A dual pump improved fuel delivery system

Claim 2

The system of claim 1, wherein: said pump outlet line comprises a first branch line and a second branch line, wherein said first branch line provides fuel flow to said pressure regulating valve, and said second branch line provides fuel flow to said fuel delivery line.

Claim 3

The system of claim 2, further comprising: first check valve means, disposed between said fuel delivery line and said demand control pump means, for preventing fuel flow from said fixed displacement pump from entering the outlet of said demand control pump means; and second check valve means, disposed in said second branch line, for preventing fuel flow from said demand control pump means from entering the outlet of said fixed displacement pump.

Claim 4

The system of claim 1, further comprising: an electric motor, for driving said demand control pump means at a certain speed; and speed control means, for controlling said certain speed in response to said commanded speed signal.

Claim 5

A dual pump improved fuel delivery system providing a metered fuel flow to an aircraft gas turbine engine under the control of an electronic engine control, comprising: an inlet line, for supplying a low pressure fuel; a fixed displacement pump, operating at a speed proportional to the speed of the aircraft gas turbine engine, for pressurizing an inlet fuel flow comprising said low pressure fuel, and for providing a pressurized output fuel flow in a pump outlet line; a demand control pump means, parallel to said fixed displacement pump and operating at a speed indicative of a commanded speed signal from the electronic engine control, for pressurizing said low pressure fuel; a fuel delivery line, disposed to receive fuel flow from two or more sources including said fixed displacement pump and said demand control pump means; a fuel metering valve, for metering fuel from said fuel delivery line with a variable metering valve area controlled by the electronic engine control in order to provide a metered fuel flow into a metering valve outlet line; a pressure regulating valve, for bypassing a portion of said pressurized output fuel flow within said pump outlet line to a bypass line coupled to said inlet line in order to maintain a fixed pressure drop across said fuel metering valve when said pressurized output fuel flow enters said fuel metering valve; and valve means, responsive to the electronic engine control and parallel to said pressure regulating valve, for shunting fuel flow from said pump outlet line to said bypass line in order to control whether fuel flow from said fixed displacement pump or fuel flow from said demand control pump means flows into said fuel delivery line.

Claim 6

The system of claim 5, further comprising: first check valve means, disposed between said fuel delivery line and said demand control pump means, for preventing fuel flow from said fixed displacement pump from entering the outlet of said demand control pump means; and second check valve means, disposed in said pump outlet line, for preventing fuel flow from said demand control pump means from entering the outlet of said fixed displacement pump.

Claim 7

The system of claim 5, further comprising: an electric motor, for driving said demand control pump means at a certain speed; and speed control means, for controlling said certain speed in response to said commanded speed signal.

Claim 8

A dual mode improved fuel delivery system providing a metered fuel flow to an aircraft gas turbine engine under the control of an electronic engine control, comprising: fuel supply means, for supplying a low pressure fuel; a fixed displacement pump, operating at a speed proportional to the speed of the aircraft gas turbine engine, for pressurizing an inlet fuel flow comprising said low pressure fuel, and for providing a pressurised output fuel flow in a pump outlet line; a demand control pump means, operating parallel to said fixed displacement pump and at a speed indicative of a commanded speed signal from the electronic control, for pressurizing said low pressure fuel; valve means, responsive to the electronic engine control, for routing the fuel flow from either said fixed displacement pump or said demand control pump means into a delivery line, for routing fuel flow from the fixed displacement pump to said delivery line when the engine is being started, and for routing fuel flow from the demand control pump means to said delivery line in other engine operating modes; a fuel metering valve, disposed to receive fuel from said delivery line, comprising a variable metering valve area controlled by the electronic engine control in order to provide a metered fuel flow into a metering valve outlet line; and a pressure regulating valve, for maintaining a fixed pressure drop across said fuel metering valve by bypassing a variable amount of a pressurized fuel from the outlet of said fixed displacement pump to the inlet of said fixed displacement pump when said valve means routes fuel flow from said fixed displacement pump to said delivery line where said pressurized fuel is mixed with said low pressure fuel to create said inlet fuel flow.

Claim 9

The system of claim 8, wherein: said pump outlet line comprises a first branch line and a second branch line, wherein said first branch line provides fuel flow to said valve means and said pressure regulating valve, and a second branch line provides fuel flow to said fuel delivery line;

Claim 10

The system of claim 9, further comprising: first check valve means, disposed between said fuel delivery line and said demand control pump means, for preventing fuel flow from said demand control pump means from entering the outlet of said fixed displacement pump; and second check valve means, disposed in said second branch line for preventing fuel flow from said fixed displacement pump from entering the outlet of said demand control pump means.

Claim 11

The system of claim 8, further comprising: an electric motor, for driving said demand control pump means at a certain speed; and speed control means, for controlling said certain speed in response to said commanded speed signal.

Claim 12

A dual pump improved fuel delivery system providing a metered fuel flow to an aircraft gas turbine engine under the control of an electronic engine control, comprising: an inlet line, for supplying a low pressure fuel; a fixed displacement pump, operating at a speed proportional to the speed of the aircraft gas turbine engine, for pressurizing an inlet fuel flow comprising said low pressure fuel, and for providing a first pressurized output fuel flow in a pump outlet line; a first check valve, responsive to the electronic engine control and disposed to receive said first pressurized output fuel flow, for operating either open or closed; a demand control pump means, parallel to said fixed displacement pump and operating at a speed indicative of a commanded speed signal from the electronic engine control, for pressurizing said low pressure fuel, and for providing a second pressurized output fuel flow; a second check valve, responsive to the electronic engine control and disposed to receive said second pressurized output fuel flow, for operating either open or closed; a fuel delivery line, disposed to receive fuel flow from two or more sources including said first check valve and said second check valve where said first check valve and said second check valve can not be open at the same time; a fuel metering valve, for metering fuel from said fuel delivery line with a variable metering valve area controlled by the electronic engine control in order to provide a metered fuel flow into a metering valve outlet line; and a pressure regulating valve, for bypassing a portion of said first pressurized output fuel flow within said pump outlet line to a bypass line coupled to said inlet line in order to maintain a fixed pressure drop across said fuel metering valve when said first check valve is open.

Claim 13

The system of claim 12, further comprising: an electric motor, for driving said demand control pump means at a certain speed; and speed control means, for controlling said certain speed in response to said commanded speed signal.