Search Results

This paper presents a study of lubricating oil transport and exchange in a four-stroke spark ignition engine while undergoing transient load changes. The study consisted of experiments with a single cylinder test engine utilizing 2D LIF (Two Dimensional Laser Induced Fluorescence) techniques to view real time oil transport and exchange, along with computer modeling to describe certain phenomenon observed during the experiments. The computer modeling results included ring dynamics and corresponding gas flows through different regions of the power cylinder. Under steady-state conditions and constant speed during the experiments, more oil was observed on the piston at low load than at high load. Therefore, a transition from low load to high load resulted in oil leaving the piston, and a transition from high load to low load resulted in oil being added to the piston.

This paper presents a model for the lubrication and friction between a twin land oil control ring and the liner within an engine cycle. This model is based on the deterministic method, which considers micro geometry of the liner finish and its effects on both hydrodynamic lubrication and asperity contact. In this particular application, the liner surface micro features are solely responsible for hydrodynamic pressure generation due to the flat face profile of a typical twin land oil control ring, contrasting to the traditional average model where ring surface macro geometry is most important in generating hydrodynamic pressure.

A dry piston secondary dynamics model has been developed. This model includes the detailed piston and cylinder bore hot shape geometries, and piston deformations due to combustion pressure, axial inertia and interaction with the cylinder bore, but neglects the effects of the hydrodynamic lubrication at the piston - cylinder bore interface in order to achieve faster calculation times. The piston - cylinder bore friction is calculated using a user supplied friction coefficient. This model provides a very useful, fast tool for power cylinder system analysis, provided its limitations are understood.

A general deterministic hydrodynamic lubrication model [1] was modified to study the interaction between a Twin Land Oil Control Ring (TLOCR) and a liner with cross-hatch liner finish. Efforts were made to customize the general model to simulate the particular sliding condition of TLOCR/liner interaction with proper boundary conditions. The results show that model is consistent, robust, and efficient. The lubricant mass conservation was justified and discussed. Then analysis was conducted on the lubricant transport between the deep grooves/valleys and plateau part of the surface to illustrate the importance of deep grooves in oil supply to the plateau part and hydrodynamic pressure generation. Furthermore, since the TLOCR land running surface is completely flat and parallel to the nominal liner axis, the liner finish micro geometry is fully responsible for the hydrodynamic pressure rise, which was found to be sufficient to support significant portion of the total ring radial load.

This paper discusses the influences of several cylinder liner honing surface geometrical features on the interaction between the piston twin land oil control ring (TLOCR) and the cylinder liner by using the deterministic hydrodynamic model [1] and the twin land oil control ring model [2]. Additionally, the key design parameters of the TLOCR, including ring tension and land axial width are studied. The results show significant effects of three liner honing surface features beyond height distribution, including plateau wavelength, groove density and honing angle in hydrodynamic pressure generation. The study in oil control ring design parameters reveals that both ring tension and land axial width have important influences on friction and oil consumption, and their competing effects are discussed subsequently.

This paper presents the follow up to previous work done by Przesmitzki and Tian [1] studying large increases in blow-by in a spark ignition engine during transient load changes. This study examines the sensitivity of such blow-by spikes to differing intake pressures, and the time spent under both high and low intake pressure. The study consisted of experiments with a single cylinder test engine utilizing 2D LIF (Two Dimensional Laser Induced Fluorescence) techniques to view real time oil transport and exchange, along with computer modeling to explain certain phenomenon observed during the experiments. The previous work found that a very large blow-by spike could occur upon a transition from low engine load to a high engine load. The hypothesis was the top ring groove was being filled with oil during low engine load. Thereafter, it was hypothesized a transition to high load resulted in radial collapse of the top ring, and the subsequent blow by spike.

Engine oil consumption is recognized to be a significant source of pollutant emissions. Unburned or partially burned oil in the exhaust gases contributes directly to hydrocarbon and particulate emissions. In addition, chemical compounds present in oil additives poison catalytic converters and reduce their conversion efficiency. Oil consumption can increase significantly during critical non-steady operating conditions. This study analyzes the oil consumption behavior during ramp transients in load by combining oil consumption measurements, in-cylinder measurements, and computer-based modeling. A sulfur based oil consumption method was used to measure real-time oil consumption during ramp transients in load at constant speed in a production spark ignition engine. Additionally in-cylinder liquid oil behavior along the piston was studied using a one-point Laser-Induced-Fluorescence (LIF) technique.

As a part of the effort to comply with increasingly stringent emission standards, engine manufacturers strive to minimize engine oil consumption. This requires the advancement of the understanding of the characteristics, sources, and driving mechanisms of oil consumption. This paper presents a combined theoretical and experimental approach to separate and quantify different oil consumption sources in a production spark ignition engine at different speed and load conditions. A sulfur tracer method was used to measure the dependence of oil consumption on engine operating speed and load. Liquid oil distribution on the piston was studied using a Laser-Induced-Fluorescence (LIF) technique. In addition, important in-cylinder parameters for oil transport and oil consumption, such as liner temperatures and land pressures, were measured.

A model was developed to study engine oil vaporization and oil vapor transport in the piston ring pack of internal combustion engines. With the assumption that the multi-grade oil can be modeled as a compound of a number of distinct paraffin hydrocarbons, a set of equations governing the oil vapor density variations were derived by applying mass conservation law to the amount of oil vaporized from the piston and the amount of oil vapor transported within the piston ring pack. The model was applied to a heavy-duty diesel engine. First, the case with the maximum oil supply to all the piston regions was studied. The results showed that, under this condition, the oil consumption from piston vaporization alone was far greater than the typical oil consumption value measured in the engine.

The lubrication of the piston ring-pack is directly related to the engine friction and oil consumption. Non-axisymmetric characteristics of the power cylinder system, most noticeably cylinder bore distortion, piston secondary motion, and ring gaps, can introduce circumferential variations to ring/liner lubrication and overall performance of the ring-pack in friction and oil consumption. In order to be able to optimize the piston ring-pack in a more fundamental way, it is necessary to develop physical understanding of the effects of these non-axisymmetric properties and effective numerical tools. In this study, a comprehensive model has been developed for the lubrication of a piston ring-pack. By employing a finite element analysis, this model is capable of evaluating the in-plane structural response of a ring to external forces. A newly developed one-dimensional hydrodynamic lubrication sub-model is implemented to calculate the lubrication force at each cross-section.

Faced with increasing concern for lubricating oil consumption and engine friction, it is critical to understand the oil transport mechanisms in the power cylinder system. Lubricating oil travels through distinct regions along the piston ring pack before being consumed in the combustion chamber, with the oil distribution and dominant driving forces varying substantially for each of these regions. In this work, the focus is on the lowest region in the piston ring pack, namely the third land, which is located between the second compression ring and the oil control ring. A detailed 2D LIF (Two Dimensional Laser Induced Fluorescence) study has been performed on the oil distribution and flow patterns of the third land throughout the entire cycle of a single cylinder spark ignition engine. The impact of speed and load were experimentally observed with the LIF generated real time high-resolution images, as were changes in piston and ring design.