Search Results

The understanding of deactivation mechanisms is critical to the development of NOx adsorber catalysts with improved durability. The thermal deactivation of a state-of-the-art Pt/Rh based NOx adsorber catalyst is evaluated following oven agings at 800 and 900°C. Sulfur poisoning during lean/rich cycling is studied as a function of catalyst inlet temperature and SO2 concentration. Complementing these studies utilizing synthetic exhaust gas compositions, deactivation resulting from three different engine aging schedules is examined. The performance of engine-aged catalysts is evaluated as received, and following desulfurization procedures differing in inlet temperature and air/fuel ratio. The impact of aging schedules on NOx adsorption and three-way catalyst function is discussed with respect to precious metal dispersion, washcoat sintering, as well as sulfur build-up and oil-derived poisonings.

Legislation world-wide has made it necessary to find ways to control the level of engine emissions and reduce the damage to our environment. Increasing restrictions have made the elimination of zinc dithiophosphates from crankcase oils and increasing the effectiveness of catalytic converters viable options. Lead and phosphorus containing compounds in the exhaust are known catalyst poisons that shorten the life of current automotive catalysts. Unleaded fuel has successfully resulted in a reduction of harmful emissions due to the fuel. Current government and industry research is actively pursuing replacement of phosphorus additives with phosphorus free additives. Several phosphorus-free oils were developed and are evaluated in bench tests in this study. Test comparisons with phosphorus- containing oils demonstrated satisfactory oxidation stability and wear performance of the phosphorus free oils.

A radioactive tracer method was used to measure the contribution of engine oil to deposits on exhaust system components and particulates in the exhaust gas of a gasoline engine. The technique involves the use of an oil molecule labeled with radioactive 14C. By measuring the 14C concentration in engine deposits, the fraction of carbon derived from the lubricating oil can be determined. Results show that depending on the location of the deposit, oil contributes from 1 to 8% of the carbon deposited, and is independent of engine operating conditions. Oil contribution to particulate filtered from the exhaust gas ranges from 2 to 30% of the carbon, which increases in proportion to engine speed.

In this study the effect of spray characteristics such as spray penetration, spray cone angle and Sauter Mean Radius have been shown to influence fuel vapor distribution, vapor mixing in air and combustion chamber gas turbulence. The effect can be seen in the combustion results, i.e. cylinder pressure, heat release, cumulative heat release, fuel vapor concentration, soot and NOx-formation. In KIVA2-CFD code the Magnussen EDC ( Eddy Dissipation Concept ) model were used for the fuel vapor and soot particles combustion, the Tesner & Magnussen model for the soot formation and the extended Zeldovich model for the NO-formation. Mainly the modified TAB-model or alternatively χ-squared droplet distribution method (DDM) were used for the spray. The TAB-model constants and the initial SMR in the DDM-model were varied logically in order to obtain different kinds of spray characteristics and accordingly different spray behavior in combustion and non-combustion cases.

Changes in the performance requirements of passenger car (PCEO) and heavy duty (HDEO) engine oils are dra-matically impacting the design of tomorrow's automotive lubricants. Specifically, lubricant base oils are shifting toward higher quality API Group II+ (100 - 120 VI) and Group III versus more traditional API Group I and Group II. A feature of premium base oils is high Viscosity Index (VI). Since base oil VI is linked to volatility at a particular kinematic viscosity (KV), higher VI reduces base oil and finished oil volatility. This is key for ILSAC GF-3 PCEO requirements where significant volatility reduction is required to reduce oil consumption. High base oil VI also allows for higher base oil KV and reduced viscosity modifier (VM) treat which improves shear stability of finished fluid. This also provides opportunities to formulate PCEO against the European engine oil requirements where volatility and shear stability are key performance requirements.

The combustion process of a heavy-duty DI-Diesel truck engine has been investigated using numerical simulation. The numerical modeling was based on an improved version of the KIVA-2 engine simulation code, employing a modified characteristic time-scale combustion model and a modified Kelvin-Helmholtz spray atomization model. The NO-formation process was modeled using the extended thermal Zeldovich mechanism. The simulation efforts included the effects of different injection characteristics such as varying the injection rate profile or number of injection holes and sizes. The physical sub-models used to improve the simulation of the mixture-formation and the combustion process were validated through comparison with single-cylinder engine experiments. Special attention was given to accurately model the in-cylinder flame propagation of the individual sprays and their effect on thermal NO-formation. All simulations were based on full load cases at medium speed.

Various single and split injection schemes are studied to provide a better understanding of fuel distribution during cold starting in DI diesel engines. Improved spray-wall interaction, fuel film and multicomponent vaporization models are used to analyze the combustion processes. Better combustion characteristics are obtained for the split injection schemes than with a single injection. An analysis of the fuel impingement processes identifies the mechanisms involved in producing the differences in vaporization and combustion of the fuel. A greater amount of splashing occurred for the split injections compared to a single injection. This behavior is attributed to the decreased film thickness (less dissipation of impingement energy), the decreased impingement area (obtained by increasing the impingement Weber number), and most importantly, the reduced frequency of drop impingement.

A flame sheet model for NO production in multi-dimensional diesel simulation has been developed. It explicitly addresses that because of the finite computational cell resolution, the local temperature within the diffusion flame is substantially higher than the cell averaged temperatures. Thus using the latter values will under-predict NO production. The methodology uses a flame sheet library for the NO production. Computations using this model are compared to experimental data for a Cummins N14 engine. The results show that the NO production is predominantly from within the flame sheets; the bulk production accounts for less than 5% of the total production.

FTP emissions tests on a passenger vehicle equipped with a 1.8 L IDI turbo-charged diesel engine show that the mass emissions of particles decrease by (36±8)% when 16.6% dimethoxymethane (DMM) by volume is added to a diesel fuel. Particle size measurements reveal log-normal accumulation mode distributions with number weighted geometric mean diameters in the 80 - 100 nm range. The number density is comparable for both base fuel and the DMM/diesel blend; however, the distributions shift to smaller particle diameter for the blend. This shift to smaller size is consistent with the observed reduction in particulate mass. No change is observed in NOx emissions. Formaldehyde emissions increase by (50±25)%, while emissions of other hydrocarbons are unchanged to within the estimated experimental error.

The flow-field of an automotive DI Diesel engine is characterized by experiments in a motored engine using Laser Doppler Velocimetry and by CFD simulations. Only one cylinder is active and a specific swirling intake duct is used. Various bowls with different shapes are investigated: fiat or W-shaped bowls, with or without re-entrant. The influence of engine speed is also studied. The mean velocity and turbulence evolutions are measured with back-scatter LDV experiments using an optical access in an extended piston. The simulations are performed using the KMB code, a modified version of KIVA-II. Along with the detailed flow-field description, integral quantities characterizing the flow are derived. The comparison between LDV data and CFD results is shown to be satisfactory. The effects of geometry and engine speed on spatial profiles and temporal evolution of mean and turbulent velocities are correctly reproduced.

The majority of low sulphur automotive diesel fuels marketed today are treated with an additive to enhance the lubricity of the base fuel. Field experience has shown that in order to achieve the full benefits of the low sulphur diesel fuel, the lubricity additive must not only provide sufficient lubricity performance to protect sensitive diesel fuel pumps, but must have no undesirable side effects. These potential side effects include: 1) Degrading the properties of the base fuel, 2) Interacting with crankcase lubricating oils, 3) Reducing the performance benefits of other fuel additives The oil and additive industries have developed a wide range of tests to evaluate the no-harm performance of lubricity additive packages and components. This paper describes many of these tests, with respect to their use in the development of a novel, lubricity additive package for City Diesel Fuel.

The diesel engine in the past few years has improved its market sharing because the new engine technology has reduced the emissions and the diesel engine has relatively cheaper power cost. Nevertheless, in order to meet more restricted emission standards, the NOx, CO, HC, and particulate emissions must be further reduced. Thus, this study will explore the possible fuel additive technology to further reduce the emissions from the diesel engine. In this study the fuel additives EHN, DTBP, MTBE, DMC, Diglyme, Monoglyme, and Ethanol are added into the diesel fuel with two different dosages. These additives are classified into four categories. It is well believed that the fuel cetane number improver such as DTBP (di-t-butyl peroxide) or EHN (2-ethylhexyl nitrate) can increase the fuel cetane number and thus reduce the emission level.

A joint program was undertaken to evaluate the use of Middle Distillate Flow Improvers (MDFIs) in diesel fuel to ambient temperatures as low as -40°C. The objectives of the program were to (i) study MDFI effectiveness at preventing fuel filter blockage due to excessive wax formation at temperatures below -30°C, and (ii) determine the effectiveness of Low Temperature Filterability Test (LTFT) laboratory procedure in protecting vehicles these extremely low temperatures. A total of seven fuels were blended (including 4 treated with MDFI additive) and subsequently tested in three heavy duty trucks in an all weather climate controlled chassis dynamometer facility. Overnight soak temperatures were as low as -40°C. Two of the trucks were equipped with an engine that was known to be critical for fuel filter plugging due to excessive wax formation. A total of 14 valid vehicle tests were run over a six-day period.

Many marketers of branded diesel fuels are introducing a “premium” diesel fuel grade. The National Conference on Weights and Measures is recommending that one of the criteria for marketing a fuel as “premium” is that it have a lower cloud point or alternatively a reduced low temperature flow test (LTFT) failure point [1]. However, waxy crudes and process limitations make it difficult for refiners to economically make very low cloud point diesel fuel. Fortunately, cloud point depressants (CPDs) can overcome these limitations. However, refiners are concerned about the effect cloud point additives have on other diesel fuel properties. We found that cloud point depressants allow refiners to meet low temperature specifications while being neutral or beneficial to other diesel fuel properties.

A study has been made of the lubricant film-forming properties of viscosity index improver-containing oils in non-steady state, high-pressure contacts. Two types of non-steady speed condition have been investigated, sudden halting of motion and cyclically-varying entrainment speed. Film thickness has been measured in a ball on flat contact using ultra-thin film interferometry. It has been shown that viscosity index improver polymers in solution exhibit an enhanced squeeze behavior during halting and a viscoelastic response to acceleration/deceleration.

The purpose of this study was to examine the cause of fluctuations in combustion. It is important to understand the changes that occur in flame kernel development and in flame propagation during cyclic variation. In this study, a comparison was made between time-series variations in OH emission with THC concentration, and the intensity of the combustion reaction and the direction of flame propagation are also discussed. Early flame development and cyclic variation at an early stage of combustion were demonstrated by simultaneously measuring a two-dimensional image of flame emission and the time-series variation of local flame emission. The instantaneous intensity at Cassegrain measurement point agreed with the intensity of time-series variation in local flame propagation at CCD recorded timing. Variations in THC concentration in the cylinder were compared with time-series variations in local flame emission.

This paper describes measurements of oil film thickness of piston ring packages which have different oil control rings. The oil film thickness measurements were taken at three points, namely, the piston thrust side, front side and rear side, by the Laser Induced Fluorescence Method(LIF). One of the main findings is that the oil film thickness on the thrust side varies greatly from cycle to cycle, while cyclic variations are smaller on the front and rear sides. This difference is due to the smaller inclination of the oil control rings on the front and rear sides, compared with that on the thrust side. It is also found that oil consumption has a good correlation with oil film thickness on the thrust side and that the thrust side oil film thickness becomes thinner as the oil ring becomes narrower.

In this study, a piezo disk was used to generate a cloud of n-decane fuel drops, which were mixed with air, then carried into a combustion chamber and ignited by a platinum wire. Microgravity data obtained at the Japan Microgravity Center (JAMIC) were compared to normal gravity data, all at 1Atm pressure and 20+/-1°C initial temperature. Under normal gravity the lean limit was found to be 7.6x106/mm3 (Φ = 1.0), and from this point the flame front speed steadily increased from 20cm/s up to a maximum flame front speed of 210cm/s at a fuel drop density of about 14x106/mm3 (Φ = 1.85). Microgravity data showed a much richer lean limit - about 14.5x106/mm3 (Φ = 1.9), and the flame front speed did not gradually rise to a peak value. Instead, the measurements indicated a peak value of about 250cm/s, with a steep increase followed by a gradual decrease at richer fuel air ratios. A cellular flame structure appeared, and the cell size decreased as the mixture density increased.

In plasma jet ignition, combustion enhancement effects are caused toward the plasma jet issuing direction. Therefore, when the igniter is attached at the center of cylindrically shaped combustion chamber, the plasma jet should issues toward the round combustion chamber wall. The plasma jet igniter that had a concentric circular orifice has been developed. It is expected that the plasma jet is issued and is diffused from concentric circular orifice toward the combustion chamber wall. Relationship between plasma jet and igniter configuration was experimentally clarified. Plasma jet can issue from the entire concentric circular orifice for some igniter. Plasma jet is extended with increasing concentric circular orifice area. Plasma jet penetration increases with increasing concentric circular orifice width.

The introduction around the world of low sulphur diesel fuel has required extensive use of lubricity additive technology in some markets. At the same time, the use of performance diesel additives such as detergents and defoamers is becoming more widespread. The wider application of performance diesel additives demands the introduction of proven technologies in new markets, whilst new requirements are met with a combination of existing and new additive technologies. Such developments are not without risk. These new applications could generate a variety of field problems and extensive testing is necessary to prove that the use in a new environment is trouble-free. This paper illustrates how diesel fuel additives can be efficient in solving specific problems and, at the same time, can generate a host of new problems such as plugging of fuel filters, in-line diesel pump failures, increased level of engine bore polish and deactivation of other performance diesel additives.