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A prior study (Chon and Heywood, [1]) examined how the design and performance of spark-ignition engines evolved in the United States during the 1980s and 1990s. This paper carries out a similar analysis of trends in basic engine design and performance characteristics over the past decade. Available databases on engine specifications in the U.S., Europe, and Japan were used as the sources of information. Parameters analyzed were maximum torque, power, and speed; number of cylinders and engine configuration, cylinder displacement, bore, stroke, compression ratio; valvetrain configuration, number of valves and their control; port or direct fuel injection; naturally-aspirated or turbocharged engine concepts; spark-ignition and diesel engines. Design features are correlated with these engine’s performance parameters, normalized by engine and cylinder displacement.

The challenge posed by the long run times necessary to accurately quantify ash effects on diesel aftertreatment systems has led to numerous efforts to artificially accelerate ash loading, with varying degrees of success. In this study, a heavy-duty diesel engine was outfitted with a specially designed rapid lubricant degradation and aftertreatment ash loading system. Unlike previous attempts, the proposed methodology utilizes a series of thermal reactors and combustors to simulate all three major oil consumption mechanisms, namely combustion in the power cylinder, evaporative and volatile losses, and liquid losses through the valve and turbocharger seals. In order to simulate these processes, each thermal reactor allows for the precise control of the level of lubricant additive degradation, as well as the form and quantity of degradation products introduced into the exhaust upstream of the aftertreatment system.

The effects of the directed port flow produced by a Charge-Motion-Control-Valve (CMCV) on mixture preparation in a Port-Fuel-Injection engine were assessed under conditions typical of fast idle in a cold start process. The port fuel was found to comprise two components: a “valve” puddle (at the vicinity of the valve) that built up quickly, and that was mainly responsible for the delivery of the fuel to the cylinder charge; a “port” puddle located significantly upstream. The latter was mainly created by the reverse back flow process and built up slowly. Although the fuel amounts in these two components were roughly the same, the latter did not significantly interact with the fuel transport to the cylinder charge. The CMCV only weakly affected the purging or filling time of the valve puddle, hence the dynamics of the fuel delivery process was not materially affected.

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.

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.

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.

Liquid fuel flow into the cylinder an important source of hydrocarbon (HC) emissions of an SI engine. This is an especially important HC source during engine warm up. This paper examines the phenomena that determine the inflow of liquid fuel through the intake valve during a simulated start-up procedure. A Phase Doppler Particle Analyzer (PDPA) was used to measure the size and velocity of liquid fuel droplets in the vicinity of the intake valve in a firing transparent flow-visualization engine. These characteristics were measured as a function of engine running time and crank angle position during four stroke cycle. Droplet characteristics were measured at 7 angular positions in 5 planes around the circumference of the intake valve for both open and closed-valve injection. Additionally the cone shaped geometry of the entering liquid fuel spray was visualized using a Planar Laser Induced Fluorescence (PLIF) setup on the same engine.

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.

A spark-ignition engine friction model developed by Patton et al. in the late 1980s was evaluated against current engine friction data, and improved. The model, which was based on a combination of fundamental scaling laws and empirical results, includes predictions of rubbing losses from the crankshaft, reciprocating, and valvetrain components, auxiliary losses from engine accessories, and pumping losses from the intake and exhaust systems. These predictions were based on engine friction data collected between 1980 and 1988. Some of the terms are derived from lubrication theory. Other terms were derived empirically from measurements of individual friction components from engine teardown experiments. Recent engine developments (e.g., improved oils, surface finish on piston liners, valve train mechanisms) suggested that the model needed updating.

In an effort to both increase engine efficiency and generate new, consistent, and reliable data useful for the development of engine concepts, a modern single-cylinder 4-valve spark-ignition research engine was used to determine the response of indicated engine efficiency to combustion phasing, relative air-fuel ratio, compression ratio, and load. Combustion modeling was then used to help explain the observed trends, and the limitations on achieving higher efficiency. This paper analyzes the logic behind such gains in efficiency and presents correlations of the experimental data. The results are helpful for examining the potential for more efficient engine designs, where high compression ratios can be used under lean or dilute regimes, at a variety of loads.

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.

In this paper, a previously developed and experimentally-validated piston secondary motion model has been improved further numerically and applied to understand the detailed interactions between the piston skirt and cylinder liner for various piston design parameters. The model considers the roughness of the surfaces and the topography of the skirt in both the axial (barrel profile) and circumferential directions (ovality). Three modes of lubrication: hydrodynamic, mixed, and boundary lubrication regimes have been considered and the skirt is partially flooded in most cases. Elastic deformation of the skirt is an essential part of the model. In this model, the piston dynamic behavior, frictional and impact forces are predicted as functions of crank angle and are examined in detail. Parameters investigated include piston skirt profile, piston to liner clearance, surface roughness, and oil availability.

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.

As part of ongoing research on hydrogen-enhanced lean burn SI engines, this paper details an experimental combustion system optimization program. Experiments focused on three key areas: the ignition system, in-cylinder charge motion produced by changes in the inlet ports, and uniformity of fuel-air mixture preparation. Hydrogen enhancement is obtained with a H2, CO, N2 mixture produced by a fuel reformer such as the plasmatron. The ignition system tests compared a standard inductive coil scheme against high-energy discharge systems. Charge motion experiments focused on the impact of different flow and turbulence patterns generated within the cylinder by restrictor plates at the intake port entrance, as well as novel inlet flow modification cones. The in-cylinder fluid motion generated by each configuration was characterized using swirl and tumble flow benches. Mixture preparation tests compared a standard single-hole pintle port fuel injector against a fine atomizing 12-hole injector.

The flow into and out of the piston top-land crevice of a spark-ignition engine has been studied, using a square-cross-section single-cylinder engine with two parallel quartz glass walls which permit optical access to the entire cylinder volume. Schlieren short-time exposure photographs and high speed movies were used to define the essential features of this flow. The top-land crevice and the regions behind and between the rings consist of volumes connected through the ring gaps. A system model of volumes and orifices was therefore developed and used to predict the flow into and out of the crevice regions between the piston, piston rings and cylinder wall.

The way In which combustion chamber geometry affects combustion in SI engines was studied using a quasi-diraensional cycle simulation. Calculations were performed to investigate the following questions: (i) the sensitivity of geometric effects on combustion to engine operating conditions; (ii) the differences in burn duration between ten chamber geometries and spark plug locations; and (iii) the relative merits of improved chamber design and amplified turbulence as means to reduce burn duration. The results from these studies are presented and discussed.

In analyzing the processes inside the cylinder of an internal combustion engine, the principal diagnostic at the experimenter's disposal is a measured time history of the cylinder pressure. This paper develops, tests, and applies a heat release analysis procedure that maintains simplicity while including the effects of heat transfer, crevice flows and fuel injection. The heat release model uses a one zone description of the cylinder contents with thermodynamic properties represented by a linear approximation for γ(T). Applications of the analysis to a single-cylinder spark-ignition engine, a special square cross-section visualization spark-ignition engine, and a direct-injection stratified charge engine are presented.

This paper reviews the major changes that have occurred in spark-ignition engine design and operation over the last two decades. The automobile air pollution problem, automobile emission standards, and automobile fuel economy standards -- the factors which have and are producing these changes -- are briefly described. The major components in spark-ignition engine emission control systems are outlined, and advances in carburetion, fuel injection, ignition systems, spark retard and exhaust gas recycle strategies, and catalytic converters, are reviewed. The impact of these emission controls on vehicle fuel economy is assessed. The potential for fuel economy improvements in conventional spark-ignition engines is examined, and promising developments in improved engine and vehicle matching are outlined.

Difficulties in the starting and operation of diesel engines at low temperatures are an important consideration in their design and operation, and in selection of the fuels for their use. Improvements in operation have been achieved primarily through external components of the engine and associated subsystems. A Rapid Compression Machine (RCM) has been modified to operate over a wide range of temperatures (−20°C to 100°C). It is used to isolate the combustion chamber in an environment in which all significant parameters are carefully defined and monitored. The influence of temperature and cetane number on the ignition and combustion processes are analyzed. Examination of the combustion characteristics show that temperature is by far the most influential factor affecting both ignition delay and heat release profiles. Cetane number (ASTM D-613) is not found to be a strong indicator of ignition delay for the conditions investigated.