Question

An ideal air standard Otto cycle has a compression ratio of 8.5. If the ratio of the specific heats of air (Y) is 1.4, what is the thermal efficiency (in percentage) of the Otto cyde? (a) 57.5 (b) 45.7 (c) 52.5 (d) 95

Answer 1

Given info : An ideal air standard Otto cycle has compression ratio is 8.5. if the ratio of the specific heats of air (γ) is 1.4,

To find : the percentage thermal efficiency of Otto cycle is ...

Solution : using formula, $\eta=\left(1-\frac{1}{r^{\gamma-1}}\right)\times100$

Here, r is the compression ratio and γ is the specific heat ratio (i.e., Cp/Cv) and η is percentage efficiency of Otto cycle.

then, r = 8.5, γ = 1.4

So, η = {1 - 1/8.5^(1.4-1)} × 100

= {1 - 1/(8.5)^(0.4)} × 100

= (1 - 1/2.35) × 100

= (1 - 0.425) × 100

= 57.5 %

Therefore the percentage thermal efficiency of Otto cycle is 57.5 %