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.