Session: 31-02 Transonic Flow

Paper Number: 126672

126672 - Influence of Engine Conditions on the Performance Prediction of a Two-Stage Transonic Low Pressure Compressor 

The combination of rising operating costs and the necessity to reduce climate-affecting emissions is placing continuously increasing demands on the efficiency of modern aircraft engine compressors. Thereby, the inclusion of real engine operating conditions in the flow-optimized development of individual compressor components is of large importance. The derivation of application-driven impact factors on the performance of real engine compressors is therefore an essential prerequisite for the development of efficiency-enhanced compressor concepts. This study intends to extend the knowledge of the sensitivity of compressor operation simulation on real-engine design conditions, by investigating the impact of upstream and downstream engine components on the prediction of compressor map characteristics.

The investigations are conducted on a two-stage transonic low pressure compressor (LPC) of an unmixed low bypass ratio turbofan engine. The division of the engine mass flow into core and bypass mass flow is located directly downstream of the tandem stator of the second LPC stator row.

Results of Reynolds Averaged Navier Stokes simulations (RANS) using the turbomachinery flow solver TRACE are presented. Starting from the basic test case of a compressor operation under non-disturbed and homogeneous boundary conditions, the compressor is systematically subjected to aerodynamic conditions deriving from the compressor positioning downstream of the engine intake and upstream of the bypass splitter. The focus is placed on the effect of the intake boundary layer on compressor aerodynamics, the need for a representation of the spinner geometry in numerics and the impact of a two-part throttling condition resulting from the downstream presence of the high-pressure compressor and the bypass nozzle.

The analysis focuses on both global compressor map characteristics and the causal relations in local aerodynamics, in terms of a radial redistribution of the blade loading, local resistance against flow separation and the role of stage interaction depending on the distinguished engine conditions. A quantitative sensitivity analysis shows the corresponding influence and demonstrates the need to prescribe boundary conditions referring to the upstream and downstream engine installation situation in compressor numerics.

The simulations were performed for two different spool speeds representing an operation of the LPC at design and off-design condition. The design speed features a transonic relative rotor blade tip inflow, whereas the second speed studied corresponds to a subsonic inflow in all compressor stages. The discussion is oriented toward the different necessities for a consideration of real engine compressor installation conditions in transonic and subsonic flow regimes and the resulting implications on the compressor map prediction.

Presenting Author: Julian Alexander Scheibel University of the Bundeswehr Munich, Department of Aerospace Engineering, Institute of Jet Propulsion

Presenting Author Biography: 10/2012 - 07/2016: Bachelor´s degree - Mechanical Engineering at Technical University of Munich
10/2016 - 04/2019: Master´s degree - Aerospace Engineering at Technical University of Munich
since 05/2019: Research assistant at Institute of Jet Propulsion at University of the Bundeswehr Munich

Julian Scheibel is currently Ph.D. student at the Institute of Jet Propulsion in the CFD group. His areas of focus in research are numerical investigations of transonic turbo compressors and highly bent intake ducts. This includes FSI/CHT simulations of turbomachinery components, investigations of injector geometries for active flow control measures and, in particular, the numerical resolution of flow phenomena close to the surge line by stepwise implementation of more advanced numerical methods.

Authors:

Julian Alexander Scheibel University of the Bundeswehr Munich, Department of Aerospace Engineering, Institute of Jet Propulsion
Marcel Stößel University of the Bundeswehr Munich, Department of Aerospace Engineering, Institute of Jet Propulsion
Dragan Kožulović University of the Bundeswehr Munich, Department of Aerospace Engineering, Institute of Jet Propulsion