The Reaearch Of The Influence To Turbine Performance By Flange Clearance Of Propeller Turbine

The axial flow water turbine is very sensitive to the flux change, and the flux change affect the efficiency and power of the water tubine directly. The axial flow water turbine which run above the river with lots of bedload, its flange clearance is enlarge because of cavitation and abrasion. Then, it enhances clearance leak fluxion to make a decrease of the water tubine actual availably flux, and reduces efficiency and power of the water tubine, even worse, it doesn' t make water turbine bring load and work normally. Researched flange clearance leakage flows of the axial flow water turbine, it have some science signification and much more practice engineering signification.The text select the product of axial flow water turbine ZD760-LH-80 ,and get seven kinds of water turbine models with different tip clearance gap width by changing the diameter of the turbine casing. The value of tip clearance is as follow:0mm,1mm,3mm,6mm,8mm,10mm,15mm. The standard k-εturbulence model and SIMPLE algorithm are applied to analyze the flow passage of the water turbine at three condition (large flow condition,rating condition,low flow condition)under different schemes by FLUENT6.1 in this thesis. The result indicates that:The tip clearance flow has great influence on the surface of suction and blade tip;A small low preesure area lie in import flange of working surface and suctional surface,it is the original area of the leaky vortex in clearance;The low preesure area of clearance inside expand along with the extendability of the tip clearance value;Axial velocity distribution shows that the tip clearance leakage flow is asymmetric and the worst leakage flow area is at 20%-30% region be part from the aerofoil cephalic region of the outer margin blade tip;Combining with Empirical formula and using the function of surface integral in the FLUENT, we calculate the leak flux of the flange clearance.Through calculate the flux of tip clearance, we can conclude that the efficiency and power of water turbine decline rapidly along with the extendability of the tip clearance value in three working condition. When the value enlarge to 15mm from 0.7mm of design, the efficiency and power of water turbine decline 17%, 18% and 22% in turn of the low flow condition, the rating condition and large flow condition. When the value of the tip clearance is 8mm in the three running condition, the water turne has work at available area verge of the composite performance curve. If the value keep on enlarging, the water turbine is going to work out of available area verge of the composite performance curve and the efficiency and power of the turbine decline much more quickly. In addition, the numerical simulation result coincide with the production and examine and repair date of the hydroelectric power station. So it shows the calculate result is credibility and rightly.