Search Results

The objective of this study is to explore the relation among mixture distribution condition, chemical character of fuel, combustion processes, and emissions characteristics with premixed charge compression ignition (PCCI) operation. The present experiment employs two fuel injectors which are capable of port injection and direct one. The former was used to supply a highly-homogeneous mixture and the latter with late injection timing was employed to control the mixture heterogeneity. Thus, these sets of injection equipments are capable of setting a wide variety of mixture heterogeneity. Furthermore, two primary reference fuels were used in order to know the influences of chemical character. The experiments were conducted in order to clarify the combustion and emissions characteristics through engine tests. Optical diagnostic was also performed to gain additional insight into the combustion processes for a wide variety of mixture distribution.

Deceleration patterns of an expert driver will be formulated using the perceptual risk index for approach and proximity of a preceding vehicle as an example of comfortable braking pattern. It will be shown that the formulated braking pattern can generate smooth deceleration profile uniformly for many conditions of approaching conditions. In addition, brake initiation timing of expert driver will be successfully formulated using the alternative index. Finally, an automatic braking system will be proposed based on the formulated brake initiation model and the velocity profile. Twenty five expert drivers experienced the automatic braking installed in an experimental car. It will be shown that the proposed system can generate smooth profile and realize secure brake patterns based on subjective evaluation.

It is very much necessary for researchers and engineers whose work is the field of combustion in a CI engine to find the information of droplets in a diesel spray. The information is strongly required to construct the model of spray built in the numerical code for its simulation and to be used for the verification of the accuracy of the calculation. This paper describes the photographing system with high spatial resolution, the distribution of droplet size and the vortex scale caused by the droplets motion by means of this system.

This paper describes the application of statistical energy analysis (SEA) to predicting sound power radiated from co-generation system enclosure. To predict vibration and noise accurately by using SEA, it is important to estimate parameter called loss factors. In this study, loss factors were estimated by power injection method. Next, the noise radiated from enclosure surface was predicted by the obtained vibration and radiation efficiency of enclosure panels. As a result, the calculated sound power was relatively corresponding to measured sound power. Finally, the sound power from modified enclosure was predicted. Coupling loss factors related to a modified subsystem were estimated by ratio of the number of structure modes. By using these steps, the noise from the system was reduced.

It’ll be expected that tandem riders increase in the future. So, there is a need to improve the motorcycle stability of tandem riding from the perspectives of safety and comfort. In this research, we focus on tandem riding at low speed because the motorcycle especially becomes unstable. In order to improve the stability of a motorcycle after disturbance is input by the passenger’s posture change, we design a front wheel steer control system that assists the rider’s driving operation. And we simulate it. It is necessary to consider cooperation with the rider’s driving operation. In this study, as a means to consider the cooperative control of the man-machine system, the fuzzy logic was applied to this system.

A high performance digging algorithm for a hydraulic excavator has not been established because the relationship between digging parameters and digging performance is complex. An examination process for a high-performance digging algorithm is proposed. In this paper, the digging efficiency is defined as the soil volume derived by the applied energy to drive the bucket in order to evaluate digging performance. The digging algorithm, which we study for high digging efficiency, decreases the reaction force to the bucket from the soil by moving the bucket upward when the reaction force exceeds a threshold during digging. Digging tests are performed with a miniature test device and a simulation model by two-dimensional distinct element methods (2D-DEM). The device and the simulation assess the effectiveness of the digging algorithm. It is quantitatively shown that the digging performance obtained by the feedback digging system is improved to prevent growing of reaction force.

The purpose of this study is to characterize the brake torque variation (BTV) of the developed brake system using wave type brake disc. The brake torque was fluctuated when the pad passed at the point of the wavy shape. The indentation of the pad into the space of wavy shape was observed. These results indicate that remarkable peak of the BTV of the wave type brake disc was related with the pad deformation. In the devised test, remarkable peak of the BTV of the wave type brake disc was decreased by insertion of spacers. This paper proposed an effective aspect to prevent the BTV of the wave type brake disc.

This paper describes the results of on-board measurement of engine performance and emissions in diesel vehicle operated with bio-diesel fuels. Here, two waste-cooking oils were investigated. One fuel is a waste-cooking oil methyl esters. This fuel is actually applied to a garbage collection vehicle with DI diesel engine (B100) and the city bus (B20; 80% gas oil is mixed into B100 in volume) as an alternative fuel of gas oil in Kyoto City. Another one is a fuel with ozone treatment by removing impurities from raw waste-cooking oils. Here, in order to improve the fuel properties, kerosene is mixed 70% volume in this fuel. This mixed fuel (i-BDF) is applied into several tracks and buses in Wakayama City. Then, these 3 bio-diesel fuels were applied to the on-board experiments and the results were compared with gas oil operation case.

Changes to OBDII regulations in North America are requiring more frequent leak checks to the evaporative emissions system. Conventional methods are unable to comply with the required 0.26 performance ratio due to various factors such as unstable tank pressure and fuel evaporation. These strict regulations require an innovative detection device. Utilizing a vacuum pump, a leak check module with high detection frequency, leak diagnostic accuracy, and reliability has been developed. In the present paper, the details of ELCM based on the depressurization method are reported together with the results of study on the pressurization method.

In order to reveal the mechanism of noise generation from CVT (Continuously Variable Transmissions) using a dry hybrid V-belt, the power spectrum of sound from a two-pulley CVT system and its variation with respect to rotational speed were measured. The experimental results showed that the frequency of the first peak in the power spectrum of the observed sound linearly increased with increasing the rotational speed of the pulley. The sound frequency of the first peak coincides with the frequency derived from the belt block pitch and the belt speed. Then, sound intensity analyses were conducted to identify noise sources of CVT. The experimental results reveal that unpleasant sound whose frequency is high occurs due to the collision or slip between CVT blocks and the pulley groove at the entrance and the exit of V-groove pulleys. Pulley surface roughness strongly affects the noise level. Additionally, the location of noise source varies due to surface roughness of the pulley groove.

The maximum liquid-phase penetration and vaporization behavior was investigated by using simultaneous measurement for mie-scattered light images and shadowgraph ones. The objective of this study was to analyze effect of variant parameters (injection pressure, ambient gas condition and fuel temperature) and fuel properties on vaporization behavior, and to investigate liquid phase penetration for the single- and multi-component fuels. The experiments were conducted in a constant-volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector.

In this study, a system to perform a parameter search of heavy-duty diesel engines is proposed. Recently, it has become essential to use design methodologies including computer simulations for diesel engines that have small amounts of NOx and SOOT while maintaining reasonable fuel economy. For this purpose, multi-objective optimization techniques should be used. Multi-objective optimization problems have several types of objectives and they should be minimized or maximized at the same time. There is often a trade-off relationship between objects and derivation of the Pareto optimum solutions that express the relationship between the objects is one of the goals in this case. The proposed system consists of a multi-objective genetic algorithm (MOGA) and phenomenological model. MOGA has strong search capability for Pareto optimum solutions. However, MOGA requires a large number of iterations.

Flash-boiling occurs when a fuel is injected to a combustion chamber where the ambient pressure is lower than the saturation pressure of the fuel. It has been known that flashing is a favorable mechanism for atomizing liquid fuels. On the other hand, alternative fuels, such as gaseous fuels and oxygenated fuels, are used to achieve low exhaust emissions in recent years. In general, most of these alternative fuels have high volatility and flash-boiling takes place easily in fuel spray, when they are injected into the combustion chamber of an internal combustion engine under high pressure. In addition, fuel design concept the multicomponent fuel with high and low volatility fuels has been proposed in the previous study in order to control the spray and combustion processes in internal combustion engine. It is found that the multicomponent fuel produce flash-boiling with an increase in the initial fuel temperature.

Two-layered clutch plates manufactured by a new process using BMC show a significant deflection. Two methods solving such deflection were alternatively developed in this study. Changing the composition of the clutch plate appeared to be useless while after-curing on deflected clutch plates was effective. Thermal cycles or high pressure for after-cure did not reduce the deflection. However, applying after-cure with a sloped mold reduce the deflection without increasing the disk density.

This work investigates the soot formation process in diesel jet flame using a detailed kinetic soot model implemented into the KIVA-3V multidimensional CFD code and 2D imaging by use of time-resolved laser induced incandescence (LII). The numerical model is based on the KIVA code which is modified to use CHEMKIN as the chemistry solver using Message Passing Interface (MPI). This allows for the chemical reactions to be simulated in parallel on multiple CPUs. The detailed soot model used is based on the method of moments, which begins with fuel pyrolysis, followed by the formation of polycyclic aromatic hydrocarbons, their growth and coagulation into spherical particles, and finally, surface growth and oxidation of the particles. The model can describe the spatial and temporal characteristics of soot formation processes such as soot precursors distributions, nucleation rate and surface reaction rate.

This study proposes a hybrid model which consists of modified TAB(Taylor Analogy Breakup) model and DVM(Discrete Vortex Method). In this study, the simulation process is divided into three steps. The first step is to analyze the breakup of droplet of injected fuel by using modified TAB model. The second step based on the theory of Siebers' liquid length is analysis of spray evaporation. The liquid length analysis of injected fuel is used for connecting both modified TAB model and DVM. The final step is to reproduce the ambient gas flow and inner vortex flow injected fuel by using DVM. In order to examine the hybrid model, an experiment of a free evaporating fuel spray at early injection stage of in-cylinder like conditions had been executed. The numerical results calculated by using the present hybrid model are compared with the experimental ones.

Supercharging system is obviously a necessary technology for heavy duty vehicular diesel to meet future stringent emission regulation as well as to improve fuel consumption characteristics. Although the conventional exhaust turbocharger system improves fuel consumption, there are some problems such as having a difficulty in improving starting acceleration and smoke emission characteristic because the response of an exhaust supercharger is not enough. On the other hand, the conventional mechanical supercharging system seems to be a quite effective aid for acceleration ability. However, it does not satisfy demand for low fuel consumption characteristic.

In the present study, we have proposed a novel fuel design concept in order to achieve low emissions and combustion control in engine systems. The fuel design concept is based on the combustion control that could be realized by using a mixed fuel with a lower boiling point fuel, such as gasoline or gaseous fuel components and a higher boiling point fuel, such as gas oil or fuel oil components. According to the fuel design concept proposed in this work, the characteristics of vaporization during mixture formation process as well as of combustion can be reasonably improved due to the formation of two-phase region. The heat release analysis was conducted to compare the temporal history of heat release for both a mixed fuel and a single component fuel that has the same transport properties of mixed fuels. In addition, the two-color method, which simultaneously allows the measurements of temperature distribution and soot concentration, is applied to the combustion field for mixed fuels.

Generally, it is well known that road noise generated by vibration from automobile tires and suspensions can be reduced by changing the stiffness of the rubber mounts installed in the suspension systems. Such stiffness, however, is rarely changed to avoid riding discomfort and so on. In this paper, a stiffness optimization method for suspension system rubber mounts that reduces road noise, and improves riding comfort as well, is presented. In the process, Road Noise Contribution Analysis (RNCA) is applied to the target vehicle to specify the major factors of road noise. Furthermore, the suspension system of the vehicle is investigated by Sensitivity Analysis using Measured FRF data (SAMF) to identify the optimal stiffness combination of rubber mounts. As a result, an effective stiffness combination of two mounts is specified to reduce road noise and to improve riding comfort.

The mixed fuel composed of two kinds of fuel oil whose boiling temperature is different each other forms the fine spray with minute droplets when its condition crosses over the two-phase region. It is expected that the fuel with low volatility dominates the ignition delay and that with high volatility does the generation of particulate matter. The experiments were carried out in a rapid compression and expansion machine and in an actual high-speed small sized diesel engine by use of this kind of fuel. The experimental results prove this expectation.