Calculation and modification by experiment of driving force for vertical impact sprinkler

Abstract: At present, the most representative and most widely used sprinkler is high pressure vertical impact sprinkler. The magnitude of driving force, an important evaluation indicator, influences not only the stress distribution and service life of the sprinkler but also the stability of the running sprinkler. In order to improve the accuracy of calculated driving force of vertical impact sprinkler, in this paper, we modified the theoretical calculation equations of driving force through the experimental test results, and presented the correction coefficient transformation equations on the basis of the theoretical equations for calculating horizontal driving force and vertical driving force, and verified the amended equations of calculating the driving forces. Moreover, the advanced testing system was used to measure the driving force of vertical impact sprinkler. Our research results showed that the assumed conditions had a relatively significant impact on the calculation of the driving force in the process of theoretical derivation, which caused a large deviation in theoretical values. The maximum deviation was about 20% between the driving force of horizontal direction and that of vertical direction especially under low working pressure. The deviation of the theoretical calculation decreased with the increase of working pressure both in the horizontal and vertical directions. Meanwhile, this also showed that the correction coefficient of theoretical equation was not a constant, and it changed with the working pressure of the sprinkler. The horizontal calculation deviation decreased considerably with the increase of working pressure and the calculation values of horizontal driving force had better accuracy under high pressure, while the vertical calculation deviation was less than the horizontal calculation deviation as the working pressure increased. The overall calculation deviation was relatively large. Subsequently, on the basis of the theoretical equations for calculating horizontal and vertical driving forces, the correction coefficient transformation equations were obtained through the regression analysis of experimental data and were relatively higher in accuracy. The determination coefficient R2 was 0.9799 and 0.9289 for horizontal and vertical, respectively. In addition, the correction coefficients were in an exponential and logarithmic relationship respectively with the working pressure in its calculation equations of the horizontal driving force and the vertical driving force. In the theoretical calculation, the deviation of the driving force presented a reverse relationship with the working pressure as the diameters of sprinkles varied. Within the variation range of measuring parameters, the maximum deviations were 23.99% and 31.08% in the theoretical calculation of vertical driving force and horizontal driving force, respectively. It showed that the theoretical calculation equation of the vertical driving force was higher than that of the horizontal driving force in accuracy before the amendment of the theoretical calculation equations. After the amendment, the obtained values of the vertical driving force and the horizontal driving force were approximate to the experimental values with the deviation less than 5%, showing that the amended equations for calculating driving forces were higher in accuracy. This study provided reference for designing and optimizing the rocker arm and the drive vane of the vertical impact sprinkler.