Gas Turbine Temperatures

Gas turbines have thermal sensing probes all over for direct readings of temperature. These readings will vary based on fuel used (gas turbines can burn propane, natural gas, hydrogen, number 2 fuel oil, gasified coal, gasified garbage, and any blend of any of these) and site temperature.

Gas turbines also have various non-fuel injections as well to help complicate the calculations. Steam injection, water injection in the combustor, inlet cooling, and water injection at the compressor inlet. All of which change various bulk flow temperatures and the power output.

Actually i want to findout the temperature using heat balance.

Is there any relationship between exhaust temperatures and combustion temperatures?

Yes there is. Engineers place EGT/TOT probes on service engines to get an average temperture. It's different for each model eng. due to the distance from the really hot parts and the temperture probes. After much testing they learn that exceeding a certain EGT / TOT and something has probaly been melted. They get pretty good info on test stands, but, flying is where they dicide where to put the colored marks on the instruments.

The relation does exists. the turbine design is based on this relationship.

The combustion temperature is to be the highest by achieving complete combustion.

the inter passes are designed to utilise the maximum heat to convert into mechanical energy. the lower the exhaust temperature better the performance.

The heat recovery is done in to exhaust section to increase the inlet air temperature for combustion.

Your use of the "etc" suggests that you just might have more data. That is good because the whole point of designing or examining a gas turbine is to know exactly what is going on inside what you define as a gas turbine. If you have all the temperature readings for all the points on all the components, with pressures, velocities, gas compositions, material compositions of all components, "etc" , as well as similar data for the environment surrounding the gas turbine, you can use approximations based on assumptions, both theoretical and experimental, to guess at what you are asking. You do not give any information about the precision desired in your requested temperatures, so I guess the best answer is yes, or no, depending on required precision. If this is a theoretical question, the answer may be different. If it is a commercially available gas turbine, you can request a response from the manufacturer

"Gas turbine temperature calculations." What you want to calculate? You say "I have the outlet temperatures, inlet temperatures, gas compression ratio's,output power,GCV etc"

"compressor outlet temperature & combustion chamber temp?" compressor outlet temperature will depend on compressor design and pressure ratio. Combustion chamber temp shall be higher than turbine inlet temp. How much higher depend on so many factors.

Generaly speaking, if you have the inlet/outlet conditions and the process (type of gas, cp) then ideal conditions can be calculated by using thermodynimics energy balance.

In order to have a more realistic calculation, we need to know what kind of gas turbine you are using, normally you have the combustion to take place within the main air inlet and compressor on the shaft (as with airplanes jet turbines) but there are special purpose turbines in which the combustion does not mix with the main air inlet and heat transfer occurs by conduction of the container wall. If you had a diagram would be very helpful.

Hope you find this helpful, if you have more details I could help you with the heat calculations

Thanks everybody for replying.

The turbine is solar Titan 13O. The parameters i want to figure out is

1) How the exhaust temperatures will vary depending on the variation in inlet temperatures ?

2) If the inlet temperature increases how the airflow rate varies ?

What gas this Gas turbine handles? Is it Air? Only generalised answer I can give for your questions.

1) How the exhaust temperatures will vary depending on the variation in inlet temperatures ? Considering inlet and outlet pressure unchanged, drop in inlet temperature will reduce outlet temperature (not in same proportion) as well as enthalpy drop (refer thermodynamic chart for the gas) so work output will be reduced. For increase vise-versa.

2) If the inlet temperature increases how the airflow rate varies ? Considering again inlet air pressure unchanged, the inlet air temperature increases will decrease the air mass flow rate. Volume flow rate at inlet condition will be the same, the decrease will be on volume flow rate at NTP or mass flow rate due to decrease in density.

Have you contacted the Manufacture (Caterpillar) for their performance data sheets? Every gas turbine I've worked on, comes with extensive performance data.

During manufacturing R&D research, they run various parameters,usually to extremes, then plot/graph their findings, then program the governor's to compensate for varying parameters and prevent self-destruction.

This is a very expensive piece of equipment your wanting to play with. So, if It's Not Broken, Do Not Fix It! DJ

If you haven't studied it yet, gas turbines use the Brayton cycle. The following pdf has a pretty good description and various equations that apply.

http://web.me.unr.edu/me372/Spring2001/Brayton%20Cycle.pdf

I'd suggest getting comfortable analyzing a given situation and then once you grasp how everything relates, look back to the equations and start varying whatever parameter you're interested in to see the effects.

My dear friend i think there is a mistake in the thermal efficiency formula in the link which you have send me.

Instead of (T3-T2)/(T4-T1) it should be (T4-T1)/(T3-T2).

Thanks every body for giving good advises....

Hey Pritam that was a cool reply from you, which i was waiting."The mass flow rate decreases with increase in inlet temperatures". which is in line with my calculations.

Thanks, but I got 2 OT's for my reply, may be from previous commenters. I have studied the link at #11 suggested by 'ChovoticIntellect'. It's informative. The error you have pointed out at#14 is only typographical, as it is corrected at very next step.

Also as suggested by 'dj95401' at #12, study the performance data sheets from OEM, your many doubts will be cleared.

This doesn't address your original question, but I think it is worth mentioning since your name is boilertrainee and it wouldn't be a quantum leap to think you probably work with one or more GTs. There is another important thing to know and often get lost in the academic understanding. Simply put, these are mass flow machines, so the more fluid you can cram in the inlet, the more power you're going to get out (and quite often improve the heat rate as well). Take note, all the equations are in "specific" quantities for ease of analysis.

Thanks C.I for valuable comments...

All points noted.