Which one of the following correctly represents the variation of thermal efficiency (y-axis) with mixture strength (x-axis)?
Option (A)
Option (B)
Correct Option:
Question Solution:
As the mixture is made lean (less fuel) the temperature rise due to combustion will be lowered as a result of reduced energy input per unit mass of mixture. This will result in lower specific heat. Further it will lower the losses due to dissociation and variation in specific heat. The efficiency is therefore higher [and, in fact, approaches the air-cycle efficiency as the fuel-air ratio is reduced.]