Study On Measurement Of Large Pipe Flow In Hydropower Station

The efficiency test of the prototype unit of the hydropower station is conducive to the identification of the comprehensive characteristics of the turbine,the volute flow coefficient K of the fixed unit,and the guidance of the power plant to optimize the economic operation.Therefore,it has extremely important engineering significance.What's more,the measurement of turbine flow is the most important and key link in the efficiency test of hydropower station prototypes.The accuracy of flow measurement determines the success or failure of the entire efficiency test directly.This paper takes the unit of No.1 Plant A of Yulin Hydropower Plant of Jiangxi Power Company of the State Grid which has been transformed as an example,analyzing and evaluating the level of this efficiency test mainly from three aspects: the efficiency test of the real machine,the comparison of test methods,and the CFD calculation error.First of all,the test of the flow measurement of the convective speed meter is studied in detail,and the possible errors in the test results are introduced and analyzed from the selection of the instrument,the arrangement of the test and the setting of the important parameters.Through the CFD simulation,the influence of the bending section on the test accuracy is analyzed,and the velocity distribution of the flow section will be affected by the bending section,but the final flow results are not affected.The results show that the f0 low velocity measurement results can be used as the standard flow rate of efficiency test for the unit of No.1 Plant A of Yulin Hydropower Plant.The layout of the sound channel,the selection of instruments and the result processing are described.The test results of ultrasonic test and flow meter method are carefully compared.The causes of the relative error of the two flow measurement results are analyzed theoretically.The CFD simulation is used to calculate the error caused by the test device of the flow meter,which is compared with the test results.The analysis shows that the relative error of ultrasonic method is 2.2%,that is,the flow value relative velocity meter is less than 2.2%.The error of the ultrasonic method is caused by the interference of the flow meter test device.At last,the flow coefficient of the volute of the unit is determined by the flow rate measured by the flow meter,and the efficiency-output curve under the different head of the unit is drawn by the flow rate measured by the flow meter and the corresponding output.Combined with the model test of unit of No.1 Plant A of Yulin Hydropower Plant,the results of real machine test and model test are compared and analyzed.91.249 can be used as the K value of the volute flow coefficient of this unit.The efficiency test results meet the design characteristics of the unit and evaluate the reliability of the efficiency test results more comprehensively.At the same time,the paper combines real machine tests and uses CFD numerical calculation techniques to verify and calculate the sources of error analysis.On the one hand,the actual model parameters of the real machine test are connected to the principles of various flow measurement methods to effectively evaluate the accuracy of the test from the perspective of numerical simulation;on the other hand,this paper makes a bold attempt and experience accumulation for opening up new techniques and means for the error analysis of water turbine field test.