EXPERIMENTAL AND NUMERICAL STUDY OF CMC LEADING EDGES IN HYPERSONIC FLOWS

摘要

Future transportation concepts aim at high supersonic orrnhypersonic speeds, where the formerly sharp boundariesrnbetween aeronautic and aerospace applications becomernblurred. One of the major issues involved to high speedrnflight are extremely high aerothermal loads, whichrnespecially appear at the leading edges of the plane'srnwings and at sharp edged air intake components of thernpropulsion system. As classical materials like metals orrnsimple ceramics would thermally and structurally failrnhere, new materials have to be applied. In this context,rnlightweight ceramic matrix composites (CMC) seem tornbe prospective candidates as they are high-temperaturernresistant and offer low thermal expansion along withrnhigh specific strength at elevated temperature levels.rnA generic leading edge model with a ceramic wingrnassembly with a sweep back angle of 53° was designed,rnwhich allowed for easy leading edge sample integrationrnof different CMC materials. The samples consisted ofrnthe materials C/C-SiC (non-oxide), OXIPOL andrnWHIPOX (both oxide) with a nose radius of 2 mm. Inrnaddition, a sharp edged C/C-SiC sample was prepared torninvestigate the nose radius influence. Overall, 13rnthermocouples were installed inside the entire model tornmeasure the temperature evolution at specific locations,rnwhereby 5 thermocouples were placed inside thernleading edge sample itself. In addition, non-intrusiverntechniques were applied for surface temperaturernmeasurements: An infrared camera was used to measurernthe surface temperature distribution and at specificrnspots, the surface temperature was also measured byrnpyrometers. Following, the model was investigated inrnDLR's arc-heated facility L3K at a total enthalpy ofrn8.5 MJ/kg, Mach number of 7.8, different angles ofrnattack and varying wing inclination angles.rnThese experiments provide a sound basis for thernsimulation of aerothermally loaded CMC leading edgernstructures. Such fluid-structure coupled approaches havernbeen performed by FOI, basing on a modal approach forrnthe conduction model. Results show, that therntemperature profiles are correctly depicted dependent onrnthe model's angle of attack.