The performance of emitters used in trickle irrigation systems is one of the main factors affecting the irrigation efficiency. In order to achieve high emission uniformity, emitters should discharge water uniformly. Most of the existing irrigation systems are low in uniformity of emission. therefore. an evaluation of hydraulic parameters of different emitters is useful in
optimazation of system design which also would lead to an improvement of overall system performance. In this study the hydraulic and technical
characteristics of emitters made in Iran and in some other countries were
evaluated. Hundred emitters were selected from each of nine manufacturers'
products. the 48 of which were randomly picked to be used in the performance of necessary tests. Seven types which made in Iran and two made
in other countries. From the selected emitters. five were of the long path type, two pressure compensating and two the simple orifice type. Evaluation
parameters such as emitter discharge exponent (x). empirical factor (k),
pressure-discharge relation ('I - h), emitter manufacturer's coefficient of variation (Cv), emission uniformity (EU), allowable maximum pressure variation of system ( h\h)\. emitler discharge coefficient of variation (Vqs), statistical uniformity (Us), and emitter discharge coefficient of variation (Vpf)
were determined in pressure heads ranging from 5 to 20 meters. Tests were carried out according to ASAE standards for micro-irrigation systems. The
evaluation parameters were evaluated separately each under six different pressure heads (5. 8.10.12.15 and 20 meters). By obtaining four different
types of equations (exponential. power, logarithmic and linear) for each type of emitters. the proper pressure-discharge relationship was found out and
selected. Emitter performance evaluation parameters such as Vgs. Us. Vqh
and Vpf were also evaluated by using 16 emitters of each type, in the pressure heads ranging from 10 to 12 meters as related to their hydraulic properties. Finally, after the completion of the required tests and determining evaluation parameters, the expressions, excellent, good, fair, poor and unacceptable were
used to indicate emitters, evaluation and performance. From nine types of tested emitters, three were found to be excellent, one good, one fair, one poor
and the rest unacceptable.
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