Session: 31-03 Compressor Inlet Distortion

Paper Number: 153169

Performance and Secondary Flow Structures Characterization in a Highly-Loaded Low-Pressure Compressor Under Distorted Inflow Conditions 

Advanced aircraft technologies are currently in the focus of research to address the environmental goal of reducing aircraft emissions within the next decade and beyond. Short-Nacelle High-Bypass (SNHB) turbofans and Boundary Layer Ingestion (BLI) engines stand out as promising solutions to enhance fuel and propulsive efficiency in the short and long term respectively. However, these engines are forced to operate under highly-distorted inlet flows such as crosswind and high inlet incidence operations. The complex flow pattern observed behind the fan demonstrates how the distortion can propagate within the downstream components of the engine and in particular through the low-pressure core, possibly jeopardizing performance and stability of the whole engine.

A highly loaded 1.5-stage axial compressor representative of the first stage of a modern booster was tested in the VKI-R4 facility with an inlet total pressure distortion replicating realistic engine installation effects. Performance was initially assessed over a broad speed range. Given the significant impact of the distortion on the stage operability, particularly at high speeds, the flow features responsible for the observed performance loss were identified and characterized. To this end, time-averaged and time-resolved measurements were employed to gain a comprehensive understanding of the involved physical phenomena. Additionally, URANS simulations of the full-stage domain were performed to characterize the distortion transfer mechanisms and support the experimental results in regions of difficult instrumentation access. These results were then compared with the clean configuration to quantify and assess the impact of the distortion.

Unlike typical cases where only an intensification of secondary flows is observed, the present stage reacted critically to the inlet distortion, exhibiting a strong performance reduction without the appearance of rotating stall. This behaviour was attributed to a severe rotor unbalance and to the propagation of critical flow structures within the distorted region, especially when the stage was operated near the stall boundary. Along with the performance and flow field characterization in distorted conditions, this paper aims to address the limitations of existing methods and tools used for the analysis of traditional machines under severe inlet total pressure distortions.

Presenting Author: Riccardo Toracchio von Karman Institute for Fluid Dynamics

Presenting Author Biography: Riccardo Toracchio is currently working as engineer in the Turbomachinery Department of the von Karman Institute for Fluid Dynamics. He earned his master degree in Mechanical Engineering from the University of L'Aquila, Italy, and began his PhD program at VKI, in collaboration with the University of Liège, in 2019, focusing on experimental and numerical analysis of low-pressure compressors operating under highly-distorted conditions.

Authors:

Riccardo Toracchio von Karman Institute for Fluid Dynamics
Koen Hillewaert University of Liège
Fabrizio Fontaneto von Karman Institute for Fluid Dynamics