Over prediction of temperature during methane-oxygen combustion

Amigo94 · March 26, 2018, 13:05

Im simulating ox-ch4 combustion in a rocket thrust chamber. The details of the combustion model is explained below
Reaction mechanism- single step eddy dissipation mechanism
Variation of cp of reactants and products - piece wise linear
Chamber presure- approximately 1 MPa
Turbulence model - k epsilon realizable
Solver- Coupled pseudo transient (time scale factor for species and energy is 10)
My thrust chamber is a subscale chamber having only 300 mm length and 50 mm diameter. I'm only simulating one fifth of the chamber and imposing periodic boundary condition on the two sides. Mesh contains 1926451 elements with maximum skewness of 0.83.
Right now im getting a maximum temperature of 4670 K which is not possible according to experimental results.
If anyone has experience with this type of problem, please help

racing_student · November 6, 2018, 14:44

Hi, I also had this problem and hope I could help also after the long time difference. I solved it by including more reaction species which are produced by the cumbstion. I calculated the species and the stochiometric coefficients with NASA CEA. Of you include more species the temperature becomes lower. I also used a polynomial function for the cp values, because the default settings for the cp values are Not accurate for high temperatures. The polynomials you could find at a eddy dissipation tutorial by ansys fluent.

March 26, 2018, 13:05	Over prediction of temperature during methane-oxygen combustion	#1
Amigo94 New Member Godwin Join Date: Mar 2018 Posts: 1 Rep Power: 0	Im simulating ox-ch4 combustion in a rocket thrust chamber. The details of the combustion model is explained below Reaction mechanism- single step eddy dissipation mechanism Variation of cp of reactants and products - piece wise linear Chamber presure- approximately 1 MPa Turbulence model - k epsilon realizable Solver- Coupled pseudo transient (time scale factor for species and energy is 10) My thrust chamber is a subscale chamber having only 300 mm length and 50 mm diameter. I'm only simulating one fifth of the chamber and imposing periodic boundary condition on the two sides. Mesh contains 1926451 elements with maximum skewness of 0.83. Right now im getting a maximum temperature of 4670 K which is not possible according to experimental results. If anyone has experience with this type of problem, please help

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November 6, 2018, 14:44		#2
racing_student New Member Marius Join Date: Nov 2018 Posts: 17 Rep Power: 8	Hi, I also had this problem and hope I could help also after the long time difference. I solved it by including more reaction species which are produced by the cumbstion. I calculated the species and the stochiometric coefficients with NASA CEA. Of you include more species the temperature becomes lower. I also used a polynomial function for the cp values, because the default settings for the cp values are Not accurate for high temperatures. The polynomials you could find at a eddy dissipation tutorial by ansys fluent.