The Delavan Variflo nozzle is a pressure atomizing nozzle which provides discharge rate variations without changing nozzles. This is accomplished by the bypass principle. With constant inlet supply pressure and the bypass (return line) closed, the nozzle operates as a simplex atomizing nozzle. For a reduced discharge flow the bypass line is opened and part of the fuel is allowed to return to the tank. The advantage is reduced flow without deterioration of the spray quality. The key advantage of the Variflo over a simplex nozzle (like Delavan\'s oil burner nozzles) is flexibility; larger turndown ratios with better atomization. With the Variflo nozzle, using a constant supply pressure, the discharge flow rate varies approximately as the square of the bypass pressure. This means that at minimum flows the atomization pressure is reduced approximately 34%.