Performance Evaluation of an Axial Compressor With Modified Blades Using Leading Edge Tubercles

Abstract

Abstract The performance of a Rolls-Royce A250 gas turbine axial compressor was evaluated for four different compressor configurations employing a flow control device called leading-edge tubercles. The tubercle shape was selected based on optimization performed in a 2-D compressor cascade for the design conditions of a first stage compressor rotor blade. The A250 compressor was tested without flow control to establish its compressor map for baseline performance. Tubercle shape was manufactured onto the leading edge of each compressor blade using a technique called Sinker EDM. An operational axial compressor with tubercle-modified rotor and stator blades was tested. For the final configuration, a compressor with modified rotor blades only was tested. The fully modified compressor showed slight improvements in the pressure rise along with increased mass flow rate, with a slightly open bleed valve at the fifth stage. At high speeds, the modified compressor configurations were unable to improve performance over the baseline. However, subsequent analysis revealed encouraging affects on stability. High frequency pressure transducer results showed that in the baseline compressor, stall precursors appeared first at the first stage that then propagated downstream in the compressor. The modified compressor completely eliminated the presence of stall cell in the first stages. With flow control, the stall developed at the last stage before propagating upstream. The challenging blade modification method precluded careful finishing of tubercle edges. Degraded modified compressor performance is attributed to this. Leading-edge tubercles showed potential for their application on compressors, demonstrating slight performance improvement in some ranges of operation and the elimination of stall cells known to lead to complete compressor stall in the baseline compressor.