Equivalent pipe algorithm for metal spiral casing and its application in hydraulic transient computation based on equiangular spiral model

For the metal spiral casing of water turbines, a new equivalent pipe algorithm is developed based on the idea of equiangular spiral. Prototype tests and computations are carried out to investigate the hydraulic transient characteristics. The computation results by using the new model are in a good agreement with the prototype test data with respect to the maximum speed of the turbine-generator unit, the maximum water hammer pressure in the spiral casing and the maximum vacuum in the draft tube. The proposed method is a significant improvement over the conventional algorithm with the accuracy increased and the error reduced by about 3%.