Study On Hydraulic Performance Of Drip Irrigation Tape Under Low Pressure Water Supply

Low-pressure water supply is a research direction of high-efficiency and energy-saving irrigation technology,which has the advantages of saving water,low energy consumption and convenient management.But at present,the technology mostly simulates the hydraulic performance of low-pressure drip irrigation theoretically,and seldom compares and analyses the difference of its hydraulic performance.Based on the current research situation,four different types（q=1.38 L/h,2.50L/h,3.00 L/h,3.20 L/h;S=0.30 m）were used in this study to install patch-type drip irrigation tapes.In the low pressure mode（1⁶ m）and the normal pressure mode（10 m or more）,the pressure-flow relationship is measured,and the pressure-flow function model of the low pressure mode is established;Three drip irrigation tapes with different dripper spacing（S=0.30 m,0.20 m,0.15 m）q=1.38 L/h were selected to study the hydraulic performance of drip irrigation tapes with different laying lengths（L=80m,100 m,120 m,150 m）under low pressure mode（2⁶ m）,and determine the head loss and the maximum allowable laying length of drip irrigation tapes under low pressure（L=80 m,100 m,120 m,150 m）.The main results of the study are as follows:（1）Under the low pressure water supply mode,the pressure drop has a great influence on the flow pattern of different drippers.With the increase of the rated flow rate of drip irrigation tape,it shows a trend of sawtooth reduction.In order to ensure the uniformity of irrigation,drip irrigation tape with larger drip flow rate should be selected.（2）When the four drip irrigation tapes were operated in the low pressure water supply mode,the dripper manufacturing deviation decreased with the increase of pressure in a wavy manner,but changed more gently under the normal pressure mode（more than 10 m）.The dripper manufacturing deviation of the four drip irrigation tapes was the largest when the import pressure was 1 m,and the import pressure should not be less than 1 m to ensure the uniformity of irrigation.（3）Using the direct and indirect methods to establish the pressure-flow model of the conventional inlay-type drip irrigation tape in the low-pressure water supply mode,R² is greater than 0.9,and the fitting effect is better.（4）Through the field test,it is proposed that the appropriate inlet pressure is 2⁴ m when the A-type drip irrigation tape is operated in the low-pressure water supply mode.（5）When operating in the low-pressure water supply mode,the laying length is in the range of80¹20 m.With the increase of the inlet pressure,the uniformity of Cu increases,but the change is not big.When the laying length is 150 m,the uniformity of Cu with the increase of pressure firstly decreases and then increases;the larger the distance between the dripper,the better the uniformity of irrigation Cu,I₁ type>I₂ type>I₃ type;the longer the laying length,the uniformity of irrigation the worse.（6）Using SPSS 22.0 statistical analysis software to analyze the influence of laying length,inlet pressure and dripper spacing on the uniformity in the test,and obtain the confidence that the laying length is low pressure water supply under the confidence of significantα=0.05.The effect of irrigation uniformity is the most significant.（7）Calculate the head loss of the drip irrigation tape with the Brassie’s formula.The calculated value is not much different from the actual value.The calculated value of I₁（S=0.30 m）type is larger than the measured value,and the type I₂（S=0.20 m）the calculated value is in good agreement with the measured value.The calculated value of I₃ type（S=0.15 m）is smaller than the measured value.The head loss of the inlaid patch drip irrigation tape is less calculated by the Brassie’s formula.（8）Under the low-pressure water supply mode（2⁶ m）,the linear formula is obtained,which can accurately calculate the maximum laying length of the drip irrigation tape when calculating the low-pressure water supply mode.