Mechanical Engineering - Thermodynamics - Discussion

The correct answer is: cut-off is decreased.

The Diesel cycle and Otto cycle are both idealized thermodynamic cycles used to model internal combustion engines. The main difference between them is the way heat is added to the system.

As the cut-off ratio (the ratio of the volume at the end of combustion to the volume at the beginning of combustion) in a Diesel cycle decreases, the cycle approaches the Otto cycle. This is because a smaller cut-off ratio means that the combustion process is more similar to the constant-volume heat addition process in the Otto cycle.

In contrast, a large cut-off ratio means that the combustion process is more similar to the constant-pressure heat addition process in the Diesel cycle. A cut-off ratio of zero would mean no heat addition and a constant cut-off ratio would not change the fundamental characteristics of the cycle.

I think the right answer is B.

If you all compare both the cycle in one PV diagram. The Otto cycle highest temp meet to diesel cycle highest temp when cut off is zero. So the given answer is right.

When cut-off is zero OR in other words cut-off ratio is one (i.e. When heat is being added at constant volume), diesel cycle approaches to Otto cycle.

The answer is right.

Because here (Cut-off) is mention so, when cut-off will be zero then the efficiency of diesel cycle approaches to the efficiency of otto.

Where CUT-OFF and CUT-OFF RATIO both are different, If cut-off ratio is unity then the efficiency of the diesel cycle will approach to efficiency of otto cycle.

By L-HOSPITAL rule, you can prove, but for cut-off ratio.

Correct, Thanks @Madan.

The answer is right.

Because here (Cut-off) is mention so, when cut-off will be zero then efficiency of diesel cycle approaches to efficiency of otto.

Mind it, CUT-OFF and CUT-OFF RATIO both are different, If cut-off ratio is unity then efficiency of diesel cycle will approaches to efficiency of otto cycle.

By L-HOSPITAL rule, you can prove, but for cut-off ratio.

Answer is C.

Because of the value of the cut-off ratio is ZERO put the value in equation of diesel cycle then both are equal.

The question should be a Dual cycle, not the diesel cycle.

Because in the dual cycle there are two heat addition one at constant volume and other at constant pressure known as cut off and when this cutoff is made zero the cycle becomes Otto cycle.

When the cutoff ratio ρ=1 then the efficiency of 'DUAL' cycle becomes efficiency of the Otto cycle.

And when ρ=0 then the efficiency of 'diesel' cycle becomes efficiency of the Otto cycle by L hospital's rule.