Shape Memory Preload Relief Valve for High-Temperature Pressure Stability
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Solution Overview
Problem
Pressure relief valves (PRVs) used in high-temperature pneumatic applications, such as aircraft engines and nacelles, face challenges in maintaining consistent performance across a wide range of temperatures due to the degradation of biasing forces provided by materials like springs.
Innovation Solution
Incorporating a variable preload means utilizing shape memory materials, which apply a higher preload to the biasing means when the temperature exceeds a transition temperature, thereby compensating for the degradation in biasing force and maintaining consistent cracking pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple mechanical PRV is used, then the device complexity is reduced and weight is decreased, but the performance consistency across wide temperature ranges deteriorates due to biasing force degradation
Solution Approach 1:
The shape memory alloy washer changes its physical state from austenite to martensite at the transition temperature (190°C), causing a dimensional change that adjusts the spring preload. This parameter change allows the PRV to compensate for spring stiffness degradation and maintain consistent cracking pressure across wide temperature ranges without increasing structural complexity
Solution Approach 2:
The invention converts the harmful effect of spring stiffness degradation at high temperatures into a beneficial self-compensation mechanism. The shape memory alloy washer utilizes the temperature change that causes spring degradation to automatically adjust the preload, turning the temperature-induced problem into a self-correcting feature that maintains performance consistency
2Reliability
If an electronically actuated PRV is used to maintain consistent performance across wide temperature ranges, then performance consistency is improved, but the device complexity and weight increase due to additional sensors, control and wiring
Solution Approach 1:
The shape memory alloy washer performs the temperature compensation function autonomously without requiring external control systems. The material automatically senses temperature changes and adjusts the spring preload accordingly, eliminating the need for electronic sensors, controllers, and wiring while maintaining performance consistency across wide temperature ranges
Solution Approach 2:
The invention replaces complex electronic control systems with a passive mechanical solution using shape memory alloy. The smart material provides automatic temperature compensation through its inherent phase transformation properties, substituting electronic actuators and control circuitry with a simple mechanical component that maintains cracking pressure consistency
3Reliability
If a shape memory material is used to provide thermal compensation, then performance consistency across temperature ranges is improved, but the device complexity increases due to the variable preload means
Solution Approach 1:
The shape memory alloy washer serves multiple functions simultaneously: it acts as both a preload adjustment mechanism and a temperature sensing element. This multi-functionality allows the single component to compensate for spring degradation across wide temperature ranges without requiring separate sensing and actuation systems, thereby minimizing the increase in device complexity
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 enables a simple and lightweight PRV to maintain consistent performance across a wide range of operating temperatures, reducing pressure decay and maintaining regulatory pressure effectiveness.
Implementation Method 1
a variable preload means, the variable preload means configured to apply a preload to the biasing means so as to increase the biasing force, wherein the variable preload means comprises a shape memory material such that, above a transition temperature of the shape memory material, the variable preload means changes shape so as to apply a higher preload to the biasing means
Data Source
Figure 1A
Figure 1B~1C
Figure 2A
AI summary
There is provided a pressure relief valve, PRV, comprising an inlet (210) and an outlet (220) defining a fluid flow path therebetween. The PRV comprises a plunger (202), the plunger being moveable between a closed position and an open position, wherein, in the closed position, the plunger blocks the fluid flow path, and, in the open position, fluid may flow through the fluid flow path, wherein pressure at the inlet applies an opening force on the plunger, urging the plunger towards the open position. The PRV also comprises a biasing means (205) configured to apply a biasing force to the plunger, thereby biasing the plunger towards the closed position such that, when the biasing force is greater than the opening force, the plunger remains in the closed position, and when the opening force is greater than the biasing force and the plunger moves to the open position. The PRV also comprises a variable preload means (208), the variable preload means configured to apply a preload to the biasing means so as to increase the biasing force; wherein the variable preload means comprises a shape memory material such that, above a transition temperature of the shape memory material, the variable preload means changes shape so as to apply a higher preload to the biasing means.