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Technical Paper

Why are NCI Pistons Not Used in Heavy Duty Diesel Engines?

In order to meet the strict exhaust emission legislation and customer's requirements of high power, heavy-duty diesel engines have to have a higher peak firing pressure and higher thermal load recently. It causes serious influence on the reliability and durability of the engines and engine parts, pistons in particular. The pistons for the next generation heavy-duty diesel engines are required to withstand more than 20 MPa of the peak firing pressure and higher thermal load, productivity of course. Nodular cast iron (NCI) pistons are one of the answers that could satisfy the requirements mentioned above. It is well known that NCI pistons have a lot of advantages but not popular. The difficulty of the casting technology and the quality control are the major reasons. Hino P11C engine has adopted it and kept it under mass production since 1991 and approx.20000 units of total production volume without any troubles.
Technical Paper

Windage Tray Design Comparison Using Crankcase Breathing Simulation

The conflicting requirements of better fuel economy, higher performance and lower emissions from an automobile engine have brought many new challenges that require development teams to look beyond conventional test and seek answers from simulations. One of the relatively unexplored areas of development where frictional losses haven't been completely understood is the flow in the crankcase. Here computational engineering can play a significant role in analyzing flow field in a hidden and complex region where otherwise testing has serious limitations. Flow simulation in the crankcase poses significant complexity and provides an opportunity to enhance the understanding of underlying physics by using multi-physics analyses tools available commercially. In this study, air space under the piston and above the oil level in oil pan is simulated. It is known that bay-to-bay breathing and windage holes account for considerable amount of power losses in the crankcase.
Technical Paper

Work Extraction Efficiency in a Series Hybrid Opposed Piston Engine

This work investigates the development of a novel series hybrid architecture utilizing a single cylinder opposed piston engine. The opposed piston engine presents unique benefits in a hybrid architecture such as its lower heat transfer due to a favorable surface area to volume ratio and lack of a cylinder head, as well as the thermodynamic benefits of two stroke operation with uniflow scavenging. A particular focus of this effort is the work extraction efficiency of two design concepts. The first design concept utilizes a geartrain to couple the crankshafts of the engine in a conventional manner, providing a single power take-off for coupling to an electric motor/generator. In this design, the large inertia of the geartrain dampens the speed fluctuation of the single cylinder engine, reducing the peak torque required to for the electric machine. However, the friction losses caused by the geartrain limit the maximum work extraction efficiency.
Technical Paper

Working Fluid Properties Variation During Combustion in Premixed Charge Hydrogen Engines

Several studies have been performed to investigate the effects of using hydrogen in spark ignition (SI) engines. One general conclusion that emerged was that stoichiometric operation of premixed charge hydrogen engines features increased losses compared to other fuels such as methane. Most studies attribute this higher loss to increased rates of heat transfer from the working fluid to the combustion chamber walls. Indeed, heat flux measurements during combustion and expansion recorded much higher values for hydrogen compared to methane stoichiometric operation. With regard to fluid properties, using the same net heat release equation as for gasoline engines results in an over prediction of heat losses to the combustion chamber walls. Also, the variation of specific heats ratio greatly influences calculated values for the rate of heat release. Therefore, a more detailed analysis of heat losses is required when comparing hydrogen to other fuels.
Technical Paper

World Wide Escort/Lynx Engine Design and Development

In 1981, Ford Motor Company introduced a new family of fuel efficient four cylinder engines world wide. These engines, based on a compound valve arrangement in a hemispherical combustion chamber, were specifically designed for installation in light weight front-wheel-drive vehicles. Ford Research efforts were integrated with the resources of Ford U.S. and Ford of Europe to design and develop the engine in a compressed time frame. The technical and organizational efforts to accomplish this task, as well as, the design and development are discussed.
Technical Paper

Zero-Dimensional Spark Ignition Combustion Modeling - A Comparison of Different Approaches

Internal combustion engines development with increased complexity due to CO2 reduction and emissions regulation, while reducing costs and duration of development projects, makes numerical simulation essential. 1D engine simulation software response for the gas exchange process is sufficiently accurate and quick. However, combustion simulation by Wiebe function is poorly predictive. The objective of this paper is to compare different approaches for 0D Spark Ignition (SI) modeling. Versions of Eddy Burn Up, Fractal and Flame Surface Density (FSD) models have been coded into GT-POWER platform, which connects thermodynamics, gas exchange and combustion sub-models. An initial flame kernel is imposed and then, the flame front propagates spherically in the combustion chamber. Flame surface is tabulated as a function of piston position and flame radius. The modeling of key features of SI combustion such as laminar flame speed and thickness and turbulence was common.
Technical Paper

a universal means for Rating Diesel Engines for Deposits and Wear

THE NEW CRC Diesel Engine Rating Manual is intended to furnish a universal language for identification of diesel-engine deposits and wear. Diesel-engine pistons are evaluated for lacquer deposits by utilizing an area demerit basis and color gradations of brown and gray from clean to black. In studying various means for evaluating thickness and texture of deposit in oil systems, it was decided that the scratch gage developed by the CRC Engine Deposit Rating Panel of the CRC-Motor Engine Varnish and Sludge Group was suitable for diesel engines. A procedure for establishing a volume factor which furnishes a weighted interpretation of the deposit was created.*
Technical Paper

p>Thermomechanical Analysis of the Cylinder Head and Cylinder Block with the Liner of AFV Diesel Engine

This paper deals with the Coupled thermo mechanical analysis of a cylinder head, cylinder block and crank case with the liner of an uprated engine. The existing engine develops 780 hp output with mechanical driven supercharger and the engine is uprated to 1000 hp by replacing the supercharger with a turbocharger and new Fuel injection equipment. For uprating any engine, the piston and cylinder head are the most vulnerable members due to increased mechanical and thermal loadings. Mechanical loading is due to the gas pressure in the gas chamber and its magnitude can be judged in terms of peak pressure. Thermal loading is due to temperature and the heat transfer conditions in the piston surface, cylinder liner and the cylinder head. The relative importance of the various loads applied on the head and cylinder block in operation are assessed and a method of predicting their influence on the structural integrity of the components described.
Technical Paper

the identification and characterization of RUMBLE AND THUD

SIMULTANEOUS RECORDINGS of cylinder pressure, audible sound, and crankshaft motion have shown that rumble is a noise associated with bending vibrations of the crankshaft. The vibrations are caused by abnormally high rates of pressure rise near the top dead center piston position. In this study the high rates of pressure rise were obtained by inducting deposits into the the engine. Thud is a torsional vibration of the crankshaft, similar in sound to rumble but resulting from much earlier occurrence of the maximum rates of pressure rise. Rumble vibrations consisted of a fundamental frequency of 600 cps and higher harmonics in the 11/1 compression ratio V-8 laboratory engine used in the investigation. The audible noise of rumble was predominantly composed of the second harmonic or about 1200 cps.
Technical Paper

λDSF: Dynamic Skip Fire with Homogeneous Lean Burn for Improved Fuel Consumption, Emissions and Drivability

Dynamic skip fire (DSF) has shown significant fuel economy improvement potential via reduction of pumping losses that generally affect throttled spark-ignition (SI) engines. In DSF operation, individual cylinders are fired on-demand near peak efficiency to satisfy driver torque demand. For vehicles with a downsized-boosted 4-cylinder engine, DSF can reduce fuel consumption by 8% in the WLTC (Class 3) drive cycle. The relatively low cost of cylinder deactivation hardware further improves the production value of DSF. Lean burn strategies in gasoline engines have also demonstrated significant fuel efficiency gains resulting from reduced pumping losses and improved thermodynamic characteristics, such as higher specific heat ratio and lower heat losses. Fuel-air mixture stratification is generally required to achieve stable combustion at low loads.
Technical Paper

“Hot Tube Test”-Analysis of Lubricant Effect on Diesel Engine Scuffing

To prevent engine scuffing in the field a new laboratory test called the Hot Tube Test has been established in order to evaluate the high temperature stability of diesel engine oils. In a strip mining application field test using 47 bulldozers powered by the same engine type, half of the engines suffered from piston scuffing failures when operated on a variety of commercially available API CD quality SAE 30 Grade engine oils. All the field test oils have been investigated using the Hot Tube Test, and an analysis of the results indicates that it would be possible to accurately predict scuffing failures by this test method. Furthermore, the reliability of this analysis has been verified by bench engine testing on reference oils. The reasons why the Hot Tube Test predicts the anti-scuffing performance of engine oils are discussed.
Technical Paper

“Influence of Engine Variables on Exhaust Oxides of Nitrogen Concentrations from a Multi-Cylinder Engine”

The influence of engine variables on the concentration of oxides of nitrogen present in the exhaust of a multicylinder engine was studied. The concentrations of nitric oxide (NO) were measured with either a mass spectrometer or a non-dispersive infrared analyzer. The NO concentration was low for rich operation (deficient in oxygen) and increased with air-fuel ratio to a peak value at ratios slightly leaner than stoichiometric proportions. A further increase in air-fuel ratio resulted in reduced NO concentrations. Advanced spark timing, decreased manifold vacuum, increased coolant temperature and combustion chamber deposit buildup were also found to increase exhaust NO concentration. These results support either directly or indirectly the hypothesis that exhaust NO concentration is primarily a result of the peak combustion gas temperature and the available oxygen.