Cold gas dynamic spray apparatus, system and method

A system for cold gas dynamic spraying of particulate material, the system comprising:

• (a) a nozzle having
• a first, substantially linear, flow path from a first end to a second end, the first flow path having a cross-sectional area that converges from the first end to a throat of minimum cross-sectional area and diverges from the throat to the second end,
• a working gas inlet proximal the first end to permit working gas to enter the first flow path substantially parallel to the first flow path,
• two or more particle inlets at a location between the throat and the second end to permit particulate material to enter the first flow path at the location, the two or more particle inlets arranged symmetrically around the first flow path, the two or more particle inlets having particle flow paths therein, and
• an outlet at the second end through which the particulate material exits the nozzle, substantially all of the particulate material being in solid phase when exiting the nozzle;
• (b) one or more non-combustion sources of pressurized working gas in fluid communication with the working gas inlet;
• (c) one or more sources of the particulate material in particle flow communication with the two or more particle inlets;
• and,
• (d) a sink coupled between the one or more particulate material sources and the two or more particle inlets for clearing the two or more particle inlets of residual particulate material when the system is not spraying the particulate material out the nozzle, the sink operable to reduce a pressure in a chamber that is selectively coupled to the two or more particle inlets between the two or more particle inlets and the one or more particulate material sources, so that the pressure in the chamber becomes lower than that of the particle flow communication to draw the residual particulate material into the chamber;
• wherein the sink comprises a valve for controlling communication between the two or more particle inlets and the chamber, and wherein the chamber is connected to an exhaust port through which the particles drawn out of the particle inlets are expelled.