The thermal efficiency of a diesel engine is approximately

🔑 Key Points
[Heading 2]:
→ Explanation: Diesel engines are also known as constant-pressure engines because the addition of heat takes place at constant pressure.

[Sub-heading 2]:
➡️ The thermal efficiency of diesel engines:
→ η=1−1/rγ−1.(rcγ−1)/γ(rc−1)
→ where, r = compression ratio, rc = cut-off ratio, and γ is the ratio of specific heat.
→ Diesel engines are high-capacity engines because of their high compression ratio.
→ The absence of a throttle valve leads to low specific fuel consumption, thus making diesel engines economical.

📌 Important Points
→ The theoretical efficiency of a diesel engine is up to 75%. But in practice, the diesel efficiency is in the range of 30% to 50%.
→ Modern passenger cars' effective efficiency is up to 43%, whereas engines in trucks and buses operating on diesel engines can achieve peak efficiency of about 45%.
→ The diesel engine efficiency will be highest up to 55% achieved in a large two-stroke watercraft diesel engine.