Numerical Investigation of Rocket Engine Cooling Channel Heat Transfer for Different Lng Under Trans and Super-Critical Conditions

Abstract

Liquefied Natural Gas LNG is a promising fuel for rocket engines because it offers high-performance thrust and high energy density. While using it for cooling the engine channel presents some challenges. Hydrocarbon impurities and wall roughness impact the cooling effectiveness of rocket engine channels using LNG as a coolant in subcritical and supercritical conditions are investigated. The Reynolds-averaged-Navier-Stokes equations are numerically solved. This study uses a straight cooling channel with a circular cross-section and uniform heat flux. LNG’s thermophysical and transport properties are calculated using the GERG equation of state and extended corresponding states, respectively. The turbulent models are validated numerically for vapor methane and supercritical hydrogen. The results show that Hydrocarbon compositions play a significant role in cricondenbar pressure. As a result of that, the exit pressure from the cooling channel should be more than the critical pressure of 4.6 MPa for pure methane and more than the cricondenbar 5.1 and 7.5 MPa for lean and rich LNG, respectively, to avoid two-phase flow in the cooling channel. The impacts of various wall roughness configurations on the cooling capabilities and pressure drops are sensitive under Trans and supercritical conditions and Hydrocarbon compositions. An increase in small impurities guides to a decrease in pressure drop and cooling capabilities. This study established the essential relationships to calculate the required cooling channel surface roughness and Nusselt Number within the appropriate pressure drop limit. They depend directly on the composition of ethene or propane present in LNG. Increasing the percentage of carbon atoms in LNG allows designers to increase the surface roughness. It improves heat transfer as the pressure drops remain within the permissible limits at a particular mass flux. The study is expected to provide valuable insights into the design of cooling systems for rocket engines, which are crucial for ensuring optimal engine performance.

Keywords: cooling channel, supercritical pressure, liquefied natural gas, liquid rocket engine, heat transfer