8 replies to this topic

[Ajane]

Hi,
I'm trying to study the effect of ambient air temperature on gas turbine. It is known that as air temp rise, turbine power output is reduced. I would like to know how to simulate this in HYSYS. I tried to use a conversion rxtr for the combustion of fuel/air. However with steady-state simulation, I could not vary the ambient air temperature and find the corresponding duty. The intention was the energy from turbine will power the compressors used in a refrigeration of LNG process. Appreciate your advise and tips!

Regards,
Jane

[Ajane]

Just to share my findings,
the power output increases linearly due to the specified 75% adiabatic efficiency on the gas turbine (simulated as an expander) and under steady-state simulation. In actual case, efficiency changes as gas temperature changes, thus, the effect on ambient air temperature change can only be evaluated in HYSYS or other programs with the efficiency curve entered in the expander module.

Then again, such performance characteristics (for GE turbines) are available in the internet
<http://www.gepower.c...s/ger3567h.pdf>

Cheers,
Jane

[engware]

Hi there:

Here are a few plots for the Carnot Cycle indicating an impact of the ambient temperature of the cycle efficiency.

I am not trying to be smart, just trying to show the outcome until you get HYSYS up and running.

Sometimes, simple stuff is not so easy to implement by using sophisticated software and tools.

As you can notice, I already have available a few plots on an interesting subject matter -- why not share it with other fellow engineers who are interested in the same subject matter.

I do hope that you will find my input acceptable ...

Thanks,

Gordan

[mzulu]

Hi Jane,

I just want to find out if you were finally successful in trying to sudy the effect of ambient temperature on gas turbine. I'm currently working on the same subject..., and I've completed the HYSYS simulation, and I've also set up a thermodynamic model using visual basic to model a gas turbine.

We can share the learning and experience if you don't mind...

Regards
<mzulu>

[engware]

To All:

Here is a URL that might help you out with your calculations:
http://engware.i-dentity.com/calc3.htm

Thanks,

Gordan

[Padmakar Katre]

Dear,
Increase in air temperature will increase the power output from the Gas Turbine. Actually I don't remeber the actual figure but I have read it in the Gas Turbine Handbook. You can configure the Gas Turbine with the As Built Approach in Hysys. The only problem is Hysys doesn't have axial compressor option which you could manage to put number of compressors in series with the compression ratio of say 1.1:1 to 1.2:1 with the 95% adiabatic efficiency specified. The air outlet temperature is approx 450 C for air at 1 atm to 25 bar pressure after 12th stage outlet. You put mixer and mix the gas and air and send it to the Gibb's Reactor(use this option as you need not configure the reactions in your reactions tab of the simulation basis manager). The outlet vapor stream ypu could connect to the turbine inlet and see the power given by the turbine. The point to be noted here is the air flow you have to adjust based on either the inlet temperature of the turbine of the flue gas temperature. Turbine temperature you can keep say around 1100 to 1350 C or the turbine outlet flue gas temperature as 500-650 C. You can choose any one out of these two options to adjust the air flow.
Your air flow will be much higher. As in case of Gas Turbines the most of the air is used as coolent and lesser for combustion. Any doubts on this you are welcome. I am sure I could help on this as I have done one project starting from prefeasibility to the commission of a gas turbine(GE Machine) for 30 MW power generation.
Don't forget to calculate the efficiency of the gas turbine. It comes around 55-60% if you have a option of HRSG.

Here is a picture from a GE gas turbine data analysis system, I hope it may help.



More pictures can be found at http://www.leiosoft....reen_en_win.htm

[JoeWong]

Increase in air temperature will increase the power output from the Gas Turbine...

Is this air temperature or flue gas temperature ?

...The air outlet temperature is approx 450 C for air at 1 atm to 25 bar pressure after 12th stage outlet...

Is this air temperature or flue gas temperature ? Air pressure upto 25 bar ?


I am sorry. I just can't follow.

[Padmakar Katre]

Increase in air temperature will increase the power output from the Gas Turbine...

Is this air temperature or flue gas temperature ?

...The air outlet temperature is approx 450 C for air at 1 atm to 25 bar pressure after 12th stage outlet...

Is this air temperature or flue gas temperature ? Air pressure upto 25 bar ?


I am sorry. I just can't follow.

Dear Joe,
Both are air temperatures which is the outlet tempearature of the last stage of the air compressor. Gas Turbine inlet temperature (i.e. Combustor outlet) is say 1100 - 1700 C (in some gas tubines I have seen as high as 2100 C) and the gas turbine outlet temp is as max as 650-700 C depending on the number of turbine stages and the flue gas heat recovery system. I hope this could clear your doubt. Please let me know if any doubt if it still persist.