Otto cycle efficiency for a given compression ratio: compute the thermal efficiency. Given: Compression ratio r = 5.5 for an ideal Otto cycle with γ ≈ 1.4. Find the approximate thermal efficiency (percentage).

Given data

• Compression ratio r = 5.5
• Specific heat ratio γ ≈ 1.4 (air-standard)

Formulaη_Otto = 1 − 1/r^(γ−1)

Step-by-step calculationr^(γ−1) = 5.5^0.4 ≈ 1.977η = 1 − 1/1.977 ≈ 1 − 0.5056 ≈ 0.494η ≈ 49.4% ≈ 50%

Final Answer50%.