Patent Application
20200232577
This disclosure relates to valve systems and more particularly starter valve systems for gas turbine engines.
A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air moves into the engine through the fan section. Airfoil arrays in the compressor section rotate to compress the air, which is then mixed with fuel and combusted in the combustor section. The products of combustion are expanded to rotatably drive airfoil arrays in the turbine section. Rotating the airfoil arrays in the turbine section drives rotation of the fan and compressor sections. The compressor section and turbine section each have multiple stages of blades that rotate about a central axis and multiple stages of vanes that are stationary relative to the central axis.
Some gas turbine engines, such as high efficiency gas turbine engines, may undergo a thermal stabilization or cooling cycle prior to engine operation. Gas turbine engines, may utilize an air turbine starter for a cooling cycle and subsequent spool up to ignition. This air turbine starter may also be utilized for normal engine starting cycles. A traditional shutoff valve used to control airflow to the air turbine starter for the cooling cycle and spool up may experience rapid wear, which may lead to frequent maintenance and/or replacement of the valve.
In one exemplary embodiment, a turbine engine system includes an engine starter coupled to a turbine engine. A starter valve assembly is configured to provide a flow of fluid to the engine starter. The starter valve assembly has a flow control valve movable via an actuator. A pneumatic control is in communication with the actuator. A torque motor servo-valve is in communication with the actuator.
In a further embodiment of any of the above, the torque motor servo-valve is configured to vary a position of the flow control valve to an infinite number of positions between an open position and a closed position.
In a further embodiment of any of the above, the position of the flow control valve is proportional to a current provided to the torque motor servo-valve.
In a further embodiment of any of the above, the flow control valve is a butterfly valve that has a disk rotatable about a shaft between an open position and a closed position.
In a further embodiment of any of the above, the flow control valve is configured to receive the flow of fluid that is bleed air from an auxiliary power unit.
In a further embodiment of any of the above, the flow control valve is configured to receive the flow of fluid that is bleed air from another engine.
In a further embodiment of any of the above, the torque motor servo-valve is configured to control the actuator in a motoring mode.
In a further embodiment of any of the above, the motoring mode permits the engine starter to operate at a lower speed.
In a further embodiment of any of the above, the pneumatic control is configured to provide over-torque protection to the engine starter.
In a further embodiment of any of the above, the pneumatic control is configured to control the flow control valve in a cross bleed start mode.
In a further embodiment of any of the above, a manual wrench feature is configured to permit an operator to manually control the actuator.
In a further embodiment of any of the above, the starter valve assembly does not contain a solenoid.
In another exemplary embodiment, a valve assembly for an engine includes a flow control valve that is configured to move between an open position and a closed position. An actuator is configured to actuate the valve between the open and closed positions. A pneumatic control is in communication with the actuator. A torque motor servo-valve is in communication with the actuator and is configured to vary a position of the flow control valve between the open and closed positions.
In a further embodiment of any of the above, the flow control valve is configured to meter a flow of fluid to an engine starter that is configured to operate in a motoring mode in response to a current provided to the torque motor servo-valve.
In a further embodiment of any of the above, the flow control valve is movable to an infinite number of positions between the open and closed positions.
In a further embodiment of any of the above, the pneumatic control is configured to provide over torque protection to the turbine.
In a further embodiment of any of the above, the actuator is a pneumatic half area actuator that has a spring and a diaphragm. The flow control valve is a butterfly valve.
In a further embodiment of any of the above, the valve assembly does not contain a solenoid.
In another exemplary embodiment, a method of operating a turbine engine includes providing an electrical signal to a torque motor servo valve that is in communication with a flow control valve. A flow of fluid is metered from an input to a turbine starter with the flow control valve. The turbine starter is operated in a motoring mode with the flow of fluid.
In a further embodiment of any of the above, the method provides a pneumatic control in communication with the flow control valve. The pneumatic control is configured to provide pressure regulation and prevent over torque.
The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings.
Various components of gas turbine engine 20 may heat or cool at different rates following operation and shutdown, leading to uneven thermal expansion. This uneven thermal expansion may physically deform engine components. For example, the thermal inequality may lead to bowed rotors, which can cause deflection of the rotor systems. Starting the engine 20 in this bowed condition can lead to tip strike of the rotor blades against nearby engine components, such as blade outer air seals (BOAS).
The system 100 includes a starter valve assembly 102. The starter valve assembly 102 described herein may help provide more uniform warm up and/or cooling of gas turbine engine components during start-up and/or shutdown and may reduce engine maintenance time of valves in the air turbine starter (ATS) 108. A starter valve assembly 102 may regulate airflow to the air turbine starter. Controlling the airflow to the air turbine starter 108 permits regulation of the engine speed to uniformly distribute engine temperature. This may help reduce the bowing of rotor systems in the engine 20, particularly during engine start-up and/or shutdown.
The system 100 may include a controller 104. The controller 104 may be a full authority digital engine control (FADEC), for example. The controller 104 may be in electrical communication with the valve assembly 102 and configured to control the valve assembly 102. The valve assembly 102 controls an output pressure of the airflow from the valve assembly 102.
The valve assembly 102 may be in communication with an input 106 of an engine component. In one example, the valve assembly 102 is in fluid communication with the input 106 and receives compressed air from the engine component. The input 106 may be bleed air pressure from an auxiliary power unit (APU) in one example. In this configuration, the engine 20 may be started via an APU ground start. For an APU ground start, an APU is started, then bleed air from the APU is directed to the turbine starter 108 via the starter valve 102 to start rotating a component of the engine 20. The input 106 may be bleed air from another engine in another example. In this configuration, the engine 20 may be started via a cross-bleed start. The input 106 may be connected to the valve assembly 102 via a bleed manifold. The valve assembly 102 may receive compressed air from the input 106 and deliver a controlled pressurized airflow to a turbine starter 108. In one example, the turbine starter 108 receives compressed air from the valve assembly 102, which drives a turbine wheel and gear shaft, which may be operatively coupled to the gas turbine engine 20. The turbine starter 108 starts rotating the gas turbine engine 20 during start-up. In one example, increased airflow to the turbine starter 108 results in increased rotational speed. Thus, the valve assembly 102 controls the rotational speed of the turbine starter 108 by controlling airflow to the turbine starter 108.
The system 100 may include a sensor 110 in communication with the controller 104. The sensor 110 may also be coupled to the gas turbine engine 20 and/or the turbine starter 108. The sensor may measure a speed of the gas turbine engine 20 and/or the turbine starter 108, for example. The sensor 110 may provide feedback to the controller 104, for example, which may generate a command based on the feedback received from the sensor 110.
The valve assembly 102 may further include a closed position switch 120 and a manual wrench 122. The closed position switch 120 and manual wrench 122 may also move the flow control valve 114 between the open and closed positions. The manual wrench 122 may permit an operator to manually open and close the valve 114, for example.
As shown in
The pneumatic control 117 provides over-torque protection for the turbine starter 108. The pneumatic control 117 generally includes a control spring 150 within a control cover 152, a control diaphragm 154, and a control nozzle 156 (shown in
The torque motor servo valve 118 may be an electromagnetic device that controls a flow of fluid proportional to an electrical signal that it receives, such as an amount of current. The fluid may be a pneumatic fluid, for example. The torque motor servo valve 118 generally includes a torque motor 160 and an armature 161 (shown in
When the system 100 is off, the torque motor 160 is not energized, and thus receives no current. In this state, the valve 114 is fully closed. When the valve is energized, the valve 114 is open or regulating. In one example, the torque motor 160 receives about 50 mA of current when the system 100 is on. In other examples, the torque motor 160 may modulate between 0 and 50 mA, as it relates to engine speed. In some embodiments, the torque motor may also have rated currents other than 50 mA, such as 100 mA or 150 mA, for example. When the system 100 is on, it has several modes, such as an APU Ground Start or APU Maintenance mode, an Engine Cross Bleed Start mode, and an Engine Motoring mode.
The APU Ground Start or APU Maintenance mode has the valve 114 in the fully open position. In this mode, the torque motor 160 is energized, and the outlet pressure Pvo is equal to the inlet pressure Pvi. The inlet pressure Pvi may be greater than about 10 psig, for example. The Engine Cross Bleed Start mode may have the valve 114 fully open or partially open. In this mode, the torque motor 160 is energized. When the valve 114 is fully open in the Engine Cross Bleed Start mode, the outlet pressure Pvo is equal to the inlet pressure Pvi. The inlet pressure Pvi may be greater than or equal to about 10 psig. When the valve 114 is partially open in the Engine Cross Bleed Start mode, the valve inlet pressure Pvi is greater than the valve outlet pressure Pvo.
When the valve is in the Engine Motoring Mode, the valve 114 is between the open and closed positions. The valve 114 is modulating a flow of fluid F. The Engine Motoring Mode permits a smaller amount of fluid to pass through the valve 114 than the fully open position, which permits the engine starter 108 to rotate at a slower speed than when the valve 114 is in the fully open position. In the Engine Motoring Mode, the torque motor 160 receives less than 50 mA, for example, and the valve inlet pressure Pvi may be greater than about 10 psig, for example. The pneumatic control 117 prevents over torque of the engine starter 108 and turbine of the engine 20, while the torque motor servo-valve 118 permits modulating the valve 114 in an engine motoring mode. The Engine Motoring Mode allows a turbine of the engine 20 to turn slower than during normal operation, which may be beneficial before or after a flight to permit the turbine to warm up or cool down to help prevent bowing.
Known starter valves utilize solenoids for control of the aircraft engine starter. The starter valve functions to control the pressure from the APU or engine into the air turbine starter. Often pulse-width modulation (PWM) signals are employed to control these solenoids for low speed engine motoring during bowed rotor starts. Some systems utilize PWM solenoids to provide low engine motoring during bowed rotor starts. However, PWM solenoids can be prone to reliability issues.
The above described system provides a torque motor servo valve on a starter valve that utilizes a pressure regulation feature for protection of the engine starter. When the disclosed valve is used for cross bleed starts using engine bleed pressures, a pressure regulation feature is required to limit the pressure into the starter to provide over-torque protection. The disclosed system uses a torque motor servo valve in place of the solenoid on a starter valve for both open and close operations and engine motoring control provides an efficient and reliable approach. This system is more reliable than previous systems.
The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.
