Parametric Study of a 1.5-D Combustion Chamber Numerical Modeling on the Hybrid Rocket Engine Performances
Creators: name:  E. QUERO GRANADO 
name:   J. LESTRADE 
name:   J. HIJLKEMA 
name:   J. ANTHOINE 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: PROPULSION PHYSICS
HYBRID PROPULSION

description: Hybrid rocket technology constitutes both a low-cost and and a high performance solution for a space propulsion system when compared to its rocket propulsion counterparts - liquid and solid-, allowing its application for sounding rockets or small satellite launchers. The high costs implied in the realization of experimental test campaigns in the space domain, has boosted the development of two-dimensional CFD codes permitting to obtain quite accurate results in the simulation of the combustion of hybrid rockets. Nevertheless, the large computing time thereof represents a fairly substantial hindrance for their applicability during the engine pre-design phases, in which the thrust and specific impulse are the results of interest. A 1.5-D combustion chamber modeling of a hybrid rocket engine (HRE) allows to combine the speed and the simplicity in the calculations - characteristics that can be found in 0-D models, for example - with the precision required for the first conception phases of the engine. This kind of modeling is an approximation of the two-dimensional equations of the flow: it is based on the integration of the fluid dynamics equations along the radial direction of the chamber, followed by the numerical computation of the resulting equations through the axial direction. A Gas-Surface Interaction model (GSI) is used to describe the heat and mass transfers at the solid fuel surface, with the use of an Arrhenius law to define the fuel pyrolysis. This latter fact increases the applicability of the model to a wide range of engine configurations and dimensions when compared with empirical fuel regression rate laws, whose coefficients depend on the test conditions. This paper makes a brief presentation of the pseudo 2-D model in a combustion chamber of cylindrical shape, establishes a comparison with three experimental tests from the laboratory database, and addresses, more specifically, a parametric study of this numerical modeling as regards to the engine performances (fuel regression rate, thrust, specific impulse, etc.). The objective is to define the influence of several parameters on the numerical results, and to ensure the obtention of the good trend about the impact of these according to the bibliography results in order to complete the model validation process. For this purpose, three main analysis are considered in this paper, where the selected variables in each of them have been found to affect to a certain degree the HRE performances. The first one, accounts for the effects of a selection of aerodynamics parameters at the entrance of the channel, such as the mass flux, the oxidizer inlet temperature or the chamber pressure among others. The impact of the radiative heat contribution on fuel consumption is also evaluated in this study. The second part of the analysis is devoted to the effects of the thermo-chemical properties of the fuel, which influence the energy exchanges happening at its surface and then, have a repercussion on the fuel regression rate and specific impulse of the engine. Amid the parameters within this category, a focus is made on the the Arrhenius law coefficients used to characterize the fuel ablation, the heat of thermal degradation employed in the energy balance at the surface, or the physical properties of the fuel (density and specific heat). A final study assesses the geometrical aspect of the fuel modeling through the characterization of the scale-up effects and the fuel block architecture (single or multiple ports). These analysis will enable us to evaluate the validity of the model with respect to the references regarding the impact of several parameters on the numerical results, as well as to understand the extent of a simple physics modeling on the simulation of a combustion chamber in a HRE. Furthermore, they could eventually serve as a first step towards the construction of an optimization algorithm to determine the best engine configuration concerning the motor performances (couple of reactants, geometry, inlet oxidizer mass flow law, etc.) for some specified conditions.