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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.

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.

This work evaluates the thermal and structural integrity of a heavy duty diesel piston using finite element analysis. The effects of aluminum, ductile iron, and superalloy piston materials; air gaps; and plasma-sprayed zirconia coating on piston temperature and stress, as well as on heat flux through the piston, are assessed. The coating lowered the heat flux through the piston 56 percent and caused other changes in the piston to have an insignificant effect on the heat flux. The air gaps had the least effect on heat flux with substantially lower safety margins than pistons without air gaps.

Warranty data can be a useful, accurate, and timely information source for monitoring the reliability of a product. At Cummins Engine Company a warranty based reliability information system was developed for diesel engines that has the capability to 1) evaluate the reliability of engines and their components, 2) compare the reliability performance of engines and components to goals and prioritize those areas needing improvement, and 3) detect changes in the warranty claims pattern of engine components to provide early warning of potential problems. This paper will describe this warranty data system with emphasis on the analytical tools used to perform the above activities. Although many of the examples refer to diesel engines, the general concepts apply to the use of warranty data for many types of products.

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.

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.

Diesel engine operation under high load conditions (>45 hp/cyl) may result in piston “debond” in which the Ni-resist ring carrier separates from the aluminum piston matrix leading to destruction of the piston. Historically, engine loads have increased to achieve higher power densities which together with more stringent emissions requirements have resulted in greatly increased stress levels in the piston. The higher stresses have resulted in debond failure. The design of the ring carrier will affect debond failure. Deformation of the ring carrier will initiate debond at the back of the insert at the junction with the piston matrix. The ring carrier cross-section must be made robust enough through proper design to achieve expected reliability. Another factor influencing ring carrier retention is the quality of the AlFin bond layer. Casting defects which arise from the AlFin bonding process, degrade the strength of the joint leading to failure.

Tests were conducted with several production diesel engines and one prototype low-emission diesel engine to determine the effect of fuel properties on exhaust emissions and engine performance. Fuel cetane number was found to be the most significant fuel property; low cetane fuels resulted in higher hydrocarbons and oxides of nitrogen and increased noise. Conversely, higher cetane fuels produced lower emissions and noise, and also improved engine starting characteristics. The degree of these effects was influenced by engine configuration. Although engine design changes can result in substantial emissions reduction, fuel properties can also influence achieveable levels.

The specific goal of this project was to determine if there is a difference in the lube oil degradation rates in a heavy-duty diesel engine equipped with an EGR system, as compared to the same configuration of the engine, but minus the EGR system. A secondary goal was to develop FTIR analysis of used lube oil as a sensitive technique for rapid evaluation of the degradation properties of lubricants. The test engine selected for this work was a Caterpillar 3176 engine. Two engine configurations were used, a standard 1994 design and a 1994 configuration with EGR designed to meet the 2004 emissions standards. The most significant changes in the lubricant occurred during the first 50-100 hours of operation. The results clearly demonstrated that the use of EGR has a significant impact on the degradation of the engine lubricant.

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.

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 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.

Measurements of instantaneous temperature were made at three locations on the cylinder head of a direct injection diesel engine. Changes in calculated instantaneous heat flux with changes in cylinder head surface temperature were assessed. The results were used in an assessment of various approaches to the description of instantaneous heat transfer incorporated in diesel cycle simulations. It was concluded that changes in the thermal boundary layer thickness throughout the cycle could account for some of the observed phenomena. A close correlation was seen between the heat transfer measured here and earlier published studies of measured boundary layer thickness. Some additional indications from the measurements point to a significant thermal capacitance of the boundary layer. Additional work is needed to further understand the potential ramifications of this effect.

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.

This paper documents the successful operation of a modified Cummins T46 turbocharger with a ceramic rotor. This turbocharger is modified to incorporate a 4.6 inch diameter ceramic turbine rotor (pressureless sintered silicon nitride) on the hot end. These results document the most complete ceramic turbine rotor performance map, for a large ceramic turbocharger rotor, available to date.

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.

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.

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.