Parker Aerospace variable bypass valve actuators control and vary the position of bypass air valves within the engine. The positions of the actuator is controlled directly by the control system and commanded by the full authority digital engine control (FADEC). During normal operation, the actuators are modulated according to the FADEC, based upon feedback from the actuator’s linear variable differential transformer (LVDT) signal.
Typically, there are two types of variable bypass valve actuators, master and slave. The master is the only one that contains an electro hydraulic servo valve (EHSV) and a LVDT, which position the actuator piston and provide electrical feedback to the FADEC.
Variable bypass valve actuators are fuel or oil operated. Fuel enters the EHSV cavity of the spool/sleeve through the “P” inlet port. Electrical signals sent to the dual coil servo from the FADEC cause the servo to modulate pressures Control 1 (C1) and Control 2 (C2). C1 and C2 are connected to the two chambers of the actuator piston. A pressure force difference between C1 and C2 causes the pistons to move (in the direction of higher to lower pressure force) and to travel to the desired position. When C1 pressure force equals C2 pressure force, the pistons remain in place due to a force balance and the piston position is held constant.
APPLICATIONS: Commercial aircraft engines
FEATURES AND ATTRIBUTES:
• Use of light weight, high strength 2618-T61 aluminum alloy bar for the piston cylinder/housing. This material has been proven to be light weight and high strength in numerous engine actuator applications.
• Piston made from high purity 15-5 PH grade stainless steel with tungsten-carbide plated (no chrome) shaft-seal surfaces to enhance reliability and service life.
• Sizing and geometry of internal fluid-flow passages have been optimized to minimize pressure losses, improving efficiency.
• High reliability, high performance Parker Jet-Pipe® EHSV, capable of superior low-temperature performance and chip shear force to ensure valve operation under all conditions.
• Sealing system proven to have low external leakage, minimal friction, and reduced contamination.
• LVDT adjustment feature which guarantees actuator-LVDT assembly and interface accuracy.
• Internally routed LVDT wiring prevents electromagnetic interference (EMI) and radio frequency interference (RFI) related issues. This design also provides superior wire management for vibration resistance and prevents damage during handling and installation.
At Parker Aerospace, our pneumatic subsystem expertise complements our fuel subsystem and fluid conveyance abilities in the engine environment. Available for virtually any specification or application, our cost-effective subsystems and components are well proven and reliable. Designed for extreme engine environments, our engine controls offer a wide range of seamlessly integrated and optimized selections using advanced designs, materials, and actuation technologies.
