QUESTIONS• What is the advantages and Disadvantages of four stock
engines?• What is the advantages and Disadvantages of two stock
engines?• What is the advantages and Disadvantages of Petrol engines?• What is the advantages and Disadvantages of Diesel engines?• What is the advantages and Disadvantages of Wankel stock
engines?• Compare 4 - stroke & 2 - stroke Engine?
QUESTIONS• Describe working principles of Wankel engines?• Numerate performance parameters of the I.C. engines?
Ideal cycles are simplified
Ideal Cycles
• More realistic than Carnot cycle.• Internally reversible but not totally.• Idealizations:
– No friction– Expansions and compressions – quasi-equilibrium– Heat transfer is negligible
Different Processes
Isobaric Isometric
Adiabatic ΔT ≠ 0 but Q = 0
IsothermalΔT = 0 but Q ≠ 0
CyclicIf clockwise – heat engine
If counterclockwise – heat pump
Area inside the cycle represents net work out for TS or PV diagrams.
Otto Cycle, ideal for spark ignition engines
TS plot of the Otto Cycle
Efficiency vs Compression Ratio
Higher ratios produceautoignition andknocking
Efficiency vs ratio of specific heats
Air
Combustionmixture
He
The Ideal Otto Cycle