Gas Power Cycle - Assignment

GAS POWER CYCLE ASSIGNMENT
1. What are the air-standard assumptions?
2. What is the difference between the clearance volume and the

displacement volume of reciprocating engines?
3. What is the difference between spark-ignition and compression-ignition

engines?
4. What four processes make up the ideal Otto cycle?
5. How does the ideal Diesel cycle differ from the ideal Otto cycle?
6. What four processes make up the simple ideal Brayton cycle?
7. An engine working on air standard Otto cycle has a cylinder diameter of

10cm and stroke length of 15 cm. The ratio of specific heats for air is 1.4.
If theclearance volume is 196.3 cc and the heat supplied per kg of air per
cycle is1800kJ/kg, then calculate the work output per cycle per kg of air.
8. For an engine operating on air standard Otto cycle, the clearance volume
is10% of the swept volume. The specific heat ratio of air is 1.4. Calculate
the air standardcycle efficiency.
9. An ideal air standard Otto cycle has a compression ratio of 8.5. If the
ratio of the specific heats of (y) is 1.4, then what is the thermal efficiency
(in percentage) of the Otto cycle?
10. In an air-standard Otto cycle, the compression ratio is 10. The condition
at the beginning of the compression process is 100 kPa and 270C. Heat
added at constant volume is 1500 kJ/kg, while 700 kJ/kg of heat is
rejected during the other constant volume process in the cycle. Specific
gas constant for air = 0.287 kJ/kgK. Calculate the mean effective pressure
(in kPa) of the cycle.
11. In a spark ignition engine working on the ideal Otto cycle, the
compression ratio is 5.5. The work output per cycle (i.e., area of the P-V
diagram) is equal to 23.625 x 105 x Vc J, where Vc is the clearance volume
in m3. Calculate the indicated mean effective pressure.
12. The stroke and bore of a four stroke spark ignition engine are 250 mm
and 200 mm respectively. The clearance volume is 0.001 m3. If the
specific heat ratio γ = 1.4, find the air-standard cycle efficiency of the
engine.
13. In an air-standard Otto cycle, air is supplied at 0.1 MPa and 308 K. The
ratio of the specific heats (γ) and the specific gas constant (R) of air are
1.4 and 288.8 J/kg.K, respectively. If the compression ratio is 8 and the
maximum temperature in the cycle is 2660 K, calculate the heat (in
kJ/kg) supplied to the engine.
14. A diesel engine has a compression ratio of 17 and cut-off takes place at
10% of the stroke. Assuming ratio of specific heats as 1.4, find the air-
standard efficiency.
15. In a compression ignition engine, the inlet air pressure is 1 bar and the
pressure at the end of isentropic compression is 32.42 bar. The
expansion ratio is 8. Assuming ratio of specific heats (γ) as 1.4, find the
air standard efficiency (in percent).
16. Air enters a diesel engine with a density of 1.0 kg/m3. The compression
ratio is 21. At steady state, the air intake is 30 × 10–3 kg/s and the net
work output is 15 kW. Calculate the mean effective pressure (kPa).
17. An ideal Brayton cycle, operating between the pressure limits of 1 bar
and 6 bar, has minimum and maximum temperature of 300 K and 1500
K. The ratio of specific heats of the working fluid is 1.4. Calculate the
approximate final temperatures in Kelvin at the end of compression and
expansion processes respectively.
18. In a simple Brayton cycle, the pressure ratio is 8 and temperatures at the
entrance of compressor and turbine are 300 K and 1400 K, respectively.
Both compressor and gas turbine have isentropic efficiencies equal to
0.8. For the gas, assume a constant value of cp(specific heat at constant
pressure) equal to 1 kJ/kgK and ratio of specific heats as 1.4. Neglect
changes in kinetic and potential energies. Calculate the power required
by the compressor in kW/kg of gas flow rate.
19. In an ideal Brayton cycle, atmospheric air (ratio of specific heats, cp/cv =
1.4, specific heat at constant pressure = 1.005 kJ/kg.K) at 1 bar and 300 K
is compressed to 8 bar. The maximum temperature in the cycle is limited
to 1280 K. If the heat is supplied at the rate of 80 MW, find the mass
flow rate (in kg/s) of air required in the cycle.
20. The pressure ratio across a gas turbine (for air, specific heat at constant
pressure, cp = 1040 J/kg K and ratio of specific heat γ = 1.4) is 10. If the
inlet temperature to the turbine is 1200 K and the isentropic efficiency is
0.9, calculate the gas temperature at turbine exit in K.

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GAS POWER CYCLE ASSIGNMENT

1. What are the air-standard assumptions?

2. What is the difference between the clearance volume and the

3. What is the difference between spark-ignition and compression-ignition

4. What four processes make up the ideal Otto cycle?

6. What four processes make up the simple ideal Brayton cycle?

7. An engine working on air standard Otto cycle has a cylinder diameter of

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