CPD in GT

C

Thread Starter

calvein

Why does the compressor discharge air pressure increase with an increase in load over the same IGV angle range when the compressor is basically rotating at the same speed?
 
Good question.

What happens to the cylinder pressure when you put more fuel in a cylinder and ignite it?

Right; the pressure increases.

In a gas turbine the same thing happens, it's just that the increased pressure in the combustors means the "back-pressure" on the axial compressor increases. When the IGVs are full open (or are being held at a constant angle), you are correct that the air flow through the machine isn't changing if the fuel flow-rate is being increased. So, the compressor has to work a little harder to get the same amount of air into the combustors.

Axial compressors are interesting machines.

I believe the increased fuel pressure being allied to the nozzles/combustors as well as the increased mass flow through the machine adds the increased CPD.

Finally, have a look at a plot of CPD when a gas turbine trips. It decreases very dramatically as soon as fuel is cut off. In fact some gas turbine manufacturers are testing turbines without flame detectors, using CPD and exhaust temperature to determine the presence and/or loss of flame.
 
>Very well explained CSA,
>
>Thank you
>G.Rajesh

I come from a process industry where our gas turbines are variable speed, not fixed to a grid like in power generation. If more fuel is required, the turbine speeds up and there is a corresponding increase in CDP. Just offering this as a different way to look at it.
 
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