Experimental And Numerical Investigation Of Flow Field In Steam Turbine Low-Pressure Exhaust Hood With Air Cooling

The performances of the steam turbine are decided by its economy and safety. The economy of the steam turbine is evaluated by the summation of all kinds of loss and the exhaust loss is about 15 percent of the whole loss of steam turbine. So it is very significant for the engineering application to analyze the loss mechanism and optimize the configuration of the exhaust system by the CFD investigation of aerodynamic performance of the exhaust system.The flow field of the exhaust hood is three-dimensional and unsteady. The early investigations focus on the blowing experiment of model to investigate the performances of exhaust hood and less experimental measurements for the flow field are carried out. To deep investigate the flow in the exhaust hood, experimental measurement and numerical simulation are carried out in the project to investigate the flow field of the exhaust model.First, the PIV system is applied to get the two-dimensional flow fields on different diagnostic planes of the exhaust hood. The vortex structures and their fluctuant characteristics with time on different diagnostic planes are caught. Second, ICEM of Anasys software is applied to generate the computational grid of the exhaust model and the numerical simulation is carried out using CFX software. Through the CFD simulation, the effects of the reinforcing rib and the baffle of pressure dilator on the flow field and the aerodynamic performance are investigated. The numerical simulations are also compared with the experimental measurements to validate the reasonability of CFD for the exhaust system. The vortex structures in the exhaust hood are caught by the experimental measurement and the numerical simulation successfully. The flow separation near the oriented loop outlet of the pressure dilator makes the effective outlet area of the pressure dilator reduced and so the effect of pressure dilator debases. Synchronously, two similar passage vortices where the flow velocity and pressure is low exist in the volute of the exhaust hood and these bring the flow loss, make the outlet velocity distribution of the exhaust hood asymmetric and influence the efficiency of the condenser. The data and conclusions from the experimental measurements and numerical simulations are valuable for deep understanding the loss mechanism and optimizing the exhaust system.