Fig. 2 General characteristics of multi-stage reheat centripetal turbine with variable working condition Progress in research on multistage reheat centripetal turbine of compressed air energy storage

In the compressed air energy storage System, the performance of multistage reheat centripetal turbine has a significant effect on the system efficiency. In the actual operation of energy storage system, multistage reheat centripetal turbine is often operated under non-design conditions, so it is necessary to study and analyze the characteristics of its variable working condition.

Recently, the Institute of Engineering Thermal Physics, Chinese Academy of Sciences, energy storage research and development center through numerical and experimental methods to carry out relevant research, and make new progress. The researchers first put forward the whole numerical calculation method, using the porous medium model to simulate the plate-fin heat exchanger, given the inlet and outlet boundary conditions, the parameters matching and overall performance can be obtained by one calculation, and the numerical model is shown in Figure 1. The researchers analyzed the characteristics of multi-stage reheat centripetal turbine under four kinds of conditions, such as total pressure, rotational speed, reheat temperature, first stage guide Yecaido and so on, and studied the variation regularity and characteristics of different levels of expansion ratio, efficiency, work, mass flow and so on under varying working conditions. The results show that the average efficiency is basically the same when the total inlet pressure drops, but the efficiency of the fourth stage decreases greatly. When the rotational speed decreases, the average efficiency decreases; When the reheat temperature increases, the power of the system increases greatly, but the average efficiency decreases obviously.

When the opening degree decreases, the fourth stage expansion ratio decreases, the first stage increases, the two, the three levels change less, the average efficiency decreases. At the same time, the researchers found that the losses in the guide Vane channel mainly focus on the side of the suction surface of the vane outlet and the trailing edge of the guide vane exit, the total pressure loss due to the leaf top clearance is relatively small, the total pressure loss mainly occurs in the rear 20% of the guide vane channel. The entropy increase in the moving vane channel is homogeneous, which belongs to the uniform loading type vane. When the vane opening is reduced, the leakage flow through the leaf top gap is more easily mixed with the main part of the Leaf high school in the posterior 20% region of the guide Vane channel, resulting in two loss of flow.

When the total inlet pressure is lowered, the pressure on the surface of the moving blade is lower than that of the suction surface, which results in the loss of power and the average efficiency of the part blades.

Relevant research results have been published in the International journal Proceedings of the Institution of Mechanical Engineers, part a:journal of Power and energy.

Fig. 1 schematic diagram of multistage reheat centripetal turbine