Session: 01-04: Inlet Distortion and Engine Operability

Submission Number: 178449

Mixed Fidelity Method to Evaluate Circumferential and Radial Distortion in Integrated Multistage Compressor Systems 

Aircraft engines can be temporarily or permanently exposed to distorted inlet flow conditions for reasons such as flight mission segments causing asymmetric inflow, installation related ingestion of lower momentum fluid or engine integration behind curved inlet ducts. 
Even if the overall system operates in a quasi steady state, the individual rotating components experience a temporal change in their inflow conditions, leading to an unsteady work input and excitation of vibrations as the blade forces change.

In the early stages of the design process of the compressor components, uniform inflow conditions are commonly assumed to allow the use of steady state numerical methods and periodicity simplifications in order reduce the numerical effort. While this is a reasonable approach, when the initially, extensive boundaries of the compressor design space are being surveyed, it would be beneficial to include the distorted conditions into the design process early on to prevent a possible misdirected development caused by the uniformity assumption, especially for compressor systems that are supposed to operate under permanent distortions.

The inherent unsteady nature of the phenomenon requires the use of time resolving methods accompanied by their large need of numerical resources, that contradicts the desire to explore the design space by broad variation of multiple parameters.
A methodology developed at the DLR Institute for Propulsion Technology aims to combat this conflict by combining steady state RANS and a streamline curvature approach. This methodology was previously implemented and validated against time resolved numerical data for single stage turbofans. For this publication, it was expanded to multistage applications and an analysis of a 4.5 stage compressor rig was conducted. The results of the mixed fidelity analysis were validated against high fidelity uRANS data as well as experimental data that was recorded using the same compressor rig exposed to a total pressure inlet distortion.
It was found that the fundamental phenomenon of flow redistribution, the compressor internal stage wise attenuation of the total pressure distortion and the synchronous excitation of a total temperature distortion could be reproduced in the mixed fidelity method at a significantly reduced numerical cost. Specifically the flow conditions at the entry plane of the compressor are in very good agreement with the high fidelity data.

Presenting Author: David Kaiser DLR

Presenting Author Biography: from 2022: Research at DLR Institute of Propulsion, Topics: Compressor Design for Variable Cycle Engines, Compressor Design with Inlet Distortions

2019-2022: M.Sc. Mechanical Engineering at Karlsruhe Institute of Technology (Fluid Dynamics, Combustion Engine Systems)

2015-2019: B.Sc Mechanical Engineering at Karlsruhe Institute of Technology

Authors:

David Kaiser DLR
Maximilian Mennicken DLR
Georgios Goinis DLR