Pre-chamber Ignition System Flame Propagation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In after-top-dead-center ignition control modes, the reduced flow of mixture in the pre-chamber due to breaking of tumble or swirl results in decreased spark elongation, making it difficult to ignite fuel efficiently and causing a slower propagation of the flame to the main chamber.
Innovation Solution
The ignition system includes a dividing wall that separates the combustion chamber into a main chamber and a pre-chamber, with at least one spray hole for communication between them. A spark plug creates a spark across a gap between electrodes, with the ignition source being placed in the spray hole-nearby region, the spray hole, or the main chamber within 20° after the ignition timing to facilitate quick flame propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If after-top-dead-center ignition control is performed to warm up the catalyst, then the thermal energy transmission efficiency to the catalyst is improved, but the flame propagation speed to the main chamber is reduced
Solution Approach 1:
The combustion chamber is divided into a pre-chamber and a main chamber separated by a dividing wall with spray holes. The spark plug is located in the pre-chamber, creating a segmented ignition system where combustion starts in the pre-chamber and then propagates to the main chamber through the spray holes, enabling controlled flame propagation while maintaining thermal efficiency.
Solution Approach 2:
The spark plug electrode is specifically positioned to create a spark gap near the spray holes in the pre-chamber. This local positioning ensures that the ignition source is optimally placed to ignite the fuel-air mixture near the communication openings, facilitating rapid flame propagation into the main chamber while maintaining efficient energy transfer.
2Reliability
If the spark plug creates a spark in the pre-chamber, then the fuel ignition is achieved, but the spark elongation is reduced due to reduced mixture flow
Solution Approach 1:
The spray holes in the dividing wall act as intermediaries that guide and concentrate the fuel spray into the pre-chamber near the spark gap. This intermediary structure ensures that the fuel is delivered precisely where the spark is generated, compensating for reduced mixture flow and ensuring reliable ignition even when spark elongation is limited.
Solution Approach 2:
The fuel spray is injected into the pre-chamber before the spark is generated, preparing the fuel-air mixture in advance near the spark gap. This preliminary action ensures that when the spark occurs, the fuel is already positioned optimally for ignition, compensating for the reduced spark elongation caused by lower mixture flow rates.
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 configuration allows for the quick propagation of the flame to the main chamber, enhancing combustion efficiency and reducing the duration of the fast idling mode, which improves fuel consumption and reduces exhaust emissions.
Implementation Method 1
The spark plug works to create an electrical spark to ignite fuel upon application of voltage across a spark gap within the pre-chamber
Implementation Method 2
ignite fuel to produce a flame which, in turn, jets into the main chamber, thereby facilitating the combustion of the fuel within the combustion chamber
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
An ignition system includes a dividing wall (34) which divides a combustion chamber (30) of an engine (90) into a main chamber (31) and a pre-chamber (38) and has formed therein at least one spray hole (35) which communicates between the main chamber and the pre-chamber, and a spark plug (40) in which voltage is applied across a spark gap (45) between a first electrode (44) and a second electrode (46) to create an electrical spark (f) to ignite fuel. The pre-chamber has the first electrode. The dividing wall or a member which electrically conducts with the dividing wall has the second electrode. The ignition system executes an after-top-dead-center ignition control mode to ignite fuel after a compression stroke top dead center (Td). In the after-top-dead-center ignition control mode, an ignition source which is in the form of a self-growable flame kernel is provided in a spray hole-nearby region (R), the spray hole, or the main chamber within a crank angle of 20° after an ignition timing (Ts) at which the voltage starts to be applied across the spark gap. The spray hole-nearby region is a region which is located 3mm or less away from a spray hole center in the pre-chamber.