Mechanical Engineering - Thermodynamics - Discussion
Discussion Forum : Thermodynamics - Section 1 (Q.No. 17)
17.
The efficiency of Diesel cycle approaches to Otto cycle efficiency when
Discussion:
41 comments Page 2 of 5.
Vishal Joshi said:
1 decade ago
The efficiency of Otto cycle is 1-(1/r^(Y-1)) Y = Gamma.
And that of Diesel cycle is 1-[(1/r^(Y-1))[(ρ^y-1)/y(ρ-1)] ρ=rho= cut-off. Here if ρ=0, then Efficiency of Diesel cycle becomes 1-(1/Y(r^(Y-1))).
So we can say the efficiency of Diesel cycle approaches to that of Otto Cycle.
And that of Diesel cycle is 1-[(1/r^(Y-1))[(ρ^y-1)/y(ρ-1)] ρ=rho= cut-off. Here if ρ=0, then Efficiency of Diesel cycle becomes 1-(1/Y(r^(Y-1))).
So we can say the efficiency of Diesel cycle approaches to that of Otto Cycle.
Rajat said:
8 years ago
As an diesel cycle the cut off ration is the ratio between V3/V2.
V3 - Fuel Injection Into the Cylinder Stop While Power Stroke.
V2 - Fuel Injection Into the Cylinder Start While Power Stroke.
Those V3 & V2 are Smaller than The V1(Cylinder Volume).
V3 - Fuel Injection Into the Cylinder Stop While Power Stroke.
V2 - Fuel Injection Into the Cylinder Start While Power Stroke.
Those V3 & V2 are Smaller than The V1(Cylinder Volume).
Aniruddh said:
7 years ago
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.
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.
Brajesh said:
7 years ago
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.
And when ρ=0 then the efficiency of 'diesel' cycle becomes efficiency of the Otto cycle by L hospital's rule.
Srikanth said:
8 years ago
In the options, they said cutoff(vol after combustion-vol before) not cutoff ratio (vol after combustion/vol before combustion).
Therefore as cutoff reaches zero it becomes constant volume process.
Therefore as cutoff reaches zero it becomes constant volume process.
Chetan Hindwal said:
7 years ago
The Efficiency of diesel I think much greater then petrol so here we can say choose the value of cut off high as it decreases the efficiency of diesel which approaches to petrol. Am I right?
DEVESH CHAUDHARY said:
9 years ago
When cut off ratio is 1 then the efficiency of diesel cycle is maximum which is equal to the efficiency of the otto cycle. So right answer should be when cut off ratio is 1.
Trulli said:
5 years ago
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.
(1)
Jithin said:
5 years ago
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.
(1)
Islam gamal said:
7 years ago
The efficiency will be lower if cutoff ratio is higher because the piston has already moved far down while the heat is still being added.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers