Numerical Analysis And Thermal Economic Diagnosis Method Of Steam Turbine Flow Passage

Economy of steam turbine is severely affected by the flow passage losses. It is very important to study the mechanism of flow passage losses and normal value of diagnose in order to evaluate the operating condition of steam turbine flow passage. And this research will be helpful to improve the relative internal efficiency of steam turbine and promote the energy conservation and pollution reduction.First, aimed at no final conclusion of the rotor speed of steam turbine influenced on steam flow characteristics of seal at present, mechanism and flow characteristics of clearance leakage of diaphragm gland are deeply researched. The focus is the effect of the rotor speed on flow field of seal. The results show that the effects of rotation on the internal flow and leakage are much smaller than structural parameters of seal.Second, the change rule of the leakage flow, the trajectory of leakage vortex, the mixing degree of tip leakage and main flow at outlet of suction surface and the vortex strength along axial direction with the blade tip clearance are studied by numerical simulation method. And, a comparative study is made by using large eddy simulation method. The results show that the unsteady of main stream is caused by the tip leakage flow. The effects of tip leakage flow on main stream appear some regularity, from weak to strong, and then from strong to weak. The secondary vortex of flow passage changes near the suction surface to away from the suction surface, then the other. The incidence of leakage vortex is recurring process that from weak to strong, and then from strong to weak. The leakage vortex is strengthened with the increase of the tip clearance, and the range affected by leakage vortex increases. The large eddy simulation method can better capture the formation, shedding of the leakage vortex and the interaction with the wake vortex. So the large eddy simulation method is good to study the unsteady interference between the leakage vortex and all kinds of vortexes.At the same time, the flow field of the exhaust hood and condenser throat which has inner heaters and exhaust of turbine driven feed pump is studied by coupling numerical simulation method based on the thermodynamic behavior of wet steam and the different inflow condition, in order to study the real flow condition of wet steam in the exhaust channel. The results show that the energy loss coefficient of exhaust channel decreases with increasing the inlet wetness, the intensity of swirl flow and the inflow angle.Finally, the index for thermal economic diagnosis of steam turbine flow passage and its normal value are studied. The results show that the relative internal efficiency is coupled to ideal cycle thermal efficiency, when the regeneration system or reheated temperature system is used in steam turbine. The relative internal efficiency of steam turbine cannot accurately reflect the economic performance of the flow passage in operation. It is recommended that the flow passage condition of steam turbine be estimated by relative internal efficiency of stage groups. And, a method to determine the norm of relative internal efficiency of stage groups is proposed. It is difficult to determine the norm relative internal efficiency of the last stage group lying in wet steam region. A method based on BP neural network to determine the normal value is proposed. The studying results fall foundations for thermal economic diagnosis of steam turbine flow passage.