Atomization and Sprays, Vol.7, No.2, 161-181, 1997
Independent control of liquid flow rate and spray droplet size from hydraulic atomizers
Independent control of the temporally averaged liquid flow rate and the droplet size spectrum emitted from hydraulic atomizers was achieved by coupling control of liquid supply pressure and pulse-width modulation (PWM) of instantaneous nozzle flow. Experimental results for a number of atomizer types, typical of agrochemical spraying, indicated that 10:1 flow turndown ratios could be achieved at fixed liquid supply pressures. Such capability is useful when a wide range of application rate and rapid response are desired. The spray droplet volume median diameter of emitted spray could be concurrently controlled over a two- to threefold range. The technique is useful when off-target movement of spray material can be reduced by decreasing the volume fraction of spray material contained in small droplets. The dynamic control range allowed eightfold reductions in the spray volume contained in droplets less than 105 mu m diameter. The technique,vas designed for integration into spray application controllers with flow and pressure feedback loops. The technique is limited to spray applications where the nozzle flow is the predominant mechanism for atomization. Dt situations such as high-speed air flow past a nozzle, the secondary breakup of the emitted spray call reduce the effectiveness of the technique significantly.