Passive Pre-Chamber Engine Combustion Stability
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Solution Overview
Problem
Existing gasoline internal combustion engines with combustion pre-chambers are not compatible with conventional trivalent catalysts and face challenges in meeting emission regulations at low temperatures and high engine loads, due to high surface/volume ratios and lean mixture operations.
Innovation Solution
The engine employs a 'passive' combustion pre-chamber without direct fuel or air injection, using a second spark plug with electrodes facing the main combustion chamber, and an electronic control unit to manage air/gas mixtures stoichiometrically, along with a reduced pre-chamber volume and high thermal conductivity materials for enhanced heat dissipation, allowing for increased compression ratios and reduced detonation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a combustion pre-chamber with high surface/volume ratio is used for lean-burn operation, then fuel efficiency is improved, but stable ignition at low temperatures becomes difficult and emission regulations cannot be met
Solution Approach 1:
The combustion system is segmented into two separate combustion chambers: a pre-chamber for efficient combustion and a main chamber for stable ignition. The pre-chamber contains a spark plug for reliable ignition, while the main chamber receives combustion products through communication holes, enabling stable operation across all temperature conditions while maintaining fuel efficiency.
Solution Approach 2:
The pre-chamber acts as an intermediary between the spark plug ignition source and the main combustion chamber. It receives the spark ignition, develops high-temperature combustion, and transfers combustion products to the main chamber, thereby enabling stable combustion at low temperatures without compromising fuel efficiency.
2Reliability
If an active combustion pre-chamber with direct fuel injection is used, then low-load ignition is improved, but compatibility with conventional trivalent catalysts is lost and emission regulations cannot be met
Solution Approach 1:
The fuel injection function is extracted from the pre-chamber system. Instead of injecting fuel directly into the pre-chamber, fuel is injected only into the main combustion chamber. The pre-chamber is filled with the air-fuel mixture from the main chamber through communication holes, eliminating the need for pre-chamber injection and enabling compatibility with conventional catalysts.
Solution Approach 2:
The pre-chamber serves multiple functions: providing a confined space for controlled combustion, generating high-temperature ignition sources, and transferring combustion products to the main chamber. This multi-functionality enables reliable low-load ignition without requiring direct fuel injection, thereby maintaining compatibility with conventional emission control systems.
3Reliability
If the pre-chamber volume is increased to improve combustion stability, then ignition reliability is improved, but detonation resistance at high loads decreases
Solution Approach 1:
The pre-chamber volume is optimized to a specific small size (0.3-0.8 mL) that provides sufficient combustion stability while limiting the total energy release. The communication holes between pre-chamber and main chamber are designed with specific dimensions and arrangements to control the transfer of combustion products, achieving both stability and detonation resistance through precise parameter optimization.
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 enables the engine to operate with a conventional trivalent catalyst, reduce fuel consumption by 30%, and minimize emissions, while maintaining compatibility with modern automotive comfort standards by modulating combustion duration and reducing exhaust gas temperatures.
Implementation Method 1
a first spark plug associated with each cylinder, mounted within a support element that is arranged within a cavity of said cylinder head and that defines a combustion pre-chamber having a first end facing the electrodes of said first spark plug
Implementation Method 2
a second spark plug associated with each cylinder, having electrodes directly facing the combustion chamber
Implementation Method 3
at least one electromagnetically-controlled gasoline injector device associated with each cylinder of the engine
Implementation Method 4
Gasoline internal combustion engine
Data Source
AI summary
An engine has, for each cylinder, a combustion chamber and a combustion pre-chamber communicating with the combustion chamber. First and second spark plugs are associated with the pre-chamber and combustion chamber, respectively. Gasoline is injected by an injector device directly into the combustion chamber and/or by an injector device into a cylinder intake duct. There is no device for injecting gasoline, air or an air/gasoline mixture directly into the pre-chamber. The engine operates with an air/gasoline mixture substantially corresponding to stoichiometric, for compatibility with an exhaust system having a trivalent catalyst. The pre-chamber is not used for engine operation with poor dosing, but to increase resistance to engine detonation. The engine can thus be configured with a high compression ratio, with a significant reduction in fuel consumption at the same power level. The second spark plug is only activated at low and medium engine loads to stabilize combustion.