Multipoint Ignition Piston Cavities for Lean Burn Combustion
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Solution Overview
Problem
Natural gas engines, particularly large bore lean burn engines, face unstable combustion issues such as misfire when burning fuel with an excess of air or increased brake mean effective pressure, leading to incomplete ignition, reduced efficiency, and higher emissions.
Innovation Solution
A multipoint distributed ignition system is introduced, featuring a piston with a concave piston bowl and cavities around its circumference, where a fuel jet from a pre-chamber nozzle tip is injected into the combustion main chamber, creating multiple ignition points that enhance combustion plumes and ensure more complete fuel combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-point ignition system is used in natural gas engines, then the device complexity is low, but combustion stability deteriorates under conditions of excess air or increased brake mean effective pressure
Solution Approach 1:
The ignition system is segmented into multiple independent ignition points distributed around the combustion chamber. The piston crown includes multiple cavities (first cavity, second cavity, third cavity) that receive separate fuel jets, creating multiple discrete ignition zones rather than a single ignition point, thereby improving combustion stability without excessive complexity
Solution Approach 2:
Different regions of the combustion chamber are assigned different ignition characteristics. Each cavity is positioned at specific locations (first, second, and third cavities) with fuel jets oriented to create localized ignition zones that collectively ensure complete combustion throughout the chamber, addressing local combustion requirements
2Reliability
If a multipoint distributed ignition system with multiple cavities is implemented, then combustion stability improves, but device complexity increases
Solution Approach 1:
Multiple ignition functions are merged into a single integrated piston crown structure. The first cavity, second cavity, and third cavity are formed as part of the same piston component, sharing common fuel injection infrastructure and control systems, which reduces overall system complexity despite the multipoint ignition configuration
Solution Approach 2:
The piston crown serves multiple functions simultaneously: it contains the combustion chamber, provides structural support, and integrates multiple ignition cavities with fuel injection capability. This multi-functionality reduces the need for separate ignition components, thereby limiting the increase in device complexity
3Quantity of substance
If fuel is injected with excess air into the combustion chamber, then the air-fuel mixture is diluted, but combustion stability deteriorates and misfire occurs
Solution Approach 1:
The combustion chamber is divided into multiple zones with dedicated fuel jets (first, second, and third fuel jets) that can be independently controlled. This segmentation allows precise control of fuel injection timing and quantity at each zone, ensuring complete combustion even when excess air is present, thereby preventing misfire
Solution Approach 2:
Fuel is injected into the cavities before the main combustion event. The fuel jets deliver fuel to the first, second, and third cavities in advance, allowing the fuel-air mixture to be prepared and ignited reliably before the piston reaches the combustion stroke, ensuring stable combustion despite excess air conditions
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 system improves combustion stability, efficiency, and reduces unburned hydrocarbons and nitrogen oxides by ensuring more thorough fuel ignition and air mixture combustion.
Implementation Method 1
upon firing of a spark plug associated with each cylinder, the compressed mixture ignites. The expanding combustion gases resulting from the ignition move a piston within the cylinder
Implementation Method 2
the nozzle tip having at least one nozzle opening configured to inject a fuel jet into the combustion main chamber, wherein the piston includes a piston wall located around a circumference of the piston bowl, the piston wall including at least one cavity
Data Source
AI summary
The disclosure describes multipoint ignition systems for an engine and methods of operation of the same. The systems and methods can include an engine, including an engine block having at least one cylinder bore, a piston having a piston crown facing a flame deck surface such that a combustion main chamber is defined within a cylinder bore and located between the piston crown and the flame deck surface, the piston crown further including a piston bowl having a generally concave shape, and a combustion pre-chamber having a nozzle tip disposed in fluid communication with the combustion main chamber, the nozzle tip having at least one nozzle opening configured to inject a fuel jet into the combustion main chamber, wherein the piston includes a piston wall located around a circumference of the piston bowl, the piston wall including at least one cavity.