This study intends to improve and extend the understanding of the origin and development of pre-stall perturbations in axial, multi-stage, transonic engine compressors. The current state of knowledge is mostly based on investigations on component level and represents thus the reference case of compressor operation under reproducible model conditions. To investigate the transferability of these findings to the engine system level integration of turbo compressors, it is proposed with this study to conduct systematic investigation of the effect of turbo-engine-specific disturbance factors on the aerodynamic phenomena near the stability limit. The ISA can rely on a broad database of experimental test data undertaken with the two-stage low pressure compressor at the Larzac 04 C5 turbofan engine, forming the validation basis for the intended CFD simulations. The study focuses on the initial formation of pre-stall perturbations and their evolution. In a first step, the Larzac LPC is numerically subjected to aerodynamic perturbations of the inflow and geometric deviations from the reference design, using a reduced compressor CFD model with a Zonal Large Eddy Simulation (ZLES) approach. Qualitative and quantitative dependencies between the type of a disturbance pattern, the temporal imprint and the resulting triggering of pre-stall perturbations are to be determined. Following the analysis of the triggering mechanisms, the dynamic development of pre-stall perturbations after the initial excitation by engine-specific disturbance factors will be investigated. ZLES simulations of the entire compressor will be conducted to derive flow-physical dependencies for the amplification, the decay behavior, or the potential transformation of initially triggered pre-stall perturbations into experimentally undetectable perturbation patterns. In addition to the local examination of the physical mechanism of action, findings will also be obtained regarding a potential shift in the global stability limit of the compressor as a result of engine-specific disturbance conditions. Two different spool speeds are investigated to represent the range of operating conditions relevant for flight conditions. The distinguished benefit of the proposed research project is the transition of well-established knowledge on stall inception from ideal model conditions to real prevailing engine conditions. The study will provide a novel basis of relevant impact factors on pre-stall perturbation behavior to be considered in the design phase and in the operational service of transonic multi-stage turbo compressors installed in aircraft engines. It is expected that the results will provide specific indications for the further development of early stall detection systems and for the targeted use of active and passive flow stabilization measures to improve component efficiency and to contribute to global fuel savings in air transport.    «

This study intends to improve and extend the understanding of the origin and development of pre-stall perturbations in axial, multi-stage, transonic engine compressors. The current state of knowledge is mostly based on investigations on component level and represents thus the reference case of compressor operation under reproducible model conditions. To investigate the transferability of these findings to the engine system level integration of turbo compressors, it is proposed with this study to...    »