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January 30, 2008, 01:10 |
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#1 |
Guest
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hi all,
I am modeling hybrid rocket combustion. I use axi-symmetric model. My motor consists of a cylindrical combustion chamber and a convergent nozzle. I model only the cylindrical port. So my grid is in the shape of a rectangle. From the left surface oxidiser comes in. From the top surface fuel comes in. The bottom line is the axis and on the right side a convergent nozzle is fitted. The model grid can be found in "http://picasaweb.google.com/guru.palani" inside Projects folder. As a first step, I keep the full inlet of the port (left side of rectangle) for oxidizer inlet and as I said the top surface becomes the inlet for fuel. So as such, there is a cross flow between oxidiser and fuel. Now, the problem is, I require the fuel to come out normally from the fuel inlet boundary.(top surface of the rectangle), which I am not getting. I use, density based solver, ideal gas approximation for fluids (so I could not use velocity inlet condition), and mass flow inlet boundary condition for both fuel and oxidiser. And moreover as I switch on the reaction, after some iterations, I see reverse flow in fuel inlet which is something very much disliked, because any change in the fuel flux makes the flame to go off. When I specify the normal mass flux, if reverse flow happens then it means that the boundary condition I specified (defined mass flux normal to the boundary) has not been satisfied. How do I tackle it..?? I need fuel to enter into the port normal to the surface at all the time.What should I do??? Is there a possibility to specify velocity at the boundary for compressible calculations??? Is there a possibility to specify some porous wall kind of boundary???I saw porosity can be defined at a zone and not at the boundary. Or is there a way to model some permeable membrane type of boundary??? Any sort of help would be highly appreciated. Thanks in advance, Palani. |
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January 30, 2008, 01:12 |
Re: Combustion in Hybrid Rocket Motor
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#2 |
Guest
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sorry, I did not set the subject line in the previous message.
Thanks, Palani. |
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