Axial Flow Expander Double-Flow Structure Thrust Cancellation
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Solution Overview
Problem
Conventional rotary machines used for expanding gases in large-scale liquefied gas plants face challenges with high pressure and flow rate, requiring multiple centrifugal expanders, which increase costs and maintenance, and existing axial flow turbines do not provide a suitable structure for removing inner components for maintenance without risking gas leaks.
Innovation Solution
An axial flow expander with a double-flow type structure, where the rotor shaft, stator vanes, and moving blades are integrated and inserted into a cylindrical casing, canceling thrust forces and eliminating the need for a division surface, thus preventing gas leaks and simplifying installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an axial flow rotary machine is adopted to increase flow rate, then productivity is improved, but thrust power occurs causing reliability deterioration
Solution Approach 1:
The patent applies the counterweight principle by designing a double-flow type structure where gas flows in opposite directions through two separate passages. This creates equal and opposite thrust forces that cancel each other out, eliminating the net thrust power problem while maintaining high flow rate capability. The first and second moving blades are positioned to receive gas flow from opposite directions, generating counterbalancing forces.
2Ease of repair
If the casing is divided into two parts for component removal, then ease of repair is improved, but gas leaks occur due to high pressure causing reliability deterioration
Solution Approach 1:
The patent applies segmentation by dividing the casing into a first casing and a second casing along the axial direction, with the rotor shaft and blades positioned between them. This segmentation allows the rotor shaft to be removed from the end of the first casing without requiring separation at high-pressure interfaces, enabling easy maintenance while preventing gas leaks through proper sealing design.
3Productivity
If multiple centrifugal expanders are used to handle large flow rate, then productivity is improved, but device complexity and installation space increase
Solution Approach 1:
The patent merges multiple expansion functions into a single axial flow expander by incorporating two sets of moving blades (first and second moving blades) within one unit. This allows the device to handle large flow rates that would otherwise require multiple centrifugal expanders, reducing overall system complexity and installation space while maintaining high productivity.
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 axial flow expander effectively increases flow rate and withstands high pressure while reducing component count, eliminating gas leaks and simplifying installation by integrating key components within the casing, allowing for stable operation and reduced maintenance complexity.
Implementation Method 1
the gas is flowed inside the gas passage in both directions along an axis of the expander, it is possible to cancel force in a thrust direction acting on the rotor shaft
Implementation Method 2
an axial flow expander for expanding gas flowed in a direction along an axis
Data Source
AI summary
The axial flow expander includes: an outer casing provided with a suction port and a discharge port through which gas is discharged from the outer casing; an inner casing inside which a gas passage is formed and which is provided with a first communication portion which communicates the gas passage with the suction port and a second communication portion which communicates the gas passage with the discharge port; a rotor shaft which extends in the direction along an axis; a bearing configured to bear the rotor shaft; stator vanes which protrudes inward from an inner periphery of the inner casing; and moving blades which protrudes outward from the rotor shaft. The inner casing, the rotor shaft, the bearing, the stator vanes, and the moving blades are integrally assembled, and the assembled members are inserted into the outer casing.