The First Application of a Miniature Laser Doppler Velocimetry System for Time-Resolved Velocity and Turbulence Measurements in a Two-Spool Rig

Abstract This paper presents the first application of a two-dimensional miniature Laser Doppler Velocimetry system (mini-LDV) in a nonstationary, engine-representative flow environment. The miniaturized system enhances maneuverability, allowing it to be deployed in confined or difficult-to-reach areas where traditional turbomachinery-related LDV systems might not be suitable. Experiments were conducted at the Transonic Turbine Test Facility of the Institute of Thermal Turbomachinery and Machine Dynamics at Graz University of Technology. The test setup consists of the high-pressure turbine stage, an intermediate turbine duct — in this case, a Turbine Vane Frame configuration (TVF), and the downstream located first low-pressure rotor. This allows for the replication of engine-relevant flow features. Additionally, the rotor-stator cavities of the setup were supplied with purge air. After validating the mini-LDV system on a separate test bench, the measurements for this work were performed in the TVF flow duct between the vane grid. The results from the mini-LDV system were validated by comparing them with measurement data from a five-hole probe and constant temperature hot-wire anemometry, which showed good agreement. Despite the mini-LDV’s reduced laser power compared to traditional LDV systems used in turbomachinery, it effectively captured reliable flow data in the complex, unsteady environment of the two-spool rig.