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Gas Turbine Driven Centrifugal Compressor Effciency

compressor centrifugal effciency gas turbine natural gas compression adiabatic polytropic

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#1 ADITYA.DUBEY

ADITYA.DUBEY

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Posted 31 December 2016 - 02:01 AM

Dear Forum Members

 

A very happy New year to you all.

 

I'm planning to calculate gas turbine driven  compressor  efficiency.

 

P1=7 bar , T1 = 30 Deg C

P2=22 Bar , T2 =130 Deg C

 

 

Below are my queries -

 

1) Which inlet suction flow to be considered for calculation purpose??

  Flow before Anti-surge line(A) or flow after anti-surge line( B ) .

How to consider Anti-surge valve opening effect in efficiency calculation??

Will its effect only be on fuel gas consumption of Gas turbine??

 

2) Adiabatic index for natural gas(Mol Wt =17.2),I am taking 1.3.

 

3) Polytropic index calculation will be from the formula

 

P1/P2 = (T2/T1)^(n/n-1)

 

4) I 'm calculating Efficiency by below formula 

 

= (Work done by compressor) / (Fuel gas consumption Energy)

 

 

Any addition/suggestion will be most welcome.

 

Regards

Aditya

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Edited by ADITYA.DUBEY, 31 December 2016 - 02:01 AM.


#2 Bobby Strain

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Posted 31 December 2016 - 10:24 AM

Compressor efficiency is determined by temperature and pressure only,as you show incorrectly in (3). Your formula (4) gives overall efficiency of turbine and compressor combined. So you should search for compressor and turbine thermodynamics, work and efficiency.

 

Bobby



#3 ADITYA.DUBEY

ADITYA.DUBEY

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Posted 04 January 2017 - 11:30 AM

Dear Sir

 

(A)

You mean to say ASV opening or flow rate through compressor does not affect compressor efficiency.

But during work done calculation under polytropic process by compressor will be

 

W= (no. of Moles)*R*(T2 - T1)/(1-n)

 

where T2 and T1 are discharge and suction temperature.

n = polytropic index

R= gas constant

 

Which includes no. of Moles i.e. the flow rate through the compressor.

Please clear my doubt.

 

( B )

Formula given in (3) is for calculation of Polytropic index(n).

Its not for polytropic efficiency

 

( C )

Yes I want to calculate overall efficiency of compressor and turbine together.

 

Regards

Aditya


Edited by ADITYA.DUBEY, 04 January 2017 - 11:31 AM.


#4 Bobby Strain

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Posted 04 January 2017 - 03:17 PM

Td = Ts (Pd/Ps) (n-1)/n

 

This is where you start to determine n. Rearrange the equation to suit your needs. Note that this is not as you presented in (3).

 

Bobby






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