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DIFFUSION FLAMES ARE THE FLAME TYPE OF MOST PRACTICAL COMBUSTION DEVICES. THE ABILITY TO PREDICT THE COUPLED EFFECTS OF COMPLEX TRANSPORT PHENOMENA WITH DETAILED CHEMICAL KINETICS IN SUCH SYSTEMS IS CRITICAL IN THE MODELING OF TURBULENT REACTING FLOWS AND IN UNDERSTANDING THE PROCESSES BY WHICH EXTINCTION SOOT FORMATION AND RADIATIVE TRANSFER TAKE PLACE. TURBULENT DIFFUSION FLAMES ARE GENERALLY NONBUOYANT DUE TO THE LARGE FLOW VELOCITIES. IN ADDITION IN PRACTICAL DEVICES COMBUSTOR CONFIGURATION AND FLOW FIELD PATTERNS MAY PRODUCE FLAMES WITH SHARP EDGES. EXTINCTION ALONG THESE EDGES CAN RESULT FROM INCOMPLETE COMBUSTION. IN OTHER REGIONS COMBUSTION GENERATED SOOT PARTICULATES MAY BE FORMED. TO UNDERSTAND BETTER THE FACTORS THAT AFFECT FLAME EXTINCTION AND PARTICULATE FORMATION WE FOCUSED THIS STUDY ON FLAME PHENOMENA AT THE EXTREMES OF THE FUEL DILUTION SPECTRUM NAMELY DILUTE FLAMES NEAR EXTINCTION AND PURE-FUEL (SOOTING) FLAMES. PREVIOUS WORK HAS SHOWN THAT EXISTING COMPUTATIONAL MODELS ARE UNABLE TO PREDICT ACCURATELY THE BEHAVIOR OF THESE SYSTEMS. THE ENHANCED TIME AND SPATIAL SCALES IN A MICROGRAVITY ENVIRONMENT WILL ENABLE THE STABILIZATION OF FLAMES WITH INCREASED LEVELS OF DILUTION AND WILL HELP GENERATE FLAMES THAT HAVE INCREASED SOOT RESIDENCE TIMES COMPARED TO NORMAL GRAVITY FACILITIES. THIS SHOULD PROVIDE AN EXCELLENT PLATFORM TO GAIN A BETTER UNDERSTANDING OF THE FACTORS THAT AFFECT DIFFUSION FLAME LIFT-OFF DISTANCE AND EXTINCTION AND IT SHOULD ALSO PROVIDE AN EXCELLENT TEST-BED TO DETERMINE THE ROLES OF INCEPTION SURFACE GROWTH AND OXIDATION PROCESSES IN SOOT FORMATION MODELS. THE OVERALL GOALS OF THE RESEARCH ARE TO IMPROVE OUR UNDERSTANDING OF THE PHYSICAL AND CHEMICAL PROCESSES CONTROLLING DIFFUSION (I.E. NON-PREMIXED) FLAME STRUCTURE AND LIFTING PHENOMENA (I.E. STABILIZATION) AND TO PROVIDE FOR RIGOROUS TESTING OF NUMERICAL MODELS INCLUDING THERMAL RADIATION SOOT FORMATION AND DETAILED CHEMICAL KINETICS. THE WORK CONSISTS OF BOTH EXPERIMENTAL AND COMPUTATIONAL COMPONENTS. PROGRESS IS SUMMARIZED IN THE FOLLOWING SECTIONS.

$749,325FY2017National Aeronautics and Space AdministrationNASA

Yale Univ

Investigators

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DIFFUSION FLAMES ARE THE FLAME TYPE OF MOST PRACTICAL COMBUSTION DEVICES. THE ABILITY TO PREDICT THE COUPLED EFFECTS OF COMPLEX TRANSPORT PHENOMENA WITH DETAILED CHEMICAL KINETICS IN SUCH SYSTEMS IS CRITICAL IN THE MODELING OF TURBULENT REACTING FLOWS AND IN UNDERSTANDING THE PROCESSES BY WHICH EXTINCTION SOOT FORMATION AND RADIATIVE TRANSFER TAKE PLACE. TURBULENT DIFFUSION FLAMES ARE GENERALLY NONBUOYANT DUE TO THE LARGE FLOW VELOCITIES. IN ADDITION IN PRACTICAL DEVICES COMBUSTOR CONFIGURATION AND FLOW FIELD PATTERNS MAY PRODUCE FLAMES WITH SHARP EDGES. EXTINCTION ALONG THESE EDGES CAN RESULT FROM INCOMPLETE COMBUSTION. IN OTHER REGIONS COMBUSTION GENERATED SOOT PARTICULATES MAY BE FORMED. TO UNDERSTAND BETTER THE FACTORS THAT AFFECT FLAME EXTINCTION AND PARTICULATE FORMATION WE FOCUSED THIS STUDY ON FLAME PHENOMENA AT THE EXTREMES OF THE FUEL DILUTION SPECTRUM NAMELY DILUTE FLAMES NEAR EXTINCTION AND PURE-FUEL (SOOTING) FLAMES. PREVIOUS WORK HAS SHOWN THAT EXISTING COMPUTATIONAL MODELS ARE UNABLE TO PREDICT ACCURATELY THE BEHAVIOR OF THESE SYSTEMS. THE ENHANCED TIME AND SPATIAL SCALES IN A MICROGRAVITY ENVIRONMENT WILL ENABLE THE STABILIZATION OF FLAMES WITH INCREASED LEVELS OF DILUTION AND WILL HELP GENERATE FLAMES THAT HAVE INCREASED SOOT RESIDENCE TIMES COMPARED TO NORMAL GRAVITY FACILITIES. THIS SHOULD PROVIDE AN EXCELLENT PLATFORM TO GAIN A BETTER UNDERSTANDING OF THE FACTORS THAT AFFECT DIFFUSION FLAME LIFT-OFF DISTANCE AND EXTINCTION AND IT SHOULD ALSO PROVIDE AN EXCELLENT TEST-BED TO DETERMINE THE ROLES OF INCEPTION SURFACE GROWTH AND OXIDATION PROCESSES IN SOOT FORMATION MODELS. THE OVERALL GOALS OF THE RESEARCH ARE TO IMPROVE OUR UNDERSTANDING OF THE PHYSICAL AND CHEMICAL PROCESSES CONTROLLING DIFFUSION (I.E. NON-PREMIXED) FLAME STRUCTURE AND LIFTING PHENOMENA (I.E. STABILIZATION) AND TO PROVIDE FOR RIGOROUS TESTING OF NUMERICAL MODELS INCLUDING THERMAL RADIATION SOOT FORMATION AND DETAILED CHEMICAL KINETICS. THE WORK CONSISTS OF BOTH EXPERIMENTAL AND COMPUTATIONAL COMPONENTS. PROGRESS IS SUMMARIZED IN THE FOLLOWING SECTIONS. · GrantIndex