Fast traveling pneumatic probes for turbomachinery applications

Abstract

Pneumatic probes are commonly used to determine the flow vector as well as the thermodynamic state of the fluid in turbomachinery applications. The conventional method to measure a flow passage velocity or pressure field is to move the probe to discrete positions and to hold a certain settling time before valid data can be recorded. This study presents a measurement methodology leading to a reduction in the required measurement duration of up to 70-90%, depending on the level of flow field resolution. The approach is based on the concept of continuously traversing probes as introduced by Gomes et al. [1]. However, the system model is changed by reducing the transfer function to a single PT1-behavior. While the experiments conducted by Gomes et al. [1] were limited to only linear cascade measurements, the method used here is extended to turbomachinery applications with highly complex flow structures. The continuous traverse measurements are validated through a comparison with conventional discrete measurements that include characteristic settling time. For this purpose, tests have been performed in an axial diffuser test rig operated with air and a low pressure steam turbine. The results obtained with the new approach show a good match, thus proving the viability of the proposed method for turbomachinery applications. For future tests, a significant reduction in measurement time and cost can be achieved.