文丘里施肥器水力学性能测试与数值模拟

发布时间：2019-01-29 20:16

【摘要】：本文通过CT扫描方法,得到了3种喉管结构,14种流道形式的文丘里施肥器。对扫描文件进行建模,后导入到CFD中进行数值模拟,最后与试验数据做对比分析,检验了数值模拟方法的合理性。对内部流场结构不同的文丘里施肥器进行了相关的测试,探究了不同喉管结构和调控方式对施肥器性能的影响。在完成了试验与数值模拟的任务基础上提出了一种文丘里施肥器的改进方案,并进行了测试分析。得出如下几点结论:(1)对于不同结构的文丘里施肥器,随着入口流量的增加,吸肥效率呈递减趋势,且随着喉管进口直径的增大,吸肥效率的递减趋势变缓;喉管进口直径越小,随着流量的增加,其吸肥效率下降越迅速。在入口流量一定时,λ=1.27时喉管的吸肥效率最大。(2)在相同的入口流量下,T型喉管的吸肥效率最大;在相同的入口流量区间内,T型喉管的吸肥效率的递减速率最大。对于不同结构的喉管,随着入口流量的增大,在不出现倒吸的情况下,喉管负压逐渐达到最小值并保持不变。T型喉管能有效的提高吸肥量,但随着入口流量的增加,进出口压差会增大。(3)对于不同的文丘里施肥器,在小比例的控制出口阀门时,入口流量对其性能的影响很大。对于具有相同收缩段、扩张段的文丘里施肥器,喉管直径越小,适应性就越强;随着喉管进口直径的增大,受出口阀门的影响就越大。在小流量范围内,喉管直径是影响喉管负压的最主要因素,随着入口流量的增大,出口阀门的影响逐步显现。λ=1时,T型喉管在出口阀门的调节范围内的性能比较强,并且强于C型和E型;当λ=1.33时,T型喉管的性能最稳定。(4)在文丘里施肥器有肥液吸入的情况下,且出口阀门在全开状态时,吸肥效率往往呈现先增加后减小的趋势。在大流量下,E型喉管的吸肥效率受出口阀门的影响较C型和T型喉管小。综合对比λ=1和λ=1.33这两种情况来看,T型喉管的性能最稳定,相对于E型和C型来讲受到来出口阀门的影响比较小。喉管进出口直径一定时,适合选用具有T型喉管结构的文丘里施肥器。(5)通过CFD数值模拟发现,最佳的收缩角在40°左右。
[Abstract]:In this paper, three kinds of throat structures and 14 kinds of Venturi fertilizer applicators were obtained by CT scanning. The scanning file is modeled and then imported into CFD for numerical simulation. Finally, the rationality of the numerical simulation method is verified by comparing with the experimental data. The Venturi fertilizer applicator with different internal flow field structure was tested, and the effects of different throat structure and regulation mode on the performance of the fertilizer applicator were investigated. On the basis of completing the task of experiment and numerical simulation, an improved scheme of Venturi fertilizer is put forward, and the test and analysis are carried out. The conclusions are as follows: (1) for the Venturi fertilizer with different structure, the fertilizer absorption efficiency decreases with the increase of inlet flow rate, and the decreasing trend of fertilizer absorption efficiency becomes slower with the increase of throat inlet diameter; The smaller the throat inlet diameter, the faster the fertilizer absorption efficiency decreases with the increase of flow rate. When the inlet flow rate is constant, 位 = 1.27, the absorption efficiency is the greatest. (2) under the same inlet flow rate, the absorption efficiency of T type pipe is the greatest, and the decreasing rate of T type pipe is the largest in the same inlet flow range. For the pipes with different structures, with the increase of the inlet flow rate, the negative pressure of the pipe gradually reaches the minimum value and remains unchanged without the appearance of suction. The T-type pipe can effectively increase the amount of absorption of fertilizer, but with the increase of the inlet flow rate, The pressure difference between inlet and outlet will increase. (3) for different Venturi fertilizer applicators, the inlet flow rate has a great influence on the performance of the outlet valve when the valve is controlled in a small proportion. For Venturi fertilizer applicator with the same contraction and expansion section, the smaller the diameter of throat, the stronger the adaptability, and with the increase of inlet diameter of pipe, the greater the influence of outlet valve is. In the small flow range, the diameter of the pipe is the most important factor affecting the negative pressure of the pipe. With the increase of the inlet flow rate, the influence of the outlet valve gradually appears. And stronger than C and E; When 位 = 1.33, the performance of T-type pipe is the most stable. (4) in the case of Venturi Fertilizer, and when the outlet valve is in full open state, the absorption efficiency of T pipe tends to increase first and then decrease. Under the condition of large flow rate, the efficiency of sucking fertilizer in E type pipe is less affected by outlet valve than that in C type and T type pipe. Compared with 位 = 1 and 位 = 1.33, the performance of T type pipe is the most stable, and it is less affected by outlet valve than that of E type and C type. When the diameter of throat inlet and outlet is constant, the Venturi fertilizer with T-shaped throat structure is suitable. (5) by CFD numerical simulation, the optimum contraction angle is about 40 掳.
【学位授予单位】：石河子大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S224.2

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