Numerical Simulation Of Reversible Axial Turbine

Accurate Simulation of flow field in hydraulic machinery helps us to predict general performance of different components (especially that of runner) with low cost. So it is becoming an essential tool for designing new high quality runner in factories. People have been looking for good methods which can work well in a wide operation range to precisely predict comprehensive performance of hydro unit, including efficiency, cavitation property and stability, so as to reduce cost in test and model-making.In this thesis, some theoretical problems relating to numerical simulation of hydraulic machinery were put forwards firstly. Combing with standard k-e model, N-S equations were employed in three dimensional steady flow calculation under many work conditions with different blade angle and different guide vane openings. In the simulation, plenty of methods have been used, including structural grid division, velocity input of the turbine inlet boundary condition, free outflow in outlet, static and dynamic interfering sliding grid model technique in fixed coordinates and rotational coordinates, wall function applied in along-wall and SIMPEC algorithm which had good convergence for pressure and velocity.From the calculation,turbine efficiencies have been obtained that it was 75.8% of most high-efficiency in the positive operation condition,and 66.6% in the negative operation condition.The results from the calculation agree well with the results from the experiment,but the value of calculation was lower than the value of experiment,that the average error was 7.5% in the positive operation condition and 2.5% in the negative operation conditon.The error analysis was performed at the same time.Based on work mentioned above, further analysis on inner flow characteristics of turbine have been studied in the positive and negative condition. According to small blade angle blade velocity of flow and pressure maldistribution, and to take off to flow and bump in the too big blade angle condition the losses increased in various degree.Using the numerical simulation results, component loss in different work conditions has been calculated.The losses wave relatively high in therunner and draft tube.The section of losses of runner was about 15% in the positive condition,but about 21% in the negative condition.The losses of draft tube was about 12% in the positive and negative condition.The kinetic losses of draft tube attained 19% because the kinetic energy of the runner outlet increased and the kinetic resumed coefficient of draft tube was small at the large discharge condition deviating from the negative optimum operation condition.