| Summary: | Experiments were conducted at low speed in a flat plate rig and a compressor cascade. The flat plate rig was used to optimise flow control by blowing with vortex generator jets. This study showed that a boundary layer separation could be prevented with the application of steady blowing at a jet velocity achievable in a real gas turbine compressor. Pulsed blowing was also studied, yielding a reduction in the injected mass flow rate of 40%, but required an increase in the injected jet velocity. The recommendations of the flat plate study were applied to a cascade in order to establish the performance impact of flow control by blowing with vortex generator jets in an environment more representative of a real compressor. Together with endwall control, flow control was found to remove a separation occurring at high incidence and reduce the profile loss coefficient at midspan by 67%. The skewed jets were, however, found to aggravate a corner separation occurring on the endwall of the cascade to which the jets were skewed, requiring additional endwall suction to be applied to yield a uniformly thin wake across the full blade span. For a blade with a representative aspect ratio, flow control by steady blowing with vortex generator jets was found to reduce the loss coefficient averaged over the full span by 20% relative to the uncontrolled case. In addition to blowing, flow control was also applied in the cascade rig in the form of boundary layer suction. Suction was found to reduce the loss coefficient averaged over the full span by 33% relative to the uncontrolled case. The optimal configurations identified were studied in terms of their impact on the engine cycle, when applied to reduce the solidity of a stator row. Flow control was found to enable a 35% reduction in the number of blades at no cost to compressor efficiency.
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