Gasoline compression ignition (GCI) is a low temperature combustion (LTC) concept that lias been gaining increasing interest over the recent years owing to its potential to achieve diesel-like thermal efficiencies with significantly reduced engine-out nitrogen oxides (NOx) and soot emissions compared to diesel engines. In this work, closed-cycle computational fluid dynamics (CFD) simulations are peifarmed o f this combustion mode using a sector mesh in an effort to understand effects o f model settings on simulation results. One goal o f this work is to provide recommendations fo r grid resolution, combus tion model, chemical kinetic mechanism, and turbulence model to accurately capture experimental combustion characteristics. Grid resolutions ranging from 0.7mm to 0.1 mm minimum cell sizes were evaluated in conjunction with both Reynolds averaged Navier-Stokes (RANS) and large eddy simulation (LES) based turbulence models. Solu tion o f chemical kinetics using the multizone approach is evaluated against the detailed approach o f solving chemistry in every cell. The relatively small primary reference fuel (PRF) mechanism (48 species) used in this study is also evaluated against a larger 312-species gasoline mechanism. Based on these studies, the following model settings are chosen keeping in mind both accuracy and computation costs-0.175 mm minimum cell size grid, RANS turbulence model, 48-species PRF mechanism, and multizone chem istry solution with bin limits o f 5 K in temperature and 0.05 in equivalence ratio. With these settings, the performance o f the CFD model is evaluated against experimental results corresponding to a low h a d start o f injection (SOI) timing sweep. The model is then exercised to investigate the effect o f SOI on combustion phasing with constant intake valve closing (IVC) conditions and fueling over a range o f SOI timings to isolate the impact o f SO! on charge preparation and ignition. Simulation results indicate that there is an optimum SOI timing, in this case -3 0 deg aTDC (after top dead center), which results in the most stable combustion. Advancing injection with respect to this point leads to significant fuel mass burning in the colder squish region, leading to retarded phasing and ultimately misfire fo r SOI timings earlier than -4 2 deg aTDC. On the other hand, retarding injection beyond this optimum timing results in reduced residence time avail able fo r gasoline ignition kinetics, and also leads to retarded phasing, with misfire at SOI timings later than -IS d e g a T D C .

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Conventional combustion techniques struggle to meet the current emissions norms. In particular, oxides of nitrogen (NOJ and partieulate matter (PM) emissions have limited the utilization of diesel fuel in compression ignition engines. Advance combustion concepts have proved the potential to combine fuel efficiency and improved emission performance. Low-temperature combustion (LTC) offers reduced NO^ and PM emissions with comparable modern diesel engine efficiencies. The abiliry of premixed, low-temperature compression ignition to deliver low PM atid NO^ emissiotis is dependent on achieving optimal combustion phasing. Diesel operated LTC is limited by early knocking combustion, whereas conventional gasoline operated LTC is limited by misflring. So the concept of using an unconventional fuel with the properties in between those two boundary fuels has been experimented in this paper. Low-octane (84 RON) gasoline has shown comparable diesel efficiencies with the lowest NO^ emissions at reasonable high power densities (NO, emission was I g/kW h at 12 bar BMEP and 2750 rpm).

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