Turbulence Quantification in Supercritical Nitrogen Injection: An Analysis of Turbulence Models

Leandro Magalhães,Francisco Carvalho,André Silva,Jorge Barata

doi:10.18502/keg.v5i6.7052

Abstract

In Liquid Rocket Engines, higher combustion efficiencies come at the cost of the propellants exceeding their critical point conditions and entering the supercritical domain. The term fluid is used because, under these conditions, there is no longer a clear distinction between a liquid and a gas phase. The non-conventional behavior of thermophysical properties makes the modeling of supercritical fluid flows a most challenging task. In the present work, a RANS computational method following an incompressible but variable density approach is devised on which the performance of several turbulence models is compared in conjunction with a high accuracy multi-parameter equation of state. Also, a suitable methodology to describe transport properties accounting for dense fluid corrections is applied. The results are validated against experimental data, becoming clear that there is no trend between turbulence model complexity and the quality of the produced results. For several instances, one- and two- equation turbulence models produce similar and better results than those of Large Eddy Simulation (LES). Finally, considerations about the applicability of the tested turbulence models in supercritical simulations are given based on the results and the structural nature of each model. Keywords: Supercritial fluids, RANS turbulence modeling, Liquid rocket engines

Highlights

Supercritical fluids exist on Earth as a byproduct of naturally occurring phenomena, i.e., crystal formation in aqueous solutions at supercritical conditions
Our objective is to evaluate several turbulence models in a RANS based numerical solver to access the necessary complexity of the said model in providing accurate results of the centerline density distribution for a nitrogen mixing layer
Even if the version here tested is an improvement over the 1998 Wilcox K-ω model, with an added cross-diffusion term introduced to deal with the free-stream sensitivity, it does not provide acceptable results throughout the whole of the domain

Summary

Introduction

Supercritical fluids exist on Earth as a byproduct of naturally occurring phenomena, i.e., crystal formation in aqueous solutions at supercritical conditions. The dynamics of these fluids is still a topic of study, and its implications are not fully understood. The RS-25, the Vulcain, and the Vinci engines are a few examples of Liquid Rocket. Engines (LRE’s) where conditions in the combustion chamber exceed those of the critical point [1]. With increasing development costs for the future and improved rocket engines, there is a need to eliminate the trail-and-errors phase of the development. With enormous demands and competitions for cheaper and safer launchers access to space, the design.

Objectives

Results

Conclusion