Asymmetric Stirling Engine Cylinder Offset for Compact Design
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Solution Overview
Problem
Gamma type Stirling engines are bulky, complex, and inefficient due to their 90° cylinder configuration, limiting their flexibility and performance, especially in applications requiring constant energy delivery, and they do not allow for variations in power modulation.
Innovation Solution
The engine design features a first and second cylinder angularly offset with pistons connected through crank means having offset pivoting axes and radial distances, optimizing thermodynamic efficiency and heat exchanges by differentiating piston kinematics and reducing bulk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gamma type Stirling engine configuration with 90° cylinder arrangement is used, then the engine can achieve continuous and constant energy delivery, but the engine becomes bulky and complex
Solution Approach 1:
The patent applies asymmetry by offsetting the cylinders from the traditional 90° quadrature configuration to a different angular arrangement. This asymmetric configuration reduces the bulk and complexity of the engine while maintaining the ability to deliver continuous energy through the optimized spatial relationship between cylinders and pistons.
Solution Approach 2:
The patent implements dynamic piston motion through offset crank mechanisms with different radial distances. The first piston and second piston follow different kinematic paths with varying speeds and strokes, creating a dynamic system that maintains continuous power delivery while reducing structural complexity compared to symmetric gamma configuration.
2Reliability
If gamma type Stirling engine configuration with 90° cylinder arrangement is used, then the engine can achieve continuous and constant energy delivery, but the engine volume increases
Solution Approach 1:
By deviating from the symmetric 90° gamma configuration and adopting an asymmetric angular offset between cylinders, the engine achieves a more compact arrangement. This asymmetric layout reduces the overall engine volume while preserving the continuous energy delivery capability through optimized piston-crank geometry.
Solution Approach 2:
The patent reconfigures the spatial arrangement of cylinders and pistons by changing the angular offset dimension from the traditional 90° to a different angle. This dimensional change optimizes the space utilization and reduces the engine's external bulk while maintaining internal volumetric efficiency for continuous power output.
3Adaptability or versatility
If variable configuration engine with adjustable cylinder angle is used, then the rotation speed can be varied, but the functioning performance decreases due to increased idle volumes
Solution Approach 1:
The patent employs parameter changes by varying the radial distances of crank pins from the rotation axis and adjusting the angular offset between cylinders. These parameter variations enable rotation speed control while optimizing the piston motion profiles to minimize idle volumes and associated energy losses, unlike variable configuration engines that increase idle volumes.
Solution Approach 2:
The offset crank mechanisms are pre-configured with specific radial distances and angular positions to optimize piston motion before operation begins. This preliminary optimization ensures that during variable speed operation, the pistons maintain efficient motion patterns that minimize idle volumes and energy losses throughout the operating range.
4Adaptability or versatility
If variable configuration engine with adjustable cylinder angle is used, then the rotation speed can be varied, but the device complexity increases
Solution Approach 1:
The patent achieves rotation speed variation through parameter changes in the fixed offset crank mechanisms rather than through adjustable configuration mechanisms. By varying operational parameters within the fixed geometric framework, the engine achieves adaptability without increasing mechanical complexity.
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 results in a compact, efficient, and economical engine with improved power output and reduced bulk, enhancing the engine's ability to handle varying energy demands without sacrificing performance.
Implementation Method 1
an external combustion engine, also known as a Stirling engine, which exploits a cycle of isothermal expansion and compression of a thermodynamic fluid
Implementation Method 2
a cycle of isothermal expansion and compression of a thermodynamic fluid
Implementation Method 3
an external combustion engine, also known as a Stirling engine, which exploits a cycle of isothermal expansion and compression
Implementation Method 4
The hot part and the cold part of the first cylinder are respectively heated and cooled to transfer heat to the thermodynamic fluid contained in the first cylinder
Implementation Method 5
By exploiting the expansion of the thermodynamic fluid due to the contribution of heat from the hot part, the second piston moves toward its lower dead point
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
External combustion engine which comprises a first cylinder (11) and a second cylinder (12), in which a first piston (20) and a second piston (30) are able to slide respectively. The first (11) and second cylinder (12) are fluidically connected with respect to each other for the passage of a heat-carrying fluid suitable to determine the cyclical movement of the first piston (20) and the second piston (30). The external combustion engine also comprises a drive shaft (21) rotating around an axis of rotation (Z), and with which crank means (25) are solidly associated, provided with at least a first pin (26) and a second pin (32) having pivoting axes (J, K) parallel to each other, and also disposed distanced radially from the axis of rotation (Z). The external combustion engine also comprises first (22, 23) and second (31) kinematic connection means suitable to connect respectively the first pin (26) and the second pin (32) to the first piston (20) and respectively to the second piston (30). The first pin (26) and the second pin (32) are disposed with the respective pivoting axes (J, K) angularly offset so as to be angled by a desired angular amplitude equal to a first acute angle (beta) with respect to the axis of rotation (Z).