Experimental investigation of Ethane and Propane injection under sub- and super-critical conditions

Abstract

Studying a fluid flow under high-pressure conditions through reliable experiments is still nowadays a challenge. When the chamber pressure exceeds the critical pressure of working fluids the supercritical state of matter is reached and the distinction between gas and liquid becomes blurred. For such special conditions, experimental data are scarce and need to be consolidated. Indeed, the modification of the local refractive index induced by density gradient needs to be analyzed with appropriate image-based technique. In the present study, the REFINE test bench (Real-gas Effect on Fluid Injection: a Numerical and Experimental study) has been designed at CORIA Lab to study the non-reactive injection of Ethane and Propane into Nitrogen under sub-and supercritical conditions. The ambient gas pressure can be raised up to 6 MPa and warmed up to 573 K to scan sub-and trans-critical injections. The chamber is equipped with two perpendicular optical axes allowing simultaneously different optical diagnostics. Experimental data are collected from shadowgraph and diffused backlight illumination techniques. Quantitative measurements of jet spreading angle and breakup length are compared to results coming from literature exhibiting multiple flows topologies. KeywordsSupercritical, Experimental, Injection. IntroductionIn propulsion applications like in rocket engines, gas turbines or diesel engines when late injections are performed, injection often occurs at pressures that are above the critical point of the incoming fluids, i.e. at supercritical pressures [1,2]. At such high-pressure conditions, injection is quite different from classical known behaviors observed at low pressure, and studying these new phenomena is challenging. Very few experiments dealing with non-reacting supercritical injection exists in the world, but a substantial experimental data set has been developed over the last few decades at DLR and AFRL laboratories [3]. The main issue is the ambient high pressure that locally affects the refractive index gradient making the delivery of experimental data highly challenging. Therefore this lack of reliable data is damaging for the development of models for turbulence and combustion [4,5,6]. The objectives of the research program REFINE (Real-gas Effects on Fluid Injection: a Numerical and Experimental study) are to bridge the gap between experimental and numerical observations in providing reliable experimental data and new strategies of modeling. The experimental aspect is presently addressed through the development of a new test-bench (next section) and for which a first qualitative analysis is presented. Indeed, many combustion devices involve thermodynamic phase transition from subcritical to supercritical state as in high-pressure combustion chambers of rocket or diesel engines. When the pressure exceeds the critical pressure pc of any substance, the distinction between gas and liquid vanishes and the injection and combustion are quite different from classical known behaviors observed at low pressur...