Me6016 Te

JEPPIAAR ENGINEERING COLLEGE
Jeppiaar Nagar, Rajiv Gandhi Salai – 600 119
DEPARTMENT OF MECHANICAL ENGINEERING
QUESTION BANK
IV SEMESTER
ME6404 – THERMAL ENGINEERING
Regulation – 2013
JEPPIAAR ENGINEERING COLLEGE
Jeppiaar Nagar, Rajiv Gandhi Salai – 600 119
DEPARTMENT OF MECHANICAL ENGINEERING
QUESTION BANK
Subject : ME6404 – THERMAL ENGINEERING

Year / Sem : II / IV
UNIT I GAS POWER CYCLES

Otto, Diesel, Dual, Brayton cycles, Calculation of mean effective pressure, and air standard efficiency - Comparison of
cycles.
PART-A
CO Mapping : C406.1
BT
Q.No. Questions Competence PO
Level
1 Define Thermodynamic cycle BTL-1 Remembering PO1, PO6
2 Define air standard cycle. BTL-1 Remembering PO1
3 Draw the p-V & T-S diagram for Otto cycle. BTL-1 Remembering PO1, PO6
4 Draw the p-V & T-S diagram for Diesel cycle BTL-1 Remembering PO1
5 Mention the various processes of the Brayton cycle BTL-1 Remembering PO1, PO6
6 Mention the four thermodynamic processes BTL-1 Remembering PO1, PO2
involved in Diesel cycle
7 Mention the various process of Dual cyale. BTL-1 Remembering PO1, PO2
What are the assumptions made on air standard
8 BTL-1 Remembering PO1
cycles?
9 Define air standard efficiency of Diesel cycle BTL-1 Remembering PO1
10 What are the functions of a flywheel? BTL-1 Remembering PO1, PO2
11 Define compression ratio. BTL-1 Remembering PO1, PO2
12 Define cut-off ratio BTL-1 Remembering PO1, PO2
Which cycle is more efficient with respect to the Remembering
13 BTL-1 PO1
same compression ratio?
For the same compression ratio and heat supplied, Remembering
14 state the order of decreasing air standard BTL-1 PO1
efficiency of Otto, Diesel and Dual cycle.
Name the factors that affect air standard Remembering
15 BTL-1 PO1
efficiency of Diesel cycle
What is the effect of cut-off ratio on the efficiency Remembering
16 BTL-1 PO1
of diesel cycle when the compression ratio is kept
constant?
Define the term actual thermal efficiency and
17 BTL-1 Remembering PO1, PO2
relative efficiency
18 Define Mean Effective Pressure of an I.C Engine. BTL-1 Remembering PO1, PO2
19 Name the various Gas power cycles. BTL-1 Remembering PO1
20 Define air standard efficiency. BTL-1 Remembering PO1
Define specific air consumption

Define cylinder bore, stroke
23 Define clearance volume. BTL-1 Remembering PO1

Define swept volume.
What is the expression for efficiency of Otto &
Diesel cycle?
Compare Otto and Diesel cycles. Same
26 Compression Ratio And Same Heat Input: BTL-1 Analysing PO1, PO2
What is the expression for efficiency of Dual

cycle?
What is the expression for efficiency of Diesel
cycle?
29 What are all the modifications are carried out in BTL-1 Remembering PO1
Brayton cycle? Why?
What is the difference between otto and diesel
cycle?
What is meant by Atkinson cycle?
PART-B
The compression ratio for a single cylinder engine
operating on dual cycle is 9. The maximum pressure
in the cylinder is limited to 60 bar. The pressure and
temperature of the air at the beginning of the cycle
1 are 1 bar and 30OC. Heat is added during constant BTL-5 Evaluating PO1, PO2
pressure process upto 4 percent of the stroke.
Assuming cylinder diameter and stroke length as
250mm and 300mm. Determine (i) The air standard
efficiency of the cycle (ii) The power developed if the
number of working cycles is 3 per second.
The swept volume of a diesel engine working on dual
cycle is 0.0053m3 and clearance volume is
0.00035m3. The maximum pressure is 65 bar. Fuel
2 injection ends at 5 percent of the stroke. The BTL-5 Evaluating PO1, PO2, PO6
temperature and pressure at the start of the
compression are 80OC and 0.9 bar. Determine the air
standard efficiency of the cycle. Take ‫ ﻻ‬for air as 1.4.
3 In a gas turbine plant working on the Brayton cycle BTL-5 Evaluating PO1, PO2
the air at the inlet is at 27OC, 0.1 MPa. The pressure
ratio is 6.25 and the maximum temperature is 800OC,
The turbine and compressor efficiencies are each
80%. Find (i) the compressor work per kg of air (ii)
the turbine work per kg of air (iii) the heat supplied
per kg of air (iv) the cycle efficiency and (v) the
turbine exhaust temperature.
An engine with 200mm cylinder diameter and
300mm stroke works on theoretical diesel cycle. The
initial pressure and temperature of sir used are 1 bar
and 27OC. The cut-off is 8% of stroke. Determine (i)
4 Pressures and Temperatures at all salient points (ii) BTL-5 Evaluating PO1
Theoritical air standard efficiency (iii) Mean effective
pressure (iv) Power of the engine if the working
cycles per minute are 380. Assume that compression
ratio is 15 and working fluid is air.
Air enters the compressor of a gas turbine plant
operating on Brayton cycle at 1 bar and 27OC. The
5 pressure ratio in the cycle is 6. If WT =2.5 WC where BTL-5 Evaluating PO1, PO2
WT and WC are the turbine and compressor work
respectively. Calculate the maximum temperature
and the cycle efficiency.
An air standard dual cycle has a compression ratio of
10. The pressure and temperature at the beginning of
compression are 1 bar and 27OC. The maximum
pressure reached is 42 bar and the maximum
6 temperature is 1500OC. Determine (i) The BTL-5 Evaluating PO1
temperature at the end of constant volume heat
addition (ii) cut-off ratio (iii) workdone per kg of air
(iv) the cycle efficiency. Assume Cp=1.004 kJ/kg K
and Cv= 0.717 kJ/kg K for air.
The following data refers to the theoretical diesel
cycle during air as the working fluid. Pressure at the
end of the suction stroke = 1bar, Temperature at the
end of the suction stroke = 30°C, Temperature at the
7 end of the constant pressure heat addition = 1500°C, BTL-5 Evaluating PO1, PO2
Compression ratio = 16, Specific heat at constant
pressure =1.005 kJ/kgK, Specific heat at constant
volume = 0.718 kJ/kgK. Find : i) The percentage of
stroke at which cutoff place ii) Temperature at the
end of the expansion iii) The ideal thermal efficiency.
A diesel engine operating on the air-standard Diesel
cycle has six cylinders of 100 mm bore and 120 mm
stroke. The engine speed is 1800 rpm. At the
8 beginning of compression the pressure and BTL-5 Evaluating PO1
temperature of air are 1.03 bar and 35°C. If the
clearance volume is 1/8th of the stroke volume,
Calculate i) The pressure and temperature at the
salient points of the cycle, ii) The compression ratio,
iii) The efficiency of the cycle and iv) The power
output if the maximum temperature of the cycle is
1500°C. Assume Cp and Cv of air to be 1.004 kJ/kg K
and 0.717 kJ/kg K respectively.
An engine working on Otto cycle has a volume of
0.45m3, pressure 1 bar and temperature 30°C at the
beginning of compression stroke. At the end of
compression stroke, the pressure is 11 bar and 210 kJ
9 of heat is added at const ant volume. Determine i) BTL-5 Evaluating PO1
pressure, temperature and volumes at salient points in
the cycle ii) efficiency, Percentage of clearance, mean
effective pressure, ideal power developed by the
engine if the number of working cycle per minute is
210.
Derive an expression for the ideal efficiency of
Diesel cycle, using ideal air as the working fluid with
10 the aid of P-v and T-s diagrams. Sketch the Diesel BTL-2 Understanding PO1
cycle on P-V and T-S diagrams and derive the
expression for its mean effective pressure.
An air standard dual cycle has a compression ratio of
18, and compression begins at 1 bar, 40°C. The
maximum pressure is 85 bar. The heat transferred to
11 air at constant pressure is equal to that at constant BTL-5 Evaluating PO1
volume. Estimate: i) The pressure and temperatures at
the cardinal points of the cycle ii) The cycle
efficiency and iii) The mean effective pressure of the
cycle.
An an air standard dual cycle, the pressure and
temperature at the beginning of compression are 1 bar
and 57°C respectively. The heat supplied in the cycle
12 is 125 kJ/kg, two third of this being added at constant BTL-5 Evaluating PO1
volume and rest at constant pressure. If the
compression ratio is 16, determine the maximum
pressure, temperature in the cycle, thermal efficiency
and mean effective pressure.
In a gas turbine power plant, the air at inlet is at
35°C, 0.1 MPa. The pressure ratio is 8 and the
maximum temperature is 1050°C. The turbine and
compressor efficiencies are each 80%. Find
13 BTL-5 Evaluating PO1, PO2
compressor work, turbine work, heat supplied, cycle
efficiency and turbine exhaust temperature. Mass of
air may be considered 1 kg. Draw the T-s diagram.
(16 Marks)
Derive an expression for the ideal efficiency of dual
14 combustion cycle, using ideal air as the working fluid BTL-2 Understanding PO1, PO2
with the aid of P-V and T-S diagrams.
15 i) A diesel engine has a compression ratio of 20 BTL-5 Evaluating PO1
and cutoff takes place 5%of the stroke.
Find the air standard efficiency. Assume
γ=1.4. (6 Marks)
ii) In an engine working on the diesel cycle the ratios
of the weights of air and fuel supplied is 50:1, the
temperature of air at the beginning of the
compression is 333 K and the compression ratio used
is 14:1. What is the ideal efficiency of the engine?
Calorific value of the fuel used is 42000 kJ/kg.
Assume Cp=1.004 kJ/kg K and Cv =0.717 kJ/kg K
for air.
In an engine working on dual cycle, the temperature
and pressure at the beginning of the cycle are 90°C
and 1 bar respectively. The compression ratio is 9.
The minimum pressure is limited to 68 bar and the
16 BTL-5 Evaluating PO1
total heat supplied per kg of air is 1750 kJ.
Determine, i) Pressure and temperature at all salient
points ii) Cut-off ratio iii) Work-done per kg of air
and iv) net work output per kg vi) Cycle efficiency
UNIT II INTERNAL COMBUSTION ENGINES

Classification - Components and their function. Valve timing diagram and port timing
diagram - actual and theoretical p-V diagram of four stroke and two stroke engines. Simple
and complete Carburettor. MPFI, Diesel pump and injector system. Battery and Magneto
Ignition System - Principles of Combustion and knocking in SI and CI Engines. Lubrication
and Cooling systems. Performance calculation.
PART-A
CO Mapping : C406.2
BT
Level
1 What is meant by scavenging in I.C. Engines? BTL-1 Remembering PO1
Differentiate between ideal and actual valve
timing diagrams of a petrol engine.
What are the important requirements of fuel
injection system?
Mention different types of fuel injection systems
in IC Engines
What is the purpose of a thermostat in an engine
5 BTL-2 Understanding PO1, PO2
cooling system?
6 What is meant by ignition delay? BTL-1 Remembering PO1, PO2
7 What is Cetane number? BTL-1 Remembering PO1
Explain the phenomenon of detonation in S.I
Engine.
9 What are the effects of knocking? BTL-1 Remembering PO1
Define the terms: (i) Indicated Power. (ii) Brake
10 Power. (iii) Friction Power (or)Differentiate BTL-1 Remembering PO1
between Brake power and Indicated power.
Differentiate between SFC and TFC in engine
performance
12 What is meant by IC Engine? BTL-1 Remembering PO1
What is meant by highest useful compression
ratio?
Compare the thermal efficiency of petrol engines
with diesel engines. Give reasons
Which is better efficient two stroke or four stroke
engines? Why?
. What is carburetor? State some functions of
carburetor.
17 What is meant by compensation in carburetor? BTL-1 Remembering PO1
List the various circuits available in the solex
carburetor?
19 What is the fuel injector? BTL-1 Remembering PO1
20 Define governing. State functions of governing. BTL-1 Remembering PO1, PO2
List out the advantages of electronic ignition
system over the conventional systems.
What is meant by lubrication system? State the
methods of lubrication.
23 What is meant by scavenging in I.C. Engines? BTL-1 Remembering PO1
BT
Level
24 How fuels are rated? Explain. BTL-1 Remembering PO1, PO2
What is “super charging” in diesel engine? And
state its use.
What are the different factors which influence
knocking in petrol engines?
27 What are the advantages of supercharging?. BTL-1 Remembering PO1, PO6
28 What is pre – ignition? How can be detected? BTL-1 Remembering PO1, PO2
29 . List out the factors affects the ignition lag. BTL-1 Remembering
What is auto ignition and why it occurs in SI
30 BTL-1 Remembering
engine?
PART-B
Describe with suitable sketches the following system
1 of a modern carburetor. (i) main metering system (ii) BTL-2 Understanding PO1, PO2
idling system (iii) economizer system (iv)
accelerating pump system (v) choke.
(i) With a neat sketch, explain the principle of work
of diesel fuel injector
(ii) A four-stroke, four-cylinder gasoline engine has
a bore of 60mm and a stroke of 100 mm. On test
it develops a torque of 66.5 N-m when running
BTL-1 Remembering
2 at 3000rpm. If the clearance volume in each PO1
BTL-5 Evaluating
cylinder is 60cc, the relative efficiency with
respect to brake thermal efficiency is 0.5 and the
calorific value of fuel is 42MJ/kg, determine the
fuel consumption in kg/h and the brake mean
effective pressure.
(i) Explain the pressure lubrication system with a
neat sketch. BTL-2 Understanding
3 PO1
Explain the bosch fuel injector with a neat sketch
Air consumption for a four stroke petrol engine is
measured by means of a circular orifice of diameter
3.5 cm. The coefficient of discharge for the orifice is
0.6 and the pressure across the orifice is 14 cm of
water. The barometer reads 760 mm of Hg. The
temperature of air in the room is 24OC. The piston
4 displacement volume is 1800 cm3. The compression BTL-5 Evaluating PO1
ratio is 6.5. The fuel consumption is 0.13 kg/min and
calorific value is 44000kJ/kg. The brake power
developed at 2500 rpm is 28 kW. Determine (i) Air-
Fuel ratio (ii) Volumetric efficiency on the basis of
air alone (iii) Brake mean effective pressure (iv)
Relative efficiency on brake thermal efficiency
basis.
5 Discuss the difference between theoretical and BTL-2 Understanding PO1
actual valve timing diagrams of a diesel engine.
Explain the phenomena of knocking in diesel
6 engines. What are the different factors which BTL-2 Understanding PO1
influence knocking?
A four-cylinder, four-stroke oil engine 10 cm in
diameter and 15 cm in stroke develops a torque of
185 Nm at 2000 rpm. The oil consumption is 14.5
lit/hr. The specific gravity of the oil is 0.82 and
7 calorific value of oil is 42,000 kJ/kg. If the IMEP BTL-5 Evaluating PO1
taken from the indicator diagram is 6.7 bar, find (i)
mechanical efficiency (ii) brake thermal efficiency
(iii) brake mean effective pressure (iv) specific fuel
consumption in litres on brake power basis. (16
Marks)
Write a note on lubrication system for an IC engine
in detail with relevant sketches of various types.
Explain how knocking taking place in S.I. engines
9 and discuss the various factors which affect BTL-2 Understanding PO1
knocking in S.I engines
i) Compare four stroke and two stroke cycle engine
10 ii) Explain with a sketche the non-exhaust emission BTL-2 Understanding PO1
from a vehicle
i During the test of 40 minutes on a single cylinder
gas engine of 200 mm bore and 400 mm stroke,
working on the four stroke cycle, the following
readings were taken; total no of revolutions 9400,
total no of explosion 4200 and area of indicator
11 diagram 72 mm, spring number 0.8 bar/mm, brake BTL-5 Evaluating PO1
load 540 N, brake diameter 2 cm, gas used 8.5 m3,
and calorific value 15900 kJ/m3. Calculate i)
Indicated power ii) Brake power and iii) Indicated
and brake thermal efficiency. ii) Write short notes on
SI and CI engine emissions
UNIT III STEAM NOZZLES AND TURBINES
Flow of steam through nozzles, shapes of nozzles, effect of friction, critical pressure ratio,
supersaturated flow. Impulse and Reaction principles, compounding, velocity diagram for
simple and multi-stage turbines, speed regulations –Governors.
PART-A
CO Mapping : C406.3
BT
Level
What are the main classifications of steam
turbine?
What is meant by carry over loss?
State the function of fixed blades.
State the function of moving blades.
Differentiate between impulse and reaction
turbines
Give examples of impulse turbine and reaction
6 turbine? BTL-1 Remembering PO1, PO6, PO7
What is meant by degree of reaction?

What are the three methods compounding?
9 What is hypothetical indicator diagram? BTL-1 Remembering PO1, PO6, PO7
10 Explain pressure compounding BTL-1 Remembering PO1, PO6, PO7

Define diagram factor.
11 BTL-1 Remembering PO1, PO6, PO7
Briefly explain the working of steam turbine.
Define pure substance.
14 Give the classification of steam turbine. BTL-1 Remembering PO1
Give the classification of steam turbines according
15 BTL-4 Analyzing PO1
to number of stages
16 Define impulse turbine. BTL-1 Remembering PO1
17 Define reaction turbine BTL-1 Remembering PO1
18 Define compounding of steam turbines BTL-1 Remembering PO1
19 Define velocity diagram. BTL-1 Remembering PO1
Define speed ratio.
21 Define degree of Reaction (Rd). BTL-1 Remembering PO1
What are the assumptions required to derive
22 maximum efficiency? BTL-1 Remembering PO1
What are the classifications of steam turbine on

23 the basis of method of steam expansion? BTL-1 Remembering PO1, PO6

24 the basis of number of blades? BTL-1 Remembering PO1

25 the basis of steam flow direction? BTL-1 Remembering

26 the basis of pressure of steam? BTL-1 Remembering
What are the external loses in turbine?

What are the internal loses in turbine?
What are the main constructional features of a
29 turbine? BTL-1 Remembering PO1
30 What is supersaturated flow? BTL-1 Remembering PO1

PART-B
i)Define critical pressure ratio of a nozzle and
discuss why attainment of sonic velocity
determines the maximum discharge through steam
1 BTL-6 Creating PO1, PO6, PO7
nozzle. (10 Marks)
ii)Explain the metastable expansion of steam in a
nozzle with help of h-s diagram. (6 Marks)
2 A simple impulse turbine has one ring of moving BTL-5 Evaluating PO1, PO6, PO7
blades running at 150 m/sec. The absolute velocity of
steam at exit from the stage is 85 m/sec at angle of
80O from the tangential direction. Blade velocity co-
efficient is 0.82 and the rate of steam flowing
through the stage is 2.5 kg/sec. If the blades are
equiangular, determine (i) Blade angles (ii) Nozzle
angle (iii) Absolute velocity of steam issuing from
the nozzle (iv) Axial thrust.
A convergent divergent nozzle required to discharge
2 kg of steam per second. The nozzle is supplied with
steam at 7 bar and 180OC and discharge takes place
against a back pressure of 1 bar. The expansion up to
throat is isentropic and the frictional resistance
between the throat and the exit is equivalent to 63
3 BTL-5 Evaluating PO1, PO6, PO7
kJ/kg of steam. Take approach velocity of 75 m/s and
throat pressure 4 bar. Estimate (i) suitable areas for
the throat and the exit (ii) overall efficiency of the
nozzle based on the enthalpy drop between the actual
inlet pressure and the temperature and the exit
pressure
In a stage of impulse reaction turbine operating with
50% degree of reaction, the blades are identical in
shape. The outlet angle of the moving blade is 19O
and the absolute discharge velocity of steam is
100m/s in the direction 70O to the bottom of the
blades. If the rate of flow through the turbine is
15000 kg/hr, calculate the power developed by the
turbine.
Dry saturated steam at a pressure of 11 bar enters a
convergent divergent nozzle and leaves at a pressure
5 of 2 bar. If the flow is adiabatic and frictionless, BTL-5 Evaluating PO1, PO2, PO6
determine (i) the exit velocity of steam (ii) ratio of
cross section of exit and that at throat.
In a De Laval turbine steam issues from the nozzle
with a velocity of 1200 m/s. The nozzle angle is 20O,
the mean blade velocity is 400 m/s and the inlet and
outlet angles of blades are equal. The mass of steam
PO1, PO2, PO6,
6 flowing through the turbine per hour is 1000kg. BTL-5 Evaluating
PO7
Calculate (i) blade angles (ii) relative velocity of
steam entering the blades (iii) Tangential force on
blades (iv) power developed (v) blade efficiency.
Take blade velocity co-efficient as 0.8.
Dry saturated steam at a pressure of 8 bar enters a
convergent-divergent nozzle and leaves it at a
pressure of 1.5 bar. If the flow is isentropic, and the
corresponding expansion index is 1.133; find the
ratio of cross-sectional area at exit and throat for
maximum discharge.
8 The steam at 4.9 bar and 160OC is supplied to a BTL-5 Evaluating PO1
single stage impulse turbine at a mass flow rate of 30
kg/min, from where it is exhausted to a condenser at
a pressure of 19.6 kPa. The blade speed is 300 m/s.
The nozzles are inclined are inclined as 25O to the
plane of wheel and the outlet blade angle is 35O.
Neglecting friction losses, determine (i) theoretical
power developed by the turbine (ii) diagram
efficiency and (iii) stage efficiency.
Steam enters a convergent divergent nozzle at 2 MPa
and 400°C with a negligible velocity and a mass flow
rate of 2.5 kg/s and it exits at a pressure of 300 kPa.
The flow is isentropic between the nozzle entrance
and throat and overall nozzle efficiency is 93 %.
Determine i) throat area and ii) exit area
A gas expands in a convergent divergent nozzle
from 5 bar to 1.5 bar, the initial temperature being
700°C and the nozzle efficiency is 90%. All the
10 BTL-5 Evaluating PO1, PO2
losses take place after the throat. For 1 kg/s mass
flow rate of the gas, find throat and exit areas. Take
n=1.4, R=287 J/kgK
UNIT IV AIR COMPRESSOR

Classification and working principle of various types of compressors, work of compression with and without
clearance, Volumetric efficiency, Isothermal efficiency and Isentropic efficiency of reciprocating compressors,
Multistage air compressor and inter cooling –work of multistage air compressor.
PART-A
CO Mapping : C803.4
BT
Level
List out the components of reciprocating air
compressor.
2 List out the types of air compressors. BTL-1 Remembering PO1, PO2
3 Define single acting compressor. BTL-1 Remembering PO1
4 Define double acting compressor. BTL-1 Remembering PO1
5 Define single stage compressor? BTL-1 Remembering PO1
6 Define multistage compressor? BTL-1 Remembering PO1
7 Define ratio of compression. BTL-1 Remembering PO1
8 Define free air delivered (FAD? BTL-1 Remembering PO1
9 Define displacement of the compressor. BTL-1 Remembering PO1
10 Define actual capacity of the compressor. BTL-1 Remembering PO1
11 List out the parts of a centrifugal compressor. BTL-1 Remembering PO1
Distinguish between rotary and reciprocating
compressor.
13 Define volumetric efficiency. BTL-1 Remembering PO1
14 Define clearance ratio? BTL-1 Remembering PO1, PO2
15 Define Isothermal Efficiency of air compressor. BTL-1 Remembering PO1
16 Define isentropic efficiency. BTL-1 Remembering PO1
Explain how flow of air is controlled in a
reciprocating compressor.
Mention the important applications of compressed
air?
What factors limit the delivery pressure in a
reciprocating compressor
Why clearance is necessary and what is its effect on
the performance of reciprocating compressor.
21 . Define mean effective pressure. BTL-1 Remembering PO1
Name the methods adopted for increasing isothermal
22 efficiency of reciprocating air BTL-1 Remembering PO1
compressor.
Which type of compression is the best in
reciprocating compressor?
What are the factors that affect the volumetric
24 efficiency of a reciprocating BTL-1 Remembering PO1
compressor?
Discuss the effect of clearance upon the performance
25 of an air compressor? BTL-1 Remembering PO1, PO2
PART-B
A two-stage air compressor consists of three
cylinders having the same bore and stroke. The
delivery pressure is 7 bar and the free air delivery is
4.3 m3/min. Air is drawn in at 1.013 bar , and 15OC
1 and an intercooler cools the air to 38OC. The index of BTL-5 Evaluating PO1
compression is 1.3 for all three cylinders. Neglecting
clearance calculate, (i) the intermediate pressure (ii)
the power required to drive the compressor (iii) the
isothermal efficiency
With a neat sketch, describe the construction and
working of a single stage acting reciprocating air
2 compressor. Also derive the equation for work done BTL-2 Understanding PO1
with clearance and without clearance.
The FAD (free air delivered) of a single cylinder

single stage air compressor is 2.5 m3/min. The
ambient is at 20C and 1.013 bar and delivery
pressure is 7 bar. The clearance volume is 5% of the
stroke volume and law of compression and expansion
is PV1.25=C. Stroke length is 20% more than that of
the bore.Compressor runs at 150 rpm. Determine the
mass of air per second, indicated power, indicated
mean effective pressure and bore and stroke of the
cylinder.
Explain the construction and working principle of
4 centrifugal compressor and axial flow compressor BTL-2 Understanding PO1
with neat sketches.
A single acting, single stage air compressor delivers
0.6 kg of air per minute at 6 bar. The temperature and
pressure at the end of suction stroke are 30OC and 1
bar. The bore and stroke of the compressor are 100
mm and 150 mm respectively. The clearance is 3%
of swept volume. Assuming the index of
compression and expansion to be 1.3. Find (i)
volumetric efficiency of the compressor (ii) power
required if the mechanical efficiency is 85% and (iii)
speed of compressor (rpm).
In a single acting two stage reciprocating air
compressor 4.5 kg of air per min. are compressed
from 1.013 bar and 15OC through a pressure ratio of
9 to 1. Both stage have the same pressure ratio, and
the law of compression and expansion in both stages
is pV1.3=C. Calculate (i) the indicated power (ii) the
cylinder swept volume required. Assume that the
clearance volume of both stages are 5% of their
respective swept volumes and that the compressor
runs at 300 rpm.
A single acting air compressor takes in atmospheric
air (atm condition 101.325 kPa, 27OC) and delivers it
at 1.4 MPa. The compressor runs at 300 rpm and has
cylinder diameter of 160 mm and stroke 200 mm.
Clearence volume is 5% of stroke volume. If the
7 pressure and temperature of air at the end of suction BTL-5 Evaluating PO1
stroke are 100kPa and 47OC, and law of compression
and expansion is pV1.2=C, determine (i) mass of the
sir delivered per minute (ii) volumetric efficiency
(iii) driving power required, if mechanical efficiency
is 85%.
A three stage air compressor with perfect
intercooling takes 15 m3 of air per minute at 95 kPa
and 27OC, delivers the air at 3.5 MPa. If compression
process is polytropic (pV1.3=C), determine (i) Power
required if mechanical efficiency is 90% (ii) heat
rejected in the intercoolers per minute (iii) isothermal
efficiency (iv) heat rejected through cylinder walls
per minute.
Derive an expression for the minimum work
required for a two stage reciprocating air
9 compressor with perfect inter-cooling and prove that BTL-2 Understanding PO1
the intercooler pressure is the geometric mean of the
initial and final pressure.
Write working principle of multi-stage reciprocating
air compressor. Derive the condition for minimum
work output of two stage reciprocating air
compressor and work output relation for multi stage
reciprocating air compressor.
A single –acting two stage air compressor deals with
4 m3/min of air at 1.013 bar and 15° C with a speed
of 250 rpm. The delivery pressure is 80 bar.
Assuming, complete inter-cooling. Find the
maximum power required by the compressor and the
bore and stroke of the compressor. Assume a piston
speed of 3 m/s, mechanical efficiency of 75% and
volumetric efficiency of 80% per stage. Assume the
polytropic index of compression in both the stage to
be n=1.25 and neglect clearance.
A single stage single acting reciprocating air
compressor has a bore of 20 cm and a stroke of 30
cm. The compressor runs at 600 rpm. The clearance
volume is 4% of the swept volume and index if
expansion and compression is 1.3. The suction
conditions are 0.97 bar and 27°C and delivery
pressure is 5.6 bar. The atmospheric conditions are at
1.01 bar and 17°C. Determine i) the free air delivered
in m3/min ii) the volumetric efficiency referred to the
free air conditions iii) the indicated power.
i) A single stage single acting compressor delivers 15
m3 of free air per minute from 1 bar to 8 bar. The
speed of the compressor is 300 rpm. Assuming that
compression and expansion follows the law PV1.3 =
Constant and clearance is 1/16th of swept volume,
13 find the diameter and stroke of the compressor. Take BTL-5 Evaluating PO1
L/D = 1.5. The temperature and pressure of air at the
suction are same as atmospheric air. ii) For the same
pressure ratio, discuss the advantages of multistage
compression with inter cooling over single stage
compression.
Explain with neat sketch the construction and
14 working of Roots blower with two lobe and three BTL-1 Remembering PO1
lobe rotor and vane type compressor.
2 kg/s of air enter the L.P cylinder of a two stage,
reciprocating air compressor. The overall pressure
ratio is 9. The air at inlet to the compressor is at 100
kPa and 35°C. The index of compression in each
cylinder is 1.3. Find the inter-cooler pressure for
perfect inter-cooling Also find the minimum power
required for compression. Take R=0.287 kJ/kgK and
Cp=1 kJ/kg K.
UNIT V REFRIGERATION AND AIR CONDITIONING
Refrigerants - Vapour compression refrigeration cycle- super heat, sub cooling – Performance calculations -
working principle of vapour absorption system, Ammonia –Water, Lithium bromide – water systems (Description
only) . Air conditioning system - Processes, Types and Working Principles. - Concept of RSHF, GSHF, ESHF-
Cooling Load calculations.
PART-A
CO Mapping : C803.5
BT
Level
1 Define C.O.P. of a refrigeration system. BTL-1 Remembering PO1, PO5
2 Define refrigerator. BTL-1 Remembering PO1
3 Define heat pump. BTL-1 Remembering PO1, PO5
4 Define DPT and Degree of saturation. BTL-1 Remembering PO1
Define Relative humidity (RH) and Specific
humidity.
What are the classifications of air conditioning
system?
7 How does humidity affect human comfort? BTL-1 Remembering PO1, PO5
8 Define: RSHF, RTH. BTL-1 Remembering PO1
What are the various sources of heat gain of an air
conditioned space?
10 Define apparatus dew point (ADP) of cooling coil BTL-1 Remembering PO1
11 Define bypass factor (BPF) of a coil. BTL-1 Remembering PO1
12 What is psychrometry ? BTL-1 Remembering PO1
13 Define DPT and Degree of saturation. BTL-1 Remembering PO1
Define Relative humidity (RH) and Specific
humidity.
15 How does humidity affect human comfort? BTL-1 Remembering PO1, PO5
What are the various sources of heat gain of an air
conditioned space?
State the effects of very high and a very low bypass
factor.
18 What factors affect BPF? BTL-1 Remembering PO1, PO5
What are the requirements of comfort air
conditioning?
20 Define Effective Temperature (ET). BTL-1 Remembering PO1
What are the general comfort conditions during
summer and winter?
22 Differentiate between heat pump and refrigerator. BTL-1 Remembering PO1
23 What is dew point temperature? BTL-1 Remembering PO1, PO5
24 What is effective temperature? BTL-1 Remembering PO1
25 Define dew point depression. BTL-1 Remembering PO1
26 Define Dew point,Tdp BTL-1 Remembering PO1
27 What is meant by Absolute humidity? BTL-1 Remembering PO1
What is Humidity Ratio?
PART-B
Describe the following refrigeration systems with
1 layout (i) Ammonia water system (ii) Lithium- BTL-2 Understanding PO1
bromide water system.
(i) Describe the working principle of centralized
air conditioning system and enumerate the
2 need for it. BTL-2 Understanding PO1
(ii) List the loads that contribute to the overall
cooling load.
A food storage locker requires a refrigeration
capacity of 50 kW. It works between a condenser
temperature of 35OC and an evaporator temperature
of -10OC. The refrigerant is ammonia. It is sub-
cooled by 5OC before entering the expansion valve
by the dry saturated vapour leaving the evaporator.
Assuming a single cylinder, single acting compressor
operating at 1000 rpm with stroke equal to 1.2 times
the bore. Determine (i) the power required (ii) the
cylinder dimensions.
(i) Explain the centralized air conditioning system
with a neat sketch
100 m3 of air per minute at 15OC DBT 80% RH is
heated until its temperature is 22OC. Calculate heat
added to air per minute, RH of the heated air and wet
bulb temperature of the heated air.
An ammonia refrigerator operates between
evaporating and condensing temperatures of -16OC
and 50OC respectively. The vapour is dry saturated
at the compressor inlet, the compression process is
isentropic and there is no undercooling of the
condensate. Calculate (i) The refrigerator effect per
kg (ii) The mass flow and power input per kw of
refrigeration and (iii) COP.
. Saturated air leaving the cooling section of an air
conditioning system at 14OC at a rate of 50 m3/min is
mixed adiabatically with the outside air at 32OC and
60% relative humidity at a rate of 20 m3/min.
assuming that the mixing process occurs at a pressure
of 1 atm, determine the specific humidity, the relative
humidity, the dry-bulb temperature and the volume
flow rate of the mixture.
An air conditioning plant is required to supply 50 m3
of air per minute at a DBT of 22OC and 50% RH.
The atmospheric condition is 32OC with 65% RH.
Determine the mass os moisture removed and
capacity og cooling coil, if the required effect is
obtained by dehumidification and sensible cooling
process. Also calculate sensible heat factor.
i) Explain the construction and working of vapour
absorption refrigeration system with neat sketch. ii)
8 Write the advantages and disadvantages of vapour BTL-2 Understanding PO1
absorption and vapour compression refrigeration
system.
i) Explain the working principle of vapour absorption
refrigeration system and compare it with vapour
compression refrigeration system. ii) A Freon vapour
compression system operating at a condenser
temperature of 40°C and an evaporator temperature
of -5°C develops 15 tons of refrigeration. Using the
9 p-h diagram for Freon 12, determine i) The mass BTL-5 Evaluating PO1
flow rate of the refrigerant circulated. ii) the
theoretical piston displacement of the compressor
and piston displacement per ton of refrigeration. ii)
The theoretical horse power of the compressor and
horse power per ton of refrigeration iv) The heat
rejected in the condenser.
i) Compare vapour compression and vapour
absorption refrigeration system. ii) For a hall to be
air-conditioned the following conditions are given:
Outdoor condition 40°C DBT,20°C WBT, Required
comfort condition 20°C DBT,60% RH, Seating
10 capacity of hall-1500, Amount of outdoor air supply BTL-5 Evaluating PO1, PO5
0.3 m3/min per person, if the required condition is
achieved first by adiabatic humidification and then
by cooling, estimate a) the capacity of the cooling
coli in tones and ii) The capacity of humidifier in
kg/hr.
UNIT I GAS POWER CYCLES

Otto, Diesel, Dual, Brayton cycles, Calculation of mean effective pressure, and air standard efficiency - Comparison of cycles.
PART-A
1. Define Thermodynamic cycle. (OCT’ 97)
Thermodynamic cycle is defined as the series of operations which takes place in a certain order and restore
the initial conditions.
2. Define air standard cycle. ( May’14, Dec’12, May’11)
The theoretical cycle or air cycle approximation which is used to calculate conditions in an internal
combustion engines is known as air standard cycle.
3. Draw the p-V & T-S diagram for Otto cycle. (APR’04)
1-2 Isentropic compression

2-3 Constant Volume Heating
3-4 Isentropic Expansion
4-1 Constant Volume Cooling
4. Draw the p-V & T-S diagram for Diesel cycle. (MAY’07)
1-2 Isentropic compression

2-3 Constant pressure Heating
3-4 Isentropic expansion
4-1 Constant volume Cooling
5. Mention the various processes of the Brayton cycle. (OCT’96)

1. Isentropic compression
2. Constant pressure heat supplied
3. Isentropic expansion
4. Constant pressure heat rejection.
6. Mention the four thermodynamic processes involved in Diesel cycle. ( APR’08)

1. One reversible adiabatic compression
2. One constant pressure process
3. One reversible adiabatic expansion
4. One constant volume
7. Mention the various process of Dual cyale. (APR’96)

1. Isentropic compression
2. Constant volume heat addition
3. Isentropic expansion
4. Constant volume heat rejection
8. What are the assumptions made on air standard cycles? (MAY’16, NOV’16, MAY’15, MAY’13, May’11,
JUNE’09)
The assumptions made are,
(i) Air is the working fluid, assumed to be a perfect gas.
(ii) Effect of colorific values of fuels is neglected by using hot and cold body contacts with the engine cylinder
head for addition and rejection of heat respectively.
(iii)Frictionless.
(iv) No heat is either gained or lost during the cycle except during the contact of hot body and cold body with
the cylinder head.
9. Define air standard efficiency of Diesel cycle. (DEC’08)
Air standard efficiency is defined as the ratio of work done by the cycle to the heat supplied to the cycle.
10. What are the functions of a flywheel? (MAY’15)
Flywheel serves as an energy reservoir. It stores energy during power stroke and releases energy during
remaining strokes.
11. Define compression ratio. (NOV’10, MAY’14)
Compression ratio is defined as the ratio of volume fluid occupied when the piston reaches bottom dead
centre position to the volume of fluid occupied when the piston reaches the top dead centre position.
V
‘ R 1  S
C V
C
12. Define cut-off ratio. (MAY’14)
Cut-off ratio is defined as the ratio of volume after the heat addition to the volume before the heat addition.
13. Which cycle is more efficient with respect to the same compression ratio? (OCT’95)
For the same compression ratio, Otto cycle is more efficient than Diesel cycle.
14. For the same compression ratio and heat supplied, state the order of decreasing air standard efficiency
of Otto, Diesel and Dual cycle. (APR’98, OCT’98)
ɳotto > ɳDual > ɳDiesel
15. Name the factors that affect air standard efficiency of Diesel cycle. (APR’97)
Compression ratio and cut-off ratio
16. What is the effect of cut-off ratio on the efficiency of diesel cycle when the compression ratio is kept
constant? (NOV’15, APR’03)
When the cut-off ratio of diesel cycle increases, the efficiency of cycle is decreased when the compression
ratio kept constant and vice versa.
17. Define the term actual thermal efficiency and relative efficiency. (DEC’12)
Actual efficiency is defined as the ratio of work output by the cycle to the heat input to the cycle.
Relative efficiency is defined as the ratio between actual efficiency and air standard efficiency.
18. Define Mean Effective Pressure of an I.C Engine. (MAY’16, NOV’07)
Mean effective pressure is defined as the constant pressure acting on the piston during the working stroke. It
is also defined as the ratio of work done to the stroke volume or piston displacement volume.
19. Name the various Gas power cycles.

1. Carnot cycle 2.Otto cycle 3.Diesel cycle
4. Brayton cycle 5.Dual combustion cycle 6.Atkinson cycle.
20. Define air standard efficiency.
It is defined as the ratio of net work transfer during the cycle to the net heat transfer to the cycle. It is also
known as thermal efficiency.
Q  Qr
  s
a Q
s
21. Define specific air consumption.
Specific air consumption is the quantity of working substance required for doing unit work transfer.
22. Define cylinder bore, stroke.
Bore: the cylinder diameter is known as cylinder bore.
Stroke: the distance through which the piston can travel between top dead center position and bottom dead
centre is known as stroke.
23. Define clearance volume.

Clearance volume is defined as the volume occupied by the fluid when the piston reaches top dead centre. It
is denoted by Vc
24. Define swept volume.
It is defined as the volume swept by the piston. When it moves between top dead centre and bottom dead
centre. It is denoted by Vs
25. What is the expression for efficiency of Otto & Diesel cycle?
For Otto cycle,
 1  V
Efficiency, cy  1    1  where r  1  compression ratio
  r   V2
For Diesel cycle,
  rc  1 
Efficiency, cy  1   1  , where rc=Cut-off ratio
  r  rc  1 
26. Compare Otto and Diesel cycles.

Same Compression Ratio And Same Heat Input:
D  O Same
V1
Compression ratio =C
V2
i.e., For same T1 ,T2 should be same for both the cycles.
Heat input is same
mCv(T3- T2) = mCv (T3' - T2 )
we know that Cp > Cv
(T3’- T2) < (T3- T2)
o  1 
T4  T1 
T3  T2 
o  1
T  T 
4
'
1
 T  T 
3
'
2
27. What is the expression for efficiency of Dual cycle?

  rc rp  1 
  
cy  1   1  Where r = Compression Ratio


r  
 rp  1   rp  rc  1 
rc =Cut-off ratio
rp= Pressure ratio
28. What is the expression for efficiency of Diesel cycle?

 
 1 
η = 1   1 
Where rp=Pressure ratio
 r   
 p 
29. What are all the modifications are carried out in Brayton cycle? Why? (APR/MAY 2015)
In Brayton cycles, the devices can be incorporated to increase its thermal efficiency such as (i) Regenerator
(ii) Re heater and (iii) Intercooler, because of increasing thermal efficiency of the cycle.
30. What is the difference between otto and diesel cycle? (NOV’16, NOV’15)
Otto cycle Diesel cycle

1. Otto cycle consist of two 1. It consists of two adiabatic one
adiabatic and two constant constant volume and one constant
volume process. pressure process.
2. Compression ratio is equal to 2. Compression ratio is greater than
expansion ratio expansion ratio
3. Heat addition takes place at 3. Heat addition takes place at
constant volume constant pressure.
4. Compression ratio is less. It is 4. Compression ratio is more. It
varies from 6 to 8. varies from 12 to 18.
PART-B
1. The compression ratio for a single cylinder engine operating on dual cycle is 9. The maximum pressure in
the cylinder is limited to 60 bar. The pressure and temperature of the air at the beginning of the cycle are 1
bar and 30OC. Heat is added during constant pressure process upto 4 percent of the stroke. Assuming
cylinder diameter and stroke length as 250mm and 300mm. Determine (i) The air standard efficiency of the
cycle (ii) The power developed if the number of working cycles is 3 per second.(May/June 2016)
Refer: ͞Kothandaraman.C.P., Domkundwar. S,Domkundwar. A.V., “A course in thermal Engineering", Fifth Edition, ” by
Dhanpat Rai & sons , 2002
2. The swept volume of a diesel engine working on dual cycle is 0.0053m3 and clearance volume is 0.00035m3.
The maximum pressure is 65 bar. Fuel injection ends at 5 percent of the stroke. The temperature and
pressure at the start of the compression are 80OC and 0.9 bar. Determine the air standard efficiency of the
cycle. Take ‫ ﻻ‬for air as 1.4. (MAY/JUNE 2016)
Refer: “Kothandaraman.C.P., Domkundwar. S,Domkundwar. A.V., “A course in thermal Engineering", Fifth Edition, ” by Dhanpat Rai
& sons , 2002
3.In a gas turbine plant working on the Brayton cycle the air at the inlet is at 27 OC, 0.1 MPa. The pressure
ratio is 6.25 and the maximum temperature is 800OC, The turbine and compressor efficiencies are each 80%.
Find (i) the compressor work per kg of air (ii) the turbine work per kg of air (iii) the heat supplied per kg of
air (iv) the cycle efficiency and (v) the turbine exhaust temperature.(NOV/DEC 2016)
Refer: ͞Kothandaraman.C.P., Domkundwar. S,Domkundwar. A.V., “A course in thermal Engineering", Fifth Edition, ” by
Dhanpat Rai & sons , 2002
4. Air enters the compressor of a gas turbine plant operating on Brayton cycle at 1 bar and 27OC. The
pressure ratio in the cycle is 6. If WT =2.5 WC where WT and WC are the turbine and compressor work
respectively. Calculate the maximum temperature and the cycle efficiency (APRIL/MAY 2015)
& sons , 2002
5.An air standard dual cycle has a compression ratio of 10. The pressure and temperature at the beginning of
compression are 1 bar and 27OC. The maximum pressure reached is 42 bar and the maximum temperature
is 1500OC. Determine (i) The temperature at the end of constant volume heat addition (ii) cut-off ratio (iii)
workdone per kg of air (iv) the cycle efficiency. Assume Cp=1.004 kJ/kg K and Cv= 0.717 kJ/kg K for air.
(NOV/ DEC 2015)
& sons , 2002
6. The following data refers to the theoretical diesel cycle during air as the working fluid. Pressure at the end
of the suction stroke = 1bar, Temperature at the end of the suction stroke = 30°C, Temperature at the end of
the constant pressure heat addition = 1500°C, Compression ratio = 16, Specific heat at constant pressure
=1.005 kJ/kgK, Specific heat at constant volume = 0.718 kJ/kgK. Find : i) The percentage of stroke at which
cutoff place ii) Temperature at the end of the expansion iii) The ideal thermal efficiency. (Nov-Dec 2010)
& sons , 2002 ”
7.A diesel engine operating on the air-standard Diesel cycle has six cylinders of 100 mm bore and 120 mm
stroke. The engine speed is 1800 rpm. At the beginning of compression the pressure and temperature of air
are 1.03 bar and 35°C. If the clearance volume is 1/8th of the stroke volume, Calculate i) The pressure and
temperature at the salient points of the cycle, ii) The compression ratio, iii) The efficiency of the cycle and iv)
The power output if the maximum temperature of the cycle is 1500°C. Assume Cp and Cv of air to be 1.004
kJ/kg K and 0.717 kJ/kg K respectively. (Nov/Dec 2011)
& sons , 2002 ”
8.An engine working on Otto cycle has a volume of 0.45m3, pressure 1 bar and temperature 30°C at the
beginning of compression stroke. At the end of compression stroke, the pressure is 11 bar and 210 kJ of heat
is added at const ant volume. Determine i) pressure, temperature and volumes at salient points in the cycle ii)
efficiency, Percentage of clearance, mean effective pressure, ideal power developed by the engine if the
number of working cycle per minute is 210. (May/June 2007 May/June 2011)
& sons , 2002 ”
9. Derive an expression for the ideal efficiency of Diesel cycle, using ideal air as the working fluid with the aid
of P-v and T-s diagrams. Sketch the Diesel cycle on P-V and T-S diagrams and derive the expression for its
mean effective pressure. (Nov/Dec 2008 Nov/Dec 2011)
& sons , 2002 ”
10. An air standard dual cycle has a compression ratio of 18, and compression begins at 1 bar, 40°C. The
maximum pressure is 85 bar. The heat transferred to air at constant pressure is equal to that at constant
volume. Estimate: i) The pressure and temperatures at the cardinal points of the cycle ii) The cycle efficiency
and iii) The mean effective pressure of the cycle. (Nov-Dec 2012)
& sons , 2002 ”
UNIT II INTERNAL COMBUSTION ENGINE

Classification - Components and their function. Valve timing diagram and port
timing diagram - actual and theoretical p-V diagram of four stroke and two stroke
engines. Simple and complete Carburettor. MPFI, Diesel pump and injector system.
Battery and Magneto Ignition System - Principles of Combustion and knocking in SI
and CI Engines. Lubrication and Cooling systems. Performance calculation.
PART-A
1. What is meant by scavenging in I.C. Engines? (MAY’13, NOV’10, APR’03)
The process of removing burnt exhaust gases from the combustion chamber of the engine cylinder using
the fresh incoming charge is known as scavenging.
2. Differentiate between ideal and actual valve timing diagrams of a petrol engine. (OCT’01)
Theoretical valve timing diagram:
In theoretical valve timing diagram, inlet and exhaust valves open and close at both at dead centers.
Similarly, all the process sharply completed at the TDC or BDC.
Actual valve timing diagram:
The inlet valve opens 10-30o before the TDC. The air fuel mixture is sucked into the cylinder till the inlet
valve closes.
The inlet valve closes 30-40o or even 60o after BDC. The charge is compressed till the spark occurs.
The spark is produced 20-40o before the TDC. This gives sufficient time for fuel to burn. The pressure
and temperature increase. The burnt gases expand till the exhaust valve opens.
The Exhaust valve opens 30-60o before the BDC. The exhaust gases are forced out from the cylinder till
the exhaust valve closes.
The exhaust valve closes 8-20o after the TDC. Before it closes, again the inlet valve opens 10-30o before
TDC.
3. What are the important requirements of fuel injection system? (NOV’15, NOV’07)
 The beginning as well as end of injection should take place sharply.
 Inject the fuel at correct time in the cycle throughout the speed range of the engine.
 The injection of fuel should occur at the correct rate and in correct quantity as required by the
varying engine load.
 Atomize the fuel to the required degree
 Distribute the fuel throughout the combustion chamber for better mixing.
4. Mention different types of fuel injection systems in IC Engines. (APR’99)
a. Air injection systems
b. Airless injection system
1. Common rail system
2. Individual pump system
5. What is the purpose of a thermostat in an engine cooling system? (NOV’15, APR’03)
A Thermostat valve is used in the water cooling system to regulate the circulation of water in system to
maintain the normal working temperature of the engine parts during the different operating conditions.
6. What is meant by ignition delay? (NOV’03)
In the actual engine cylinder, there is a certain time interval between the instant of spark and the instant
of pressure rise due to combustion. This time interval or time lay is known as “Ignition Lag” or “Ignition
Delay” or “Delay Period”.
7. What is Cetane number? (APR’03)
The property that quantities the ignition delay is called cetane number.
8. Explain the phenomenon of detonation in S.I Engine. (MAY’16, NOV’10)
If the temperature of the un burnt mixture exceeds the self ignition temperature during the ignition delay
period, auto ignition occurs at various locations in the cylinder. This will generate pressure pulses. These
high pressure pulses can cause damage to the engine and quite often are in the audible frequency range. This
phenomenon is often called knocking or detonation.
9. What are the effects of knocking? (MAY’07)
The Impact on the engine components and structures may cause failures and creates undesirable noise
which is always objectionable.
The lack of control of combustion process leads to pre ignition and local overheating. Therefore piston
may be damaged by overheating.
The pressure differences in the combustion chamber cause the gas to vibrate and scrub the chamber walls
causing increased loss of heat to the coolant.
Detonation results in increased carbon deposits on the wall of the cylinder.
Due to increase in the rate of heat transfer, the power outputs as well as efficiency of the engine will
decreases.
10. Define the terms: (i) Indicated Power. (ii) Brake Power. (iii) Friction Power (or) Differentiate
between Brake power and Indicated power. (APR’03)
(i) Indicated power is defined as the power actually developed by the engine in the engine cylinder.
(ii) Brake power is defined as the power available at the crankshaft. It is always less than the
indicated power.
(iii) Friction power is the difference between indicated power and the brake power. Actually friction
power is the power lost due to engine friction.
i.e FP = IP – BP
11. Differentiate between SFC and TFC in engine performance. (NOV’03)
SFC is defined as the amount of fuel consumed of fuel consumed per brake power hour of work.
12. What is meant by IC Engine?
The internal combustion engine (IC Engine) is a heat engine that converts chemical energy in a fuel into
mechanical energy. Chemical energy of a fuel is first converted into thermal energy by means of energy of a
fuel is first converted into thermal energy by means of combustion or oxidation with air inside the engine.
This thermal energy is converted into useful work through mechanical mechanism of the engine.
13. What is meant by highest useful compression ratio?
The compression ratio which gives maximum efficiency is known as highest useful compression ratio.
14. Compare the thermal efficiency of petrol engines with diesel engines. Give reasons.
Thermal efficiency of diesel engine is greater than petrol engine. This is due to high compression ratio.
15. Which is better efficient two stroke or four stroke engines? Why?
Two stroke engine gives always lesser efficiency than four stroke engine due to incomplete combustion
and poor scavenging.
16. What is carburetor? State some functions of carburetor.
A carburetor is a device which vaporizes the fuel and mixed it with the air.
a. It maintains a small reserve of petrol in the float chamber at a constant head.
b. It atomizes and vaporizes the fuel.
c. It prepares a mixture of petrol and air in correct proportion.
d. It supplies a fine spray of petrol.
17. What is meant by compensation in carburetor?
The process of providing additional air or fuel when it requires maintaining the correct air fuel mixture is
called compensation in carburetor.
18. List the various circuits available in the solex carburetor?
a. Starting circuits.
b. Normal running circuits
c. Acceleration circuit
d. Idling circuit and slow running circuit.
19. What is the fuel injector?

Fuel injector is used in diesel engine to inject and atomize the diesel at the compression stroke into the
combustion chamber.
20. Define governing. State functions of governing.
Governing is the process of varying the fuel supply. It is done to maintain constant speed through the
load is changed.
21. List out the advantages of electronic ignition system over the conventional systems. (NOV’03)
The parts such as reluctor, magnetic pick up and electronic control module are not subjected to wear and
tear as a mechanical contact breaker.
a. Periodic adjustment of engine timing is not necessary.
b. It gives very accurate control of timing.
22. What is meant by lubrication system? State the methods of lubrication.
The process of reducing the friction between moving parts is known lubrication.
 Petrol lubrication or mist lubrication system
 Wet sump and
 Dry sump
23. What is meant by scavenging in I.C. Engines?
The process of removing burnt exhaust gases from the combustion chamber of the engine cylinder using
the fresh incoming charge is known as scavenging.
24. How fuels are rated? Explain.

The rating of a SI engine fuel is done by comparing its performance with that of a standard reference fuel
which is usually a combination of iso – octane and n-heptane called octane number.
The rating of a SI engine fuel is established by compounding the test fuel to two standard reference fuels.
The fuel component n-cetane number value of 100, while alpha methylnaphthalene, C11H10, is given the
value of 0 called cetane numbers.
25. What is “super charging” in diesel engine? And state its use.
Supercharging is the process of forcing of air fuel mixture or air alone into the engine cylinder during the
suction stroke at a pressure greater than that of atmospheric pressure. It is done to increase the density of air
fuel mixture. Or air admitted into the engine cylinder.
26. What are the different factors which influence knocking in petrol engines?
Temperature factors, density factors, time factors, and composition factors.
27. What are the advantages of supercharging?
 Complete combustion of mixture takes place inside the combustion of mixture takes place inside the
combustion chamber which increases the power output of the engine.
 The turbulence caused by supercharging assist in better mixing of fuel and air particles.
 Possibility of knocking is reduced in C.I. Engines.
 Specific fuel consumption is less due to complete combustion of air fuel mixture.
 Mechanical and thermal load carrying capacity of the engine increases with increase in supercharging.
 The exhaust gas temperature us reduced and there will be better scavenging.
28. What is pre – ignition? How can be detected?
Pre ignition is defined as phenomenon of ignition of the charge before the ignition spark occurs. Carbon
particles in the combustion chamber are over heated under certain operating conditions.
PART-B
Describe with suitable sketches the following system of a modern carburetor. (i) main
May/June
1 metering system (ii) idling system (iii) economizer system (iv) accelerating pump
2016
system (v) choke.
Refer:”Thermal Engineering” by Dr.R.K.Rajput Page No:

(iii) With a neat sketch, explain the principle of work of diesel fuel injector
(iv) A four-stroke, four-cylinder gasoline engine has a bore of 60mm and a stroke of
100 mm. On test it develops a torque of 66.5 N-m when running at 3000rpm. If May/June
2
the clearance volume in each cylinder is 60cc, the relative efficiency with respect 2016
to brake thermal efficiency is 0.5 and the calorific value of fuel is 42MJ/kg,
determine the fuel consumption in kg/h and the brake mean effective pressure.
(i) Explain the pressure lubrication system with a neat sketch. Nov/Dec
3
(ii) Explain the bosch fuel injector with a neat sketch. 2016
Discuss the difference between theoretical and actual valve timing diagrams of a Apr/May
4
diesel engine. 2015

Compare SI and CI engines with respect to i) Basic cycle ii) Introduction of fuel iii)
Nov-Dec
5 Fuel used iv) ignition v) Compression ratio vi) Speed vii) efficiency viii) Weight (16
2012
Marks)
Explain the phenomena of knocking in diesel engines. What are the different factors Apr/May
6
which influence knocking? 2015

A four-cylinder, four-stroke oil engine 10 cm in diameter and 15 cm in stroke
develops a torque of 185 Nm at 2000 rpm. The oil consumption is 14.5 lit/hr. The
specific gravity of the oil is 0.82 and calorific value of oil is 42,000 kJ/kg. If the Nov/Dec
7
IMEP taken from the indicator diagram is 6.7 bar, find (i) mechanical efficiency (ii) 2015
brake thermal efficiency (iii) brake mean effective pressure (iv) specific fuel
consumption in litres on brake power basis. (16 Marks)
Write a note on lubrication system for an IC engine in detail with relevant sketches of Nov/Dec
8
various types. (16 Marks) 2015

Nov-Dec
Explain how knocking taking place in S.I. engines and discuss the various factors 2010
9
which affect knocking in S.I engines. (16 Marks) Nov/Dec
2006 (1)
10 i) Compare four stroke and two stroke cycle engine ii) Explain with a sketche the May/June
non-exhaust emission from a vehicle. (9+7 marks) 2009
UNIT III - STEAM NOZZLES AND TURBINES
Flow of steam through nozzles, shapes of nozzles, effect of friction, critical pressure ratio,
supersaturated flow. Impulse and Reaction principles, compounding, velocity diagram for
simple and multi-stage turbines, speed regulations –Governors.
PART-A
1. What are the main classifications of steam turbine?
1. On the basis of method of steam expansion
a. Impulse turbine.
b. Reaction turbine.
c. Combination of impulse and reaction turbine
2. On the basis of number of stages.
a. Single stage turbines
b. Multi stage turbines
3. On the basis of steam flow directions
a. Axial turbine.
b. Radial turbine
c. Tangential turbine.
d. Mixed flow turbine.
4. On the basis of pressure of steam
a. High pressure turbine
b. Low pressure turbine
c. Medium pressure turbine
2. State the function of fixed blades.

The function of fixed blades is that they guide the steam as well as allow it to expand a larger
velocity
3. State the function of moving blades.
 It converts the kinetic energy of the steam into useful mechanical energy.
 The steam expands while flowing over the moving blades and thus gives reaction to the moving blades.
Hence the turbine is called as reaction turbine.
 The velocity of the steam decreases as the kinetic energy of the steam absorbed.
4. Differentiate between impulse and reaction turbines. (MAY’16, MAY’11, DEC’10, APR’04)
Si. Impulse Turbine Reaction Turbine

No.
1. It consists of nozzle and moving It consists of fixed blades and moving blades.
blades.
2. Pressure drops occurs only in nozzles Pressure drop occurs in fixed as well as moving
not in moving blades. blades.
3. Steam strikes the blade with kinetic Steam passes over the moving blades with pressure
energy. and kinetic energy.
4. It has constant blade channels area. It has varying blade channels area.
5. Due to more pressure drop per blade, Number of stages required is more due to more
number of stages required is less. pressure drop.
5. Give examples of impulse turbine and reaction turbine?

Impulse turbine – De level, curties and rateau
Reaction turbine – Parson
6. What is meant by degree of reaction?

Degree of reaction is defined as the ratio of enthalpy drop in moving blades to total enthalpy in the fixed
and moving blades (stage)
.
7.What are the three methods compounding?

1. Velocity compounding 2. Pressure compounding 3.Pressure – velocity compounding
.
8. What is hypothetical indicator diagram?
The theoretical cycle of the steam engine work on the Rankine cycle. The hypothetical indicator diagram
is the theoretical indicator diagram of a steam engine when there is no loss during the cycle.
9.Explain pressure compounding. (MAY’15)

The steam from the boiler is passed through the nozzle rings and moving blade rings alternately.
When the steam expands through nozzle, pressure of the steam decreases and velocity increases. When the
steam flows over moving blades, velocity of steam decrease and pressure remain constant. Then the steam
again expanded in the nozzle. This process is continued till the pressure of the steam is reduced from boiler
pressure to condenser pressure. The pressure of steam is reduced in each stage of nozzle ring and hence it is
known as pressure compounding.
10. Define diagram factor.
The ratio of the actual indicator diagram to the hypothetical indicator diagram is known as diagram
factor.
i.e., k = Area of actual indicator diagram
Area of hypothetical indicator diagram
11. Briefly explain the working of steam turbine.
Steam turbine consists of a nozzle and a rotary blade wheel. In the nozzle, the steam is expanded from a
high pressure to a low pressure. Due to this fall in pressure, a certain amount of heat energy is converted into
kinetic energy which causes the increase in velocity of steam. The steam with high velocity flows over a
curved blades and its direction of motion changed. This causes a change of momentum and force. This
constitutes the rotation of turbine shaft.
.
12. Define pure substance.
A pure substance is defined as a homogeneous material which retains its chemical composition even
though there may be a change of phase.
13.Give the classification of steam turbine. Steam turbines are classified as :
a. Impulse turbine b. Reaction turbine
.
14. Give the classification of steam turbines according to number of stages.
According to the numberof stages, steam turbines are classifed as :
a. Single stage turbine.
b. Multi stage turbine
15. Define impulse turbine. (DEC’11)
If at the inlet of the turbine, the energy available is only kinetic energy, then the turbine is known as
impulse turbine. eg: curties turbine
.
16. Define reaction turbine. (DEC’11)
If at the inlet of the turbine, the water possesses kinetic energy as well as pressure energy , then the
turbine is known as reaction turbine. eg. parson's turbine.
.
17. Define compounding of steam turbines. (NOV’15, NOV’10)
Compounding is defined as the method used for reducing rotor speed and sharing the loss of kinetic
energy in stages in an impulse turbine is known as compounding.
18.Define velocity diagram.

Velocity diagrams are defined as diagrams drawn to determine rate of change of momentum of steam
during the flow, through the moving blade in order to find force on the blades.
19. Define speed ratio.

Speed ratio (ρ) is defined as the ratio of tangential velocity of the blade (V) to absolute velocity of steam
at inlet of moving blade (Val).
ρ = V / Val
.
20. Define degree of Reaction (Rd). (MAY’14, APR’04)
The degree of reaction in an impulse reaction turbine is defined as the ratio of enthalpy drop in moving
blades to enthalpy drop in the stage.
21. What are the assumptions required to derive maximum efficiency?

The assumptions are,
i. The degree of reaction is 50%
ii. The moving and fixed blades are of the same shape
iii. The velocity of steam at exit from the proceeding stage is same as the velocity of steam at the
entrance to the succeeding stage.
22. What are the classifications of steam turbine on the basis of method of steam expansion?
Impulse turbine.
Reaction turbine.
Combination of impulse and reaction turbine
.
23. What are the classifications of steam turbine on the basis of number of blades?
Single stage turbines
Multi stage turbines
.
24. What are the classifications of steam turbine on the basis of steam flow direction?
Axial turbine.
Radial turbine
Tangential turbine.
Mixed flow turbine.
.
25. What are the classifications of steam turbine on the basis of pressure of steam?
High pressure turbine

Low pressure turbine
Medium pressure turbine
26. What are the external loses in turbine?

ESV & strainer losses
Governing losses (throttling losses)
Leaving Energy Losses (Latent heat of exhaust steam in condenser)
Radiation Loss to the surroundings
.
27. What are the external loses in turbine?
28.What are the internal loses in turbine?
Blade losses
Primary Losses:
Friction loss due to profile surface finish
Secondary Losses:
Impingement loss
.
29. What are the main constructional features of a turbine?
Casing, Rotor and Control stage
30. What is supersaturated flow? (MAY’15)

When the supersaturated steam is expanded in the nozzle, the condensation should
occur in the nozzle. Since the steam has a great velocity, the condensation does not take
place at the expected rate. So, the equilibrium between liquid and vapour phase is
delayed and the steam continues to expand in a dry state. The steam in such set of
condition is said to be supersaturated or metastable flow.
31. What is the effect of friction on the flow through a steam nozzle? (NOV’15)(NOV’16)
(i) The dryness fraction of the steam is increased
(ii) Entropy and specific volume of the steam are increased
(iii) Exit velocity of the steam is reduced
(iv) Mass of steam discharged is increased
PART-B
1..i)Define critical pressure ratio of a nozzle and discuss why attainment of sonic velocity
determines the maximum discharge through steam nozzle. (10 Marks) May/June
ii)Explain the metastable expansion of steam in a nozzle with help of h-s diagram. (6 2016
Marks)
2.
A simple impulse turbine has one ring of moving blades running at 150 m/sec. The
absolute velocity of steam at exit from the stage is 85 m/sec at angle of 80O from the
tangential direction. Blade velocity co-efficient is 0.82 and the rate of steam flowing May/June
through the stage is 2.5 kg/sec. If the blades are equiangular, determine (i) Blade angles 2016
(ii) Nozzle angle (iii) Absolute velocity of steam issuing from the nozzle (iv) Axial
thrust.
3
(i) Explain the pressure lubrication system with a neat sketch. Nov/Dec
e xplain the bosch fuel injector with a neat sketch. 2016

4
Air consumption for a four stroke petrol engine is measured by means of a circular orifice of
diameter 3.5 cm. The coefficient of discharge for the orifice is 0.6 and the pressure across the
orifice is 14 cm of water. The barometer reads 760 mm of Hg. The temperature of air in the
room is 24OC. The piston displacement volume is 1800 cm3. The compression ratio is 6.5. Nov/Dec
The fuel consumption is 0.13 kg/min and calorific value is 44000kJ/kg. The brake power 2016
developed at 2500 rpm is 28 kW. Determine (i) Air-Fuel ratio (ii) Volumetric efficiency on
the basis of air alone (iii) Brake mean effective pressure (iv) Relative efficiency on brake
thermal efficiency basis.
5
Discuss the difference between theoretical and actual valve timing diagrams of a diesel Apr/May
engine. 2015
Refer: :”Thermal Engineering” by Dr.R.K.Rajput , Page No:

6
Explain the phenomena of knocking in diesel engines. What are the different factors which Apr/May
influence knocking? 2015
Refer:”Thermal Engineering” by Dr.R.K.Rajput , Page No:

7
A four-cylinder, four-stroke oil engine 10 cm in diameter and 15 cm in stroke develops a
torque of 185 Nm at 2000 rpm. The oil consumption is 14.5 lit/hr. The specific gravity of the
Nov/Dec
oil is 0.82 and calorific value of oil is 42,000 kJ/kg. If the IMEP taken from the indicator
2015
diagram is 6.7 bar, find (i) mechanical efficiency (ii) brake thermal efficiency (iii) brake mean
effective pressure (iv) specific fuel consumption in litres on brake power basis. (16 Marks)
Refer:”Thermal Engineering” by Dr.R.K.Rajput , Page No:
8
Write a note on lubrication system for an IC engine in detail with relevant sketches of various Nov/Dec
types. (16 Marks) 2015
Refer:”Thermal Engineering” by Dr.R.K.Rajput, Page No:
9.
Nov-Dec Nov-
Explain how knocking taking place in S.I. engines and discuss the various 2010 Dec
factors which affect knocking in S.I engines. (16 Marks) Nov/Dec 2010
2006 (1) Nov/Dec
2006 (1)
Refer :”Thermal Engineering” by Dr.R.K.Rajput, Page No:

10
i) Compare four stroke and two stroke cycle engine ii) Explain with a sketche the non- May/June
exhaust emission from a vehicle. (9+7 marks) 2009
Refer :”Thermal Engineering” by Dr.R.K.Rajput, Page No:
UNIT IV – AIR COMPRESSOR
Classification and working principle of various types of compressors, work of compression

with and without clearance, Volumetric efficiency, Isothermal efficiency and Isentropic
efficiency of reciprocating compressors, Multistage air compressor and inter cooling –work
of multistage air compressor
.
PART-A
1.List out the components of reciprocating air compressor.
The components of reciprocating air compressor are,
i. Cylinder ii. Outlet valve iii. Piston
iv. Connecting rod v. Inlet valve
2.List out the types of air compressors.

The types of air compressors are,
i. Single acting compressor ii. Double acting compressor
iii. Single stage compressor iv. Multistage compressor.
2. Define single acting compressor.

Single acting compressor is a reciprocating compressor in which suction, compression and delivery of
the air takes place on one side of the piston only. It has only one delivery stroke per revolution of crankshaft.
3. Define double acting compressor.

Double acting compressor is a reciprocating compressor in which sqction, compression and delivery of
the air takes place on both sides of the piston. It has two delivery stroke per revolution of the crankshaft.
4. Define single stage compressor.
Single stage compressor is a compressor in which compression of air from initial pressure to final
pressure is carried out in one cylinder only. It is used when pressure ratio is low.
5. Define multistage compressor.

When the compression of air from initial pressure to final pressure is carried out in more than one
cylinder arranged in series, then the compressor is known as multistage compressor. It is necessary when the
pressure ratio is high.
6. Define ratio of compression.

Ratio of compression is the ratio of absolute discharge pressure to absolute inlet pressure. It is also
known as pressure ratio.
7. Define displacement of the compressor.

The swept volume of the piston is known as displacement of the compressor
8. Define actual capacity of the compressor.
The actual free air delivered per cycle (or) per minute is known as actual capacity of the compressor. The
actual capacity is always less than displacement. It is expressed in cubic meter of free air per minute.
9. List out the parts of a centrifugal compressor.

The parts of a centrifugal compressor are
i. Rotating impeller ii. Diffuser iii. Casing
10. Distinguish between rotary and reciprocating compressor.

Rotary compressor Reciprocating compressor
1. the maximum free air delivered is The maximum free air delivered is 300 m3 /
3000 m3 / min min.
2. These are smaller in size for the same These are larger in size for the same
discharge. discharge.
3. Lubricating system is simple. Lubricating system is complicated.
4. There is no balancing Balancing is the major problem
5. The air delivered is clean because it The air delivered is not clean as it has contact
does not come in contact with with lubricating oil.
lubricating oil.
6. The speed is high. The speed is low.
11. Define volumetric efficiency. (MAY’16, MAY’15)

Volumetric efficiency is defined as the ratio of volume of free air sucked into the compressor per cycle
to the stroke volume of the cylinder.
12. Define clearance ratio.
It is defined as the ratio of clearance volume to swept volume (or) stroke volume.
13.Define Isothermal Efficiency of air compressor.

It is defined as the ratio of isothermal work to Indicated work.
14. Compare the petrol and LPG?

PETROL LIQUIED PETROLEM GAS
Octane rating of petrol is 81 Octane rating of LPG is 110.
Petrol has odours LPG is odourless.
In order to increase octane number LPG is lead free with high Octane
number.
15. Define isentropic efficiency.
16. Explain how flow of air is controlled in a reciprocating compressor.
The flow of air is controlled by centrifugal governor, or by maintaining the speed of motor constant or
by providing the air pocket advancement to the cylinder.
17. Mention the important applications of compressed air.

Compressed air used in,
1. Pneumatic brakes 2. Pneumatic drills 3. Spray painting
4. Pneumatic Jacks 5. Air conditioning 6. Refrigeration
18. What factors limit the delivery pressure in a reciprocating compressor

1. To obtain high delivery pressure the size of the cylinder will be large.
2. Temperature of Air.
19. Why clearance is necessary and what is its effect on the performance of reciprocating compressor.
When the piston reaches top dead center in the cylinder, there is a dead space between piston top and
cylinder head. This space is known as clearance space and the volume occupied by this space is known as
clearance volume.
21. Define mean effective pressure.

Mean effective pressure is defined as hypothetical pressure, which is considered to be acting on the
piston IP throughout the power stroke.
22. Name the methods adopted for increasing isothermal efficiency of reciprocating air
compressor.
Isothermal efficiency is increased by perfect internal cooling.
. Which type of compression is the best in reciprocating compressor?
Isothermal compression.
24. What are the factors that affect the volumetric efficiency of a reciprocating
compressor? (MAY’16)
1.Clearance volume. 2.Compression ratio.
25. Discuss the effect of clearance upon the performance of an air compressor.
The volumetric efficiency of air compressor increases with decreasing the clearance of the compressor.
The free air delivered by the compressor is increased by decreasing the clearance volume.
26. What is meant by inter cooler?

An inter cooler is a simple heat exchanger. It exchanges the heat of compressed air from the low pressure
compressor to the circulating water before the air enters to the high pressure compressor. The purpose of
inter cooling is to minimize the work of compression.
27. What are the the classification of reciprocating compressors?

In-line compressors, “V”-shaped compressors, Tandem Piston compressors. Single-acting compressors, Double-
acting compressors, and Diaphragm compressors.
28. What are the types of rotary compressors?

Screw compressors, Vane type compressors, Lobe and scroll compressors and other types.
29. What are the types Under the Roto-dynamic compressors?

Centrifugal compressors, and the Axial flow compressors.
31. How compressors are classified based on other aspects?

Number of stages, Cooling method and medium, Drive types Lubrication method and Service Pressure
PART-B
A two-stage air compressor consists of three cylinders having the same bore and stroke.
The delivery pressure is 7 bar and the free air delivery is 4.3 m3/min. Air is drawn in at
May/June
1 1.013 bar , and 15OC and an intercooler cools the air to 38OC. The index of compression
2016
is 1.3 for all three cylinders. Neglecting clearance calculate, (i) the intermediate
pressure (ii) the power required to drive the compressor (iii) the isothermal efficiency
Refer: “Thermal Engineering” by Dr.R.K.Rajput Page No:
2
With a neat sketch, describe the construction and working of a single stage acting
May/June
2 reciprocating air compressor. Also derive the equation for work done with clearance and
2016
without clearance.
The FAD (free air delivered) of a single cylinder single stage air compressor is 2.5
m3/min. The ambient is at 20C and 1.013 bar and delivery pressure is 7 bar. The
clearance volume is 5% of the stroke volume and law of compression and expansion is Nov/Dec
3
PV1.25=C. Stroke length is 20% more than that of the bore.Compressor runs at 150 rpm. 2016
Determine the mass of air per second, indicated power, indicated mean effective
pressure and bore and stroke of the cylinder. (16 Marks)
Explain the construction and working principle of centrifugal compressor and axial flow Nov/Dec
4
compressor with neat sketches. 2016
.
A single acting, single stage air compressor delivers 0.6 kg of air per minute at 6 bar.
The temperature and pressure at the end of suction stroke are 30OC and 1 bar. The bore
and stroke of the compressor are 100 mm and 150 mm respectively. The clearance is April/May
5
3% of swept volume. Assuming the index of compression and expansion to be 1.3. Find 2015
(i) volumetric efficiency of the compressor (ii) power required if the mechanical
efficiency is 85% and (iii) speed of compressor (rpm).
In a single acting two stage reciprocating air compressor 4.5 kg of air per min. are
compressed from 1.013 bar and 15OC through a pressure ratio of 9 to 1. Both stage have
the same pressure ratio, and the law of compression and expansion in both stages is April/May
6
pV1.3=C. Calculate (i) the indicated power (ii) the cylinder swept volume required. 2015
Assume that the clearance volume of both stages are 5% of their respective swept
volumes and that the compressor runs at 300 rpm.

A single acting air compressor takes in atmospheric air (atm condition 101.325 kPa,
27OC) and delivers it at 1.4 MPa. The compressor runs at 300 rpm and has cylinder
diameter of 160 mm and stroke 200 mm. Clearence volume is 5% of stroke volume. If
Nov/Dec
7 the pressure and temperature of air at the end of suction stroke are 100kPa and 47 OC,
2015
and law of compression and expansion is pV1.2=C, determine (i) mass of the sir
delivered per minute (ii) volumetric efficiency (iii) driving power required, if
mechanical efficiency is 85%.
A three stage air compressor with perfect intercooling takes 15 m3 of air per minute at
95 kPa and 27OC, delivers the air at 3.5 MPa. If compression process is polytropic
Nov/Dec
8 (pV1.3=C), determine (i) Power required if mechanical efficiency is 90% (ii) heat
2015
rejected in the intercoolers per minute (iii) isothermal efficiency (iv) heat rejected
through cylinder walls per minute.
Derive an expression for the minimum work required for a two stage reciprocating air
Nov-Dec
9 compressor with perfect inter-cooling and prove that the intercooler pressure is the
2010
geometric mean of the initial and final pressure. (16 Marks)
Write working principle of multi-stage reciprocating air compressor. Derive the
Nov/Dec
10 condition for minimum work output of two stage reciprocating air compressor and work
2011
output relation for multi stage reciprocating air compressor. (16 Marks)
UNIT V - REFRIGERATION AND AIR CONDITIONING
Refrigerants - Vapour compression refrigeration cycle- super heat, sub cooling – Performance ca
Types and Working Principles. - Concept of RSHF, GSHF, ESHF- Cooling Load calculations.
1. Define C.O.P. of a refrigeration system.

C.O.P. of a refrigeration system is the ratio of heat removed from the low temperature system to the work supp
C.O.P = Q / W
Where, W = Work supplied in kJ per unit time, Q = Heat removed in kJ per unit time, C.O.P. -Coeff
2. Define refrigerator.
A refrigerator is equipment which is used to remove heat continuously from space and maintain temperature be
3. Define heat pump.

A heat pump is equipment used to supply heat continuously to space and maintain the temperature above atmos
4. Define DPT and Degree of saturation.

DPT (Dew Point Temperature) is the temperature to which moist air is to be cooled before it starts condensing.
Degree of saturation is the ratio of specific humidity of moist air to the specific humidity of saturated air at tem
5. Define Relative humidity (RH) and Specific humidity.

RH is the ratio of mass of water vapour (mv) in a certain volume of moist air at a given temperature to the mass
Specific humidity (ώ) is the ratio of mass of water vapour (mv) to the mass of dry air in the given volume of m
6. What are the classifications of air conditioning system?

I. Based on construction of components:
 Unitary system
 Central system
 Package system
 Split units
II. Based on fluid flow methods:
 Direct expansion system
 Chilled water system
 Chilled water air washer system.
7. How does humidity affect human comfort?

If the humidity is above a certain level, water vapour from human body moisture cannot be absorbed by atmosp
8. Define: RSHF, RTH.

RSHF (Room Sensible Heat Factor) is the ratio of room sensible heat (RSH) to room total heat.
RSHF = RSH / RTH
RTH (Room Total Heat) is the sum of room sensible heat and room latent heat.
RTH = RSH+RLH
9. What are the various sources of heat gain of an air conditioned space?
 Solar gain through glass plates
 Solar gain through roof and walls
 Heat gain from occupants
 Heat gain from appliances and lights.
 Duck leakage
 Infiltration
 Vapour transmission
10. Define apparatus dew point (ADP) of cooling coil.

For dehumidification, the cooling coil is to be kept at a mean temperature which is below the dew point temper
11. Define bypass factor (BPF) of a coil.

The ratio of the amount of air which does not contact the cooling coil (amount of bypassing air) to the amount o
i.e. BPF = amount of air bypassing the coil / Total amount of air passed.
12. What is psychrometry ?

Psychrometry is a study of properties of moist air. It deals with the state of atmosphere with respect to moistur
commodities and the human comforts.
13. Define DPT and Degree of saturation.

DPT (Dew Point Temperature) is the temperature to which moist air is to be cooled before it starts condensing.
Degree of saturation is the ratio of specific humidity of moist air to the specific humidity of saturated air at tem
14. Define Relative humidity (RH) and Specific humidity.

It is the ratio of the actual partial pressure of water vapour in the moist air to the
Saturation pressure of water vapour corresponding to the dry-bulb temperature, i.e.,
Existing partial pressure of water vapour, Pv
 
The saturation pressure of pure water vapour at the same temperature, Ps
15. How does humidity affect human comfort?
If the humidity is above a certain level, water vapour from human body moisture cannot be absorbed by atmosp
16. What are the various sources of heat gain of an air conditioned space?
1. Solar gain through glass plates
2. Solar gain through roof and walls
3. Heat gain from occupants
4. Heat gain from appliances and lights.
5. Duck leakage
6. Infiltration
7. Vapour transmission
17. State the effects of very high and a very low bypass factor.
Very high BPF:
a. Requires lower ADP. Refrigerant plant should be of larger capacity.
b. Requires more air. Larger fan and motor required.
c. Less heat transfer area.
d. Requires more chilling water. Larger piping required.
Very low BPF:
a. Higher ADP is to be employed.
b. Requires less air. Fan and motor size reduced.
18. What factors affect BPF?

a. Pitch of fins. b. Number of coil tubes
c. Air velocity over the coil. d. Direction of air flow.
19. What are the requirements of comfort air conditioning?

a. Supply of O2 and removal of CO2.
b. Removal of heat of occupants.
c. Removal of moisture of occupants.
d. Good air distribution.
e. Maintaining air purity.
20. Define Effective Temperature (ET).

ET is defined as that temperature of saturated air at which the subject would experience the same feeling of com
21. What are the general comfort conditions during summer and winter?
Summer:
Inside temperature 24o±1oC
RH 50 – 60 %
Air movement 4.5 – 7.5 m / min.
Winter:
Inside temperature 20o±1oC
RH 35 – 40%
22. Differentiate between heat pump and refrigerator. (AU' MAY 2003)
Refrigeration may be defined as the process by which the temperature of a given space or a substance is lowere
23. What is dew point temperature? (AU' MAY 2004)

Dew point temperature is temperature to which moist air is to be cooled before it starts condensing.
24. What is effective temperature? (AU' MAY 2004)

Effective temperature is defined as that temperature of saturated air at which the subject would experience the s
25. Define dew point depression.

It is the difference between dry bulb temperature and dew point temperature of air vapour mixture.
26. Define Dew point,Tdp :

It is the temperature at which the liquid droplets just appear when the moist air is Cooled continuously
27. What is meant by Absolute humidity?

It is the amount of water vapour per unit volume of the gas.
28. What is Humidity Ratio?

It is also called the specific humidity. It is defined as the amount of water vapour in the moist air per unit mass
29. What is Saturated air?

A mixture of dry air and water vapour in which the patial pressure of the vapour is equal to saturation
30. What is Degree of saturation, µ?

It is defined as a ratio of the mass of the water vapour at a given temperature associated with the unit mass of d
µ =mv/mvs
1 Describe the following refrigeration systems with layout (i) Ammonia water system (ii) Lithium-br

(i) Describe the working principle of centralized air conditioning system and enumerate the ne
2
(ii) List the loads that contribute to the overall cooling load.
A food storage locker requires a refrigeration capacity of 50 kW. It works between a condenser te
3
saturated vapour leaving the evaporator. Assuming a single cylinder, single acting compressor oper
(i) Explain the centralized air conditioning system with a neat sketch
4
(ii) 100 m3 of air per minute at 15OC DBT 80% RH is heated until its temperature is 22OC. Calcul
An ammonia refrigerator operates between evaporating and condensing temperatures of -16OC an

5
Calculate (i) The refrigerator effect per kg (ii) The mass flow and power input per kw of refrigerati
Refer: ͞Thermal Engineering͟ by Dr.R.K.Rajput Page No:
Saturated air leaving the cooling section of an air conditioning system at 14OC at a rate of 50 m3/m
6
atm, determine the specific humidity, the relative humidity, the dry-bulb temperature and the volum
.
An air conditioning plant is required to supply 50 m3 of air per minute at a DBT of 22OC and 50%
7
dehumidification and sensible cooling process. Also calculate sensible heat factor.
8
i) Explain the construction and working of vapour absorption refrigeration system with neat sketch
9
i) Explain the working principle of vapour absorption refrigeration system and compare it with vapour compressio
diagram for Freon 12, determine i) The mass flow rate of the refrigerant circulated. ii) the theoretical piston disp
condenser. (16 Marks)
10
Explain the construction and working of summer and winter air conditioning systems. (16 Marks)

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JEPPIAAR ENGINEERING COLLEGE

Jeppiaar Nagar, Rajiv Gandhi Salai – 600 119

DEPARTMENT OF MECHANICAL ENGINEERING

ME6404 – THERMAL ENGINEERING

DEPARTMENT OF MECHANICAL ENGINEERING

Subject : ME6404 – THERMAL ENGINEERING

UNIT I GAS POWER CYCLES

22 BTL-1 Remembering PO1

23 Define clearance volume. BTL-1 Remembering PO1

What is the expression for efficiency of Dual

UNIT II INTERNAL COMBUSTION ENGINES

What is meant by degree of reaction?

9 What is hypothetical indicator diagram? BTL-1 Remembering PO1, PO6, PO7

10 Explain pressure compounding BTL-1 Remembering PO1, PO6, PO7

What are the classifications of steam turbine on

What are the classifications of steam turbine on

What are the classifications of steam turbine on

What are the classifications of steam turbine on

What are the external loses in turbine?

30 What is supersaturated flow? BTL-1 Remembering PO1

UNIT IV AIR COMPRESSOR

The FAD (free air delivered) of a single cylinder

UNIT I GAS POWER CYCLES

1-2 Isentropic compression

1-2 Isentropic compression

5. Mention the various processes of the Brayton cycle. (OCT’96)

6. Mention the four thermodynamic processes involved in Diesel cycle. ( APR’08)

7. Mention the various process of Dual cyale. (APR’96)

19. Name the various Gas power cycles.

23. Define clearance volume.

26. Compare Otto and Diesel cycles.

we know that Cp > Cv

(T3’- T2) < (T3- T2)

27. What is the expression for efficiency of Dual cycle?

28. What is the expression for efficiency of Diesel cycle?

Otto cycle Diesel cycle

UNIT II INTERNAL COMBUSTION ENGINE

19. What is the fuel injector?

24. How fuels are rated? Explain.

Refer:”Thermal Engineering” by Dr.R.K.Rajput Page No:

Refer:”Thermal Engineering” by Dr.R.K.Rajput Page No:

Refer:”Thermal Engineering” by Dr.R.K.Rajput Page No:

Refer:”Thermal Engineering” by Dr.R.K.Rajput Page No:

Refer:”Thermal Engineering” by Dr.R.K.Rajput Page No:

Refer:”Thermal Engineering” by Dr.R.K.Rajput Page No:

UNIT III - STEAM NOZZLES AND TURBINES

2. State the function of fixed blades.

Si. Impulse Turbine Reaction Turbine

5. Give examples of impulse turbine and reaction turbine?

6. What is meant by degree of reaction?

7.What are the three methods compounding?

9.Explain pressure compounding. (MAY’15)

18.Define velocity diagram.

19. Define speed ratio.

21. What are the assumptions required to derive maximum efficiency?

High pressure turbine

26. What are the external loses in turbine?

Friction loss due to profile surface finish