Abstract:

Variable geometrical characteristics of the four stage radial inflow turbines and heat exchangers are analysed using the computational fluid dynamics (CFD) method. The China’s first MW scale supercritical compressed air energy storage test system is used as an example in the analyses. The results show that an increase in the third stage guide vane opening gives the greatest change in the expansion ratio of the third stage , followed by that of second stage, and the isentropic efficiencies of the two stages vary greatly. When the guide vane opening of first and third stages increases, the expansion ratio tends to be evenly distributed across each stage, and the mass flow rate, the total power, the average isentropic efficiency and the specific work are all seen to increase. When the system is run with a changing load, the joint regulation of the guide vane opening of the first and third stages can increase the range of flow rate and the total power of multistage turbine. In the same time, a wide range of adjustment can be achieved by adjusting the opening of the first stage guide vane, whereas the fine-tuning can be achieved by changing the third stage guide vane opening. When the total pressure of the first stage is lower than the design value, the system can operate efficiently in a wide range of operating conditions with improved isentropic efficiency and total power occurring at 80% first and third guide vane opening.

Key words: adjustable guide vane, variable geometry, variable condition, multistage radial inflow turbine, numerical simulation