The Complement Of Complete Characteristic Curve Of Pump's Numerical Value Transformation And The Comparison Of Different Application Methods In The Water Hammer Computation

In recent years, because the near city water and river water's pollution makes the surface water's quality deterioration, and excessive use of groundwater will lead to land subsidence, thus the long distance Water Transfer Projects are increasing year by year. With the increase in such projects, urban water supply pipeline's blast frequency is general increased, and most of burst pipes are caused by the damage of water hammer which caused by suddenly stop the pumps. Therefore, the calculations of Water hammer and prevention of pipe explosion are essential. The calculations of Water hammer are based on the water pump comelete characteristic curve, because this type of curves are very complex, when calculate Water hammer, we must use the numerical method to modify the curves for the computer called. But the Measurement of water pump comelete characteristic curve is very time-consuming, the measured curves very few at present. When comelete characteristic curve which we need is lacking, how to obtain relevant datas for the computer called. In this regard, we conduct the following researches.(1) When the water pump comelete characteristic curve with the measured data, we give the specific methods of quantize the curve for the computer called.(2) When the water pump comelete characteristic curve without the measured data, we have two existing methods to obtain the required comelete characteristic curve which we need, namely, approximate calculation method and general model method; then we point out the shortcomings of this two were methods; and based on the general model methods,we proposed two new methods to get the comelete characteristic curves which we need, that is, general model method based on quintic polynomial and general model method based on classification of cubic polynomial.(3) Based on The pump characteristic curve and pump specific speed, we raised a new test model which use to test the accuracy of different general model method. And use the test method and the pump performance curve with different specific speeds, to do a specific comparison with the methods which mentioned in point (2).(4) Finally, Combined with the Integrated Water Supply Project Water's hammer calculation example in Xianyang, Xinjiang and Liaoning, we compared the water hammer's pressure cased by the pump's suddenly stop, which use different general model methods to transformation curves.Came to the conclusion, the general model method baced on classification of cubic poiynomial is most accurate. And when the data which got by different methods are used in water hammer calculation, the effects is relatively large in some cases. Therefore, in the future, when we calculate the water hammer, use general model method baced on classification of cubic polynomial to reduce the error in water hammer calculations is very necessary.