Abstract: In order to strengthen the injection performance of the fertilizer injector, computational fluid dynamics (CFD) was used to study the effect of nozzle length on the performance of the jet fertilizer injector. An incompressible multiphase flow model was established to examine the impact of nozzle length on the injection performance of the jet fertilizer injector and investigate its influencing mechanisms. The results showed that the nozzle length has a significant effect on the injection performance of the jet fertilizer injector. When the nozzle length was too long, the growth of fertilizer absorption was limited, reducing the fertilizer injection performance. Under different inlet and outlet pressures, the fertilizer absorption concentration, inlet flow ratio, and fertilizer absorption efficiency of the fertilizer injector were all at their lowest when the nozzle length was L. When the inlet and outlet pressure differed by 1.0 MPa, the fertilizer absorption of the fertilizer applicator with a shorter nozzle length was more than 10% larger than that of the fertilizer injector with a nozzle length of L. Through analyzing the internal flow field of the fertilizer injector, it was found that the negative pressure distribution inside the fertilizer injector is a key factor affecting the injection performance. Longer nozzle lengths limit the negative pressure distribution area inside the fertilizer absorption chamber and lead to more intense cavitation, thus affecting its corresponding injection performance. This study provides theoretical support for the design and optimization of jet fertilizer injectors.

Key words: cavitation, nozzle length, jet fertilizer injector, injection performance

摘要： 为强化施肥器的吸肥性能，提出采用计算流体力学手段研究喷嘴长度对射流式施肥器吸肥性能的影响。建立不可压缩多相流模型，基于该模型研究喷嘴长度对射流式施肥器的吸肥性能的影响，并对其影响机制进行调查分析。研究结果表明：喷嘴长度对射流式施肥器的吸肥性能有显著影响，当喷嘴长度过长时，施肥器的吸肥量增长受限，吸肥性能降低。不同进出口压差条件下，喷嘴长度为L施肥器的吸肥浓度、进口流量比和吸肥效率这几个指标也均为最低；且当进出口压差为1.0MPa时，喷嘴长度较小的施肥器的吸肥量均比喷嘴长度为L时的吸肥量大10%以上。通过对施肥器内部流场进行分析得到，施肥器内部负压分布是影响吸肥性能的关键，而较大的喷嘴长度则会限制吸肥腔内部的负压分布面积导致更加剧烈的空化现象，进而影响其相应的吸肥性能。

关键词: 空化, 喷嘴长度, 射流式施肥器, 吸肥性能