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Journal Article

Visualization of Oxidation of Soot Nanoparticles Trapped on a Diesel Particulate Membrane Filter

Through microscopic visualization experiments, a process generally known as depth filtration was shown to be caused by surface pores. Moreover, the existence of a soot cake layer was an important advantage for filtration performance because it could trap most of the particulates. We proposed an ideal diesel particulate filter (DPF), in which a silicon carbide (SiC) nanoparticle membrane (made from a mixture of 80 nm and 500 nm powders) instead of a soot cake was sintered on the DPF wall surface; this improved the filtration performance at the beginning of the trapping process and reduced energy consumption during the regeneration process. The proposed filter was called a diesel particulate membrane filter (DPMF). A diesel fuel lamp was used in the trapping process to verify the trapping and oxidation mechanisms of ultrafine particulate matter. Thus, the filtration performance of the membrane filters was shown to be better than that of conventional DPFs.
Technical Paper

Visualization Study of PM Trapping and Reaction Phenomena in Micro-structural Pores through Cross Section of DPF Wall

Trapping of diesel particulates and phenomena of chemical reaction in regeneration were investigated by visualization through the cross-sectional area of a diesel-particulate-filter wall, using a digital-microscope with a high focusing depth. Herein, SiC-DPF walls were polished up to make a uniform height and to create a mirror-like surface on each SiC-particle-grain. At the beginning of the trapping process, it was observed that large particulates were trapped once in the small pores inside the wall, and then, since the flow-pattern was changed drastically, the trapped particulates were pushed out and blown off again, and finally, trapped in a region further downstream. As time passed, image analysis disclosed that since fine particulates were deposited around the SiC-particle-grain surface, the flow-channels became increasingly narrow.
Technical Paper

The influence that the disclosure of idling noise exerts on HRV and respiratory frequency

The sense of a human being is expressed in a word always with the sensuous evaluation to idling noise. However, due to the sense of the human being is very complicated basically and be including delicate elements, there is a limit to express it in a word. Also, idling noise might be giving a stress to our body, without feeling it. Then, several studies have been made on physiological information receive the response of a human being objectively, tried to evaluate the load of a body. Electrocardiogram (ECG) and respiratory curve were measured to examine the influence that the disclosure of idling noise exerts on the autonomic nervous system function in this study. Heart rate variability (HRV) was obtained from ECG and respiratory frequency was obtained from respiratory curve in the analysis. Seven subjects were adult males who were healthy hearing. We investigated the result with considering the differences by 4 kinds of noise and 2 kinds of sound pressure.
Technical Paper

The Effect of Exhaust Gas Recirculation on Performance and Emission of Ethanol Fumigated Diesel Engine

Primary energy source such as fossil fuel keep decreasing due to various kind of usage. According to less amount of the fossil fuel, human seeks for an alternative fuel source such as alcohol. Alcohol like ethanol can be produced easily from strarchy plant. But using alcohol as blended fuel with diesel fuel doesn't work well because alcohol has low cetane number, lack of lubricity and very low miscibility with diesel fuel. To overcome this, fumigation system or port fuel injection of alcohol seems interesting. Although it requires more complicate system but it can compensate the miscibility issue and alcohol can be used in higher dose to give more energy. Diesel engine produces a lot of emission such as NOx and some other carbon content emission like HC, CO and soot due to they run in lean condition as their characteristic. Modern diesel engines are now coupled with exhaust gas recirculation system to help reduce in main emission like NOx.
Technical Paper

Soot Oxidation Characteristics of SiC Nanoparticle Membrane Filters

A diesel particulate membrane filter (DPMF) has good trapping efficiency of soot and reduces the pressure loss through the soot accumulation process on the diesel particulate filter wall. The activation energy reduction effect of the soot oxidation reaction by DPMF was clarified. The membrane consists of SiC nanoparticles with a diameter of 10-100 nm. A thin oxide layer is formed on the SiC particle surface, and nanoscale noble metal particles are distributed on the surface. The reduction mechanism for the activation energy was investigated in detail. Nanoscale soot was accumulated on DPMF from a diesel lamp. Furthermore, the soot oxidation in the regeneration process was observed using an optical microscope. An Arrhenius plot was made from the change of the concentration of the product gases CO and CO₂ with respect to time. The performance and the temperature dependence of oxygen desorption on the oxide layer was measured by thermal desorption spectroscopy (TDS).
Technical Paper

Solar Furnace System Using Tower-Reflector with Ellipsoidal Mirror

A new solar furnace system using a stationary elliptic dish and heliostats is proposed. Since the elliptic dish has two focuses (an upper focus and a lower focus) for elliptic geometry, this system has three advantages. The first is enable to fix a solar reactor on the ground, the second to expand the heliostat field largely, and the third to concentrate the direct solar radiation in a small area around the lower focus. The horizontal deviation from the lower focus of the direct solar radiation was estimated within ±1.2m for the heliostat field of 100m and the tower-reflector height of 70m. The system using the elliptic dish and heliostats is available as high-concentration system due to large scale of solar energy.
Technical Paper

Simultaneous Optimum Design Method for Multiple Dynamic Absorbers to Control Multiple Resonance Peaks

‘Three kinds of new simultaneous optimum design methods of plural dynamic absorbers are proposed. These methods allow the optimum tuning in many natural modes of multiple degrees of freedom structures or a continuous bodies simultaneously to effectively suppress vibration. Changes of natural modes and natural frequencies of the main structure due to added mass effect of dynamic absorbers can be taken into account in the design. Validity and usefulness of the proposed methods are verified by both a computer simulation and by experiments.
Technical Paper

Simultaneous Measurements of the Components of VOCs and PAHs in Diesel Exhaust Gas using a Laser Ionization Method

A simple real-time measurement system for the components of volatile organic compounds (VOCs) and polyaromatic hydrocarbons (PAHs) in automobile exhaust gas using a laser ionization method was developed. This method was used to detect VOCs and PAHs in the exhaust gas of a diesel truck while idling, at 60 km/h, and in the Japanese driving mode JE05. As a result, various VOCs and PAHs, such as xylene and naphthalene, were simultaneously detected, and real-time changes in their concentration were obtained at 1 s intervals.
Technical Paper

Simultaneous Measurements of Temperatures of Flame and Wall Surface in a Combustion Chamber of Diesel Engine

In order to investigate the combustion phenomena in a combustion chamber of the diesel engine at transient operations, the simultaneous measurements of temperatures of flame and wall surface in a combustion chamber were conducted. The new technique for simultaneous measurements of flame temperature and wall surface was developed. Laser-Induced phosphorescence was used for the measurement of wall surface temperature which was coupled with the flame temperature measurement by a two-color pyrometry. The NOx and soot emissions were also measured simultaneously in transient operations. The relation between the temporal changes of emissions and temperatures of flame and surface wall are discussed. The results show that the temporal change of NOx emission during transient operation is similar to that of the average gas temperature in a chamber. On the other hand, the temporal change of soot emission is similar to neither that of flame temperature nor that of average gas temperature.
Journal Article

Simultaneous Measurements of Aromatic Hydrocarbons in Exhaust using a Laser Ionization Method

A simultaneous multi-composition analyzing (SMCA) resonance enhanced multi-photon ionization (REMPI) system was used to investigate gasoline engine exhaust. Observed peaks for exhaust were smaller mass numbers than those from diesel exhaust. However, large species up to three ring aromatics were observed suggesting that soot precursor forms even in the gasoline engine. At low catalyst temperature condition, the reduction efficiencies of a three-way catalyst were higher for higher mass numbers. This result indicates that the larger species accumulate in the catalyst or elsewhere due to their lower vapor pressures. To evaluate the emission of low volatility species, the accumulation should be taken into account. In the hot mode, reduction efficiencies for aromatic species of three-way catalyst were almost 99.5% however, they fall to 70% in the cold start condition.
Technical Paper

Simultaneous 2-D Imaging of OH Radicals and Soot in a Diesel Flame by Laser Sheet Techniques

The OH and soot in an unsteady flame, which was achieved in a rapid compression machine, were visualized simultaneously by the laser-induced fluorescence and laser-induced scattering techniques. The fuel mixture consisting of 90% paraffin hydrocarbon (reference fuel) and 10% polypropylene-glycol was used to reduce the optical attenuation caused by dense soot cloud. The simultaneous images of the fluorescence from OH and scattering from soot show that the soot and OH exist separately from each other in the leading portion of the spray flame, and the OH is formed earlier than the soot in the near field region of spray flame.
Technical Paper

Scanning Electron Microscopic Visualization of Transition from Surface Pore Filtration to Cake Filtration Inside Diesel Particulate Filter Walls

Surface pores that are open to the inlet channel below the surface play a particularly important role in the filtration of particulate matter (i.e., soot) inside the walls of a diesel particulate filter (DPF); they are closely related to the pressure drop and filtration efficiency through the DPF as well as the performance of the regeneration process. In this study, a scanning electron microscope (SEM) was used to dynamically visualize the soot deposition process at the particle scale as “time-lapse” images corresponding to the different increases in the pressure drop at each time step. The soot was first trapped at the deepest areas of the surface pores because the porous channels in this area were constricted by silicon carbide grains; soot dendrite structures were observed to grow and finally cause obstructions here.
Journal Article

Scanning Electron Microscopic Visualization of Bridge Formation inside the Porous Channels of Diesel Particulate Filters

Time-lapse images of particulate matter (PM) deposition on diesel particulate filters (DPFs) at the PM-particle scale were obtained via field-emission scanning electron microscopy (FE-SEM). This particle scale time-series visualization showed the detailed processes of PM accumulation inside the DPF. First, PM introduced into a micro-pore of the DPF wall was deposited onto the surface of SiC grains composing the DPF, where it formed dendritic structures. The dendrite structures were locally grown at the contracted flow area between the SiC grains by accumulation of PM, ultimately constructing a bridge and closing the porous channel. To investigate the dominant parameters governing bridge formation, the filtration efficiency by Brownian diffusion and by interception obtained using theoretical filtration efficiency analysis of a spherical collector model were compared with the visualization results.
Technical Paper

Real-time Analysis of Benzene in Exhaust Gas from Driving Automobiles Using Jet-REMPI Method

Real-time analysis of benzene in automobile exhaust gas was performed using the Jet-REMPI (supersonic jet / resonance enhanced multi-photon ionization) method. Real-time benzene concentration of two diesel trucks and one gasoline vehicle driving in Japanese driving modes were observed under ppm level at 1 s intervals. As a result, it became obvious that there were many differences in their emission tendencies, because of their car types, driving conditions, and catalyst conditions. In two diesel vehicle, benzene emission tendencies were opposite. And, in a gasoline vehicle, emission pattern were different between hot and cold conditions due to the catalyst conditions.
Technical Paper

Real Time Identification and Classification of Road Surface with Neural Network

Two methods have been developed for real time identification and classification of the roughness pattern of road surfaces using the neural network. These methods are directly available both for semi-active and active vibration controls of cars. Accelerations of the rear wheel axis under the suspension are used as the input data for real time identification. The neural network which has acquired the informations of the seven typical roughness patterns is used for real time classification of actual road surfaces during driving. Validity and usefulness of these methods are verified by simulation.
Technical Paper

Quantitative Measurement of Fuel Vapor Concentration in an Unsteady Evaporating Spray via a 2-D Mie-Scattering Imaging Technique

The cross-sectional distribution of fuel vapor concentration in an evaporating spray was measured quantitatively by a new scattering imaging technique, silicone particle scattering imaging method, which was proposed in a previous paper[1]. When fuel containing silicone oil injected into a nitrogen environment at high temperature, the volatile base fuel in the droplets vaporized rapidly, leaving behind small droplets of silicone oil suspended in the vapor-gas mixture. The silicone oil droplets were illuminated by a thin laser sheet, and the scattered light was imaged by a CCD camera. The cross-sectional distribution of vapor concentration was estimated from the scattering image of the silicone oil droplets by Mie scattering theory. The results demonstrated clearly the inhomogeneity of the fuel vapor concentration. The distribution of vapor concentration was discontinuous, and islands of rich mixture with a scale of several millimeters existed in the center region of the spray.
Technical Paper

Quantitative Measurement of 2-D Fuel Vapor Concentration in a Transient Spray via Laser-Induced Fluorescence Technique

A new method to determine simultaneously the temperature and the fuel vapor concentration inside an evaporating spray was described by using a laser-induced fluorescence technique. A TMPD doped base fuel composed of C12H26: 22%, C13H28: 54% and C14H30: 30% was injected into the combustion chamber of a rapid compression machine which is filled with a high temperature and high pressure nitrogen. The laser sheet was used for incident light, which was reflected by a prism located inside the combustion chamber and propagated through the center of an evaporating spray. The laser induced fluorescence intensity was imaged by a high speed-gated intensifier from a direction perpendicular to the incident light. The results shows that mixtures with high equivalence ratio are observed in the central region, while low equivalence ratio mixtures are observed in the periphery of the spray. It is also observed that the temperature of richest mixture is 50 K as low as the surrounding gas temperature.
Technical Paper

Pyrene-LIF Thermometry of the Early Soot Formation Region in a Diesel Spray Flame

In order to investigate early soot formation process in diesel combustion, spectral analysis and optical thermometry of early soot formation region in a transient spray flame under diesel-like conditions (Pg2.8 MPa, Tg620-820K) was attempted via laser-induced fluorescence (LIF) from pyrene (C16H10) doped in the fuel. Pyrene is known to exhibit a temperature\-dependent variation of LIF spectrum; the ratio of S2/S1 fluorescence yields, from the lowest excited singlet state S1 and the second excited singlet state S2, depends on temperature. In the present study, pyrene was doped (1%wt) in a model diesel fuel (0-solvent) and the variation of LIF spectra from the pyrene in the spray flame in a rapid compression machine were examined at different ambient temperatures, ambient oxygen concentrations, measurement positions and timings after start of fuel injection.
Technical Paper

Polytopic topic Bilinear System Modeling and Nonlinear H∞ Control Design for Semi-Active Suspension System

As an important class of nonlinear system, polytopic bilinear system is investigated. Combined with the properties of convex polytope, the nonlinear control for polytopic bilinear system is formulated by synthesizing nonlinear H∞ controller which is designed for polytopic bilinear system at vertices. For a semi-active suspension system with controllable damping and variant stiffness elements, it is easily modeled as a polytopic bilinear system model. In this case, the desired nonlinear control properties are pursued in making effective use of the changeable damping property while the variant stiffness is taken as the affine parameter of polytopic model. Therefore, polytopic bilinear system model could be reduced to a feasible problem by polytopic convex decomposition. Then the control problem of bilinear system model is to find a solution of nonlinear H∞ control.
Technical Paper

Polytopic Modeling and State Observer Synthesis for Suspension System with Variant Damping and Stiffness

This paper presents the polytopic modeling method and state variable observer design approach for semi-active suspension with changeable damping and variant stiffness elements. And such semi-active suspension system is suitable to be modeled as a dynamic polytopic system where the extreme vertices of damping and stiffness values are taken as the convex vertices of polytope. Thus, a dynamic polytopic model is the convex synthesis with all the vertex system dynamics and linear system theory can be applied to the system at each vertex. Herein, the conventional Kalman filter theory is utilized to design the observer for each vertex system, then the polytopic observer is formulated by a convex synthesis. The proposed observer design approach is testified by numerical study and vehicle test.