Spark-Ignition Two-Valve Engine Combustion Chamber Design
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Solution Overview
Problem
Spark-ignition type two-valve engines face challenges in improving thermal efficiency due to focus on combustion speed, leading to thermal losses and reduced mechanical efficiency with conventional designs.
Innovation Solution
A spark-ignition type two-valve engine design featuring a single center tumble port with a separation enhancing part and a long piston stroke, which produces a fast tumble flow to reduce combustion time and thermal losses, while maintaining a reduced flame propagation distance and increased mechanical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If combustion speed is increased by using squish flow or tumble flow, then thermal efficiency is improved, but thermal losses increase due to rapid temperature rise in local parts
Solution Approach 1:
The piston crown is designed with a specific recessed shape that creates a localized squish area. This recessed portion is positioned to receive tumble flow while maintaining a controlled squish region, allowing different areas of the combustion chamber to have different flow characteristics - tumble flow in the recessed area and squish flow at the periphery - thereby improving combustion speed while controlling thermal losses
2Productivity
If piston stroke is increased to reduce combustion chamber diameter, then thermal efficiency is improved, but mechanical losses increase due to longer piston movement
Solution Approach 1:
The invention optimizes the ratio between piston stroke and combustion chamber diameter. By setting the piston stroke to be longer than the combustion chamber diameter, the design achieves improved thermal efficiency through better flame propagation control while managing mechanical losses through the specific geometric relationship between stroke length and chamber dimensions
3Loss of time
If single center tumble port is used to produce fast tumble flow, then combustion time is reduced, but flame propagation distance is constrained
Solution Approach 1:
The combustion chamber is effectively segmented into different flow zones by the recessed portion design. The tumble flow is concentrated in the recessed area while the squish flow operates at the periphery, creating distinct combustion zones that allow fast combustion in the tumble region while maintaining controlled flame propagation distance overall
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 design enhances thermal efficiency by minimizing heat dissipation and mechanical losses, achieving improved fuel consumption and performance in smaller engine sizes.
Implementation Method 1
a separation enhancing part configured to cause gas being flown to the gas inlet to flow separate away from a wall surface continuous with the gas inlet such that a tumble flow tumbling about an axis that extends in a direction intersecting the reciprocation direction is imparted to gas taken into the combustion chamber
Implementation Method 2
an offset ignition plug including an offset ignition part configured to apply spark ignition to gas in the combustion chamber
Implementation Method 3
a piston part configured to reciprocate, the piston part defining a combustion chamber
Data Source
Figure 1(A)~1(B)
Figure 2
Figure 3
AI summary
The present teaching provides a spark-ignition type two-valve engine that can improve a thermal efficiency. A spark-ignition type two-valve engine includes a piston part, a crankshaft, only one exhaust port, only one single center tumble port, an offset ignition plug, and a small-diameter long-stroke cylinder that cooperates with the piston part to define a combustion chamber. The combustion chamber is formed in such a manner that: the combustion chamber has a diameter shorter than a reciprocation stroke length of the piston part when viewed in a reciprocation direction; and as the piston part moves toward a bottom dead center by a stroke length longer than the diameter of the combustion chamber when viewed in the reciprocation direction, a tumble flow is imparted to gas taken from the single center tumble port, while as the piston part moves toward a top dead center by a stroke length longer than the diameter, the gas pushed by the piston part flows toward a gas inlet.