Passive exhaust suppressor and method
View Patent ↗A passive exhaust system is described that provides effective infrared signature suppression without affecting radar cross-section while maintaining stable function in crosswinds. A passive exhaust system may include an array of ducts with each duct having a primary and secondary nozzle. Central ducts draw in ambient cooling air to create a thick cooling film along exterior surfaces and cause plume dilution, stabilize the plume flow in a crosswind, and prevent heating of visible surfaces. Visible surfaces may incorporate radar absorbing materials and may be inclined at an angle or fabricated with a diffuse surface to prevent specular reflection. Visible surfaces may be constructed from or covered with low infrared emissivity materials. A variable passive flow controller ensures a sufficient velocity exhaust flow.
1. A passive exhaust suppressor, comprising:
an array of at least three ducts, each duct comprising:
a primary nozzle; and
a secondary nozzle, wherein at least one duct of said array comprises one of said secondary nozzles having internal side with a convex contour and positioned at the exit of one of said primary nozzles to effect exhaust exiting said one of said primary nozzles and substantially directed at a tangent to said convex contour to attach to said convex contour of said internal side of said one of said secondary nozzles; and
a shroud, positioned around the array of ducts to create an inlet adjacent to said primary nozzles and an exit plane located so that each of said secondary nozzles are positioned within said shroud.
2. The passive exhaust suppressor of claim 1 , further comprising a view-blocking framework positioned around said secondary nozzles to block the view from around said shroud at a view angle below a maximum elevation view angle of said sides of said secondary nozzles to which exhaust has attached.
3. The passive exhaust suppressor of claim 2 , wherein said view-blocking framework comprises view blockers between at least some of said nozzles of said array.
4. The passive exhaust suppressor of claim 2 , further comprising radar suppression materials covering at least a portion of a visible surface of said view-blocking framework.
5. The passive exhaust suppressor of claim 2 , further comprising infrared suppression materials covering at least a portion of a visible surface of said view-blocking framework.
6. The passive exhaust suppressor of claim 1 , further comprising a passive flow controller in fluid communication with at least one of said primary nozzles.
7. The passive exhaust suppressor of claim 6 , wherein said flow controller comprises a weighted plate wherein the weight of said plate is selected to provide at least a minimum velocity of exhaust passing through said nozzle.
8. The passive exhaust suppressor of claim 7 , wherein said weighted plate is hinged and recessed into a wall of said nozzle.
9. The passive exhaust suppressor of claim 6 , further comprising a passive flow controller in each of said primary nozzles.
10. The passive exhaust suppressor of claim 1 , wherein said array of ducts comprises six primary nozzles and six secondary nozzles in a three-by-two pattern.
11. The passive exhaust suppressor of claim 1 , wherein said array of ducts defines at least one interior duct providing a lower pressure at the interior of an exit plane of said array than the pressure provided by exterior ducts at the exterior of the exit plane of the array for stabilizing an exhaust plume exiting said secondary nozzles.
12. The passive exhaust suppressor of claim 1 , wherein said secondary nozzles are positioned at the exits of said primary nozzles to permit the induction of cooling air into the secondary nozzles and to create a film of cooling air along the exterior surface of said secondary nozzles, wherein the cooling air is colder than the exhaust.
13. The passive exhaust suppressor of claim 1 , further comprising radar suppression materials covering at least a portion of a visible surface of at least one of said ducts and said shroud.
14. The passive exhaust suppressor of claim 1 , further comprising infrared suppression materials covering at least a portion of a visible surface of at least one of said ducts and said shroud.
15. A gas propulsion system in a ship comprising a gas turbine engine and a passive exhaust suppressor of claim 1 for receiving exhaust from said gas turbine engine.
16. The gas propulsion system of claim 15 , wherein said ship is a naval combat ship.
17. A passive exhaust suppressor, comprising:
an array of at least three ducts, each duct comprising:
a primary nozzle; and
a directing surface, wherein at least one duct of said array comprises one of said directing surfaces having an internal side with a convex contour and positioned at the exit of one of said primary nozzles to effect exhaust exiting said one of said primary nozzles and substantially directed at a tangent to said convex contour to attach to said convex contour of said internal side of said one of said directing surfaces; and
a shroud, positioned around the array of ducts to create an inlet adjacent to said primary nozzles and an exit plane located so that each of said directing surfaces are positioned within said shroud.
18. A passive exhaust suppressor, comprising:
an array of at least three ducts, each duct comprising:
a primary nozzle; and
a secondary nozzle positioned at the exit of said primary nozzle to permit the induction of cooling air into the secondary nozzle, wherein said array defines at least one interior duct and at least two exterior ducts, wherein at least one of said interior ducts is configured to provide a lower pressure at the interior of an exit plane of said array than the pressure provided by exterior ducts at the exterior of the exit plane of the array and for stabilizing an exhaust plume exiting said secondary nozzles, and wherein the cooling air is colder than the exhaust of the exhaust plume; and
a shroud, positioned around the array of ducts to create an inlet adjacent to said primary nozzles and an exit plane located so that each of said secondary nozzles are positioned within said shroud.
19. The passive exhaust suppressor of claim 18 , wherein said at least one of said interior nozzles comprises an exit plane terminating noncontiguously with exit planes of said exterior ducts.
20. The passive exhaust suppressor of claim 19 , wherein said at least one of said interior nozzles comprises a primary nozzle with an exit plane terminating noncontiguously with exit planes of primary nozzles of said exterior ducts.
21. The passive exhaust suppressor of claim 19 , wherein said at least one of said interior nozzles comprises a secondary nozzle with an exit plane terminating noncontiguously with exit planes of secondary nozzles of said exterior ducts.
22. The passive exhaust suppressor of claim 18 , wherein said at least one of said interior nozzles is configured to emit exhaust having a higher velocity than exhaust exiting said exterior ducts.