Axial Flow Expander Modular Assembly for High-Pressure LNG Cooling
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Solution Overview
Problem
Current centrifugal expanders have limited efficiency and require multiple units for large-scale liquefied natural gas (LNG) production, leading to increased costs and complexity, while existing axial flow expanders lack a structure for easy maintenance and sealing in high-pressure applications.
Innovation Solution
An axial flow expander design with a unified outer casing and inner casing, featuring a rotor shaft, bearings, stator vanes, and moving blades, allowing for higher flow rates and pressure drops, and enabling easy assembly and maintenance without leakage, by using a double-flow structure to cancel thrust forces and allowing equipment attachment on both sides of the shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If centrifugal expanders are used for gas expansion, then the device can be manufactured with conventional design, but the efficiency is limited and multiple units are required for large-scale LNG production
Solution Approach 1:
The patent changes the fundamental flow parameters by transitioning from radial flow (centrifugal) to axial flow configuration. This parameter change enables single-unit handling of large gas volumes previously requiring multiple centrifugal units, while maintaining manufacturability through standardized axial turbine design practices
Solution Approach 2:
The patent transitions from two-dimensional radial flow patterns to three-dimensional axial flow patterns through the turbine stages. This dimensional change in flow configuration enables higher throughput capacity in a single unit while preserving conventional manufacturing approaches for axial turbines
2Productivity
If multiple centrifugal expanders are used to increase flow rate, then the productivity increases, but the device complexity and cost increase
Solution Approach 1:
The patent merges multiple expansion functions into a single axial flow expander unit with multiple stages. The multiple turbine stages process different refrigerant streams (CH4, C2H6, C3H8) sequentially, combining what would have required separate centrifugal units into one integrated axial flow device, thereby reducing overall system complexity
3Productivity
If axial flow expander is used for high flow rate, then the productivity increases, but the sealing in high-pressure applications becomes difficult
Solution Approach 1:
The patent segments the high-pressure environment into isolated zones using a segmented casing design. The casing is divided into separate sections that can be independently sealed, with each segment handling specific pressure zones. This segmentation allows effective sealing in high-pressure applications while maintaining the high flow capacity of axial flow configuration
4Stress or pressure
If axial flow expander is used for high-pressure application, then the pressure drop capability increases, but the maintenance accessibility becomes difficult
Solution Approach 1:
The patent divides the expander into modular segments including separate casing sections, rotor assemblies, and turbine stages. This segmentation allows individual components to be accessed, removed, and serviced independently while the unit remains installed, maintaining high-pressure operational capability during maintenance activities
Solution Approach 2:
The patent employs a dynamic maintenance approach where the casing can be opened and components can be accessed while the system is in operational or semi-operational states. The modular design allows for hot-swapping or quick-change components, enabling maintenance without complete system shutdown and preserving pressure differential capabilities
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 achieves higher efficiency and reduced equipment count, enabling more effective cooling and energy extraction for LNG production, while maintaining high-pressure sealing and facilitating maintenance.
Implementation Method 1
an axial flow expander for expanding gas flowed in a direction along an axis thereof
Implementation Method 2
removing energy from the fluid stream in an isentropic manner
Implementation Method 3
a plurality of bearings fixed to the inner casing, wherein the plurality of bearings is configured to allow the rotor shaft to rotate around the axis with respect to the inner casing
Implementation Method 4
a plurality of stator vanes fixed to the inner casing so as to protrude inward from an inner surface of the inner casing, wherein the plurality of stator vanes is arranged inside the gas passage so as to be separated at intervals in the direction of the axis. A plurality of moving blades is fixed to the rotor shaft so as to protrude outward from the rotor shaft, and arranged inside the gas passage so as to be alternating with the plurality of stator vanes
Data Source
AI summary
An exemplary embodiment of the present techniques provides a system for decreasing a temperature of a fluid. The system includes an axial flow expander for expanding gas flowed in a direction along an axis thereof. The axial flow expander includes: an outer casing made as a unified structure having an inlet port and an outlet port. An inner casing is fixed inside the outer casing. A rotor shaft is accommodated inside the inner casing, and is aligned with the axis. A number of bearings allow the rotor shaft to rotate around the axis. Moving blades protrude from the rotor shaft and are arranged inside the gas passage in an alternating fashion with a number of stator vanes. The inner casing, the rotor shaft, the bearings, the stator vanes, and the moving blades are integrally assembled, and inserted into the outer casing in the direction along the axis.