Design and Internal Flow Characteristic Investigation of High-Temperature H[sub.2]/Steam-Mixed Working Fluid Turbine

In this paper, an improved RSM-CFD method is used to optimally design a mixed turbine of non-equilibrium condensing steam (NECS) and hydrogen (H[sub.2]), of which the response surface method (RSM) and computational fluid dynamics (CFD) are coupled to take into account the effects of the wet steam non-equilibrium condensation process of the multimixed working fluid. A single-stage H[sub.2]/Steam (NEC)-mixed turbine was developed based on the improved RSM-CFD, and the effect mechanism of the H[sub.2] component ratio (ω[sub.H2]) on the flow characteristics, internal power, and isentropic efficiency within the turbine stage were investigated. The results show that the isentropic efficiency (η) increases with the increase in the hydrogen component ratio (ω[sub.H2]), since hydrogen, as a non-condensable component, can inhibit the nucleation and growth of steam, reducing the pressure pulsation on the blade surface; furthermore, it accelerates the transport and diffusion of liquid droplets, inhibits the flow separation, and reduces the flow loss in the flow channel. However, the internal power of the turbine (P) tends to decrease with increasing ω[sub.H2], since the increase in hydrogen reduces the pressure difference on the blade and lowers the torque of the fluid acting on the blade, and at the same time, the vortex and radial flow intensify, and the enthalpy drop inside the stage decreases. On this basis, the optimum operating conditions are found where the hydrogen component ratio (volume percent) ω[sub.H2] = 53%. Accordingly, the hydrogen component ratio should be maintained in the range of 38–68%, considering the work capacity and hydrogen yield of the mixed working fluid.