Measurement and analysis of heat transfer in a multi-element hydrogen/oxygen rocket combustor

A priori prediction of rocket engine combustor flowfields is extremely difficult due to a number of complicating effects including multiple property phases, unsteadiness due to high rates of energy release and turbulence, and three-dimensionality. Proof of predictive accuracy is limited by the severe environment that precludes direct measurement of most validating parameters. This dissertation describes an experiment undertaken to provide benchmark data for the validation of computational models by measuring the local wall heat flux and axial pressure variations in a multielement rocket combustor operating at pressures between 300 and 1200 psia and mixture ratios between 3 and 6. The experimental combustor comprised seven liquid oxygen/gaseous hydrogen shear coaxial injector elements and a heat-sink cooled thrust chamber instrumented with 41 coaxial thermocouple pairs to measure axial and circumferential variations and 8 pressure transducers to measure axial variations. An additional three coaxial thermocouples were placed on the injector face. Chamber pressure was varied from 300 to 1200 psia and the O/F ratio was varied from three to six. A total of 19 tests were conducted. Maximum measured wall temperatures were kept near 1000 degrees Fahrenheit. To calculate local heat flux, the thermocouple data were modeled using methods including numerical differentiation formulas and inverse methods including Tikhonov Regularization. Calculated wall heat flux ranged from 8 to 20 Btu/in2/sec. Although difficulties were encountered with thermocouple reliability, a high-quality data set was obtained with with experimental uncertainty in the heat flux of approximately 0.06 Btu/in2/sec and demonstrated repeatability. The results of the benchmark study have been assembled for transfer to CFD modelers for validation. Recommendations for improved validation experiments are provided including revised thermocouple design and installation methods, heat flux determination methods, and test article design for maximum utilization of facility and personnel resources