Overview of Unsteady Phenomena Emerging in a Stalled 1.5-Stage Transonic Compressor

Abstract

A new transonic compressor test rig for gas turbine front stages was commissioned at the Technical University of Darmstadt in 2018. In the first measurement campaign numerous transient stall maneuvers were conducted by throttling the compressor beyond its stability limit. Several distinct phenomena can be observed during in-stall operation. This work gives an overview of those different manifestations of stall with focus on classification and characterization. For this purpose, detailed post-processing and unsteady data analysis are conducted providing information in terms of operating points, propagation speeds of disturbances, structural behavior of the rotor as well as unsteady wall pressure fields. The authors propose explanations for the different phenomena and possible influences of the rig on the in-stall behavior are discussed. Finally, an overview of the occurrence of the detected phenomena is given.

Transonic compressor Darmstadt Open Test Case – unsteady aerodynamics and stall inception

“…After the emergency bleed is activated, the stabilized operating conditions result in a clean and homogeneous pressure field. Figure 8 shows the pressure rise coefficient [definition see Cumpsty (2004), Mütschard et al (2021)] during stall inception, both for design speed and part speed. For better comparison both are referred to the pressure rise coefficient at stall occurrence.…”

“…Development trends towards reduced numbers of stages with minimum blade counts, able to provide enhanced overall pressure ratios, result in high aerodynamic loading and consequently pronounced secondary flow phenomena. The aerodynamic mechanisms during stall inception are diverse, as exemplarily presented by Mütschard et al (2021Mütschard et al ( , 2022. Even though, stall and surge have been research focus for many decades, as for example summarized by Day (2016), reliable predictions of the driving phenomena, especially during the design phase, still lack in accuracy.…”

Transonic Compressor Darmstadt Open Test Case – Unsteady Aerodynamics and Stall Inception

“…Development trends towards reduced numbers of stages with minimum blade counts, able to provide enhanced overall pressure ratios, result in high aerodynamic loading and consequently pronounced secondary flow phenomena. The aerodynamic mechanisms during stall inception are diverse, as exemplarily presented by Mütschard et al (2020Mütschard et al ( , 2021. Even though, stall and surge have been research focus for many decades, as for example summarized by Day (2016), reliable predictions of the driving phenomena, especially during the design phase, still lack in accuracy.…”