Question

The air standard efficiency of the Diesel cycle reaches that of the Otto cycle when the following condition is satisfied:

• A. increased cut-off ratio
• B. decreased cut-off ratio
• C. constant cut-off ratio
• D. zero cut-off ratio

Hint:

When the cut-off ratio in a Diesel engine approaches zero, the cycle behaves more like the Otto cycle, increasing efficiency.

Answer 1

The Correct Option is D

Step 1: Definition of cut-off ratio in Diesel cycle.
The cut-off ratio refers to the point at which fuel injection stops in the Diesel cycle. It is a parameter that controls the end of combustion in the Diesel cycle.
Step 2: Efficiency comparison of Diesel and Otto cycles.
The Otto cycle achieves higher efficiency due to its constant-volume combustion process. The Diesel cycle, in contrast, operates at constant pressure. By decreasing the cut-off ratio, the Diesel cycle starts resembling the Otto cycle, and as the ratio approaches zero, the Diesel cycle becomes more efficient, equaling the efficiency of the Otto cycle.