Multi-Lobe Pressure Vessel Assembly for Compact CNG Storage
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Solution Overview
Problem
Conventional CNG storage tanks are large and bulky due to low gas volumetric density, making them inefficient for use in automotive vehicles, where space is a concern.
Innovation Solution
A pressure vessel assembly comprising a plurality of lobes with vertically arranged interior walls, joined by end caps and bonded using various welding techniques, optimized for high conformability and stress distribution, allowing efficient storage of compressed natural gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional CNG storage tanks are designed to store enough natural gas for comparable driving range, then the storage capacity is sufficient, but the tank becomes large and bulky, occupying excessive cargo space
Solution Approach 1:
The pressure vessel is divided into multiple lobes (typically 5-7 lobes) arranged in a circular pattern around a central axis. Each lobe acts as an independent pressure-containing chamber, allowing the total gas storage capacity to be distributed across multiple smaller units rather than one large tank, thereby reducing the overall volume footprint while maintaining required storage capacity.
Solution Approach 2:
The multi-lobe design enables nested arrangement where lobes are positioned concentrically around a central axis, with end caps closing the assembly. This nested configuration maximizes space utilization by arranging pressure-containing volumes in a compact circular pattern, significantly reducing the external dimensions compared to conventional cylindrical tanks of equivalent capacity.
2Volume of moving object
If the pressure vessel uses multiple lobes joined by end caps, then the conformability and space efficiency improve, but the manufacturing complexity and joining requirements increase
Solution Approach 1:
The pressure vessel is divided into multiple lobes (typically 5-7 lobes) arranged in a circular pattern around a central axis. Each lobe acts as an independent pressure-containing chamber, allowing the total gas storage capacity to be distributed across multiple smaller units rather than one large tank, thereby reducing the overall volume footprint while maintaining required storage capacity.
Solution Approach 2:
Multiple lobes are joined together through common end caps that seal the circular arrangement. This merging of multiple pressure-containing elements into a unified assembly through shared end caps simplifies the overall structure compared to having completely separate tanks, while still achieving the space-efficient multi-lobe configuration.
3Strength
If adjacent chamber walls of lobes are joined together, then the structural integrity and stress distribution improve, but the material strength loss at joint locations increases
Solution Approach 1:
The lobes are designed with curved, spherical-like geometries rather than sharp corners or flat surfaces. This curvature distributes stress more evenly across the lobe surfaces and joint regions, reducing stress concentration at connection points. The rounded contours of the lobes and their joining interfaces minimize stress risers that would otherwise lead to material strength degradation at joint locations.
Solution Approach 2:
The end caps and joint regions are designed with locally optimized geometries and material properties. The joining areas feature enhanced curvature and thickness variations that locally improve stress distribution without affecting the overall lobe structure. This localized quality enhancement at critical joint regions maintains structural integrity while minimizing material strength loss at these specific locations.
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
The design achieves higher conformability and reduced material strength loss, enabling the pressure vessel to be more compact and robust, fitting within smaller spaces such as vehicles while maintaining long-term fatigue resistance.
Implementation Method 1
bonded using various welding techniques
Implementation Method 2
friction stir welding
Implementation Method 3
friction stir welding
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A pressure vessel assembly includes a plurality of lobes, each lobe having at least one vertically arranged interior wall, the lobes positioned in a side by side arrangement such that a first interior wall of a first lobe is positioned adjacent a second interior wall of a second lobe, the first interior wall having a first wall top and bottom side, the second interior wall having a second wall top and bottom side, the first wall top side joined to the second wall top side and the first wall bottom side joined to the second wall bottom side. Also included are first and second end wall surfaces of each of the plurality of lobes. Further included is a plurality of end caps, each of the end caps joined to the end wall surfaces of the lobes, each of the end caps joined to at least one adjacent end cap.