Experimental study of the injection of fluids at high pressure (supercritical) for a rocket engine type application.

PHD Position.

The suggestion to use supercritical fluids is a century old. They have been used as solvents in reaction media or as fluids for propulsion. In the latter case, the tendency is to increase the pressure in the combustion chamber in order to increase the efficiency of the jet engines when using the new generation kerosene and thus considerably reduce the CO2 emissions and NOx production. As a result, the liquid fuel can be injected under supercritical conditions (or compressed liquid). Many energy systems involve a thermodynamic transition from a subcritical state to a supercritical state. The INSIDE project aims to study the impact of the behavior of the phases (subcritical and supercritical) on the mixture through innovative diagnostics coupled with numerical simulations. The CORIA laboratory and the CMAP of the École Polytechnique are associated in this project.

Experimental data for this type of injection regime remains scarce and / or poorly documented. The ANR REFINE (http://www.coria-cfd.fr/index.php/REFINE), completed in 2018, aimed to overcome this knowledge deficit by the experimental and numerical study of injection in diets sub, trans and supercritical of an ethane jet unassisted in helium in an enclosure at variable pressure and temperature. All of these results are available in N. Vallée's thesis defended at CORIA in 2018. During the REFINE project, it turned out that setting up high-pressure diagnostics was a challenge that required further investigation.

The CORIA phd offer proposed here is the continuation of the ANR REFINE. The goal is to perform a series of quantitative measurements (density, speed) of a supercritical jet. This is a real challenge because the development of a truly controlled experience in pressure and temperature is delicate. In addition, innovative diagnostics will be used for the first time in the context of supercritical fluids: Spontaneous Raman scattering and femtosecond double-pulse imaging. The development of these diagnostics will be a key point of the project. This study is therefore essential in understanding the disintegration of supercritical jets and will also make it possible to provide the scientific community with an exploitable experimental database for the validation of computer codes. A coaxial type injector is envisaged here in order to have a better control of the flow and to approach the final application of the rocket engine injectors. Post-processing codes using artificial intelligence (AI), thermodynamics and / or fluid mechanics may be used in order to deepen the knowledge of these very specific flows.