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Gasoline direct injection (GDI) engines usually emit higher levels of particulates in warm-up conditions of a driving cycle. Thus, sources of soot formation in these conditions were investigated by measuring particulate numbers (PN) emitted from a single-cylinder GDI engine and their sizes. The combustion was also visualized using an endoscope connected to a high-speed camera. Engine coolant and oil temperatures were varied between 15 and 90oC to mimic warm-up conditions. In addition, effects of delaying the start of ignition (SOI) on the emissions in these conditions were examined. Coolant and oil temperatures were varied individually to identify which factor has most effect on PN emissions. While coolant temperature strongly influenced PN with cold oil, the oil temperature insignificantly affected PN at low coolant temperature. These findings indicate that PN emissions are heavily dependent on the engine block’s temperature, which is dominated by the coolant.

An analysis of the soot formation and oxidation process in a conventional direct-injection (DI) diesel flame was conducted using numerical simulations. An improved multi-step phenomenological soot model that includes particle inception, particle coagulation, surface growth and oxidation was used to describe the soot formation and oxidation process. The soot model has been implemented into the KIVA-3V code. Other model Improvements include a piston-ring crevice model, a KH/RT spray breakup model, a droplet wall impingement model, a wall-temperature heat transfer model, and the RNG k-ε turbulence model. The Shell model was used to simulate the ignition process, and a laminar-and-turbulent characteristic time combustion model was used for the post-ignition combustion process. Experimental data from a heavy-duty, Cummins N14, research DI diesel engine operated with conventional injection under low-load conditions were selected as a benchmark.

In order to study the soot formation and oxidation phenomena during the combustion process of Gasoline Direct Injection (GDI) engines, soot volume fraction measurements were performed in an optical GDI engine by combined Laser-Induced Incandescence (LII) and Laser Extinction Method (LEM). The coupling of these two diagnostics takes advantages of their complementary characteristics. LII provides a two-dimensional image of the soot distribution while LEM is used to calibrate the LII image in order to obtain soot volume fraction fields. The LII diagnostic was performed through a quartz cylinder liner in order to obtain a vertical plane of soot concentration distribution. LEM was simultaneously performed along a line of sight that was coplanar with the LII plane, in order to carry out quantitative measurements of path-length-averaged soot volume fraction. The LII images were calibrated along the same path as that of the LEM measurement.

Future fuels will come from a variety of feed stocks and refinement processes. Understanding the fundamentals of combustion and pollutants formation of these fuels will help clear hurdles in developing flex-fuel combustors. To this end, we investigated the combustion, soot formation, and soot oxidation processes for various classes of fuels, each with distinct physical properties and molecular structures. The fuels considered include: conventional No. 2 diesel (D2), low-aromatics jet fuel (JC), world-average jet fuel (JW), Fischer-Tropsch synthetic fuel (JS), coal-derived fuel (JP), and a two-component surrogate fuel (SR). Fuel sprays were injected into high-temperature, high-pressure ambient conditions that were representative of a practical diesel engine. Simultaneous laser extinction measurement and planar laser-induced incandescence imaging were performed to derive the in-situ soot volume fraction.

The accumulation of soot and lubrication-derived ash particles in a diesel particulate filter (DPF) increases exhaust flow restriction and negatively impacts engine efficiency. Previous studies have described the macroscopic phenomenon and general effects of soot and ash accumulation on filter pressure drop. In order to enhance the fundamental understanding, this study utilized a novel apparatus that of a dual beam scanning electron microscope (SEM) and focused ion beam (FIB), to investigate microscopic details of soot and ash accumulation in the DPF. Specifically, FIB provides a minimally invasive technique to analyze the interactions between the soot, ash, catalyst/washcoat, and DPF substrate with a high degree of measurement resolution. The FIB utilizes a gallium liquid metal ion source which produces Ga+ ions of sufficient momentum to directionally mill away material from the soot, ash, and substrate layers on a nm-μm scale.

Soot and fuel distributions have been studied in an optically accessible direct-injection diesel engine of the “heavy-duty” size class. Laser-induced incandescence (LII) was used to study the effects of changes in the engine speed on the in-cylinder soot distribution, and elastic (Mie) scattering and laser-induced fluorescence (LIF) were used to examine the fuel distribution. The investigation showed that, in this engine, soot is distributed throughout the cross section of the combusting region of the fuel jet for engine speeds ranging from 600 to 1800 rpm. No indication was found that soot occurs preferentially around the periphery of the plume. The LII images showed that the soot concentration decreases with increasing engine speed and injection pressure, and that the soot distribution extends much further upstream (toward the injector) at the lower engine speeds than at higher speeds.

Significant effort has been put toward developing future-generation biofuels aimed at either spark-ignition or compression-ignition engines. Butyl-Acetate (BA), C6H12O2, is one such fuel that may be viable as a soot reduction drop-in blend candidate without significant impact on performance or efficiency. Though BA does have a low CN (≈ 20) and heating value (27 MJ/kg), it offers promise as a drop in blend-candidate with pump diesel due to its improved cold weather performance, high flash point, and potential for high volume renewable production capacity. This work investigated the impacts of 5% by volume blend of BA and standard pump diesel (DF2) on overall performance and with a particular focus on soot behavior. Tests were completed at 13 operating points spanning the operating map including full power. Results show a significant reduction in soot without significant impact on NOx emissions and minimal impact on thermal efficiency.

To this day, Diesel engines with direct injection are the most efficient internal combustion engines for passenger cars. The major challenge of these engines with a conventional Diesel combustion process is the high level of particulate matter and nitrogen oxide emissions. Diesel engines in passenger cars normally use a pilot injection strategy for NVH reasons, which influences the engine-out soot emissions negatively. The Diesel fuel of the pilot injection is still burning when the main injection takes place, so, liquid components of the main injection interact with the flame of the pilot injection. The time for mixture formation decreases and the combustion takes place under locally very rich conditions which results in high levels of soot formation. For this reason new emission level restrictions cannot be reached without modern exhaust gas aftertreatment systems, which are quite expensive and can have an impact on the gas exchange.

Particulate matter emissions are becoming a big issue for GDI engines as the emission regulations being more stringent. Methanol has been considered to be an important alternative fuel to reduce soot emissions. To understand the effect of methanol addition on soot and polycyclic aromatic hydrocarbons (PAHs) formation, the 2-D distributions of soot volume fraction and different size PAHs relative concentrations in methanol/gasoline laminar diffusion flames were measured by TC-LII and PLIF techniques. The effect of methanol was investigated under the conditions of the same carbon flow and the same flame height. The methanol volume fraction was set as M0/20/40/60/80. The results showed that the natural luminescent flame lift-off height and soot lift-off height increases consistently with the increasing methanol content due to the increase of outlet velocity of fuel vapor.

The effect of the use of the EGR system on the lubrication of a passenger car diesel engine was investigated. The higher the EGR rate, the more soot in the oil. And the most detrimental effect was found in valve train wear. Some engine tests, including motoring tests, were carried out to investigate the contribution of soot to valve train wear. The mechanism of cam and rocker arm wear in used oils was studied by analyzing for elements on the lubricated metal surface and subsequently the mechanism was more thoroughly studied using the four-ball test. Soot seems to act as an abrasive on the anti-wear solid film formed by the oil on the metal surface and this film contains Ca, O, P and S. Some hardware modifications and oil formulations to reduce valve train wear are also discussed.

Many researchers [1,2,3,4] have suggested that lubricants contaminated with soot result in increased rates of wear. Numerous potential mechanisms have been proposed which include abrasion via three body contact, oil starvation and deactivation of the anti-wear additives. It is commonly thought that the control of soot aggregation by the addition of appropriate dispersant additives will lead to improved wear performance [5]. In this paper, the kinematic behaviour of two valve train contacts are studied and a generalised wear model proposed that highlights the importance of oil film thickness, soot particle size and contact mechanics. The results of these analyses when considered alongside the detailed rheological behaviour of the soot laden oil lead us to challenge the significance of soot aggregation and viscosity control to engine wear.

Among the key technologies currently being used for reducing NOx emissions to achieve the target of pollutant emissions (Euro V), Exhaust Gas Recirculation (EGR) has been developed for its effectiveness and its attractive cost for car diesel engines. However, with EGR, more particle matter is emitted from engines. The presence of higher levels of soot in the oil has led to an increase in kinetic lubricant viscosity which in turn could cause lubrication problems and lead to increased wear of engine parts such as cylinder liners, piston rings, valve train systems and bearings, as well as reducing oil drain intervals. SOGEFI developed a specific method to remove soot from oil and has designed a new laboratory test to use several possible configurations and to evaluate the reduction of soot level is described. Characteristics for measuring soot levels and the size of particles are also presented.

Soot formation from heavy hydrocarbons (n-hexadecane, decahydronaphtalene, N-heptylbenzene and 1-methyl-naphtalene) was studied behind reflected shock waves, using a light extinction technique. The highly diluted mixtures (99 to 99.8% of argon) were heated between 1300 and 2700 K. The pressure ranged from 650 to 1800 kPa. Soot induction delay times, growth rates and yields, were determined under pyrolysis and for two equivalence ratios (5 and 18). The effect of aromaticity, oxygen content, temperature and pressure on these parameters were investigated. Samples of soot particles formed behind shock waves and collected after experiments have been analyzed by transmission electron microscopy for a magnification of 5x10 4 in order to determine the size of elementary spheres. This parameter was studied in relation with the experimental conditions.

Four kinds of optical measurements were performed to investigate the process of soot formation and oxidation in a direct-injection (DI) diesel engine. Measurements were carried out in an optically accessible DI diesel engine that allows planar laser sheet for combustion diagnostics to enter the combustion chamber either horizontally or along the axis of the fuel jet. The temporal and spatial distribution of soot particles has been investigated using the laser- induced incandescence (LII) and high-speed direct photography. Fuel vapor concentration, which is directly linked to the soot formation process in diesel combustion, has been deduced from the images obtained by the measurements of laser shadowgraph and elastic Mie scattering. According to the experimental results, soot formation begins to occur near the injector nozzle in which a fuel-rich mixture is distributed with a homogeneous condition. LII signal is dominated by the fuel vapor concentration in initial combustion period.

Formation of soot is a known phenomenon for diesel engines, however, only recently emerged for gasoline engines with the introduction of direct injection systems. Soot-in-oil samples from a three-cylinder turbocharged gasoline direct injection (GDI) engine have been analysed. The samples were collected from the oil sump after periods of use in predominantly urban driving conditions with start-stop mode activated. Thermogravimetric analysis (TGA) was performed to measure the soot content in the drained oils. Soot deposition rates were similar to previously reported rates for diesel engines, i.e. 1 wt% per 15,000 km, thus indicating a similar importance. Morphology was assessed by transmission electron microscopy (TEM). Images showed fractal agglomerates comprising multiple primary particles with characteristic core-shell nanostructure. Furthermore, large amorphous structures were observed. Primary particle sizes ranged from 12 to 55 nm, with a mean diameter of 30 nm and mode at 31 nm.

Changing diesel engine emission requirements for 2002 have led many diesel engine manufacturers to incorporate cooled Exhaust Gas Recirculation, EGR, as a means of reducing NOx. This has resulted in higher levels of soot being present in used oils. This paper builds on earlier work with fresh oils and describes a study of the effect of highly sooted oils on the low temperature pumpability in diesel engines. Four experimental diesel engine oils, of varying MRV TP-1 viscosities, were run in a Mack T-8 engine to obtain a soot level ranging between 6.1 and 6.6%. These sooted oils were then run in a Cummins M11 engine installed in a low temperature cell. Times to lubricate critical engine components were measured at temperatures ranging between -10 °C and -25 °C. A clear correlation was established between the MRV TP-1 viscosity of a sooted oil and the time needed to lubricate critical engine components at a given test temperature.

Particulate emissions are reported for a 0.31 L single cylinder engine fitted with an air forced direct injection system. Trends in number, size, and mass of engine out particle emissions are examined as a function of injection timing, spark timing, and EGR. Injection timing determines to a large degree the nature of the combustion, with early injection leading to homogeneous like combustion and late injection producing stratified charge combustion. As fuel injection is retarded, at a fixed lean air to fuel ratio, PM emissions decline to a minimum at an injection time well within the compression stroke, after which they rapidly increase. In the heavily stratified regime, the PM increase can be attributed to a growing number of rich zones that occur in the progressively more inhomogeneous fuel mixture. At fixed injection timing, advancing the spark causes a general increase in particle emissions.

Diesel engine oil soots from different engines have the appearance of carbon black but contain significant concentrations of engine oil additive elements. Evaluation of the soots in 4-ball wear tests supported the theory that the soots reduce the antiwear additive effectiveness by preferentially adsorbing the active antiwear additive components before they can form the essential antiwear surface coating rather than removing the surface coatings by abrasion after they are formed. Engine load and exhaust gas recirculation have large effects on the soot prowear characteristics, whereas engine refinements, engine make and oil type have lesser effects. No antiwear additives were found more effective than the currently used zinc dialkyl-dithiophosphates. Several preferential adsorber additives were effective in simple blends but not in fully formulated engine oils.

Initially, scientific investigators developed their own human simulators for use in adverse environment testing. This paper describes some of the history of the development of different types of human simulation techniques and their limitations. The increased necessity for more accurate simulations for automotive safety studies has created a need for additional sophistication. Sophisticated Sam, created by Sierra Engineering Co. under the sponsorship of the General Motors Corp., represents a significant advance in the state-of-the-art. The rationale behind the creation of a working simulator is presented along with proposed performance criteria.