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Chemical kinetic mechanism of compression ignition with PRF (iso-octane/ n-heptane) and NTF (toluene/ n-heptane) is investigated according to crank angle resolved in-cylinder sampling experiments. Profiles of two-stage consumption of fuel components in accordance with the timings of heat releases have been obtained. As well, production and consumption of intermediate species were observed. It was found that toluene consumption at the first stage is considerably less than that of n-heptane, whereas iso-octane consumption is comparable to that of n-heptane, which is accounted for by the smaller rate constant of toluene with OH. N-heptane and iso-octane are considered to produce formaldehyde; however, toluene has no or little contribution.

Intermediate species formed in the cool ignition stage of autoignition were evaluated by exhaust gas analysis with FT-IR in a test engine at hot ignition suppressed conditions. PRF (iso-octane/n-heptane) and NTF (toluene/n-heptane) were used as the fuels. The fuel consumption rate decreases with increasing iso-octane content in PRF and toluene content in NTF. HCHO generation rate increases with increasing iso-octane content in PRF but the opposite trend was found in NTF. These tendencies correspond to the difference in the detail reaction mechanism for PRF and NTF oxidation.

The chemical mechanism responsible for controlling ignition timing by using additives in HCCI has been investigated. Dimethyl ether (DME) and methanol were used as the main fuel and the additive, respectively. Fuel consumption and intermediate formation in the first stage (cool ignition) were measured with crank angle resolved pulse-valve sampling and exhaust gas analysis, where HCHO, HCOOH, CO, H2O2 and other species were detected as the intermediate. The effect of methanol addition retarding ignition is represented by an analytical model in which the growth rate of the chain reaction is reduced by the methanol addition.

The Poly-Aromatic Hydrocarbon (PAH) formation process from benzene was studied using a laminar flow reactor and GC-MS. In addition to PAH, acetylene and ethylene were observed. Without oxygen at temperatures over 1070 K, the amount of PAH and C2 species increased as the benzene concentration decreased. Addition of oxygen caused a linear decrease in the benzene concentration, and almost all of the benzene was consumed under stoichiometric conditions at all temperatures. At 1053 K, the concentrations of PAH and C2 species were not affected by the addition of oxygen. On the other hand, when the temperature was greater than 1070 K, the amount of PAH formed increased as the equivalence ratio increased, until the equivalence ratio was about 4. Above this equivalence ratio, the amounts decreased. Amounts of phenanthrene and biphenyl were large compared to those of other PAHs, which indicated that the dominant PAH formation path is the formation of phenanthrene via biphenyl.

Supersonic jet / resonance enhanced multi-photon ionization (Jet-REMPI) technique was focused on the analyzing method for gas mixture like exhaust gas from automobiles. In this method, when the mass number and wavelength of excitation laser are determined adequately, the target compound can be monitored selectively. We developed a new analyzer utilizing REMPI method. Using this analyzer, real-time monitoring of exhaust gas from a motorcycle and diesel vehicles was conducted. As a result of real-time monitoring test of the vehicles, concentrations of aromatic compounds like benzene toluene etc. were quantified and real-time changes of their concentrations were observed.

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.

Recently, particulate matter (PM) emission from internal combustion engines, especially particles having the diameter of less than 100 nm (Nano-particles) are being considered for their potential hazards posed to human health and the environment. Nano-particles are unstable and easily influenced by the conditions of engine operation and measurement techniques. In this study, the influences of cooling and dilution processes on nano- particles are presented to understand the generation and dilution mechanisms, and to further development of an accurate measurement method. It is found that the thermo-dilurter is necessary for measuring the nano-particles with higher accuracy. Accurate measurement of nano-particles requires immediate dilution of the exhaust gases by hot air.

The authors have developed a new partial flow dilution tunnel (hereafter referred to as PPFT), whose principal device is a flux splitting gas divider, as a new means of measuring particulate emissions which can be applied to transient cycle testing of diesel engines. The advantage of this system is that it can achieve perfect constant velocity splitting by means of its structure, and theoretically can also maintain high splitting performance despite fluctuations in the exhaust flow rate, including those due to engine exhaust pulsation. We compared this system with a full tunnel by analyzing the basic performance of the system and measuring particulate matter (PM) using an actual vehicle engine.

A simplified reaction model of dymethyl ether (DME) oxidation has been developed by extracting essential elementary reactions from a previous detailed mechanism. It consists of 23 reactions for 23 species without modification of rate coefficients in low temperature oxidation of the original model. Spatially non-dimensional calculations were conducted along with HCCI compression profiles using SENKIN code in CHEMKIN package. Good agreement with the detailed model was obtained in terms of ignition timing and profiles of species such as DME, HCHO, O2, H2O2, and CO as functions of intake gas temperature, equivalence ratio, and intake pressure. Adding a few reactions to the mechanism, the effective range of the model was extended to rich side, where CO emission is significant. Effect of methanol addition as an ignition suppressor was also properly described.

The use of a Thermo-Denuder (TD) is proposed to suppress the nano-particle measurement fluctuations caused by the volatile components in the available techniques. The problems encountered during the use of thermo-denuder for nano-particle measurement and their respective solutions are suggested. The behavior of nano-particles in the TD itself is not clearly understood but the thermo-denuder influences both the volatile and solid particles. As a first report, only the effect of TD dimension on solid nano-particle measurements is presented. It is concluded that the TD influences the nano-particles i.e. loss of particles occurs even the sample gas contains no volatile fractions. A sharp temperature gradient between the low temperature wall of the absorption part of TD and hot sample gas causes particle losses due to thermophoresis effect. Especially the smaller particles are affected significantly.

The cordierite filter has been widely studied because of it's inherent, high capacities in the collection efficiency and heat-resistance. During the regeneration process of a cordierite filter, failure of ignition or incomplete burning propagation occurs, and additionally melts or cracks develop sometimes. In this study, the problems stated above are considered from a new standpoint, and a regeneration method that does not strictly depend on accumulated soot quantity is discussed. A filter made of SiC (Silicon carbide) possesses the requisite electric resistance and it's possible to heat it uniformly by using electricity. Accumulated soot can be uniformly incinerated not by burning propagation but by simultaneous ignition and burning of all accumulated soot. Silicon carbide has a higher resistance to heat than cordierite. Therefore, a self-heating filter made of SiC makes it possible to regenerate the filter in a wider range of accumulated soot.

Degradation of the deNOx performance has been found in in-use heavy-duty vehicles with a urea-SCR system in Japan. The causes of the degradation were studied, and two major reasons are suggested here: HC poisoning and deactivation of pre-oxidation catalysts. Hydrocarbons that accumulated on the catalysts inhibited the catalysis. Although they were easily removed by a simple heat treatment, the treatment could only partially recover the original catalytic performance for the deNOx reaction. The unrecovered catalytic activity was found to result from the decrease in conversion of NO to NO2 on the pre-oxidation catalyst. The pre-oxidation catalyst was thus studied in detail by various techniques to reveal the causes of the degradation: Exhaust emission tests for in-use vehicles, effect of heat treatment on the urea-SCR systems, structural changes and chemical changes in active components during the deactivation were systematically investigated.

Conditioning of diluted exhaust gas by Thermo-Conditioner prior to measurement has been proposed by the GRPE/PMP Research Council of the United Nation in order to achieve stability in nano-particle measurement. In this study the effect of thermo-conditioner on the thermo-physical behavior of nano-particle under different conditions have been clarified. Stability in measurement was also attempted depending on the characteristics of nano-particles. Quality of the raw exhaust gas, the dilution ratio and temperature, and the thermal conditioning temperature were considered as the main parameters. Exhaust gas from a medium duty DI diesel engine was used for analysis. Scanning Mobility Particle Sizer was used for measuring the concentration of nano-particles. It was concluded that the concentration of nuclei-mode particles within the size range of 15∼30 nm are significantly influenced by the thermal conditioning temperature.

Two different species measurements have been conducted for compression ignition of dimethyl ether in a motored engine. Crank angle resolved pulse-valve sampling with a resolution improvement scheme enabled to detect partial fuel consumption and formation of intermediate like H2O2 and HCHO at a cool ignition, as well as their total consumption at a hot ignition. FTIR analysis of exhaust gas in single cool ignition conditions confirmed formation of HCOOH and HCOOCH3 in cool ignitions. Results obtained in a range of equivalence ratio support the advantage of 2000 version of Curran et al. DME oxidation model.

Multi-stage heat releases in homogenous charge compression ignition (HCCI) near the ignition threshold are analyzed in this study. Motored engine experiments are conducted with exhaust gas analysis by Fourier transform infrared spectrometer under hot ignition suppressed condition, in order to provide a deeper insight into the ignition mechanism of n-heptane. By increasing intake temperature from room temperature, heat release of low temperature oxidation (LTO) can be observed. Moreover, second heat release was observed after primary heat release of LTO, which increases rapidly with increasing intake temperature within narrow range below the high temperature oxidation (HTO) threshold. The mechanism of HTO preparation reaction is discussed.

Exhaust gas analysis has been conducted for a test engine operated in HCCI mode at hot ignition suppressed condition, to detect intermediate species formed in low temperature oxidation (LTO). PRF (isooctane/ n-heptane) and NTF (toluene/ n-heptane) were used as fuel mixtures. The LTO fuel consumption decreases with increasing iso-octane content in PRF and toluene content in NTF, but only NTF showed a nonlinear effect. These tendencies were reproduced by O-D and 3-D simulations with detailed chemistry; however, quantitative differences were found between chemical models. The essential mechanism of high octane number fuel affecting the ignition property of n-heptane is discussed by developing a simplified model summarizing chain reaction of LTO, in which OH reproduction and fuel + OH reaction rate play important roles.