Pre-Chamber Over-Scavenging for Transient Engine Response
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Solution Overview
Problem
Internal combustion engines with large swept volumes face challenges in ignition performance due to lean air-fuel mixtures and delayed response to transient operation conditions, such as load changes, which affect combustion efficiency and emissions.
Innovation Solution
The control unit configures the pre-chamber supply system to exceed its volume, with a surplus of the fuel or air-fuel mixture being communicated to the main combustion chamber, enhancing mixing and reaction speed during transient operations by 'over-scavenging', thereby bridging the delay in fuel delivery and improving combustion stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a lean air fuel mixture is used in the main combustion chamber to reduce emissions, then NOx and unburnt hydrocarbon emissions are reduced, but ignition performance suffers due to reduced tendency towards controlled combustion
Solution Approach 1:
The combustion chamber is divided into two segments: a pre-chamber and a main combustion chamber. The pre-chamber receives a richer air-fuel mixture for reliable ignition, while the main combustion chamber operates with a lean mixture for low emissions. The pre-chamber acts as an ignition source that transfers combustion to the main chamber through transfer passages.
Solution Approach 2:
The pre-chamber serves as an intermediary between the fuel supply system and the main combustion chamber. It prepares a controlled ignition mixture that then ignites the lean mixture in the main chamber, mediating between the need for reliable combustion initiation and the requirement for clean burning.
2Stability of the object's composition
If the pre-chamber supply system is controlled to supply exactly the pre-chamber volume, then the pre-chamber is properly filled, but during transient operation conditions there is a delay in responding to load changes due to travel time between compressor and intake manifold
Solution Approach 1:
The pre-chamber supply system is controlled to supply a larger volume of air-fuel mixture than the pre-chamber volume during transient operation conditions. This preliminary action of over-supplying the mixture allows the system to respond more quickly to load changes, as the excess mixture is already available in the pre-chamber and transfer passages.
Solution Approach 2:
The control system dynamically adjusts the supply volume based on operating conditions. During transient operations, the supply volume exceeds the pre-chamber volume to enable faster response, while during steady-state operation, the supply volume matches the pre-chamber volume for optimal mixture composition.
3Productivity
If the supply volume of the pre-chamber is increased to exceed the pre-chamber volume during transient operation, then the response to load changes is improved and combustion stability is enhanced, but the mixture composition in the pre-chamber becomes richer than optimal for the pre-chamber itself
Solution Approach 1:
The pre-chamber and main combustion chamber are merged into a functional system where the pre-chamber not only serves its traditional ignition function but also acts as a buffer reservoir during transient operations. The excess mixture supplied to the pre-chamber is subsequently transferred to the main combustion chamber, combining the functions of mixture preparation and transient response buffering.
Solution Approach 2:
The pre-chamber performs multiple functions: it serves as an ignition chamber for the main combustion chamber, acts as a mixture preparation zone, and functions as a buffer reservoir during transient operations. This multi-functionality allows the system to prioritize response speed during transients without permanently compromising pre-chamber mixture quality.
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 improves engine performance during transient conditions, reduces emissions, and enhances combustion efficiency by optimizing mixtures and injection windows in both pre-chamber and main combustion chamber systems, leading to faster start-up, reduced cycle fluctuations, and improved robustness.
Implementation Method 1
a surplus of the supply volume is communicated to the main combustion chamber through transfer passages between the pre-chamber and the main combustion chamber, where it mixes with the air or the second air-fuel mixture supplied to the main combustion chamber
Implementation Method 2
a smaller volume of air fuel mixture within the pre-chamber is ignited by, e.g., a spark plug. This combustion of a smaller volume of air fuel mixture is then transferred to the main combustion chamber through the transfer passages, resulting in flame jets expanding into the main combustion chamber
Data Source
AI summary
An internal combustion engine includes transfer passages between a pre-chamber and a main combustion chamber, and a control unit configured to control a pre-chamber supply system coupled to the pre-chamber and a main combustion chamber supply system coupled to the main combustion chamber, wherein the control unit is configured to control the pre-chamber supply system such that a supply volume exceeds a volume of the pre-chamber and that a surplus of the supply volume is communicated to the main combustion chamber, such as during a transient operating condition.