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Technical Paper

Cummins K-Series Engines

New heavy-duty diesel engines of 6-, 8-, 12-, and 16-cyl rated 75 hp/cyl turbocharged and 100 hp/cyl turbocharged and aftercooled are being developed. Design and development objectives include maximizing engine durability/reliability and use of common parts in all engine models. Fuel consumption, smoke, exhaust gas emissions, and engine noise equal or better than the best current engines within engine configurations readily adaptable to current automotive and construction equipment are also prime considerations. Initial models of the engine series meet the design and development objectives.
Technical Paper

Design Aspects of Low-Noise Diesel Engines

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.
Technical Paper

Tribological Investigations for an Insulated Diesel Engine

A Minimum Cooled Engine (MCE) has been successfully run for 250 hours at rated condition of 298 kW and 1900 rpm. This engine was all metallic without any coolant in the block and lower part of the heads. Ring/liner/lubricant system and thermal loading on the liner at top ring reversal (TRR) as well as on the piston are presented and discussed. Ring/liner wear is given as well as oil consumption and blow-by data during the endurance run. Another engine build with a different top ring coating and several lubricants suggested that a 1500 hours endurance run of MCE is achievable. Rig test data for screening ring materials and synthetic lubricants necessary for a successful operation of a so-called Adiabatic Engine with the ring/ceramic liner (SiN) interface temperature up to 650°C are presented and discussed.
Technical Paper

An Evaluation of the Lucas Combustion Noise Meter on Cummins ‘B’ Series Engines

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.
Technical Paper

Test Cell Simulation of the Driveby Noise Test

Diesel engine manufacturers have traditionally done most engine noise development work under steady: state operating conditions. However, truck driveby noise tests are acceleration tests, and engines exhibit different noise behavior under accelerating conditions. Acceleration noise can be affected by engine performance parameters which may have no influence on steady state noise levels. In this study, a test cell simulation of the truck driveby procedure has been developed and evaluated. Test cell simulation and truck driveby results are compared for a naturally-aspirated and a turbocharged engine. This simulation procedure has been shown to predict reliably results measured in vehicles. As a result, the simulation can be used to evaluate engine modifications during the development process without requiring a vehicle installation.
Technical Paper

Combustion Chamber Insulation Effect on the Performance of a Low Heat Rejection Cummins V-903 Engine

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.
Technical Paper

A Transient Spray Mixing Model for Diesel Combustion

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.
Technical Paper

The Influence of Bowl Offset on Air motion in a Direct Injection Diesel Engine

The influence of bowl offset on motored mean flow and turbulence in a direct injection diesel engine has been examined with the aid of a multi-dimensional flow code. Results are presented for three piston geometries. The bowl geometry of each piston was the same, while the offset between the bowl and the cylinder axis was varied from 0.0 to 9.6% of the bore. The swirl ratio at intake valve closing was also varied from 2.60 to 4.27. It was found that the angular momentum of the air at TDC was decreased by less than 8% when the bowl was offset. Nevertheless, the mean (squish and swirl) flows were strongly affected by the offset. In addition, the distribution of turbulent kinetic energy (predicted by the k-e model) was modified. Moderate increases (10% or less) in mass averaged turbulence intensity at TDC with offset were observed. However, the TDC turbulent diffusivity was changed less than 3% due to a slight decrease in turbulent length scale with increasing offset.
Technical Paper

The Effect of Raising Specific Output of a Highly Rated DI Diesel Truck Engine on its Performance and Emissions

A study was undertaken to establish what happens to engine emissions, and to turbocharger and injection pressure requirements, as the specific output is raised. For any given engine package, increasing specific output increases injection pressures while reducing air/fuel ratios. Thus, if the highly rated engine must satisfy the same design constraints, then raising the engine operating torque by only 10% resulted in more than 30% increase in total particulates! However, the same emission levels may be maintained if increases in specific output are accompanied by changes to engine design so as to maintain the air-fuel mixing parameters, specifically air/fuel ratio and injection pressures, throughout the entire engine operating conditions.
Technical Paper

Combustion Chamber Component Analysis for Advanced Heavy Duty Diesel Engines

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.
Technical Paper

A Preliminary Model for the Formation of Nitric Oxide in Direct Injection Diesel Engines and Its Application in Parametric Studies

A semiempirical, mathematical model describing the formation of nitric oxide in direct-injection diesel engines is derived. The model is used in conjunction with injection and thermodynamic cycle simulation programs. This approach enables prediction of nitric oxide emissions from design dimensions and operating parameters only, without the use of experimental data. Predicted results are compared with experiments for typical naturally aspirated and turbocharged engines. The accuracy of prediction is very good except under light-load naturally aspirated conditions. The model is used in an extensive parametric study, together with experimental verification. The agreement between prediction and experiments is excellent, except under conditions of excessive smoke or of high swirl.
Technical Paper

Diesel Engine Noise Reduction Hardware for Vehicle Noise Control

A range of noise reduction hardware is described for three production engine models, as well as the rationale for selecting noise reduction methods. Noise reductions up to 6 dB(A) were achieved with this hardware in the test cell. In many cases the modifications are more effective in vehicles. The success of the hardware in reducing overall vehicle noise is illustrated.
Technical Paper

Diesel Engine Component Design Using the Finite Element Method and Interactive Graphics

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.
Technical Paper

Evaluation of Microalloyed Steel for Articulated Piston Applications in Heavy Duty Diesel Engines

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.
Technical Paper

Vechicle Testing of Cummins Turbocompound Diesel Engine

Two turbocompound diesel engines were assembled and dynamometer tested in preparation for vehicle tests. Both engines met the 1980 California gaseous emission requirement and achieved a minimum BSFC of .313 lb/bhp-hr and a BSFC at rated conditions of .323 lb/bhp-hr. These engines were then installed in Class VIII heavy-duty vehicles to determine the fuel consumption and performance characteristics. Fuel consumption testing showed a 14.8% improvement for the turbocompound engine in comparison to a production NTC-400 used as a baseline. The turbocompound engine also achieved lower noise levels, improved drive-ability, improved gradeability, and moderately increased engine retardation. The second turbocompound engine was placed in commercial service and accumulated 50,000 miles on a cross-country route without malfunction. Tank mileage revealed a 15.92% improvement over a production NTCC-400 which was operating on the same route.
Technical Paper

Comparison of Measured and Theoretical Inter-Ring Gas Pressure on a Diesel Engine

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.
Technical Paper

Cummins Light Truck Diesel Engine Progress Report, 2000

The Automotive Market in the United States is moving in the direction of more Light Trucks and fewer Small Cars. The customers for these vehicles have not changed, only their purchase decisions. Cummins has studied the requirements of this emerging market. Design and development of an engine system that will meet these customer needs has started. The engine system is a difficult one, since the combined requirements of a very fuel-efficient commercial diesel, and the performance and sociability requirements of a gasoline engine are needed. Results of early testing are presented which show that the diesel is possibly a good solution.
Technical Paper

Experimental Measurements on the Effect of Insulated Pistons on Engine Performance and Heat Transfer

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.
Technical Paper

Techniques of Structural Vibration Analysis Applied to Diesel Engine Noise Reduction

This paper presents several techniques used to define quantitatively the problem of excessive noise through engine structural vibration. These techniques include both operating engine tests and bench tests. In addition, analytical techniques are shown which give a better understanding of how the critical components within the engine cause this vibration. Through the use of analytical and experimental techniques, examples illustrate practical solutions for diesel engine noise reduction.
Technical Paper

Crankshaft Design Using a Generalized Finite Element Model

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.