Flow control system for a gas turbine engine

Abstract

A flow control system for controlling a variable displacement pump including a metering valve in fluid communication with the pump for metering an output of the pump. A regulating valve receives a portion of the output of the pump as a bypass flow at a first pressure, wherein an output of the regulating valve is at an interim pressure. The interim pressure is substantially equal to an average of the first pressure and a low reference pressure. An actuator sets a displacement of the pump by acting on a piston connected to a cam ring of the pump. The actuator receives the interim pressure and, thereby, the output of the variable displacement pump is determined.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The subject invention is directed generally to a system for regulating fluid flow, and more particularly, to a system for regulating the flow of liquid fuel from a variable displacement pump to a gas turbine by utilizing bypass flow. [0003] 2. Background of the Related Art [0004] Fixed delivery fuel pumps have often been over-sized to provide excessive fuel flow capacity in order to insure adequate supply to the associated engine. Consequently, under many operating conditions, large amounts of pressurized fuel are returned to the pump inlet for recirculation. The return and recirculation results in significant fuel heating due to additional energy being put into the fuel which is subsequently turned into heat as the pressure drops in the recirculation path. In modem designs, fuel heating is a critical issue because the fuel is typically used as a heat exchanger to maintain proper operating temperature. Other methods...

AI Technical Summary

Benefits of technology

[0009] It is an object of the present disclosure to increase the fuel metering unit response while maintaining acceptable stability at all operating conditions.

[0010] It is another object to provide a hydromechanical fuel metering unit for a variable displacement pump. It is still another object to provide a fuel metering unit that achieves quick and accurate response to dynamic flow conditions.

[0011] In another embodiment, the subject invention is directed to a method for metering a variable displacement pump that provides fuel to an engine, the method includes the steps of receiving fuel at a low reference pressure into the variable displacement pump, pumping the fuel through the pump such that an output of the pump is at an elevated pressure, metering the output of the variable displacement pump with a metering valve, creating a spill return flow from the output of the variable displacement pump to allow for quick response when additional fuel is required by the engine, regulating a pressure differential across the metering valve with a regulating valve. The regulating valve is in fluid communication with the spill return flow to generate an interim pressure substantially equal to an average of the spill return and the low reference pressure. The method also includes the step of adjusting a displacement of the pump with a cam actuator connected to a cam ring of the variable displacement pump for adjusting the output, wherein the cam actuator receives the interim pressure to determine a setting of the cam actuator.

Problems solved by technology

Fixed delivery fuel pumps have often been over-sized to provide excessive fuel flow capacity in order to insure adequate supply to the associated engine.

Consequently, under many operating conditions, large amounts of pressurized fuel are returned to the pump inlet for recirculation.

The return and recirculation results in significant fuel heating due to additional energy being put into the fuel which is subsequently turned into heat as the pressure drops in the recirculation path.

In modem designs, fuel heating is a critical issue because the fuel is typically used as a heat exchanger to maintain proper operating temperature.

Other methods of heat exchange are undesirable because of the associated size, weight and cost.

This slewing is a transient event that can unacceptably starve the supply of fuel to the engine.

Under such rapidly varying operating conditions, prior art pump control systems have been unable to respond quickly and adequately.

Moreover, many prior art pump control systems lack the required stability to reliably provide fuel to the engine.

So despite the advances of the state of the art, variable displacement pumps are lacking in stability and still do not respond quickly enough to varying engine demands.

As a result, poor performance and excess fuel flow are still common.

However, as noted above, such systems still contain inadequacies such as complexity.

Moreover, such systems can only achieve adequate bandwidth by delivering excessive fuel which must be recirculated.

It is also undesirable for pump control systems to include sophisticated electronics and numerous additional components that undesirably increase costs and complexity.

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