Rotating-Frame Pitch Control Without Oil Transfer Bearings
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Solution Overview
Problem
Existing turbine engine pitch change mechanisms face issues with hydraulic fluid transfer from a fixed to a rotating reference frame, leading to complex and fragile OTBs, oil leaks, reliability concerns, and operational limitations, particularly at low rpm, requiring additional pumps and protection systems.
Innovation Solution
An electrohydraulic actuator system with a jack, hydraulic pump, and tanks in a rotating frame, along with valves and accumulators, eliminates the need for OTBs by controlling fluid transfer independently of the engine's operation and lubrication group, ensuring reliable pitch changes and feathering without electrical dependencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an OTB (Oil Transfer Bearing) is used to transfer hydraulic fluid from a fixed reference frame to a rotating reference frame, then pitch control is enabled, but the system becomes complex and fragile with significant oil leaks
Solution Approach 1:
The patent extracts the hydraulic pump from the rotating reference frame and places it in the fixed reference frame, eliminating the need for an OTB. The pump is now stationary and supplies hydraulic fluid to the rotating jack through a different mechanism that does not require rotational fluid transfer, thereby removing the complex and fragile OTB component while maintaining pitch control functionality.
Solution Approach 2:
The patent introduces a hydraulic accumulator as an intermediary element that stores hydraulic fluid in the fixed reference frame. This accumulator acts as a buffer, allowing the stationary pump to supply fluid that is then transferred to the rotating jack through a mechanism that avoids direct rotational fluid transfer, thus eliminating the OTB while maintaining system functionality.
2Power
If a hydraulic pump driven by turbine engine shafts is used to provide high power density, then power density is improved, but operating limitations occur at low rpm and during engine shutdown
Solution Approach 1:
The patent uses a hydraulic accumulator that is pre-charged with hydraulic fluid under pressure. This preliminary storage of hydraulic energy allows the system to operate independently of the turbine engine's rotational speed, providing the necessary hydraulic power for pitch control even at low rpm or during engine shutdown when the engine-driven pump cannot operate effectively.
Solution Approach 2:
The hydraulic accumulator serves as a self-contained energy storage device that does not require continuous operation of the engine-driven pump. It autonomously provides the necessary hydraulic pressure and flow to the pitch control jack, making the system self-sufficient during engine startup, shutdown, or low-speed operations without relying on the rotational speed of the turbine engine.
3Reliability
If additional independent pumps and pitchlock systems are installed to ensure pitch control at low rpm and during shutdown, then operational reliability is improved, but system complexity and weight increase
Solution Approach 1:
The hydraulic accumulator serves multiple functions: it stores hydraulic energy, provides pressure during engine shutdown, enables pitch control at low rpm, and acts as a backup power source. This single multi-functional component replaces the need for separate independent pumps, pitchlock systems, and other auxiliary devices, thereby improving operational reliability while reducing overall system complexity and weight.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enhances reliability and performance by reducing oil leaks and oversizing, operates across various engine conditions, and provides fail-safe feathering, independent of hydraulic fluid pressure, thus simplifying the engine design and reducing complexity.
Implementation Method 1
a hydraulic pump adapted to selectively supply the first chamber or the second chamber of the jack with pressurized hydraulic fluid
Implementation Method 2
a valve controlled between a first position, in which the valve puts the first chamber of the jack in fluid communication with the hydraulic pump, and a second position in which the valve puts the first chamber of the jack in fluid communication with the hydraulic fluid tank
Data Source
AI summary
The present invention relates to a pitch-change mechanism for a turbine engine propeller, said turbine engine comprising a stator portion and a rotor portion, said pitch-change mechanism comprising an electrohydraulic actuator comprising: —a cylinder for actuating the propeller, comprising a first chamber and a second chamber; —a hydraulic pump suitable for selectively supplying the first chamber or the second chamber of the cylinder with pressurized hydraulic fluid; —a hydraulic fluid reservoir configured to store a pressurized hydraulic fluid; —a valve controlled between a first position in which the valve places the first chamber of the cylinder in fluid communication with the hydraulic pump, and a second position in which the valve places the first chamber of the cylinder in fluid communication with the hydraulic fluid reservoir.