Pressure-gain combustion apparatus and method

Abstract

A pressure gain combustor comprises a detonation chamber, a pre-combustion chamber, an oxidant swirl generator, an expansion-deflection (E-D) nozzle, and an ignition source. The detonation chamber has an upstream intake end and a downstream discharge end, and is configured to allow a supersonic combustion event to propagate therethrough. The pre-combustion chamber has a downstream end in fluid communication with the detonation chamber intake end, an upstream end in communication with a fuel delivery pathway, and a circumferential perimeter between the upstream and downstream ends with an annular opening in communication with an annular oxidant delivery pathway. The oxidant swirl generator is located in the oxidant delivery pathway and comprises vanes configured to cause oxidant flowing past the vanes to flow tangentially into the pre-combustion chamber thereby creating a high swirl velocity zone around the annular opening and a low swirl velocity zone in a central portion of the pre-combustion chamber. The E-D nozzle is positioned in between the pre-combustion chamber and detonation chamber and provides a diffusive fluid pathway therebetween. The ignition source is in communication with the low swirl velocity zone of the pre-combustion chamber. This configuration is expected to provide a combustor with a relatively low total run-up DDT distance and time, thereby enabling high operating frequencies and corresponding high combustor performance.

What is claimed is: 
     
         1 . A pressure gain combustor comprising:
 a detonation chamber having an upstream intake end and a downstream discharge end, the detonation chamber being configured to allow a supersonic combustion event to propagate therethrough;   a pre-combustion chamber having a downstream end in fluid communication with the detonation chamber intake end, an upstream end in communication with a fuel delivery pathway, and a circumferential perimeter between the upstream and downstream ends and having an annular opening in communication with an annular oxidant delivery pathway;   an oxidant swirl generator in the oxidant delivery pathway and comprising vanes configured to cause oxidant flowing past the vanes to flow tangentially and turbulently into the pre-combustion chamber thereby creating a high swirl velocity zone around the annular opening and a low swirl velocity zone in a central portion of the pre-combustion chamber;   an expansion-deflection (E-D) nozzle in between the pre-combustion chamber and detonation chamber and providing a diffusive fluid pathway therebetween; and   an ignition source in the low swirl velocity zone of the pre-combustion chamber.   
     
     
         2 . A pressure gain combustor as claimed in  claim 1  wherein the fuel delivery pathway has an opening sized to atomize fuel discharged into the pre-combustion chamber. 
     
     
         3 . A pressure gain combustor as claimed in  claim 2  wherein the fuel delivery pathway opening is communicative with the high swirl velocity zone of the pre-combustion chamber. 
     
     
         4 . A pressure gain combustor as claimed in  claim 1  wherein the vanes of the swirl generator are helically arranged in the annular oxidant delivery pathway. 
     
     
         5 . A pressure gain combustor as claimed in  claim 1  wherein the E-D nozzle comprises
 a generally cylindrical body with an internal bore having a downstream end in fluid communication with the detonation chamber, an upstream end, and at least one circumferentially disposed port in the body that is in fluid communication with the bore; 
 an annular rim extending outwards from the body and which contacts an outer rim of the detonation chamber's intake end; 
 a generally cylindrical cowling that extends from the annular rim past an upstream end of the cylindrical body such that an annular space is defined between the cowl and the cylindrical body; and 
 an end plate at the upstream end of the bore and having at least one diffuser channel extending through the plate and providing fluid communication between the bore and the pre-combustion chamber; 
 wherein the diffuser channel and port provide the diffusive pathway between the pre-combustion chamber and the detonation chamber. 
 
     
     
         6 . A pressure gain combustor as claimed in  claim 5  wherein the cowling has a mantle with a partial toroidal form and which extends into the pre-combustion chamber and into sufficient proximity with the annular opening thereof to create a Coanda effect which deflects tangentially flowing oxidant radially inwards towards the center of the pre-combustion chamber. 
     
     
         7 . A pressure gain combustor as claimed in  claim 6  wherein the end plate comprises a plurality of diffuser channels, each of which extend at an angle outwardly from the bore such that each channel is directed toward an inside surface of the cowling and not the pre-combustion chamber. 
     
     
         8 . A pressure gain combustor as claimed in  claim 7  further comprising an end cap defining the upstream end of the pre-combustion chamber, and comprising the fuel delivery pathway and an ignition port opening into a central portion of the pre-combustion chamber and in communication with the ignition source. 
     
     
         9 . A pressure gain combustor as claimed in  claim 1  wherein the ignition source is selected from the group consisting of an electrical spark discharge source, a plasma pulse source, and a laser pulse source. 
     
     
         10 . A pressure gain combustor as claimed in  claim 1  further comprising an expansion chamber in fluid communication with the oxidant delivery pathway between the pre-combustion chamber and an oxidant inlet, wherein the expansion chamber has a volume selected to reduce backpressure of back flow into the expansion chamber to a desired static pressure that is less than an oxidant pressure at the oxidant inlet. 
     
     
         11 . A pressure gain combustor as claimed in  claim 10  further comprising a pre-heat chamber thermally coupled to the detonation chamber and an oxidant plenum chamber in fluid communication with the pre-heat chamber and the oxidant inlet. 
     
     
         12 . A pressure gain combustor as claimed in  claim 11  wherein the oxidant plenum chamber comprises a frusto-conical deflector shell that defines a sinuous oxidant delivery pathway inside the oxidant plenum chamber and which serves to impede backflow of combustion products and backpressure caused by detonation shockwaves. 
     
     
         13 . A method of operating a pressure gain combustor comprising:
 tangentially and turbulently flowing an oxidant into a pre-combustion chamber to form a high swirl velocity zone at an outer portion of the pre-combustion chamber and a low swirl velocity zone at an inner portion of the pre-combustion chamber;   injecting fuel into the high swirl velocity zone of the pre-combustion chamber;   flowing a mixture of the fuel and oxidant into a detonation chamber in fluid communication with the pre-combustion chamber;   after a selected dwell period, igniting the fuel and oxidant in a low velocity swirl zone of the pre-combustion chamber to form a flame kernel, and   directing a flame front formed from the flame kernel though an expansion-deflection (E-D) nozzle into the detonation chamber such that oxidant and fuel in the detonation chamber is detonated, causing a supersonic combustion event wherein the flame front becomes coupled to a shock wave and propagates through the detonation chamber at sonic velocities.   
     
     
         14 . A pressure gain combustor comprising:
 a detonation chamber having an upstream intake end and a downstream discharge end, the detonation chamber being configured to allow a supersonic combustion event to propagate therethrough;   a pre-combustion chamber in fluid communication with the detonation chamber intake end and in fluid communication with a fuel delivery pathway and an oxidant delivery pathway;   an ignition source in the pre-combustion chamber and positioned to ignite a fuel/oxidizer mixture therein;   an expansion-deflection (E-D) nozzle in between the pre-combustion chamber and detonation chamber and comprising a diffusive fluid pathway configured to be less restrictive to fluid flow in a downstream direction than in an upstream direction.   
     
     
         15 . A pressure gain combustor as claimed in  claim 14  wherein the E-D nozzle comprises:
 a generally cylindrical body with an internal bore having a downstream end in fluid communication with the detonation chamber, an upstream end, and at least one circumferentially disposed port in the body that is in fluid communication with the bore; 
 an annular rim extending outwards from the body and which contacts an outer rim of the detonation chamber's intake end; 
 a generally cylindrical cowling spaced from the body and which extends from the annular rim and past an upstream end of the cylindrical body and terminating with a radially and inwardly curved mantle such that an annular space is defined between the cowling and the cylindrical body; and 
 an end plate at the upstream end of the bore and having at least one diffuser channel extending through the plate, wherein the at least one diffuser channel extends at an angle such that the channel is coupled to the bore and directed at the cowling; 
 wherein an upstream fluid flow is more restrictive than the downstream fluid flow due to the cowling directing at least a portion of upstream fluid flow from the channels into the annular space thereby interfering with upstream fluid flow that flows into the annular space via the port. 
 
     
     
         16 . A pressure gain combustor as claimed in  claim 15  wherein the mantle has a partial toroidal form and which extends into the pre-combustion chamber into sufficient proximity with the oxidant delivery pathway to create a Coanda effect which deflects tangentially flowing oxidant in an outer region of the pre-combustion chamber radially inwards towards a central region of the pre-combustion chamber.