Terunao Kawai

Comparative Measurement of Nano-Particulates in Diesel Engine Exhaust Gas by Laser-Induced Incandescence (LII) and Scanning Mobility Particle Sizer (SMPS)

Particulate Matter (PM) from diesel engines is thought to be seriously hazardous for human health. Generally, it is said that the hazard depends on the total number and surface area of particles rather than total mass of PM. In the conventional gravimetric method, only the total mass of PM is measured. Therefore, it is very important to measure not only the mass of PM but also size and number density of particulates. Laser-Induced Incandescence (Lll) is a useful diagnostic for transient measurement of soot particulate volume fraction and primary particle size. On the other hand, Scanning Mobility Particle Sizer (SMPS) is also used to measure the size distribution of soot aggregate particulates at a steady state condition. However, the measurement processes and the phenomena used to acquire the information on soot particulate are quite different between the Lll and SMPS methods. Therefore, it is necessary to understand the detailed characteristics of both Lll and SMPS. In the present study, the size distributions of PM from Dl diesel engine are measured by both Lll and SMPS simultaneously. In addition, PM mass emission is measured gravimetrically through a dilution tunnel and is separated into SOF and ISOF. The effects of EGR rate and engine load on the results of these particulate measurements are investigated. The different trends in the characteristics of PM emission are shown in each measurement methods for PM. The difference of detailed characteristics between Lll and SMPS are illustrated by comparing the measurement results for the particulates. Finally, the problems associated with the measurements using each method are considered and some recommendations have been given for accurate measurement of nanoparticles.

Real-Time Measurement of Particle Size Distribution From Diesel Engines Equipped With Continuous Regenerative DPF Under a Transient Driving Condition

A new PM measurement method, such as particle measurement equipments, samplings and so on, is being studied at present for a type approval test in the future. Particles emitted from diesel engines, especially the particles that are called Nuclei Mode Particles are very unstable and easily influenced by the engine operating conditions and the measurement conditions. Most of nuclei mode particles are said to consist of volatile organic particles with mainly high carbon numbers. It is said that a continuous regenerative type DPF (Diesel Particulate Filter) consisting of oxidation catalyst and ceramic filter will prevail in the near future. These particles may be able to be reduced by an oxidation catalyst in this DPF. The objectives of this study is to investigate the behavior of nuclei mode particles in DPF (CRT, Continuous Regenerative Trapper) that will prevail and to clarify the collection performance of DPF for nuclei mode particles by using a fast particle sizer (DMS500) which can measure particle size distributions in real time. The transient particle size distribution behaviors were measured in real time by DMS500. It was shown that an oxidation catalyst in CRT reduced nuclei mode particles in the condition of more than 200 Celsius degree exhaust gas temperature but did not reduce them in less than 200 Celsius degree. The particle number concentrations reduced to about 1/100 by DPF.

Fundamental Study of Single Droplet and Droplets Array Combustion with Premixed Gas

In the actual spray combustion fields, coupled combustion process should be occurred, between the pre-evaporate fuel component and remaining liquid droplets. Therefore it is insufficient to clarify the fundamental spray combustion mechanism with use of only droplet or only premixed mixture analyze method. In this study, the premixed mixture-droplets coupled combustion field was focused, as a model of the actual spray combustion field. In the experiments, the effect of the flame pattern and the burning rate constant by the interference between the droplets were clarified with the variation of droplets fuel. Besides, effect of the premixed gas surrounding the droplets was clarified by the experiment on coupled combustion. The experiments were carried out under the normal gravity field and the microgravity field to estimate the effect of convection in combustion field.

Three-Dimensional In-Cylinder Flow-Field Structure before and after Distortion of Tumble.

The influence of tumble intensity on the three-dimensional flow-field structure was analyzed numerically using the STAR-CD code. It was found that when the tumble intensity is extremely high, because the velocity component in the direction of the axis of tumbling air motion is small, the flow-field structure can be treated as two-dimensional. When the tumble intensity is moderate or weak, however, various flows in the direction of the tumble axis can be observed. Therefore, such a flow-field structure should be treated as three-dimensional. A new method to measure the three instantaneous velocity components from a two-dimensional photograph was developed. By using three laser sheets composed of two continuous and one pulse laser light source with different colors radiated for preset durations and timings, velocity in the direction of the laser sheet depths can be derived. Employing this method, the flow-field structure at 15°BTDC was analyzed. It was confirmed that the distortion of tumble induces horizontal vortices in addition to the vertical vortex.