IC engines is a scoring area, there are usually straightforward questions from engine testing, carburetion or diesel injection, emissions, knocking etc. So, good returns on specific minimal effort. No need for PhD in engines.Below, I have taken up numericals first because 1.they are the scoring areas and need immediate attention., 2.they can be understood even with general sense of engines. Books usually put them in end. By that time, we know much about engines, but we run out of energy to push thru these tedious procedural questions.
Please feel free to give your inputs/corrections/suggestions on any topic or any solved question below. Do quote the Q no. ex 2015A3b20 or topic name while doing so. Cheers!
General
Difference between External combustion engine and Internal combustion engine
Basic engine parts, nomenclature, materials used, dimension terms
Classification of engines
4 stroke and 2 stroke engines, valve timings, differences
Engine testing numericals
ip, bp, n-ith, n-bth, n-m, n-v, isfc, bsfc, F/A, A/F
Balance sheet on minute basis
2015A3b20 Petrol engine, 4S, 9cyl, D=14.5cm, L=18cm, r=7, bp 350kW @ 2000rpm, when mix is 15% weak with 82.5%C ad 14.8% H2, CV=47MJ/kg , vol eff=0.76 at 15degC, 1 bar, (eta-m)=0.9, R=0.287kJ/kgK, to find: (eta-ith)
Ans: Now, bp=350kW so, ip =bp/(eta-m)=350/0.9 =388.9kW
(eta-ith)=ip/(mf x CV) and (eta-v)= ma /( rho x pi D^2 L /4 x N/120 x n)
now that catch in the question is to get air mass rate ma and then A/F, then mf and hence eta-ith
so, ma= (eta-v) x RT/p x pi D^2 L /4 x N/2 x n
ma= 0.76 x 287 (273+15) /10^5 x pi x 0.145^2 x 0.18 /4 x 2000/120 x 9 = 0.28 kg/s
in above, i have used rho =RT/p gas eqn, vol of cyl =pi D^2 L/4, cycles per sec=N/(2x60), n=9 cyls
Now, consider 100kg fuel, mixed in stoichiometric ratio then
(82.5/12)C + (14.8/2)H2 +(aO2 + 79.1a/20.9 N2) -->bCO2 +dO2 + eN2 +fH2O
so, b=6.875, d=0 no excess air, a=d+b+f/2 = 0+6.875+7.4/2=10.575 kmoles(air required for stoichio)
So for 15% weak mix, air required =0.85 x 10.575 kmoles=8.98875 kmoles
so, ma=(ax32 + 79.1a/20.9 x28)= (32 + 79.1/20.9x28)x8.98875=1241.57kg/s when mf=100kg/s
or A/F=ma/mf=12.4157, so for ma=0.28 kg/s, mf=0.28/12.4157=0.02255 kg/s
(eta-ith)=388.9kW/(0.02255 kg/s x 47000 kJ/kg) = 0.367
Emissions related theory and numericals
Apparatus for measuring exhaust emissions
Gasoline engine emission control
Diesel smoke and control
Air standard cycles
Carnot
Stirling 1816
Ericsson
Lenoir
Constant volume or Otto
Diesel cycle
Dual cycle
Atkinson
Joule or Brayton cycle
Fuel air cycles and actual cycles(no numericals from here, don't break your head over them)
Assumptions made in fuel air cycle
Loss due to variation of specific heat on p-v diagram
Effect of disassociation on temperature at different mixture strength, and on power
Effect of variable on p, T in cylinder
1.compression ratio
2.F/A ratio
-on efficiency
-on max power
-on max temp
-on max pr
-on exhaust temp
-on mep
Losses in an actual cycle
-Time losses
-Direct heat losses
-Exhaust blowdown loss
-Pumping losses
-Rubbing friction loss
Combustion in SI engines
Stages
Effect of engine variables on ignition lag
-fuel
-mixture ratio
-initial p,T
-electrode gap
-turbulence
Effect of engine variables on flame propagation
-F/A ratio
-compression ratio
-intake p,T
-engine load
-turbulence
-engine speed
-engine size
p-theta for different rates of combustion
Abnormal combustion
Detonation/knocking
Effects of detonation
Theories of detonation
Factors affecting detonation
Control of detonation
knock evaluation in cfr engine(Philips knock meter)
Abnormal combustion knock(surface ignition)
-wild ping, rumble etc
CC design principles
CC desings
-T head
-I head
-F head
Combustion in CI engines
Stages
A/F ratio in CI engines
Delay period or ignition lag
Variables affecting delay period
Diesel knock
Methods of controlling diesel knock(reduce delay period)
Methods of generating swirl
M-chamber
Cold starting
SI vs CI engines, comparison
Fuels and additives
Fuel desirable properties
Refining process
Volatility and effect on engine performance
-cold and hot starting
-vapour lock
etc
Knock rating
-HUCR
-octane number
-RON, MON
-PN
Effect of fuel structure on knocking
Diesel fuels
-flash point, fire point, viscosity, cloud point, pour point
Cetane number
Diesel index
Aniline point
API gravity
Additives
-antiknock
Fuels for gast turbines and jet engines
ATF
Alternative fuels
Methanol, Ethanol
Volumetric efficiency
factors affecting
-inlet air temp
-inlet and exhaust pr
-inlet mach number
-piston speed and engine size
-induction heat transfer
-valve timing
Carburetion
-A/F for max power, max sfc
Automotive engine operation F/A ranges
-idling and low loadm cruising, max power
Simple carburettor(no need to look at variants)
Theory and formula for simple carb
Exact analysis, considering compressibility
Electronic fuel injection--features, compare with conv carburetion
Altitude compensation
Diesel injection
Heat release diagram
Types of injection systems(no need for details, only overview)
Numericals on quantity of fuel per cycle, nozzle orifice size
Ignition, Lube system, cooling system
Supercharging
objective, p-v diagram compare
Effect on engine performance
-on power output
-on mechanical efficiency
-on fuel consumption
Gas turbine cycle
p-v and efficiency calcs
Please feel free to give your inputs/corrections/suggestions on any topic or any solved question below. Do quote the Q no. ex 2015A3b20 or topic name while doing so. Cheers!
General
Difference between External combustion engine and Internal combustion engine
Basic engine parts, nomenclature, materials used, dimension terms
Classification of engines
4 stroke and 2 stroke engines, valve timings, differences
Engine testing numericals
ip, bp, n-ith, n-bth, n-m, n-v, isfc, bsfc, F/A, A/F
Balance sheet on minute basis
2015A3b20 Petrol engine, 4S, 9cyl, D=14.5cm, L=18cm, r=7, bp 350kW @ 2000rpm, when mix is 15% weak with 82.5%C ad 14.8% H2, CV=47MJ/kg , vol eff=0.76 at 15degC, 1 bar, (eta-m)=0.9, R=0.287kJ/kgK, to find: (eta-ith)
Ans: Now, bp=350kW so, ip =bp/(eta-m)=350/0.9 =388.9kW
(eta-ith)=ip/(mf x CV) and (eta-v)= ma /( rho x pi D^2 L /4 x N/120 x n)
now that catch in the question is to get air mass rate ma and then A/F, then mf and hence eta-ith
so, ma= (eta-v) x RT/p x pi D^2 L /4 x N/2 x n
ma= 0.76 x 287 (273+15) /10^5 x pi x 0.145^2 x 0.18 /4 x 2000/120 x 9 = 0.28 kg/s
in above, i have used rho =RT/p gas eqn, vol of cyl =pi D^2 L/4, cycles per sec=N/(2x60), n=9 cyls
Now, consider 100kg fuel, mixed in stoichiometric ratio then
(82.5/12)C + (14.8/2)H2 +(aO2 + 79.1a/20.9 N2) -->bCO2 +dO2 + eN2 +fH2O
so, b=6.875, d=0 no excess air, a=d+b+f/2 = 0+6.875+7.4/2=10.575 kmoles(air required for stoichio)
So for 15% weak mix, air required =0.85 x 10.575 kmoles=8.98875 kmoles
so, ma=(ax32 + 79.1a/20.9 x28)= (32 + 79.1/20.9x28)x8.98875=1241.57kg/s when mf=100kg/s
or A/F=ma/mf=12.4157, so for ma=0.28 kg/s, mf=0.28/12.4157=0.02255 kg/s
(eta-ith)=388.9kW/(0.02255 kg/s x 47000 kJ/kg) = 0.367
Emissions related theory and numericals
Apparatus for measuring exhaust emissions
Gasoline engine emission control
Diesel smoke and control
Air standard cycles
Carnot
Stirling 1816
Ericsson
Lenoir
Constant volume or Otto
Diesel cycle
Dual cycle
Atkinson
Joule or Brayton cycle
Fuel air cycles and actual cycles(no numericals from here, don't break your head over them)
Assumptions made in fuel air cycle
Loss due to variation of specific heat on p-v diagram
Effect of disassociation on temperature at different mixture strength, and on power
Effect of variable on p, T in cylinder
1.compression ratio
2.F/A ratio
-on efficiency
-on max power
-on max temp
-on max pr
-on exhaust temp
-on mep
Losses in an actual cycle
-Time losses
-Direct heat losses
-Exhaust blowdown loss
-Pumping losses
-Rubbing friction loss
Combustion in SI engines
Stages
Effect of engine variables on ignition lag
-fuel
-mixture ratio
-initial p,T
-electrode gap
-turbulence
Effect of engine variables on flame propagation
-F/A ratio
-compression ratio
-intake p,T
-engine load
-turbulence
-engine speed
-engine size
p-theta for different rates of combustion
Abnormal combustion
Detonation/knocking
Effects of detonation
Theories of detonation
Factors affecting detonation
Control of detonation
knock evaluation in cfr engine(Philips knock meter)
Abnormal combustion knock(surface ignition)
-wild ping, rumble etc
CC design principles
CC desings
-T head
-I head
-F head
Combustion in CI engines
Stages
A/F ratio in CI engines
Delay period or ignition lag
Variables affecting delay period
Diesel knock
Methods of controlling diesel knock(reduce delay period)
Methods of generating swirl
M-chamber
Cold starting
SI vs CI engines, comparison
Fuels and additives
Fuel desirable properties
Refining process
Volatility and effect on engine performance
-cold and hot starting
-vapour lock
etc
Knock rating
-HUCR
-octane number
-RON, MON
-PN
Effect of fuel structure on knocking
Diesel fuels
-flash point, fire point, viscosity, cloud point, pour point
Cetane number
Diesel index
Aniline point
API gravity
Additives
-antiknock
Fuels for gast turbines and jet engines
ATF
Alternative fuels
Methanol, Ethanol
Volumetric efficiency
factors affecting
-inlet air temp
-inlet and exhaust pr
-inlet mach number
-piston speed and engine size
-induction heat transfer
-valve timing
Carburetion
-A/F for max power, max sfc
Automotive engine operation F/A ranges
-idling and low loadm cruising, max power
Simple carburettor(no need to look at variants)
Theory and formula for simple carb
Exact analysis, considering compressibility
Electronic fuel injection--features, compare with conv carburetion
Altitude compensation
Diesel injection
Heat release diagram
Types of injection systems(no need for details, only overview)
Numericals on quantity of fuel per cycle, nozzle orifice size
Ignition, Lube system, cooling system
Supercharging
objective, p-v diagram compare
Effect on engine performance
-on power output
-on mechanical efficiency
-on fuel consumption
Gas turbine cycle
p-v and efficiency calcs
