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Paper Information

Journal:   FUEL AND COMBUSTION   FALL 2016-WINTER 2017 , Volume 9 , Number 2 ; Page(s) 95 To 120.
 
Paper: 

NUMERICAL MODELING OF MIXING AND COMBUSTION AT SUPERCRITICAL CONDITIONS FOR A MODEL COMBUSTOR

 
 
Author(s):  BARANI EHSAN, MARDANI AMIR*
 
* DEPARTMENT OF AEROSPACE ENGINEERING, SHARIF UNIVERSITY OF TECHNOLOGY, TEHRAN, IRAN
 
Abstract: 

This paper discusses numerical modeling of the mixing and combustion at supercritical conditions for a rocket model combustor. Fluid behavior is very complex at supercritical conditions. At these conditions, the surface tension of the liquid is zero and the thermodynamic properties such as heat capacity and density are dramatically changed. Therefore, two test cases of RCM01 and RCM03 were selected for modeling using a 2D-Axi-RANS approach. In primary test cases (i.e. RCM01), supercritical nitrogen jet at 59.8bar, and in the second test cases (i.e. RCM03), supercritical flow of gaseous hydrogen-liquid oxygen at a chamber pressure of 60bar and above the critical pressure of hydrogen and oxygen, were investigated. For the nitrogen jet, turbulence models have been studied and it was observed that the k-e Realizable predicts better results in the area of the shear layer and outer recirculation zone, and thus provides better mixing when the equations were discretized using a second order approach. Better predictions of the k-e Realizable model could be due to better estimation of turbulent kinematic eddy viscosity term on the Boussinesq eddy viscosity assumption. It has been observed that the spreading angle depends on the Outer Recirculation Zone (ORZ) predicted by different turbulence models. As the estimated size of ORZ is larger, mixing at core occurs in lower rates and density profile will be uniform posterior. Also, combustion of cryogenic propellants LOx/H2 at very high pressure were examined using the EDC turbulent combustion model and a detailed chemical mechanism. Different turbulence models and equations of state were studied while an upwind first order discretization method was used. The performance of the turbulence models in predicting the flame shape and temperature distribution were investigated and it was found that the k-w SST better estimates the flame shape. Checking the ideal gas and real gas EOS revealed that ideal gas assumptions suffer from large errors in estimating the shape and length of the flame. Different suggestions for the equations of real gas behavior were studied in both experiments and the results showed that SRK EOS yields the closest results to the experimental data.

 
Keyword(s): COMBUSTION, SUPERCRITICAL, MIXING, REAL EOS, TURBULANCE MODELS, HYDROGEN-LOX
 
References: 
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