Question

The ratio of the heat equivalent to one kW hour to the heat in fuel per B.P. hour is termed as brake thermal efficiency.

(a) True

(b) False

I have been asked this question during a job interview.

My doubt stems from Engine Efficiencies in division Measurements and Testing/Performance Parameters and Characteristics of IC Engine

Answer 1

The correct answer is:

(c) four stroke C.I. engine, two stroke S.I. engine, four stroke S.I. engine

This sequence is based on the general efficiency characteristics of these engine types:

- Four-stroke C.I. (Compression Ignition) engines typically have the highest brake thermal efficiency due to their higher compression ratio and better fuel efficiency, especially when compared to spark-ignition engines.

  

- Two-stroke S.I. (Spark Ignition) engines generally have lower brake thermal efficiency because of incomplete combustion and greater energy loss due to the simpler design and shorter cycle.

- Four-stroke S.I. engines have the lowest thermal efficiency among the three because of their lower compression ratio compared to C.I. engines, which limits their ability to convert fuel energy into work efficiently.