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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.

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.

Cavitation corrosion is a very complex phenomenon that is governed by a formidable amount of factors and parameters. The phenomenon is a multi-disciplinary one which involves several aspects of physical sciences and engineering. This process is a slow progressive phenomenon with its detrimental effects being felt after severe damage has already occurred. A real time detection method for the severity of fluid cavitation and bubble collapse is described. The results are correlated to dynamic instantaneous pressure fluctuation measurements. The method is fast, reliable, and less restrictive of the sensing location. It has been tested and verified through a specially designed cavitation test rig and instrumentation setup. The method can be used for cavitation studies on ultrasonic bench rig tests and for cavitation measurements on running engines. The method was used to shed some light on characteristic cavitation differences between water and glycol which is used in engine coolants.

Testing procedures to evaluate new coolant pump seal face materials and new coolant pump seal designs were evaluated. Rig testing of materials and seals followed by engine dynamometer testing enabled changes in the seal materials or design to be validated prior to field testing and limited production. These procedures were used to test and implement a coolant pump seal face material change to silicon carbide versus carbon. The change resulted in higher reliability for the coolant pump seal and reduced warranty cost for the engine.

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.

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.

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.

RAPID CORROSIVE WEAR OF COPPER ALLOYS caused by a friction reducing additive was encountered in field tests of experimental lubricants. This oil soluble molybdenum, sulphur, and phosphorous containing additive subsequently was used in several commercial heavy duty diesel lubricants although the additive manufacturer did not recommend it for such applications. Numerous engine failures occurred due to the aggressiveness of this additive toward copper. Standard laboratory engine test methods or standard bench test methods did not predict the severe field problem. A new laboratory engine test method has been shown to duplicate the field failures. Bench test methods to duplicate the field failures are discussed. The mode of failure is shown and described.

Joint development of the adiabatic engine by Cummins Engine Company and the U. S. Army began with a feasibility analysis ten years ago. The effort was initially driven by the expectation of substantial performance improvement, a reduction in cooling system size, and several additional benefits. Program emphasis turned quickly to experimentation with the goal of demonstrating the feasibility of the adiabatic engine in working hardware. Several significant achievements were realized as have been reported earlier. Further development of the adiabatic engine is expected to be more evolutionary, paced by available technology in the areas of materials and tribology. Analysis capability necessary for insulated engine development has been found to be inadequate. Additional effort has gone into the development and validation of insulated engine analysis tools, both for cycle simulation and structural modeling.

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.

Fundamental aspects of performance and regeneration of a porous ceramic particulate trap are described. Dimensionless correlations are given for pressure drop vs. flow conditions for clean and loaded traps. An empirical relationship between estimated particulate deposits and a loading parameter that distinguishes pressure drop changes due to flow variations from particulate accumulation is presented. Results indicate that trapping efficiencies exceed 90% under most conditions and pressure drop doubles when particulate accumulation occupies only 5% of the available void volume. Regeneration was achieved primarily by throttling the engine intake air. For various combinations of initial loading level, trap inlet temperature and oxygen concentration, it was found that regeneration rate peaked after 45 seconds from initiation.

The effect of eight installation and component parameters on cooling system heat rejection and air flow were examined in detail in a wind tunnel facility. A quarter-replicate, two level factorial test plan was followed. Within the ranges of each parameter tested, the fan characteristics and the projection of fan into the shroud are highly significant parameters. The fan to radiator distance, the radiator characteristics, and the fan tip to shroud clearance are significant parameters. The fan to engine block distance and the type of shroud are not significant parameters.

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.

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.

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.

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.

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.

A series of comparative evaluation tests to determine the effect of various full-flow and combination full-flow and bypass filter systems on diesel engine piston ring and crankshaft bearings was made using radioactive tracer wear measurement and component weight loss techniques. The results of these tests indicate that bypass lube oil filtration combined with good full-flow lube oil filtration result in lowest engine wear rate and lowest total cost for the engine user.

The production of pollutants and an increasing need for pollution management are an inevitable concomitant of a society with a high standard of living. The automotive diesel engine is used more than any other type of engine for transporting freight over highways. Two kinds of pollution to be considered with regard to the diesel engine are the dark exhaust smoke and odor, of which the public is quite cognizant, and the less obvious but possibly toxic carbon monoxide, oxides of nitrogen, unburned hydrocarbons, and trace compounds of other toxic materials. This paper discusses sampling, measurement techniques, and established standards for exhaust smoke and odor. Examination of diesel exhaust shows it to be less offensive in terms of harmful effects than the invisible exhaust from other types of engines. The major problem is exhaust color and odor.