Propeller Blade Angle Oil Circuit for Overheating Control
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Solution Overview
Problem
Turboprop gas turbine engines face inefficiencies due to excess hydraulic fluid being diverted back to the pump during steady-state operations, leading to increased oil temperature and potential damage, as the pump is sized for peak loads rather than steady-state requirements.
Innovation Solution
The oil system incorporates a flow regulator with a pressure regulator valve that operates in closed position during transient operations and open position during steady-state, diverting excess oil to the engine oil return system for cooling, thereby reducing the risk of overheating and optimizing hydraulic power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pump is sized to meet the largest load requirements of the blade angle control system, then the hydraulic fluid flow requirements for peak loads are satisfied, but the pump supplies more fluid than required during steady-state operation, causing excess fluid to be diverted back to the pump inlet and increasing oil temperature
Solution Approach 1:
The patent applies a dynamic flow regulator valve that automatically adjusts its opening degree based on real-time system conditions. During transient operations, the valve opens fully to allow maximum fluid flow for rapid blade angle changes. During steady-state operations, the valve partially closes to restrict excess fluid flow back to the pump inlet, thereby reducing oil temperature rise while maintaining sufficient flow for control operations.
Solution Approach 2:
The flow regulator valve changes the flow resistance parameter dynamically based on operational phase. By adjusting the valve opening degree, the system modifies the flow characteristics to match demand: high flow during transient operations and restricted flow during steady-state operations, preventing excessive temperature increase in the oil.
2Temperature
If a flow regulator is added to restrict excess fluid flow during steady-state operation, then oil temperature increase is reduced, but the device complexity increases
Solution Approach 1:
The flow regulator valve is designed as a self-regulating device that automatically adjusts its opening degree based on system pressure and flow conditions without requiring external control signals or complex electronics. The valve uses inherent pressure differential and spring forces to modulate flow, eliminating the need for additional sensors, actuators, or control systems, thereby minimizing added complexity.
3Power
If the flow regulator operates in closed position during transient operation, then hydraulic power availability is optimized for rapid blade angle changes, but the system cannot dissipate excess heat during high-load operations
Solution Approach 1:
The flow regulator valve operates in periodic cycles, switching between fully open position during transient operations to maximize power delivery and partially closed position during steady-state operations to dissipate heat. This periodic adjustment of flow restriction aligns with the operational demands of the propeller control system, providing maximum power when needed and thermal management when demand is lower.
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
This solution effectively manages oil flow to prevent overheating and ensures consistent hydraulic power availability for propeller blade angle control, enhancing engine performance and reducing the risk of damage from excessive temperatures.
Implementation Method 1
The blade angle control system is actuated by hydraulic fluid which is supplied under pressure by a pump
Implementation Method 2
controlling access of the hydraulic fluid to a leakage path leading to an engine oil return system
Implementation Method 3
The pressure regulator valve has a spool disposed within the housing and displaceable relative to the housing to block and expose the inlet aperture
Data Source
Figure 1
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Figure 3
AI summary
A control circuit (20) for changing the angle of propeller blades (17) includes a propeller control unit (21) controlling a supply of oil to modify an angle of propeller blades (17), and a fixed-displacement pump (22) providing the supply of oil from an engine oil return system (13) to the propeller control unit (21). An oil cooling line (23) extends between an outlet (22B) of the pump (22) and the engine oil return system (13). The oil cooling line (23) defines an oil leakage path (27) leading to the engine oil return system (13) for cooling the oil. A flow regulator (30) between the pump (22) and the propeller control unit (21) is operable between an open position where oil is directed through the oil cooling line (23) to the engine oil return system (13) for cooling the oil, and a closed position blocking the oil cooling line (23) and directing oil toward the propeller control unit (21) to modify the angle of the propeller blades (17).