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Two different types of mesh used for diesel combustion with the KIVA-4 code are compared. One is a well established conventional KIVA-3 type polar mesh. The other is a non-polar mesh with uniform size throughout the piston bowl so as to reduce the number of cells and to improve the quality of the cell shapes around the cylinder axis which can contain many fuel droplets that affect prediction accuracy and the computational time. This mesh is specialized for the KIVA-4 code which employs an unstructured mesh. To prevent dramatic changes in spray penetration caused by the difference in cell size between the two types of mesh, a recently developed spray model which reduces mesh dependency of the droplet behavior has been implemented. For the ignition and combustion models, the Shell model and characteristic time combustion (CTC) model are employed.

Reactivity-controlled compression ignition (RCCI) has been shown to be capable of providing improved engine efficiencies coupled with the benefit of low emissions via in-cylinder fuel blending. Much of the previous body of work has studied the benefits of RCCI operation using high injection pressures (e.g., 500 bar or greater) with common rail injection (CRI) hardware. However, low-pressure fueling technology is capable of providing significant cost savings. Due to the broad market adoption of gasoline direct injection (GDI) fueling systems, a market-type prototype GDI injector was selected for this study. Single-cylinder light-duty engine experiments were undertaken to examine the performance and emissions characteristics of the RCCI combustion strategy with low-pressure GDI technology and compared against high injection pressure RCCI operation. Gasoline and diesel were used as the low-reactivity and high-reactivity fuels, respectively.

Technologies for improving the fuel economy of gasoline engines have been vigorously developed in recent years for the purpose of reducing CO2 emissions. Increasing the compression ratio for improving thermal efficiency and downsizing the engine based on fuel-efficient operating conditions are good examples of technologies for enhancing gasoline engine fuel economy. A direct-injection system is adopted for most of these engines. Direct injection can prevent knocking by lowering the in-cylinder temperature through fuel evaporation in the cylinder. Therefore, direct injection is highly compatible with downsized engines that frequently operate under severe supercharging conditions for improving fuel economy as well as with high compression ratio engines for which susceptibility to knocking is a disadvantage.

Technologies for improving the fuel economy of gasoline engines have been vigorously developed in recent years for the purpose of reducing CO2 emissions. Increasing the compression ratio is an example of a technology for improving the thermal efficiency of gasoline engines. A significant issue of a high compression ratio engine for improving fuel economy and low-end torque is prevention of knocking under a low engine speed. Knocking is caused by autoignition of the air-fuel mixture in the cylinder and seems to be largely affected by heat transfer from the intake port and combustion chamber walls. In this study, the influence of heat transfer from the walls of each part was analyzed by the following three approaches using computational fluid dynamics (CFD) and experiments conducted with a multi-cooling engine system. First, the temperature rise of the air-fuel mixture by heat transfer from each part was analyzed.

This paper describes the methods adopted to improve the image quality of the all-around view system. This system uses multiple vehicle-mounted cameras to capture images of the circumstances around the vehicle. The images undergo viewpoint transformation and are synthesized to create a single image seen from a virtual perspective overhead. The specific methods discussed here concern optimization of the design parameters for the camera orientation and a camera calibration method that does not involve physical movement of the cameras.

This paper investigates flow and combustion in a full-cycle simulation of a four-stroke, three-valve HCCI engine by visualizing the flow with pathlines. Pathlines trace massless particles in a transient flow field. In addition to visualization, pathlines are used here to trace the history, or evolution, of flow fields and species. In this study evolution is followed from the intake port through combustion. Pathline analysis follows packets of intake charge in time and space from induction through combustion. The local scalar fields traversed by the individual packets in terms of velocity magnitude, turbulence, species concentration and temperatures are extracted from the simulation results. The results show how the intake event establishes local chemical and thermal environments in-cylinder and how the species respond (chemically react) to the local field.

The effect of the ring pack storage mechanism on the hydrocarbon (HC) emissions from an air-cooled utility engine has been studied using a simplified ring pack model. Tests were performed for a range of engine load, two engine speeds, varied air-fuel ratio and with a fixed ignition timing using a homogeneous, pre-vaporized fuel mixture system. The integrated mass of HC leaving the crevices from the end of combustion (the crank angle that the cumulative burn fraction reached 90%) to exhaust valve closing was taken to represent the potential contribution of the ring pack to the overall HC emissions; post-oxidation in the cylinder will consume some of this mass. Time-resolved exhaust HC concentration measurements were also performed, and the instantaneous exhaust HC mass flow rate was determined using the measured exhaust and cylinder pressure.

A transport equation residual model incorporating refined G-equation and detailed chemical kinetics combustion models has been developed and implemented in the ERC KIVA-3V release2 code for Gasoline Direct Injection (GDI) engine simulations for better predictions of flame propagation. In the transport equation residual model a fictitious species concept is introduced to account for the residual gases in the cylinder, which have a great effect on the laminar flame speed. The residual gases include CO2, H2O and N2 remaining from the previous engine cycle or introduced using EGR. This pseudo species is described by a transport equation. The transport equation residual model differentiates between CO2 and H2O from the previous engine cycle or EGR and that which is from the combustion products of the current engine cycle.

The aim of this study is to gain a better understanding of the mechanism of knocking with respect to flame propagation behavior based on 3D simulations conducted with the Universal Coherent Flamelet Model. Flame propagation behavior under the influence of in-cylinder flow was analyzed on the basis of the calculated results and experimental visualizations. Tumble and swirl flows were produced in the cylinder by inserting various baffle plates in the middle of the intake port. A comparison of the measured and calculated flame propagation behavior showed good agreement for various in-cylinder flow conditions. The results indicate that in-cylinder flow conditions vary the flame propagation shape from the initial combustion period and strongly influence the occurrence of knocking.

The focus of this paper is to discuss the modeling and control of intake plenum pressure on the Powertrain Control Research Laboratory's (PCRL) Single-Cylinder Engine (SCE) transient test system using a patented device known as the Intake Air Simulator (IAS), which dynamically controls the intake plenum pressure, and, subsequently, the instantaneous airflow into the cylinder. The IAS exists as just one of many devices that the PCRL uses to control the dynamic boundary conditions of its SCE transient test system to make it “think” and operate as though it were part of a Multi-Cylinder Engine (MCE) test system. The model described in this paper will be used to design a second generation of this device that utilizes both continuously and discretely actuating valves working in parallel.

In-cylinder temperature and velocity fields were quantified simultaneously in an optically accessible, small-bore diesel engine. A technique utilizing luminescence from Pr:YAG phosphor particles aerosolized into the intake air was used for temperature determination while particle image velocimetry (PIV) on the aforementioned phosphor particles was used to simultaneously measure the velocity field. The temperature and velocity fields were measured at different points throughout the compression stroke up to −30 CAD. Systematic interference due to emission from the piston window reduced the accuracy of the measurements at crank angles closer to TDC. Single-shot simultaneous measurements of the temperature and velocity fields were made using both unheated and heated intake temperatures. In both cases, cycle-to-cycle variations in the temperature and velocity fields were visible.

It is generally known that NOx reacts with unburned gasoline, olefins in particular, to form sludge precursors. In this study, the authors investigated the process by which NOx and unburned gasoline mix into the engine oil and analyzed the mechanism whereby stop and go driving accelerates sludge formation. It has been found that NOx detected in the engine oil as nitrite ions mixes into the oil in the crankcase. The NOx concentration in the engine oil increases rapidly when the crankcase gas temperature is nearly equal to the dew point of the water vapor in the crankcase. Unburned gasoline is mainly absorbed into the oil through the oil film on the cylinder walls and the oil in the ring grooves. During low-temperature engine operation in stop-go driving (i.e., when the vehicle is stopped), NOx and unburned gasoline are absorbed into the engine oil and, in high-temperature engine operation (i.e., when the vehicle is moving), NOx and unburned gasoline are released from the oil.

Although turbocharging can extend the high load limit of low temperature combustion (LTC) strategies such as reactivity controlled compression ignition (RCCI), the low exhaust enthalpy prevalent in these strategies necessitates the use of high exhaust pressures for improving turbocharger efficiency, causing high pumping losses and poor fuel economy. To mitigate these pumping losses, the divided exhaust period (DEP) concept is proposed. In this concept, the exhaust gas is directed to two separate manifolds: the blowdown manifold which is connected to the turbocharger and the scavenging manifold that bypasses the turbocharger. By separately actuating the exhaust valves using variable valve actuation, the exhaust flow is split between two manifolds, thereby reducing the overall engine backpressure and lowering pumping losses. In this paper, results from zero-dimensional and one-dimensional simulations of a multicylinder RCCI light-duty engine equipped with DEP are presented.

Reducing friction in the crankshaft main bearings is an effective means of improving the fuel efficiency of reciprocating internal combustion engines. To realize these improvements, it is necessary to understand the lubricating conditions, in particular the oil film pressure distributions between crankshaft and bearings. In this study, we developed a thin-film pressure sensor and applied it to the measurement of engine main bearing oil film pressure in a 4-cylinder, 2.5 L gasoline engine. This thin-film sensor is applied directly to the bearing surface by sputtering, allowing for measurement of oil film pressure without changing the shape and rigidity of the bearing. Moreover, the sensor material and shape were optimized to minimize influence from strain and temperature on the oil film pressure measurement. Measurements were performed at the No. 2 and 5 main bearings.

In Biodiesel Fuel Research Working Group(WG) of Japan Auto-Oil Program(JATOP), some impacts of high biodiesel blends have been investigated from the viewpoints of fuel properties, stability, emissions, exhaust aftertreatment systems, cold driveability, mixing in engine oils, durability/reliability and so on. This report is designed to determine how high biodiesel blends affect oil quality through testing on 2005 regulations engines with DPFs. When blends of 10-20% rapeseed methyl ester (RME) with diesel fuel are employed with 10W-30 engine oil, the oil change interval is reduced to about a half due to a drop in oil pressure. The oil pressure drop occurs because of the reduced kinematic viscosity of engine oil, which resulting from dilution of poorly evaporated RME with engine oil and its accumulation, however, leading to increased wear of piston top rings and cylinder liners.

Achieving a multi-cylinder engine with excellent noise/vibration character sties and low friction at the main bearings requires an optimal design not only for the crankshaft construction but also for the bearing support system of the cylinder block. To accomplish that, it is necessary to understand crankshaft system behavior and the bearing load distribution for each of the main bearings. Crankshaft system behavior has traditionally been evaluated experimentally because of the difficulty in performing calculations to predict resonance behavior over the entire engine speed range. A coupled crankshaft-block analysis method has been developed to calculate crankshaft system behavior by treating vibration and lubrication in a systematic manner. This method has the feature that the coupled behavior of the crankshaft and the cylinder block is analyzed by means of main bearing lubrication calculations. This paper presents the results obtained with this method.

A direct calibration has been performed on laser-induced fluorescence measurements of the oil film in a single cylinder air-cooled research engine by simultaneously measuring the minimum oil film thickness by the capacitance technique. At the minimum oil film thickness the capacitance technique provides an accurate measure of the ring-wall distance, and this value is used as a reference for the photomultiplier voltage, giving a calibration coefficient. This calibration coefficient directly accounts for the effect of temperature on the fluorescent properties of the constituents of the oil which are photoactive. The inability to accurately know the temperature of the oil has limited the utility of off-engine calibration techniques. Data are presented for the engine under motoring conditions at speeds from 800 - 2400 rpm and under varying throttle positions.

The contribution to the engine-out hydrocarbon (HC) emissions from fuel that escapes the main combustion event in piston ring crevices was estimated for an air-cooled, V-twin utility engine. The engine was run with a homogeneous pre-vaporized mixture system that avoids the presence of liquid films in the cylinder, and their resulting contribution to the HC emissions. A simplified ring pack gas flow model was used to estimate the ring pack contribution to HC emissions; the model was tested against the experimentally measured blowby. At high load conditions the model shows that the ring pack returns to the cylinder a mass of HC that exceeds that observed in the exhaust, and thus, is the dominant contributor to HC emissions. At light loads, however, the model predicts less HC mass returned from the ring pack than is observed in the exhaust. Time-resolved HC measurements were performed and used to assess the effect of combustion quality on HC emissions.

Some automakers have been studying variable compression ratio (VCR) technology as one possible way of improving fuel economy. In previous studies, we have developed a VCR mechanism of a unique multiple-link configuration that achieves a piston stroke characterized by semi-sinusoidal oscillation and lower piston acceleration at top dead center than on conventional mechanisms. By controlling compression ratio with this multiple-link VCR mechanism so that it optimally matches any operating condition, the mechanism has demonstrated that both lower fuel consumption and higher output power are simultaneously possible. However, it has also been observed that fuel consumption does not reduce further once the compression ratio reached a certain level. This study focused on the fact that the piston-stroke characteristic obtained with the multiple-link mechanism is suitable to a longer stroke.

A multiple-link variable compression ratio (VCR) mechanism is suitable for a long-stroke engine by providing the following characteristics: (1) a nearly symmetric piston stroke and (2) an upper link that stays vertical around the time of the maximum combustion pressure. These two characteristics work to reduce force inputs to the piston. The maximum inertial force around top dead center is reduced by the effect of the first characteristic. The second characteristic is effective in reducing piston side thrust force and helps ease piston pin lubrication. Because of the combined effect of these characteristics, the piston skirt can be made smaller and the piston pin can be shortened. That makes it possible for the piston skirt and piston pin to move between the counterweights, resulting in a downward extension of the piston stroke. As a result, a longer-stroke engine mechanism can be achieved without making the cylinder block taller.