Experimental study on etching-method with electric-insulation-panels for fabricating cooling passages of combined-cycle-engine wall

摘要

Although the walls of scramjet-based combined-cycle engines operating up to a flight number of 10 are subjected to severe heat flux, it is one order lower than that of the rocket engine throats and combustors. The application of a nickel-based heatproof alloy to such engine walls has been suggested, and an etching method as a fabrication technique for cooling passages In a combinedcycle- engine wall has been investigated. Although a nickel-based heatproof alloy is hard, and the machining of thin cooling passages in a large area is difficult, by the use of this etching method with a photographic print, a large area can be easily processed at the same time. As this nickel-based heatproof alloy is also corrosion resistant, ferric chloride solution, a conventional etching solution, cannot be used for such etching. Thus, the authors chose an electrochemical technique for dissolving the nickel-based heatproof alloy. In previous studies, although the dissolution of the nickel-based heatproof alloy was achieved by the electrochemical technique, the passages at the edges were processed deeper than those In the center area in electrochemical etching processing due to the current distribution on a reaction surface of a nickel-based heatproof alloy plate. In the present experiment, electric insulation panels were employed to control the electric current and to obtain uniform passages. The electric insulation panels were installed on the nickel-based heatproof alloy plate around and vertical to the reaction surface. The effect of such electric insulation panels was confirmed analytically and experimentally. Uniform passages on the nickel alloy plate were achieved in the experimental study.