微灌滴头设计工作压力取值理论研究

Theory on the calculation of operation pressure of micro-irrigation emitters

在满足由田间微地形偏差、灌水器制造偏差、水力偏差3因素引起的灌水流量偏差率的前提下,提出了一种新的微灌滴头设计工作压力计算方法,利用该方法可以确定农田不同种植模式下微灌滴头的设计工作压力值,即在加压情况下,地面坡度为零时,首先提出毛管年费用计算公式,然后以毛管年费用为目标函数,用黄金分割搜索法求出满足灌水流量偏差率要求的滴头设计工作压力值。结果表明,田面局部高差和允许流量偏差率是影响滴头设计工作压力的关键因素,田面局部高差越大,工作压力越大,而允许流量偏差率越大,滴头设计工作压力越小。在目前耕作条件下,若以20%流量偏差率作为灌水质量指标,则棉花、温室、果园滴头设计工作压力的最大值分别为0.5,1.0和2.5 m。

A new calculation method of micro-irrigation operation pressure was developed. This method was based on the acceptable emitter flow variation which resulted from the combined effect of farmland sectional altitude difference,manufacture variation and hydraulic variation. First of all ,the equation of annual cost of the lateral was proposed. And then annual cost of the lateral ,which included material cost and annual running cost ,was used as objective function. The optimal micro-irrigation operation pressure was determined by using gold searching computer method under condition of the discharge variation being kept within acceptable limits. The research indicated that the most important factors affecting the micro-irrigation operation pressure were farmland sectional altitude difference and the acceptable emitter flow varia- tion. The bigger the farmland sectional altitude difference was, the bigger the micro-irrigation operation pressure was. The smaller the acceptable emitter flow variation was,the bigger the micro-irrigation operation pressure was. The maximum micro-irrigation operation pressures on the cotton land ,orchard and hothouse were 0.5,1.0 and 2.5 m respectively.