STUDIES ON HYDRAULIC PERFORMANCE OF RAINGUN AND ITS EVALUATION
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Date
2018
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Acharya N.G. Ranga Agricultural University
Abstract
Water has a key role to play in the progressive agriculture and economic development of the country. Due to the food demands of constantly growing population at the rate of 1.95 % annually, the demand of water for agriculture is increasing. However, availability of water for agriculture sector is reducing due to stiff competition from other sectors such as industries, recreation and domestic water supply. Thus, tremendous amount of pressure lies on agriculture sector to reduce its share of water and at the same time to enhance total production by enhancing the water use efficiency.
Pressurized irrigation systems such as drip and sprinkler have been proved to be very efficient and useful in water scarce and undulated area. Amongst sprinkler irrigation systems, rain gun can be used most effectively for irrigating larger fields in short period and with minimum labour requirement. As the rain gun sprinkler system is recently adopted in India, adequate information is not available on hydraulic characteristics.
The relationships viz., pressure-radius of throw, pressure-discharge and pressure-uniformity coefficient were developed for standalone rain gun at different riser heights. The linear, logarithmic, power and exponential types of equations were fitted for these relationships. The best relationships were selected based on the value of regression coefficient. Characteristic curves were drawn for the raingun based on hydraulic performance. This is beneficial to farmers for selection of raingun based on type of nozzle size and riser height etc.
Uniformity coefficient increases with operating pressure and maximum uniformity coefficient was observed in 8mm nozzle i.e. 68 % at 3.5 kg/cm2 and 1.5 m riser height among the tested nozzles. Uniformity coefficient decreases with the increase in riser height for the tested pressures. Uniformity coefficient increases with decrease in the nozzle size for the tested pressures.
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Mobile rain gun system attached to the tractor is developed to supply the irrigation to the field where the electricity is not available to pump the water. It is evaluated to calculate the fuel consumption, discharge, pressure developed and maximum radius of throw by the system with 24 hp mini tractor and 38 hp tractors. The evaluation of mobile rain gun system attached to the tractor results that fuel consumption is 3l/h for mini tractor and 4.2 l/h for 38 hp tractor and discharge is 16 lps for mini tractor and 21 lps for 38 hp tractor. Cost of operation for irrigating with raingun per hectare with 24 hp mini tractor is Rs 1388/- and with 38 hp tractor is Rs 1237/-
The performance of rain gun irrigation system is similar to the sprinkler irrigation system except following parameters. The uniformity coefficient of the rain gun system is 64 % and the sprinkler system is 84 %. Pod yield for the raingun irrigation system is 3100 kg/ha and sprinkler system is 3340kg/ha. The water use efficiency of raingun system is 21.14 kg/ha-mm and sprinkler system is 22.79 kg/ha-mm.
The results revealed that the radius of throw of rain gun increases with operating pressure and riser height. This facilitates the scope for deciding the operating pressure to obtain the desired precipitation rate according to the soil type. However the nature of variation in radius of throw with operating pressure and riser height were different for different nozzles of rain gun. Similarly the discharge and uniformity coefficient of rain gun was found to increase with operating pressure and riser height.
Key words: Rain gun, pressure, radius of throw, discharge, uniformity coefficient, riser height, mobile rain gun.
Description
D5743
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