Supersonic exhaust nozzle having reduced noise levels for CO.sub.2 cleaning system
AssigneeFord Motor Company
InventorLakhi N. Goenka
Life of this patent
Estimating the term…
Abstract
A CO.sub.2 nozzle receives and expels liquid CO.sub.2 through orifices sized for converting the CO.sub.2 liquid into CO.sub.2 snow. A body, defining an elongated cavity therein, is coupled to the CO.sub.2 nozzle such that the CO.sub.2 snow is ejected into the cavity. An exhaust nozzle is coupled to the body and the cavity therein for directing the pressurized CO.sub.2 snow toward the workpiece. The exhaust nozzle is operated in an overexpanded mode for containing the shockwave within the nozzle for reducing the shear noise therefrom. Pressurized air is injected into the elongated cavity for exhausting the CO.sub.2 snow under pressure.
Claims6
An apparatus for cleaning a workpiece with abrasive CO.sub.2 snow, comprising in combination:
- a nozzle for receiving and ejecting liquid CO.sub.2 through at least one orifice sized for converting the liquid CO.sub.2 into solid CO.sub.2 snow,
- a body defining a cavity therein, with said nozzle being coupled to said body for ejecting the CO.sub.2 snow into said cavity,
- first means, coupled to said body, for injecting pressurized air into said cavity for carrying the CO.sub.2 snow from said orifice in said nozzle, and
- an exhaust nozzle including a subsonic section coupled to said cavity within said body for receiving the CO.sub.2 snow and air under pressure therefrom, a throat section and a supersonic section for directing the air and CO.sub.2 snow toward the workpiece, with said supersonic section being operated in the overexpanded mode for containing the shockwave therein, thereby reducing the noise produced by the pressurized air and CO.sub.2 snow exiting said exhaust nozzle.
A method for cleaning a workpiece with abrasive CO.sub.2 snow, comprising:
- receiving CO.sub.2 in a liquid form at a first pressure and temperature,
- passing the liquid CO.sub.2 through an orifice in a nozzle for changing the CO.sub.2 from the liquid phase along a constant entropy line to a mixture of CO.sub.2 liquid and CO.sub.2 snow,
- injecting pressurized air into a cavity adjacent the nozzle for receiving and mixing with the CO.sub.2 snow,
- collecting the resulting CO.sub.2 snow and pressurized air within the cavity and then accelerating the mixture to supersonic speeds through a converging/diverging exhaust nozzle, with the diverging section of the exhaust nozzle having a contour for directing the flow of the CO.sub.2 snow toward the workpiece, and then
- decelerating the air within the diverging section of the exhaust nozzle to subsonic speed, thereby generating a normal shockwave within said exhaust nozzle and suppressing shear layer noise.
Dependencies are inferred from the claim text.