Understanding Injection Into High Pressure Supercritical Environments
Abstract
This paper summarizes the results of systematic research programs at both the DLR and the AFRL which began nearly ten years ago. The research is aimed at improving the understanding of atomization, mixing, and combustion processes associated with coaxially injected liquid propellant rocket engines. Cold flow studies are imperative for investigations without the complexities introduced with combustion. Initial studies utilized liquid nitrogen (LN2) without a co-flow stream into a chamber with ambient pressures exceeding the thermodynamic critical pressure of the injectant. Secondly, cryogenic cold flow studies were extended with consideration of the effects of a co-flowing gas. Parallel to this work, combustion studies with cryogenic propellants were introduced to understand high-pressure coaxial injection phenomena with the influence of chemical reaction. In both cases, high-pressure injection and combustion facilities were specifically designed and implemented to gain maximum information from a single coaxial injector element. Results from visualization, jet initial growth rate, fractal analysis, Raman scattering, visible length scales, and phenomenological modeling are presented and discussed. It is found that the behavior of the injected jet into supercritical ambient is quite different from those at subcritical conditions. In particular, it is found that the nature of atomization is substantially different and departs significantly from the classical cascade of events attributed to low-pressure liquid jet atomization. At elevated pressure conditions, the injected cryogenic liquid jet behaves more like a high-density gas injected into a low-density gas environment. Implications of this behavior on mixing, growth rate, evolution and response of reacting and non-reacting flow-fields, combustion zone time and length scales, and combustor behavior are investigated and discussed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 09, 2003
- Accession Number
- ADA417985
Entities
People
- B. Chehroudi
- D. Talley
- J. J. Smith
- R. Branam
- W. Mayer
Organizations
- Air Force Research Laboratory