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A number of wear resistant coatings has been developed using physical vapor deposition(PVD) process. However this coating process has not yet been widely used in the automotive industry. The purpose of this work was to evaluate thin PVD coatings such as diamond like carbon doped with tungsten (W-DLC), molybdenum-disulfide doped with aluminum (MoS2-Al), and chrome nitride (CrN). Some of these coatings were previously found to have low friction, high wear resistance, or both when tested in unlubricated conditions. In the present work, the experiments were conducted using a Cameron-Plint apparatus in lubricated conditions. The ring counterfaces used were Cr-plated and gas-nitrided compression rings. Our data also indicated that some PVD coatings with thicknesses in the same order of magnitude as the surface roughness of the liners did show some improvement in liner wear resistance. The suitability of thin coatings for liner applications needs additional study.

We have developed a methodology for predicting combustion and emissions in a Homogeneous Charge Compression Ignition (HCCI) Engine. The methodology judiciously uses a fluid mechanics code followed by a chemical kinetics code to achieve great reduction in the computational requirements; to a level that can be handled with current computers. In previous papers, our sequential, multi-zone methodology has been applied to HCCI combustion of short-chain hydrocarbons (natural gas and propane). Applying the same procedure to long-chain hydrocarbons (iso-octane) results in unacceptably long computational time. In this paper, we show how the computational time can be made acceptable by developing a segregated solver. This reduces the run time of a ten-zone problem by an order of magnitude and thus makes it much more practical to make combustion studies of long-chain hydrocarbons.

The Cummins A3.4-125 (rated 93 kW at 3600 rpm) has been developed to meet 1991 US and California light-heavy duty emission standards, replacing the Cummins 6AT3.4 (formerly Onan L634T-A). Compliance with the stringent particulate standard has been achieved by redesigning the combustion chamber, a systematic oil control program, and charge air cooling. The Ricardo Comet combustion chamber was modified to a downstream glowplug configuration. Oil control efforts addressed all sources of oil derived particulate. With charge air cooling, NOx emissions were reduced while improving fuel economy, torque output, altitude capability, and engine durability. THE CUMMINS A3.4-125 is an evolutionary development of the 1988-90 6AT3.4 engine. The development was driven primarily by 1991 US and California light-heavy duty emission standards, but also was the result of a policy of continuous product improvement. The Cummins A Series diesel engine family was conceived as the Onan L Series (1*).

In this paper, two approaches are presented for steady state fluid flow calculations in complex diesel engine exhaust valve-port geometries. The first one simplifies the geometry and concentrates on the fine details in the valve seat region using two-dimensional axisymmetric Navier-Stokes equations. Various configurations are examined to show the usefulness of the approach for design purposes. The second approach is illustrated by a full 3-D simulation of the flow in a complex cylinder-valve-port geometry with two exhaust valves. Details are presented on the generation of the geometry and the mesh, and important flow features from the CFD solution are described. For both approaches, limited available experimental information is presented in support of the computational results.

A high horsepower, low heat rejection diesel engine is being developed to meet future Army heavy combat vehicle requirements. This engine features high power output in a compact design that is oil-cooled allowing for a significant reduction in radiator size. This design requires a lubricant which can survive a sump temperature of 160°C, for 300 hours with transient sump temperature surges to over 177°C. A comprehensive high temperature lubricant development program has been initiated to address the need for this new design. A modified Cummins 10 liter diesel engine was used to simulate the operating condition of this low heat rejection engine. The premium commercial lubricant that was tested survived only 58 hours before completely losing oxidative stability. Several of the experimental lubricants completed the 200-hour peak torque endurance test.

Data link interfaces are a very important part of the heavy duty vehicle industry; sharing information between subsystems is vital. SAE Recommended Practices J1708, J1587 and J1922 were developed to provide standards for proprietary communications, general information sharing, diagnostic definition and early powertrain controls. The industry realized, however, that these standards would not accomplish the ultimate goal-that of a high speed control and communications network. The development of more capable serial data communications for the heavy duty vehicle industry was prompted by the following: the desire of component suppliers to integrate subsystems for improved performance; the advancement of technology; customer expectations; and government regulations.

Corrosive wear of non-ferrous engine components by lubricants is a concern of all major heavy duty diesel engine manufacturers since warranty on key engine components has been extended to 500,000 miles. Several commercial lubricants have been linked to premature cam and rod bearing failures induced by corrosion in certain fleets. Although the overall failure rate is low, specific fleets have experienced significantly higher failure rates due to the lubricants used. These failures usually occur at high mileages but less than 500,000 miles. This kind of slow corrosion easily escapes detection of engine tests contained in current oil specifications, and it represents a serious issue in long term warranty cost to diesel engine manufacturers. A comprehensive fleet database has been established to identify the most corrosive lubricants. These lubricants have served as reference oils to develop a corrosion bench test.

An engine rig test and a scuffing BOCLE test have been used to investigate the lubricity of low sulfur diesel fuels and its relationship with unit injector wear in heavy duty diesel engines. The rig test effectively ranks 11 selected fuels/fluids according to their actual performance. The scuffing BOCLE test correlates with the rig test by showing the same ranking capability, and it is easy to perform. A similar correlation has been established using ISO reference fuels. The scuffing BOCLE test has been used to study 37 fuels randomly sampled from the field. The data shows that there is indeed a reduction in lubricity of low sulfur fuels. The variation in lubricity of low sulfur fuels is also much greater than high sulfur fuels. Data in this study shows that transition from good to poor lubricity usually occurs between 2500 to 3000 grams in the scuffing BOCLE.

Reports of disabling diesel engine seal failures which accompanied the introduction of low sulfur diesel fuel in October '93 prompted an in-depth survey of diesel fuel chemical and physical properties. The purpose of the survey was to anticipate other possible problems which might arise with the newly introduced low sulfur fuels. The survey will produce a database containing over 1000 number 2 diesel fuels from various parts of the US. About 75% of the samples tested were on-highway low sulfur diesel fuels. Samples analyzed were from the D-A Lubricant Company, Cummins customers failures (truck fleets of various sizes), and a number of retail fueling stations. Properties under investigation are % Sulfur, Cloud/Pour Points, Viscosity, API Gravity, TAN/TBN, Boiling Range, Aromatics content, Heat Content, Lubricity, and Peroxide number.

The EPA Heavy Truck Driveby Noise test is used to regulate trucks over 10,000 pounds GVW. The EPA test procedure is based on SAE J366. The EPA/J366 procedure is used both as a regulatory compliance tool and as a development tool. When the test procedure is used as a development tool, the goal is to determine the most cost effective means of meeting the legal requirement. Since J366 was not intended as a development tool, it can be difficult or misleading to use it to make decisions on product configuration. In order to use J366 successfully in vehicle or engine development, one must understand and properly account for the inherent variability of the J366 driveby test procedure. This paper examines both the extent and some of the sources of J366 driveby test variability. Strategies are proposed to ensure the proper interpretation of test results. Several repeat tests are required to accurately determine a small change in driveby noise level.

The ability of a piston oil ring to conform to liner distortions during engine operation is directly related to its radial stiffness. The ability to conform is also very important for controlling lubricant oil consumption and emissions. This paper describes the procedure utilized to investigate the technical feasibility of using flexible high performance engineering plastics to replace metal as base material for oil rings. Bench tests and engines were used to select and evaluate different types of plastics for wear resistance and structural integrity. Engine test results indicated no structural failures but wear levels were found to be unacceptably high for use in durable heavy duty diesel engines.

Diesel engine builders are faced with a new challenge to lower the weight of engines to increase payload while meeting rigorous durability goals for the engine. Cooling system parts represent a family of components which may be converted to lightweight metallic alloys for significant weight savings. To utilize lightweight alloys, cooling system parts must be engineered to maintain the same durability as the cast iron components they replace. For a modern high speed diesel, the Bl0 design life may be upwards of 1,280,000 kilometers which is a very aggressive target for a new component design. A test program was planned to guide design and development of aluminum (Al) cooling system parts for a new engine. The part must exhibit no corrosion after long duration operating with acceptable coolant. This program included three major phases consisting of bench scale corrosion tests for alloy selection, component rig tests for design verification and engine testing for system reliability.

Evolving diesel engine design trends are expected to include fuel systems operating at significantly higher pressures and temperatures than in the past. Accordingly, meaningful laboratory tests are needed to help guide this development. Two candidate test methods were evaluated in this exploratory study. Scuffing Load Ball-on Cylinder Lubricity Evaluator (BOCLE) and Modified High-Frequency Reciprocating Rig (HFRR) test results covering a range of operating temperatures were compared with fuel property data. Correlations of the Modified HFRR test data with BOCLE results were also made.

High Velocity Oxygen Fuel sprayed face coatings have shown great promise for piston rings used for High Power Density Diesel Engines. Various coatings have been tested on both wear test rigs and in engines. A highly dense HVOF cermet coating was developed with reasonable crack resistance during service. The HVOF coated piston rings wore three to six times lower than chrome plating. Cylinder liner (counter face) wear was found to be one to three times higher than chrome. However, engine oil consumption and blow by were within normal values. The HVOF coating is considered to be an excellent replacement for chrome plating. The coating process is more environmentally friendly than the chrome plating process. Also, the coating has potentially lower or equivalent production cost when compared to chrome.

A laboratory method has been developed to rank the scuff resistance of piston ring coatings. This method employs a standard wear test apparatus with a specially designed sample holder. Scuff resistance of electrolytic chrome, thermal spray and physical vapor deposition (PVD) face coatings have been examined. Based on this method, examined PVD coatings produced the highest scuff resistance of all the tested face coatings.

Compression rings for heavy duty diesel engines are traditionally made of ductile cast iron material. These rings, in general, have conservative standard dimensions limited by the strength of their base material. More recently, however, the market for heavy duty diesel engines demanded products able to cope with high levels of power density and, at the same time, lower levels of oil consumption, friction, and emissions. This paper discusses the advantages of some radical changes made on the design of compression rings in order to take advantage of steel as the base material. The superior mechanical properties of steel allow the use of rings with smaller cross sections which minimizes the friction losses caused by the combustion gas pressure pushing the ring against the liner. It also allows the use of compression rings with a free gap significantly larger than usual.

This paper examines the feasibility of using the boundary element method (BEM) and the Rayleigh integral to assess the sound radiation from engine components such as oil pans. Two oil pans, one cast aluminum and the other stamped steel, are used in the study. All numerical results are compared to running engine data obtained for each of these oil pans on a Cummins engine. Measured running-engine surface velocity data are used as input to the BEM calculations. The BEM models of the oil pains are baffled in various ways to determine the feasibility of analyzing the sound radiated from the oil pan in isolation of the engine. Two baffling conditions are considered: an infinite baffle in which the edge of the oil pan are attached to an infinite, flat surface; and a closed baffle in which the edge of the oil pan is sealed with a rigid structure. It is shown that either of these methods gives satisfactory results when compared to experiment.

Laboratory tests have shown that 40% glass-reinforced PPS is suitable for automotive underhood use where it comes into contact with used engine oil, gasoline/alcohol, gasoline/MTBE, water, water/ethylene glycol, hydraulic fluid, and transmission fluid at elevated temperatures. On exposure to water or water/ethylene glycol at 248° F (120° C) and 257°F (125°C), respectively, there is a sharp decline in mechanical strength in the first few weeks with little change thereafter. The residual strength of the 40% glass-reinforced PPS is comparable to, or better than other materials, such as phenolics, which have proved satisfactory in such usage. These results have been translated to successful applications in heavy duty diesel engines. Piston cooling nozzles and water pump impellers made of 40% glass-reinforced PPS have undergone successful engine component evaluations.

There has been an accelerated growth in power of diesel engines in United States line haul trucking. This paper analyzes the effect of high power on engine-related operating variables that occur under different highway conditions and dissimilar terrain features. When properly applied, high-powered diesel engines can increase average vehicle speed and/or fuel economy.