A novel combustion process has been developed utilizing
supercritical gasoline injection-ignition for light-duty
compression ignition engines known as Transonic Combustion or
TSCi™. Previous publications have demonstrated results for
improving fuel economy and emissions under light-load operating
conditions typical of those for passenger car vehicles.
The TSCi™ combustion process exhibits similarities with HCCI,
LTC, PCCI and RCCI with high indicated thermal efficiencies
(greater than 45%) and simultaneous reduction of NOx and PM at high
EGR levels. The use of EGR at low and medium loads has shown a
strong impact on NOx without compromising particulate emissions.
However at higher loads with HCCI, LTC, PCCI and RCCI the operating
range is limited by excessive pressure rise rates and control of
combustion phasing, whereas the TSCi™ combustion process, due to
its partially premixed and partially stratified mixture
preparation, is not limited in the same manner. For the TSCi™
process the use of copious EGR levels have demonstrated to be
effective in reducing NOx and cylinder pressure rise rates while
maintaining start of combustion control and low soot emissions at
light load conditions.
The test results presented in this paper are from extensive
single-cylinder engine studies. The results demonstrate the
operating range capability of the TSCi™ process at low load
without EGR, medium load with use of EGR, and high speed low load
with EGR. The results further the technical understanding of the
performance of the TSCi™ process into operating regions
previously unattained. The impact on thermal efficiency, NOx, PM,
hydrocarbons (HC), and carbon monoxide (CO), as well as the ability
to control pressure rise rates, combustion stability, combustion
duration and ignition delay will be presented. The impact of SOI,
Boost, fuel temperature and intake temperature on the supercritical
combustion process are also reported.