Question

Compared to the Otto cycle for the same compression ratio, the diesel cycle efficiency is:

• A. Lower
• B. Higher
• C. Equal
• D. Cannot be determined

Hint:

The Diesel cycle typically operates at higher compression ratios, but the Otto cycle generally achieves higher thermal efficiency due to the nature of their combustion processes.

Answer 1

The Correct Option is A

In general, the efficiency of a diesel engine cycle is lower than that of an Otto cycle when the same compression ratio is used. This is due to the fact that the Diesel cycle operates at a higher compression ratio, which leads to higher in-cylinder temperatures and pressures. However, the Diesel cycle typically operates with higher air-fuel ratios that lower its overall efficiency when compared to the Otto cycle.
- Lower is correct because, at the same compression ratio, the Diesel cycle will have lower thermal efficiency than the Otto cycle due to differences in their operating conditions and fuel characteristics.
- Higher is incorrect, as it is the Otto cycle that tends to show higher efficiency at similar compression ratios.
- Equal is not true as the Diesel cycle efficiency is generally not equal to the Otto cycle efficiency for the same compression ratio.
- Cannot be determined is incorrect because the relationship between Diesel and Otto cycle efficiency is well known, and it can be determined that the Diesel cycle has lower efficiency at the same compression ratio.
Therefore, the Diesel cycle efficiency is lower than the Otto cycle for the same compression ratio.