Investigation of the performance of a bifurcated turboprop engine inlet with propeller interference

The aerodynamic interaction between propeller slipstreams and bifurcated turboprop inlets is not yet fully understood, particularly concerning swirl distortion dynamics and unsteady pressure fluctuations caused by rotating propeller interference. This study combines wind tunnel experiments with sliding-mesh CFD simulations to investigate propeller-induced flow interference. High-frequency unsteady pressure sensors and five-hole probes with a 15° stepwise rotation were used to measure time-averaged and transient flow characteristics. Results indicate that increasing the propeller pitch angle from 40° to 50° raises the total pressure recovery coefficient σ by 0.25% but also increases the total pressure distortion DC60 by 40.4%. Similarly, increasing the propeller speed from 1500 r/min to 2000 r/min enhances σ by 0.34% while causing DC60 to rise by 51.4%. The propeller interference increases the swirl distortion., limiting swirl intensity to 3.43° at 4048 r/min under propeller rotation. This represents a 12.1% increase compared to the 3.06° swirl intensity observed when the propeller is absence. A dominant frequency of 240.3 Hz, corresponding to the blade-passing frequency of the 8-bladed propeller at 1800 r/min, was identified in the wall pressure fluctuations, confirming periodic flow interactions. These findings provide experimental and numerical evidence of the mechanisms behind propeller-induced swirl distortion in bifurcated inlets. The methodology and results directly support the design of advanced turboprop engines requiring improved aerodynamic stability and foreign object exclusion capabilities.