Variable delivery, positive displacement fuel pump hydromechanical control arrangement e.g. for aircraft gas-turbine engine

摘要

A hydromechanical control system for a variable delivery, positive displacement fuel pump includes a variable area orifice metering window through which fuel from the pump outlet passes on its way to a gas turbine aircraft engine. The fuel pressures on either side of the fuel metering window are ported to corresponding sides of a spool of a pump control valve. The position of the valve spool controls the fuel flow to either side of a pump control actuator, whose movement varies the displacement of the pump. A bypass fuel flow upstream of the fuel metering valve is also ported to the pump control valve. During steady-state pump operation, a relatively small and constant value of fuel flow is bypassed through the pump control valve and back to the pump inlet. However, upon increasing or decreasing pump speed transients, the bypass fuel flow is increased or decreased in a proportional amount. In this way, improved control of the pump during transient conditions is achieved.