Subtopic: Calculation of power, torque, fuel consumption, heat load and power losses
Question Statement:
In the Willans line method for estimating the mechanical friction power of a compression-ignition engine operating at constant speed:
Options:
(A) A plot of gross fuel consumption rate versus brake power output is linearly extrapolated backward to zero fuel consumption; the negative power intercept represents engine friction power
(B) Fuel injection timing is retarded until the engine stalls
(C) Cylinders are cut off one by one using a shorting bar
(D) The engine is driven with an external electric dynamometer with the cylinder head removed
Answer Key:
A
Step-by-Step Solution & Explanation
In a compression ignition engine running at governed constant speed, gross fuel consumption plotted against brake power yields an approximately straight line (Willans line). Extrapolating this line backward to the zero fuel consumption axis gives a negative power intercept that represents the total engine friction and pumping losses ($FP$).