Application of a multi-tiered blade system for reversible hydromachines of PSPP

Abstract

The use of reversible hydraulic machines is often the most cost-effective option in most pumped storage configurations. At the same time, among reversible machines, radial-axial pump-turbines are most often used. This is due to the fact that such hydraulic turbines are capable of operating at high pressures, which are used in pumped storage power plants. The impellers of such reversible machines have a rigid-blade system, that is, they are not able to change their position, like the blades of axial and diagonal rotary-blade hydraulic turbines. What makes the problem in the design of pump-turbines is that, due to the different influence of hydraulic resistances, the optimum in pumping and turbine modes is different. This is taken into account in the design and determines both geometric and operational parameters. As a result, the maximum impeller diameter calculated for the pumping mode does not correspond to the optimal turbine geometry. At the same time, it is the turbine mode that should have the maximum efficiency, since the cost of peak electricity is higher than the cost of energy during the hours of dips in the daily load schedule corresponding to the pumping mode. In order to design the impeller-pump of the turbine optimally for the turbine mode, it is necessary for the same impeller to develop a greater pressure in the pumping mode of operation. To increase the pressure in the pumping mode, multi-tiered paddle grids can be used. This paper discusses the effect of additional tiers of hydrodynamic grids on the turbine regime and the prospects for their modernization in conjunction with other well-known technical solutions to increase the pressure and expand the operating area of HPP hydroelectric units.