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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.

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 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.

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.

Parallel measurements of lubricant-film behavior and oil consumption in two identical small production IDI diesel engines are presented. Oil consumption was measured using tritium as a radioactive tracer, and instantaneous film thickness data between the piston and liner were obtained using laser fluorescence diagnostics. The data covered single- and multi-grade lubricants and five different ring configurations (two-piece vs three-piece rings at various ring tensions). The data illustrate (a) oil-film profiles under the rings, especially around the leading and trailing edges, (b) accumulation of oil on piston lands and skirt, (c) circumferential variations around the bore, (d) observations on ring rotation, and (e) the piston-skirt oil-pumping mechanism. Effects of lubricants and piston-ring configurations on oil-film characteristics are investigated, and the oil consumption data are compared with oil-film thickness measurements.

The cylinder of the aluminum engine block without iron sleeve was coated directly with thin thermal barrier coatings of zirconia and chrome oxide. The cylinder head and valve face and the piston crown were also coated. These three engine components were tested individually and together. The fuel consumption performance of this 84 x 70 mm direct injection diesel engine improved 10% with only coated cylinder bore. When the fuel injection timing of the coated cylinder bore engine was retarded by about 2°CA, emissions characteristics were approximately the same level as for the baseline engine with 8% improvement in brake specific fuel consumption compared with the baseline engine. At constant fuel flow rate to the engine, the exhaust and cylinder head temperatures were higher for the insulated bore case. One can summarize the combustion temperature must have been higher and heat release rates were faster in the insulated case.

The trend toward lighter vehicles for improved performance has recently introduced the use of aluminum and plastic materials for vehicle bodies and drive trains. In particular, the aluminum alloy block for engine application is certain to reappear. The soft aluminum cylinder liner will require additional treatment before acceptance. Three possible approaches appear to solve the aluminum cylinder liner dilemma. These approaches are: 1. Use of high silicon aluminum such as the 390 aluminum. 2. Insert or cast steel liners into the aluminum engine block. 3. Ceramic coat the low cost standard aluminum engine block. Each has known advantages and disadvantages. It is the purpose of this paper to present the merits of Option 3, the ceramic coated aluminum cylinder bore from the standpoint of low weight, cost, and tribological effectiveness. The advantages of approaches (1) and (2) are obvious. High temperature after treatment of the ceramic engine components is not required.

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.

In this study, changes in the composition of lubricant additives in the power cylinder oil are examined. Samples are extracted from a single cylinder heavy-duty diesel engine in two locations during engine operation; the crankcase and the top ring groove of the piston. Emissions of lubricant-derived ash-forming elements are lower than would be expected based on oil consumption and crankcase oil composition. This occurs partly because the inorganic additive compounds are less volatile than light-end hydrocarbons in the base oil. The tribology of the piston ring pack also affects the composition of the oil consumed in the power cylinder system. The elemental composition of oil extracted from the top ring groove is significantly different than the crankcase oil. Additive metals are concentrated in the top ring groove of the power cylinder. Detergent compounds (i.e. Ca and Mg) concentrate due to the volatility of the base oil. The metals associated with ZDDP (i.e.

The experimental emissions testing of a turbocharged six cylinder Caterpillar 3116 diesel engine converted to the Miller cycle operation was conducted. Delayed intake valve closing times were also investigated. Effects of intake valve closing time, injection time, and insulation of piston, head, and liner on the emission characteristics of the Miller cycle engine were experimentally verified. Superior performance and emission characteristic was achieved with a LHR insulated engine. Therefore, all emission and performance comparisons are made with LHR insulated standard engine with LHR insulated Miller cycle engine. Particularly, NOx, CO2, HC, smoke and BSFC data are obtained for comparison. Effect of increasing the intake boost pressure on emission was also studied. Poor emission characteristics of the Miller cycle engine are shown to improve with increased boost pressure. Performance of the insulated Miller cycle engine shows improvement in BSFC when compared to the base engine.

A previous paper (1)* described the performance improvements which can be obtained by using an “adiabatic” (uncooled) engine for military trucks. The fuel economy improved 16% to 37% (depending upon the duty cycle) and was documented by dynamometer testing and vehicle testing and affirmed by vehicle simulation. The purpose of this paper is to document a NATO cycle 400 hour durability test which was performed on the same model adiabatic engine. The test results showed that the engine has excellent durability, low lubricating oil consumption and minimal deposits.

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 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.

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.

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 novel approach to condition the lubricant at a fixed station in the oil circuit is explored as a potential means to reduce additive requirements or increase oil drain interval. This study examines the performance of an innovative oil filter which releases no additives into the lubricant, yet enhances the acid control function typically performed by detergent and dispersant additives. The filter chemically conditions the crankcase oil during engine operation by sequestering acidic compounds derived from engine combustion and lubricant degradation. Long duration tests with a heavy-duty diesel engine show that the oil conditioning with the strong base filter reduces lubricant acidity (TAN), improves Total Base Number (TBN) retention, and slows the rate of viscosity increase and oxidation. The results also indicate that there may be a reduction in wear and corrosion.

Ash, mostly from essential lubricant additives, affects diesel particulate filter (DPF) pressure-drop sensitivity and limits filter service life. It raises concern in the lubricant industry to properly specify new oils, and engine and aftertreatment system manufacturers have attempted to find ways to mitigate the problem. To address these issues, results of detailed measurements of ash characteristics in the DPF and their effects on filter performance are presented. In this study, a heavy-duty diesel engine was outfitted with a specially designed rapid lubricant degradation and aftertreatment ash loading system. Unlike previous studies, this system allows for the control of specific exhaust characteristics including ash emission rate, ash-to-particle ratio, ash composition, and exhaust temperature and flow rates independent of the engine operating condition.

Engine oil consumption is recognized to be a significant source of pollutant emissions. Unburned or partially burned oil in the exhaust gases contributes directly to hydrocarbon and particulate emissions. In addition, chemical compounds present in oil additives poison catalytic converters and reduce their conversion efficiency. Oil consumption can increase significantly during critical non-steady operating conditions. This study analyzes the oil consumption behavior during ramp transients in load by combining oil consumption measurements, in-cylinder measurements, and computer-based modeling. A sulfur based oil consumption method was used to measure real-time oil consumption during ramp transients in load at constant speed in a production spark ignition engine. Additionally in-cylinder liquid oil behavior along the piston was studied using a one-point Laser-Induced-Fluorescence (LIF) technique.

Engine oil consumption is an important source of hydrocarbon and particulate emissions in automotive engines. Oil evaporating from the piston-ring-liner system is believed to contribute significantly to total oil consumption, especially during severe operating conditions. This paper presents an extensive experimental and theoretical study on the contribution of oil evaporation to total oil consumption at different steady state speed and load conditions. A sulfur tracer method was used to measure the dependence of oil consumption on coolant outlet temperature, oil volatility, and operating speed and load in a production spark ignition engine. Liquid oil distribution on the piston was studied using a one-point Laser-Induced-Fluorescence (LIF) technique. In addition, important in-cylinder variables for oil evaporation, such as liner temperature and cylinder pressure, were measured. A multi-species cylinder liner oil evaporation model was developed to interpret the oil consumption data.

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.