Experimental Investigation on Methane in Transcritical Conditions

Abstract

The use of the Methane as coolant in a regenerative liquid rocket engine (LRE) presents some difficulties since transcritical fluidynamics operating conditions occur in the cooling channels. Transcritical conditions cause large fluid properties variation that strongly influences the coolant performance. The HYPROB program is carried out by CIRA under contract by the Italian Ministry of Research with the main objective to improve National system and technology capabilities on liquid rocket engines for future space applications, with specific regard to LOx/LCH4 technology. Its main objective is to develop an test a LOX/LCH4 demonstrator. In order to match this objective a specific breadboard, the Methane Thermal Properties (MTP) breadboard has been manufactured and test. It is based on an electrical heating of a single representative cooling channel that has the aim to validate numerical methodologies and to improve the understanding of relevant physics of methane thermal properties in transcritical conditions. The experimental test campaign has been succsesfull performed at Maurice J. Zucrow Laboratories in Purdue University and the paper presents the main results

Transcritical Behavior of Methane in the Cooling Jacket of a Liquid-Oxygen/Liquid-Methane Rocket-Engine Demonstrator

“…However, it is possible to observe the transcritical conditions of methane at x/L = 0.75, where some parts of fluid near the bottom wall of the channel have already reached the critical temperature. Thus, a sort of thermal stratification is evident [20,21,30], as pointed out by Figure 16d: very high gradients are observed near the bottom surface of the channel since some parts of the fluid near the bottom walls as well as side walls tend to behave like a "gas", while in the upper zones of the channel, where temperature values are lower, methane tends to remain in "liquid-like" conditions. From the throat region, larger parts of fluid begin to behave like a "vapor" and after x/L = 0.52, the fluid is fully composed by a supercritical gas because the temperature values overcome the pseudocritical one all over the fluid domain, as also confirmed by density axial profiles, plotted in Figure 14, and the dimensionless fields reported hereinafter in Figure 17.…”

“…Nowadays, although huge efforts have been spent, this kind of investigations remains current, especially for methane-based LREs. Indeed, data under theoretical, numerical and experimental points of view are still needed, if compared to other cryogenic propellants, such as hydrogen, to validate engineering tools and numerical codes [19][20][21]. In the case of methane, evolving in a regenerative cooling jacket, the refrigerant is injected in liquid phase, but due to the huge thermal load from combustion gases, it typically shows a transcritical behavior [22].…”