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 equiangu-lar spiral. Prototype tests and computations are carried out to investigate the hydraulic transient characteristics. The computation re-sults by using the new model are in a good agreement with the prototype test data with respect to the maximum speed of the tur-bine-generator unit, the maximum water hammer pressure in the spiral casing and the maximum vacuum in the draft tube. The propo-sed method is a significant improvement over the conventional algorithm with the accuracy increased and the error reduced by about 3%.

Structural Research on Embedment of a Bare Deflated Spiral Case

Complete bearing spiral case has not been applied to large power stations in China so far. The proposal of applying complete bearing spiral case necessitates an analysis of the reliability of the spiral case structure and the security of units under various working conditions. In combination with practice of a project, this paper presents a three-dimensional nonlinear finite element static analysis of the concrete using a concrete smeared crack model by means of the well-known finite element method （FEM） software ABAQUS. The stress distribution of the spiral case and reinforcing bars, the range of damages in surrounding concrete, and the displacement of structure are quantified. The computational results indicate that the embedment method ensures the structure＇s safety in strength. At the same time, the result shows that this embedment is a kind of preponderant method for embedment in aspects of economy and technique of construction, and the application of this embedment method to the hydropower station is feasible provided that some proper engineering measures are taken to constrain the width of the concrete in accord with the code＇s requirements. The paper proves the security and reliability of the structural design of spiral case in hydropower station accordingly.

Improving the Energy Performance of a High-Pressure Hydraulic Turbine by Researching the Flow in the Flow Part

In this study, the goal is to increase the efficiency of a high-pressure hydraulic turbine. The goal is achieved by numerical flow simulation using CFX-TASCflow. This approach reduces costs and time compared to the experimental approach and allows for improving the turbine productivity and its design. The analysis of energy losses in the flow part of the turbine Fr500, as well as the analysis of the influence of the opening of the guide vanes on changes in energy losses. The results showed that the greatest losses occur in the guide vane 3.02% based on the two-dimensional model and 2.5% based on the 3D model, which significantly affects the efficiency. The analysis was carried out using programs for calculating fluid flow in two-dimensional and three-dimensional formulations. With the help of the study, the main energy problem is solved—increasing efficiency.