滴灌滴头内流场的数值模拟及流道优化设计

针对滴灌技术中农用传统迷宫型滴头流道内易堵塞的缺点,提出根据流线形状设计"自清洗"型滴头的思想.以滴头流道内流场的三维数值模拟分析为基础,以减少非主流区域通流面积和避免较大的主流速度梯度为基本思想,对滴头流道的结构形状进行优化设计,消除流道中的滞止区和涡旋区,使得流道内速度分布趋于均匀以减少低速流动区域.优化前、后的计算结果表明:优化后的滴头能够有效地避免内部涡旋和滞止区的产生,提高了滴头流道的抗堵性能;滴头在紊流流动状态运行时,流道的近壁面速度较高,抗堵性能更好;优化后的滴头流道整体压降降低,可以通过延长流道长度和增加进口流量予以弥补.

Numerical Flow Simulation and Optimum Channel Design of Drip Irrigation Emitter

Traditional drip irrigation emitter with small diameter labyrinth channel is vulnerable to clogging by the debris in water, and the phenomena may partly be attributed to the stagnant regions and vortices existing in the flow field within the channels. A new design scheme of self-washing emitter is presented. Numerical simulation is first conducted, and then channel curves and shapes are corrected and optimized based on the calculated streamlines. The new design can effectively eliminate the vortices and low velocity and stagnant regions within the emitter pore. It is found that, compared with laminar flow, turbulent flow assumes an uniform velocity profile in the cross section of the channel and higher velocities even in the region close to channel wall, and therefore turbulent flow would have better anti-clogging characteristics. The pressure drop across the optimized channel is significantly reduced, and the reduction can be compensated by increasing the channel length and the flow rate through the channel.