Experimental study of interaction of supersonic gas jet with a substrate under Cold Spray process

The interaction of the supersonic gas jets of rectangular section with a flat obstacle under conditions of the Cold Spray process was studied. Pressure distribution on the obstacle surface at various jet regimes is measured. Instability of the jet as well as compressed layer structure is observed with the aid of laser schliren visualization. Depending on jet pressure ratio, distance between nozzle exit and the obstacle various modes of the jet are registered including classical mode, the mode with peripheral maximum and circulate bands, the mode with oscillations of bow shock, and the mode with jet oscillations. It is shown that the distribution of pressure along the smaller size of the nozzle is self-similar in the classic regime of the impingement and does not depend on the angle of encounting at phi = 50 - 90degrees. The critical parameters of the gas, when it accelerates along the surface, are reached near the boundary of the falling jet. The distributions of the stagnation temperature and heat transfer coefficient in the near-wall jet at various stand-off distances are experimentally obtained. It is shown that the experimental data on the heat transfer coefficient are higher than the calculated ones, and this difference can be explained by velocity fluctuations in the vicinity of the stagnation point and in the near wall jet.