Apparatus and method for jet noise suppression

A method of suppressing noise in a jet comprising the steps of:

• (a) providing a jet exhaust nozzle from which the jet exits;
• (b) providing an elongated porous member fixed within said nozzle and having a portion thereof projecting rearward from the center of said jet exhaust nozzle and downstream in the jet;
• thereby,
• (c) creating a pressure difference between the jet and the interior of the porous member to affect the static pressure in the jet downstream of the exhaust nozzle and influence the rate of entrainment of ambient fluid into the jet downstream of the exhaust nozzle.

A method of suppressing noise in a jet comprising the steps of:

• (a) providing a jet exhaust nozzle from which the jet exits;
• (b) providing an elongated substantially equal diameter hollow nozzle plug centerbody;
• (c) extending the hollow nozzle plug centerbody rearward from the jet equal to at least 10D, D being the average distance from the outer surface of the centerbody to the exhaust nozzle wall measured at the jet exit;
• (d) providing a pressure source for producing a pressure differential between the jet and the interior of the hollow centerbody along the length of the centerbody downstream of the jet exit to affect the static pressure in the jet stream and influence the rate of entrainment of ambient fluid into the jet downstream of the exhaust nozzle.

A method of suppressing noise in a jet operating in an ambient fluid comprising the steps of:

• (a) providing a jet exhaust nozzle from which the jet exits;
• (b) providing an elongated hollow nozzle plug centerbody supplied with perforations about the exterior surface thereof, the number and size of the perforations being related to the length of the centerbody and the maximum mass flow of the jet;
• (c) extending a portion of the centerbody rearward from the exhaust nozzle to a distance downstream equal to at least 10D, D being the average distance from the outer surface of the centerbody portion within the exhaust nozzle to the exhaust nozzle wall measured at the jet exit;
• (d) providing a pressure source for producing a pressure differential between the jet and the interior of the centerbody downstream of the jet;
• and
• (e) regulating the pressure differential along the centerbody length to influence the rate of entrainment of the ambient fluid into the jet downstream of the exhaust nozzle.

A jet noise suppression device comprising:

• a jet exhaust nozzle;
• an elongated hollow member having a portion thereof fixed within said nozzle and a portion centrally extending in the jet downstream of said nozzle;
• said hollow member being of a substantially constant diameter along the length thereof;
• a porous wall serving as the exterior surface of said elongated hollow member on at least the portion thereof extending in the jet downstream of said nozzle;
• and,
• pressure means connected to said elongated hollow member, said pressure means serving to affect the static pressure in the jet through said porous wall to influence the rate of entrainment of ambient fluid into the jet downstream of said exhaust nozzle.

A noise suppression device for a jet operating in an ambient fluid comprising:

• a jet exhaust nozzle;
• means for influencing the rate of entrainment of ambient fluid into the jet emanating from said nozzle;
• said means including an elongated hollow porous nozzle plug centerbody member having a length thereof fixed within said nozzle and a length thereof extending downstream in the jet emanating from said jet exhaust nozzle;
• and
• pressure means connected to said porous centerbody member.

A device for suppressing noise in a jet flow containing at least one shock wave comprising:

• a jet exhaust nozzle;
• an elongated hollow porous member having a first length portion thereof fixed relative to the nozzle and a second length portion disposed within the jet flow extending downstream of said exhaust nozzle;
• and,
• pressure means connected to said porous member to provide a pressure differential between the jet flow and porous member, said pressure means serving to affect the static pressure in the jet downstrream of said exhaust nozzle by homogenous mixing of the differential pressures through said porous member to dissipate any shock waves emanating from within said exhaust nozzle.