Stirling Engine Piston Assembly for Low Temperature Difference
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Solution Overview
Problem
Stirling Cycle heat engines face challenges in achieving maximum output when using heat sources with smaller temperature differences, as they require a larger gas flow through the regenerator to compensate for the smaller pressure rise, which is not efficiently managed by existing designs.
Innovation Solution
The design incorporates a heat engine with a high-temperature space and a low-temperature space separated by a regenerator, featuring two pistons that move with a 180° phase difference and are connected by a connecting rod, allowing for increased gas flow through the regenerator and efficient pressure change, while minimizing mechanical loss and optimizing crankshaft radius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If gas flow through the regenerator is increased to compensate for smaller pressure rise in low temperature difference applications, then output is improved, but device complexity increases
Solution Approach 1:
The patent combines the displacer and power transmission functions into a single integrated piston structure. The first piston serves both as a displacer to transfer working gas and as a power transmission element, eliminating the need for separate displacer and power piston components. This merging reduces device complexity while maintaining the required gas flow through the regenerator for low temperature difference applications.
Solution Approach 2:
The first piston is designed with multi-functionality, serving as both a displacer for gas transfer and a power transmission element. The piston's movement with a phase difference smaller than 180° allows it to perform both functions simultaneously, reducing the number of components needed while achieving the necessary gas flow rates for improved output in low temperature difference applications.
2Power
If phase difference between pistons is reduced from 180° to optimize pressure change, then power transmission efficiency is improved, but gas transfer effectiveness deteriorates
Solution Approach 1:
The patent employs dynamic phase difference control where the first piston moves with a phase difference smaller than 180° relative to the second and third pistons. This dynamic adjustment optimizes the balance between pressure change for power transmission and gas transfer effectiveness, allowing the system to adapt to different operating conditions and maintain both power efficiency and productivity.
Solution Approach 2:
The patent changes the operational parameter of phase difference from the conventional 180° to a smaller value. This parameter change optimizes the pressure change characteristics for better power transmission efficiency while the integrated piston design compensates for any potential reduction in gas transfer effectiveness, achieving overall system optimization.
3Loss of energy
If crankshaft radius is reduced to minimize mechanical loss, then efficiency is improved, but torque generation capacity deteriorates
Solution Approach 1:
The patent applies preliminary action by optimizing the piston phase difference before the working gas expands. The first piston is positioned and phased to maximize pressure change during the expansion stroke, ensuring that maximum force is available early in the power stroke. This allows for a smaller crankshaft radius to be used while maintaining sufficient torque generation capacity throughout the cycle.
Solution Approach 2:
The patent changes the phase difference parameter to optimize the timing and magnitude of pressure changes, which compensates for the reduced torque leverage from a smaller crankshaft radius. By adjusting the phase relationship between pistons, the system maintains effective torque generation while minimizing mechanical loss through the smaller crankshaft dimensions.
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 enables sufficient pressure change and efficient energy transfer, optimizing output for heat sources with smaller temperature differences, reducing mechanical loss, and allowing for compact, high-speed operation suitable for low-temperature-difference applications like geothermal heat and industrial waste heat utilization.
Implementation Method 1
a regenerator provided between the high-temperature space portion and the low-temperature space portion... heat and motive energy are exchanged by using volumetric changes of the working gases
Implementation Method 2
the first piston configured to cause volumetric changes of the working gases in each of the high-temperature space portion and the low-temperature space portion and transmit motive energy on receipt of pressure changes of the working gases
Implementation Method 3
the second piston and the third piston configured to transfer the working gases between the high-temperature space portion and the low-temperature space portion and move with a phase difference from each other with respect to the regenerator
Data Source
AI summary
A heat engine includes: a high-temperature space portion and a low-temperature space portion, each of which has a working gas with a different temperature range from each other; a regenerator provided between both of the space portions; a first piston configured to cause volumetric changes of the working gases in the space portions and transmit motive energy on receipt of pressure changes of the working gases; and a second piston and a third piston configured to transfer the working gases between both of the space portions and move with a 180° phase difference from each other with respect to the regenerator. The second piston is slidably housed in a cylinder portion included in the first piston. Heat and motive energy are exchanged by using the volumetric changes in both of the space portions, as well as by using the transfer of the working gases.