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Flame Kernel Development for a Spark Initiated Pre-Chamber Combustion System Capable of High Load, High Efficiency and Near Zero NOx Emissions
Journal Article
2010-01-2260
ISSN: 1946-3936, e-ISSN: 1946-3944
Sector:
Topic:
Citation:
Attard, W. and Parsons, P., "Flame Kernel Development for a Spark Initiated Pre-Chamber Combustion System Capable of High Load, High Efficiency and Near Zero NOx Emissions," SAE Int. J. Engines 3(2):408-427, 2010, https://doi.org/10.4271/2010-01-2260.
Language:
English
Abstract:
Turbulent Jet Ignition is an advanced spark-initiated
pre-chamber combustion system for an otherwise standard spark
ignition engine found in current on-road vehicles. This
next-generation pre-chamber design simply replaces the spark plug
in a conventional spark ignition engine. Turbulent Jet Ignition
enables very fast burn rates due to the ignition system producing
multiple, widely distributed ignition sites, which consume the main
charge rapidly. This high energy ignition system results from the
partially combusted (reacting) pre-chamber products initiating main
chamber combustion. The fast burn rates allow for increased levels
of dilution (lean burn and/or EGR) when compared to conventional
spark ignition combustion, with dilution levels being comparable to
other low temperature combustion technologies (HCCI) without the
complex control drawbacks.
Previous Turbulent Jet Ignition experimental results have
highlighted peak net indicated thermal efficiency values of 42% in
a standard modern engine platform. Additionally, the pre-chamber
combustion system is capable of tolerating up to 54% mass fraction
diluent (excess air and EGR) at the worldwide mapping point of 1500
rev/min, 3.3 bar IMEPn (~2.62 bar BMEP), resulting in an 18%
improvement in fuel economy and near-zero engine-out NOx
emissions.
This paper focuses on single-cylinder experiments at the
worldwide mapping point, which attempted to extend the dilution
level further by altering the flame kernel development inside the
very small but rich pre-chamber environment. Turbulent Jet Ignition
experiments incorporated previous techniques found to affect the
dilution limits in conventional spark ignition combustions systems.
This included variations in spark plug type, orientation, location
and electrode gap for the spark plug-initiated pre-chamber
combustion system. Experimental results highlighted that the
pre-chamber combustion system is quite robust and largely
unaffected by these changes, unlike conventional spark ignition
combustion, as long as combustion inside the pre-chamber can be
initiated. This occurs as combustion in the heavily diluted main
chamber is driven by the chemical, thermal and turbulence effects
of the propagating jet exiting the pre-chamber and not the flame
front itself. Nevertheless, experiments found that eliminating the
dead volume near the spark plug inside the pre-chamber, was
beneficial in reducing the trapped residuals and thus enabled the
dilution level to be slightly improved from an exhaust lambda of
2.08 to 2.14 (54 to 56% mass fraction diluent).