Question

The Otto engine consumes 9 liters of petrol per hour and develops 30 kW. The specific gravity of petrol is 0.8 and its calorific value is 45000 kJ/kg. What is the indicated thermal efficiency of the engine?

(a) 33.33%

(b) 25%

(c) 30%

(d) 32%

The question was posed to me in an interview for job.

My question comes from Performance Parameters and Characteristics in chapter Automotive Electronics, Engine Performance Parameter & Testing of Automobile Engines of Automobile Engineering

Answer 1

Right option is (d) 32%

The explanation: ηith = heat equivalent of indicated power / heat input = (30 * 60 * 60 * 100) / (9*10^-3*800)*45000 = 33.33%.