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Technical Paper

Cavitation Intensity Measurements for Internal Combustion Engines

1996-02-01
960884
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.
Technical Paper

Real Time Captivation Detection Method

1996-02-01
960878
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.
Technical Paper

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

1996-10-01
961909
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

Effect of Fuel Composition and Altitude on Regulated Emissions from a Lean-Burn, Closed Loop Controlled Natural Gas Engine

1997-05-01
971707
Natural gas presents several challenges to engine manufacturers for use as a heavy-duty, lean burn engine fuel. This is because natural gas can vary in composition and the variation is large enough to produce significant changes in the stoichiometry of the fuel and its octane number. Similarly, operation at high altitude can present challenges. The most significant effect of altitude is lower barometric pressure, typically 630 mm Hg at 1600 m compared to a sea level value of 760 mm. This can lower turbocharger boost at low speeds leading to mixtures richer than desired. The purpose of this test program was to determine the effect of natural gas composition and altitude on regulated emissions and performance of a Cummins B5.9G engine. The engine is a lean-burn, closed loop control, spark ignited, dedicated natural gas engine. For fuel composition testing the engine was operating at approximately 1600 m (5,280 ft) above sea level.
Technical Paper

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

1989-02-01
890263
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

Performance and Regeneration Characteristics of a Cellular Ceramic Diesel Particulate Trap

1982-02-01
820272
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.
Technical Paper

Modeling of Transient Evaporating Spray Mixing Processes-Effect of Injection Characteristics

1984-02-01
840226
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.
Technical Paper

Visual Thermodynamics: Processes in Log(p)-Log(T) Space

1999-03-01
1999-01-0516
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.
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