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The rotary engine provides high power density compared to piston engine, but one of its downside is higher oil consumption. In order to better understand oil transport, a laser induced fluorescence technique is used to visualize oil motion on the side of the rotor during engine operation. Oil transport from both metered oil and internal oil is observed. Starting from inside, oil accumulates in the rotor land during inward motion of the rotor created by its eccentric motion. Oil seals are then scraping the oil outward due to seal-housing clearance asymmetry between inward and outward motion. Cut-off seal does not provide an additional barrier to internal oil consumption. Internal oil then mixes with metered oil brought to the side of the rotor by gas leakage. Oil is finally pushed outward by centrifugal force, passes the side seals, and is thrown off in the combustion chamber.

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.

Further improvement in fuel consumption is needed for diesel engines to address regulatory requirement particularly for heavy duty diesel in Japan enforced in 2015, in addition to the compliance to the regulatory requirements for exhaust emission, which seems to be more stringent in future. The authors have participated in the project of “Comprehensive Technological Development of Innovative, Next-Generation, Low-Pollution Vehicles” organized by New Energy and Industrial Technology Development Organization (NEDO), and innovative devices such as multi stage boosting system, ultra high-pressure fuel injection system and variable valve actuation (camless) system had been developed in this project from a standpoint of simultaneous improvement of fuel consumption and exhaust emission. In camless system, intake and exhaust valves are driven by hydraulic pressure. So, fully flexible setting of opening and closure timings and lift of the intake and exhaust valves is possible.

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.

Since the fuel supply specifications in a multi-point injection (MPI) system are usually determined experimentaly, the way fuel behaves in the induction port is still not clearly understood. In this study, a fuel behavior model is developed to gain a better understanding of how fuel behaves in the induction port so that the best fuel supply specifications can be determined on the basis of analysis. This paper outlines a model of fuel spray and wall film and presents some typical calculation results. Taking into account fuel properties, the vapor, the flow and other characteristics of fuel in the induction port are calculated using these models. A comparison of the calculated results with experimental data confirms the validity of the model. The calculated results show the effects of the fuel propeties and fuel supply system specifications on induction port fuel behavior.

Inorganic engine lubricant additives, which have various specific, necessary functions such as anti-wear, leave the combustion chamber bound to soot particles (approximately ≤1% by mass) as ash [13], and accumulate in aftertreatment components. The diesel particulate filter (DPF) is especially susceptible to ash-related issues due to its wall-flow architecture which physically traps most of the soot and ash emissions. Accumulated lubricant-derived ash results in numerous problems including increased filter pressure drop and decreased catalytic functionality. While much progress has been made to understand the macroscopic details and effects of ash accumulation on DPF performance, this study explores the nano- and micron-scale forces which impact particle adhesion and mobility within the particulate filter.

Particulate emissions from a production gasoline direct injection spark ignition engine were studied under a typical cold-fast-idle condition (1200 rpm, 2 bar NIMEP). The particle number (PN) density in the 22 to 365 nm range was measured as a function of the injection timing with single pulse injection and with split injection. Very low PN emissions were observed when injection took place in the mid intake stroke because of the fast fuel evaporation and mixing processes which were facilitated by the high turbulent kinetic energy created by the intake charge motion. Under these conditions, substantial liquid fuel film formation on the combustion chamber surfaces was avoided. PN emissions increased when injection took place in the compression stroke, and increased substantially when the fuel spray hit the piston.

A dynamometer-mounted four-cylinder Saturn engine was used to accumulate combustion chamber deposits (CCD), using an additized fuel. During each deposit accumulation test, the HC emissions were continuously measured. The deposit thickness at the center of the piston was measured at the beginning of each day. After the 50 and 35-hour tests, HC emissions were measured with isooctane, benzene, toluene, and xylene, with the deposited engine, and again after the deposits had been cleaned from the engine. The HC emissions showed a rapid rise in the first 10 to 15 hours and stabilization after about 25 hours of deposit accumulation. The HC increase due to CCD accumulation accounted for 10 to 20% of the total engine-out HC emissions from the deposit build-up fuel and 10 to 30% from benzene, isooctane, toluene, and xylene, making CCDs a significant HC emissions source from this engine. The HC emissions stabilized long before the deposit thickness.

A gasoline engine with an electronically controlled fuel injection system has substantially better fuel economy and lower emissions than a carburetted engine. In general, the stability of engine operation is improved with fuel injector, but the stability of engine operation at idle is not improved compared with a carburetted gasoline engine. In addition, the increase in time that an engine is at idle due to traffic congestion has an effect on the engine stability and vehicle reliability. Therefore, in this research, we will study the influence of fuel injection timing, spark timing, dwell angle, and air-fuel ratio on engine stability at idle.

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.

The purpose of this study is to clarify the state of heat loss to the cylinder liner of the tested engine of which piston and cylinder head were previously measured. The authors' group developed an original measurement technique of instantaneous surface temperature at the cylinder liner wall using thin-film thermocouples. The temperature was measured at 36 points in total. The instantaneous heat flux was calculated by heat transfer analysis using measurement results of the temperature at the wall. As a result, the heat loss ratio to all combustion chamber walls is evaluated except the intake and exhaust valves.

The characteristics of the early development of fuel sprays from pressure swirl atomizer injectors of the type used in direct injection gasoline engines is investigated. Planar laser-induced fluorescence (PLIF) was used to visualize the fuel distribution inside a firing optical engine. The early spray development of three different injectors at three different fuel pressures (3, 5, and 7 MPa) was followed as a function of time in 30 μsec intervals. Four phases could be identified: 1) A delay phase between the rising edge of the injection pulse and the first occurrence of fuel in the combustion chamber, 2) A solid jet or pre-spray phase, in which a poorly atomized stream of liquid fuel during the first 150 μsec of the injection. 3) A wide hollow cone phase, separation of the liquid jet into a hollow cone spray once sufficient tangential velocity has been established and 4) A fully developed spray, in which the spray cone angle is narrowed due to a low pressure zone at the center.

Diesel emissions are significant issue worldwide, and emissions requirements have become so tough that. the application of after-treatment systems is now indispensable in many countries To meet even more stringent future emissions requirements, it has become apparent that the improvement of market fuel quality is essential as well as the development in engine and exhaust after-treatment technology. Japan Clean Air Program II (JCAP II) is being conducted to assess the direction of future technologies through the evaluation of current automobile and fuel technologies and consequently to realize near zero emissions and carbon dioxide (CO2) emission reduction. In this program, effects of fuel properties on the performance of diesel engines and a vehicle equipped with two types of diesel NOx emission after-treatment devices, a Urea-SCR system and a NOx storage reduction (NSR) catalyst system, were examined.

Various premixed diesel combustion concepts are suggested as the way of simultaneous reduction of NOx and PM emission from diesel engines. However, every combustion concept has common problems, such as difficulty of ignition timing control, a great deal of HC and CO emissions and limiting the operation region to low load operation. The purpose of this study is to expand the operation region of Premixed Compression Ignition (PCI) combustion, which is a premixed diesel combustion concept that realizes the fuel injection around the top dead center. As a result of examining it with EGR, supercharging operation and low compression ratio piston, PCI combustion region was expanded to cover higher load operation. And the high load region was limited by not only stoichiometric air fuel ratio but also permissible maximum in-cylinder pressure.

A direct-injection gasoline engine that uses a stratified charge combustion process was developed by Nissan and released in the Japanese market toward the end of 1997. This new engine is based on Nissan's VQ engine, which enjoys a good reputation for its quick throttle response and low fuel consumption, and has been developed to accomplish the objectives of reducing fuel consumption by stratified charge combustion and securing high power output. The fuel injectors are connected by an arrangement of lightweight, small-diameter fuel lines that distribute fuel to each injector under high pressure. This system was adopted in order to reconcile the use of an aerodynamic straight intake port with the desired fuel injection position. The use of a casting net injector, which uniformly distributes the fuel spray above the piston, makes it possible to accomplish stratified charge combustion with a shallow-bowl piston.

The SR engine is a new medium-size, all aluminum (cylinder block, head, rocker cover and oil pan) in-line 4-cylinder gasoline powerplant developed as a replacement for CA engine in Nissan's compact passenger cars. The development aim set for this engine was to achieve excellent power output and ample torque in the middle-and high-speed ranges, as well as a clear, linear engine sound up to the red zone. These performance targets have been achieved through the use of the 4-valve-per-cylinder DOHC design featuring a Y-shaped valve rocker arm system. This system allows a straight intake port for high power output and a narrow valve angle for a compact combustion chamber. The result is ample torque output as well as good fuel economy.

Three-dimensional combustion simulation tools together with the Universal Coherent Flamelet Model (UCFM), a flame propagation model, have been applied to SI lean-burn combustion to study the influence of the equivalence ratio on the amount of unburned hydrocarbons (HCs). Unburned HCs from piston-cylinder crevices were taken into the consideration by using a calculation grid incorporating the actual crevice volume and shape and by applying an autoignition model to post-flame phenomena. The calculation results show the general tendencies for the total amount of unburned HCs and their distribution in the combustion chamber.

Fuel injection rate pattern represents an important factor for emissions reduction. In this study, fuel spray photography, combustion photography and experimental data analysis indicate. 1) effect of pilot injection 2) effect of a gradual shaped injection profile using nozzle needle lift control 3) effect of a boot shaped injection profile using pressure control Common rail type fuel injection equipment was used in these experiments, and the engine was single cylinder naturally aspirated D.I. diesel engine. As a result, we found out that it is important to control the pre-mixed combustion for NOx reduction and to activate the diffusion combustion for smoke, and various fuel injection rate patterns we studied have similar effect on combustion and emissions at the most suitable condition respectively.

The presence of liquid fuel inside the engine cylinder is believed to be a strong contributor to the high levels of hydrocarbon emissions from spark ignition (SI) engines during the warm-up period. Quantifying and determining the fate of the liquid fuel that enters the cylinder is the first step in understanding the process of emissions formation. This work uses planar laser induced fluorescence (PLIF) to visualize the liquid fuel present in the cylinder. The fluorescing compounds in indolene, and mixtures of iso-octane with dopants of different boiling points (acetone and 3-pentanone) were used to trace the behavior of different volatility components. Images were taken of three different planes through the engine intersecting the intake valve region. A closed valve fuel injection strategy was used, as this is the strategy most commonly used in practice. Background subtraction and masking were both performed to reduce the effect of any spurious fluorescence.