Internal Flow Characteristics and Aerodynamic Noise Suppression of Serrated Trailing Edge Rotor Blades in an Axial-flow Turbine

The effects of rotor-stator interactions induce complex wake disturbances in turbine blades, and the use of a serrated trailing edge (STE) has been recognized as an effective flow control strategy. In this study, STEs were applied to the rotor blades of an AACHEN 1.5-stage axial-flow turbine, and it was to investigate the impact of the STEs on the aerodynamic and acoustic performance. Detached eddy simulation (DES) was employed to analyze the internal flow characteristics for different serration configurations. The results indicated that an STE could effectively improve the wake velocity of the rotor blade. The growth rate of the wake velocity reached 40.18% at the serration tip and 21.23% at the serration root, indicating improvements throughout the serrated region. Additionally, the STE rotor blades enhanced the flow mixing and generated rotational vortex structures between the serration peaks and valleys while maintaining the original aerodynamic performance. These vortices facilitated energy exchange between low-speed and high-speed regions, thereby reducing the wake vortex intensity. Furthermore, pressure fluctuations were effectively suppressed by the effect of the STE rotor blades, leading to a significant noise reduction, with the sound pressure level (SPL) reduced by approximately 8.52 dB in the low-frequency range and 12.49 dB in the high-frequency range. These findings confirmed that the STE blade improved both aerodynamic and acoustic characteristics. Thus, this study provides valuable insights for turbine blade design optimization and noise reduction strategies.