Pressure-compensating Emitters Research Articles

Flow rate dynamics of pressure-compensating drippers under clogging effect

ABSTRACT The clogging dynamics of pressure-compensating drippers is still poorly addressed, and its understanding is quite important to control clogging. The aim of this study was to evaluate the flow performance of pressure-compensating drippers under clogging effect. Eight pressure-compensating emitters, model J-SC Jain PC-PLUS with nominal flow rate of 2.2 L h-1 were evaluated. The tests were run for 8 h d-1 for 4 weeks, a total of 160 h. Every 40 h, the concentration and granulometry of suspended particles were increased, by adding 125 mg L-1 of solids, composed of sand. The flow rate of the emitters was determined using a weight measurement system. Flow rate variations of the emitters did not follow a defined pattern. Clogging seems to occur randomly and abruptly. Sometimes the flow rate exceeded the nominal value (maximum relative flow rate of 182%) and other times it was lower than the nominal value (minimum relative flow rate of 0%).

Modeling the future of irrigation: A parametric description of pressure compensating drip irrigation emitter performance.

Drip irrigation is a means of distributing the exact amount of water a plant needs by dripping water directly onto the root zone. It can produce up to 90% more crops than rain-fed irrigation, and reduce water consumption by 70% compared to conventional flood irrigation. Drip irrigation may enable millions of poor farmers to rise out of poverty by growing more and higher value crops, while not contributing to overconsumption of water. Achieving this impact will require broadening the engineering knowledge required to design new, low-cost, low-power drip irrigation technology, particularly for poor, off-grid communities in developing countries. For more than 50 years, pressure compensating (PC) drip emitters—which can maintain a constant flow rate under variations in pressure, to ensure uniform water distribution on a field—have been designed and optimized empirically. This study presents a parametric model that describes the fluid and solid mechanics that govern the behavior of a common PC emitter architecture, which uses a flexible diaphragm to limit flow. The model was validated by testing nine prototypes with geometric variations, all of which matched predicted performance to within R2 = 0.85. This parametric model will enable irrigation engineers to design new drip emitters with attributes that improve performance and lower cost, which will promote the use of drip irrigation throughout the world.

Performance of pressure-compensating emitters using treated sewage effluent for irrigation

ABSTRACT This study aimed to evaluate the flow variation of pressure-compensating emitters using treated sewage effluent (TSE). A drip irrigation system with four types of pressure-compensating emitters (G1 - Naan Dan Jain Model Top Drip, G2 - Naan Dan Jain Model Naan PC, G3 - Drip-Plan, G4 - Naan Dan Jain Model Naan Amnon) was installed with TSE from the sewage treatment station, filtered through a disc filter (120 mesh). Seven evaluations of flow rate of the drippers were performed (0, 100, 200, 300, 400, 500 and 600 h of operation) operating at 100 kPa. The experimental design was completely randomized in a 4 x 7 factorial arrangement (4 models and 7 times) with four replicates and Tukey test to compare the means. The relative flow rate (Qr), flow rate coefficient of variation (CVQ) and degree of clogging (DC) were determined. It was found that the models of emitters were not much susceptible to clogging during the operation of the system. The G4 model showed better performance compared with the others, presenting mean Qr of 99.92%, CVQ of 2.69% and DC of 1.19% at the end of the experiment. The results revealed that emitters are affected by the time of use of TSE.

Discussion of “Statistical Analysis of Non-Pressure-Compensating and Pressure-Compensating Drip Emitters” by H. Perea, J. Enciso-Medina, V. P. Singh, D. P. Dutta, and B. J. Lesikar

Discussion of “Statistical Analysis of Non-Pressure-Compensating and Pressure-Compensating Drip Emitters” by H. Perea, J. Enciso-Medina, V. P. Singh, D. P. Dutta, and B. J. Lesikar

Closure to “Statistical Analysis of Non-Pressure-Compensating and Pressure-Compensating Drip Emitters” by H. Perea, J. Enciso-Medina, V. P. Singh, D. P. Dutta, and B. J. Lesikar

Closure to “Statistical Analysis of Non-Pressure-Compensating and Pressure-Compensating Drip Emitters” by H. Perea, J. Enciso-Medina, V. P. Singh, D. P. Dutta, and B. J. Lesikar

Fluid-Structure Interaction Analysis on Pressure-Compensating Emitters

<abstract><title><italic>Abstract. </italic></title> Pressure-compensating (PC) emitters can maintain a constant discharge within a wide range of working pressures, thus they have extensive application prospect in mountain regions where the hydraulic pressure in irrigation systems often changes greatly. Although the rapid design method for non-PC emitters based on CFD is quite mature at present, common CFD method is not suitable for the design of PC emitters because a two-way coupling interaction exists between the fluid flow and elastic diaphragm. In order to improve the design accuracy and efficiency of PC emitters, the fluid-structure interaction (FSI) analysis was studied in this paper. In the FSI analysis procedure, adaptive mesh repair was adopted to refine the distorted fluid mesh. Incremental method and displacement-pressure finite element formula were used for the nonlinear analysis of the incompressible material. In this article, SST K-ω turbulence model was used for the fluid analysis, while contact analysis method and Neo-Hookean Mooney-Rivlin rubber material model were adopted for the structure analysis. The results showed that the discharge was adjusted by a very small deformation of the diaphragm to reach a steady state. At last, compared with the test results carried out using the test samples made by rapid prototyping, the analyzed values were a little larger while the maximum relative deviation was within 2.5%. This verified that PC emitter’s discharge could be predicted by FSI analysis accurately. In conclusion, FSI analysis is an efficient way to improve the design accuracy and reduce the test times for PC emitters.

Impact of water temperature and structural parameters on the hydraulic labyrinth-channel emitter performance

The effects of water temperature and structural parameters of a labyrinth emitter on drip irrigation hydraulic performance were investigated. The inside structural parameters of the trapezoidal labyrinth emitter include path width (W) and length (L), trapezoidal unit numbers (N), height (H), and spacing (S). Laboratory experiments were conducted using five different types of labyrinth-channel emitters (three non-pressure compensating and two pressure-compensating emitters) commonly used for subsurface drip irrigation systems. The water temperature effect on the hydraulic characteristics at various operating pressures was recorded and a comparison was made to identify the most effective structural parameter on emitter performance. The pressure compensating emitter flow exponent (x) average was 0.014, while non-pressure compensating emitter’s values average was 0.456, indicating that the sensitivity of non-pressure compensating emitters to pressure variation is an obvious characteristic (p&lt;0.001) of this type of emitters. The effects of water temperature on emitter flow rate were insignificant (p&gt;0.05) at various operating pressures, where the flow rate index values for emitters were around one. The effects of water temperature on manufacturer’s coefficient of variation (CV) values for all emitters were insignificant (p&gt;0.05). The CV values of the non-pressure compensating emitters were lower than those of pressure compensating emitters. This is typical for most compensating models because they are manufactured with more elements than non-compensating emitters are. The results of regression analysis indicate that N and H are the essential factors (p&lt;0.001) to affect the hydraulic performance.

Eight emitters clogging characteristics and its suitability under on-site reclaimed water drip irrigation

Drip irrigation is the most effective and reliable method for reclaimed water irrigation. The water usually contains a lot of suspended particles, metal salt ions, organisms and microbial communities, which will enhance the possibility of emitter clogging or more complex clogging mechanism. Emitter clogging has become one of the key problems to the application and popularization of the drip irrigation technology. In this paper, we selected four kinds of pressure-compensating emitters and four kinds of non-pressure-compensating emitters, and executed the experiment of drip irrigation with on-site reclaimed water treated with cyclic activated sludge system (CASS). The emitter discharge ratio variation (Dra), coefficient of uniformity (CU) and clogging rate distribution were analyzed to evaluate the emitter clogging characteristics after eliminating the effect of temperature and pressure on the emitter outflow by data correction. The results showed that Dra and CU varied in three periods as system operation. The beginning of experiment was the fluctuated balance period, Dra and CU recurrent fluctuated in 5 %, and the emitters clogged at some spots after the system run 36–48 h. Then the two parameters varied linearly in 60–108 h, tuning into the initiate linear period, as the non-pressure-compensating emitters got an obvious linear change than the pressure-compensating ones with the gradient changed from −0.094 to 0.042 and −0.073 to 0.047, respectively. Some of the emitters have a significant difference on these two parameters at this stage. After the restarting in the second year, Dra and CU decreased sharply. The maximum decrement was, respectively, 9.6 and 10.7 %. Then they varied in line with a greater slope degree as all emitters reached the significant level, the gradient ranges were −0.176 to 0.115 and −0.216 to 0.117, respectively. This stage was called the accelerated linear period. Seriously clogged and completely clogged emitters appeared, and both Dra and CU dropped down to 38.7 and 41.5 %. Various degrees of clogged emitters often emerged in the end part of lateral at first then propelled to the head gradually, the completely clogged emitters in the end accounted for more than 73.0 % when the system run 540 h. Comprehensively considered, the pressure-compensating emitters and cusp-shaped saw-tooth non-pressure-compensating emitters with short flow path are recommended in reclaimed water drip irrigation. These researches are aimed to provide references explaining the emitter clogging mechanism of reclaimed water drip irrigation as well as its technological application and popularization.

Rapid Development of Novel Integrated Pressure Compensating Emitters

Although pressure compensating emitters (PCE) have many advantages, they are difficult to develop and very costly. Traditional PCE are composed of emitter structures and compensating diaphragms. Their manufacture is very difficult and time-consuming. In this paper, we invented novel PCE with variable flow channels, which are designed as integrated structures with pressure compensating barriers, and manufactured three of them with different structures based on the rapid prototyping/rapid tooling technology. The pressure-flow test showed their behavior indexes were 0.009, 0.008 and 0.011, respectively, indicating this type of novel PCE have remarkable compensating effect.

Biofilm development in micro-irrigation emitters for wastewater reuse

Laboratory experiments were carried out to investigate bioclogging on three types of online emitters using synthetic wastewater filtered at 10 μm (COD = 200 mg L−1). The three types of emitters were as follows: non-pressure-compensating emitters delivering 2 L h−1 (NPC2), non-pressure-compensating emitters delivering 4 L h−1 (NPC4) and pressure-compensating emitters delivering 2.2 L h−1 (PC). They were plugged on two parallel pipe diameters (16 and 20 mm). Emitter performance was followed by flow rate measurements. The results showed that PC emitters seemed to be more sensitive to clogging than NPC emitters. Biofilm was observed mainly on NPC flow paths and PC membranes; its presence was also confirmed by the assessment of different water quality parameters such as total organic carbon and pH. Experimental results compared with a model designed with computational fluid dynamics Software (ANSYS Fluent®) showed relations between biofilm development and velocity distribution on NPC flow paths. Finally, pipe diameter also appeared to be a parameter inducing emitter clogging.

Quantitative relationship between biofilms components and emitter clogging under reclaimed water drip irrigation

Emitter clogging is a bottleneck to restrain the application and popularization of reclaimed water drip irrigation technology, and it is tightly related to the formation of biofilms attached on drip irrigation emitters. However, there is still no quantitative description about the relationship between biofilms components and emitter clogging. Based on the reclaimed water drip irrigation experiment, the characteristics of biofilms attached on 7 kinds of emitters under reclaimed water drip irrigation have been systematically explored with phospholipid fatty acids (PLFAs) and other microbiological testing methods, and quantitative relationship between biofilms components and emitter clogging was analyzed. The results showed that emitter clogging degree and biofilms components revealed an increasing trend with the drip irrigation system running, which could be regarded as the “quick-slow-quick-slow” increasing trend. Biofilms exhibited a rapid growth after restarting in the 2nd year. The dry weights (DWs), PLFAs, and extracellular polymers (EPS) of biofilms attached on the emitters could reach up to 0.133 g, 100.83 μg, and 1,645.04 μg, respectively, after accumulatively ran for 540 h. DWs of biofilms in different positions such as head, middle, and end parts of the lateral also revealed a increasing trend. Meanwhile, biofilms in the pressure-compensating emitters grew less than that in the non-pressure-compensating emitters. During the initial 540 h of the system running, DWs, PLFAs, and EPS of attached biofilms had a obvious negative linear correlation (R2 > 0.85) with emitter discharge ratio variation (Dra) and coefficient of uniformity (CU), which could describe the drip irrigation emitter clogging mechanism well. Furthermore, PLFAs reflected the type and quantity of microorganisms in attached biofilms, and sticky EPS secreted by microorganisms could link the microorganisms with absorbed particulates together and formed the stable biofilm structure. As PLFAs reflected the comprehensive effect of microorganisms, particulates and EPS on emitter clogging, and presented the highest negative linear correlation with Dra (R2 = 0.93), it is most appropriate to reflect emitter clogging mechanism. These results can provide a theoretical basis for exploring emitter clogging mechanism and promoting the application of reclaimed water drip irrigation technology.

Comparison of Clogging in Drip Emitters During Application of Sewage Effluent and Groundwater

Drip irrigation can be an efficient and safe method of applying water from sewage effluent; however, clogging of emitters is one of the most serious problems associated with drip irrigation systems using sewage effluent. The objectives of this study were to investigate the temporal variations of the emitter discharge rate and the distribution of clogged emitters in the system and to quantify the impact of emitter clogging on system performance. In the experiments, six types of emitters with or without a pressure-compensation device and two types of water sources (stored secondary sewage effluent and groundwater) were assessed by measuring the emitter discharge rate of the system at approximately ten-day intervals. The total duration of irrigation was 83 days, with a daily application of 12 h. The water source had a very significant influence on the level of drip emitter clogging. Of all the emitters tested over the entire period of the experiments, the emitters applying sewage effluent were clogged much more severely, producing a 26% lower average mean discharge rate than those applying groundwater. Different types of emitters had different susceptibilities to clogging, but the clogging sensitivity was inversely proportional to the pathway area in the emitter and the emitter's manufacturing coefficient of variability (Mfg CV). The distribution of clogged emitters along the lateral was controlled by the emitter type and the water source. For groundwater application, the clogged emitters tended to be generally located at the terminals of the laterals for emitters without a pressure-compensation device, while randomly distributed clogged emitters were found for pressure-compensating emitters. A more random distribution of clogged emitters was found for the sewage application. Clogging of emitters could seriously degrade system performance. The values of the uniformity coefficient (CU) and the statistical uniformity coefficient (Us) decreased linearly with the mean clogging degree of the emitters. To maintain a high system performance, more frequent chemical treatments should be applied to drip irrigation systems applying the sewage effluent than to systems applying the groundwater.

Emitter discharge variability of subsurface drip irrigation in uniform soils: effect on water-application uniformity

Emitter discharge of subsurface drip irrigation (SDI) decreases as a result of the overpressure in the soil water at the discharge orifice. In this paper, the variation in dripper discharge in SDI laterals is studied. First, the emitter coefficient of flow variation CVq was measured in laboratory experiments with drippers of 2 and 4 L/h that were laid both on the soil and beneath it. Additionally, the soil pressure coefficient of variation CVhs was measured in buried emitters. Then, the irrigation uniformity was simulated in SDI and surface irrigation laterals under the same operating conditions and uniform soils; sandy and loamy. CVq was similar for the compensating models of both the surface and subsurface emitters. However, CVq decreased for the 2-L/h non-compensating model in the loamy soil. This shows a possible self-regulation of non-compensating emitter discharge in SDI, due to the interaction between effects of emitter discharge and soil pressure. This resulted in the irrigation uniformity of SDI non-compensating emitters to be greater than surface drip irrigation. The uniformity with pressure-compensating emitters would be similar in both cases, provided the overpressures in SDI are less than or equal to the compensation range lower limit.

Performance Evaluation of Drip Irrigation System Using Sweet Corn

Gravitational drip irrigation system was developed using available materials. The system consisting of 4.0 l/hr Netafim pressure-compensating emitters was used to irrigate 0.0015 ha of land where sweet corn was planted under variable water applications in a randomised complete block design with three treatments. Treatment one (W1) received water once per week, treatment two (W2) received water twice per week, while third treatment (W3) received water thrice per week. W1 received 229mm per emitter; W2 received 437mm per emitter, while 653mm per emitter was applied to W3 throughout the experimentation period. Total biomass yield including bulk weight, stem weight, root weight and cob yield were determined using top loading digital weighing balance. Results obtained which were subjected to statistical analysis at 5% significant level show that there were significant differences in the crop growth, biomass and cob yield. Watering thrice per week resulted in the highest leaf area, plant height, root depth and weight. However, watering twice per week provided the highest fresh weight and cob yield.The trend in biomass yield showed that W2 performed better. Watering twice per week appeared optimum for cultivation of sweet corn during water scarce season in Ibadan, Nigeria. Keywords: Drip Irrigation, Agronomic parameters, Corn, Evaluation. Journal of Applied Science, Engineering and Technology Vol. 6 (1) 2006 pp. 16-21

Performance of Wastewater Subsurface Drip Emitters at Low and Normal Pressure

Subsurface drip distribution is an important on-site wastewater treatment technique widely used with various soil types and restricted site conditions. This study evaluated the performance of five subsurface wastewater drip products under eight pressures, ranging from 0 to 310 kPa. Results showed that Netafim Bioline pressure-compensating emitters (Netafim Irrigation Inc., Fresno, California) had an application uniformity coefficient of 95% and a coefficient of variance (C(v)) of 4.9%. The average uniformity coefficient of Geoflow Wasteflow products (Geoflow USA, Charlotte, North Carolina) was 94.4%, with a C(v) value of 6.8%. Flowrate and pressure relationships were developed by analyzing low and normal operational pressure ranges, and R-square values ranged from 1.000 to 0.301. Geoflow pressure-compensating products were non-pressure-compensating emitters under low pressure. Netafim pressure-compensating emitters were partially pressure-compensating under low pressures. In normal operational pressure ranges, both Geoflow and Netafim products were fully pressure-compensating. Netafim pressure-compensating products were characterized as pressure-compensating over the full range of operational pressures.

Uniformity of Domestic Wastewater Effluent Application in a Subsurface Drip Distribution System

An on-site wastewater treatment project with two separate drip fields was operated for 6 years and received no maintenance. The two drip fields (with different design configurations) contained pressure-compensating emitters (PC) and non-pressure-compensating emitters (NPC), respectively, and received wastewater with an average 5-day biochemical oxygen demand concentration of 23 mg/L. Flowrates of the PC emitters reduced from rated average of 3.50 to 1.00 L/h, and the average flowrate of the NPC emitters reduced from 2.00 to 1.53 L/h. The statistical uniformities were 48 and 71%, and the uniformity coefficients were 70 and 86% for PC and NPC emitters, respectively. Significant, but incomplete, recovery was achieved with field-flushing and consecutive shock-chlorination treatments of 500 and 1000 mg/L.