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How Polymer Architecture Affects Permanent Viscosity Loss of Multigrade Lubricants

The Lubrizol Corporation-Michael J. Covitch
Published 1998-10-19 by SAE International in United States
Multigrade automotive lubricants contain polymeric viscosity modifiers which enable the oil to provide adequate hydrodynamic lubrication at high temperatures and good starting/pumping performance at low temperatures. Under operating conditions in engines, transmissions and gear boxes, polymeric additives undergo both temporary and permanent viscosity loss. The former is caused by flow orientation and the latter by molecular chain scission. Whatever the mechanism, original equipment manufacturers are interested in maintaining a minimum level of hydrodynamic viscosity from oil change to oil change. This is often expressed as a “stay-in-grade” requirement.Commercial viscosity modifiers (VM) span a wide range of chemistries and molecular architectures. An earlier paper (1)1 reported on the permanent viscosity loss characteristics of SAE 5W-30 engine oils differing in VM chemistry and speculated that differences in molecular structure - linear chains, A-B block copolymers and stars - could explain most experimental observations. This paper presents a similar study on a series of SAE 15W-40 heavy duty diesel engine oils formulated with OCP, styrene/butadiene, star and PMA viscosity modifiers. Very similar relative permanent viscosity losses to those…
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The Development of the GM 2.2LCNG BI-Fuel Passenger Cars

IMPCO Technologies, Inc.-Xiaobo Sun, Alwin Lutz, Ezio Vermiglio, Mark Arold, Tom Wiedmann
Published 1998-10-19 by SAE International in United States
A CNG bi-fuel version of the Chevrolet Cavalier has been developed as an OEM (Original Equipment Manufacturer) vehicle. The fuel management system is an automatically switching bi-fuel system which is able to control fuel flow rate, spark timing, EGR, and perform OBD-II (On-Board Diagnostics II). The system consists of a CNG fuel tank, fuel filter, electric and manual fuel shutoff valves, high and low pressure regulators, gas mass sensor, mixture control valve, gas distribution system, CNG fuel gauge, OEM exhaust gas oxygen sensor, digital engine control unit (ECU), OEM powertrain control module (PCM) and unique wiring harness. This paper discusses the components, operation, and calibration of the CNG bi-fuel management system.A computer engine simulation model able to predict engine performance, fuel economy, and exhaust emissions, was used to assist spark, fuel, and EGR table mapping. The use of computer modeling reduced system calibration turn-around time as well as the cost of testing. Regulated exhaust emissions of non-methane organic gases (NMOG), carbon monoxide (CO), and Oxides of Nitrogen (NOx) were measured on the FTP Urban Cycle.…
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Optimising CFD Predictions of Diesel Engine Combustion and Emissions Using Design of Experiments: Comparison With Engine Measurements

Perkins Technology Perkins Engines Company Ltd.-J. F. O'Connor, C. L. White, M. R. Charnley
Published 1998-10-19 by SAE International in United States
Design of experiments (DoE) has been used to optimise the accuracy of CFD predictions for diesel combustion and emissions simulations. Eight CFD simulation variables concerning grid geometry and simulation time step were used as the basis for a twenty-two point DoE analysis. The results showed that for practical CFD simulations the CFD predictions were heavily dependent on local grid distribution and the calculation timestep. From the DoE statistical models, two CFD setups were predicted to give optimal combustion and emissions results with CPU times of 11 and 44 hours, model (A) and model(B), respectively. These two CFD model setups were then used to assess the accuracy of CFD combustion and emissions predictions against a series of detailed measurements performed on a single cylinder engine fitted with a common rail fuel injection system.Comparisons with the measured data for twenty-one engine test configurations showed that model (B) delivered more consistent and more accurate predictions of in-cylinder pressure, engine power, fuel consumption, NOx and soot. Predictions of mean in-cylinder pressure were within 4% of the measured values, predicted…
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Passive and Active Performance Characteristics of NOx Catalysts for Direct-Injection Diesel Engines for Passenger Cars

NISSAN Motor Co., Ltd.-Yasuhisa Kitahara, Hiroshi Akama, Maki Kamikubo, Motohiro Shinzawa
Published 1998-10-19 by SAE International in United States
Diesel exhaust contains a lower level of hydrocarbons, which serve as the reductant for the NOx catalyst, than gasoline engine exhaust. An investigation was made of several methods for maximizing the performance of NOx catalysts for direct-injection diesel engines. First, the catalysts were given an HC adsorption capability and then their characteristics were tailored to the HC species contained in diesel exhaust. This HC adsorption capability is designed to achieve better utilization of the HC species in diesel exhaust as a reductant. Second, catalyst performance was examined under passive and active conditions. Excellent catalyst performance was obtained under a passive condition, because at high engine loads, NOx catalysts with an HC adsorption capability can utilize HCs adsorbed under low engine load conditions to reduce NOx. By adopting a common-rail system to facilitate post-injection under an active condition, a higher catalyst inlet HC/NOx ratio can be obtained under all operating conditions, resulting in a dramatic improvement in NOx catalyst performance. However, post-injection causes some problems, such as a fuel economy penalty and deterioration of engine durability.
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Effect of Gas Composition on the NOx Conversion Chemistry in a Plasma

Lawrence Livermore National Laboratory-Bernie M. Penetrante
Zero Emissions Technology-Christopher R. McLarnon
Published 1998-10-19 by SAE International in United States
Much work has been done on the application of plasmas to the treatment of NOx from power plants. In power plant applications, the purpose of the plasma is to oxidize NO to NO2, and eventually to nitric acid. The desired products, in the form of ammonium salts, are then obtained by mixing ammonia with the formed acids. Some form of scrubbing is required to collect the final products. For applications to the treatment of exhausts from cars and trucks, it is very important to make a distinction between NO removal by chemical oxidation and NO removal by chemical reduction. To avoid the need for scrubbing of plasma processing products, the desired method of NO removal is by chemical reduction; i.e. the conversion of NO to benign gaseous products like N2. This paper will discuss the results of an extensive series of experiments aimed towards understanding the effect of gas composition on the NOx conversion chemistry in a plasma. The NOx conversion chemistry in the presence of the individual components, such as N2, O2, H2O, and…
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Effects of In-Cylinder Fuel Spray Formation on Emissions and Cyclic Variability in a Lean-Burn Engine. Part 2: Results

Nissan Motor Co.-Y. Takagi
Shell Research Ltd.-Stephen M. Skippon
Published 1998-10-19 by SAE International in United States
The effects of injection system design, air/fuel ratio, coolant temperature and fuel volatility on engine-out hydrocarbon emissions, NOx emissions and cyclic variability have been studied in a prototype 1.8l lean-burn SI engine. The results have been compared with ILIDS measurements of in-cylinder spray characteristics made under similar conditions, to establish the degree to which variations in fuel spray formation affect engine performance. The engine was found to exhibit a different behaviour when running lean compared to stoichiometric. In lean-burn operation, there was a clear tendency for the best performance to occur under operating conditions which produced charge stratification in the cylinder, whereas when the engine was run with a stoichiometric air/fuel ratio, the best performance was achieved under engine operating conditions which gave the most homogeneous charge in-cylinder. The main effects of increasing mid-range or back-end fuel volatility were to increase evaporation from the inlet port wall film, thereby reducing the contribution made by strip atomisation to the overall in-cylinder droplet population early in the intake stroke. The optimum fuel system for lean-burn operation was…
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Study on Spatial Characteristics of the In-Cylinder Flow Field in an I.C. Engine Using PIV

Tianjin Univ.-Yan-Xiang Yang, Chang-Wen Liu, Jie Liu, Hui Zhao
Published 1998-10-19 by SAE International in United States
In-cylinder flow characteristics in a four-stroke diesel engine were studied experimentally by instantaneous measurements of swirl and squish flow velocity distribution with particle image velocimetry (PIV). The triple-exposed PIV films were interrogated on a self-made system to get the velocity distribution. The measured velocities were analyzed by spatially high-pass and low-pass filtering techniques. Vorticity distributions were also calculated using the measured data. As results, vortex structure of the flow field was clearly visualized. Spatially averaged in-cylinder flow energy was found decaying at high rate but the less-scaled flow components at much lower rate. Clearly visualized squish and reverse squish movements around the top dead center (TDC) during the compression stroke were found strongly affecting the swirl flow field. making the in-bowl flow energy increased.
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Comparison of the Exhaust Emissions of Diesel Fuels Derived from Oil Sands and Conventional Crude Oil

Imperial Oil Ltd.-E. Keith Richardson
National Research Council Canada-Xiaobin Li, Wallace L. Chippior, Ömer L. Gülder
Published 1998-10-19 by SAE International in United States
The effects of fuel properties of both oil-sands-derived and conventional-crude-oil-derived diesel fuels were investigated on a single-cylinder DI research engine. The engine used in this study incorporated features of contemporary medium- to heavy-duty diesel engines and was tuned to the U.S. EPA 1994 emission standards. The engine experiments were run using the AVL 8-mode steady-state simulation of the U.S. EPA heavy-duty transient test procedure. The experimental fuels included 12 fuels blended using refinery streams to have controlled total aromatic levels and 7 other diesel fuels obtained from different sources. The results showed that at a constant cetane number (44) and sulfur content (150 ppm), oil-sands-derived fuels produced similar NOx emissions as their conventional-crude-oil-derived counterparts and total aromatic content and fuel density could be used in a regression model to predict NOx emissions. At the same total aromatic content, the oil sands derived fuel blends produced 5-10% higher PM emissions in the test engine, whereas at the same density, the two kinds of fuel blends produced similar PM emissions. Therefore, the higher PM emissions observed in…
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Comparison of Analytically and Experimentally Obtained Residual Fractions and NOX Emissions in Spark-Ignited Engines

Ford Motor Company-R. Miller, S. Russ, C. Weaver, E. Kaiser, C. Newman, G. Davis, G. Lavoie
Published 1998-10-19 by SAE International in United States
Using a fast-sampling valve, residual-fraction levels were determined in a 2.0L spark-ignited production engine, over varying engine operating conditions. Individual samples for each operating condition were analyzed by gas-chromatography which allowed for the determination of in-cylinder CO and CO2 levels. Through a comparison of in-cylinder measurement and exhaust data measurements, residual molar fraction (RMF) levels were determined and compared to analytical results. Analytical calculations were performed using the General Engine SIMulation (GESIM) which is a steady state quasi-dimensional engine combustion cycle simulation. Analytical RMF levels, for identical engine operating conditions, were compared to the experimental results as well as a sensitivity study on wave-dynamics and heat transfer on the analytically predicted RMF. Similarly, theoretical and experimental NOx emissions were compared and production sensitivity on RMF levels explored. A new heat transfer algorithm is developed which produced favorable agreement between the experimental and analytical RMF measurements. Improved NOx predictions were similarly observed over varying operating conditions using the super-extended Zel'dovich mechanism (SEZM) in conjunction with the new heat transfer algorithms. The SEZM produces NOx emissions within…
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Turbulent Flame Speed Closure Model: Further Development and Implementation for 3-D Simulation of Combustion in SI Engine

Chalmers University of Technology-Johan Wallesten, Andrei N. Lipatnikov
Volvo Car Components Corporation-Jonny Nisbet
Published 1998-10-19 by SAE International in United States
A Turbulent Flame Speed Closure Model is modified and implemented into the FIRE code for use in 3D computations of combustion in an SI-engine. The modifications are done to account for mixture inhomogeneity, and mixture compression through the dependency of local equivalence ratio, pressure and temperature on the chemical time scale and a global reaction time scale. The model is also subjected to further evaluation against experimental data, covering different mixture and turbulence conditions.The combustion process in a 4-valve pentroof combustion chamber is simulated and heat release rates and spatial flame distribution are evaluated against experimental data. The computations show good agreement with the experiments. The model has proven to be a robust and time effective simulation tool with good predictive ability.
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