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Relationships between vehicle's high speed stability during a steering action and following aerodynamic coefficients have already been reported in the past: coefficients for time-averaged aerodynamic lift, yawing moment, side force and rolling moment. In terms of the relationships, however, we have occasionally experienced different high speed stability during steering input even with identical suspension property and almost the same aerodynamic coefficients. A vehicle during high speed cornering shows complex behavior due to unsteady air flow around the vehicle and unintentional steering input from a driver. So it is supposed that the behavior is too complex to be fully described only with those aerodynamic coefficients. Through on-road test [1] and CFD analysis [2,3,4], we have studied unsteady aerodynamic characteristics around a vehicle for pitching motion during straight-line high speed driving.

A new impinging nozzle head attached on a normal injection nozzle was designed for improving the performance and combustion of DI diesel engine. Since the fuel is directly injected to the nozzle head at a very short distance from a spray tip of nozzle in a DI diesel engine, the fuel particles will be improved in spray diffusion and distribution. In the case of a prototype injection nozzle with four orifices, the spray angle from each orifice is narrow and similar to the shape of conifer's leaves. By using of the new designed impinging nozzle head, however, an improved spray angle and distribution of fuel and a better starting performance at very low temperature have been observed.

Several different shaped impinging nozzle heads have been studied. A small impinging nozzle head supported by single stay shows a good spray distribution, and economic fuel consumption under middle engine loads and all engine speeds In a single cylinder DI diesel engine without air swirl Intake system.

This report describes with the performance test of a diesel engine using a new variable scroll type turbocharger (VS turbocharger). The experimental variable scroll is relatively a simple structure in which several scroll pieces are jointed by pins, located inside of exhaust turbine inlet flow passage. The scroll is varied by the control rod according to exhaust flow volume, and as a result, the A/R ratio that effects to the performance of turbocharger is varied. To compare the performances of variable scroll type turbocharger with a conventional turbocharger with waste gate, a test of diesel engine equipped with each was performed. The experimental results show that VS turbocharger increases more than the conventional turbocharger in boost pressure at lower engine speed, and the wide torque range is ensured. Also, the experimental scroll pieces did not showed signs of trouble from heat wear during experimentation ensuring reliability.

A new variable scroll type turbocharger has been developed, which is a kind of variable geometry turbocharger. This paper describes a method for determining the shape of a scroll chamber of a turbine housing of the turbocharger. The basic idea is to vary the flow area using the scroll according to exhaust gas flow. The scroll consists of several scroll pieces joined to form a linked variable structure. The shape of the scroll pieces is decided on the basis of an Archimedes’ curve. The device developed is relatively simple.

A comprehensive two-dimensional gas chromatography with time of flight mass spectrometer (GC x GC - TOFMS) was applied to analyze combustion products in exhaust gas emitted by a spark ignition combustion engine. N-heptane and toluene were used as fuel. For identification of detected compounds, NIST library search of the GC Image software was used. In exhaust gas of SI combustion using n-heptane as fuel, many types of branched chain compounds, aromatic compounds and naphthenic compounds were detected. On the other hand, in toluene SI combustion, most components of exhaust gas were aromatic compounds.

The injection amount per stage in a multiple injection strategy is smaller than a conventional single-stage injection. In this paper, the effect of the injection amount (0.27mg, 0.89mg, 2.97mg) under 100MPa injection pressure and the effect of injection pressure (100MPa, 150MPa, 170MPa) under different injection amounts (0.27mg, 2.97mg) on the spray and mixture formation characteristics were studied by analyzing the vapor/liquid phase concentration distributions obtained under various conditions via using the tracer LAS technique. The spray was injected into a high-pressure and high-temperature constant volume vessel by using a single-hole nozzle with a diameter 0.133mm. The higher the injection pressure with a smaller injection amount is, the shorter the spray tip penetration and leaner air-fuel mixture occur. The combustion processes had been examined by a high-speed video camera with the two-color pyrometry method.

Spray characteristics under very small injection amount injected by the hole-type nozzle for a D.I. Diesel engine were investigated using the spray test rig consisting a high-pressure and high-temperature constant volume vessel with optical accesses and a common rail injection system. The Laser Absorption Scattering (LAS) technique was used to visualize the liquid and vapor phase distributions in the evaporating spray. In the very small injection amount condition of the evaporating and free (no wall impingement) spray, the both spray tip penetration and spray angle are larger than those of the non-evaporating free spray. This tendency contradicts the previous observation of the diesel spray with large injection amount and the quasi steady state momentum theory. In the case of the spray impinging on a 2-dimensional piston cavity wall, the spray tip penetration of the evaporating spray is larger than that of the non-evaporating spray.

We investigate the pitching stability characteristics of sedan-type vehicles using large-eddy simulation (LES) technique. Pitching oscillation is a commonly encountered phenomenon when a vehicle is running on a road. Attributed to the change in a vehicle's position during pitching, the flow field around it is altered accordingly. This causes a change in aerodynamic forces and moments exerted on the vehicle. The resulting vehicle's response is complex and assumed to be unsteady, which is too complicated to be interpreted in a conventional wind tunnel or using a numerical method that relies on the steady state solution. Hence, we developed an LES method for solving unsteady aerodynamic forces and moments acting on a vehicle during pitching. The pitching motion of a vehicle during LES was produced by using the arbitrary Lagrangian-Eulerian technique. We compared two simplified vehicle models representing actual sedan-type vehicles with different pitching stability characteristics.

As an effective means of improving engine output, turbocharging has been widely used in engines. However, due to the inherent mismatch of a turbocharger to a reciprocating machine, a turbocharged machine does have some drawbacks,such as the reduction in transient performance, low torque backup, low torque and etc. One solution to these problems is to dynamically vary the size of the turbine stage, reducing the swallowing capacity of the turbine at lower gasflows and increasing the swallowing capacity at high gasflows. A turbocharger fitted with such a turbine is called “Variable Geometry” turbocharger. In general, there are two types of variable nozzle turbocharger. One is the traditional gas turbine approach of using a set of individually pivotable nozzle guide vanes (1) (2), and the other is with axial movable nozzle vanes (3) (4) (5).

In order to measure the droplets and vapor concentration inside a fuel spray, a dual-wavelength laser absorption-scattering technique was developed using the second harmonic (532nm) and the fourth harmonic (266nm) of a Nd:YAG laser and using dimethylnaphthalene as the test fuel. The investigation results show that dimethylnaphthalene, which has physical properties similar to diesel fuel, is almost transparent to visible light near 532nm and is a strong absorber of ultraviolet light near 266nm. Based on this result, the vapor concentration in a fuel spray can be determined by the two separate measurements: a transmission measurement at a non-absorbing wavelength to detect the droplets optical thickness and a transmission measurement at an absorbing wavelength to detect the joint vapor and droplets optical thickness. The droplets density can be determined by extinction imaging through the transmission at the non-absorbing wavelength.

This paper is describes the progress of the development of continuous variable valve timing mechanism by the combination of the three-dimensional cam and the moving rocker arm, and the performance of 4 cylinder gasoline engine with this mechanism. This continuous valve timing mechanism is very concise. Through the trial product's experiment, it proved to be reliable. Furthermore, engine performance demonstrated high torque and low fuel consumption in wide engine speed range.

An axially movable vane turbocharger has been modified based on the basic aerodynamic design principles, and good performance is obtained. The details of design and engine bench testing results of several vane variations are presented, and the most suitable assembly nozzle with two separate vanes is then developed. These have produced a simple design with a minimum number of the moving parts. Experimental data also show that the new turbocharger efficiently expands the effective torque band and get the low fuel consumption at a wide engine speed range.

This paper is described the performance of VVT using engine cycle simulation software and the verification of compression ignition combustion in practical engine. It was predicted by engine cycle simulation that the control of high temperature EGR by the application of VVT improved thermal efficiency markedly by compression ignition combustion. A trial VVT is applied to an actual engine, and compression ignition combustion is realized.

A virtual power window control system was built in order to look into and demonstrate applications of microcontroller models. A virtual ECU simulated microcontroller hardware operations. The microcontroller program, which was written in binary digital codes, was executed step-by-step as the virtual ECU simulation went on. Thus, production-ready codes of ECUs are of primary interest in this research. The mechanical system of the power window, the DC motor to lift the window glass, the H-bridge MOSFET drivers, and the current sensing circuit to detect window locking are also modeled. This means that the hardware system of the control system was precisely modeled in terms of mechanical and circuit components. By integrating these models into continuous and discrete co-simulation, the power window control system was analyzed in detail from the microscopic command execution of the microcontroller to the macroscopic motion of the window mechanism altogether.

In order to improve thermal efficiency of spark ignition (SI) engines, an improved technology to avoid irregular combustion under high load conditions of high compression ratio SI engines is required. In this study, the authors focused on high pressure gasoline direct injection in a high compression ratio SI engine, which its rapid air-fuel mixture formation, turbulence, and flame speed, are enhanced by high-speed fuel spray jet. Effects of fuel injection pressure, injection and spark ignition timing on combustion characteristics were experimentally and numerically investigated. It was found that the heat release rate was drastically increased by raising the fuel injection pressure. The numerical simulation results show that the high pressure gasoline direct injection enhanced small-scale turbulent intensity and fuel evaporation, simultaneously.

The multi-impingement-wall head (MIW head) is designed to be located at the center of combustion chamber and is attached to the cylinder head. In this paper, a new concept of the MIW head has been investigated to obtain a three-dimensional diffusion spray for improving the combustion and performance of a DI diesel engine. Four Types of combustion chambers, the troidal type used in a normal DI diesel engine, and the reentrant types with a projection, with a cutouts, and their combinations (with both projection and cutouts) have been used in the NICS-MH engine experiments. Based on the experimental results of engine performance, it shows that the reentrant type of combustion chamber with a projection and a cutouts has a better fuel consumption and produces lower harmful exhaust gases (HC, NOx and smoke) than those of other NICS-MH engines.

A three-dimensional diffusing spray using the multi-impingement-wall head (MIW head) has been proposed to form air-fuel mixtures in a simple DI diesel engine. In this paper, effects of the width of the MIW head on spray pattern, distribution and engine performance have been investigated. In the fuel spray and engine performance experiments, an optimal width of MIW head results in the collision of fuel particles to advantageous position in a combustion chamber for obtaining a good fuel spray distribution. The minimum BSFC is almost the same value as that of a single DI diesel engine, the HC and smoke densities are reduced and the NOx density is shown a tendency to some increase under part load and decrease under full load. A relatively slow heat release rate and maximum temperature duration of the MIW head can be obtained by shortening the ignition delay.

Fuel injected from multi-hole injector with a small injection angle (100°) is impinged to the multi-impingement-wall head(MIW head), which is located in the center of combustion chamber and is attached to the cylinder head. The fuel is diffused into the piston cavity to form a three-dimensional diffusion spray. The main advantage of diffusion spray is that the effects of the fuel impinging diffusion and the collision between fuel particles can be obtained. Based on the concept of MIW head, the experimental results show that the combustion performance and the fuel consumption have been improved. Besides, the NOx, HC and smoke densities of the exhaust gas of a diesel engine have been reduced.