Aerodynamic performance and flow characteristics analysis of Tesla turbines with different nozzle and outlet geometries

The aerodynamic performance and flow characteristics of a multichannel nozzled Tesla turbine were investigated numerically with different nozzle and outlet geometries at different rotational speeds. Two kinds of nozzle geometries were proposed: one nozzle channel to one disc channel (named as one-to-one turbine) and one nozzle channel to several disc channels (named as one-to-many turbine). Simplified radial outlet and real axial outlet geometries of the Tesla turbines were adopted to research the influence of outlet geometries. The results show that compared with the one-to-many turbine, the isentropic efficiency of the one-to-one turbine is much higher; while the flow coefficient is much lower. In addition, in the middle disc channels (DC1 and DC2) of which two walls are rotating disc walls, the flow fields are almost the same, but different from that in the side channel (DC3) of which one wall is a rotating wall and the other one is a stationary casing wall. DC1 and DC2 generate more torque with less working fluid, thus the disc spacing distance of DC3 should be narrower than that of DC1 and DC2. Compared to the one-to-many turbine, the working fluid flowing through DC1 and DC2 of the one-to-one turbine is much less, and the flow path lines are much longer. The results of different turbine outlet geometries show that compared with the turbines with radial outlet, the isentropic efficiency of the one-to-many turbine with axial outlet is a little higher, while that of the one-to-one turbine with axial outlet is lower. This is due to the larger torque on the disc hole walls, despite a lot more total pressure loss in the exhaust vent of the one-to-many turbine. Therefore, the contribution of disc hole walls to torque cannot be neglected in numerical simulations.