Abstract: A variable performance valve for use in a fuel nozzle is presented. The valve includes a spring, an inner spool having a port, an outer sleeve, and an orifice, which in a fuel nozzle application may be a calibration orifice. In a low flow condition, the inlet to downstream pressure is the spring force divided by the area on which the pressure acts. At low flow the orifice does not cause any appreciable pressure drop. As the flow increases, a pressure drop develops across the orifice. Since the pressure drop across the valve cannot be greater than the spring force divided by valve area, the valve is forced to open to compensate. As flow is increased, the valve will stroke completely open and the pressure drop at the port becomes negligible and the pressure drop across the orifice is nearly 100% of the pressure drop across the valve.

Abstract: A variable performance valve for use in a fuel nozzle is presented. The valve includes a spring, an inner spool having a port, an outer sleeve, and an orifice, which in a fuel nozzle application may be a calibration orifice. In a low flow condition, the inlet to downstream pressure is the spring force divided by the area on which the pressure acts. At low flow the orifice does not cause any appreciable pressure drop. As the flow increases, a pressure drop develops across the orifice. Since the pressure drop across the valve cannot be greater than the spring force divided by valve area, the valve is forced to open to compensate. As flow is increased, the valve will stroke completely open and the pressure drop at the port becomes negligible and the pressure drop across the orifice is nearly 100% of the pressure drop across the valve.