| Thin wall micro spray belt is fast developing water saving irrigation equipment.It has the advantagers of convenient installation,time-saving and labor-saving,strong anti block ability.It has become one of the most popular water-saving irrigation methods for farmers.At present,micro spray belt is widely used.predecessors have been studied for it,but there is no uniform standard for their hydraulic performance.This paper through survey the products of micro spray belt,and analyses the main types and usage and the related hydraulic performance of micro spray belt at home and abroad.Hydraulic performance experiment were started for soft plasticthin wall micro spray belt.Based on the hydraulic theory and experimental results,to studied the working pressure,degree of homogeneity,paving width and frictional head loss of thin wall micro spray belts,The working pressure and the related calculation parameters of orifice outflow for thin wall micro spray belts were determined,put forward calculation formulas of the sprinkler width and the frictional head loss for thin wall micro spray belt and the extreme laying length of the thin wall micro spray belt at different slopes,in order to provide guidance for practical engineering.The main research results are as follows:(1)The working pressure of the thin wall micro spray belt was determined.,the blasting pressure point of the thin wall micro spray belt was obtained through the test.According to the relevant stabdard,Safe Operation and Economical Savings,taking 2 as the optimal safety factor to calculate the working pressure point of the thin wall micro spray belt with the pipe diameter of N43~N64 mm,which provides a reference for the practical engineering.(2)The relationship between working pressure and orifice discharge of the thin wall micro spray belt is established.,by controlling the variable method to obtain thin wall micro spray belt about experiment date about outlet flow rate of the orifice,It is found that the outlet flow rate increases with pressure and pore diameter.for the same type the thin wall micro spray belt,the pressure at the head end is constant,the outlet flow rate is gradually decrease with the increase of the length.Through the analysis of R software,to obtaine the relationship between flow rate and pressure.Put forward the parameters of the empirical formula and the theoretical formula of outlet flow rate of the orifice for thin wall micro spray belt.It is found that the flow regime index of the thin wall micro spray belt varies from 0.5 to 0.6,so orifice outflow belongs to turbulent outflow.Finally,the orifice outflow formula is compared and analyzed.It is found that there is little difference between the theoretical formula and the empirical formula.For the convenience of calculation,the empirical formula may be used for calculation.(3)The variation of uniformity of the thin wall micro spray belt was studied.Taking the length and pressure as the main factors,To open-minded the longitudinal and transverse uniformity tests of micro-sprinkler belts under different lengths and pressures.Through the analysis of the longitudinal uniformity experiment of thin wall micro spray belt,it is found that the longitudinal uniform ity of thin wall micro spray belt increases with the length and pipe diameter and in the range of 1-8m waterhead,Longitudinal uniformity of micro-sprinkler belt increases first and then decreases with the increase of pressure,and the pressure point at the highest uniformity is 4-5m headit is found that the longitudinal uniformity of the thin wall micro spray belt increases with the increase of length and diameter in the range of 30-60 m.In the range of 1-8m water head,the longitudinal uniformity of micro-sprinkler belts increases first and then decreases with the increase of pressure,and the pressure point at the highest uniformity is 4-5m water head.The transverse uniformity of microstrip increases with the increase of pressure.Finally,the relative errors of longitudinal and transverse uniformity are used to measure the comprehensive uniformity of Thin wall micro spray belt.The results show that the comprehensive uniformity of micro spray belt is better when the pressure is between 5 to 6 m.(4)The formula for calculating spray width of the thin wall micro spray belt was established.Taking pressure and aperture as the main factors,To experiment the spraying width of the thin wall micro spray belt with pipe diameter of N43~N64 mm.The experimental data of spraying width of the thin wall micro spray belt were obtained.It was found that the spray width increases with the increase of pressure under normal laying conditions.Finally,the relationship between pressure and spraying width was obtained by multiple regression with R software.(5)The control variable method and L9(34)orthogonal test scheme were applied to test the hydraulic performance of the frictional head loss about the thin wall micro spray belt with pipe diameter of N43 mm,N45mm,N50 mm and N64 mm.Based on the experimental data of the flow rate,length,pipe diameter and frictional head loss,this paper analyzed the influence of frictional head loss level by flow rate,length and pipe diameter and obtained the hydraulic performance parameters,put forward the frictional resistance coefficient and modified the parameters of the formula for frictional head loss and obtained parameters of thin wall micro spray belt for frictional head loss.The results show that the frictional head loss increases with the increase of the pressure and length and of spray belt;the influence of the pipe diameter,flow rate and length on the hydraulic frictional head loss decreases sequentially which F values are 90.314?26.056 and 19.041 respectively.The modified parameter of frictional head loss are used to calculate frictional head loss of the thin micro spray belt,which is more consistent with the experimental data.(6)Considering the lay slope of the thin micro spray belt,combining theory with experiment,mathematical optimization model is established under the constraint condition that the head deviation of irrigation district is not more than 20%.By solving the model,the calculate formulas are obtained which is maximum laying Length of the thin micro spray belt on slope,reverse slope and flat slope and the maximum allowable gradient of the thin micro spray belt along the slope. |
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