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The schlieren method is a powerful and widely used technique for studying ignition and combustion. Jointly with high-speed photography, this method is often used in both SI- and CI-engines and combustion bombs, including rapid compression machines (rcm). This paper describes tests carried out on a new hydraulically actuated dynamic combustion rig, using schlieren visualisation in two orthogonal directions. The working principle of the rig is briefly described. Results are presented on ignition properties of low quality gas blends using spark ignition and pilot flame. Methane, ethane and nitrogen were blended at different air-fuel ratios and tested as to ignition and early flame development. For spark ignition tests, the pair of images from the two orthogonal directions enables the use of digital image processing to calculate the flame speed, and to compose a three-dimensional volumetric image of the flame front shape.

The SNR-technique is a new NOx aftertreatment system for lean burn gasoline and diesel applications. The objective of SNR is NOx removal from lean exhaust gas by NOx adsorption and subsequent selective external recirculation and decomposition of NOx in the combustion process. The SNR-project is composed of two major parts. Firstly the development of NOx adsorbents which are able to store large quantities of NOx in lean exhaust gas, and secondly the NOx decomposition by the combustion process. Emphasis of this paper is the investigation of NOx reduction in the combustion process, including experimental investigation and numerical simulation. The NOx decomposition process has been proven in diesel and lean-burn gasoline engines. Depending on the type of engine NOx-conversion rates up to 90 % have been observed. Regarding the complete SNR-system, including the efficiency of the adsorbing material and the NOx decomposition by the combustion, a NOx removal of more than 50% is achievable.

A “thermal pulse” technique has been used to measure thermal diffusivity and thickness of combustion chamber deposits continuously during engine operation. The technique uses a fast-response thermocouple junction at the combustion chamber wall surface and a simplified model which describes the effect of the deposit on the measured temperature cycle. Results from 13 tests using four different fuels and three different commercial additive packages are discussed in the paper. Thermal diffusivity values in the range of 0.85 - 4.2 x 10-7 m2s-1 were measured. Deposit growth is normally a continuous process. However, occasionally deposit flaking events characterised by a sudden significant decrease in deposit thickness were observed.

Lean NOx traps were tested under various laboratory and engine dynamometer conditions to assess the effects of sulfur, temperature, and other exhaust gas parameters on their NOx efficiency and durability. Most recent vendor supplied NOx trap materials have shown significant temperature durability improvements, but sulfur tolerance has remained unchanged. Trap samples were subjected to sulfur poisoning and were desoxed at high temperatures and at various air to fuel ratios. It was found that a simple sulfate model of sulfur interaction with the NOx trapping specie is not sufficient to explain the sulfur interactions observed.

Selective NOx recirculation (SNR), involving adsorption, selective external recirculation and decomposition of the NOx by the combustion process, is itself a promising technique to abate NOx emissions. Three types of materials containing Ba: barium aluminate, barium tin perovskite and barium Y-zeolites have been developed to adsorb NOx under lean-burn or Diesel conditions, with or without the presence of S02. All these materials adsorb NO2 selectively (lean-burn conditions), and store it as nitrate/nitrite species. The desorption takes place by decomposition of these species at higher temperatures. Nitrate formation implies also sulfate formation in the presence of SO2 and SO3, while the NO2/SO2 competition governs the poisoning of such catalysts.

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.