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This study simulates soot formation processes in diesel combustion using a large eddy simulation (LES) model, based on a one-equation subgrid turbulent kinetic energy model. This approach was implemented in the KIVA4 code, and used to model diesel spray combustion within a constant volume chamber. The combustion model uses a direct integration approach with a fast explicit ordinary differential equation (ODE) solver, and is additionally parallelized using OpenMP. The soot mass production within each computation cell was determined using a phenomenological soot formation model developed by Waseda University. This model was combined with the LES code mentioned above, and included the following important steps: particle inception during which acenaphthylene (A2R5) grows irreversibly to form soot; surface growth with driven by reactions with C2H2; surface oxidation by OH radical and O2 attack; and particle coagulation.

Lean-burn technology is now being reviewed again in view of demands for higher efficiency and cleanness in internal combustion engines. The improvement of combustion using in-cylinder gas flow control is the fundamental technology for establishing lean-burn technology, but the great increase in main combustion velocity due to intensifying of turbulence causes a deterioration in performance such as increase in heat loss and N0x. Thus, it is desirable to improve combustion stability while suppressing the increase in main burn velocity as much as possible (1). It is expected that the fluid characteristics of the in-cylinder tumbling motion that the generated vortices during intake stroke breake down in end-half of compression stroke will satisfy the above requisition. This study is concerned with the effects of enhancing of tumble intensity on combustion in 4-valve S. I. engines.

Exhaust and noise emissions were successfully reduced using a Single Spray Direct Injection Diesel Engine (SSDI) on a two-liter naturally-aspirated four-cylinder engine. The compression ratio, the swirl ratio and the pumping rate were optimized to obtain good fuel economy, high power output and low exhaust emissions. Furthermore, through a modification of the fuel injection equipment, hydrocarbon (HC) emissions were reduced. Upon a test vehicle evaluation of this engine, more than 11% fuel savings relative to Mazda two-liter Indirect Injection Diesel Engines (IDI) were obtained. As for engine noise, structural modifications of the engine were carried out to obtain noise emission levels equivalent to IDI.

Valve train motion was investigated with computer simulation technique. The application of a 5-mass model was found to accurately predict the valve train behavior. It was identified that valve train stiffness and close-side characteristics of valve lift curve have significant effects on bounce occurrence. A valve train with high stiffness tends to develop bounce after jump, while on one with low stiffness, bounce starts in the absence of jump. These findings allowed to develop a new cam form with use of harmonic curves for elevating the revolution limit of the valve train.

An approach of modeling is put forward for automobile product development, and a concept of a functional model is proposed in this paper. Functional models of mechanical, electrical and fluid systems of single degree of freedom are introduced. A wiper system and a power train system are modeled using this approach, and hierarchical functional models of these systems are presented. Simulation result with the hierarchical functional model is compared with test result using an actual power train system of passenger car in order to verify validity and usefulness of the proposed approach.

Stratified charge engines have been getting attention for the drastic improvement in thermal efficiency at low-load region. There have been researchers on the two types of engines-the high pressure direct injection stratified charge type in which fuel is supplied directly at high pressure into its combustion chamber right before ignition timings, and the low pressure direct injection stratified charge type in which fuel is injected directly into its cylinder while the cylinder pressure is comparatively low[ 1- 3]. Rotary engines have higher freedom than reciprocating engines in terms of equipping direct fuel injection devices, since their combustion chambers rotate along the rotor housing. The fuel supply units, therefore, need not be exposed to high temperature combustion gas.

The causes of the cyclic combustion variation in a lean operating SI engine have been identified using multivariate analysis on the pressure-time data. Principal component analysis on the combustion characteristics obtained from the pressure-time data was conducted in order to select an index of an optimal released heat pattern for analyzing the causes of the cyclic combustion variation. Using this index and the released heat quantity, the IMEP variation was subjected to multiple regression analysis to identify the causes of the cyclic combustion variation. Optimizing the fuel injection timing and swirl ratio made it possible to enrich the mixture near the spark plug. With the lean limit thus extended, a SI engine was operated in a lean range, and the resultant pressure-time data were analyzed. It was found that the main cause of the IMEP variation in the lean operating SI engine was the released heat quantity variation.

Aluminum Honeycomb Sandwiches and Extrusions have been applied to a platform for convertibles. The platform, composed of a dashpanel and floor panels (honeycomb sandwiches) and a framework (extrusions), has a much more lightweight and rigid structure than other conventional convertible bodies-in-white. This improves remarkably vibrational behavior and handling characteristics, which deteriorate in a convertible, in the case of a prototype.

In recent years, improving fuel efficiency and collision safety are important issue. We have worked on a new construction method to develop body structure which is light weight and strong/stiff. We adopt multi type Tailor-Welded Blanks (TWB) which is formed after welding several steel sheets for ATENZA (MAZDA 6), NEW DEMIO (MAZDA 2), and RX-8. This is a technology to consistently improve of such product properties and to reduce costs. Laser welding is a common TWB welding method, but for further equipment cost reductions and productivity improvements, we have developed a higher welding speed and robust plasma welding and introduced this to mass production. We introduce this activity and results in this report.

As a demand for vehicles of higher functionality grows, automakers and material suppliers are devoting increasing efforts to develop technologies for greater safety, lighter weight, higher corrosion resistance, and enhanced quietness. The resin-sandwiched vibration damping steel sheet (VDSS), developed as a highly functional material for reducing vehicle vibration and noise, has been used for oil pans1) and compartment partitions2). First applied for a structural dash panel of the new Mazda 929, a Zn-Ni electroplated VDSS which allows direct electric welding has contributed to greater weight reduction as well as improved quietness.

This paper describes a calculating method to predict the quasi-static collapsing behaviors of spot-welded closed-hat section curved beams under axial compression. The overall deformat ions and the local buckling modes of beams were calculated using a geometrical model. Force-displacement relations were predicted by a elastic-plastic structural analysis method using the ‘plastic hinge’ concept. Collapsing tests were made on beams which are differenting section size, rotation angle, and metal sheet thickness. Comparisons between the calculated and experimental results of deformed shapes of beams, the local buckling modes and the force displacement relations are discussed.

Disk brake rotors require reduced unsprung weight and improved cooling ability for improved fade performance. Automotive brake rotors made from aluminum metal matrix composites (MMC) were evaluated by dynamometer and vehicle tests for the required improvement. The friction and wear performance and the thermal response during fade stops were compared with those of commercially produced gray cast iron (GCI) rotors. It was proved that MMC is a very effective material to replace GCI for brake rotor application, as it reduces unsprung weight and decreases maximum operation temperature of the brake system.

An all-ceramic swirl chamber has been developed which meets the 1987 U.S. particulate emission standard for LDV. The all ceramic construction raises combustion temperature to reduce particulate emission to the necessary level. But particulate reduction led to two-fold increase in NOx. This problem was coped with by applying EGR and fuel injection timing control. As a result NOx has been cut to the same level as with a base engine and particulate has been further reduced.

Magnesium has the lowest specific gravity of all metals used for structural members. The application of magnesium for a road wheel leads to improved vehicle handling and drivability because of the reduction of an unsprung weight. The authors have developed new magnesium alloy which shows excellent mechanical properties and attained a magnesium forged road wheel that is 30% lighter than aluminum wheels.

A new and very practical technology has been developed to prevent gasoline permeation in plastic fuel tanks. The main body of the new tank is multi-layered, consist of high density polyethylene (HDPE), adhesive resin, polyamide (PA). The top and bottom parts of the tank are single layer consist of HDPE. This method has many advantages including such features as excellent gasoline permeation prevention, the processing time is the same as that for conventional blow molding methods, the method is safe because no toxic substances are used in the treatment process, the cost-performance ratio is excellent due to the minimum use of expensive auxiliaries (PA, adhesive resin), and the top and bottom single layer flashes can be re-used if they are pulverized.

A method was studied for simultaneous zinc phosphating on aluminum and steel surfaces to obtain high corrosion resistance on aluminum surfaces, which conventional phosphatic processing could not provide with sufficient corrosion resistance. Since aluminum is protected by an oxide film on its surface, it has poor processability with zinc phosphating solutions applied to steel. An appropriate quantity of fluoride was therefore added to improve processing, and the coating film, aluminum composition and surface conditions were optimized to suppress filiform corrosion, which is characterized by string-like blisters of paint film starting from a paint defect. In addition, in view of the actual production environment, the corrosion resistance of the ground area made for readjustment after stamping was studied for the optimization of the processing solution.

The new combustion method in DISC engine has been developed. It has a double structure combustion chamber characterized as ‘Caldera’. The chamber is constructed by a center cavity for the purpose of forming a stable mixture around a spark plug electrode, and by an outer cavity which has a role of a main chamber. This method makes possible a perfect un-throttling operation, and a fuel consumption equal to a diesel engine is achieved. With regard to an out-put of DISC engine, a stoichmetric combustion and a high torque are achieved by controling a fuel injection timing with an electro-magnetic injection system device. With regard to emission regulations, a heavy EGR include residual gas decreases greatly NOx and HC emissions simultaneously, and which suggests a possibility to achieve LEV/ULEV regulations.

It has been required recently that diesel engines for passenger cars meet various requirements, such as low noise, low fuel consumption, low emissions and high power. The key to improve the noise is to reduce a combustion noise known as “Diesel knock noise”. Conventional approaches to reduce the diesel knock are decreasing combustion excitation force due to pilot/pre fuel injection, adding ribs to engine blocks or improving noise transfer characteristics by using insulation covers. However, these approaches have negative effects, such as deterioration in fuel economy and increase in cost/weight. Therefore, modification of engine structures is required to reduce it. We analyzed noise transfer paths from a piston, a connecting rod, a crank shaft to an engine block and vibration behavior during engine operation experimentally, and identified that piston resonance was a noise source.

Owing to the small size of engines and high injection pressures, it is difficult to avoid the fuel spray impingement on the combustion cylinder wall and piston head in Direct Injection Spark Ignition (DISI) engine, which is a possible source of hydrocarbons and soot emission. As a result, the droplets size and distribution are significantly important to evaluate the atomization and predict the impingement behaviors, such as stick, spread or splash. However, the microscopic behaviors of droplets are seldom reported due to the high density of small droplets, especially under high pressure conditions. In order to solve this problem, a “spray slicer” was designed to cut the spray before impingement as a sheet one to observe the droplets clearly. The experiment was performed in a constant volume chamber under non-evaporation condition, and a mini-sac injector with single hole was used.

Cost and weight reduction considerations make it very important to evaluate and reduce aerodynamic noise in the early stage of vehicle develpment. For these reasons, a method to evaluate aerodynamic noise quantitatively is needed. As an initial step, our first paper investigated airflow around the A-pillar of a full-scale vehicle. As a result, vortical flow structure and the influence of the vortical flow on the pressure fluctuations were clarified. As the second step, this paper presents an estimation method for the aerodynamic noise from a vehicle. Based on Lighthill's equation, we propose an evaluation equation to estimate aerodynamic noise. The aerodynamic noise radiated externally from a vehicle is estimated as ∑(Pfi,fi,Sfi)2 Where Pfi is the fluctuating pressure on the surface of the vehicle, fi the frequency and Sfi the correlation area. The method is applied to the aerodynamic noise problem associated with the A-pillar of a vehicle.