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 limit extension.
Previous jet ignition experimental results have highlighted high
thermal efficiencies, high load capability and near-zero engine-out
NOx emissions in a standard contemporary engine platform. Although
previous results of this system have been very promising, the main
hurdle has been the need for a dual fuel system, with liquid
gasoline used in the main combustion chamber and small fractions of
gaseous propane in the pre-chamber. Initial attempts in replacing
the pre-chamber gaseous propane with liquid gasoline were
problematic, although engine operation was successful at some
operating conditions. The poor mixture preparation with liquid
gasoline inside the small pre-chamber cavity due to the limited
production injector hardware somewhat compromised the thermal
efficiency, resulting in slight elevations in NOx emissions. Since
specialized pre-chamber injector hardware was not available for
evaluation, the purpose of this paper is to demonstrate that this
combustion system can operate robustly using gasoline, with
vaporized gasoline found to be a successful pre-chamber fuel
substitute. With this concept at part load, the test engine
recorded a 41.4% peak thermal efficiency, ultra lean operation past
lambda 2.1, single-digit engine-out NOx emissions and a 20% peak
fuel economy improvement over the baseline spark ignition
system.