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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.

The effects of spray/wall interaction on diesel combustion and soot formation in a two-dimensional piston cavity were studied with a high speed color video camera in a constant volume combustion vessel. The two-dimensional piston cavity was applied to generate the impinging spray flame. In the cavity, the flat surface which plays a role as the cylinder head has a 13.5 degree angle with the injector axis and the impinging point was located 30 mm away from the nozzle tip. Three injection pressures of 100, 150, and 200 MPa and a single hole diesel injector (hole diameter: 0.133mm) were selected. The flame structure and combustion process were examined by using the color luminosity images. Two-color pyrometry was used to measure the line-of sight soot temperature and concentration by using the R and B channels of the color images. The soot mass generated by impinging spray flame is higher than that of the free spray flame.

Internal combustion engines still play a vital role in realizing the low carbon society. For spark ignition engines, further improvement in thermal efficiency can be achieved by increasing both compression and specific heat ratios. In the current work, the authors developed practical technologies to prevent output power loss due to knocking at full load, which is a critical issue for increasing compression ratio. These new technologies allowed to increase the compression ratio significantly and provide an equivalent torque level as a conventional engine. As a result, thermal efficiency has been improved at partial load.

Mazda announced that all customers who purchase Mazda cars are provided with the joy of driving and excellent environmental and safety performance under slogan of "Sustainable Zoom-Zoom" long-term vision for technology development. The purpose of this study is to develop a new approach of Life Cycle Assessment (abbreviated to LCA) to be applied to clean energy vehicles and new car models. The improvement of both environmental performance, e.g., fuel consumption, exhaust emissions, vehicle weight reduction, and LCA that is a useful methodology to assess the environmental load of automobiles for their lifecycles has become more important. LCA by inventory analysis, for RX-8 Hydrogen RE as a rotary engine vehicle used hydrogen as clean energy, was carried out and disclosed the world for the first time. LCA for new Mazda 5 was carried out as the portfolio of all models, previously only the specific model equipped with fuel efficiency device based on ISO14040.

Effects of split injection, with a relatively short time interval between the two sprays, on the spray development process, and the air entrainment into the spray, were investigated by using laser induced fluorescence and particle image velocimetry (LIF-PIV) techniques. The velocities of the spray and the ambient air were measured. The cumulative mass of the ambient air entrained into the spray was calculated by using the entrainment velocity normal to the spray boundary. The vortex structure of the spray, formed around the leading edge of the spray, showed a true rotating flow motion at low ambient pressures of 0.1 MPa, whereas at 0.4 MPa, it was not a true rotating flow, but a phenomenon of the small droplets separating from the leading edge of the spray and falling behind, due to air resistance. The development processes of the 2nd spray were considerably different from that of the 1st spray because the 2nd spray was injected into the flow fields formed by the 1st spray.

Recently, an audible clattering noise has been noticed in some vehicles during cold engine starts, mainly in the U.S. The clattering is referred to by various names, such as “carbon knock,” “carbon rap,” “mechanical knock” and “combustion chamber deposit interference (CCDI).” CCDI is believed to be caused by the deposit formation in the combustion chamber. In the research effort described here, CCDI was successfully reproduced in a 2.5-liter multipoint injection engine with a polyolefin amine gasoline additive. It was determined that the CCDI was caused by mechanical contact between the piston top and the cylinder head deposits. The vibration due to CCDI originated mainly at the thrust side of the piston right after top-dead-center on compression stroke and was characterized by a high frequency response. Combustion chamber deposit (CCD) formation depends on many factors, including gasoline additives.

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.

We have introduced a supercharged Miller Cycle gasoline engine into the market in 1993 as an answer to the requirement of reduction in CO2 emission of vehicles. Improvement in the fuel economy of a supercharged Miller Cycle engine is achieved by the reduction of friction loss due to a smaller displacement. The biggest problem of a conventional supercharged engine is knocking. In order to avoid the knocking, lower compression ratio, which accompanies lower expansion ratio, has been adopted by the conventonal engines and achieved insufficient fuel economy improvement. The Miller Cycle obtains superior anti-knocking performance as well as lowering compression ratio, while keeping the high expansion ratio. The decreased friction loss by the smaller displacement has completely lead to the improvement of fuel economy.

A gasoline engine with an entirely new combustion cycle deriving from Miller Cycle is developed. By delaying closing timing of intake valve and with new Lysholm Compressor which provides higher boost pressure, engine knocking is avoided while high compression ratio is maintained and approximately 1.5 times larger toque than that of a naturally aspirated(NA) engine of the same displacement is realized. This V6 Miller Cycle gasoline engine can be the alternative to a larger displacement NA engine because of its equivalent torque performance and its lower fuel consumption by the effect of smaller displacement.

First, this paper describes a measurement of the human back-backrest interface contours and a reduction procedure of the measured contours to reconstruct the statistical back contours of American 50 and 95-percentile male. Second, the paper illustrates the difference of the back contour between the statistical male drivers and SAE 3-D Manikin. Finally, the advantage of using the back contour model in experiment is given. The AM 50 back contour model was used as a loader to obtain the backrest pressure distribution and proved an excellent tool for backrest comfort evaluation.

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.

A hydrogen-fueled rotary engine was investigated with respect to the effects of the fuel supply method, spark plug rating and spark plug cavity volume on abnormal combustion. It was found that abnormal combustion was caused by pre-ignition from the spark plugs and gas leakage through the plug hole cavity. The hydrogen-fueled rotary engine could function through a wide operating range at a theoretical air-to-fuel ratio by optimising the above factors. Consequently, the hydrogen-fueled rotary engine achieved output power of up to 63%-75% of the gasoline specification, while the hydrogen-fueled reciprocating engine only reached 50%.

In this paper, a prediction method of the aerodynamic sound emitted from the three-dimensional delta wing of the attack angle at 15 degrees is presented. Computed flow Reynolds numbers range from 2.39x1 05 up to 9.56X 105. The method is based on the assumptions: flow Mach number is much less than unity and the strength of sound source equals Curle's dipole. These assumptions are validated by the experimental works performed in a quiet-flow-noise wind tunnel. Owing to the low Mach number condition, the computation region can be devided into two regions: inner flow region and outer wave region. The incompressible flow computation in the inner region is performed based on the full Navier-Stokes equations. The integration of the N-S equations are executed by using finite-difference method. For high Reynolds flow computation, the nonlinear convection terms are discretized by third-order upwind difference scheme.

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.

The substantial part of the drag of an automobile is the pressure drag. Therefore, the car must be designed as it produces minimum pressure drag. The present paper describes effects of geometrical configuration of the rear part of a car on the aerodynamic drag. Experiments were made on 1/5 scale models of fastback and notchback design. For the fastback car the drag depends heavily on the angle of a rear window. At a certain critical angle the drag shows a sharp peak. This peak drag can be reduced drastically by the tapering of plan form of the rear geometry. For the notch-back design some combination of the angle of rear window and height of trunk deck shows similar maximum in the drag. Methods of avoiding the large drag were also found. Our experiment was extended to the measurement of structure of wake by hot wire anemometers and total pressure tubes. The correlation between the wake structure and drag was clarified by the consideration of vorticity and circulation.