LDA Measurements in a Kaplan Spiral Casing Model

This paper presents an experimental inv estigation of a Kaplan spiral casing turbine model. A two-component laser Doppler anemometry (LDA) apparatus was used to measure the velocity profiles at different locations in the turbine. To improve the signal quality and measurement accuracy, a refractive index matching optical box was mounted on the circular pipe of the spiral casing inlet. The investigations were carried out with a constant runnerblade angle and at three different loads: the best operating point of the turbine and two off-design operating points (left and right side of the propeller curve) with the presence of a vortex breakdown. The mean velocity profiles and corresponding RMS at the spiral casing before the guide vanes and at inlet of the spiral casing are presented for the different loads investigated.