Patent Application
20200378315
The present disclosure relates to a fuel, and more particularly to fuel system having overspeed and thrust control malfunction protection.
A variety of systems are known in the fuel metering and fuel control field. In addition to metering fuel flow, gas turbine fuel controls must provide safety functions to assure that that the engine and aircraft operate at safe conditions. Two required safety protection functions are Overspeed (O/S) and Thrust Control Malfunction (TCM). Overspeed protection typically requires rapidly reducing fuel flow to zero, while TCM must reduce flow to an intermediate value.
The conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for fuel systems having improved complexity and reliability. There also remains a need in the art for such fuel systems and components that are economically viable. The present disclosure may provide a solution for at least one of these remaining challenges.
A fuel system with integrated thrust control malfunction and overspeed protection includes a high pressure centrifugal pump configured to receive filtered fuel and supply fuel to a metering and pressure regulating valve, wherein the metering and pressure regulating valve is configured to meter discharge of filtered fuel flow to a gas generator burner, a shut off valve downstream of the metering and pressure regulating valve movable from an open position to a fully closed position configured to provide rapid fuel flow shutoff or to a fixed intermediate position configured to reduce fuel flow to the gas turbine burner, and first solenoid and a second solenoid for controlling the shut off valve position.
The first solenoid acts independent of the second solenoid and the second solenoid acts independent of the first solenoid. The first solenoid provides a pressure to a spring side of the shut off valve to activate the shut off valve to an intermediate position. The second solenoid provides a pressure to a spring side of the shut off valve to activate the shut off valve to the closed position using a second overspeed valve. The second overspeed valve is fluidly connected to the first solenoid and to the second solenoid.
The first solenoid reduces fuel flow to the engine burner by translating the shut off valve to an intermediate position between the open position and the closed position. The intermediate position is fixed and is based on a location of a middle feedback window of the valve spool.
The second solenoid is fluidly connected to a pressure port of the second overspeed valve.
A method of overspeed and thrust control malfunction protection includes monitoring a speed of an engine and at least one aircraft characteristic using a controller or Full Authority Digital Engine Control (FADEC), detecting an engine overspeed or a thrust control malfunction, and actuating a shutoff valve from an open position to a either second intermediate position by energizing a first solenoid, thereby reducing the fuel flow to the engine burner for thrust control malfunction accommodation or actuating a shutoff valve to a closed position shutting off fuel flow to the engine burner for accommodation of a overspeed.
These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.
So that those skilled in the art to which the subject invention appertains will readily understand how to make and use the devices and methods of the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:
Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject invention. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a fuel system in accordance with the invention is shown in
Referring to
The second, O/S, solenoid 114 activates the shut off valve 110 to the closed position by translating a second overspeed valve 118. The second overspeed valve 118 is fluidly connected to the second solenoid 114. The first solenoid 112 acts independent of the second solenoid 114 and the second solenoid 114 acts independent of the first solenoid 112. Each solenoid is commanded individually by the Full Authority Digital Engine Control (FADEC). The FADEC controls the activation of each solenoid. If a thrust control malfunction event occurs, the FADEC recognizes the situation and activates the TCM solenoid 112. If an overspeed event is detected or the pilot commands shutdown the FADEC will activate the overspeed shutdown solenoid 114.
Referring to
Activating the TCM solenoid 112 connects Pf pressure to the backside of the valve 110 via the TCM feedback window 122 resulting in flow across the damping and pressure raising orifice 120. Flow through this orifice increases pressure on the spring side of the SOV 110. This pressure will cause the valve to translate towards the closed position. The intermediate position of the valve is based on the location of the TCM window 122 of the valve spool and metering edge in the valve sleeve. In this position, the SOV 110 provides a fixed restriction in series with the metering valve. By providing a fixed restriction in series with the metering valve, the effective area of the metering flow path is reduced and therefore flow to the burner is reduced. The first solenoid 112 is fluidly connected to a pressure port of the shut off a valve and to a feedback window of the shut off valve and then to the Damping and Pressure Raising Orifice 120. As the valve closes, it also closes the window 122 that connects Pf to the backside of the valve. This reduces the flow through the window 122 and through Damping and Pressure Raising Orifice 120 which in turn reduces the pressure 116 on the backside of the valve. As the valve closes, pressure continues to reduce until the valve eventually reaches an equilibrium point, where the area of the remaining open window 122 provides just enough pressure to hold the valve in the intermediate position. If the window 122 were to close further the pressure would drop and the valve would be out of pressure balance causing the valve to open again until pressure balance is again achieved.
Referring to
A method of thrust control malfunction and overspeed detection is also disclosed. While an electronic controller (FADEC) is monitoring the speed of the engine, if an overspeed of a predetermined speed setting is detected or if overspeed is sensed due to other failure (e.g., engine shaft shear detected by shaft speed sensors that detect speeds at opposite ends of the shaft), the controller (FADEC) will activate the overspeed solenoid 114. The controller (FADEC) will also sense a thrust control malfunction event, by taking into account at least one aircraft characteristic such as altitude/power setting/flight regime and make a decision to reduce the fuel flow to the engine rather than shut it down. If the thrust control malfunction criteria is satisfied, the controller (FADEC) will actuate a shutoff valve from an open position to a second position by energizing a TCM solenoid, thereby reducing the fuel flow to the engine burner and having the thrust of the aircraft be reduced. When the TCM solenoid is energized, TCM (thrust reduction) accommodation happens (flow reduction). When the O/S solenoid is energized, O/S accommodation happen (flow off). When both solenoids are energized, O/S accommodation occurs. In other words, O/S has priority over TCM.
The structure of the second solenoid, TCM feedback window 122 and the SOV metering window 124 defines a fixed, known position of SOV in a state such that flow to the engine burner is predetermined to be slightly above idle. The system has very high hydraulic spring rate which makes it such that no vibratory issues when closing
The methods and systems of the present disclosure, as described above and shown in the drawings, provide for fuel metering system with superior properties including increased reliability and reduced size, weight, complexity, and/or cost. While the apparatus and methods of the subject disclosure have been showing and described with reference to embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and score of the subject disclosure.
