A 3D-LDA Study of the Relation Between Coincident and Time Stepped Non-Coincident Stress Measurements in a Linear Compressor Cascade

Abstract

Especially in the turbulence research, it is necessary to record three velocity components concurrently. As a result, all six components of the Reynolds stress tensor and higher-order velocity correlations can be determined. This article assesses the three-dimensional flow field of a linear transonic compressor cascade. The velocity field within the blade passage is measured using a 3D-LDA system. This requires a coincident measurement of the velocity. However, this leads to a significant reduction in the data rate. To circumvent this problem there is the general approach of a record interval window to the subsequent generation of coincident data. In comparison to previous publications, a transonic flow is considered here. For a coincident measurement it is essential that all velocities are perpendicular to each other. Because of limited arrangement possibility of the probes the system measures three non orthogonal velocity components. Therefore, a coordinate transformation is necessary. Due to uncertainties in the exact laser alignments, the transformation matrix for this arrangement is determined experimentally. This paper deals with these two problems, for a case similar to gas turbine conditions. The influence of the time interval on the measured data is compared with coincident data. Within the cascade different measuring planes are considered and a time step study is carried out.

Evaporation Modeling of Water Droplets in a Transonic Compressor Cascade under Fogging Conditions

“…This was monitored using six pressure taps and the phase-Doppler system. The optical measurement setup used was identical to that presented in [9], and thus, the reader is referred to this publication for more detailed information. Demineralised water is sprayed into the settling chamber via a manifold of ten impingement nozzles (PJ10, BETE Germany GmbH) generating a spray with a Sauter mean diameter of D 32 = 32.0 µm and a mean diameter of D 10 = 4.0 µm at the cascade's entrance.…”