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The use of hydrogen as a fuel supplement for lean-burn engines at higher compression ratios has been studied extensively in recent years, with good promise of performance and efficiency gains. With the advances in reformer technology, the use of a gaseous fuel stock, comprising of substantially higher fractions of hydrogen and other flammable reformate species, could provide additional improvements. This paper presents the performance and emission characteristics of a gas mixture of equal volumes of hydrogen, CO, and methane. It has recently been reported that this gas mixture can be produced by reforming of ethanol at comparatively low temperature, around 300C. Experiments were performed on a 1.8-liter passenger-car Nissan engine modified for single-cylinder operation. Special pistons were made so that compression ratios ranging from CR= 9.5 to 17 could be used. The lean limit was extended beyond twice stoichiometric (up to lambda=2.2).

The challenge posed by the long run times necessary to accurately quantify ash effects on diesel aftertreatment systems has led to numerous efforts to artificially accelerate ash loading, with varying degrees of success. In this study, a heavy-duty diesel engine was outfitted with a specially designed rapid lubricant degradation and aftertreatment ash loading system. Unlike previous attempts, the proposed methodology utilizes a series of thermal reactors and combustors to simulate all three major oil consumption mechanisms, namely combustion in the power cylinder, evaporative and volatile losses, and liquid losses through the valve and turbocharger seals. In order to simulate these processes, each thermal reactor allows for the precise control of the level of lubricant additive degradation, as well as the form and quantity of degradation products introduced into the exhaust upstream of the aftertreatment system.

This paper presents a numerical model of the rotational and lateral dynamics of the piston (secondary motion) and piston slap in mixed lubrication. Piston dynamic behavior, frictional and impact forces are predicted as functions of crank angle. The model considers piston skirt surface waviness, roughness, skirt profile, thermal and mechanical deformations. The model considers partially-flooded skirt and calculates the pressure distributions and friction in the piston skirt region for both hydrodynamic and boundary lubrication. Model predictions are compared with measurements of piston position using gap sensors in a single-cylinder engine and the comparison between theory and measurement shows remarkable agreement.

While metal fiber filters have successfully shown a high degree of particle retention functionality for various sizes of diesel engines with a low pressure drop and a relatively high filtration efficiency, little is known about the effects of lubricant-derived ash on the fiber filter systems. Sintered metal fiber filters (SMF-DPF), when used downstream from a diesel engine, effectively trap and oxidize diesel particulate matter via an electrically heated regeneration process where a specific voltage and current are applied to the sintered alloy fibers. In this manner the filter media essentially acts as a resistive heater to generate temperatures high enough to oxidize the carbonaceous particulate matter, which is typically in excess of 600°C.

Ash, primarily derived from diesel engine lubricants, accumulates in diesel particulate filters directly affecting the filter's pressure drop sensitivity to soot accumulation, thus impacting regeneration frequency and fuel economy. After approximately 33,000 miles of equivalent on-road aging, ash comprises more than half of the material accumulated in a typical cordierite filter. Ash accumulation reduces the effective filtration area, resulting in higher local soot loads toward the front of the filter. At a typical ash cleaning interval of 150,000 miles, ash more than doubles the filter's pressure drop sensitivity to soot, in addition to raising the pressure drop level itself. In order to evaluate the effects of lubricant-derived ash on DPF pressure drop performance, a novel accelerated ash loading system was employed to generate the ash and load the DPFs under carefully-controlled exhaust conditions.

This paper is a direct continuation of a previous study that addressed the performance and design of a variable compression engine, the Alvar-Cycle Engine [1]. The earlier study was presented at the SAE International Conference and Exposition in Detroit during February 23-26, 1998 as SAE paper 981027. In the present paper test results from a single cylinder prototype are reviewed and compared with a similar conventional engine. Efficiency and emissions are shown as function of speed, load, and compression ratio. The influence of residual gas on knock characteristics is shown. The potential for high power density through heavy supercharging is analyzed.

Irreversible plugging of diesel particulate filters caused by lubricant-derived metallic ash is the single most important factor responsible for long-term performance degradation and reduction in the service life of these filters. While a number of studies in the open literature have already demonstrated the benefits of diesel particulate traps and highlighted some of the difficulties associated with trap operation, many specific factors affecting trap performance and service life are still not well understood. The exact composition and nature of the exhaust entering the trap is one of the most important parameters affecting both short-term trap operation and long-term durability. In this study a fully instrumented Cummins ISB 300 six-cylinder, 5.9 liter, diesel engine was outfitted with a diesel particulate filter and subjected to a subset of the Euro III 13-mode stationary test cycle.

The oil film thickness distribution between the top ring and liner was observed using laser fluorescence (LF). Five different commercial lubricants, two single grades and three multigrades, were studied at two azimuthal, mid-stroke locations for five speed/load combinations in a small IDI diesel engine. Cavitation is never observed. The lubricant always separates tangent to the ring surface. The rheology of the oil flow under the ring is consistent with a non-Newtonian viscosity without elasticity. The difference between lubricant type (single or multigrade) corresponds to differences in inlet and outlet conditions. Using an analytical model together with the measured oil distributions, calculations demonstrate a difference in friction between single and multigrade lubricants. The multigrade lubricants have a lower friction coefficient, consistent with improvements in fuel economy reported in the literature.

This paper describes the study and the results obtained to determine the performance deterioration of diesel particulate traps due to ash accumulation. Based on the ash emission rate in an engine exhaust and the full-size trap volume, a flow and distance simulation technique was developed to translate the results from bench tests of small scaled down traps to engine conditions. Fuel doped with metalloorganic additives was used to accelerate the ash loading of the scaled traps. The study was conducted on both a cellular ceramic trap and a wire-mesh trap. Results indicate that for a 60 liter, ceramic trap mounted on the exhaust of a heavy duty engine, the pressure drop, Δp, will double in approximately 90,000 km. It is also seen that for the same size wire-mesh trap, the Δp will increase by 70% of the clean trap Δp in about 200,000 km. The paper also describes the work done to determine the effect of particulate trap pore size on ash accumulation in cellular ceramic traps.

The effects of lubrication system parameters on particulate emission rate and composition were studied. Engine load, viscosity and piston-ring gap were varied. Particulate rate and composition were measured for multiple combinations of lubricant and ring-gap configurations at three different engine operating conditions. Particulate rates were higher with the lower viscosity oil and larger with the wider top-ring gap. At high load, the difference in particulate rate was due to changes in the non-soluble portion, while at medium and low loads, the change in particulate rate was due to differences in the lubricant-derived portion of the soluble organic fraction (SOF). Additionally, changes in the fuel-derived portion of the SOF were discovered and attributed to changes in fuel-absorption in the oil film.

The effects of combustion chamber and intake valve deposit build-up on the knocking characteristics of a spark ignition engine were studied. A Chrysler 2.2 liter engine was run continuously for 180 hours to build up intake valve and combustion chamber deposits. In the tests reported here, the gasoline used contained a deposit controlling fuel additive. The engines's octane requirement increased by 10 research octane numbers during this extended engine operating period. At approximately 24 hour intervals during these tests, the engine was audibly knock rated to determine its octane requirement. Cylinder pressure data was collected during knocking conditions to investigate the knocking characteristics of each cylinder, and deposit build-up effects on those statistics. Cylinder-to-cylinder variations in knock statistics were studied. Analysis of the data indicated that some 20 to 40 percent of cycles knock before the knock is audibly detected.

The life of an automotive engine is often limited by the ability of its components to resist wear. Zinc dialkyldithiophosphate (ZDDP) is an engine oil additive that reduces wear in an engine by forming solid antiwear films at points of moving contact. The effects of this additive are fairly well understood, but there is little theory behind the kinetics of antiwear film formation and removal. This lack of dynamic modeling makes it difficult to predict the effects of wear at the design stage for an engine component or a lubricant formulation. The purpose of this discussion is to develop a framework for modeling the formation and evolution of ZDDP antiwear films based on the relevant chemical pathways and physical mechanisms at work.

The transportation sector in the United States is a major contributor to global energy consumption and carbon dioxide emission. To assess the future potentials of different technologies in addressing these two issues, we used a family of simulation programs to predict fuel consumption for passenger cars in 2020. The selected technology combinations that have good market potential and could be in mass production include: advanced gasoline and diesel internal combustion engine vehicles with automatically-shifting clutched transmissions, gasoline, diesel, and compressed natural gas hybrid electric vehicles with continuously variable transmissions, direct hydrogen, gasoline and methanol reformer fuel cell hybrid electric vehicles with direct ratio drive, and battery electric vehicle with direct ratio drive.

The increased use of biodiesel fuels has raised concerns over the fuel's impact on engine performance and hardware compatibility. While these issues have received much attention in recent years, less well-known are the effects of biodiesel on engine-out ash emissions and lubricant properties. Significant differences in composition between biodiesel and petroleum diesel fuels have the potential to influence ash emissions, thereby affecting aftertreatment system performance. Further, the fuel also interacts directly with the lubricant through fuel dilution, and may impact lubricant properties. In this study, a 5.9L, 6 cylinder, Cummins ISB 300 diesel engine was outfitted with a specially designed rapid lubricant aging system and subjected to a set of steady-state engine operating conditions. The lubricant aging system allows for the investigation of the interactions of emissions and combustion products, as well as fuel dilution, on lubricant properties in an accelerated manner.

The oil control ring is the most critical component for oil consumption and friction from the piston system in internal combustion engines. Three-piece oil control rings are widely used in Spark Ignition (SI) engines. However, the dynamics and lubrication of three piece oil control rings have not been thoroughly studied from the theoretical point of view. In this work, a model was developed to predict side sealing, bore sealing, friction, and asperity contact between rails and groove as well as between rails and the liner in a Three Piece Oil Control Ring (TPOCR). The model couples the axial and twist dynamics of the two rails of TPOCR and the lubrication between two rails and the cylinder bore. Detailed rail/groove and rail/liner interactions were considered. The pressure distribution from oil squeezing and asperity contact between the flanks of the rails and the groove were both considered for rail/groove interaction.

A technique of calculating the evolution of turbulence during the combustion phase of a reciprocating engine cycle is presented. The method is based on a local linearization of the full non-linear equations of motion. It is valid when the turbulence is distorted more rapidly by the changes in mean flows than it interacts with itself. The theory requires as input strain rates of the deterministic mean motion, and the initial state of turbulence. Calculations are presented for the particular case of a cylindrical chamber geometry. In the burning process it is assumed that the spark plug is located on the cylinder axis and the strain field is that established by the flame front. The theory calculates the turbulence parameters during the combustion period. Combustion rates, and durations, as a function of equivalence ratio and the initial turbulent and thermodynamic conditions.

Mechanisms of NH₃ generation using LNT-like catalysts have been studied in a bench reactor over a wide range of temperatures, flow rates, reformer catalyst types and synthetic exhaust-gas compositions. The experiments showed that the on board production of sufficient quantities of ammonia on board for SCR operation appeared feasible, and the results identified the range of conditions for the efficient generation of ammonia. In addition, the effects of reformer catalysts using the water-gas-shift reaction as an in-situ source of the required hydrogen for the reactions are also illustrated. Computations of the NH₃ and NOx kinetics have also been carried out and are presented. Design and impregnation of the SCR catalyst in proximity to the ammonia source is the next logical step. A heated synthetic-exhaust gas flow bench was used for the experiments under carefully controlled simulated exhaust compositions.

As a part of the effort to comply with increasingly stringent emission standards, engine manufacturers strive to minimize engine oil consumption. This requires the advancement of the understanding of the characteristics, sources, and driving mechanisms of oil consumption. This paper presents a combined theoretical and experimental approach to separate and quantify different oil consumption sources in a production spark ignition engine at different speed and load conditions. A sulfur tracer method was used to measure the dependence of oil consumption on engine operating speed and load. Liquid oil distribution on the piston was studied using a Laser-Induced-Fluorescence (LIF) technique. In addition, important in-cylinder parameters for oil transport and oil consumption, such as liner temperatures and land pressures, were measured.

The way In which combustion chamber geometry affects combustion in SI engines was studied using a quasi-diraensional cycle simulation. Calculations were performed to investigate the following questions: (i) the sensitivity of geometric effects on combustion to engine operating conditions; (ii) the differences in burn duration between ten chamber geometries and spark plug locations; and (iii) the relative merits of improved chamber design and amplified turbulence as means to reduce burn duration. The results from these studies are presented and discussed.