Effect of strainer type, spray pressure, and orifice size on the discharge coefficient of standard flat-fan nozzles

Authors: BAHADIR SAYINCI

Abstract: The aim of this study was to determine the effect of nozzle strainer type (cylindrical, ball check, slotted, and cup screen type), spray pressure, and nozzle orifice size on the discharge coefficient (C_d) of standard flat-fan nozzles of different nominal sizes (from 02 to 06) and 110° spray angle. The flow rates measured for each nozzle orifice size and strainer type combinations were determined at five different spray pressures (2.0, 3.5, 5.0, 6.5, and 8.0 bars). In the study, size, shape, and area measurements concerned with nozzle geometry were performed and the differences between nozzles of different nominal sizes were revealed. Some of these data were also used to determine the liquid inlet and outlet velocity, discharge coefficient, and minimum spray pressure required for the atomization of nozzles with different strainer types. The liquid inlet and outlet velocity ranged from 4.38 to 11.75 m s^-1 and 20.49 to 41.72 m s^-1, respectively, depending on the spray pressures. The nozzles used with the cup screen and slotted strainers had identical velocity data as the same nozzles without strainers. The cylindrical and ball check strainers had a limiting effect on liquid inlet and outlet velocity, especially for 04 and 06 sizes. The C_d means of the nozzles with cup screen and slotted strainers, and of those without strainers, ranged from 0.874 to 0.980, and the differences between their means were found to be statistically insignificant for each spray pressure and orifice size. The C_d means of the nozzles with cylindrical and ball check strainers were 0.850-0.961 and 0.811-0.963, respectively. The C_d of the standard flat fan nozzles without strainer had a tendency to decrease with the increasing spray pressure, while the C_d means of the nozzles with ball check strainer moderately increased. For the complete atomization, the minimum pressure requirements of the orifices of 02 and 06 size without strainer were 2.03 and 0.99 bars, respectively, corresponding to flow rates of 0.64 and 1.33 L min^-1. The required spray pressure for the nozzle with ball check strainer was found to be higher than that of the other strainer types.

Keywords: Flow rate, nozzle inlet velocity, nozzle outlet velocity, projected area, pressure exponent

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