Two-Stroke Engine Porting for Gas Transfer Efficiency
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Solution Overview
Problem
Two-stroke engines face inefficiencies in gas transfer within the cylinder, leading to suboptimal primary compression ratio and the need for expensive crankshaft assemblies due to the lack of a pressurized lubrication system, resulting in oil burning and pollution.
Innovation Solution
A gas transfer port system with a fixed separator plate and annular skirt that includes long and short gas transfer ports, directing gas flow efficiently from the underside of the piston to the combustion chamber, enhancing gas transfer and compression ratio while isolating the upper cylinder section from the crankcase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a fixed separator plate is used to divide the cylinder into upper and lower sections, then the primary compression ratio is increased and pressurized lubrication is enabled, but the gas transfer efficiency from the lower section to the combustion chamber deteriorates
Solution Approach 1:
The gas transfer port is divided into two distinct sections: an upper port section and a lower port section. The upper section has a larger cross-sectional area to facilitate efficient gas transfer to the combustion chamber, while the lower section is restricted to control gas flow from the lower cylinder section. This segmentation allows the system to maintain both high compression ratio and efficient gas transfer.
2Device complexity
If roller bearings are used on the crankshaft to operate in oil/fuel mix without pressurized lubrication, then the engine can function without a pressurized lubrication system, but the crankshaft assembly becomes heavy and expensive
Solution Approach 1:
The invention extracts the lubrication requirement from the crankshaft operation by enabling pressurized lubrication for the piston through the fixed separator plate arrangement. This allows the use of simpler slipper bearings on the crankshaft instead of heavy roller bearings, reducing both weight and cost while maintaining reliable lubrication.
3Reliability
If oil is added to the air/fuel mixture for piston lubrication without pressurized lubrication system, then the piston can be lubricated, but oil is burned causing pollution
Solution Approach 1:
The fixed separator plate acts as an intermediary that enables a dedicated pressurized lubrication system for the piston. This separates the lubrication function from the combustion process, allowing oil to be delivered directly to the piston via pressurized lubrication channels rather than being mixed with the air/fuel charge, thereby eliminating oil burning and pollution while ensuring reliable piston lubrication.
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 system improves gas transfer efficiency, increases the primary compression ratio, and simplifies the crankshaft construction, reducing oil consumption and pollution by optimizing the flow of gases within the two-stroke engine.
Implementation Method 1
at least one long gas transfer port connecting a lower portion of said annular well with a gas transfer port outlet aperture in a wall of said cylinder
Implementation Method 2
a fixed separator plate dividing said cylinder into an upper section, and a lower section... said well sealed at the bottom such that said cylinder is isolated from a crankcase of said engine
Data Source
AI summary
A gas transfer port system for a cylinder of a two stroke internal combustion engine; said cylinder provided with a fixed separator plate dividing said cylinder into an upper section and a lower section; a piston in said cylinder reciprocating between said separator plate and a cylinder head; and wherein an annular skirt descending from said separator plate forms at least a portion of an annular well between said skirt and an internal surface of said cylinder; said well sealed at the bottom such that said cylinder is isolated from a crankcase of said engine; said gas transfer port system including at least one long gas transfer port connecting a lower portion of said annular well with a gas transfer port outlet aperture in a wall of said cylinder.