【作者】 徐幼林；

【导师】 张沂泉；

【作者基本信息】 南京林业大学 ， 机械设计及理论， 2009， 博士

【摘要】 本文分析了在线混合混药器工作机理,确定了混药器基本结构及相关尺寸,设计了4种不同结构的混药器:C型为吸药口在喉管后、B型为吸药口在喉管中、G型为吸药口在喉管后斜向吸入、D型为吸药口在喉管前。利用CFD对混药器的内部流场进行了数值模拟,表明C型混药器吸药性能最好;B型混药器吸药性能一般;G型混药器吸药性能较差;D型混药器吸药性能最差。同时进行了吸药性能试验,结果验证了仿真的可靠性。进行了混药器内部流场流动图像数据采集和分析。用水加示踪剂进行了在线混合试验,结果表明,除G型混药器外,随计量泵指示流量增加,混合效果明显改善;随离心泵指示流量增加,混合效果逐渐变差。针对不同农药属性采用C型混药器的在线混合内部流场,对Prime oil和Silicon oil加示踪剂进行了在线混合试验,表明用C型混药器均能实现在线混合,但是对Silicon oil的混合效果和混合均匀性要优于Prime oil。分析了在不同农药属性、不同混药器结构、不同喷雾机工作参数下,混药器的吸药性能、混合效果、混药均匀性的综合影响因素,表明足够的工作液速度能够实现稳定吸药;良好的混合效果与吸药口位置有关,同时工作液与农药的流动方向应相互垂直,并要求有合理的喉管工作液流速与农药流速比。更多还原

【Abstract】 The mechanism of in-line-mixing inside the chemical mixers was first studied which is a critical component in the direct in-line injection systems to ensure that systems can apply pesticides uniformly to target areas. In light of that, the internal configurations and geometric dimensions were determined in the design of an in-line-mixing chemical mixer. Mixers with four different Venturi mixing chambers were then developed for tests: a C-type mixer with the injection point downstream of the constricted section, a B-type mixer with the injection point at the midpoint of the constricted section, a G-type mixer with an angled injection point downstream of the constricted section, and a D-type mixer with the injection point upstream of the constricted section.A computational fluid dynamics program (FLUENT) was used to assist the simulation of the internal flow field inside the in-line-mixing mixers. The computer simulations showed that among the four mixers the C-type mixer had the best performance in delivery of fluid to the mixing chamber, followed by the B-type and then G-type mixer while the D-type mixer had the worst performance. Test results agreed with predicted performances of the computer simulations.Machine vision technologies were used to analyze the chemical mixing process inside the mixing chamber and a special program was developed to acquire and process digital images of two-phase flow fields recorded by a camera. A water-based water-soluble liquid were used as simulated pesticides for the test. Experiments were conducted that fluorescent tracers were mixed with simulated pesticides enabling the camera to track the mixing process in the transparent chamber. The experimental result showed that except for the G-type mixer, all other three mixers had significantly constant injection flow rates and produced uniform mixtures for water-based simulated pesticide. However, the increase of water flow rate from the centrifugal pump reduced gradually the mixing performance.The in-line-mixing experiments for C-type mixer and different chemicals with oil-based water-soluble liquid and non-water-soluble liquid were conducted. For the oil-based water-soluble liquid (Prime oil) and non-water-soluble liquid (Silicon oil), the C-type mixer had the highest mixture uniformity index among the four mixers. Also, the C-type mixer had a high uniformity index for mixing the non-water-soluble liquid (Silicon oil) than the oil based water-soluble liquid (Prime oil).This research established relationships among mixture uniformity, amount of simulated pesticides injected, physical properties of simulated pesticides, configurations of in-line mixers, and sprayer operating conditions. It was demonstrated that mixture uniformity could be greatly improved by a proper mixer, injection point position, injection direction, and the ratio of water flow speed and the injection flow speed through the mixing chamber.更多还原