| 摘要 |
The ultimate objective of this invention is to provide an improved Cold Gas Dynamic Spray (CGDS) apparatus capable of discharging powdered materials at greater velocities with higher deposition efficiency, as well as a greater variety of materials (e.g. nanopowders). This objective is achieved by attaching a specialized device to an existent CGDS system. The device is a pulse-generator and is attached behind the converging portion of the De Laval-type nozzle. This device significantly increases the efficiency of the spray process in three ways. First, it creates a higher pressure environment that introduces a wave of pulses to the exit stream, thereby increasing the speed of any introduced powder materials. Second, the addition of this device introduces steam to the overall process which also increases the speed of the exit stream. Third, the introduction of steam into the process also increases the drag co-efficient of any injected powders, thereby once again contributing to an increase in the velocity of the exit stream. This improved design and the resulting increased efficiency of the CGDS process also permits a greater choice in the type of powdered materials that may be used. The pulse-generator generates detonation-type impulse waves by injecting hot compressed water into the low-pressure (vacuum) and high-temperature discharge chamber. The vacuum or low-pessure environment in the discharge chamber provides a greater pressure gradient for the creation of detonation-type impulse waves. The injections are repeated in a cyclical manner at a pre-determined frequency. |
