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Periodic increases of PN, PM, and regulated gases associated with DPF regeneration from a heavy-duty truck equipped with a diesel particulate filter (DPF; non-SCR truck) and from a heavy-duty diesel engine equipped with a DPF and a urea-SCR (SCR engine) were investigated. Both met Japanese 2009 regulations. From both exhausts, PN emissions two orders of magnitude higher than the European legislation limit were observed in the regeneration cycle, and these emissions gradually decreased in subsequent cycles. This can be explained by the relation between the filtering efficiency and the amount of loaded soot in the DPF. No emissions particular to regeneration, such as soot fragments, were observed. In some cases, higher PN emissions were observed from the SCR engine. This may be because of the difference in DPF performance, but there is a possibility that some particles were produced in the urea-SCR system.

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.

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.

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.

Repeatabilities of PM measurements on a heavy-duty diesel engine equipped with a diesel particulate filter (DPF) using a filter weighing method and a number counting method with a full flow dilution system and a partial flow system were evaluated. The filter method with partial flow exhibited the best repeatability. However, a good correlation between the full flow and the partial flow number counting results suggests that the fluctuations observed using the number counting method were caused by changes in the engine exhaust. Applying a strict preconditioning procedure should improve the repeatability of the number counting method because this method is more sensitive than the filter weighing method. In addition, the effects of the specifications for the number counting method were evaluated. The results indicate that the hose length from the tip of the sampling probe to the inlet of the number counting system had a negligible effect.

The formation pathway for poly aromatic hydrocarbons (PAHs) has been studied by not only fundamental chemists but also motor engineers due to the formation of nanoparticle precursors and soot in vehicle emissions. In this study, the formation process of up to triple-ring PAHs was investigated using a flow tube reactor. The gaseous products from the pyrolysis of benzene were analyzed by using GC-MS in the temperature range of 850 - 1277 K and pressure range of 50 - 760 mmHg. We found that PAH products formed at temperatures greater than 1050 K, and the formation process was pressure dependent.

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.

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.

Autoignition in the homogeneous charge compression ignition (HCCI) process typically exhibits heat release in two stages called cool flame and thermal flame. The mechanisms governing these two stages were investigated using a DME-fueled HCCI engine and numerical simulations. Composition analysis after cool flame showed that the cool flame is explained by a chain reaction mechanism in which the chain terminator is the intermediate species formed in cool flame. In the case of thermal flame, although the chain reaction mechanism is complex, the behavior is clearly described by thermal explosion theory in which the rate-determining reaction is H2O2 decomposition.

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.

We developed a high-pressure fuel pump for a direct injection gasoline engine and used a hydraulic simulator to design it. A single plunger design is the major trend for high-pressure fuel pumps because of its simple structure and small size. However, the single plunger causes large pressure pulsation and an unstable flow rate, especially at high engine speed. Therefore, a fuel-pipe layout that inhibits the pressure pulsation and a flow-rate control that stabilizes the flow are the most important challenges in pump design. Our newly developed hydraulic simulator can evaluate the dynamic characteristics of a total fuel supply system, which consists of pump, pipe, injector, and control logic. Using this simulator, we have improved fuel flow by optimizing the outlet check valve lift and the cam profile, and we reduced pressure pulsation by optimizing the layout of fuel pipes. Our simulation results agreed well with our experimental results.

Applicability of detailed chemical kinetic models to HCCI runs in terms of ignition timings and intermediate species composition has been investigated. An existed n-heptane model and its expansion to n-decane established in this study were particularly concerned. Exhaust gas analysis showing transient composition after cool flames indicated that the unmodified n-decane model overestimates fractions of various grade of aldehydes, whereas it represents experimental ignition timings. The aldehyde yield was found to be sensitive to reactions of aldehyde with OH rather than aldehyde formation reactions. Reactions of QOOH decomposition forming HO2 were also suggested as a candidate to be revised for the model improvement on ignition delays.

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.

In the small engine market, it is essential that engines should be competitive in price, fuel-efficient, reliable and durable. This is nowhere truer than for units in the horsepower range below 100kW. With these goals in mind, recent trends in engine development have focussed on increased power with a smaller swept volume at high speeds. The development of this new series was vitalized by intense competition in the industrial engine market, especially from automakers, and a trend which is particularly noticeable in the United States towards the replacement of gasoline drive with diesel in the range below 50kW. One result is that engine design and manufacture have become increasingly complex and demanding. The TN series is designed to meet these new standards and ride the growing trend towards dieselization. It replaces the current TL and THL engine series.