The current study investigates the flow physics resulting from a large tip clearance in a one-and-a-half stage axial compressor. The study aims to understand how the complex nature of rotor tip leakage flow affects compressor performance with a tip gap size of more than 4–5% of the rotor span, which is typical of advanced small core engines.&nbsp; The primary objective of the current investigation is to understand why some advanced flow simulation tools miscalculate compressor performance with large rotor tip gaps.&nbsp;Flow structure in the rotor tip region is complex with several&nbsp;&nbsp; dominant vortical structures with opposite rotation, resulting in inhomogeneous and highly anisotropic turbulence. Earlier measurements show that eddy viscosity is negative over large parts of the tip region and eddy viscosity varies among stress/strain components. &nbsp;&nbsp;The current study applies Unsteady Reynolds-averaged Navier-Stokes (URANS) and Large Eddy Simulation (LES) techniques to calculate the pressure rise in a one-and-a-half stage low speed axial compressor with a large rotor tip gap (5.5% of the rotor span). Calculated flow fields from the two different approaches are compared with available measurements and examined in detail.&nbsp;LES calculates the pressure rise in the present compressor fairly well, while URANS with a standard turbulence closure model underpredicts the pressure rise by 10-20% of the measured values. The current study shows that URANS predicts much lower tangential momentum of the tip gap flow compared to measurements.&nbsp;It appears that this effect is amplified with rotor tip gap size when a constant eddy viscosity is used over the entire tip region in the simulation.&nbsp;

Flow Physics in a Large Rotor Tip Gap in a Multi-Stage Axial Compressor

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

Turbo Expo 2021

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.