Two-Stroke Engine Port Timing Inversion for Compression

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Solution Overview

Problem

Conventional two-stroke engines face issues with unclean exhaust gases due to simultaneous opening of inlet and exhaust ports, leading to reduced compression rate and efficiency at higher engine speeds, and limitations in utilizing exhaust-driven turbines for pressurized charge air production.

Innovation Solution

The two-stroke engine design positions the inlet port above the exhaust port, with the exhaust port closing before the inlet port opens, utilizing a controllable valve to introduce combustion air after the exhaust gases have been evacuated, creating a negative pressure for efficient air intake and reducing port opening duration as speed increases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If the exhaust valve opens early to discharge exhaust gas before the inlet valve opens, then the exhaust gas discharge is improved, but the compression rate is reduced and efficiency decreases at higher engine speeds

Engineering Contradiction:

Improveexhaust gas dischargeVSAvoidcompression rate

Core Design Contradiction:

Object-generated harmful factorsVSProductivity

Solution Approach 1:

The patent inverts the conventional valve timing sequence by closing the exhaust valve before the inlet valve opens, rather than opening the exhaust valve before the inlet valve closes. This reversal of the traditional approach eliminates the period where both valves are open simultaneously, preventing the harmful mixing of fresh charge air with exhaust gases while maintaining adequate compression time even at high engine speeds

Inventive Principle:

Principle #13The other way round (Inversion)

2Productivity

If the inlet and exhaust ports are open simultaneously for gas exchange, then the gas exchange efficiency is improved, but unclean exhaust gas is discharged due to combustion air with fuel and lubricating oil flowing out through the exhaust port

Engineering Contradiction:

Improvegas exchange efficiencyVSAvoidunclean exhaust gas discharge

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent reverses the conventional port operation sequence by closing the exhaust port before the inlet port opens, rather than opening the inlet port before closing the exhaust port. This inversion ensures that the exhaust port is closed while the inlet port is opening, preventing any overlap where both ports are simultaneously open and thus eliminating the discharge of unclean exhaust gas containing unburnt fuel and lubricating oil

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The exhaust port is closed in advance before the inlet port opens, creating a preliminary separation between the exhaust and intake phases. This preliminary action ensures that the cylinder is sealed against exhaust gases before fresh charge air begins to enter, preventing contamination of the incoming air-fuel mixture with exhaust residues

Inventive Principle:

Principle #10Preliminary action

3Speed

If the compression stroke time is reduced to accommodate higher engine speeds, then the engine speed is improved, but the compression rate is reduced resulting in reduced efficiency

Engineering Contradiction:

Improveengine speedVSAvoidcompression rate

Core Design Contradiction:

SpeedVSProductivity

Solution Approach 1:

The patent inverts the conventional valve timing to close the exhaust valve before the inlet valve opens, which eliminates the harmful overlap period. This inversion allows for more effective utilization of the available compression time, maintaining adequate compression rates even at high engine speeds by ensuring that the compression process is not compromised by simultaneous port openings

Inventive Principle:

Principle #13The other way round (Inversion)

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 ensures constant compression rate and improved efficiency across varying speeds, prevents unclean exhaust gas issues, and enhances the effectiveness of exhaust-driven turbines by maintaining negative pressure for optimal air intake, even at high engine speeds.

Implementation Method 1

creating a negative pressure for efficient air intake

Methodology Applied

Scientific EffectNegative pressure: Pressure Drop

Implementation Method 2

combustion air is introduced to the combustion space from an inlet pipe via a controllable valve

Methodology Applied

Scientific EffectFluid flow:

Implementation Method 3

compression of introduced combustion air is initiated

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentEP3698030B1Method in a two-stroke engine and two-stroke engine

Publication Date: 2024.05.15 HEDMAN ERICSSON PATENT AB

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AI summary

The present invention concerns a method in a two-stroke engine comprising at least one cylinder (1) with a reciprocating piston (2), a delimited combustion space (5), at least one outlet port (7) and an inlet port (9) which are both uncovered at the bottom dead center position of the piston, an actuator (8) which activates a valve (17) to open and introduce combustion air via an inlet pipe (6), a control system (15) which controls the actuator to open the valve in order to introduce combustion air via the inlet port. The invention is characterized in that the inlet port is closed by the piston after the outlet port has been closed, thus the opposite compared to the two-stroke engines of today.