| Micro-irrigation technology as one of a rather rapid development of water-saving methods, in which the drip irrigation technology got a more development speed, it has got widespread attention because of its water-saving efficient. In recent years, low-pressure drip irrigation becomes popular due to it can significantly reduce investment. In this paper, we mainly use experimental methods, combined with theoretical analysis to study hydraulic characteristics of several large-diameter thin-wall low pressure drip irrigation hose, in this experiment test, under low pressure, we analysis the pressure distribution along the hose, the flow characteristics of the law, head loss, irrigation uniformity analysis and evaluations, and a pilot study of flow patterns in theoretical, and test set in the case of flat slope, in the process of water flowing towards to the end of the hose, under the effect of porous flow along the hose, head loss along the hose and local head loss, as well as pipe deformation, and so on, the flow, pressure ditribution, head loss and irrigation uniformity is changing, mainly reflects in the following specific aspects:(1) During the experiment, by the effects of the laying length of hose pipe, inlet pressure and orifice interval, the law of flow distribution along the pipe is not the same, while all show a single peak patterns. With the increase of laying length and orifice interval, the location of maximum flow value moves forward, and the changes along the pipe is more uniform; with the increase of inlet pressure, the change range also becomes small; as well, with the increase of orifice interval, the absolute difference between the first to the end appears small fluctuations, but little change.(2) Under the condition of continuous supply pressure, in the whole pipe, the pressure head along the pipe always has been reduced, and with the increase of orifice interval, the rate tends to slow down, the reduce rate of first half is about4times of the next half, in the same orifice interval, a relatively short pipe could gets a more uniform pressure distribution because of the backwater effect.(3) With the increase of inlet pressure, head loss shows a linearly downward trend, when the length of pipe is30m, the reduce rate under the inlet pressure1-3m is about2times under the inlet pressure is4-5m and its length is40m, with the decrease of orifice interval, head loss shows the same trend, and as for a longer pipe, we could use a bigger orifice interval to obtain a smaller head loss, so as to improve irrigation uniformity.(4) For low-pressure thin-wall porous hose, when the water flows in the pipe, the flow pattern is turbulent flow regime, we analyse the ralations between the ratio of measured head loss to standard values calculated by recommend code and the inlet pressure, diameter, orifice interval, and finally we get the result that head loss correction coefficient β and the inlet pressure is a significant quadratic function, as well as orifice interval, and with the diameter is a power function, that is, β is the function of inlet pressure (H), diameter (D) and orifice interval (L'), in addition, when the flow pattern is laminar flow, the specific form ofβvalue also needs to be a further research.(5) The impact of stress on Cu becomes more significant when the pipe is longer, and will appear a maximum value; Cu value increases upward generally with the orifice interval, but changes are not the same; with the diameter changes shows two trends, when the diameter is less than32mm, its change is not significant, after the diameter is more than32mm, Cu value has a slight increase, but the overall change is relatively samll.(6) In theorey, we make an analysis of flow pattern (x), using those equations we got in front text to realize a simple identification of flow patterns in drip irrigation pipes, under double role of decreasing inlet pressure and increasing pipe diameter, x value tends to increase, and tends to become laminar flow. |
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