Search Results

Lubrication networks in today's passenger car engines are complex systems managing the interactions between the manufacturers' demand for long engine-life, low friction characteristics and sufficient heat-transfer work of the lubricant. Modern engines work harder and run hotter and consequently place more demands on the engine oil and the design of the lubrication system. The paper presents an overview of the influences of various oil pump parameters as oil pump suction port, rotor geometry and oil pump component clearances on the engine's operating behavior. The results of detailed investigations, intended to design the oil pump capacity exactly to the requirements of the optimized lubrication system, are shown in combination with the analysis of the oil draining system, aimed to reduce the hydraulic losses. A potential is presented that engine manufacturer can obtain in terms of saving energy.

Despite progressively stricter emission regulations, the harmful effects on the environment resulting from internal combustion engine powered vehicles. especially in heavily populated urban areas, has increased. Alternative fuels, especially neat methanol, have new found importance due to their environmental benefits. Through a research program sponsored by the U.S. Environmental Protection Agency, a direct-injected (DI) methanol glow plug engine is being developed and integrated into a passenger car. The base engine for this project is a prototype DI diesel engine, which is currently under development by Volkswagen AG. The methanol DI engine displaces 1.9L and is equipped with a turbocharger, an intercooler, and exhaust gas recirculation (EGR). The engine demonstrates basically the same favorable efficiency of a small DI diesel engine in combination with very low NOx and particulate emissions.

A global awareness of internal combustion engine exhaust emissions has resulted in diesel engine manufacturers considering advanced engine technologies and the use of alternative fuels, such as methanol, to address this important issue. Within this paper, the continued development of a methanol engine, based upon the Navistar DT-466 diesel engine, is outlined. A hot surface ignition (glow plug) system is used to assist in methanol ignition allowing the methanol engine to produce favorable NOx and particulate emissions, without increased unburned fuel emissions, compared to the baseline diesel version. Performance and efficiency correspond to that of the diesel engine. In addition to fuel consumption and emissions behavior, the design features of the methanol engine, such as cylinder head modifications, hot surface ignition systems and the methanol fuel injection system are presented.

Ziel dieser experimentellen Arbeiten war es, das Zusammenwirken zwischen Motor und Katalysator bei stationärer und instationärer Betriebsweise zu untersuchen. Als Versuchsträger diente ein 4-Zylinder-Ottomotor (1,8 ltr.), der mit einer KE-Jetronic und Schubabschaltung ausgerüstet war. Um sowohl die Rohemission des Motors als auch die Umsatzrate des Katalysators beurteilen zu können, wurde eine Abgasanalyse vor und hinter dem Katalysator vorgenommen. Zur Beurteilung der Katalysatorbeanspruchung bei den verschiedenen Randbedingungen wurden die Temperaturen innerhalb des Katalysators an verschiedenen Meßstellen mit Thermoelementen erfaßt. Die Messungen erfolgten bei 4 unterschiedlichen Kennfeldpunkten, wobei im Instationärbetrieb, ausgehend von den Ausgangslasten, in den Schubbetrieb übergegangen wurde. Nach der Schubphase wurde wieder auf die Ausgangslast zurückgesprungen.

A computer program has been developed to simulate the operational behavior of turbocharged Diesel engines under transient conditions. The essential characteristics of this program which is based upon the filling and emptying model are presented. In particular, the code considers the waste gate behavior, the charge-air cooler and the component temperatures which vary during acceleration. A comparison between computed and measured response has been made for a turbocharged inter-cooled 4-cylinder swirl chamber Diesel engine. The code has also been used to assess improvements in the acceleration behavior which can be realized by a strongly reduced mass of inertia of the turbocharger rotors, lower friction of the bearings, variable geometry of the turbocharger turbine and heat insulation of the exhaust ports and the exhaust manifold.

Exhaust gas quality and efficiency of diesel combustion are primarily influenced by the mixture formation process during fuel injection. The first step in understanding the mechanisms of pollutant formation is analyzing the atomization, self-ignition and burning of the injected spray. This paper presents the details of a combustion chamber developed to inject fuel into quiescent air and allow air pressures to 60 bar (900 psi) and air temperatures to 600°C (1100°F). The special design enables four-sided optical access for the visualization of the diesel spray movement and self ignition zones by high speed photography including Schlieren techniques. For different injected fuels (diesel fuel, methanol and n-heptane) the ignition delay has been determined and the dependence on pressure and temperature are shown. At those positions where ignition occurs, measurements of the local air-fuel ratio have been performed with spontaneous Raman spectroscopy.

The loads which act upon the crankshaft are analyzed and its reactions are described. A typically and practically known calculation procedure for crankshafts is compared with various calculation procedures of classification societies and a draft from the CIMAC* working group “Crankshafts”. The CIMAC draft serves as basis for a standardization of design requirements of all classification societies which is currently under negotiation between the CIMAC and the IACS**. The differences among the calculation procedures are presented and evaluated. The need for a uniform calculation procedure accepted world-wide by all classification societies is shown. The possibilities opened by the availability of modern techniques in developing more detailed and thus more accurate calculation models are pointed out.

A mathematical equivalent model to describe the dynamic behaviour of mechanical actuated valve trains has been developed which is based on a multi-degrees-of-freedom vibratory system. It could be shown that dampings and stiffnesses efficient in a valve train are influenced by three oil film effects: these are squeeze films between the valve train components, elastohydrodynamic lubrication of cam and follower and the cam shaft bearings. Thus, the effective values for dampings and stiffnesses within the equivalent model are calculated with regard to these different kinds of oil film effects. The accuracy of the model is demonstrated by a comparison to measured forces and accelerations which were taken up on a pushrod-actuated valve train.

Using known approaches to describe the reaction kinetics of soot, simple models are formulated to calculate regeneration limits and describe the interaction between engine and filter. - Insulation of exhaust ports and manifold reduces the lower limit of automatic filter regeneration by approx. 0.5 bar bmep. - Intake throttling extends the range of automatic regeneration to within medium load. - The combination of intake throttling with a small constant output burner enables regeneration for all engine operating conditions. - Fuel additives can lower the limit for filter regeneration through lowering the activation energy to within the lower part load without additional measures.

Knowledge of flame propagation enables a more detailed description of the combustion processes as well as assessing the influences of engine operating conditions and design parameters, particularly in view of efficiency improvements and pollutant reduction. Flame propagation in a single-cylinder spark-ignition engine is studied by means of a measuring technique using lightconductors coupled with photo-multipliers. The propagation process is monitored through a large number of optical probes arranged in a matrix in the combustion chamber. The spatial flame contour, the flame volume, and the flame front velocity as a function of time are furnished from these measurements. The investigations show the formation of quench zones ("flame quenching") not penetrated by the flame directly above the piston towards the end of the expansion phase at extremely lean operating conditions.

Monolithic ceramic filters, suitable for reducing particulate emissions to within the 0,2 g/mile emissions limit, are intermittantly loaded and regenerated. A mathematical model was developed in order to describe the processes which take place in the filter during regeneration. The basis of the calculation model, such as reaction kinetics, heat and mass transfer, energy and mass balance, and flow performance are explained. Filter temperature, soot oxidation and exhaust flow behavior are described over the length of a filter channel. A calculated and measured regeneration sequence for an engine operating point near engine full load are illustrated and compared. The results show that due to the prevailing higher temperatures, an intensified soot oxidation occurs at the rear of the channel.