Estimating Gas Tank Pressure via Flow Rate Modulation
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Solution Overview
Problem
Existing gas supply systems face challenges in accurately detecting the internal pressure of gas tanks, especially when the remaining capacity is low, due to the trade-off between detection range and sensitivity, leading to inaccuracies in pressure estimation.
Innovation Solution
A gas supply system with an unbalanced pressure reducing valve and a pressure sensor configuration that changes the outlet-side flow rate to estimate the inlet-side pressure using the difference between detection values at different flow rates, improving accuracy by referencing a pre-stored map of pressure and flow rate relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pressure sensor with a wide detection range is used to detect pressure from full capacity to very small remaining capacity, then the detection range is improved, but the detection sensitivity decreases and the variation from true value increases
Solution Approach 1:
The detection process is segmented into multiple stages based on tank pressure levels. When pressure is high (full capacity), the system uses one detection approach, and when pressure is low (depleted capacity), it switches to another approach. This segmentation allows each stage to use optimized parameters for its specific range, resolving the contradiction between wide range and high sensitivity.
Solution Approach 2:
The system dynamically adjusts the detection method based on the current tank pressure level. By monitoring the pressure state and switching between different detection strategies (direct detection vs. estimation through flow rate and outlet pressure), the system maintains high measurement precision across the entire detection range, rather than using a fixed sensor configuration.
2Measurement precision
If the outlet-side flow rate of the pressure reducing valve is changed to estimate inlet-side pressure using pressure differences, then the accuracy of pressure estimation is improved, but the system complexity increases
Solution Approach 1:
The system uses the pressure reducing valve and outlet pressure sensor as intermediary components to indirectly measure inlet pressure. Instead of placing a sensor directly in the high-pressure inlet line, it uses the valve's pressure reduction function and measures the lower-pressure outlet side, inferring inlet conditions through the known valve characteristics and flow rate relationships.
Solution Approach 2:
The system changes the flow rate parameter of the pressure reducing valve to create measurable pressure differences that reveal inlet pressure information. By varying the flow rate and observing corresponding outlet pressure changes, the system can estimate inlet pressure with high accuracy using the relationship between flow rate, outlet pressure, and inlet pressure.
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 configuration enhances the accuracy of internal pressure estimation in gas tanks, even at low remaining capacities, by leveraging the sensitivity of pressure changes with flow rate variations, thereby improving the detection precision and extending the usable hydrogen supply in fuel cell systems.
Implementation Method 1
an unbalanced pressure reducing valve in which an outlet-side pressure changes with an increase in inlet-side pressure and which is disposed in the gas supply path and reduces a pressure of the gas supplied from the gas tank
Data Source
AI summary
A gas supply system includes: a gas tank; an unbalanced pressure reducing valve that reduces a pressure of the gas supplied from the gas tank; a pressure sensor that detects an outlet-side pressure of the pressure reducing valve; a flow rate changing unit that changes an outlet-side flow rate of the pressure reducing valve; and a control unit. The control unit changes the outlet-side flow rate between first and second flow rates, obtains a first pressure, which is a detection value of the pressure sensor when the outlet-side flow rate is the first flow rate, and a second pressure, which is a detection value of the pressure sensor when the outlet-side flow rate is the second flow rate, and estimates an inlet-side pressure of the pressure reducing valve using the relationship among the first flow rate, the second flow rate, and the difference between the first and second pressures.