Study on the Influence of Working Condition Uncertainty on Aerodynamic Characteristics of Last Two Stage Blades of Steam Turbine
The operating conditions of steam turbine have a certain degree of random fluctuation,which has potential impact on the stable operation of steam turbine.The working environment conditions of steam turbine were taken as the determined conditions in conventional investigations,and the influence of such random variations was not considered.In this paper,the back pressure,radial flow angle and inlet flow of steam turbine were taken as random variables subject to certain probability distribution,and the influence of the random fluctuations of the above parameters on the aerodynamic performance of the last two stage blades of a steam turbine was studied by CFD simulation combined with the polynomial chaos method.The simulation results show that the method for calculating the inlet boundary condition has little effect on the computational result of the overall performance of the last two stages of steam turbine.When the inlet flow boundary conditions are given,the last two stages have the highest efficiency;when ap-proaching the blocking condition,the random change of inlet and outlet conditions has little effect on the flow rate,but the efficiency fluctuates obviously.The influence of inlet airflow angle on the overall per-formance is relatively small;when the back pressure and inlet flow fluctuate randomly,the shock wave position in the last stage rotor blade fluctuates in a small range.The shock position is insensitive to the fluctuation of the radial flow angle.
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