Numerical Simulation of Liquid Propellant Rocket Engines A. Hetem * , J. Miraglia ** , R. Burian ** and C.A.C. Caetano ** * Universidade Federal do ABC-UFABC/CECS, São Paulo, Brazil ** Faculdade de Informática e Administração Paulista / FIAP, São Paulo, Brazil annibal.hetem@ufabc.edu.br Abstract - The development of liquid propellant rocket engines requires tests and dynamical simulations of all its elements in a computer environment. With the advances of the numerical methodologies, particularly of the implicit schemes, the solution of flow problems which require real gas modeling became also feasible by the end of last century. Many research activities are devoted to the numerical simulation of combustion and particularly to flame modeling, being quite important for the development of low emission rocket engines. We present the first results of our developed code that simulates a liquid propellant engine. The code was developed in a modular structure, simulating structural elements such as the combustion chamber, injector, nozzle supersonic, valves and piping and pumping system. Each of these elements was modeled and numerically coded in C++. The elements can be chosen in such a way that many different engine configurations can be evaluated, with different combinations of propellant and oxidant. We present results for a green propellant combination, where alcohol (ethanol) was used together with liquid oxygen and hydrogen peroxide. As a result one can appreciate the evolution of fluxes, pressures, temperatures and other important variables as a function of time. I. INTRODUCTION During the middle years of the XX century, mostly the main development of rocket engines took place. Today, one can consider we achieved a mature stage in this subject. Actual rocket engines are the epitome of rocket design. While design and projects from the 1960s are still flying, the needs of the new century, mostly commercial, are pushing the development of rocket engines, which appear worldwide in significant numbers and concepts [1]. Included in the actual approach are the green concerns, and these preoccupations lead to choices of combustibles that contribute to lower levels of atmospheric pollution. One of the candidates is the hydrogen peroxide, whose catalytic decomposition is in agreement with our ecological interests. The hydrogen peroxide presents some characteristics that lead to a very interesting choice for utilization in propulsive systems [2]. About this composite, the main points are: 1) versatility: the hydrogen peroxide can be used as monopropellant and as oxidant in pre-mixed bipropellant systems; 2) higher density when compared to the majority of propellants, leading to a smaller reservoir volume and consequently a higher mass for the payload; 3) smaller toxic potential (much less toxic than hydrazine or nitrogen tetra oxide); 4) higher oxidant/combustible ratio; 5) long time storage; 6) compatibility with low cost reservoir materials, as aluminum and stainless steel; 7) low cost when compared to other combustibles; 8) easily available in Brazil. This work presents a model developed to simulate a thrust chamber based on the catalytic decomposition of the hydrogen peroxide. All physics and chemistry are included, like heat transfer, gaseous latent decomposition, and also the other rocket engine components, like pipes, valves and orifice injectors, each component with its own contribution to load loss. II. THE MODEL A. Ideal Catalytic Thrust Chamber As presented by [3], the ideal thrust catalytic chamber design must be based on the following assumptions: 1) ideal gas; 2) the temperature inside the combustion chamber is uniform; 3) the thrust chamber is adiabatic; 4) the propellant is injected, gasified and decomposed instantly; 5) one-dimensional flow; 6) the decomposition reaction is an exclusive function of the catalytic; 7) the thermo chemical properties of gases decomposition are functions uniquely of the chemical compositions of the propellant and the catalytic; 8) the catalyst is incompressible. It is worth noting that this engine's combustion chamber is filled with a fixed catalytic bed and is not stagnant, there is a pressure gradient over the entire bed, so it is convenient to divide the chamber as sketched in the fig. 1. The mean pressure rate, C P , as a function of time, t, in the chamber for the monopropellant system is modeled Figure 1. Sketch of thrust chamber and its structures