Theory of Internal Combustion Engines and Emissions

MME 4036 THEORY OF INTERNAL COMBUSTION ENGINES AND

EMISSIONS
THEORY OF INTERNAL COMBUSTION ENGINES AND

[3 0 0 3]
No. of Lecture hours: 36

Introduction: Thermodynamics and Classification of IC engines, Idealized cycles and Processes:

Otto, Diesel, Dual and Sterling Cycle. Comparison of Air-standard Cycle, Fuel air cycles and
actual cycles. [04]

Fundamentals of combustion: Introduction to combustion, modes of combustion,

Stoichiometry, heat of formation, adiabatic flame temperature, chemical equilibrium. ignition
limits, simple numericals. [04]

IC engine fuels: conventional and non-conventional fuels. Conventional fuels, chemical

EMISSIONS

structure of petroleum products, refining process, products of refinery, required qualities of

engine fuels, rating of fuels, SI engine and CI engine fuels. Non-conventional fuels (alternative
fuels): Alcohols, LPG, CNG, Hydrogen, Vegetable oils. [06]

Combustion in SI and CI engines: Combustion in SI engines: Stages of combustion, factors

affecting the different stages of combustion, rate of pressure rise, Normal and abnormal
combustion and Combustion Knock. Design and operational factors for control of knock.
Combustion chamber design for SI engines. Combustion Phenomenon in CI engines: Stages of
combustion, Delay period physical and chemical delay period, abnormal combustion in CI
engines- Diesel Knock. Factors affecting delay period. Control of diesel knock.SI and Ci engine
combustion chamber designs [08]

Modern developments in IC engines: Rotary (Wankel engine) combustion engine. Electronic

injection systems like CRDI, MPFI, TBI and GDI systems Dual fuel engines and stratified charge
engines. [04]

Engine pollutant formation and control: Introduction to pollution, Nitrogen Oxides, kinetics of
NOX formation in SI engine and CI engine. CO emission, UBHC emission, flame quenching, HC
emission from SI and CI engines. Particulate emissions, soot formation, oxidation and
adsorption and condensation. Exhaust and non-exhaust emissions: Exhaust emission control
methods- thermal reactors, catalytic converters and particulate traps, chemical methods like
ammonia injection. EGR technique, Non- exhaust emissions - evaporative emissions and crank
case emissions and its control. . [10]

Department of Mechanical and Manufacturing Engineering, MIT, Manipal

 Theory of Internal Combustion Engines and Emissions

MME 4036 – THEORY OF INTERNAL COMBUSTION ENGINES

AND EMISSIONS
References:

1. Ganeshan V., Internal Combustion Engines, (3e), Tata McGraw Hill Education
Private Limited, New Delhi, 2007.
2. Mathur and Sharma, A Course in I C Engines, DhanpathRai Publishers, New
Delhi, 1981.
3. John B. Heywood, Introduction to Internal Combustion Engines, Tata McGraw
Hill Education Private Limited, New Delhi, 2011.
4. Lichty L.C., International Combustion Engines, McGraw Hill, New Delhi, 1951.
5. Edward F. Obert, Internal Combustion Engines and Air Pollution, Harper & Row,
Publishers. Delhi, 1973.
6. Richard Stone, Introduction to Internal Combustion Engines, The McMillan
Press, New Delhi, 1999.

1.

Department of Mechanical and Manufacturing Engineering, MIT, Manipal

 Theory of Internal Combustion Engines and Emissions

Table 1 COMPARATIVE PROPERTIES OF S.I. ENGINE FUELS

Fuel Gasoline Propane Methanol Ethanol Hydrogen Ammonia Biogas CNG
Property (LPG) (60%CH4 ) (96%CH4 )
Liquid Density 0.70 0.582 0.79 0.78 0.07 0.68 __ __
o
at 15 C (g/cc) (at 20 K)
Latent Heat 303 425 1168 920 456 1306 __ 510
(kJ/kg)
o
Vap.pr@38 C 0.8 bar 13.3 bar 0.32 bar 0.16 bar
Heating Value 44,000 46,000 19,600 26,750 1,20,000 18,600 14,500 55,200
(kJ/kg)
Volumetric
Liquid Energy
Density(kJ/Lit) 30,800 26,800 15,480 20,870 8400 12,650 --- ---
at atm.pr.& temp.
`
Stoichiometric 15.0 15.6 6.4 8.95 34.5 6.06 5.9 17.3
A/F by mass
Flammability
Limits (% by vol. 1.2 - 6 2.2 - 9.5 7 – 36 4.3 – 18 4 – 75 16 – 29 --- 5.3 – 15
of vapour)
A/F by mass at 21.5 (lean) 29.9 12.9 15.0 360.0 10.6 __ 34.2
the limits 4.5 (rich) 6.93 2.5 3.51 19.3 5.88 __ 12.08
Max. possible 44 91.6 101 68 943 75 __ 97.6
leaning air (%)
(Lean limit Ø) 0.686 0.515 0.493 0.609 0.093 0.549 --- 0.502
Octane Number 85 –100 >100 106 -115 > 100 > 100 --- > 100 130
(Research)
B.Pt. at atm. pr. 99.5 -42.18 65 78 - 253 - 33 --- - 161.4
o (50 to 220)
( C)
Toxicity low nil high nil nil high nil nil
Total System
Efficiency (%) 15 9.0 12 13.5 6.3 7 --- --
(from Production
to Utilization)

Department of Mechanical and Manufacturing Engineering, MIT, Manipal

 Theory of Internal Combustion Engines and Emissions

1. Advantages of Alcohol over gasoline

• Renewable in nature
• Higher Octane rating
• Lean burning ability
• Higher power due to better volumetric efficiency
• Higher thermal efficiency dueto higher HUCR
2. Limitations of Alcohol over gasoline
• Lesser CV and Higher cost.
• Difficult cold starting.

Department of Mechanical and Manufacturing Engineering, MIT, Manipal

 Theory of Internal Combustion Engines and Emissions

• Poor volatility characteristic hence vapor lock problem during hot starting and
acceleration.
• Water absorption- hence metal corrosion problem
• Chemical attack on plastic components in direct contact
• Lower overall system efficiency- production to utilization.
Alcohol gasoline blends (upto 20% alcohol) can be used in SI engines without any engine
modifications.
• Utilization of alcohol blend for automobiles requires proper monitoring, accounting and
caution in handling stations.
• Utmost care should be taken to store the alcohol and its blends to keep away from
moisture.
• Adequate steps should be taken to double the alcohol production to meet the
requirement.
------------------------------------------------------------------
Utilization of alcohol in Diesel engines
• Blend of moisture free alcohol in Diesel ( Upto 20%) can be used
• Duel injection (Upto 20%)
• Bi fuel operation (Upto 50% in DI engines) by fumigation

MERITS OF HYDROGEN AS AN ALTERNATIVE FUEL

 Hydrogen has the fastest burning velocity which causes rapid combustion and hence
high engine speed, thereby improving the specific output.
 It has an excellent lean burning ability which improves its thermal efficiency.
 It has a high Octane Number, which enables higher CR to be used with the associated
higher Klimep and higher energy conversion efficiency.
 It has a high self ignition temperature (581ºC compared to 450ºC for gasoline or 466ºC
for propane and 534ºC for methane) which makes it highly knock resistant.

Department of Mechanical and Manufacturing Engineering, MIT, Manipal

 Theory of Internal Combustion Engines and Emissions

 When it burns in air it produces steam and the exhaust is devoid of CO, CO 2, SO2, smoke
and Carcinogens. The only expected pollutant is NOx which can be easily controlled by
lean burning or by EGR technique.
 Tasteless, odourless and non-toxic by itself, hydrogen gives out just clean energy
producing steam, thereby maintaining the Nature’s balance of water in the
hydrosphere.
 It is highly combustible, requiring very little energy (1/12 of gasoline) to ignite it. (0.02
mJ compared to 0.25 mJ for gasoline and propane and 0.3 mJ for methane under similar
laboratory test conditions).
 It has a very high calorific value on mass basis.
DE-MERITS OF HYDROGEN
 Its high combustibility can cause fire hazards and inlet back fire. This requires flame
traps, flash back arresters and crank case ventilation to prevent explosions due to blow-
by accumulation.
 Even when a fuel cell is being used, the design has to account for the weather, because
in cold weather conditions there will be freezing of water which is a byproduct of the
reaction. The freezing of water can be harmful for the fuel cell.
 Due to its very low density (0.09 kg/m³ for the gas) it has a very low volumetric energy
density and hence on-board storage requires a large volume for a given mass.
 Due to complexity and cost of cryogenic liquid hydrogen storage, carrying hydrogen on
board in a vehicle is a challenging task. One of the acceptable solutions is storage in the
form of metal hydrides, which, unfortunately, can hold only about 2 to 8% by mass of
hydrogen in it.
 Hydrogen is very expensive and its production is highly energy intensive.
PRODUCTION OF HYDROGEN
Hydrogen can be produced by several methods. 65% of the total production of
hydrogen in the world is by catalytic steam reforming of methane or naptha, 25% by
partial oxidation of heavy oils, 7% by water gas reaction from coal/coke and 3% by
electrolysis of water.
Direct thermal splitting of H2O (at 3000ºC) using solar focusing collectors, thermo-
chemical splitting of H2O (at 850ºC) using FeCl2 or CrCl2, modified photosynthetic
reactions in green plants and algae using specific enzymes etc. are some of the
techniques under consideration and development to produce hydrogen.

Department of Mechanical and Manufacturing Engineering, MIT, Manipal

 Theory of Internal Combustion Engines and Emissions

METHODS OF ADMISSION OF HYDROGEN INTO THE ENGINE CYLINDER

1. Carburetion or valve controlled flow into the intake manifold directly from hydrogen
cylinder or hydride storage.
2. Manifold hydrogen gas injection.
3. Direct in-cylinder injection (Gas or Liquid)
ON-BOARD STORAGE OF HYDROGEN
 Compressed hydrogen gas storage in high pressure cylinders
 Hydrogen storage in the liquid form
 Metal hydride storage
Comparison of typical hydrogen storage systems for equal energy storage

Fuel Container volume in Mass of fuel in kg Mass of container +

liters fuel(kg)

Gasoline 75.7 53.1 68

Liquid hydrogen 275 19.5 136

Hydrogen gas at 138bar 1820 19.5 2090

Metal Hydride: Mg-Ni 310 19.5 316

In the chart it can be seen that transportation of hydrogen is very inefficient. If the total mass of
the container and fuel is 2090 kg, only 19.5 kg of the total mass will be hydrogen gas. If
hydrogen is transported in liquid state, then for a total mass (Container+Fuel) of 136 kg, only
19.5 kg will be liquid hydrogen.

Department of Mechanical and Manufacturing Engineering, MIT, Manipal

 Theory of Internal Combustion Engines and Emissions

Hydrogen storage system in a passenger car

• The cars must have detectors that will immediately recognise a leak. Hydrogen disperses
very fast because it is very light.
• The safety features involve a hydrogen vent which will immediately vent the hydrogen
in case of an accident.
• In hydrogen supply we tend to think in terms of weight and not in terms of volume,
because volume can change depending on the pressure at which the hydrogen is
supplied.
• To increase the mass of hydrogen going in the hydrogen is supplied at a high pressure.
So the pump when you clamp the nozzle onto the gas tank has to form a very tight seal.
Unless the pump knows that the seal is tight, the pump will not turn on.
Hydrogen as an alternative fuel –conclusion
Technical feasibility of hydrogen as a renewable alternative to petroleum fuels has been
successfully demonstrated by experiments in the laboratory as well as on the road. However,
before hydrogen can be considered for wide use in automobiles further research efforts are
required in the following areas-

Department of Mechanical and Manufacturing Engineering, MIT, Manipal

 Theory of Internal Combustion Engines and Emissions

■ Production of hydrogen at an affordable cost

■ On-board storage of hydrogen with improved power to weight ratio
■ Safe methods to prevent fire hazards during operation and due to accidents
■ Analysis of hydrogen supply system with computerized control of mixture ratio in
response to drive commands and exhaust emission levels
■ Performance studies on all-weather and altitude operation including extreme cold starting
In general it is seen that the merits of hydrogen out-weigh the limitations and hence
hydrogen promises to emerge out as the most attractive fuel of the future, particularly for the
transportation sector.

Department of Mechanical and Manufacturing Engineering, MIT, Manipal