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Knock Limit Extension with a Gasoline Fueled Pre-Chamber Jet Igniter in a Modern Vehicle Powertrain
Journal Article
2012-01-1143
ISSN: 1946-3936, e-ISSN: 1946-3944
Sector:
Citation:
Attard, W., Blaxill, H., Anderson, E., and Litke, P., "Knock Limit Extension with a Gasoline Fueled Pre-Chamber Jet Igniter in a Modern Vehicle Powertrain," SAE Int. J. Engines 5(3):1201-1215, 2012, https://doi.org/10.4271/2012-01-1143.
Language:
English
Abstract:
Turbulent Jet Ignition is an advanced spark-initiated
pre-chamber combustion system for otherwise standard spark ignition
engines. Combustion in the main chamber is initiated by jets of
partially combusted (reacting) pre-chamber products which provide a
high energy ignition source. The resultant widely distributed
ignition sites allow relatively small flame travel distances
enabling short combustion durations and high burn rates.
Demonstrated benefits include ultra lean operation (λ≻2) at part
load and high load knock improvement.
This study compared the knock limit of conventional spark
ignition and pre-chamber jet ignition combustion with reducing fuel
quality in a modern PFI engine platform. Seven PRF blends ranging
from 93-60 octane were experimentally tested in a stoichiometric
normally aspirated single-cylinder research engine at 1500 rev/min
and ~WOT (98 kPa MAP). The majority of jet ignition experiments
utilized an unfueled pre-chamber (no pre-chamber auxiliary fuel
addition), with results highlighting significant knock limit
extension with this combustion system. At MBT combustion phasing, a
10 octane number improvement was recorded with the unfueled
pre-chamber over conventional spark ignition combustion due to the
burn rate enhancement. At the combustion stability limit (3% CoV
IMEPg) with spark retard, the unfueled pre-chamber jet igniter was
capable of operating on 65 octane fuel, corresponding to a ≻15
octane number benefit due to the increased ignition delay and the
ability to burn the main charge very late and very quickly. This is
estimated to correspond to a base compression ratio increase of ~3
points over conventional spark ignition combustion at the 1500
rev/min test condition, in the same test engine. Additional
experiments were also completed using an auxiliary-fueled
pre-chamber, with the PRF fuel fed into the pre-chamber cavity as
well as the PFI main chamber. Results highlight further burn rate
enhancement when fueling the pre-chamber independently of the main
chamber, with successful WOT engine operation utilizing 60 octane
fuel. Further experiments using standard US 87 (R+M)/2 pump fuel
were completed up to 5500 rev/min and 13 bar IMEPn, with similar
knock limit extensions observed with the pre-chamber jet igniter
when compared to the baseline spark ignition combustion system.