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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.

Previous work on the cooling jackets of the Cummins L10 engine revealed flow separation, and low coolant velocities in several critical regions of the cylinder head. The current study involved the use of detailed cooling jacket temperature measurements, and finite element heat transfer analysis to attempt the identification of regions of pure convection, nucleate boiling, and film boiling. Although difficult to detect with certainty, both the measurements and analysis pointed strongly to the presence of nucleate boiling in several regions. Little or no evidence of film boiling was seen, even under very high operating loads. It was thus concluded that the regions of seemingly inadequate coolant flow remained quite effective in controlling cylinder head temperatures. The Cummins L10 upon which this study has focused is an in-line six cylinder, four-stroke direct injection diesel engine, with a displacement of 10 liters.

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.

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.

The increased use of on-board and off-board electronic systems with medium duty and heavy duty trucks and buses presents challenges with compatibility and proper integration. The vehicle architecture is taking shape to establish three areas of computer control-the powertrain, the cab instrument panel, and the cab operations center. The critical element of pursuing proper integration of these systems requires established and clear standards and test methods. Clear roles and responsibilities, a defined system architecture and common test methods are required between subsystem electronic product suppliers and vehicle manufacturers. The electronics integration challenges are presented in the context of the U.S. medium duty and heavy duty automotive industry but have broad applicability to other heavy vehicles and markets worldwide. SAE and ISO forums are needed to address these issues.

The development of smoke measurement procedures and instruments has been one of the significant factors contributing to the reduction of smoke from diesel-powered trucks. There is a need, however, for better information on the relation between measurements and the appearance of the smoke plume, for improved smokemeters, and for common international test procedures. Studies of smoke plumes using jet theory, alumina tracer, and hydraulic analog techniques indicate that the plumes are sometimes unstable and subject to large-scale shedding in the region where free-plume smokemeters are located. This introduces a significant random variation into smoke measurements made in this location. A future test procedure based on smoke measurements made with a long path (500 mm) in-line smokemeter during a dynamic cycle is suggested for consideration. Smoke limits would be based on tests similar to those conducted by MIRA to relate smoke levels and engine size to human response.

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.

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.

Until recently, dry cargo has been unloaded from trucks by use of compressed air. By making the automotive engine act partly as an air compressor during the unloading operation, the auxiliary air compressor mounted on the tractor frame can be eliminated. This paper, in describing the dual diesel, discusses operating characteristics, cycle analysis, and operational problems.

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.

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.

Some results of a systematic numerical study of the effects of injection characteristics on the transient evaporating spray mixing process in a diesel like environment are presented. The study uses an existing two-dimensional stochastic thick spray model. It was found that, for a fixed injection quantity, changes in the nozzle hole number, nozzle hole size, and injection duration changed significantly the evaporation and mixing processes of a transient evaporating spray. In particular, It is found that, for a fixed nozzle geometry, reduced injection duration is most effective in increasing the mixing rate. The results also show that the injection rate shape greatly influences the mixing process of a transient spray, especially during the injection period. After the end of injection, the global effect of injection rate shape can be characterized by the mass averaged injection pressure alone. The higher the mass averaged injection pressure, the faster the mixing rate.

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.

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 new technique has been developed to allow engine performance engineers to visualize and communicate a wide range of thermodynamic issues and constraints in a single diagram. The technique, called Visual Thermodynamics, is the presentation of engine cycle data in logarithmic pressure and logarithmic temperature space, log(p)-log(T). Visual Thermodynamics is a thought organization and concept visualization tool. It is not intended to provide high-precision numerical results. The utility of the technique is in comparing engine concepts, assessing trends, identifying boundaries of operation and building a general understanding of engine system behavior. The technique provides a powerful mechanism for communicating engine thermodynamic issues to both technical and non-technical colleagues.