Study On Hydraulic And Anti-clogging Performance Of Drip Emitter

Geometrical parameter and characteristic factors of solid particles have great influence on the hydraulic and anti-clogging performance of labyrinth flow path of drip emitter. This paper studies the main geometrical parameter such as angle, height, width, stagger and the upper width in dentation and trapezoid flow path, firstly, uses the single-phase numerical simulation of the computational fluid dynamics (CFD) technique to analyse the influence of different geometrical parameter on discharge coefficient and flow state exponent of drip emitter. Secondly, uses the two-phases numerical simulation of CFD (1% sand content ) to analyse the influence of the above mentioned geometrical parameter on the contribution regulation of sand and anti-clogging performance. Thirdly, uses the PIV(particle Tracking Velocimetry) technique which can see the small-scale flow path to observe and test the trajectories and velocities of solid particles in labyrinth flow path, and analyses the basic factors which can influence the movement characteristic of solid particles and the flow state in flow path. Finally, makes the mould to produce the drip emitter and manufacture the drip tape according to the above mentioned geometrical measurement, and tests all aspects performance under the conditions of standardization(GB/T 17187-1997 Irrigation equipment in agriculture Technique criterion and experiment methods of drip emitter, and ISO short-period testing procedure, ISO /TC23 /SC18 /WG5N4), and validates the numerical simulation results of CFD, puts forward the design methods of anti-clogging about the labyrinth flow path emitter on the basis of the hydraulic performance, by the above mentioned analyze and study, and get the main results following:1.The upper width in those parameters in trapezoid flow path is the biggest influence factor to flow rate and flow index, furthermore, the relationship each other is positive. Angle in flow path is the biggest influence factor to flow index, the relationship each other is negative, and the relationship between the discharge coefficient and angle is also negative. Other parameters such as offset value, height and width are not the biggest influence factors to flow rate and flow index, the relationship between width, offset value and flow index is negative, the relationship between height and flow index is positive, the relationship between width ,height, offset value and flow index is positive.2.The biggest sand content in flow path is changeable when the structural parameters change, when the value of the biggest sand content is increasing, the clogging ratio of drip emitters are increasing, the normal irrigation days are shorting, the results of numerical simulation and testing experiment have good consistency which testifies that it is possible to analyse the anti-clogging performance of drip emitter by the two-phases flow numerical simulation of CFD. The angle in flow path in those structural parameters is the biggest influence factor to the hydraulic and anti-clogging performance, when the angle is 60 degree, the flow index of drip emitter is smaller, and the anti-clogging performance is stronger, thus, designing the flow path it should be 60 degree.3.Amending the structure of the flow path according to the isoline of smaller sand content, canceling the higher sand content part such as upwind surface, corner and so on, after standardization, comparing the measurements of flow path and hydraulic performance with the original one, and choosing the best one as the new flow path, this method can decrease rapidly the sand content, increase the effective irrigation time, enhance the anti-clogging performance of drip emitter, comparison with the original one, the hydraulic performance improved also, this method is one new thought thread to advance the anti-clogging performance of drip emitter.4. The velocity, path length and movement trajectories of the solid particles with different diameter and density simulated and observed by the numerical simulation technique of CFD and observation technique of PIV are close, it is feasible to CFD technique to simulate the movement regulation of solid particles in labyrinth flow path. But the movement of solid particles is more close the main stream by the PIV observation, and the time of higher velocity is more long, due to the observation points by PIV are lack, the trajectories and velocity curves are consist of beelines which connect the all observation points, this method can not descript the trajectories and velocity in any locations, but CFD can do, so, combines the CFD technique with PIV technique to analyse the movement regulation of solid particles.By PIV observation, with the increasing of the angle and width in flow path, the movement regulation of the solid particles are more turbulent, and the average movement speed and path length are longer, the influence of offset value on movement regulation of solid particles is near with the angles', when the value of offset is bigger, the solid particles can go through the gap, but when solid particles enter into the vortex, the movement time is greatly long, and the average speed decrease greatly, it is not outstanding to solid particles movement regulation influenced by height.