Mechanical Engineering - Thermodynamics - Discussion

3. 

The efficiency and work ratio of a simple gas turbine cycle are

[A]. low
[B]. very low
[C]. high
[D]. very high

Answer: Option B

Explanation:

No answer description available for this question.

Manigandan said: (May 4, 2013)  
70% of the power produced by the turbine is used to run the compressor itself.

Gokul said: (Jun 3, 2013)  
Because there will be more availability in the exit of the turbine. That's why rankine cycle is used combined with gas power plant.

Jogi Pal said: (Sep 29, 2013)  
Work ratio = (turbine work/net work).

Turbine is used to run the compressor itself.

So, work ratio is very low.

Digvijay Singh said: (Oct 26, 2013)  
Work ratio is = work net/turbine work.

Low because lost of work used to drive compressor.

Shyam said: (Dec 13, 2013)  
Compressor work is nearly about 40-60% of total work. So work done per specific fuel consumption is less compered to other.

Sudhir said: (Jan 17, 2014)  
Because work ratio lies between 0 $ 1.

Dheeraj said: (Mar 23, 2014)  
But it is low how we can say it is very low ?

Anshu Maan Mishra said: (Mar 24, 2014)  
The ratio of the actual work output of the turbine to the work output that would be achieved if the process between the inlet state and the exit state was isentropic.

Awinash Kumar said: (Apr 20, 2014)  
Mechanical efficiency of gas turbine is about 95%. It is not clear in question although thermal efficiency is about 15-20%.

Rajkumar said: (Jul 10, 2014)  
Since the specific volume (reciprocal of density) of air is high, the compression of air requires more work. Hence, major fraction of the work developed by the turbine is utilized in driving the compressor. Therefore, the efficiency of the simple gas turbine plant is too low.

Devendra Janjawat said: (Aug 18, 2014)  
Work ratio = positive work /net work.
Positive work = turbine work.

Sudhir Deshpande said: (Oct 13, 2014)  
Work efficiency increases by regeneration in simple gas turbine otherwise it is minimum.

Aqib Raja Khan said: (Nov 22, 2014)  
It is used for safety against pressure in excess of the rated pressure.

John said: (Dec 10, 2014)  
Efficiency = Output/input then,

Work Ratio = Net work of the turbine/Work of the turbine.

Dhms said: (Dec 12, 2014)  
The efficiency is very low because, turbine is rotating device due to that it haves high losses.

Sumit said: (Dec 21, 2014)  
Due to compressor EFF is less.

Abhay Singh said: (Dec 31, 2014)  
Gas turbine's efficiency and work is minimum because less of friction but turbine fan and air.

Biswaranjan Biswal said: (Feb 1, 2015)  
It is the ratio of net work/turbine work. Net work equal to turbine work-comp work.

Kunwar Singh said: (Mar 28, 2015)  
Turbine is mostly energy waste in rotating compressor.

Dk Singhgupta said: (May 28, 2015)  
We all know that work ratio-turbine work /net work that means turbine work means positive work so the answer is low but how the answer is very low.

Krishna said: (Oct 31, 2015)  
Nothing understood. Post the explanations clearly.

Soham Mitra said: (Dec 7, 2015)  
Rankine cycle used in thermal power plants deals on heating up water in constant pressure while changing its phase. The process will has greater thermal efficiency compared to any other cycles. Otto cycle can't be used because heat supplied to the system is in constant volume process, not allowing steam to expand properly.

If Otto cycle forced to used, the pressure will be too high for any material (vessel) to withstand. Diesel also can't be used, because while heat supplied to the system, the fluid deliver work to the surrounding. This not applicable because the work should be extracted by steam turbine.

Yogesh Gayake said: (Jan 20, 2016)  
But my question is that turbine is used to rotate the generator for generating the electricity & its rotate with the help of steam pressure. Then how we can calculate its efficiency & work ratio. But still we assure that the 70% of power from turbine is used to run the compressor itself. So it's correct but, how we can say its very low. Please suggest answer.

Chauhan Hardik N. said: (Mar 29, 2016)  
I think that, since the specific volume (reciprocal of density) of air is high, the compression of air requires more work.

Hence, the major fraction of the work developed by the turbine is utilized in driving the compressor.

Therefore, the efficiency of the simple gas turbine plant is too low.

Pavankumar Jadekar said: (May 30, 2016)  
The fuel consumption should be more in this.

Hemesh Kumar said: (Aug 12, 2016)  
Since efficiency is a function of pressure ratio in simple gas turbine (braton, joule) cycle.

Hemesh Kumar said: (Aug 12, 2016)  
Because, efficiency = 1- (heat reject / heat supply) in case of simple gas turbine.

Sa0 said: (Oct 23, 2016)  
Work ratio is just the fraction or percentage of the work that the turbine produces that is consumed by the pump.

Majd-Amer said: (Mar 14, 2018)  
Half and more the power produced by the turbine is used to complete motion in the compressor.

Vishal Kadam said: (Mar 23, 2018)  
Maximum power turbine is consumed by compressor itself and also air is working Media so max Power loss.

Bms said: (Sep 1, 2018)  
How to differentiate between low and very low? Please explain it to know.

Salman said: (Jan 31, 2019)  
@Sumit.

What is means by EFF?

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