Pumping and metering system

A fuel metering system cooperating with an electronic fuel control adapted to monitor and select the fuel flow of a turbine type of power plant, the combination including a source of fuel, fuel connecting means interconnecting said source and said power plant, a power plant driven centrifugal pump, a piezoelectrically activated displacement type of pump disposed in series flow relationship to said centrifugal pump responding to said electronic control, both of said pumps being disposed in said fuel connecting means, said displacement type of pump pressurizing the fuel when the power plant is operating below a predetermined power plant operating parameter and metering said fuel above said predetermined power plant operating parameter, and said centrifugal pump solely pressurizing fuel when said displacement pump is in the metering condition of operation.

In a gas turbine power plant having a source of fuel and means for delivering a predetermined amount of fuel to the power plant including an electronic fuel control monitoring the engine operating parameters to produce an output signal, said means including an engine driven centrifugal pump and an electrically driven positive displacement pump disposed in series flow relationship downstream of said centrifugal pump, pressure regulating means responsive to the pressure up and downstream of said positive displacement pump for maintaining the pressure drop thereacross at a constant value, means responsive to said output signal for driving said positive displacement pump whereby a) during start up said positive displacement pump both pressurizes and meters said fuel and said pressure regulating means is full open such that said centrifugal pump operates without imparting a pressure to said fuel, and b) upon reaching a predetermined power plant speed said positive displacement pump meters fuel in response to said output signal and said centrifugal pump pressurizes said fuel.