Particle-Impact Ignition Experiments at High Oxygen Pressure
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Metal particle contamination is a concern for liquid rocket engines that use oxidizer-rich staged combustion (ORSC) schemes. Under some circumstances, contaminant particle impact can initiate sustained combustion, providing an ignition source for engine components and a combustion event that consumes structural materials and leads to launch failure. Energetic impacts heat the particles to the point of ignition and provide kindling for the base metal. Experiments are underway in a characterized, purpose-built shock-tube facility to investigate the effects of oxygen pressure, target material and other parameters. Test conditions approach those found in ORSC engines. High speed imaging provides particle velocity at impact and records the outcome of each impact event. The results have shown that particle-based ignition events can be induced under favorable conditions, as long as intimate contact is maintained between particle and target material. Propagation of combustion to the base metal on a sustained basis is relatively infrequent, but has been observed. Particle-initiated combustion durations and burn rates have been measured for several particle/target combinations. The facility allows for systematic investigation, although the various parameters are coupled and underlying complexities are involved in determining outcomes. Results indicate the importance of oxygen pressure, target material and temperature.
author list (cited authors)
Crofton, M. W., Morehart, J. H., Thomas, J. C., & Petersen, E. L.