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The formation and transport processes governing the build-up of incombustible ash deposits in diesel particulate filters (DPF) are influenced to a large extent by the filter's operating history. More specifically, the regeneration process, whether active, passive, or some variation of the two, has long been assumed to exert significant influence on the resulting ash characteristics. Until recently, only limited circumstantial evidence was available to describe differences in ash properties and distribution impacting DPF performance for filters subjected to different regeneration strategies. This work presents, for the first time, results from a comprehensive series of evaluations with optically-accessible DPF core samples showing the processes controlling the formation, transport, and interaction of the soot and ash deposits over a range of DPF regeneration conditions.

Diesel fuels usually comprise a wide range of compounds having different molecular structures which can affect both the fuel's physical properties and combustion characteristics. In future, as synthetic fuels from fossil and sustainable sources become increasingly available, it could be possible to control the fuel's molecular structure to achieve clean and efficient combustion. This paper presents experimental results of combustion and emissions studies undertaken on a single cylinder diesel engine supplied with 18 different fuels each comprising a single, acyclic, non-oxygenated hydrocarbon molecule. These molecules were chosen to highlight the effect of straight carbon chain length, degree of saturation and the addition of methyl groups as branches to a straight carbon chain.

While metal fiber filters have successfully shown a high degree of particle retention functionality for various sizes of diesel engines with a low pressure drop and a relatively high filtration efficiency, little is known about the effects of lubricant-derived ash on the fiber filter systems. Sintered metal fiber filters (SMF-DPF), when used downstream from a diesel engine, effectively trap and oxidize diesel particulate matter via an electrically heated regeneration process where a specific voltage and current are applied to the sintered alloy fibers. In this manner the filter media essentially acts as a resistive heater to generate temperatures high enough to oxidize the carbonaceous particulate matter, which is typically in excess of 600°C.

Ash accumulation in the channels of ceramic, honeycomb-type particulate filters is controlled by several key parameters, which are the focus of this study. Ultimately, it is the formation of ash deposits, their transport, and the manner in which the ash accumulates in the particulate filter, which determines the useful service life of the filter and its resulting impact on engine performance. Although significant variations in ash deposit properties and their spatial distribution within the filter channels have been reported, depending on the filter's application, understanding the key parameters and mechanisms, such as the effects of exhaust flow and temperature conditions, as well as the processes occurring during filter regeneration events (whether passive or active) are critical in developing improved filter ash management strategies.

Inorganic engine lubricant additives, which have various specific, necessary functions such as anti-wear, leave the combustion chamber bound to soot particles (approximately ≤1% by mass) as ash [13], and accumulate in aftertreatment components. The diesel particulate filter (DPF) is especially susceptible to ash-related issues due to its wall-flow architecture which physically traps most of the soot and ash emissions. Accumulated lubricant-derived ash results in numerous problems including increased filter pressure drop and decreased catalytic functionality. While much progress has been made to understand the macroscopic details and effects of ash accumulation on DPF performance, this study explores the nano- and micron-scale forces which impact particle adhesion and mobility within the particulate filter.

Particulate emissions from a production gasoline direct injection spark ignition engine were studied under a typical cold-fast-idle condition (1200 rpm, 2 bar NIMEP). The particle number (PN) density in the 22 to 365 nm range was measured as a function of the injection timing with single pulse injection and with split injection. Very low PN emissions were observed when injection took place in the mid intake stroke because of the fast fuel evaporation and mixing processes which were facilitated by the high turbulent kinetic energy created by the intake charge motion. Under these conditions, substantial liquid fuel film formation on the combustion chamber surfaces was avoided. PN emissions increased when injection took place in the compression stroke, and increased substantially when the fuel spray hit the piston.

The impact of the operating strategy on emissions from the first combustion cycle during cranking was studied quantitatively in a production gasoline direct injection engine. A single injection early in the compression cycle after IVC gives the best tradeoff between HC, particulate mass (PM) and number (PN) emissions and net indicated effective pressure (NIMEP). Retarding the spark timing, it does not materially affect the HC emissions, but lowers the PM/PN emissions substantially. Increasing the injection pressure (at constant fuel mass) increases the NIMEP but also the PM/PN emissions.

The fuel energy consumption of subsonic air transportation is examined. The focus is on identification and quantification of fundamental engineering design tradeoffs which drive the design of subsonic tube and wing transport aircraft. The sensitivities of energy efficiency to recent and forecast technology developments are also examined.

In gasoline engines, a scraper ring with a step on the bottom outer edge is widely used as a second ring. However, there lacks a fundamental understanding on the effects of this feature and its dimensions on oil transport. Inspired by observations from visualization experiments, this work combining computational fluid dynamics (CFD) and theoretical analysis shows that oil can be trapped in the space bordered by a second ring step and the chamfer of a piston third land. The trapped oil can be released to a liner when the piston is approaching the top dead center (TDC). This additional oil on the liner becomes a potential source of oil consumption. Such oil transport has been observed at typically less than 1500rpm. Since road vehicles often operate in this speed range, the newly-observed oil trapping and release can be closely associated with oil consumption in gasoline engines. In this work, a comprehensive study on oil trapping and release will be demonstrated.

The Engine-Out Particulate Matter (EOPM) was collected from a spark ignition engine operating in steady state using a heated quartz fiber filter. The samples were weighted to obtain an EOPMindex and were analyzed using Scanning Electron Microscopy. The EOP Mindex was not sensitive to the engine rpm and load. When the mixture is very rich (air equivalence ratio λ less than ∼ 0.7), the EOPM comprise mostly of soot particles from fuel combustion. In the lean to slightly rich region (0.8 < λ < 1.2), however, the EOPM are dominated by particles derived from the lubrication oil.

A dynamometer-mounted four-cylinder Saturn engine was used to accumulate combustion chamber deposits (CCD), using an additized fuel. During each deposit accumulation test, the HC emissions were continuously measured. The deposit thickness at the center of the piston was measured at the beginning of each day. After the 50 and 35-hour tests, HC emissions were measured with isooctane, benzene, toluene, and xylene, with the deposited engine, and again after the deposits had been cleaned from the engine. The HC emissions showed a rapid rise in the first 10 to 15 hours and stabilization after about 25 hours of deposit accumulation. The HC increase due to CCD accumulation accounted for 10 to 20% of the total engine-out HC emissions from the deposit build-up fuel and 10 to 30% from benzene, isooctane, toluene, and xylene, making CCDs a significant HC emissions source from this engine. The HC emissions stabilized long before the deposit thickness.

A research program designed to measure the contribution from fuel absorption in the thin layer of oil, lubricating the cylinder liner, to the total and speciated HC emissions from a spark ignition engine has been performed. The logic of the experiment design was to test the oil layer mechanism via variations in the oil layer thickness (through the lubricant formulations), solubility of the fuel components in the lubricants, and variations in the crankcase gas phase HC concentration (through crankcase purging). A set of preliminary experiments were carried out to determine the solubility and diffusivity of the fuel components in the individual lubricants. Engine tests showed similar HC emissions among the tested lubricants. No consistent increase was observed with oil viscosity (oil film thickness), contrary to what would be expected if fuel-oil absorption was contributing significantly to engine-out HC. Similarly, no effect of crankcase purging could be observed.

A gasoline engine with an electronically controlled fuel injection system has substantially better fuel economy and lower emissions than a carburetted engine. In general, the stability of engine operation is improved with fuel injector, but the stability of engine operation at idle is not improved compared with a carburetted gasoline engine. In addition, the increase in time that an engine is at idle due to traffic congestion has an effect on the engine stability and vehicle reliability. Therefore, in this research, we will study the influence of fuel injection timing, spark timing, dwell angle, and air-fuel ratio on engine stability at idle.

The windage tray effect on aeration in the engine sump was assessed by replacing much of the windage tray materials with wire meshes of various blockages. The mesh was to prevent direct impact of the oil drops spinning off the crank shaft onto the sump oil, and simultaneously, to provide sufficient drainage so that there was no significant build up of windage tray oil film that would interact with these droplets. Aeration at the oil pump inlet was measured by X-ray absorption in a production V-6 SI engine motoring at 2000 to 6000 rpm. Within experimental uncertainty, these windage tray changes had no effect on aeration. Thus activities in the sump such as the interaction of the oil drops spun from the crank shaft with the sump oil or with the windage tray, and the agitation of the sump oil by the crank case gas, were not major contributors to aeration at the pump inlet.

Synthetic bio-fuels, which can be obtained through the gasification of biomass into synthesis gas and the subsequent catalytic reaction of the synthesis gas into liquid fuel molecules, could play a key-role in providing a sustainable source of automotive fuels during the coming decades. This paper presents an attempt to understand the effect of molecular structure of potential oxygenated synthetic bio-fuel molecules of different structure on the diesel combustion process in both stratified and homogeneous combustion modes. Specifically, the effects of molecular structure on the energy release rates, gaseous exhaust emissions and the sub-micron particulate matter distribution were examined. The experiments were carried out on a single-cylinder direct-injection diesel engine using a specially adapted common-rail fuel-system which allowed the injection of small single-molecule fuel samples at high pressure.

The characteristics of the early development of fuel sprays from pressure swirl atomizer injectors of the type used in direct injection gasoline engines is investigated. Planar laser-induced fluorescence (PLIF) was used to visualize the fuel distribution inside a firing optical engine. The early spray development of three different injectors at three different fuel pressures (3, 5, and 7 MPa) was followed as a function of time in 30 μsec intervals. Four phases could be identified: 1) A delay phase between the rising edge of the injection pulse and the first occurrence of fuel in the combustion chamber, 2) A solid jet or pre-spray phase, in which a poorly atomized stream of liquid fuel during the first 150 μsec of the injection. 3) A wide hollow cone phase, separation of the liquid jet into a hollow cone spray once sufficient tangential velocity has been established and 4) A fully developed spray, in which the spray cone angle is narrowed due to a low pressure zone at the center.

To address the growing need for detailed chemistry in engine simulations, new software tools and validated data sets are being developed under an industry-funded consortium involving members from the automotive and fuels industry. The results described here include systematic comparison and validation of detailed chemistry models using a wide range of fundamental experimental data, and the development of software tools that support the use of detailed mechanisms in engineering simulations. Such tools include the automated reduction of reaction mechanisms for targeted simulation conditions. Selected results are presented and discussed.

The impact of market-fuel variations on the HCCI operating range was measured in a 2.3L four-cylinder engine, modified for single-cylinder operation. HCCI combustion was achieved through the use of residual trapping. Variable cam phasing was used to maximize the load range at each speed. Test fuels were blended to cover the range of variation in select commercial fuel properties. Within experimental measurement error, there was no change in the low-load limit among the test fuels. At the high-load limit, some small fuel effects on the operating range were observed; however, the observed trends were not consistent across all the speeds studied.

This paper reviews the relevant literature on the effects of sulfated ash, phosphorus, and sulfur on DPF, LNT, and SCR catalysts. Exhaust backpressure increase due to DPF ash accumulation, as well as the rate at which ash is consumed from the sump, were the most studied lubricant-derived DPF effects. Based on several studies, a doubling of backpressure can be estimated to occur within 270,000 to 490,000 km when using a 1.0% sulfated ash oil. Postmortem DPF analysis and exhaust gas measurements revealed that approximately 35% to 65% less ash was lost from the sump than was expected based on bulk oil consumption estimates. Despite significant effects from lubricant sulfur and phosphorus, loss of LNT NOX reduction efficiency is dominated by fuel sulfur effects. Phosphorus has been determined to have a mild poisoning effect on SCR catalysts. The extent of the effect that lubricant phosphorus and sulfur have on DOCs remains unclear, however, it appears to be minor.

We present results which verify the design parameters and suggest performance capabilities/limitations of the Mars Gravity Biosatellite's proposed atmospherics control subassembly. Using a combination of benchtop prototype testing and analytic techniques, we derive control requirements for ammonia. Further, we demonstrate the dehumidification performance of our proposed partial gravity condensing heat exchanger. Ammonia production is of particular concern in rodent habitats. The contaminant is released following chemical degradation of liquid waste products. The rate of production is linked to humidity levels and to the design of habitat modules in terms of bedding substrate, air flow rates, choice of structural materials, and other complex factors. Ammonia buildup can rapidly lead to rodent health concerns and can negatively impact scientific return.