Glossary
Flow rate
Definition
Mass of fuel passed through the atomizer per unit of time, given in kg/h or, historically, in Gph.
The flow rate is the quantity of fuel the atomizer passes per hour. Industrial burners are specified in kg/h; the residential oil-burner trade still uses gallons per hour (Gph), where 1 Gph of light fuel oil corresponds to roughly 3.3 kg/h.
The figure depends on the pressure at the nozzle inlet, the viscosity and the density of the fuel, so a catalogue value is only valid at a stated pressure and viscosity. Fluid Control Instruments Ltd publishes the design range per type and confirms the actual value on the order drawing.
Because the fuel output is what the burner has to modulate, the flow rate is always quoted together with the turn-down ratio: a TYPE 32 spill-back atomizer covers 60 – 2250 kg/h at a turn-down of 1:3 – 1:5, which means it can be run anywhere between 60 and 750 kg/h at stable spray quality.