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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.

Piston rings are large contributors to friction losses in internal combustion engines. To achieve higher engine efficiency, low friction ring packs that can maintain good sealing performance must be designed. To support this effort, simulation tools have been developed to model the performance of piston rings during engine operation. However, the challenge of predicting oil consumption, blow by, and ring pack friction with sufficient accuracy remains. This is mostly due to the complexity of this system. Ring dynamics, deformation, interaction with liner and piston, gas and lubricant flow must all be studied together to make relevant predictions. In this paper, a new curved beam finite element model of piston rings is proposed. Ring structural deformation and contact with the liner are treated on two separate grids. A comparison with ring models in the literature and analytical solutions shows that it can provide accurate results efficiently.

A flame sheet model for NO production in multi-dimensional diesel simulation has been developed. It explicitly addresses that because of the finite computational cell resolution, the local temperature within the diffusion flame is substantially higher than the cell averaged temperatures. Thus using the latter values will under-predict NO production. The methodology uses a flame sheet library for the NO production. Computations using this model are compared to experimental data for a Cummins N14 engine. The results show that the NO production is predominantly from within the flame sheets; the bulk production accounts for less than 5% of the total production.

A model for calculating the residual gas fraction in spark ignition engines has been formulated. The model accounts explicitly for the contribution due to the back flow of exhaust gas to the cylinder during the valve overlap period. The model has been calibrated with in-cylinder hydrocarbon measurements at different values of intake pressure, engine speed, and valve overlap timings.

The use of hydrogen as a fuel supplement for lean-burn engines at higher compression ratios has been studied extensively in recent years, with good promise of performance and efficiency gains. With the advances in reformer technology, the use of a gaseous fuel stock, comprising of substantially higher fractions of hydrogen and other flammable reformate species, could provide additional improvements. This paper presents the performance and emission characteristics of a gas mixture of equal volumes of hydrogen, CO, and methane. It has recently been reported that this gas mixture can be produced by reforming of ethanol at comparatively low temperature, around 300C. Experiments were performed on a 1.8-liter passenger-car Nissan engine modified for single-cylinder operation. Special pistons were made so that compression ratios ranging from CR= 9.5 to 17 could be used. The lean limit was extended beyond twice stoichiometric (up to lambda=2.2).

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 novel engine management strategy for achieving fast catalyst light-off without the use of an exhaust air pump in a port-fuel-injected, spark ignition engine was developed. A conventional 4-cylinder engine was operated with three cylinders running rich and the fourth one as an air pump to supply air to the exhaust manifold. Under steady-state cold coolant conditions, this strategy achieved near total oxidation of CO and HC with sufficiently retarded spark timing, resulting in a 400% increase in feedgas enthalpy flow and a 90% reduction in feedgas HC emissions compared to conventional operation. The strategy was also evaluated for crank starts. Using the existing engine hardware, implementing the strategy resulted in a reduction in catalyst light-off time from 28.0 seconds under conventional operation to 9.1 seconds.

As the piston pin works under significant mechanical load, it is susceptible to wear, seizure, and structural failure, especially in heavy duty internal combustion engines. It has been found that the friction loss associated with the pin is comparable to that of the piston, and can be reduced when the interface geometry is properly modified. However, the mechanism that leads to such friction reduction, as well as the approaches towards further improvement, remain unknown. This work develops a piston pin lubrication model capable of simulating the interaction between the pin, the piston, and the connecting rod. The model integrates dynamics, solid contact, oil transport, and lubrication theory, and applies an efficient numerical scheme with second order accuracy to solve the highly stiff equations. As a first approach, the current model assumes every component to be rigid.

This paper presents a numerical model of the rotational and lateral dynamics of the piston (secondary motion) and piston slap in mixed lubrication. Piston dynamic behavior, frictional and impact forces are predicted as functions of crank angle. The model considers piston skirt surface waviness, roughness, skirt profile, thermal and mechanical deformations. The model considers partially-flooded skirt and calculates the pressure distributions and friction in the piston skirt region for both hydrodynamic and boundary lubrication. Model predictions are compared with measurements of piston position using gap sensors in a single-cylinder engine and the comparison between theory and measurement shows remarkable agreement.

A twin-land oil control ring (TLOCR) model is used to evaluate TLOCR friction and the results are compared to the experiment measurement in a single cylinder floating liner engine under motoring condition. The model is based on a correlation between the hydrodynamic pressure and film thickness, which is generated using a deterministic model. The well-known three-regime lubrication is predicted with the model for ring with different ring tensions under various engine running conditions. A good match is found for the model and experiment results.

The increasingly stringent regulations for fuel economy and emissions require better optimization and control of oil consumption. One of the primary mechanisms of oil consumption is vaporization from the liner; we consider this as the “minimum oil consumption (MOC).” This paper presents a physical-mathematical cycle model for predicting the MOC. The numerical simulations suggest that the MOC is markedly sensitive to oil volatility, liner temperature, engine load and speed but less sensitive to oil film thickness. A one-line correlation is proposed for quick MOC estimations. It is shown to have <15% error compared to the cycle MOC computation. In the “dry region” (between top ring and OCR at the TDC), oil is depleted due to high heat and continual exposure to the combustion chamber.

A complete one-dimensional mixed lubrication model has been developed to predict oil film thickness and friction of the piston ring-pack. An average flow model and a roughness contact model are used to consider the effects of surface roughness on both hydrodynamic and boundary lubrication. Effects of shear-thinning and liner temperature on lubricant viscosity are included. An inlet condition is applied by considering the unsteady wetting location at the leading edge of the ring. A ‘film non-separation’ exit condition is proposed to replace Reynolds exit condition when the oil squeezing becomes dominant. Three lubrication modes are considered in the model, namely, pure hydrodynamic, mixed, and pure boundary lubrication. All of these considerations are crucial for studying the oil transport, asperity contact, and friction especially in the top dead center (TDC) region where the oil control ring cannot reach.

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.

The oil control ring (OCR) controls the supply of lubricating oil to the top two rings of the piston ring pack and has a significant contribution to friction of the system. This study investigates the two most prevalent types of OCR in the automotive market: the twin land oil control ring (TLOCR) and three piece oil control ring (TPOCR). First, the basis for TLOCR friction on varying liner roughness is established. Then the effect of changing the land width and spring tension on different liner surfaces for the TLOCR is investigated, and distinct trends are identified. A comparison is then done between the TLOCR and TPOCR on different liner surfaces. Results showed the TPOCR displayed different patterns of friction compared the TLOCR in certain cases.

An adaptive air/fuel ratio controller for SI engine throttle transient was developed. The scheme is based on an event- based, single- parameter fuel dynamics model. A least- square- error algorithm with an active forgetting factor was used for parameter identifications. A one- step- look- ahead controller was designed to maintain the desired air/fuel ratio by canceling the fuel dynamics with the controller setting updated adaptively according to the identified parameters. When implemented on a Ford Ztech engine and tested under a set of throttle- transient operations, the adaptive controller learned quickly and performed well.

The paper presents a detailed study of a unique lubricating oil transport and exchange path that is important for friction, wear, and oil consumption in a 4 stroke spark ignition engine, namely the oil flow from the piston to the cylinder liner. The study consisted of experiments with a test engine utilizing 2D LIF (Two Dimensional Laser Induced Fluorescence) techniques to view real time oil transport and exchange, along with computer modeling. The effects of engine speed, load, and oil ring design were included as part of the research. The test conditions ranged from 800 RPM to 4500 RPM, while the load was varied from closed throttle to wide open throttle. Several different oil control ring designs were utilized, including U-Flex, Twin-Land, and 3-Piece. Oil transport and exchange from the piston to the liner was observed under several different engine conditions, typically moderate to high engine speeds and low loads.

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.

The piston skirt is an important contributor of friction in the piston assembly. This paper discusses friction contributions from various aspects of the piston skirt. A brief study of piston skirt patterns is presented, with little gains being made by patterning the piston skirt coating. Next the roughness of the piston skirt coating is analyzed, and results show that reducing piston skirt roughness can have positive effects on friction reduction. Finally, an introductory study into the profile of the piston skirt is presented, with the outcome being that friction reduction is possible by optimizing the skirt profile.

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 an important source of hydrocarbon and particulate emissions in automotive engines. Oil evaporating from the piston-ring-liner system is believed to contribute significantly to total oil consumption, especially during severe operating conditions. This paper presents an extensive experimental and theoretical study on the contribution of oil evaporation to total oil consumption at different steady state speed and load conditions. A sulfur tracer method was used to measure the dependence of oil consumption on coolant outlet temperature, oil volatility, and operating speed and load in a production spark ignition engine. Liquid oil distribution on the piston was studied using a one-point Laser-Induced-Fluorescence (LIF) technique. In addition, important in-cylinder variables for oil evaporation, such as liner temperature and cylinder pressure, were measured. A multi-species cylinder liner oil evaporation model was developed to interpret the oil consumption data.