INDEPENDENT CONTROL OF LIQUID FLOW-RATE AND SPRAY DROPLET SIZE FROM HYDRAULIC ATOMIZERS

Independent control of the temporally averaged liquid flow rate and th e droplet size spectrum emitted from hydraulic atomizers was achieved by coupling control of liquid supply pressure and pulse-width modulati on (PWM) of instantaneous nozzle flow. Experimental results for a numb er of atomizer types, typical of agrochemical spraying, indicated that 10:1 flow turndown ratios could be achieved at fixed liquid supply pr essures. Such capability is useful when a wide range of application ra te and rapid response are desired. The spray droplet volume median dia meter 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 spr ay material contained in small droplets. The dynamic control range all owed eightfold reductions in the spray volume contained in droplets le ss than 105 mu m diameter. The technique,vas designed for integration into spray application controllers with flow and pressure feedback loo ps. The technique is limited to spray applications where the nozzle fl ow is the predominant mechanism for atomization. Dt situations such as high-speed air flow past a nozzle, the secondary breakup of the emitt ed spray call reduce the effectiveness of the technique significantly.