Arabian Journal for Science and Engineering https://doi.org/10.1007/s13369-019-03774-1 RESEARCH ARTICLE - MECHANICAL ENGINEERING Numerical Simulation of Liquid Fuel Injection in Combustion Chamber Syed Azeem Inam 1 · Mukkarum Hussain 2 · Mirza Mehmood Baig 3 Received: 29 March 2018 / Accepted: 8 February 2019 © King Fahd University of Petroleum & Minerals 2019 Abstract Combustion of cryogenic propellants is of great technological interest for researchers and scientists nowadays. Due to high specific impulse, the use of liquid oxygen and hydrogen as cryogenic propellants will have preferences in the years to come. In the present study, RCM-3 configuration of MASCOTTE test facility is used for the investigation of supercritical cryogenic fuel combustion. The injector of this test case is a shear-coaxial injector consisting of a core of liquid oxygen surrounded by a high-speed flow of gaseous hydrogen. Pressure-based steady-state 2D axisymmetric scheme with non-premixed combustion model and compressibility effect under non-adiabatic conditions is used in the present study. Rich fuel stream flammability limit of 0.2 is used to accommodate non-equilibrium effects. Simulations are carried out for different turbulence models with ideal and real gas assumptions. Pressure-implicit with splitting of operators is used for pressure–velocity coupling while standard k–ε, standard k–ω, and SST k–ω turbulence models are used for the parametric study. Effects of ideal gas and real gas assumptions are also studied. A very low value of under-relaxation factor for density (0.01) is used to encounter stability issues. Computed results show that SST k–ω turbulence model with real gas assumptions provide qualitatively as well as quantitatively reasonable and encouraging results. Although peak temperature value is under-predicted, its location and temperature profile along the axis are accurately predicted through real gas assumption, whereas results with ideal gas are far away from experimental values. This provides conclusive evidence that the ideal gas assumption is not appropriate for fluids in the cryogenic state as liquid oxygen in the present study. Improved modeling and inclusion of detailed chemical kinetic mechanism will provide much improved results. Present results are very promising and encouraging to use CFD for the simulation and modeling of cryogenic fuel combustion in the supercritical state. Keywords Computational fluid dynamics · Non-premixed combustion · Shear-coaxial injector · Liquid oxygen/gaseous hydrogen · Supercritical combustion · Cryogenic fuel 1 Introduction An action performed to change the motion of a body is termed as propulsion [1]. In the application of propulsion, a considerable technological interest lies in the combustion of cryogenic propellants [2]. The combustion process asso- ciated with liquid oxygen and gaseous hydrogen systems is very complex [3]. Usage of liquid propellants has allowed a significant progress because of its good flexibility and high performance [4]. At high-pressure conditions, there are B Syed Azeem Inam syedazeeminam@gmail.com 1 Sindh Madressatul Islam University, Karachi, Pakistan 2 Institute of Space Technology, Islamabad, Pakistan 3 NED University of Engineering and Technology, Karachi, Pakistan regions where the thermodynamic properties of propellants deviate from ideal behavior [5]. Cryogenic propellants are generally used at high pressures for combustion in several engines [4]. There is a high probability that liquid oxygen and gaseous hydrogen will be preferred as an option of cryogenic propellants for the next decades. The reason is their high specific impulse which results in the increase in launcher’s performance [6]. The injectors for liquid propellants are considered as a dynamic component of an engine as they always function in a non-steady flow environment [7]. Hydrogen is an ideal fuel for fuel cells as it can be produced from any hydrocarbon fuel, various biological materials, from water, and because of its high reactivity and zero emission characteristics [8]. Mostly, cryogenic hydrogen as fuel and liquid oxygen as oxidizer are separately injected at very high pressure into the combustion chamber [2]. Usually, in the applications of 123