TECHNOLOGY PROPOSES TO CONDUCT A COMPREHENSIVE PROGRAM OF EXPERIMENTS ON THE LARGE-SCALE TURBULENT MOTIONS IN SWIRLING, STRATIFIED, CONFINED JET FLOWFIELDS.

TECHNOLOGY PROPOSES TO CONDUCT A COMPREHENSIVE PROGRAM OF EXPERIMENTS ON THE LARGE-SCALE TURBULENT MOTIONS IN SWIRLING, STRATIFIED, CONFINED JET FLOWFIELDS. THE PROPOSEDFLOWFIELDS SIMULATE THOSE FOUND IN GAS TURBINE COMBUSTORS, AND IN SOME RAMJET COMBUSTORS CURRENTLY UNDER DEVELOPMENT. PRESENTLY, STATE-OF-THE-ART COMPUTER CODES PRODUCE UNRELIABLE COMBUSTOR FLOWFIELD PREDICTIONS AND LARGE-SCALE TURBULENCE STRUCTURE PLAYS A ROLE IN RAMJET COMBUSTION INSTABILITIES THAT IS POORLY UNDERSTOOD. THE PROPOSED EXPERIMENTS (PHASES I AND II) WILL INTEGRATE THREE INGREDIENTS IN A UNIQUE APPROACH TO THE COMBUSTOR FLOWFIELD PROBLEMS: 1) HELIUM WILL BE INJECTED INTO THE CENTRAL RECIRCULATION REGION TO SIMULATE THE LOW DENSITY PRODUCTS OFCOMBUSTION. (2) A CENTRAL SIREN SYSTEM WILL BE USED TO ARTIFICALLY EXCITE VARIOUS MODES OF THE LARGE SCALE COHERENTSTRUCTURE. 3) A TRAVERSING HELIUM CONCENTRATION PROBE WILL BE CONDITIONALLY SAMPLED (IN PHASE WITH THE EXCITATION) TO PROVIDE QUANTITATIVE INFORMATION ON THE CONTRIBUTIONS OF THELARGE SCALE MOTIONS TO THE MEASURED "TURBULENCE". THE PAYOFF OF THE PROPOSED RESEARCH WILL BE TO PROVIDE A MORE THOROUGH UNDERSTANDING OF THE ROLE OF LARGE SCALE MOTIONS INRAMIET COMBUSTION INSTABILITIES AND WILL PRODUCE A DATA BASEOF TURBULENCE MEASUREMENTS THAT HAVE BEEN DECOMPOSED INTO VARIOUS ORGANIZED MODES AND RANDOM TURBULENCE TO BE AVAILABLE FOR THE DEVELOPMENT OF IMPROVED COMPUTATIONAL PROGRAMS.