In an air standard Otto cycle, the compression ratio is 7. Find the cycle efficiency

Explanation

Concept: The efficiency of an air standard Otto cycle is given by - where r= compression ratio, γ = ratio of specific heat C p/C v⇒ 1.4 for ideal gas i.e. Air The efficiency of the air standard Otto cycle is a function of the compression ratio r only. Range r k= 6 - 10 Calculation: Given: r k= 7, γ = 1.4 ⇒ 54.08 % ≈ 54 % Otto Cycle Air standard cycle for spark ignition (SI) engine. Piston executes four complete strokes within the cylinder, and the crankshaft completes two revolutions for each thermodynamic cycle. P-V Diagram & T-S Diagram: η ​ = Otto 1 − ​ rγ−1 1 ∵η = Otto 1 − ​ rγ−1 1 ⇒1 − ​ 70.4 1 Process 1-2 (Compression) - Reversible adiabatic compression Process 2-3 (Combustion) - Constant volume heat addition. Q 1= Q 2-3 = mc v(T 3– T 2) Process 3-4 (Expansion) - Reversible adiabatic expansion. Process 4-1 (Exhaust) - Constant volume heat rejection. Q 2= Q 4-1 = mc v(T 4– T 1)