Influence of Wake Sweeping Frequency on the Unsteady Flow Characteristics of an Integrated Aggressive Interturbine Duct

Abstract

A dynamic simulation was launched to research the influence of high-pressure turbine (HPT) rotor wake passing frequency on the flow mechanism in an integrated aggressive interturbine duct (AITD). Sweeping rods were adopted to replace the HPT rotors to decouple the influence of its wake from those of other secondary flows. The diameter of the rods (d/s, nondimensionalized by the pitch (s) of the integrated struts at midspan) was 0.10, and their reduced frequency (f) ranged from 0.49 to 1.61. The k–ω SST turbulence model and γ–θ transition model were adopted for the turbulence closure. A 6.3-million-node structured grid was used to meet the grid dependency. Along with increasing f, the intensified circumferential motion of the wake (1) enhances the wake vortex stretching and exhaustion near the hub; (2) promotes the radial inclination of wakes and elongates and narrows the wake vortex band, resulting in increased spacing between the adjacent wake vortices and the weakened vortex interaction. In the high-f cases, the enhanced turbulence intensity in the interval between the adjacent wakes could suppress the separation bubble on LPT-GV in advance, but the elongated and narrowed wake vortices resulted in a substantial reduction in the radial extent and duration of their suppression on the separation bubble. Therefore, the influence of f on the integrated AITD and its parts was bidirectional, and adjusting the sweeping frequency to balance its positive and negative effects could minimize the total loss in the integrated AITD.

Keywords

• interturbine transition duct
• sweeping rods
• boundary layer transition
• unsteady flow