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Proceedings of the 24th National and 2nd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2017)

ISSN: 2688-7231 (Online)

LOX/CH4 JET FLAMES AT NEAR CRITICAL PRESSURES

Arun M
University of Kerala, Thiruvananthapuram, Kerala, India

Shamnad Saifudeen
TKM College of Engineering, Kollam, Kerala, India

Hari Krishnan M
TKM College of Engineering, Kollam, Kerala, India

Dr. Jose Prakash M
TKM College of Engineering, Kollam, Kerala, India

DOI: 10.1615/IHMTC-2017.240
pages 171-178

Abstract

Prediction of Combustion phenomenon in rocket thrust chambers with one of the propellants in thecryogenic state is very essential and it remains as a challengingproblem while designing high-pressure rocket engines. The phenomenon becomes more complex once one of the propellants enters the chamber at a pressure near to its critical value. The propellant thermophysicalproperties show a drastic variation when the temperature is near the critical region. Incorporation of this property variation is necessary for obtaining the proper flame shape and peak temperature inside the combustion chamber. In the present study, the geometry of the RCM-3MASCOTTE combustor is used for the numerical simulation of mixing and combustion of liquid oxygen with methane under transcritical and supercritical conditions. Studies have been carried out with various turbulence models and real gas Equations of State (EoS). A pressure based numerical algorithm available in ANSYS Fluent has been used and the properties are taken from NIST (National Institute of Standards and Technology). The combustion model used is Eddy Dissipation (ED). Studies are conducted for different combustion chamber pressures and oxidizer inlet temperatures. Studies are also carried out to see how the flame is propagating from the injector tip and exact location of peak temperature along the axial direction. The results reveal that at transcritical conditions, the flame shape is that of an incandescent bulb. While increasing the chamber pressure the location of the peak temperature shifts towards the injectorside. This is happening up to 8.0MPa chamber pressure, which is very near to the critical pressure of major combustion product carbon dioxide. However, a reverse trend is observed beyond 8 MPa and this is the result of drastic variations in density and specific heat of the oxidizer due to the pseudo-boiling phenomenon. Upon combustion the density of the mixture decreases, velocity increases and there occurs flame expansion. This results in slight pressure drop which induces a central recirculation zone that restricts the flame tip. At higher oxidizer inlet temperaturesthere is no secondary recirculation and hence no abrupt termination of flame is observed.

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