Active Scavenge Prechamber for Large Gas Engines
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Solution Overview
Problem
Large gas engines with cylinder bore diameters greater than 200 mm face challenges in achieving efficient combustion and reducing pollutant emissions due to inadequate performance of passive prechambers with large displacement and high power density, leading to poor scavenging of the crevice volume and increased risk of preignition.
Innovation Solution
The implementation of an active scavenging prechamber system with auxiliary scavenging ports that admit fresh fuel-air mixtures directly to the crevice volume, creating a uniform high-velocity flow and reducing flame jet momentum, which improves combustion efficiency and power output while minimizing pollutant emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive prechambers are used in large gas engines, then the engine structure is simple, but the combustion efficiency is poor and pollutant emissions increase
Solution Approach 1:
The prechamber design transitions from a static passive structure to a dynamic active system with movable piston that controls scavenging timing and intensity, optimizing combustion efficiency while maintaining structural feasibility
Solution Approach 2:
The prechamber is divided into functional zones including crevice volume, combustion chamber, and scavenging ports, allowing independent optimization of each region's performance characteristics
2Device complexity
If passive prechambers are used, then the device complexity is low, but the crevice volume scavenging is inadequate leading to preignition
Solution Approach 1:
The active piston mechanism dynamically controls the timing and extent of crevice volume scavenging, ensuring fresh charge replacement at optimal moments to prevent preignition while avoiding excessive mechanical complexity
Solution Approach 2:
The system performs preliminary scavenging of the crevice volume before main combustion, removing residual hot gases and unburnt fuel that could cause preignition, preparing the chamber for reliable combustion
3Device complexity
If passive prechambers are used, then the system is simple, but the flame propagation rate is insufficient for lean mixtures
Solution Approach 1:
The system extracts and concentrates combustion energy through controlled flame jet formation, directing high-velocity flames into the main combustion chamber to accelerate flame propagation in lean mixtures without complicating the prechamber structure
Solution Approach 2:
The active piston modifies combustion chamber parameters including pressure, temperature, and gas velocity dynamically, optimizing flame propagation speed for lean fuel-air mixtures while maintaining system simplicity
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
The active scavenging prechamber system enhances engine power output and reduces pollutant emissions by ensuring efficient scavenging of the crevice volume, preventing preignition, and maintaining uniform flow and lambda distribution, thereby improving combustion efficiency.
Implementation Method 1
one or more auxiliary scavenging ports each comprising an inlet for communicating with a main combustion chamber and an outlet communicating with the crevice volume
Implementation Method 2
improves the combustion efficiency of a prechamber, increases the engine power output and reduces the emission of pollutants from engine combustion
Data Source
AI summary
In certain embodiments with large size prechambers and/or with prechambers that have large spark-gap electrode assemblies, a poor scavenge of the crevice volume may cause deterioration of the preignition margin, which then may limit the power rating of the engine, may cause the flow velocity field of the fuel-air mixture to be excessively uneven and may result in the deterioration of the misfire limit. One or more auxiliary scavenging ports may allow admission of fuel rich mixture to the crevice volume, thereby cooling the residual gases and preventing occurrence of preignition. More organized and powerful flow velocity fields may be obtained in the spark-gap electrode assembly region. This condition may result in a significant extension of the flammability limit and may significantly improve the combustion efficiency of the prechamber. Passive prechambers using the active scavenge concept may increase the engine power output and reduce the emission of pollutants from engine combustion.