Stephen Ciatti

Bio: Stephen Ciatti is an academic researcher from Argonne National Laboratory. The author has contributed to research in topics: Ignition system & Homogeneous charge compression ignition. The author has an hindex of 14, co-authored 38 publications receiving 649 citations. Previous affiliations of Stephen Ciatti include University of Wisconsin-Madison.

An Experimental Investigation of Low Octane Gasoline in Diesel Engines

Abstract: Conventional combustion techniques struggle to meet the current emissions norms. In particular, oxides of nitrogen (NO{sub x}) and particulate 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{sub x} and PM emissions with comparable modern diesel engine efficiencies. The ability of premixed, low-temperature compression ignition to deliver low PM and NO{sub x} emissions is dependent on achieving optimal combustion phasing. Diesel operated LTC is limited by early knocking combustion, whereas conventional gasoline operated LTC is limited by misfiring. 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{sub x} emissions at reasonable high power densities (NO{sub x} emission was 1 g/kW h at 12 bar BMEP and 2750 rpm).

Computational Fluid Dynamics Simulation of Gasoline Compression Ignition

Abstract: Gasoline compression ignition (GCI) is a low temperature combustion (LTC) concept that has 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 performed of this combustion mode using a sector mesh in an effort to understand effects of model settings on simulation results. One goal of this work is to provide recommendations for grid resolution, combustion model, chemical kinetic mechanism, and turbulence model to accurately capture experimental combustion characteristics. Grid resolutions ranging from 0.7 mm 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. Solution of chemical kinetics using the multizone approach is evaluated against the detailed approach of 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 chemistry solution with bin limits of 5 K in temperature and 0.05 in equivalence ratio. With these settings, the performance of the CFD model is evaluated against experimental results corresponding to a low load start of injection (SOI) timing sweep. The model is then exercised to investigate the effect of SOI on combustion phasing with constant intake valve closing (IVC) conditions and fueling over a range of SOI timings to isolate the impact of SOI on charge preparation and ignition. Simulation results indicate that there is an optimum SOI timing, in this case −30 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 for SOI timings earlier than −42 deg aTDC. On the other hand, retarding injection beyond this optimum timing results in reduced residence time available for gasoline ignition kinetics, and also leads to retarded phasing, with misfire at SOI timings later than −15 deg aTDC.

Hydrogen-fueled internal combustion engines

Abstract: Four types of hydrogen detectors are used by researchers, engineers, and manufacturers today, and if hydrogen continues to play a role in emerging alternative energy sources, there will be exponential growth in the use and need for more advanced and more robust devices in the future. The types of sensors reviewed in this chapter are (1) room-temperature hydrogen leak sensors; (2) thermometers, particularly useful at low temperature; (3) liquid hydrogen volume and mass gauges; and (4) para/ortho hydrogen ratiometers.