PULSE COLD GAS DYNAMIC SPRAYING APPARATUS

摘要

The ultimate objective of this invention is to provide an improved Cold GasDynamic Spray(CGDS) apparatus capable of discharging powdered materials at greatervelocities with higherdeposition efficiency, as well as a greater variety of materials (e.g.nanopowders). This objective isachieved by attaching a specialized device to an existent CGDS system. Thedevice is apulse-generator and is attached behind the converging portion of the De Laval-type nozzle. This devicesignificantly increases the efficiency of the spray process in three ways.First, it creates a higherpressure environment that introduces a wave of pulses to the exit stream,thereby increasing thespeed of any introduced powder materials. Second, the addition of this deviceintroduces steam tothe overall process which also increases the speed of the exit stream. Third,the introduction ofsteam into the process also increases the drag co-efficient of any injectedpowders, thereby onceagain contributing to an increase in the velocity of the exit stream. Thisimproved design and theresulting increased efficiency of the CGDS process also permits a greaterchoice in the type ofpowdered materials that may be used.The pulse-generator generates detonation-type impulse waves by injecting hotcompressed waterinto the low-pressure (vacuum) and high-temperature discharge chamber. Thevacuum or low-pessureenvironment in the discharge chamber provides a greater pressure gradient forthe creationof detonation-type impulse waves. The injections are repeated in a cyclicalmanner at apre-determined frequency.