Optical techniques for turbomachinery flow analysis

The conduction of measurements within the blade row is important for obtaining a detailed understanding of the flow processes in turbomachines. Suitable measuring techniques are provided by optical measuring methods, such as flow visualization, schlieren, and holographic interferometric procedures. While most of these methods give only qualitative information, it is in certain cases also feasible to conduct quantitative measurements. A description is given of laser velocimetry (LV), which represents currently the most promising and most developed measuring technique. Laser anemometers have the capability to measure the speed of small micron sized particles in flows. Attention is given to the laser Doppler velocimeter, the laser dual focus method, measuring errors and seeding and turbomachinery application related problems. A review of turbomachinery measurements is also presented.