为了研究比例施肥泵驱动活塞在往复运动过程中的受力情况,基于Fluent软件,通过用户自定义函数编程技术实现了相应的三维动网格模型,建立了比例施肥泵三维动态数值模拟模型,并通过实验数据对比验证了模型的可靠性.在此基础上,对施肥泵的内部流场进行了数值模拟.结果表明:所建立的数值模拟模型具有较好的准确性,模拟所得压差流量关系与试验结果基本一致,比例施肥泵流量的模拟值与试验值的最大相对误差为4.20％;模拟与试验所得活塞往复频率随压差的变化趋势基本相同,且模拟值与试验值的相对误差控制在12％之内.驱动活塞在往复运动过程中,泵内大部分流域流速较低,动能基本转变为压能驱动活塞.活塞上行运动与下行运动类似,在行程初期呈加速运动随后进行匀速运动.活塞不同表面所受到的力随压差的增大呈线性递增关系.该研究可为比例施肥泵的性能研究和结构设计提供参考.%Taking proportional pump as the main research object, the force of the drive piston in the process of reciprocating motion was analyzed. On the basis of the Fluent simulation software, a three-dimensional dynamic simulation model of proportional pump was established through writing dynamic mesh programs according to UDF (user defined function) and choosing the reasonable turbulent model. The computational simulation model was also validated by using the experimental data. On this basis, the internal flow field of the proportional pump was simulated. The results showed that the numerical simulation model had good accuracy. The relationships between the flow rates and the differential pressures obtained by simulation were basically consistent with that by testing, and the error between simulated value and experimental value was within 4.20％. The simulated values of piston movement frequency were larger than the experimental values in the full differential pressure range. However, the variation trend of the simulated movement frequency with the differential pressure was the same as the experimental trend. The relative error between the simulated value and the experimental value was 9.5％ under the differential pressure of 0.03 MPa. When the differential pressure increased to 0.15 MPa, the relative error between the simulated value and the experimental value increased to 11.2％. The relative errors between the simulated values and the experimental values for the piston movement frequency were controlled within 12％. The simulated velocities of the piston were slightly higher than the experimental values. However, the variation trends were consistent, and the movement velocity reached the steady state after a short time for both simulating and testing. The movement law for upward movement was similar to downward movement, and the drive piston was accelerated and then kept uniform motion. The force in different surfaces for the drive piston increased linearly with the increase of differential pressure. The flow velocities in the inlet valve and outlet valve were very large, which was conducive to mix the fertilizer and water. The upward movement time of the drive piston during a period was 0.33 s and the downward movement time was 0.275 s under the differential pressure of 0.09 MPa, which indicated that the upward movement time was longer than the downward movement time. The flow velocity in most of the flow field was low and the kinetic energy was basically converted to pressure to drive the piston in the reciprocating motion process of the drive piston. Under the differential pressure of 0.09 MPa, the maximum flow velocity increased from 7.5 m/s at 0.02 s in the downward stage to 9 m/s at the end of downward movement. Similarly, the maximum flow velocity increased from 6.5 m/s at 0.02 s in the upward stage to 8.5 m/s at the end of the upward movement. In downward movement stage, the force on the first surface and the third surface fluctuated greatly at the initial stage and then reached a relatively steady state after a certain amount of time under the differential pressure of 0.09 MPa. The force on the second surface decreased from 699.3 to 335.9 N in 0.055 s and then remained stable. In upward movement stage, the force on the first and third surfaces was basically stable at a certain level, and the force on the second surface increased from 0 to 359.7 N in 0.034 s and then kept stable under the differential pressure of 0.09 MPa. The force on the first surface and the third surface was driving force, and the force on the second surface was resistance. The results can provide valuable information for the design method of the proportional pump as well as the reasonable adjustment of the differential pressure during the operational process.
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