Heat transfer modes in supersonic hydrogen combustion

Abstract

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.A miniature wind tunnel has been built which harnesses the power to hold supersonic flows and supersonic combustion. Experiments have been performed to test the sustainability of hydrogen combustion in supersonic Mach flows. Supersonic combustion allows hypersonic flight viability. Compressed air at different pressure inlets was combined with hydrogen at a constant flow rate for the combustion reaction. Pressure ratios across the flow chamber corresponded to supersonic Mach numbers of about 2.5. The ensuing fuel-air mixture ignited with miniature spark plugs to initiate and sustain combustion at the high Mach flow. Special attention was paid to the pre-mixture of the hydrogen fuel and incoming air because of the relationship between pre-mixture and flame stability. The stability of combustion is especially important in high-speed flight, as seen in ramjet and scramjet design. The combustion reaction within the scramjet engine transmitted heat by means of conduction, convection and radiation, but not much change in temperature was seen, as predicted theoretically, within the engine because of the small scale. However, large temperature gradients were seen throughout the shrouds of the combustion chamber because of conduction. Different materials were used for shrouds to see the various effects of the materials variation as heat sinks for the combustion reaction. Experimental results are verified using laser diagnostics in cold flow, and theoretical analysis is also used in parallel to anchor and check data collected by sensors