Bleed Valve Pneumatic Control for Reliable Closure
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Solution Overview
Problem
Conventional bleed valves in gas turbine engines face challenges in reliably closing due to solenoid failure during engine start-up, particularly in managing the spring constant and preload to accurately respond to increasing operating pressures, which can lead to instability issues due to friction and piston hysteresis.
Innovation Solution
An intermediate pneumatic valve is introduced to control the air pressure within the bleed valve's chamber, allowing the bleed valve to switch positions based on engine operating pressure thresholds, rather than relying solely on the spring or solenoid, thereby reducing the impact of friction and hysteresis and enabling a more reliable closure mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bleed valve uses a spring to bias the piston towards an open position and relies on solenoid actuation to close, then the valve can be operated during start-up, but the valve fails to reliably close upon solenoid failure due to friction and piston hysteresis
Solution Approach 1:
A second pneumatic valve is introduced as an intermediary component between the solenoid actuation system and the bleed valve piston. This intermediate valve receives pressurised air from a second source and controls its delivery to the piston chamber, providing an additional control layer that ensures reliable valve closure even when the solenoid fails, while managing friction and hysteresis effects through pneumatic pressure control
2Force
If the spring constant is increased to ensure valve closure against friction and hysteresis, then the valve can overcome resistive forces, but the valve becomes unstable and difficult to control at varying engine pressures
Solution Approach 1:
The system uses pneumatic pressure from a second source, controlled by a second pneumatic valve, to act on the piston in addition to or instead of relying solely on spring force. This pneumatic control mechanism provides stable, adjustable force that responds to engine pressure conditions, eliminating the need for high spring constants and associated instability while ensuring reliable valve closure
Solution Approach 2:
The system changes the control parameter from fixed spring constant to variable pneumatic pressure. By controlling the pressure of the second air source through the second pneumatic valve, the force applied to the piston can be dynamically adjusted to match engine operating conditions, providing stable operation across varying pressures without the instability caused by high spring constants
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 ensures a more accurate and reliable closure of the bleed valve upon solenoid failure, allowing the spring constant to be set at a lower value, reducing instability and ensuring consistent operation across varying engine pressures.
Implementation Method 1
a spring configured to bias a piston towards an open position
Implementation Method 2
A solenoid forms part of a pneumatic switch that can be switched from a first position to a second position
Implementation Method 3
relatively high pressure air will be supplied to the chamber, which increases the air pressure on the piston, and also the force acting against the action of the spring
Data Source
Figure 1~2
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AI summary
An apparatus (200) for use in a gas turbine engine is disclosed comprising a bleed valve (10) and an intermediate valve (200). In use the bleed valve (10) is exposed to a source of pressurised air, and the bleed valve (10) is movable between an open position, in which the bleed valve (10) permits a flow of the pressurised air through the bleed valve (10) and a closed position, in which the bleed valve (10) does not permit a flow of the pressurised air through the bleed valve (10). The intermediate valve (200) is operatively connected to the bleed valve (10) and configured to selectively open and close the bleed valve (10), wherein the intermediate valve (200) is configured in a mode of operation to close the bleed valve (10) based on the pressurised air within the bleed valve (10) exceeding a predetermined threshold.