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The objective of the research project was the investigation of lubricant film formation in elastohydrodynamic contacts for oils of different origin (paraffinic, naphthenic, polyalphaolefin) and various types of VI-improvers (polymethacrylate, olefin copolymer, styrene butadiene copolymer). An essential part of the research was to find out whether VI-improvers maintain their thickening effect under contact conditions of high pressure (p=10,000 bar) and temperature (ϑ=50-90 °C), high shear rate (γ̇=106 s-1) and short contact time, all these conditions occurring simultaneously. A twin disk machine was used to determine values of film thickness in a line contact. For these measurements, an electrical capacitance method was used. In addition to a thermal viscosity loss, high shear rate γ̇ leads for VI improved oils to temporary viscosity loss and thus reduced film thickness. Additional permanent viscosity loss due to shear thinning reduces measured film thickness further.

A test facility was constructed at University College London to study fuel spray structure within a gasoline direct injection engine. The facility consisted of a single cylinder research engine with extensive optical access and a novel video imaging and analysis system. The engine used an experimental prototype 4-valve cylinder head with direct in-cylinder high pressure fuel injection, provided by a major automotive manufacturer. The fuel spray was illuminated using a pulsed copper-vapour laser. Results are presented that illustrate the spray behaviour within the fired research engine. A laser light sheet provided an insight into the inner spray cone behaviour.

A new type direct-injection stratified-charge combustion system for gasoline engines is developed by the authors. In the system, gasoline is directly injected into a cylinder near the end of compression stroke by a nozzle with the injection holes unequally spaced on its tip. The angles among sprays in the vicinity of spark plug are small, and become larger downstream along the direction of air swirl motion. Therefore the circularly concentration stratification form rich to lean of air-fuel mixture is mechanically realized to ensure the reliable ignition and smooth flame propagation in the inhomogeneous mixture after sparking. The selection of main parameters of the system, the performance and the combustion characteristics of the engine after optimization of those parameters are introduced in detail in this paper.

Increasing interest in gasoline engine emissions has focused attention on the fuel compositional and emissions effects that govern NOx conversion over the catalyst. This study reports the transient effects of individual species emissions and catalyst conversions on NOx conversion made using Fourier Transform Infra Red (FTIR) spectroscopy of the engine-out and tailpipe emissions (regulated and speciated) during the testing of a catalyst equipped gasoline vehicle run on multi-component model fuels over the standard European cycle. FTIR measurements confirm that transient NO conversion is directly correlated with that of CH4, especially within the Urban Drive Cycle (EUDC). Other hydrocarbon species do not govern the transient variability in NO conversion. This vehicle maintained ϕ≤ 1.0 practically throughout the EUDC and consequently no correlation was seen between transient NO conversion and equivalence ratio.

The main factors influencing the development of engine oils for the future are environmental protection, resource utilization and customer satisfaction. Improving engine oil no longer means just providing adequate durability but also maximizing fuel efficiency, minimizing detrimental effects on emission systems and maximizing useful life. Opportunities for improvements in these areas, discussed in detail in this paper, will be considered by ILSAC (International Lubricant Standardization and Approval Committee formed by the American Automobile Manufacturers Association, AAMA, and Japan Automobile Manufacturers Association, JAMA) in developing the ILSAC GF-3 standard to be introduced around the year 2000.

Recently, we reported the development of a new reduced chemical kinetic model for predicting reactivity and autoignition behavior of primary reference fuels in a motored research engine. The predicted oxidation behavior (ignition delay, preignition heat release, and evolution of key chemical species) is in fairly good agreement with experiments. In addition, the model reproduced the experimentally observed dependence of overall reactivity on charge density and manifold inlet conditions. This paper reports our initial effort to apply this new reduced chemical kinetic model to other fuels. Specifically, the model was tested using neat n-butane and n-butane/iso-butane blends (10, 20, and 48 percent by volume iso-butane) under skip fired conditions. The only adjustments made in the model were to the fuel specific rate parameters of the RO2· isomerization reaction, the reaction of aldehydes with OH·, and the reaction forming cyclic ethers.

A new reciprocating tribo-tester was constructed for simulation of piston-ring/cylinder-liner contacts. Wear behavior and wear mechanisms were investigated for 25 advanced material ring/liner pairs as well as the existing Mo-coated-cast-iron-ring/cast-iron-liner pair (MCI/CI). Results of wear data and wear mechanisms provide a base for selecting and understanding the wear behavior of these materials. The nitrided-stainless-steel-ring/Al2O3-reinforced-6061-Al-liner pair gave the highest wear resistance among the tested material pairs and had a wear resistance 10 times of the MCI/CI pair. Scuffing resistance of 19 material pairs were also examined. The MCI/CI pair nearly had the lowest scuffing resistance among the tested pairs. The scuffing resistance and scuffing temperature depends strongly on material combination.

This paper reports an investigation of the association between flame kernel movement and cyclic variability and assesses the relative importance of this phenomenon, with all other parameters that show a cyclic variability held constant. The flame is assumed to be subjected to a “random walk” by the fluctuating velocity component of the flow field as long as it is of the order of or smaller than the integral scale. However, the mean velocity also imposes prefered convection directions on the flame kernel motion. Two-point LDA (Laser Doppler Anemometry) measurements of mean velocity, turbulence intensity and integral length scale are used as input data to the simulations. A quasi-dimensional computer code with a moving flame center position is used to simulate the influence of these two components on the performance of an S I engine with a tumble-based combustion system.

The search for fuel efficient engines that also offer good performance and fuel economy at moderate cost prompted the development of the Split Port Induction (SPI) concept at Ford Motor Company. Ford has upgraded two families of 2-valve engines, the 2.0L CVH 14 and the 3.8L and 4.2L Essex V6's, with the Split Port Induction concept. SPI offers an improved WOT torque curve, better part load dilution tolerance for fuel economy and superior idle combustion stability. This is accomplished by dividing the intake port into two passages and inserting an intake manifold runner control (IMRC) valve into the secondary passage. The opening of this valve determines the level of in-cylinder charge turbulence and volumetric efficiency according to engine operating conditions. The development of the concept and the improvements resulting from its application to these engines will be described and discussed.

The ability of engine oils to provide hydrodynamic lubrication under operating conditions is essential. Such lubrication occurs at very high shear rates -- often well in excess of the current SAE J300 specification of one million reciprocal seconds. This paper presents data obtained for shear rates beginning as low as two hundred thousand to above five million reciprocal seconds as well as the technique developed to obtain these shear rates.

Influences of high shear viscosity and boundary friction on ASTM Sequence VI and Sequence VI-A fuel efficiency (FE) performances are studied through the use of laboratory screening tests. Statistical analysis of FE and screening test data suggests that optimum screening test conditions are identical for the two engine tests. This being so, a single set of screening test data allows both engine test outcomes to be predicted and the changing influence of the lubricant to be readily perceived. A further investigation is made of the influence of pressure-viscosity coefficient on Sequence VI-A fuel efficiency performance. Values of this property are determined through measurements of elastohydrodynamic oil film thickness and the results included in a further analysis of engine performance. A small but significant influence on fuel efficiency is detected.

EHC design and engine operation requirements for a battery powered EHC-cascade were investigated using flow rig, engine dynamometer and vehicle evaluations. Low mass and Pd-coated heater elements and light-off converters are recommended for optimum light-off performance. Raising the heating power improves light-off. However, battery powered systems are limited to 1.5 kW. Rich engine operation combined with an excess of secondary air results in high exothermic energy output. The benefit of additional heating and the impact of cascade position (close coupled or underfloor) are closely related to the test cycle. ULEV limits were achieved using a MY 91 vehicle without upgrades in engine control.

A catalytic converter thermal management system (TMS) using variable-conductance vacuum insulation and phase-change thermal storage can maintain the converter temperature above its operating temperature for many hours, allowing most trips to begin with minimal “cold-start” emissions. The latest converter TMS prototype was tested on a Ford Taurus (3.0 liter flex-fuel engine) at Southwest Research Institute. Following a 24-hour soak, the FTP-75 emissions were 0.031, 0.13, and 0.066 g/mile for NMHC, CO, and NOx, respectively. Tests were also run using 85% ethanol (E85), resulting in values of 0.005, 0.124, and 0.044 g/mile, and 0.005 g/mile NMOG. Compared to the baseline FTP levels, these values represent reductions of 84% to 96% for NMHC, NMOG, and CO.

It is important to understand the influence of housing stiffness on bearing performance, particularly for the connecting rod bearings of automotive engines. It is known that the engine lubricant shows a piezoviscous characteristic whereby its viscosity changes under the influence of pressure. Engine bearings under a heavy load are apt to be influenced in this way. In this study, the effects of connecting rod stiffness and lubricant piezoviscosity on bearing performance were examined by elastohydrodynamic lubrication (EHL) analysis under conditions corresponding to the high-speed operation of an actual engine. The results indicated that under such heavy load conditions housing stiffness greatly affects friction loss because of lubricant piezoviscosity. It was also found that the piezoviscosity of the lubricant has a large effect on bearing performance, as does its viscosity under atmospheric pressure.

Many engineering components in engines and machines are of a counter conformal geometry (e.g. valve trains, rolling element bearings and gears) and impose not only high shear rates and temperatures but also extremely high pressures on the lubricant. The effect of pressure is to elastically deform the sliding/rolling contact geometry. Of crucial importance to the engineering and lubricant designer is the magnitude of the lubricant film thickness generated under these severe conditions. Steady state isothermal elastohydrodynamic (EHD) lubrication is now relatively well understood by the use of engineering correlations, first propounded by Dowson et. al., for both line and point contacts, which are used as design tools. However, with ever increasing demands to improve the efficiency of machines, these correlations do not satisfy all the design needs, especially under reversal conditions, where wear is a major problem.

The estimation of fuel economy benefits gained through improved engine oils using ASTM test procedures is expensive and time consuming. This paper describes a methodology to predict ASTM Sequence VI and VIA fuel economy based on laboratory bench tests. High shear rate viscosities were measured using a tapered bearing simulator and boundary friction coefficients were measured using a Plint reciprocating machine at temperatures used in Sequence VI and VIA tests. Weighted viscosities and weighted friction coefficients were calculated from these measurements using weighting factors identical to those used in the Sequence tests. The measured Sequence VI and VIA fuel economy numbers were correlated with the weighted viscosities and weighted friction coefficients. An excellent correlation was observed between Sequence VIA fuel economy and weighted high shear rate viscosities and friction coefficients whereas a reasonable correlation was observed for Sequence VI fuel economy.

This is a first of a series of papers describing how the replacement of some of the inlet air with EGR modifies the diesel combustion process and thereby affects the exhaust emissions. This paper deals with only the reduction of oxygen in the inlet charge to the engine (dilution effect). The oxygen in the inlet charge to a direct injection diesel engine was progressively replaced by inert gases, whilst the engine speed, fuelling rate, injection timing, total mass and the specific heat capacity of the inlet charge were kept constant. The use of inert gases for oxygen replacement, rather than carbon dioxide (CO2) or water vapour normally found in EGR, ensured that the effects on combustion of dissociation of these species were excluded. In addition, the effects of oxygen replacement on ignition delay were isolated and quantified.

There is a gradient of fuel concentration in the conventional direct injection diesel engine fuel spray. Therefore, a region of stoichiometric mixture ratio exists in the spray and this results in production of large amounts of NOx. In this study, the fuel injection timing was advanced greatly to promote fuel and air mixing. Using this injection method, the engine could be operated with PREmixed lean DIesel Combustion (PREDIC), and NOx emissions were reduced greatly. To avoid collision of the fuel spray with the cylinder liner. the fuel was injected simultaneously with two side injectors. The two side injector sprays collided with each other and remained in the center region of the cylinder. Thus, mixing of the fuel and air was promoted by a long ignition delay period. Using conventional injection methods, NOx could not be reduced below 400ppm at an excess air ratio of 2.7. On the contrary. in the case of PREDIC, NOx emissions could be reduced to 20ppm at the same excess air ratio.

In this study the effect of blending biodiesel (methyl soyester) with conventional diesel on emissions has been investigated. A 1991 MC Series 60 engine was employed and emissions of NOx, CO, THC, and PM were determined using the heavy-duty transient test. The fuels tested were a reference diesel, 20%, 35%, and 65% biodiesel blends in the reference diesel, as Well as 100% biodiesel. These tests show that as the percent biodiesel increased, the NOx, emission increased, while THC, CO and PM decreased. For 35% biodiesel, the composite NOx emission increased by nearly 1% while the composite particulate emission decreased by 26% relative to the reference diesel. The NOx increase of 1% was found to be statistically significant at the 99% level. For 100% biodiesel, the composite NOx increased by 11% while PM was decreased by 66%. CO was reduced by 47% and total hydrocarbon by 44%.

The effect of several aqueous metal-salt solutions on NOx and smoke lowering in an IDI diesel engine were examined. The solutions were directly injected into a divided chamber independent of the fuel injection. The results showed that significant lowering in NOx and smoke over a wide operation range could be achieved simultaneously with alkali metal solutions which were injected just prior to the fuel injection. With sodium-salt solutions, for instance, NOx decreased by more than 60 % and smoke decreased 50 % below conventional operation. The sodium-salt solution reduced dry soot significantly, while total particulate matter increased with increases in the water soluble fractions.