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Technical Paper

Improvement of Fuel Economy in a Four Stroke Spark Ignition Engine for a Small Motorcycle

For the purpose of reducing the fuel consumption of a motorcycle with a small-displacement, four-stroke spark-ignition engine, a compact combustion chamber was tried and the weight of the moving parts of the engine was reduced. As a result, the gas mileage under 30 km/h cruising condition was increased to 110 km/l with an improvement of 50% over a conventional motorcycle.
Technical Paper

A Study of High Power Output Diesel Engine with Low Peak Cylinder Pressure

This study examined a high-speed, high-powered diesel engine featuring a pent-roof combustion chamber and straight ports, with the objective of improving the specific power of the engine while minimizing any increase in the maximum cylinder pressure (Pmax). The market and contemporary society expect improvements in the driving performance of diesel-powered automobiles, and increased specific power so that engine displacement can be reduced, which will lessen CO2 emissions. When specific power is increased through conventional methods accompanied with a considerable increase in Pmax, the engine weight is increased and friction worsens. Therefore, the authors examined new technologies that would allow to minimize any increase in Pmax by raising the rated speed from the 4000 rpm of the baseline engine to 5000 rpm, while maintaining the BMEP of the baseline engine.
Technical Paper

Quantitative Analysis of Leakage Suppression of DLC Coating on Piston Ring

Piston ring wear in gasoline engine induces deterioration of emissions performance due to leakage of blow-by gas, instability of idling caused by reduced compression in combustion chamber, and to generate early degeneration of engine oil. We examined anti-wear performance of DLC coating on piston ring, which had been recently reported as an effective method for improving the abrasion resistance. As a result, wear rate remained low under the condition of DLC existence on sliding surface, but once DLC was worn out completely, wear of the piston ring was accelerated and its life became shorter than piston ring without DLC. In this research, we designed reciprocating test apparatus that operates at much higher velocity range, and characterized the frictional materials of the piston ring and sleeve and the DLC as a protective film, a vapor phase epitaxy (VPE) was actively used as a means to form certain level of convex and concave shape on its surface.
Technical Paper

Application of Image Converter Camera to Measure Flame Propagation in S.I. Engine

A combustion flame visualization system, for use as an engine diagnostics tool, was developed in order to evaluate combustion chamber shapes in the development stage of mass-produced spark ignition (S.I.) engines. The system consists of an image converter camera and a computer-aided image processing system. The system is capable of high speed photography (10,000 fps) at low intensity light (1,000 cd/m2), and of real-time display of the raw images of combustion flames. By using this system, flame structure estimated from the brightness level on a photograph and direction of flame propagation in a mass-produced 4-valve engine were measured. It was observed that the difference in the structure and the propagation of the flame in the cases of 4-valve and quasi-2-valve combustion chambers, which had the same in the pressure diagram, were detected. The quasi-2-valve configuration was adopted in order to improve swirl intensity.
Technical Paper

Development of Gasoline Combustion Reaction Model

Gasoline includes various kinds of chemical species. Thus, the reaction model of gasoline components that includes the low-temperature oxidation and ignition reaction is necessary to investigate the method to control the combustion process of the gasoline engine. In this study, a gasoline combustion reaction model including n-paraffin, iso-paraffin, olefin, naphthene, alcohol, ether, and aromatic compound was developed. KUCRS (Knowledge-basing Utilities for Complex Reaction Systems) [1] was modified to produce paraffin, olefin, naphthene, alcohol automatically. Also, the toluene reactions of gasoline surrogate model developed by Sakai et al. [2] including toluene, PRF (Primary Reference Fuel), ethanol, and ETBE (Ethyl-tert-butyl-ether) were modified. The universal rule of the reaction mechanisms and rate constants were clarified by using quantum chemical calculation.
Technical Paper

Inhibition Effect of Ethanol on Homogeneous Charge Compression Ignition of Heptane

It is important in the application of bio-ethanol in homogeneous-charge compression ignition (HCCI) engines to investigate the HCCI combustion characteristics of ethanol. As the inhibitory mechanism of ethanol on HCCI combustion is a key factor, simulated chemical reactions are necessary. In this study, chemical reaction simulations in the combustion chamber of a rapid compression machine (RCM) were performed in order to investigate the inhibitory mechanism of ethanol on the HCCI combustion of heptane. The sensitivity analysis results suggested that the OH radical consumption reaction by ethanol that occurs would inhibit the cool flame reaction of heptane. Furthermore, visualization of HCCI combustion with the RCM was conducted using a quartz glass combustion chamber head and ICCD camera. As a result, the cool flame luminescence intensity of heptane was reduced by the addition of ethanol.
Technical Paper

A Study of Vehicle Equipped with Non-Throttling S.I. Engine with Early Intake Valve Closing Mechanism

To enable non-throttling operation of gasoline S.I. engine, we have manufactured engines equipped with a newly developed Hydraulic Variable-valve Train (HVT), which can vary its intake-valve closing-timing freely. The air-intake control ability of HVT engine is equivalent to conventional throttling engines. Combustion becomes unstable, however, under non-throttling operation at idling. For the countermeasure, newly designed combustion chamber has been developed. The reduction of pumping loss by the HVT depends on engine speed rather than load, and amounts to about 80 % maximum. A conventional engine-management system is not applicable for non-throttling operation. Therefore, new management system has been developed for load control.
Technical Paper

A Study on Shockless Combustion Change Control of Direct Injection Gasoline Engine

A direct injection gasoline engine featuring a center-injection method that incorporates a high-pressure injector at the top center of the combustion chamber, has been developed. The engine is characterized by a significantly improved fuel economy and emissions performance as the result of the application of direct-injection stratified charge, DISC, which is one of the main features of the direct-injection engine. This paper describes a study on a change control method for switching between DISC and homogeneous charge combustion. The two forms of combustion employed in the new direct-injection engine differ in terms of combustion limits in relation to recirculated exhaust gas and air-fuel ratio. This causes the torque difference which is a specific issue in direct injection gasoline engines. The authors attempted to cope with the issue from the viewpoints of misfire prevention and fuel amount restriction in accordance with the torque required.
Technical Paper

In-Situ Fuel Concentration Measurement Near Spark Plug by 3.392 μm Infrared Absorption Method-Application to a Port Injected Lean-Burn Engine

In this study, a spark plug sensor for in-situ fuel concentration measurement was applied to a port injected lean-burn engine. Laser infrared absorption method was employed and a 3.392 μm He-Ne laser that coincides with the absorption line of hydrocarbons was used as a light source. In this engine, the secondary valve lift height of intake system was controlled to obtain appropriate swirl and tumble flow in order to achieve lean-burn with the characteristics of intake flow. For such in-cylinder stratified mixture distribution, the fuel concentration near the spark plug is very important factor that affects the combustion characteristics. Therefore, the mixture formation process near the spark plug was investigated with changing fuel injection timing. Under the intake stroke, the timing that fuel passed through near the spark plug depended largely on the fuel injection timing.
Technical Paper

Influence of a Fast Injection Rate Common Rail Injector for the Spray and Combustion Characteristics of Diesel Engine

For reduction of NOx and soot emission with conventional diesel diffusion combustion, the authors focused on enhancement of the rate of injection (hereafter referred to as RoI) to improve air availability, thus enhancing the fuel distribution and atomization. In order to increase opening ramp of the RoI (hereafter referred to as fast injection rate), a hydraulic circuit was improved and nozzle geometries were optimized to make the greatest use of the advantages of the hydraulic circuit. Two different common rail injectors were prepared for this research. One is a mass production-type injector with piezo actuator that achieved the EURO-V exhaust gas emission standards, and the other is a prototype injector equipped with the new hydraulic circuit. The nozzle needle of the prototype injector is directly actuated by high-pressure fuel from common rail to improve the RoI.
Technical Paper

Validation of Turbulent Combustion and Knocking Simulation in Spark-Ignition Engines Using Reduced Chemical Kinetics

Downsizing or higher compression ratio of SI engines is an appropriate way to achieve considerable improvements of part load fuel efficiency. As the compression ratio directly impacts the engine cycle thermal efficiency, it is important to increase the compression ratio in order to reduce the specific fuel consumption. However, when operating a highly boosted / downsized SI engine at full load, the actual combustion process deviates strongly from the ideal Otto cycle due to the increased effective loads requiring ignition timing delay to suppress abnormal combustion phenomena such as engine knocking. This means that for an optimal design of an SI engine between balances must be found between part load and full load operation. If the knocking characteristic can be accurately predicted beforehand when designing the combustion chamber, a reduction of design time and /or an increase in development efficiency would be possible.
Technical Paper

Development of New 3.5 L V6 Turbocharged Gasoline Direct Injection Engine

This paper introduces the newly developed super sports car engine mounted in the new model NSX. A super sports car engine was newly developed to satisfy the high power performance required by the body package. Higher power and compactness were simultaneously achieved by selecting an engine displacement of 3.5 L and by using a V6 layout and a turbocharger. This enabled to mount a power train that combines a hybrid motor with a newly developed transmission in the rear of the body. The lubrication system uses a dry sump system capable of maintaining reliable lubrication in all possible super sports car driving scenarios. The combustion system uses high tumble-flow ports, a direct injection and a port injection system that increase power performance and thermal efficiency, emission reduction. To support the increased heat load due to higher power, a 3-piece water jacket is used around the combustion chamber and the exhaust ports.
Technical Paper

Numerical Simulations of Mixture Formation in Combustion Chambers of Lean-Burn Natural Gas Engines Incorporating a Sub-Chamber

The aim of this study is to clarify the mixture formation in the combustion chamber of our developed natural gas engine incorporating the sub-chamber injection system, in which natural gas is directly injected into a combustion sub-chamber in order to completely separate rich mixture in the sub-chamber, suitable for ignition, from ultra-lean mixture in the main chamber. Mixture distributions in chambers with and without sub-chamber were numerically simulated at a variety of operating conditions. The commercial software of Fluent 16.0 was used to conduct simulations based on Reynolds averaged Navier-Stokes equations in an axial 2 dimensional numerical domain considering movements of piston. Non-reactive flow in the combustion chamber was simulated before the ignition timing at an engine speed of 2000 rpm. The turbulence model employed here is standard k-ε model. Air-fuel ratio is set with a lean condition of 30.
Technical Paper

New 1.0L I3 Turbocharged Gasoline Direct Injection Engine

To comply with the environmental demands for CO2 reduction without compromising driving performance, a new 1.0 liter I3 turbocharged gasoline direct injection engine has been developed. This engine is the smallest product in the new Honda VTEC TURBO engine series (1), and it is intended to be used in small to medium-sized passenger car category vehicles, enhancing both fuel economy through downsizing, state-of-the-art friction reduction technologies such as electrically controlled variable displacement oil pump and timing belt in oil system, and also driving performance through turbocharging with an electrically controlled waste gate. This developed engine has many features in common with other VTEC TURBO engines such as the 1.5 liter I4 turbocharged engine (2) (3), which has been introduced already into the market.
Journal Article

A Study of Controlled Auto-Ignition in Small Natural Gas Engines

Research has been conducted on Controlled Auto-Ignition (CAI) engine with natural gas. CAI engine has the potential to be highly efficient and to produce low emissions. CAI engine is potentially applicable to automobile engine. However due to narrow operating range, CAI engine for automobile engine which require various speed and load in real world operation is still remaining at research level. In comparison some natural gas engines for electricity generation only require continuous operation at constant load. There is possibility of efficiency enhancement by CAI combustion which is running same speed at constant load. Since natural gas is primary consisting of methane (CH4), high auto-ignition temperature is required to occur stable auto-ignition. Usually additional intake heat required to keep stable auto-ignition. To keep high compression temperature, single cylinder natural gas engine with high compression ratio (CR=26) was constructed.
Journal Article

Investigation of Combustion Diagnosis System Applied for the Development of General Purpose Utility Engines

The chief goal of engineers studying internal combustion engines is to improve energy efficiency in the face of the increasingly severe global warming and energy issues. Hence, there have been numerous studies focusing on the combustion reactions in order to develop clean and reliable combustion that is capable of operating using less fuel. And to improve the comprehension of engine performance and its combustion reactions, development of comprehensive measurement technique for engine performance, in-cylinder visualization technique, and numerical simulations, is essential and strongly demanded. There have hitherto been numerous studies about combustion diagnostics and analysis, including high-efficiency measurement techniques using response surface method the air-fuel mixture distribution and flame propagation measurement with optical visualization techniques, and numerical calculations of combustion reaction with elementary reactions.
Journal Article

In-cylinder Optical Investigation of Combustion Behavior on a Fast Injection Rate Diesel Common Rail Injector

The field of diesel combustion research is producing numerous reports on studies of premixed combustion, which promises simultaneous reduction of both NOx and soot, in order to meet increasingly stringent regulations on harmful emissions from automobiles. However, although premixed combustion can simultaneously reduce both NOx and soot, certain issues have been pointed out, including the fact that it emits greater quantities of unburned HC and CO gases and the fact that it limits the operating range. Furthermore, this combustion method sets the ignition delay longer with the aim of promoting the mixing of fuel and air. This raises issues with the product due to the combustion instability and sensitivity to the uneven fuel properties that are found on the market, the capability of the engine response under transient conditions, the deterioration in combustion noise, and so on.
Technical Paper

Engine Knock Toughness Improvement Through Water Jacket Optimization

Improvement of engine cycle thermal efficiency is an effective way to increase engine torque and to reduce fuel consumption simultaneously. However, the extent of the improvement is limited by engine knock, which is more evident at low engine speeds when combustion flame propagation is relatively slow. To prevent engine damage due to knock, the spark ignition timing of a gasoline engine is usually controlled by a knock sensor. Therefore, an engine's ignition timing cannot be set freely to achieve best engine performance and fuel economy. Whether ignition timings for a multi-cylinder engine are the same or can be set differently for each cylinder, it is not desirable for each cylinder has big deviation from the median with respect to knock tendency. It is apparent that effective measures to improve engine knock toughness should address both uniformity of all cylinders of a multi-cylinder engine and improvement of median knock toughness.
Technical Paper

Control of Pressure-Rise Rates of Compression Ignition by Stratification of Reformed Premixture Using Pulsed DBD Irradiation

Dielectric barrier discharge (DBD) was applied to control the pressure-rise rate of homogeneous compression ignition, which is an important obstacle for homogeneous charge combustion engines. DBD can produce nonthermal plasmas and has been generated in air/fuel mixtures to reform some of the fuel molecules found in such mixtures. This generally shortens the ignition delay of compression ignition of the air/fuel premixture. Stratification of the reformed premixture in the combustion chamber was achieved by pulsed DBD irradiation during the induction process. The formation of inhomogeneous distribution of the reformed premixture is expected by the formation of discharge at the end of the intake processes. A demonstrative experiment was conducted by using a rapid compression and expansion machine. A simple plasma reactor was developed and installed at the intake tube. High-voltage, high-frequency pulses were applied to form plasmas. n-Heptane was used as fuel.