Variable-Orifice Pressure Relief Valve for Hydrogen Blowdown
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Solution Overview
Problem
Existing pressure relief valves for hydrogen storage tanks face challenges in controlling mass flow rate and flame size, leading to potential hazards due to fixed orifice designs that either allow dangerous accumulation or excessively large flames, and prolonged tank emptying times.
Innovation Solution
A pressure relief device with a piston mechanism that varies the outlet orifice size based on pressure differential, using a spring-biased piston within a cylinder to adjust the outlet orifice between end stops, allowing for dynamic control of fuel flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed orifice is used to control hydrogen flow rate, then flame size can be controlled, but tank blowdown time is prolonged
Solution Approach 1:
The patent applies a movable piston within a cylinder that can dynamically adjust the orifice area in response to changing tank pressure. As pressure decreases during blowdown, the piston moves to increase the orifice area, maintaining optimal mass flow rate and reducing total blowdown time while keeping flame size within safe limits.
Solution Approach 2:
The patent changes the physical parameter of orifice area from fixed to variable. By using a spring-loaded piston mechanism, the orifice area automatically adjusts as pressure changes, allowing the system to maintain optimal flow characteristics throughout the blowdown process rather than being constrained by a fixed orifice size.
2Productivity
If a fixed orifice is used to ensure sufficient hydrogen flow, then tank blowdown can occur, but flame may blow out and cause hazardous accumulation
Solution Approach 1:
The movable piston dynamically adjusts the orifice area to maintain optimal flow conditions throughout the blowdown process. This ensures sufficient hydrogen flow to prevent flame blowout while avoiding excessive flow that could create hazardous accumulation, adapting to changing pressure conditions in real-time.
Solution Approach 2:
The spring-loaded piston mechanism provides automatic feedback control where the pressure differential across the piston automatically adjusts the orifice area. As tank pressure decreases, the spring force adjusts the piston position to maintain appropriate flow rates, creating a self-regulating system that responds to changing conditions without external control.
3Loss of time
If a large orifice is used to enable rapid blowdown, then tank emptying time is reduced, but flame size becomes hazardously large
Solution Approach 1:
The piston mechanism dynamically adjusts the orifice area during the blowdown process. Initially, a smaller orifice area limits flame size to safe levels, then as pressure decreases, the orifice area increases to maintain flow rate and reduce blowdown time, optimizing both safety and efficiency throughout the process.
Solution Approach 2:
The patent changes the orifice area parameter from a constant large value to a variable value that adjusts with pressure. This allows the system to achieve rapid blowdown when needed while maintaining flame size within safe limits, avoiding the hazards associated with a permanently large orifice.
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
Enables rapid tank blowdown while maintaining controlled flame size and mass flow rate, reducing the risk of hazardous accumulation and minimizing tank emptying time.
Implementation Method 1
a spring mounted between the second end of the piston and the end wall of the cylinder, the spring arranged to bias the second end of the piston towards the second end stop
Implementation Method 2
movement of the piston along a longitudinal axis of the cylinder between the first and second end stops varies a size of the outlet orifice
Data Source
AI summary
A pressure relief device for a gaseous fuel including a cylinder having a fuel inlet in a wall, an outlet at an open first end and an end wall at a closed opposing second end; a piston disposed within the cylinder, the piston having a first end adjacent the outlet of the cylinder defining an outlet orifice and a second opposing end slidably mounted within the cylinder between first and second end stops; and a spring mounted between the second end of the piston and the end wall of the cylinder, the spring arranged to bias the second end of the piston towards the second end stop, wherein movement of the piston along a longitudinal axis of the cylinder between the first and second end stops varies the outlet orifice to vary a flow of gaseous fuel between the fuel inlet and the outlet orifice.