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Accueil du site > Thèmes de recherche > Propulsion spatiale & écoulements à grande vitesse > 3.1 Propulsion spatiale > 3.1.2 Chemical propulsion

3.1.2 Chemical propulsion

3.1.2.1 Studies on propulsion by detonation waves
This study is part of collaboration between ICARE and MBDA France and concerns both pulsed and continuous detonation wave engines. One aim is the evaluation, via numerical simulation, of the performance of a continuous detonation wave engine (CDWE). In CDWE, the propellants are injected into an annular cylindrical chamber and form a layer of fresh mixture, which is consumed by one or more detonation waves. Detonation waves continuously propagate in the azimuthal direction and generate hot gases exhausted through the other end of the chamber. CDWE has two important features : i) in the detonation waves, combustion occurs at a higher pressure than the average pressure in the chamber thus resulting in a potential gain in performance compared to the constant pressure thermodynamic cycle ; ii) the flow structure is such that the flow becomes supersonic at the exit of a cylindrical chamber which allows the use of a nozzle without geometrical throat.

Three numerical models are developed to study a CDWE fed with hydrogen-oxygen mixtures : i) a global model to estimate the performances of an ideal CDWE ; this model was used to demonstrate the theoretical advantage of a CDWE over a conventional engine ; ii) a model based on 2D Euler equations, with which a parametric study was performed by varying the injection conditions and chamber geometry (ACLN4) ; and iii) a model based on 3D Euler equations coupled with a method of adaptive mesh refinement (AMR) is employed to simulate the flow in the chamber. In addition, propulsion by pulsed detonation waves is also studied. In one study, detonation properties of n-heptane in air or oxygen are determined as an example of storable liquid fuel for pulsed detonation applications (see §2.2.2.3 in Thematic Research Group III). Another study was conducted in cooperation with CNES, MBDA and ROXEL in order to determine the detonation properties of liquid oxygen and liquid hydrogen mixtures. Two experimental facilities have been developed : one for non-reactive atomization studies and the other for detonation studies (TH29). In particular, the effect of the size distribution of LOX droplets on the initiation and propagation of the detonation wave is determined ACTI32).

3.1.2.2 Safety of storable liquid propellant systems
A study was conducted on the reactivity of hydrazine with various lubricants used in the micro pumps of spacecraft propulsion systems, in collaboration with CNES and the company CSTM. The objectives were to verify the non-explosive character of the mixture between hydrazine and the lubricants and to study the chemical behaviour of the lubricant subjected to a hydrazine saturated atmosphere. Presently, desorption kinetics of helium in ergols (monomethyldydrazine and MON) is studied. The objective is to gain understanding on the behaviour helium pressurized ergols during temperature variations and pressure drops which may create bubles in the propellant transport channels.

3.1.2.3 Laminar-turbulent transition predictions of a hypersonic spacecraft forebody
This study is developed in the framework of the LEA program conducted by ONERA and MBDA France, with the objective of building and launching a scramjet powered hypersonic vehicle able to fly from Mach 4 to Mach 8, fuelled with either hydrogen or a mixture of methane and hydrogen. For this type of engine, a well-adapted air inlet is a crucial issue and depends on the state of the boundary layer on the forebody, which serves as a compression ramp. It is highly desirable to have a turbulent boundary layer. Hence, it is important to know whether natural transition occurs or not, and if not how to initiate it.

A numerical code based on the local modal linear stability theory has been developed and validated (TH16). This code applied to different flight conditions (Mach number, altitude, angle of attack...), allows to detect different instability mechanisms and to predict the transition with the semi-empirical "eN" method. An original method has been proposed for the integration of amplification rates (ACL156). The stability code was also used to predict the transition during ground tests in two different hypersonic wind tunnels at ITAM, Novosibirsk, Russia : the blow-down T-313 wind tunnel (adiabatic wall, Mach 4 and 6), and the AT-303 impulse wind tunnel (isothermal wall, Mach 6 and 8).

The preparation of experiments, their realization and the comparison between calculations and experimental results have been conducted during another thesis (ACTI122, ACTI123, TH34). The flow field around the forebody for the different experimental conditions has been simulated in order to provide the mean flow profiles for the stability calculations, and to design the gauges for the experiments. The application of empirical criteria allowed designing efficient roughness parameters to trigger transition during the less favorable Mach 8 tests. In addition, a partnership with Tatiana Elizarova from the Russian Academy of Sciences is currently undertaken for the application of the Quasi-Gas Dynamics approach to the direct numerical simulation of the transition on the LEA forebody.

3.1.2.4 The MILES approach for compressible, multicomponent reacting flows
Since about ten years, a numerical activity is conducted at ICARE for the simulation of turbulent flows with complex physics using higher order methods. The final goal is to simulate the turbulent mixing and combustion of a hydrogen jet in co-flowing air, under conditions typical for supersonic combustion chambers. This activity is supported by CNRS-IDRIS with computational time offered on massively parallel supercomputers.

Two numerical codes have been developed for fundamental studies aiming at comparing different numerical schemes for the simulation of turbulent reacting flows (ACLN2). A Direct Numerical Simulation code based on higher order compact schemes with spectral-like resolution has been written and applied to different test cases (TH8). The code is 3D, vectorized and parallelized through task sharing with OpenMP. A second code based on WENO scheme of order 3 to 9 has also been developed in 2D for the simulation of shocked flows. The extension of the WENO code to 3D along with its compilation on various platforms is now achieved. This dissipative code allows the large eddy simulation of compressible, shocked, reacting turbulent flows with (LES) or without (MILES) explicit subgrid models ; hence the possibility to analyze the relative performances and merits of these approaches for the physics of complex flows.