Design And Study On The Flow Characteristics Of Radial Inflow Turbine For Organic Rankine Cycle

Organic Rankine Cycle(ORC)power generation technology plays an important role in the utilization of industrial waste heat,solar energy and geothermal energy.As an important component of low temperature waste heat power generation technology in the circulatory system,the radial inflow turbine has attracted more and more attention because of its advantages of a small residual velocity loss and flow loss,the simple structure,and wide operating range.In this paper,the design method and flow characteristics for O RC radial turbine were investigated,and the main research contents are as follows:Using cyclohexane as the working fluid,the aerodynamic parameters and the structure sizes of the stator and rotor blades were determined based on thermodynamic design of 200 kW radial turbine.The numerical simulation of turbine was carried out by ANSYS-CFX,then the overall performance and internal flow of the turbine were analyzed.It has showed that the thermodynamic parameters of the radial inflow turbine are in agreement with the numerical simulation results and all parameter errors are controlled within 3%.Thus the correctness of the design method is verified,and the high efficiency of the turbine is obtained.The simulation results can truly reflect the internal flow characteristics of the turbine.The turbine has good performance,the pressure drop distribution and the Mach number distribution are reasonable,and there is no large flow separation phenomenon.The flow characteristics of ORC radial inflow turbine were studied.In view of the stator cascades,the flow loss mechanism and the main loss distribution in stator cascades of ORC radial inflow turbine were analysed.And the forms of various vortexs on lower and upper end walls and in stator cascade passage were investigated,meanwhile giving the distribution of the to tal pressure loss coefficient.The simulation results show that,there is a horizontal flow between the pressure surface and the suction surface in stator cascades.However,passage vortex has not formed which is not an important vortex structure in the secondary flow vortex structures in stator cascades of ORC radial inflow turbine.The main total pressure loss appears in later 40% cascade passage in axial chord direction,near to lower and upper end walls in blade height direction,and near to the suction surface in circumferential direction.Aming at the rator,changing the shape design parameters to get the different twisting laws of blades,the influence of twisting law of blade on the efficiency of the turbine was analyzed.The conclusion is that the maximum variation range of the efficiency of the wheel periphery of the turbine is reached by 2.44% when twisting law changes,which is an important influence factor for the optimization design of the impeller structure.The effects of inlet temperature,outlet pressure and rotating speed on the efficiency performance and flow performance of the turbine were analyzed under different operating conditions.The analysis shows that,under the design condition,the influence of each variable on turbine efficiency and flow rate is minimal,and the efficiency can be kept at a high level.The rotational speed has the greatest influence on the turbine efficiency among three factors,and the maximum change of efficiency is 10.88%.The flow range is larger at 120% speed and 120% back pressure.O n the whole,the ORC radial turbine performance greatly influenced by variable operating conditions,and the reasonable control of the inlet and outlet parameters and the speed level is very important for the efficient operation of the turbine.