This work focuses mainly on the use of laboratory flames to study high temperature nanoparticle formation by hydrocarbon combustion. Particular attention is placed on incipient particles formed in high temperature combustion conditions, which may serve as condensation sites for volatile species as the exhaust plume cools. Several different measurement methods are used to determine the size and chemical composition of particles in situ in high temperature flames, on-line in diluted sample flows, and off-line on dispersions in water or other solvents or on particles deposited on filters or substrates as a sparse deposition or a thick layer. Consistent observations by a wide range of measurement methods has created a consensus in the combustion community that organic nanoparticles are formed in high temperature combustion reactions, in addition to soot. The relative properties of combustion-generated organic nanoparticles and soot are discussed.
Emission standards for diesel engines have been tightened all over the world since diesel engine exhaust emissions contribute significantly to urban and global pollution. The use of fuel additive has been proposed as a cost-effective strategy for reducing pollutant emissions from diesel-powered engines. This paper introduces a possible mechanism of the catalytic reactions in the combination of platinum and cerium in diesel engine, and also shows an example of the actual use of a platinum-cerium bimetallic fuel additive for a diesel engine. Possible mechanism is suggested as follows; the soot oxidation occurs on Pt utilizing oxygen, and also occurs on Ce consuming nitrogen dioxide. A previous study showed that 54% of elemental carbon, 23% of organic carbon, and 34% of PM2.5 were reduced when 0.13 ppm Pt and 7.5ppm Ce of the additive were used. The investigation of long-term effect for the diesel emission characteristics associated with the use of the fuel additive and other pollution control technologies is needed for further study.
In this paper, recent advances on the temperature measurement technique for application to the combusting flame are briefly reviewed, and two new flame temperature measurement techniques are described, such as the laser speckle technique and the flame reaction technique. These techniques are non-intrusive, and they can measure simultaneously multiple points in the flame. The former technique relies on the laser speckle pattern for the measurement of reflective-index distribution in the flame, which is a function of the temperature, while the latter technique is based on the visualization of the flame by flame reaction technique combined with the statistical thermodynamic consideration. Examples of the temperature measurements are given for the dilute hydrogen flame by laser speckle technique and for the flickering premixed methane/air flame by the flame reaction technique.
The laser induced Exciplex fluorescence (EXCIPLEX) technique proposed by Melton is based on the TMPD/Naphthalene system. The Exciplex fluorescence from liquid phase and Monomer TMPD fluorescence from vapor phase can separately visualize the both phases simultaneously. The objective of the present study is to develop an applicable method to the fuel vapor visualization in fuel spray. Firstly, the spatial distributions of liquid and vapor in a fuel spray suspended by ultrasonic waves were visualized by the EXCIPLEX technique. In this measurement, however, we found that the EXCIPLEX technique has various disadvantages. In addition, the fluorescence intensity from vapor phase was very weak. Instead of the method, therefore, we proposed a new laser induced Excimer fluorescence (EXCIMER) technique to visualize the liquid and vapor phases simultaneously. We choose the fluorescent molecule and examined the characteristics of Monomer and Excimer fluorescence spectra. We compared the EXCIMER technique with the EXCIPLEX technique and evaluated the EXCIMER technique. Finally, we investigated the correlation between fuel vapor concentration and fluorescence intensity by measuring the fluorescence intensity of saturated vapor formed over liquid fuel with a controlled temperature, and attempted the quantitative measurements of the fuel vapor concentration. (189 Words)
We developed an instrument which determines the sizes of sprayed droplets with a high-accuracy. By applying this instrument to the measurement of droplets formed by spraying kerosene (JIS K 2203), we found that the Sauter diameter ranged from 8 to 35 μm and that the mean diameter was almost in agreement with the diameter of droplets generated by other general spray methods. Furthermore, we observed the droplets passing through a diffusion flame formed by the combustion of butane and found the relationship between the droplet velocity and droplet diameter.
We previously reported that the airborne fine allergenic particles of Japanese cedar pollen were high in concentration during sunny days after rainfall. In this study, we investigated the morphological change of Japanese cedar pollen grains due to the contact with raindrops, and the elution behavior of major pollen allergenic Cry j 1, based on the assumption that rainfall may promote the release of fine allergenic particles from airborne pollen grains.
The observation of raindrops showed that a great number of pollens were scavenged at the initial stage of precipitation and that many burst pollen grains were contained in the rainwater. Therefore, it was suspected that the fine allergenic particles included in fragment of cell wall and ingredients of pollen were released from the burst of pollen grains.
On the other hand, the elution of allergenic Cry j 1 was found to increase when the solution contained high concentrations of ionic species. Especially, elution of allergenic Cry j 1 was significantly increased when the pollens were soaked with a weak basic solution containing Ca2+ ion. It was also found that high ionic concentration and high pH values appeared in rainfall water during the rainfall after long range transportation events of Asian dust. Therefore, we think that one of the important factors for releasing fine allergenic particles is the contact with the rainfall which scavenged Asian dust experienced a long range transportation.
We continuously measured cloud condensation nuclei (CCN) concentration (NCCN) with six different supersaturation conditions (SS=0.10, 0.17, 0.24, 0.31, 0.38, 0.44%) at the summit of Mt. Fuji from July. 17 to Aug. 25, 2010. Using backward trajectory analysis (NOAA HYSPLIT MODEL), types of air masses were classified according to the region and altitude. It was expected that the summit of Mt. Fuji was located in the free troposphere when the air masses came from a higher altitude than that of Mt. Fuji (3776 m a.s.l.). When the summit of Mt. Fuji was located in the free troposphere, NCCN was lower by 20%~50% than that under the other condition. However, continental air masses that came from China had a larger NCCN. The continental air masses at the summit of Mt. Fuji and other areas were similar in the shape of CCN spectra. We speculated that CCN concentration may be influenced by the long-range transport of pollution from the continent when the summit of Mt. Fuji is located in the free troposphere.
Monitoring of aerosol number concentration is important in detecting environmental contamination and controlling air quality. The atmospheric aerosol number concentration always exhibits time variation due to the natural causes such as weather, wind (direction and velocity) and atmospheric stability, and therefore it is difficult to attribute an unexpected increase in aerosol number concentration to a certain causes other than the natural ones. This paper employed the FUMI theory (Function of Mutual Information) to analyze the natural time variation and estimated the detection limit. If an observed value exceeds the detection limit, the null hypothesis that the observed signal comes from non-natural causes would not be denied. The FUMI theory has been used in the field of analytical chemistry to estimate detection limits of a variety of instrumental analyses, and this paper examines whether the FUMI theory is applicable to aerosol time variation which is not necessarily the same as the background noise of analytical instruments. This paper demonstrates that the FUMI theory can be used in an aerosol monitoring system to detect a signal from non-natural causes with a satisfactory precision.
We previously reported the investigation of 20 ingredients of VOCs at the Tateyama Murodo (altitude : 2,450m) and Tateyama Gondola (altitude : 1,180m) in Mt. Tateyama area from August to October 2007 [J. Environ. Chem., 19, 41-54 (2009)]. In the present work, a newly introduced GC-MS with a high sensitivity was applied to analyze 30 ingredients in VOCs sampled from the same area from August 16 to October 30 in 2009. Twenty-five components of 30 VOCs were detected, and benzene, toluene, and ethyl benzene showed higher average values among the detected VOCs. From the result of back trajectory analysis, the East Asia source occupied 48% at Tateyama Murodo and 37% at Tateyama Gondola. The average value of all VOCs at both points were lower than those at urban areas. We have compared the concentrations at both measuring points with the background data at Cape Hedo in Okinawa. Although the concentration of toluene was almost equal to or slightly lower than that of Cape Hedo, the other detected VOCs had a concentration equivalent or slightly higher than Cape Hedo. It was found that benzene/toluene ratios of the East Asia source were higher than those of the other sources.