gas turbine project

[aukap]

so i went to my professor with the presentation on a turbo based engine and he asked me what exactly i wanted to do after fabricating the engine,what my goal was. I was wondering if the turbocharger based engine could be used with bio gas , but i was concerned about it reaching self sustainability considering a low fuel pressure unlike an LPG cylinder.

[racket]

Yep , you'll need fuel pressure above compressor discharge pressure ( P2) , it need not be a lot greater than P2 , just a couple of psi extra at idle and a bit more at higher P2s.

[aukap]

before doing fabrication of any sort my professor wanted me to simulate the combustion on ansys. i am sharing the results of the simulation here. Combustion fuel used was Propane.

[aukap]

[aukap]

This combustor geometry has been successfully used by some fellow users in this forum as i have seen, and moreover the geometry is designed totally according to jetspecs, air inlet near the turbine end, NO TANGENTIAL FEED, smooth transition(as you can see) into the turbine.

The temperatures at the turbine inlet came out to be very high nearly 1500-1600 K whereas in real world they come(as with the fellow users) some 1000-1100K and in simulation it was showing quite an amount of flame burning after the tertiary zone.

The parameters i used were:-

ZONE                                              BOUNDARY CONDITION 

Compressor feed                              Mass inlet(mass flow 0.3 Kg/s, pressure 2 bar, temperature 98 degrees celsius)

Turbine inlet(combustor outlet)           Pressure outlet(pressure 2 bar)

Fuel inlet                                        Mass inlet( Stoichometric ratio x mass inlet)


Model used K-epsilon with energy equation.


Anyone seeing this post if knows anything about CFD then please share if i am doing wrong anywhere due to which my turbine inlet temperatures are coming so high.



Aukap

[rythmnbls]

I've never used Fluent, but I have played around a bit with OpenFOAM for some airfoil simulations.

What velocity did you use for the airflow ? typically it should around 0.1 to 0.2 Mach. Any higher and you usually get losses.

Regards,

Steve.

[finiteparts]

Aukap,

Did you mean to have the inlet and outlet pressures the same (2 Bar)? Looking at you last figure showing contours of static pressure, there doesn't appear to be much happening, I would expect more static pressure variation through the combustor.

Typically a good target for pressure drop through the combustor is around 4-5%. Lots of pressure drop across the liner is great for turbulent mixing in the combustor, but bad for the cycle efficiency. Too little pressure drop across the combustor liner and you get low mixing and poor combustion.

I agree with your choice of boundary conditions, except for the pressures being equal at the inlet and outlet. That is how I would approach setting the boundary conditions...mass flow on inlet and pressure on outlet. I would tend to disagree with Steve's statement to impose velocities as a boundary condition, there is too much uncertainty selecting an average velocity across the inlet plane...depending on the flow regime, (laminar, transitional or fully turbulent), you usually have strong cross-stream velocity gradients that make selecting a representational cross-sectional velocity very difficult.

Good luck!

Chris

[rythmnbls]

I stand corrected I'll have to dig into the OpenFoam combustion tutorials and brush up a bit.

Regards,

Steve.

[gtbph]

Hello everybody,

I'm new here and I'll make an "official" first post soon .
Aukap, I think the reason for the high temperatures is too much fuel.

Mar 28, 2015 5:15:05 GMT -5 aukap said:

Fuel inlet                                        Mass inlet( Stoichometric ratio x mass inlet)

Propane has a stoichiometric ratio of about 16:1, but gas turbines usually don't run at that ratio, they use much less fuel/more air. If you try a ratio of about 60:1 I think the temperatures will be normal.

Regards, Alain

[aukap]

So the project has officially started....starting a new build thread in DIY engines sub group.

Aukap.