| The High Temperature Gas-cooled Reactor (HTGR) and external-combustion heat engine firing with non-traditional fuel bring Brayton-cycle helium turbine a very good prospect. If the helium compressor is designed according to conventional air-compressor rule, the pressure ratio of single stage will be smaller and the number of stages will be excessive. These problems present a topic which must be solved in further development. Therefore a new velocity triangle of helium compressor is presented and analyzed. It can increase severalfold stage loading. The test data and experiences of air cascade are used to estimate the profile losses and stage efficiency of the new helium cascade. On the basis of validation for selected turbulence model and mesh division, fluid analysis software FLUENT6.3 is used to simulate the flow of new helium cascade.Simulation results show that, comparing with the conventional design, the new stage loading can be increased by 2 to 4 times when inlet Mach number is 0.466 to 0.7013. Therefore the stage number of helium compressor is reduced severalfold, while profile efficiency can reach 0.939 to 0.894; The air turning angle reaches 38.75°to 49.43°, while the outlet angle reaches 0.78°to -12.45°; There is basically no separating phenomenon in flow field; Reducing the maximum thickness of aerofoil can improve the stage profile efficiency.Because the experimental data are lacking to support the new cascade structural parameters and air cascade test is a kind of low-speed test, there is some deviation to estimate helium cascade performance at the higher Mach number by use of air cascade experiences. In this cascade simulation, traditional original profile thickness distribution (C4 blade profile) is applied, therefore the optimizing for the profile thickness distribution and the shape of flow field are expected to be a greater potential for enhancing performance.
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