TECHNOLOGY AREAS: Air Platform, Ground/Sea Vehicles, Materials/Processes

OBJECTIVE: Investigate passive combustion control techniques such as porous matrix inserts in the combustion chamber to reduce combustion-generated noise, thereby reducing the audible noise spectrum from turbine engines used for propulsion of aircrafts and weapons.

DESCRIPTION: Combustion instabilities and the resulting pressure oscillations that lead to excessive noise could produce degradation in performance and ultimately excessive vibrations and failure of the propulsion system. A number of investigations have addressed active control of combustion instability, and the exhaust noise from jet engines, and several passive combustion control technologies have focused on emission control. Some of the techniques investigated earlier can have a profound effect on noise control if properly modified. Pours matrix insert in turbine engine combustors have shown to produce a uniform temperature distribution (pattern factor) and reduced emissions, and elimination of hot spots. Techniques like this will have an impact on noise reduction as well because they also address some of the factors that lead to excessive combustion-generated noise. Since they do not require elaborate sensors and actuators and feed back control systems, the modifications to be implemented will be simple, cost-effective and reliable.

PHASE I: Design and fabricate (or procure) porous inserts and test simple combustor configuration (cylindrical/backward step) with the inserts placed in appropriate locations and determine the combustion noise reduction. Evaluate the dependence of noise reduction on location, thickness etc. of the inserts. For other passive control techniques also, determine the parametric dependence of noise reduction.

PHASE II: From the information obtained in Phase I, design and fabricate the components required for insertion/conversion of an existing small turbine engine. Perform elaborate parametric testing and prepare noise reduction spectrum over extended frequency range at various ambient conditions of pressure temperature and velocity. Evaluate dependency of the technology on the fuel used. Develop computational tools for performance evaluation, prediction and optimization.

PHASE III: Design, fabricate and package the new components to be added in a government-provided full size engine. Perform comprehensive tests to evaluate the effectiveness of the technique in overall sound pressure level reduction as well as in the audible spectra. Validate the computational model developed in Phase II with the performance parameters obtained in Phase III. Extend the prediction capability to other specific engines and configurations, and make the models available as user-friendly codes. Provide a test matrix for the integrated system operation.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Application of passive combustion control to combustion could prove to be one of the most effective, simple and reliable methodology for noise control and reduction. Further, techniques such as porous inserts improve performance of the turbine engine by providing uniform combustion, reducing combustion oscillations and emissions. Reduction in combustion-generated vibrations and elimination of hot spots increase the engine life and consequently maintenance cost will be reduced. The technology developed here can be applied to commercial aircrafts, ship propulsion and service engines, as well as land-based turbine engines. Aircraft engine and aircraft manufactures, surface ship builders and the power industry will benefit from this program. Existing engines may also be retrofitted with passive combustion control with multiple benefits.

REFERENCES:
1. Witton, J.J. and E. Noordally, "Porous Media Burners for Clean Engines", Combustion Processes in Propulsion (Gabriel D. Roy, Ed.), Academic Press/Elsevier, 2005, pp. 139-144
2. Ellzey, J.L., A.J. Barra, and G. Diepvens, "Simulations of a Porous Burner for a Gas Turbine", Combustion Processes in Propulsion (Gabriel D. Roy, Ed.), Academic Press/Elsevier, 2005, pp. 145-156
3. Singh, S. and R.E. Peck, "An Innovative Method for Reducing Gaseous Emissions from Power Turbine Combustors", Advances in Chemical Propulsion (Gabriel D. Roy Ed.) CRC Press, 2002, pp. 463-476

KEYWORDS: Combustion control; noise reduction; turbine engines; porous inserts; pattern factor; audible spectra; aircrafts; weapons

TPOC: Gabriel Roy
Phone: (703)696-4406
Fax: (703)696-2558
Email: [email protected]
2nd TPOC: Gil Graff
Phone: (703)588-0703
Fax: (703)696-4274
Email: [email protected]

** TOPIC AUTHOR (TPOC) **

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