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A apparatus and method for improving combustion by improving at least one of temperature distribution in the combustor, pressure distribution around the combustor and combustion noise level in the combustor, by redistributing air around the combustor to modify the structure of the air flow prior to

A apparatus and method for improving combustion by improving at least one of temperature distribution in the combustor, pressure distribution around the combustor and combustion noise level in the combustor, by redistributing air around the combustor to modify the structure of the air flow prior to entry into the combustor.

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I claim: 1. A gas turbine engine comprising: a combustor portion including at least one combustor, the combustor having a plurality of holes therein for admitting combustion air into the combustor; a casing defining at least one chamber therein, the chamber containing the combustor and a volume of

I claim: 1. A gas turbine engine comprising: a combustor portion including at least one combustor, the combustor having a plurality of holes therein for admitting combustion air into the combustor; a casing defining at least one chamber therein, the chamber containing the combustor and a volume of air around at least a portion of the combustor; a compressor portion communicating with the chamber via a compressor diffuser outlet for delivering compressed air to the chamber for subsequent admission into the combustor; and a ring extending into the chamber substantially continuously around the chamber so as to extend partially into an air flow exiting the compressor diffuser outlet into the chamber, the ring sized and positioned in the chamber to cause a step change in direction and pressure of at least a portion of the air flow, the step change adapted to effect a redistribution of air around the combustor to thereby achieve at least one of reduced combustion noise and more uniform temperature distribution in the combustor. 2. The gas turbine engine of claim 1, wherein the step change in pressure is a pressure drop not greater than an air flow pressure drop calculated to occur across the combustor in an equivalent gas turbine engine, the equivalent gas turbine being identical to the gas turbine engine except equivalent gas turbine is without a ring of the type claimed in claim 1. 3. The gas turbine engine of claim 1, wherein the ring extends from a wall of the chamber. 4. The gas turbine engine of claim 1, wherein the ring extends substantially radially into the air flow. 5. The gas turbine engine of claim 1, wherein the ring includes a bevelled inner periphery on a side facing the compressor outlet. 6. The gas turbine engine of claim 1, wherein the ring is secured between an upstream section and a downstream section of the casing. 7. The gas turbine engine of claim 1, wherein the ring is disposed in the chamber so as to be closer to the compressor outlet than it is to substantially all of said holes in the combustor. 8. An apparatus for improving combustion in a gas turbine engine, the gas turbine engine comprising at least a compressor portion, a combustor and a chamber housing the combustor, the compressor portion having a compressor diffuser outlet interfacing with the chamber for delivering a flow of compressed air to the chamber, the combustor having holes therein interfacing with the chamber and adapted to permit air in the chamber to enter the combustor for combustion, the apparatus comprising: means positioned fluidly intermediate the compressor diffuser outlet and the combustor extending partially into the compressed air flow exiting the compressor diffuser outlet for aerodynamically tripping the compressed air flow entering the chamber to thereby create a step change in the air flow prior to entry into the combustor, said means adapted to thereby decouple acoustic and hydraulic fluctuation components in the air flow prior to entry of the air flow into the combustor. 9. The apparatus of claim 8, wherein step change is at least one of a direction change and an increase in pressure drop. 10. The apparatus of claim 8, wherein the means for aerodynamically tripping the air flow extends partially into the air flow. 11. A gas turbine engine comprising: a gas generator portion including at least a compressor diffuser, a combustor and a chamber around the combustor, the gas generator portion in use having an air flow from the compressor diffuser entering the chamber and guided thereby to the combustor, the air flow providing a source of combustion air to the combustor; and at least one trip disposed in the chamber at a location fluidly intermediate the compressor diffuser and the combustor, the trip extending into the air flow substantially transversely relative to an initial direction of the air flow in the chamber, the trip adapted in use to create a predetermined step change increase in pressure drop of the air flow to thereby effect a predetermined air flow redistribution in the chamber, said air flow redistribution predetermined to improve at least one of an air pressure distribution outside the combustor and a fluctuation phase shift in the air flow adapted to reduce combustion noise. 12. The gas turbine engine of claim 11, wherein the step change increase in pressure drop is not greater than a predetermined pressure drop, the predetermined pressure drop being equivalent to a pressure drop in the air flow caused by the combustor in the same gas turbine engine when the gas turbine is operated without the at least one trip. 13. The gas turbine engine of claim 11, wherein the air flow redistribution comprises a redistribution of local pressure drop around the combustor. 14. The gas turbine engine of claim 11, wherein the air flow redistribution comprises a redistribution of air flow around the combustor. 15. The gas turbine engine of claim 11, wherein the air flow redistribution is adapted to decouple pressure fluctuations in the air flow prior to entry of the air flow into the combustor. 16. The gas turbine engine of claim 11, wherein the air flow redistribution is adapted to redirect a greater portion of the air flow towards a radially inner side of the combustor. 17. The gas turbine engine of claim 11, wherein the at least one trip extends into the chamber from an inner side of a radially outer wall of the chamber. 18. A method for improving at least one of a temperature distribution and a combustion noise level in a combustor of a combustion system, the combustion system having an air source for providing a flow of compressed air to a chamber housing the combustor, the combustor having holes therein for admitting the compressed air into the combustor for combustion therein when mixed with fuel and ignited, the method comprising the step of: aerodynamically tripping the flow of compressed air downstream of an entry point for said air into the chamber and before the flow of air enters the combustor, the step of tripping adapted to impart at least a step change in pressure drop of at least a portion of the flow of air, the step change adapted to decouple fluctuation components in the flow of air prior to entry of the air into the combustor. 19. A method of providing a gas turbine engine, the method comprising the steps of: determining a configuration for a compressed air system, a combustor and a casing chamber surrounding the combustor, the configuration including an air flow path from compressed air system through the casing chamber and into the combustor; determining an initial operating air pressure distribution occurring in the compressed air in the chamber around the combustor; determining a desired air pressure redistribution in the compressed air in the chamber around the combustor, the redistribution adapted to provide at least one of reduced combustion noise and improved temperature distribution in the combustor; and introducing an intervention in the casing chamber, the intervention extending into the flow path and adapted to effect the determined air pressure redistribution. 20. The method of claim 19, wherein the intervention causes a step change in air delivered from the compressed air system to casing chamber. 21. The method of claim 19, wherein the step change includes a discontinuous increase in pressure drop. 22. The method of claim 21, wherein the increase in pressure drop is not greater than a calculated pressure drop across a combustor in a comparable gas turbine engine, the comparable gas turbine engine being free from said intervention in the casing chamber. 23. A method of improving combustion, the method comprising the steps of: providing a compressed air flow, the compressed air flow having an acoustic and hydrodynamic structure imposed during a compression process; restructuring the acoustic and hydrodynamic structure to provide a preselected second acoustic and hydrodynamic structure, the second structure preselected to cause an acoustic and hydrodynamic phase shift in at least a portion of the compressed air flow, the phase shift being selected and adapted to reduce combustion noise; providing the restructured compressed air flow to a combustor for use in combustion. 24. A method of improving combustion in a gas turbine engine, the method comprising the steps of: selecting a gas turbine engine, the engine having at least a compressor providing a source of compressed air, a combustor and a chamber surrounding the combustor, the compressor, chamber and combustor in serial fluid communication for transmitting the air from the compressor to the combustor for combustion; and modifying the gas turbine engine by inserting at least one aerodynamic trip into the chamber, the trip adapted to effect at least one of a pressure redistribution around the combustor and a phase shift in pressure fluctuations in at least a portion of the air in the chamber, the phase shift adapted to reduce combustion noise.