Mechanical Engineering - Thermodynamics - Discussion

Discussion Forum : Thermodynamics - Section 2 (Q.No. 36)
36.
Otto cycle efficiency is higher than Diesel cycle efficiency for the same compression ratio and heat input because in Otto cycle
combustion is at constant volume
expansion and compression are isentropic
maximum temperature is higher
heat rejection is lower
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
14 comments Page 2 of 2.

Saurabh said:   7 years ago
I agree @Prince. If we plot PV diagram- we see for same compression ratio the maximum temperature achieved by the Otto cycle is higher than that of diesel cycle. Also, there is no such difference can be determined unless it is not given in case of cont Volume heat rejection.

Dhrupat said:   7 years ago
@Prince.

As we know about petrol. It has a lower flash point, so there is a low temperature at heat addition time. The given answer is correct.

Prakash said:   6 years ago
Condition is given the same compression ratio and heat input so the comparison would be done on Q2 i.e. Heat rejection. Lower Q2 means higher efficiency. Q2 Otto is less than that of diesel so efficiency of Otto is high. Option D is correct.

Vinod said:   4 years ago
@Prakash.

I agree with your point and D is the Correct answer.


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