Two-Stroke Engine Combustion Control for Stable Operation
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Solution Overview
Problem
Two-stroke engines exhibit irregular running and fluctuating noise due to late combustion, leading to incomplete scavenging and disturbed mixture preparation, especially at low RPMs and after startup, causing a rough running performance.
Innovation Solution
Control the number of combustions relative to the number of crankshaft revolutions, suppressing combustions in certain cycles to maintain a stable pressure in the crankcase and adjust fuel metering and ignition accordingly, allowing for a controlled four-stroke operation to ensure smooth running.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a two-stroke engine operates with combustion on every crankshaft revolution, then power output is maximized, but the engine exhibits irregular running and fluctuating noise due to uncontrolled four-stroke operation
Solution Approach 1:
The control unit implements periodic action by deliberately suppressing combustion in certain cycles according to a predetermined pattern. This creates regular intervals of combustion and non-combustion cycles, transforming the irregular uncontrolled four-stroke operation into a controlled periodic process that reduces running fluctuations and noise while maintaining acceptable power output
2Power
If late combustion occurs in the combustion chamber, then power is temporarily increased, but the pressure in the combustion chamber increases when transfer channels open, leading to incomplete scavenging and disturbed mixture preparation
Solution Approach 1:
The control unit applies preliminary action by detecting late combustion events and proactively suppressing the next combustion cycle before it occurs. This preventive measure allows the crankcase pressure to normalize and ensures complete scavenging of the combustion chamber before the next fuel injection and ignition, preventing the disturbance of mixture preparation that would otherwise occur
3Object-affected harmful factors
If the number of combustions is reduced relative to crankshaft revolutions, then running noise is reduced and mixture preparation is improved, but power output decreases
Solution Approach 1:
The control unit implements partial action by suppressing combustion in only certain cycles rather than continuously reducing the number of combustions. This selective suppression in specific cycles reduces running noise and improves mixture preparation while maintaining combustion frequency high enough to preserve acceptable power output, achieving a balance between noise reduction and power maintenance
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 approach results in a quiet, pleasant, and stable running performance by preventing uncontrolled four-stroke operation, reducing exhaust-gas values, and ensuring proper mixture preparation, thereby improving the overall operation of the two-stroke engine.
Implementation Method 1
a piston (7) mounted in the cylinder (2) to undergo a reciprocating movement along a stroke path between top dead center and bottom dead center
Implementation Method 2
an ignition unit (20) for igniting an air/fuel mixture in the combustion chamber (5)
Data Source
AI summary
The invention is directed to a method for operating a two-stroke engine having a cylinder in which a combustion chamber is formed and which includes devices for metering fuel and supplying combustion air as well as an ignition device for igniting a mixture in the combustion chamber. In the method, fuel and combustion air are supplied to the engine and the mixture in the combustion chamber is ignited. The combustion chamber is delimited by a piston which drives a crankshaft rotatably journalled in a crankcase. A control is provided which controls the metering of fuel and the ignition of the mixture in the combustion chamber. In the method, the two-stroke engine is controlled in at least one operating state so that the number of combustions is less than the number of revolutions of the crankshaft in the same time interval.