Compact, High Performance Compressor Diffusers for Small Gas Turbine Engines Requiring a Wide Operating Range

Low cost compact diffusers are needed for small gas turbine compressor stages to economically minimize centrifugal compressor overall diameter yet permit high efficiency and wide operating range. The proposer has performed over 130 different detailed tests (on more than 40 different stage configurations) with various conventional and novel diffusers (vaneless, low solidity airfoil, channel, tandem, and twisted diffusers; but not pipe diffusers). These tests were performed to systematically improve centrifugal compressor diffuser performance. The Phase I objective is to determine the feasibility for pipe diffusers to improve the efficiency and operating range of small gas turbine engines within an optimized radial space and at a reduced cost. Pipe diffusers will be designed and tested in Phase I (making use of an existing test rig for cost and data consistency advantages). Performance data will be compared to existing data (from the same basic rig) for other diffuser types. A cost index will be established for each diffuser type. The resultant summary matrix of geometric, performance, and cost data will be used to assess the feasibility of improving compact diffuser performance and cost. In Phase II, optimum compact, high performance, low cost diffusers would be designed and tested for specific Army applications. There is a controversy surrounding pipe diffusers for applications requiring wide operating range and high efficiency. Due to potential cost advantages with pipe diffusers, there is a significant market opportunity if both efficiency and range are improved. Immediate applications are small gas turbines in aircraft, power co-generation, and ground vehicle services (as well as refrigeration and turbochargers).