Dual Exhaust Cam Combustion Engine
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Solution Overview
Problem
Conventional internal combustion engines face issues with high operating temperatures leading to undesirable emissions, increased nitrogen oxide content, and a higher risk of auto-ignition due to restricted airflow and hot exhaust valves, which limit power output and efficiency.
Innovation Solution
A four-stroke internal combustion engine design featuring a dual exhaust cam system with angularly adjustable No. 2 exhaust cam, allowing for optional closure of the exhaust valve during the compression stroke, and piston valves with directed airflow to cool the exhaust valve, enabling increased airflow and reduced likelihood of auto-ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional valve timing mechanisms are used with valve overlap, then charge of combustible mixture can be drawn into the combustion chamber economically, but unspent hydrocarbons pass directly out of the exhaust valve increasing emissions
Solution Approach 1:
The exhaust valve operation is segmented into two independent cam systems: a primary cam for normal exhaust function and a secondary cam for selective additional opening during the compression stroke. This segmentation allows the valve to perform multiple functions at different times, preventing hydrocarbon emissions during compression while maintaining normal exhaust operation during the exhaust stroke.
Solution Approach 2:
The valve timing system is made dynamic through the selective engagement of the secondary cam. The secondary cam can be rotated into or out of engagement with the valve mechanism, allowing the system to adaptively change valve timing characteristics based on operating conditions, thereby preventing hydrocarbon emissions during compression stroke when needed.
2Productivity
If exhaust valve remains closed during compression stroke, then compression ratio can be increased, but operating temperature increases leading to auto-ignition risk
Solution Approach 1:
The secondary cam is positioned to open the exhaust valve in advance during the compression stroke, before the combustion event occurs. This preliminary action allows hot gases to escape before they can reach temperatures that would cause auto-ignition, while still maintaining the benefits of compression for the remaining charge.
Solution Approach 2:
The secondary cam mechanism allows the system to skip through the problematic high-temperature phase by opening the exhaust valve during compression, rapidly expelling hot gases and preventing the temperature buildup that would lead to auto-ignition.
3Adaptability or versatility
If dual cam system with selective engagement is used, then valve timing can be optimized for different operating conditions, but device complexity increases
Solution Approach 1:
The two cam systems are merged into a single integrated mechanism where the secondary cam can be selectively engaged with the primary cam shaft. This merging approach allows the system to maintain simplicity during normal operation (using only the primary cam) while providing enhanced functionality when the secondary cam is engaged, reducing the overall complexity compared to having two completely independent systems.
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 engine operates at a cooler temperature, reduces emissions, increases power output, and allows for higher compression ratios, enhancing efficiency and extending component lifespan by minimizing auto-ignition risks.
Implementation Method 1
piston valves with directed airflow to cool the exhaust valve
Data Source
AI summary
A four-stroke internal combustion engine comprising an inlet cam configured to open and close an inlet valve, a No. 1 exhaust cam configured to open and close an exhaust valve, a No. 2 exhaust cam configured to open and close the same exhaust valve, wherein the No. 2 exhaust cam is angularly adjustable relative to the No. 1 exhaust cam in response to input from an operator, so that the No. 2 exhaust cam is able to be selectively engaged; wherein the No. 1 exhaust cam is configured to open and close the exhaust valve during the compression stroke, so that a selected quantity of air drawn in during the intake stroke is expelled during the compression stroke; and wherein the No. 2 exhaust cam is configured to optionally close the exhaust valve when engaged.