自适应滴头的控制体受力分析

Force Analysis of Control Volume in Adaptive Drip Irrigation Emitter

为分析自适应滴头的自动调流功效,研究了自适应滴头控制体的弹性调节膜原始尺寸和装配后的预变形挠度,进行了弹性调节膜的综合受力分析,并运用力学的作用应力、挠度和有效面积以及接触面的密封比压等理论分析与计算方法,得出控制合力对接触面的实际密封比压。结果表明:自适应滴头弹性膜片在装配变形挠度产生的预紧力和土壤负压20 kPa等控制分力的共同作用下,产生的最小实际密封比压为0.61 MPa,而计算的理论密封比压也为0.61 MPa,符合两个接触面正向压紧密封需要的'实际密封比压不小于理论密封比压'条件,足以维持滴头的初始断水模式,并处于止水、通水的临界状态。当土壤继续干旱、土壤负压微微变大到21 kPa以上时,实际密封比压降至0.54 MPa,远小于理论密封比压,滴头即开始滴水,进入自动调节通水状态,有效地实现了自动调流功效。

For theoretical analysis effect of self-adjustment flow on the adaptive drip irrigation emitter,the original size and pre-deformation deflection after fixed of the elastic adjustment diaphragm on the control volume were designed,and the total force to the elastic adjustment diaphragm based on description of its structure and working mechanism were analyzed.The theory and calculation method of mechanics to calculate the stress,the stiffness,the effective area of diaphragm and the sealing pressure ratio at interface of rubber adjustment diaphragm and energy dissipation hole were used.Then the actual sealing pressure ratio of the together control force was obtained.Results indicated that the minimum of actual sealing pressure ratio was 0.61 MPa at the combined action of the force produced from the predeflection and soil negative pressure of 20 kPa,but the computational theoretical sealing pressure ratio was 0.61 MPa too.The former was equal to the latter in both of them and met the condition of the actual sealing pressure ratio which was equal to or greater than the theoretical sealing pressure ratio.So the minimum of actual sealing pressure ratio was enough to maintain the drip emitter at the mode of initial shutoff water,and in a critical state of shutoff water and supply water.As long as soil negative pressure was bigger slightly when soil was drought little by little and it was equal to 21 kPa only or more than it,the actual sealing pressure ratio reduced to 0.54 MPa and far less than the theoretical sealing pressure ratio.Then the adaptive drip irrigation emitter began to drip water,and entered the mode of automatic regulation.So it had realized the effective of self-adjustment drip flow really at the same time.