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A mixed time-scale subgrid large eddy simulation was used to simulate mixture formation, combustion and soot formation under the influence of turbulence during diesel engine combustion. To account for the effects of engine wall heat transfer on combustion, the KIVA code's standard wall model was replaced to accommodate more realistic boundary conditions. This were carried out by implementing the non-isothermal wall model of Angelberger et al. with modifications and incorporating the log law from Pope's method to account for the wall surface roughness. Soot and NOx emissions predicted with the new model are compared to experimental data acquired under various EGR conditions.

It is effective in engine fuel economy to reduce the viscous friction by applying lubricating oil with low viscosity. The lower viscosity such as SAE0W20, however, increase lubricating oil consumption, LOC. In addition, it has become urgent to reduce the LOC because the emission of the sulfide ash, phosphorous and sulfur contents degrades the diesel particulate filter and the de-NOx catalyst, in addition to which the emission of metal oxide contents from oil additives can cause pre-ignition in highly supercharged spark ignition engines. In order to clarify the LOC mechanism of low viscosity oils, the LOC rates were measured with a supercharged diesel engine under various operating conditions when lubricated with SAE30 or SAE10W30 test oil, and the resulting data have been compared with the rates of the evaporation from the oil-film on the cylinder wall, LOE, as predicted by the devised analysis method for multi-species component oils.

The influence of pressure on spherically propagating premixed turbulent flames was examined with experiments carried out using a constant volume fan-stirred combustion vessel. The effects of mixture strength and turbulence intensity on the propagation and quench of turbulent flames were studied for mixture pressures of 0.10 to 0.50 MPa. Two mechanisms of quench were observed and are discussed for lean and rich flames. Possible correlations of turbulent burning velocity were developed in terms of Lewis and turbulence Reynolds numbers.

Concept of the spray guided direct Injection spark ignition (DISI) was studied to improve the performance of wall-guided DISI. Focusing the effect of multi-hole injector location either centrally-mounted or side-mounted, mixture distribution and ignitability was studied. Computational Fluid Dynamics (CFD) modeling was applied to investigate the history of mixture, ignitable mixture existence around the spark plug in light load condition and homogeneity in full load condition. CFD results showed that side-mounted injection has an advantage over centrally-mounted injection in terms of mixture stability around the spark plug, although the slight disadvantage in homogeneity in full load condition. Side-mounted injection was selected because of robust ignitability potential and further experimental investigation was conducted. Stable combustion window against injection and ignition timing was investigated in experimentally.

The present study introduces a multi-component model for heavy fuel oil combustion based on two component approximation, implemented into KIVA-3V using modified evaporation, ignition and combustion models. The fuel is treated as a blend of residual portion and cutter stocks. Different fuel properties are assigned to each component affecting evaporation behavior in the liquid phase as well as ignition and combustion characteristics in the vapor phase. The model was validated regarding spray and flame appearance using photographs of spray combustion in a visual constant volume combustion chamber. Further the effects of fuel component properties on the ignition and combustion properties of the fuel blend have been investigated based on rate of heat release analysis.

A new nitrogen oxide (NOx) reduction concept is suggested. A strong vertical vortex generated within the combustion bowl can mix hot burned gas into the cold excess air at the center of the combustion-bowl. This makes the burned gas cool rapidly. Therefore, it is possible to reduce NOx, which would be produced if the burned gas remained hot. In this paper the effect was verified with a 3D-CFD analysis of spray, air, combustion gas, and thermal efficiency as well as experiments on a 4-cylinder 2.0-liter direct injection diesel engine. The results confirmed that the vertical vortex was able to be strengthened with the change of spray characteristics and the combustion bowl shapes. This strengthened vertical vortex was able to reduce NOx by approximately 20% without making smoke and thermal-efficiency worse. Above results proved the effectiveness of this method.

Combustion phenomena inside the actual Gasoline-Direct-Injection (GDI) engines have been drawing high attention to its emission characteristics as well as its potential to deal with ultra lean mixture. Although the detailed observation is necessary for its improvement, combustion visualization seems to be strangely overlooked for some reason. This study focuses on the direct observation of GDI combustion to clarify the difficulties behind GDI concept by using a test engine of an actual “wall-guided” configuration and by comparing GDI spray quality with diesel spray in a high-pressure constant volume bomb. The results show that some of the problems about GDI combustion seem to be rather essential than easily conquered, which suggests the necessity for another combustion concept.

Considerable amounts (400 ∼ 600 thousand tons) of waste vegetable oil in Japan are still flushed down the drain every year. Utilization of waste vegetable oil for diesel fuel leads to two advantages for environmental protection, to reduce CO2 emission from engines and to avoid water pollution of rivers. In this study, combustion characteristics of waste vegetable oil methyl ester (WME) are investigated in detail by not only engine test run but also observation of burning flames in a visual engine. As results indicate, WME shows rather better combustion state in the visual engine and lower smoke emission from a high-speed DI test engine than gas oil. Moreover, by emulsifying WME with water, further improvement of combustion and more than 18 % reduction of NOx emission is carried out.

In Japan, about 750 million liters of lubricating oil from automobiles and marine engines become waste per year. The authors propose a plan to convert such used lubricating oil (ULO) to effective energy. In detail, some special diesel generator plants should be built and ULO should be burned there after some process. This plan has at least two advantages, i.e. to save the petroleum energy and to avoid the environmental pollution. Aim of this study is to develop the way to utilize ULO for diesel fuel at such a generator plant. Combustion characteristics of ULO are in detail investigated by observation of burning flames in a visual engine and by engine test run. As results of comparison between ULO and heavy fuel oil (HFO), ULO shows rather better ignition quality in the visual engine and lower smoke emission from the running test engine than HFO.

We have developed injection molding technologies consist of a new high-strength long-glass fiber reinforced polypropylene (PPLGF). They are key technologies of new modular design for substantial reductions of weight and cost, offering integrated functionality. The strength of injection molded parts are three times stronger than that of the conventional material. This technology makes it possible to replace parts from steel stamping and press molded glass-mat reinforced polypropylene. The front end and door modules of Atenza / Mazda6, Demio / Mazda2, RX-8 employs the module carriers using this material, resulting in dramatic weight and cost savings. (Fig. 1)

The newly developed rotary engine has achieved major progress in high performance, improved fuel economy and clean exhaust gas by innovative action. The engine of the next generation is named RENESIS, which stands for “The RE (Rotary Engine)'s GENESIS” or the rotary engine for the new millennium. The peripheral exhaust port of the previous rotary engine is replaced by a side exhaust port system in the RENESIS. This allows for an increase in the intake port area, thus producing higher power. Exhaust opening timing is retarded to improve thermal efficiency. The side exhaust port also allows reducing the internal EGR, stabilizing the combustion at idling. The improved thermal efficiency and the stabilized idle combustion result in higher fuel economy. In addition, the side exhaust port allows a reduction of the HC mass, realizing reduced exhaust gas emission.

Combustion characteristics of the transient methane jet were investigated using a constant volume bomb. The amount of unburned fuel increased as the ignition timing was delayed. Bulk quenching was found to occur in the trailing part of the jet due to the low fuel concentration. Then the characteristics of the flame propagation into the lean region was investigated. This is accomplished by the injection of methane into the lean methane-air mixture charge, whose equivalence ratio was less than the lower flammability limit of the premixed methane-air mixture. The effects of methane concentration of the charge on the flame propagation was examined. The flame generated in the fuel jet propagated into the lean mixture charge. Though the flame propagated in the lean mixture charge for a longer duration with the increase of its methane concentration, it was quenched in the charge before it reached the chamber wall.

We have developed injection molding technologies consist of a new high-strength long-glass fiber reinforced polypropylene (PPLGF). They are key technologies of new modular design for substantial reductions of weight and cost, offering integrated functionality. The strength of injection molded parts are three times stronger than that of the conventional material. This technology makes it possible to replace parts from steel stamping and press molded glass-mat reinforced polypropylene. The front end and door modules of Mazda 6 employ the module carriers using this material, resulting in dramatic weight and cost savings.

Combustion characteristics of the stratified mixture were investingated by the experiments on the combustion of the transient fuel jet and the numerical simulations of counterflow premixed flames. In the experiments, some characteristic features such as “secondary flame” and “bulk quenching” were observed. The secondary flame came out in the burned region after the primary flame had propagated within the fuel jet. The bulk quenching was found to occur in the periphery of the jet due to the low fuel concentration. Then the “flame inertia” was found in the investigation of the flame propagation into the lean region. The experiment was accomplished by the injection of propane into the lean premixed propane-air mixture charge, whose equivalence ratio was less than the lower flammability limit of the premixed mixture. The flame generated in the fuel jet propagated into the lean premixed mixture charge as if it had an “inertia”.

The sequential fuel injection, in which fuel is injected into swirl being generated for mixture stratification, was used to pursue the potential of a lean burn engine for its performance improvement. As a result, it has been found that the most effective method to increase thermal efficiency while reducing NOx emission level is to combine a high-compression compact combustion chamber located on exhaust valve side in cylinder head with DICS (Dual induction Control System). This method was used to build a high-compression lean burn concept vehicle, which was evaluated for compliance to various emission standards. Testing showed that the concept vehicle can improve fuel economy by 10.5% on the Japanese 10-mode cycle, by 8.3% on the ECE mode cycle, and by 6.3% on the U.S. EPA test mode cycle while meeting respective emission standards.

In order to determine the usefulness of coconut and palm oil biodiesels as alternative diesel fuel, the fuel properties, the combustion characteristics and the exhaust emissions were investigated. Therefore, the methyl esters of coconut, palm and rapeseed oils (CME, PME and RME) and the ethyl ester of palm and rapeseed oils (PEE and REE) were processed and tested using a DI diesel engine. From the experimental results, the thermal efficiency of CME is almost the same as the other test fuels and CME has the lowest HC, CO, NOx and smoke emissions among the test fuels. Also PEE has the same ignitibility as PME and the exhaust emissions of PEE are almost the same as PME. From this investigation, we can say that CME and PEE are favorable alternative diesel fuels to substitute for petroleum based diesel fuel.

In the present study, numerical simulation coupling convection and radiation in vehicle was done to analyze the formation of the temperature field under the non-uniform thermal condition. The scaled cabin model of simplified compact car was used and the thermal condition was determined. The fore floor, the top side of the inst. panel, the front window and the ceiling were heat source. The lateral side walls were cooled by the outdoor air and the other surfaces were adiabatic. It is same with the experimental condition presented in Part 5. In order to analyze the individual influence of each heat source, Contribution Ratio of Indoor climate (CRI) index was used. CRI is defined as the ratio of the temperature rise at a point from one individual heat source to the temperature rise under the perfect mixing conditions for the same heat source.

Outwardly propagating stoichiometric flames of H2/CH4/air were studied in a constant volume fan-stirred combustion chamber in order to investigate the effects of hydrogen concentration on the turbulent burning velocities. The experiments were conducted at mixture temperature of 350 K and mixture pressure of 0.10 MPa. The mole fraction of hydrogen in the binary fuel was varied from 0 to 1.0 for turbulence intensities equal to 1.23, 1.64 and 2.46 m/s. Laminar flames of the mixtures were first investigated to obtain the unstretched laminar burning velocities and the associated Markstein numbers. The unstretched laminar burning velocity increased non-linearly with increase in hydrogen fraction. The Markstein number and the effective Lewis number of the mixtures varied non-monotonically with hydrogen mole fraction. The Markstein number was used to investigate the influence of thermo-diffusive effects on the turbulent burning velocity.

The present study investigated the aerodynamic pitching stability of sedan-type vehicles under the influence of A- and C-pillar geometrical configurations. The numerical method used for the investigation is based on the Large Eddy Simulation (LES) method. Whilst, the Arbitrary Lagrangian-Eulerian (ALE) method was employed to realize the prescribed pitching oscillation of vehicles during dynamic pitching and fluid flow coupled simulations. The trailing vortices that shed from the A-pillar and C-pillar edges produced the opposite tendencies on how they affect the aerodynamic pitching stability of vehicles. In particular, the vortex shed from the A-pillar edge tended to enhance the pitching oscillation of vehicle, while the vortex shed from the C-pillar edge tended to suppress it. Hence, the vehicle with rounded A-pillar and angular C-pillar exhibited a higher aerodynamic damping than the vehicle with the opposite A- and C-pillars configurations.

Experiment and CFD have been performed to clarify the distribution of wind noise sources and its generation mechanism for a production vehicle. Three noise source identification techniques were applied to measure the wind noise sources from the outside and inside of vehicle. The relation between these noise sources and the interior noise was investigated by modifying the specification of underbody and front-pillar. In addition, CFD was preformed to predict the noise sources and clarify its generation mechanism. The noise sources obtained by simulation show good agreement with experiment in the region of side window and underbody.