Mach 10 Hypersonic Nozzle: Improved Flow Quality

The flow quality of the Mach 10 nozzle (exit diameter 1.27 m) at the National Aerospace Laboratory, Chofu, has been significantly improved. The spread of pitot pressure ratio over nearly 60% of the test section width and height was reduced from ′7.5 to ′1.5%. This was accomplished by remachining the nozzle based on a new technique for smoothing the method of characteristics plus boundary-layer correction coordinates. Various sets of possible smoothed contours were checked using two computational fluid dynamics (CFD) codes before selecting one set for machining. These codes were run with the initial contour, and the CFD results were validated by comparison to the initial test data before checking the suggested contours. The change in nozzle radius was less than 1 mm.