Rotary Engine Variable Speed Passive Piston Thermal Efficiency
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Solution Overview
Problem
Conventional rotary engines, such as the Wankel engine, suffer from high heat loss and incomplete combustion due to their geometrically narrow and long working chambers, leading to lower thermal efficiency compared to reciprocating engines.
Innovation Solution
A rotary engine design featuring a doughnut-shaped cylinder with a pair of power and passive pistons, where the passive piston is driven by a variable speed mechanism, including a partially toothed gear system or a Geneva mechanism, to optimize the working chamber volume changes during the engine cycle, allowing for efficient air intake, compression, combustion, and emission processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a Wankel engine uses an oval-like epitrochoid-shaped working chamber, then the engine can achieve continuous rotation and power output, but the high surface-to-volume ratio causes relatively high heat loss and incomplete combustion, resulting in lower thermal efficiency
Solution Approach 1:
The engine divides the working chamber into two separate chambers: a power chamber where combustion occurs and a compression chamber that does not participate in combustion. This segmentation allows the power chamber to have optimal combustion characteristics while the compression chamber handles volume changes, resolving the contradiction between continuous rotation and thermal efficiency
Solution Approach 2:
The passive piston acts as an intermediary component that controls the volume of the compression chamber without being directly subjected to combustion forces. This mediator enables precise control over compression ratios and chamber volumes, improving thermal efficiency while maintaining continuous rotation capability
2Loss of energy
If a passive piston is added to control working chamber volume, then thermal efficiency is improved through precise volume control, but the device complexity increases due to additional driving mechanisms
Solution Approach 1:
The passive piston is integrated with the power piston through a shared crankshaft mechanism, combining their motions to achieve the desired volume changes. This merging reduces the need for separate complex driving systems while maintaining thermal efficiency improvements
Solution Approach 2:
The passive piston undergoes periodic acceleration and deceleration in synchronization with the power piston's cycle, creating the necessary volume changes for improved combustion efficiency. This periodic action is achieved through the crankshaft mechanism rather than continuous complex actuation
3Productivity
If the passive piston rotates at variable speeds using a gear system, then the working chamber volume changes are optimized for efficient combustion, but frictional losses and mechanical complexity increase
Solution Approach 1:
The gear system is extracted and placed in an external transmission housing separate from the main combustion chamber. This extraction reduces the number of moving parts within the high-temperature combustion environment, minimizing frictional losses while maintaining the ability to optimize chamber volume changes for combustion efficiency
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 reduces frictional losses and enhances thermal efficiency by ensuring precise control over the working chamber volume changes, mimicking the full engine cycle of reciprocating engines while minimizing mechanical friction and noise.
Implementation Method 1
A rotary engine design featuring a doughnut-shaped cylinder with a pair of power and passive pistons, where the passive piston is driven by a variable speed mechanism, including a partially toothed gear system or a Geneva mechanism
Implementation Method 2
Igniting by a spark plug, combustion of the mixture of air and fuel may take place in the cylinder. Heated air expands and pushes the pistons downward
Implementation Method 3
Heated air expands and pushes the pistons downward
Implementation Method 4
Via a connecting rod and a crankshaft, the linear movement of the piston is then converted to a rotating movement of the crankshaft
Data Source
AI summary
One embodiment may include a rotary engine, whose cylinder is in doughnut-shape. A cross-section of the cylinder is circular. The engine includes a pair of rotation disks, a power disk and passive disk. A power-output shaft is coaxial with an axis of the cylinder. A power piston and passive piston rotate around an axis of the power-output shaft. A space between the power piston in front and the passive piston at the back is a working chamber. When combustion and expansion take place in the working chamber, the power piston will be pushed forward continuously by the expanding gases, and output power via the power-output shaft. The passive piston relies on a driving system to drive it moving forward. Volume of the working chamber varies within one revolution of rotation. Larger volume of the working chamber causes combustion and expansion. Smaller volume of the working chamber causes compression and emission.