Question 40Motor Plants - Assistant Engineer

The correct answer is B) mechanical efficiency. The mechanical efficiency of a diesel engine is the ratio of the brake horsepower (the power available at the engine's output shaft) to the indicated horsepower (the power generated within the engine's cylinders). This ratio represents the proportion of the engine's indicated power that is actually delivered as useful work, accounting for mechanical losses such as friction and drag within the engine. The other options are incorrect because: A) Thermal efficiency is the ratio of the engine's useful work output to the total energy input. C) Brake thermal efficiency is the ratio of the engine's brake horsepower to the total energy input. D) Volumetric efficiency is the ratio of the actual volume of air/fuel mixture drawn into the engine's cylinders to the theoretical maximum volume.