| The quality and performance of Drip irrigation emitters directly affect the operation and promotion using of drip irrigation systems, The hydraulic performance of labyrinth passage drip emitters is mainly affected by structural parameters and water flow situation. At presentthe domestic studies mainly paid attention on the dental labyrinth passage of drip emitter,while less studies on the arc labyrinth passage of drip emitter. On the low-pressure conditions, the paper point at the studies of the hydraulic performance of large size arc labyrinth passage of drip emitter.Take typeâ… andâ…¡arc labyrinth passage drip emitter as the main research object, arcing tip angle, linear flow path length, unit number or the channel width and water temperature as the main factors . In the low-pressure head conditions (H <3m), the hydraulic performance of emitter tests is tested, analyse the influence of different structural parameters and flow index, flow coefficient and flow rate, while studing also the relation between structural parameters and the local head loss, frictional head loss and Reynolds. Through the study reached the following conclusions:The sequence of all factor affect the flow rate, flow index and the flow coefficient of typeâ… : the first is the units number, followed by the arcing tip angle, the final is the linear flow passage length. The sequence of all factor affect the flow index of typeâ…¡is water temperature , channle width, linear flow passage length and the arcing tip angle. The flow rate order is channle width, water temperature , the arcing tip angleand linear flow passage length.In low-pressure conditions, the relationship between pressure and flow rate is linear, the rate of typeâ… decreased with unit number increaseing, flow rate ~ pressure curve more gentle with the pressure head increases and the greater the units number. The channel size of typeâ…¡emitter is smaller,the rate is also smaller.The flow index is in the range of 0.6 to 0.69, so changes in flow cross-section dimension no obviously effect on the flow pattern index. Channel width is 0.8mm, the arcing tip angle was negatively correlated with sharp corners, the longer linear length,the biger rate.while channel width is at 1.1 ~ 2.3mm, with the arcing tip angle increases, the flow rate increases , rate reduce with the growth of linear length. Local head loss of typeâ… emitter decreases with the pressure decreases, which show a rising trend with the units number, , but the increase trends is more gently with the units number growth,.Along the channel length of labyrinth passage ,the local head loss is not evenly distributed, but the relation of hj with n is logarithmic.In typeâ…¡of emitter, the percentage of local head loss accounted for the total head loss of model A, B, C and D of is approximately: 30%, 50%, 60% and 72%, so when the emitter structure size is relatively large, frictional head loss is the main energy dissipation way, and the local head loss is the main energy dissipation model when the size is relatively small.The relation of typeâ… emitter between Reynolds and the head pressure is a positive correlation , the Reynolds is smaller with more unit number,and the difference of Reynolds decrease as the unit number increases. Reynolds decreases as the linear length increases ,which take a growth trend with the increasing arcing tip angle. Therefore, in order to get better turbulence results ,should not take more nuit numbers ,linear length and smaller angle when designing emittert. The Reynolds is smaller as the model size of typeâ…¡emitter is smaller. |
