Accession Number : ADA540243


Title :   Experiments and Numerical Simulation of Mixing under Supercritical Conditions (PREPRINT)


Descriptive Note : Journal article preprint


Corporate Author : AIR FORCE RESEARCH LAB EDWARDS AFB CA


Personal Author(s) : Schmitt, Thomas ; Rodriguez, J ; Leyva, I A ; Candel, S


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a540243.pdf


Report Date : 08 Feb 2011


Pagination or Media Count : 58


Abstract : Supercritical conditions designate a situation where the working fluid pressure is above the critical point. Among these conditions, it is interesting to identify a transcritical range which corresponds to cases where the pressure is above the critical point, but the injection temperature is below the critical value. This situation is of special interest because it raises fundamental issues which have technological relevance in the analysis of flows in liquid rocket engines. This situation is here envisaged by analyzing the behavior of a nitrogen shear coaxial jet comprising an inner stream injected at temperatures close to the critical temperature and a coaxial flow at a higher temperature. Experiments are carried out both in the absence of external modulation and by imposing a large amplitude transverse acoustic field. Real gas Large Eddy Simulations are performed for selected experiments. The combination of experiments and calculations is used to evaluate effects of injector geometry and operating parameters. Calculations retrieve what is observed experimentally when the momentum flux ratio of the outer to the inner stream J = (rho-eu2 e)/(rho-iu2 i) is varied. Results exhibit the change in flow structure and the development of a recirculation region when this parameter exceeds a critical value. The instantaneous flow patterns for different momentum flux ratios are used in a second stage to characterize the dynamical behavior of the flow in terms of power spectral density of velocity and density fluctuations. Results obtained under acoustic modulation provide insight on mixing enhancement of coaxial streams with a view of its possible consequences in high frequency combustion instabilities. It is shown in particular that the presence of strong acoustic modulations notably reduces the high density jet core length, indicating an increased mixing efficiency.


Descriptors :   *COMPUTERIZED SIMULATION , *EXPERIMENTAL DATA , *LIQUID PROPELLANT ROCKET ENGINES , *NUMERICAL METHODS AND PROCEDURES , *SUPERCRITICAL FLOW , ACOUSTICS , COAXIAL CONFIGURATIONS , COMBUSTION , CRITICAL TEMPERATURE , CRYOGENICS , EDDIES(FLUID MECHANICS) , EQUATIONS OF STATE , FLOW , FLUIDS , HARMONIC ANALYSIS , LIQUID OXYGEN , MATHEMATICAL MODELS , MIXING , NUMERICAL ANALYSIS , POWER SPECTRA , RECIRCULATION , SHEAR PROPERTIES , STREAMS , STROUHAL NUMBER


Subject Categories : Numerical Mathematics
      Fluid Mechanics
      Liquid Propellant Rocket Engines


Distribution Statement : APPROVED FOR PUBLIC RELEASE