Closed-Cycle Heat Engine Fluid Bearings Without Oil Lubrication
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Solution Overview
Problem
Heat engines with oil-lubricated bearing assemblies require additional components and generate unwanted heat due to fluid shear, increasing costs and complexity, while existing solutions do not effectively utilize the working fluid for both energy production and lubrication.
Innovation Solution
A hermetically sealed heat engine design that uses the working fluid as both a sealing and lubricating medium, eliminating the need for oil-lubricated bearings by incorporating a fluid bearing assembly and sealing system, which supports the rotating drivetrain and is configured to utilize supercritical fluids like carbon dioxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oil-lubricated bearing assemblies are used, then the rotating drivetrain is supported, but additional pumps and sumps are required which increase cost and weight
Solution Approach 1:
The patent combines the lubrication function with the working fluid system by using the same fluid (supercritical CO2) for both energy conversion and bearing lubrication. This eliminates separate lubrication system components (pumps, sumps, oil reservoirs) and integrates the bearing support function into the existing closed-loop working fluid system.
Solution Approach 2:
The working fluid (supercritical CO2) performs multiple functions: it serves as the energy carrier in the heat engine cycle and simultaneously as the lubricating medium for the bearing assembly. This multi-functionality reduces the number of separate systems needed and simplifies the overall device architecture.
2Reliability
If oil-lubricated bearing assemblies are used, then the rotating drivetrain is supported, but undesired heat is generated at the oil-film clearance due to fluid shear
Solution Approach 1:
The patent changes the physical state and properties of the lubricating medium by using supercritical CO2 instead of conventional oil. The supercritical fluid has different viscosity and shear characteristics that reduce energy loss through fluid shear while still providing adequate bearing support. The parameter change from liquid oil to supercritical fluid fundamentally alters the lubrication mechanism.
3Device complexity
If the working fluid is used for both energy production and lubrication, then system complexity is reduced, but hermetic sealing is required to maintain working fluid integrity
Solution Approach 1:
The patent extracts the bearing assembly from the hermetically sealed working fluid system by placing it in a separate, accessible location. The bearing is positioned outside the main sealed chamber, allowing it to be serviced or replaced without compromising the integrity of the working fluid containment. This spatial separation resolves the conflict between simplicity and sealing requirements.
4Loss of energy
If dry gas seals are eliminated, then parasitic losses are reduced, but the working fluid must directly contact the bearing surfaces
Solution Approach 1:
The patent uses the properties of supercritical CO2 fluid dynamics to provide lubrication through controlled fluid flow and pressure distribution in the bearing clearance. The pneumatic/hydraulic action of the supercritical fluid creates a lubricating film that reduces friction and parasitic losses while the fluid's properties prevent contamination of moving surfaces.
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 design simplifies the system, reduces costs, and enhances efficiency by eliminating the need for dry gas seals and associated parasitic losses, while maintaining the integrity of the working fluid within the closed flowpath.
Implementation Method 1
The fluid bearing assembly is configured to utilize the working fluid to support the rotating drivetrain
Implementation Method 2
The heat exchanger is thermally coupled to the closed flowpath for adding heat to the working fluid
Data Source
AI summary
Heat engines employing fluid bearing assemblies hermetically sealed with a closed flowpath for a working fluid are generally disclosed. For example, the heat engine includes a rotating drivetrain and a fluid bearing assembly. The rotating drivetrain includes a compressor section, an expander section, and a heat exchanger. The compressor section and expander section together define at least in part a closed flowpath for the flow of a working fluid. The heat exchanger is thermally coupled to the closed flowpath for adding heat to the working fluid. The fluid bearing assembly is configured to utilize the working fluid to support the rotating drivetrain. Further, the fluid bearing assembly is hermetically sealed with the closed flowpath.