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Technical Paper

Exhaust Characteristics of the Automotive Diesel

1966-02-01
660550
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.
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

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

1996-02-01
960317
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

Tribological Investigations for an Insulated Diesel Engine

1983-02-01
830319
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

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

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

Effects of Injection Timing and Exhaust Gas Recirculation on Emissions from a D.I. Diesel Engine

1981-10-01
811234
Some results of a systematic study on the effects of injection timing retard and exhaust gas recirculation on emissions from a D.I. diesel engine are presented. The factors investigated include engine speed, fuel rate, injection timing, injection pressure, intake charge oxygen concentration, and type of diluent. The detailed mechanisms governing the formation and control of nitric oxide are studied analytically, using a previously developed diesel combustion model based on transient fuel-air mixing and Zeldovich nitric oxide reaction mechanisms. The results show that exhaust gas recirculation and injection timing retard are both effective in reducing nitric oxide emissions at the expense of increasing smoke. The reduction of nitric oxide with exhaust gas recirculation and injection timing retard is mainly related to the decrease of local temperature and local atomic oxygen concentration.
Technical Paper

Collection and Characterization of Particulate and Gaseous-Phase Hydrocarbons in Diesel Exhaust Modified by Ceramic Particulate Traps

1987-02-01
870254
Protocols for sampling and analysis of particulate and gaseous-phase diesel emissions were developed to characterize the chemical and biological effects of using ceramic traps as particulate control devices. A stainless-steel sampler was designed, constructed, and tested with XAD-2 sorbent for the collection of volatile organic compounds (VOC). Raw exhaust levels of TPM and SOF and mutagenicity of the SOF and VOC were all reduced when the traps were used. Hydrocarbon mass balances indicated that some hydrocarbons were not collected by the sampling system and that the proportions of collected SOF and VOC were altered by the use of the traps. SOF hydrocarbons appeared to be derived mainly from engine lubricating oil; VOC hydrocarbons were apparently fuel-derived. There was no apparent effect on SOF mutagenicity due to either sampling time or reexposure of particulate to exhaust gases.
Technical Paper

Testing Procedures for Introduction of Silicon Carbide and Carbon Water Pump Seal Faces into Heavy Duty Diesel Service

1993-03-01
930585
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.
Technical Paper

The Effects of Emulsified Fuels and Water Induction on Diesel Combustion

1970-02-01
700736
Water was inducted with the intake air and injected emulsified with the fuel, in a conventional single cylinder D.I. diesel engine. The major effects of inducted water were an increase in ignition delay, and reduction in the oxides of nitrogen and smoke at a constant fuel/air ratio. When the water was emulsified with the fuel, the ignition delay increased so much that no benefits were obtained except for a reduction in smoke. The results are compared to a similar study on an engine with the “M” combustion system. The major differences between the results obtained with the two combustion systems are attributed to the differences in the ignition delay caused by the water addition.
Technical Paper

Design Factors That Affect Diesel Emissions

1971-02-01
710484
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.
Technical Paper

Smoke Reduction in Diesel Engines

1967-02-01
670224
Black smoke is composed of free carbon or soot in an otherwise transparent exhaust stream. This paper discusses the factors responsible for smoke formation, the measurement of smoke, causes of excessive smoke on the highway, and the effect of fuel on smoke formation. Finally the role of smoke suppressant additives is described.
Technical Paper

Cooling Higher Horsepower Highway Diesel Engines

1975-02-01
750131
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.
Technical Paper

Wind Tunnel Investigation of the Effects of Installation Parameters on Truck Cooling System Performance

1976-02-01
760832
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.
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

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

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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