Leveraging Additive Manufacturing Design Strategies to Understand Vaned Diffuser Off-Design Performance

Abstract High-speed compressors for aircraft engines are required to maintain stable and stall-free operation across a wide range of operating conditions. As the operating point changes, the mass flow rate through the compressor changes and alters the flow structures in the blade passages. To design high efficiency compressors with the required stability margin, it is imperative to understand the unsteady flow physics through the blade rows. Non-intrusive measurement techniques enable characterization of the flow without influencing it. In small blade passages, like those found in centrifugal compressors, the use of non-intrusive techniques, such as high-frequency response pressure transducers and laser Doppler velocimetry, are critically important because traditional measurement techniques can cause larger flow disruptions. This investigation characterized the performance of an aeroengine centrifugal compressor vaned diffuser across the 100% design corrected speedline from the choke operating condition to a near-stall operating condition. Additive manufacturing was leveraged to implement instrumentation throughout the entire diffuser passage. A modular fixture for pressure transducers was manufactured via stereolithography to enable static pressure measurements on the diffuser case and vane surfaces. For the first time in the open literature, AM-enabled measurements of steady-state and unsteady static pressures were acquired on the diffuser vane surface to calculate aerodynamic vane loading and to study the streamwise progression of the diffusion process. Additionally, unsteady velocity vector data were acquired in the vaneless space of the compressor via three-component laser Doppler velocimetry to measure diffuser vane incidence. The diffuser incidence data were then correlated to aerodynamic vane loading, static pressure recovery, and diffuser effectiveness to understand the effect of the inlet flow on component performance across the compressor speedline.