Raymond B. Edelman

Mixing and Combustion in Two-Phase Flows with Application to the B-0-H-N System

This paper is a report upon some of the interrelated analytical and experimental studies designed to provide information on the combustion of boron particles in a high-speed air stream. The program upon which this work is based involved single particle ignition and combustion studies, B2O3 condensation studies, and axial and lateral injection of the effluent from a B-O-H-N gas generator into a supersonic air stream. This paper will emphasize the axial and lateral injection studies. Experimental data include profile measurements associated with both axial and lateral injection of hot and cold particle-laden primary streams injected into a variable temperature high-speed airstream. In addition, still color photographs and movies have been obtained. The analyses include treatments of coaxial mixing and combustion, and penetration for the description of the axial and lateral injection configurations, respectively. The coaxial analysis includes a special formulation for the turbulent diffusion of the particulate phase and the lateral injection analysis includes a treatment of the coupled gas-particle trajectories. Comparison of the analysis with the experiments shows very good agreement for both the coaxial and lateral injection flows provided the former is based upon the new mixing analysis and the latter employs a drag law based upon experiments with particulate clouds undergoing large accelerations.

Combustion of liquid hydrocarbons in a high-speed airstream

A theoretical formulation and experimental results of the high-speed mixing, ignition, and combustion characteristics of liquid fuels injected directly into a high-velocity airstream are presented. Experiments were performed in a direct connect constant area combustor supplied by a Mach 2 air stream at a static pressure level of 1 atmosphere and at total temperatures ranging from ambient (530°R) to approximately 3300°R. The fuel was liquid hexane and was injected laterally into the supersonic flow through piloted and nonpiloted injector configurations. It was found that autoignition and stable combustion occurs for air total temperatures above about 2600°R. Furthermore, the liquid fuel was effectively ignited and burned stably below this autoignition level by employing a small reacting pilot j et. Minimum pilot size and energy requirements were then established. It was found that the pilot mass flows needed for ignition and sustained combustion were small compared to the main fuel and air flow rates. Comparison with theory indicates combustion efficiencies up to 93% were obtained.

ANALYTICAL INVESTIGATION OF THE EFFECTS OF VITIATED AIR CONTAMINATION ON COMBUSTION AND HYPERSONIC AIRBREATHING ENGINE GROUND TESTS.

Abstract : A broad analytical study has been performed to define and evaluate the effects of vitiated air species contamination on combustion research development tests. The processes investigated include: equilibrium, chemical relaxation, vibrational relaxation, condensation, boundary layer and shock boundary layer interaction, combustion, mixing, and overall test engine performance. This study is concerned with the effects of hydrogen and propane vitiation in heating the working medium to temperatures of approximately 7000 degrees R. It is apparent that for the flight conditions investigated here, boundary layer phenomena and mixing are essentially insensitive to vitiation and that chemical equilibrium is adequate for facility nozzle flow determination. Furthermore, vitiation tends to enhance vibrational equilibrium. It is found, however, that the chemical kinetics of combustion and test engine nozzle recombination losses must be considered for both vitiated and pure air configurations. Condensation and combustion kinetics appear as the two most significant processes altered by the effects of vitiation. In general, it has been found that vitiation with propane in comparison with hydrogen results in substantially smaller mismatch in molecular weight while also extending the condensation limit. (Author)