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Both the automotive and truck industry are facing further regulated emissions legislation in the near future. Understanding the emissions and fuel consumption attributes of an engine/vehicle application during a drive cycle early in an engine development program is a critical step to steer the engine development program to a successful final product. The generally accepted approach is to calibrate an engine on a dynamometer and to adjust the operation of the engine to meet performance targets. With the current build and test approach, these adjustments may not be made until well into the development program, and this calibration is a costly and time consuming step in the engine development process.

A novel mechanism using a moving rocker pivot has been developed by Motive Engineering. The chosen approach offers variation of lift, duration, and phase. A compact, robust proof-of-concept mechanism has been designed, and fabricated. It was fitted to the intake valvetrain of a production SOHC four-cylinder engine. The operation of the mechanism is described. A longer-duration, higher-lift camshaft was designed to explore the potential benefits of the concept throughout the speed and load range. Dynamometer testing has been done to explore possible benefits to power, fuel economy, and exhaust emissions.

A dynamic simulation of a school bus powertrain has been constructed for the purpose of assisting in the development of engine control strategies. With some extensions, this model can also be used as a first approximation to support the development of transmission shift control strategies, predict vehicle performance and drivability as well as estimate transient loads on the powertrain components. The simulation was constructed using the Matlab* computing environment along with the Simulink* toolbox, a package for the graphical development of dynamic simulation models. The vehicle model was validated against test data measured in the target vehicle powered by a natural gas engine to ensure that the simulation model yielded sensible predictions of the dynamic powertrain behavior. Equipped with a validated model, the control engineer can now use the simulation tool to assist in algorithm development. Sample applications are illustrated.

Engine tests were conducted on a production 2.5-liter V-6 engine to investigate the effects of spark plug tip designs on a 4-cycle SI engine of current technology. The data suggest that cyclic variation can increase when the ground electrode faces the primary intake port. Lean-operation limits were extended by the use of J-gap spark plugs as compared to surface-gap and ring-gap spark plugs at the conditions tested. The surface-gap type spark plugs lose some energy as the arc traverses the surface of the insulator. Voltage requirements decrease for reversed polarity at the part load conditions tested but increase at wide open throttle.

A transient spray mixing model forming the basis of heterogeneous combustion in direct injection diesel engines is described. Experimental results of transient fuel sprays in a high pressure, high temperature chamber form the basis of spray growth equations. Use of similarity of concentration profile across the spray in conjunction with spray geometry and mass conservation yields a complete description of spatial and temporal fuel-air distribution. Fuel preparation and air entrainment rates are calculated from the history of fuel-air distribution. Progressive evolution of combustion zones is determined by the fuel-air mixing process. Energy conservation and chemical kinetics calculations in each zone yield cylinder pressure and local nitric oxide concentration. The role of fuel-air mixing in diesel combustion is discussed. The model results are compared with experimental data.

Lucas Industries Noise Centre has introduced a combustion noise meter which is designed to predict the contribution of the combustion process to overall diesel engine noise. The performance of the meter is evaluated using Cummins B series engines in naturally-aspirated and turbocharged form. Combustion noise levels predicted by the meter are compared to levels determined using traditional techniques. The effects of several engine operating parameters on combustion noise are investigated under both steady state and accelerating conditions. The meter reliably predicts changes in combustion noise levels, and is a useful tool for performance development engineers. Combustion noise is shown to be related to the maximum rate of pressure rise at the onset of combustion, but combustion noise is not reliably related to maximum cylinder pressures.

Recent engine design trends towards increasing power, reducing weight, advancing of injection timing and increasing of injection rate and pressure could result in increased incidence of liner pitting. Liner pitting due to coolant cavitation is a complex function of many engine design parameters and operating conditions as described in reference [1]*. Traditionally, liner cavitation problems were not detected early in the development cycle. Traditional liner vibration and coolant pressure measurements in conjunction with a numerous amount of expensive engine endurance tests were then needed to resolve cavitation problems. A method newly developed by the author and described in reference [2] for cavitation intensity measurements was successfully utilized to map out engine operating condition and develop limit curves. This method could also be applied in a non intrusive fashion.

Detailed thermal analysis was conducted on several advanced cylinder head, liner, and piston concepts, for low heat rejection diesel engines. The analysis was used to define an optimized engine configuration. Results pointed to the strategic use of oil cooling and insulation in the cylinder head, an oil cooled cylinder liner, and an insulated piston, with separate insulation behind the compression rings. Such a configuration reduced in-cylinder heat rejection by 30 percent, while durability would be expected to be maintained or improved from today's production levels.

Cummins Engine Company is developing a low heat rejection 450 kW engine under contract for the US Army Tank & Automotive Command. This paper discusses progress made toward achieving the program goals of 6.6 kcal/kW-min brake specific heat rejection and 200 g/kW-hr brake specific fuel consumption. Methodology for measuring heat rejection on a low heat rejection engine is presented. Design improvements of the base engine are discussed along with their effect on improving fuel consumption. Performance test data is assessed in terms of the first law energy balance and cooling load distribution. The heat rejection data provides insights on the performance of insulating components and two cooling system designs. Diesel cycle simulations are compared to the test data and are used to predict the effect of ceramic insulation on engine heat rejection.

Inter-ring gas pressure and piston ring motion are considered important for the control of oil consumption, particulate emissions, and reduced friction. For this reason, inter-ring gas pressure was measured on a diesel engine. Two different ring pack configurations were tested (positive and negative twist second rings). A significant difference in measured inter-ring pressure was observed. The measurements were compared to the predictions of a cylinder kit model with favorable results. Predictions showed that the observed difference between measured inter-ring pressures is caused by a significant difference in ring motion. The reasons for these differences are explained in this paper.

The increase in power-to-weight ratio that results from the use of higher-horsepower diesel engines in highway service prompted this study of engine cooling. This paper covers the results obtained in testing different power-to-weight ratios on grades from sea level to over 11,000 ft and compares these results with those obtained from chassis and towing dynamometer cooling trials.

An analytical tool for the efficient analysis of crankshaft designs has been developed. Finite element models are generated from a limited number of key dimensions which describe a family of crankshafts. These models have been verified by stress and deflection measurements on several crankshaft throws.

This paper discusses a new approach to the finite element analysis of cylinder head gaskets. The new method is based on a feature of the ABAQUS® finite element solver which allows the user complete freedom to define unique material properties. This is an attractive option for cylinder head gasket analysis because the user has the freedom to describe materials which are non-linear and anisotropic. There is also the possibility of specifying independent loading and unloading characteristics. To ensure repeatability and avoid errors, the new method includes a user-friendly program to automate the input deck preparation procedure. In addition to offering new capabilities, the new method was found to converge more quickly than the current gasket analysis method.

Methods of reducing the noise level of a diesel engine include the suppression of the major modes of block vibration and treatment of the external surfaces. Design methods enable the frequencies and noise levels of these modes to be calculated for a conventionally designed engine. The important modes of vibration, the noise signature and the effect of block modifications of a standard production V-8 engine were found by experiments. These provided the basis for the design of an experimental low-noise engine. Design features include a suffer block, removal of the bottom part of the crankcase skirt, the addition of a single bearing beam, and the use of isolated panels and damped surfaces. The noise reduction obtained was 9 dBA. Most of this is due to the use of isolated and damped nonload carrying surfaces.

Although diesels, as a group, are a relatively small source of air pollutants, emissions standards which limit emissions from diesels have been adopted by California and the federal government. Test procedures and instrumentation for measuring diesel emissions have been developed, and an understanding of how engine design parameters affect emissions is evolving. Smoke and carbon monoxide are primarily functions of fuel-air ratio. Smoke is also affected by injection timing, air motion, and fuel spray characteristics. Hydrocarbon emissions are most affected by details of injector design and matching of the spray geometry with the combustion chamber shape. Nitric oxide emissions are controlled by local oxygen availability in regions of high temperature and residence time at the high temperature.

An inexpensive, flexible and convenient finite element analysis system can be implemented with limited capital and resources. A system of this nature can be a functional tool of the designer and stress analyst for the analysis of many types of mechanical components. The finite element models generated by this system can approach a high degree of complexity with a small time investment compared to the time required to do this job without the aid of the system described.

The cambore distortion is one of major concerns of an engine performance. A good design does not ensure a quality product. To meet product performance requirements, engineering community turns efforts to both design and manufacturing at an early stage of product development. This paper will discuss this process by providing an example of design and manufacturing of an overhead cambore. In this study a methodology to evaluate bore distortions is introduced. FEA cambore distortion analysis will use it to provide necessary data so that the product team can make a sound decision.

A flow and heat transfer model of an engine lubrication system has been developed in order to predict sump oil temperature and study heat transfer mechanisms within the lubricating oil circuit. The objective was to develop the capability of simulating all the energy transfers between the oil and the combustion process, the engine coolant, and the engine bay air. The model developed in this study simulates a V8 spark ignited engine. Included in this simulation is a bearing model for friction heat generation, a combustion heat input model, and component models for each key heat transfer site in the lubricating oil circuit. The model predicts sump oil temperatures under different engine operating conditions and simulation results were compared to test data with good agreement. The sensitivity of oil temperature to engine speed, engine load, coolant temperature, piston friction, bearing heat energy generation, piston design, water jacket depth, and oil flow rate(s) was studied.

AISI-4140H steel has been used as articulated piston crown material in heavy-duty engines. With the driving force for reducing manufacturing cost, microalloyed steel (MAS) was identified as a low-cost material to replace 4140H steel. In order to determine the feasibility of using MAS to replace 4140H steel, a test program was initiated to fully evaluate the material properties of MAS and to compare them to those of the baseline 4140H steel. The physical and mechanical properties of both materials from room temperature to 550°C were evaluated. The effect of long term thermal exposure on the material properties was also studied. Some engine tests were also conducted to evaluate the performance of the articulated pistons made with both materials. The inherently lower strength of MAS as compared to 4140H steel, requires a total re-design of the piston for the utilization of MAS as a low-cost replacement material for 4140H steel.

Data have been gathered to compare the performance of steel crown pistons coated with yttria stabilized zirconia or mullite to an uncoated piston. The effect of coated pistons on in-cylinder heat transfer was determined from curves of ISFC versus centroid of heat release. Error analysis of the measurements showed uncertainty of ± 3% in ISFC and ± 2 crank angle degrees in the centroid of heat release could be expected for the data. Particulate emissions increased at advanced injection timings with the mullite coated piston while the zirconia coated piston showed an increase in particulate and NOx at advanced timings.