| 摘要 |
A fuel system comprises a first, variable displacement fuel pump (16) operable to supply fuel through a metering valve to an engine, a control servo (50) operable to control the operation of the first pump (16), a pressure drop control valve (PDCV) (68) responsive to a pressure drop across the metering valve (20), a second fuel pump (26), and a spill valve (32) movable between an open position in which substantially all of the fuel supplied by the second fuel pump (26) is returned to an inlet side thereof, and a closed position, or partially closed position, wherein a proportion of the fuel supplied by the second pump (26) is delivered to the engine. |
