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Analysis and Modeling of NOx Reduction Based on the Reactivity of Cu Active Sites and Brønsted Acid Sites in a Cu-Chabazite SCR Catalyst

Waseda Univ-Yoshihisa Tsukamoto, Takao Fukuma, Jin Kusaka
Published 2019-09-09 by SAE International in United States
The NOx-reducing activity of a Cu-chabazite selective catalytic reduction (SCR) catalyst was analyzed over a wide temperature range. The analysis was based on the ammonia SCR (NH3-SCR) mechanism and accounted for Cu redox chemistry and reactions at Brønsted acid sites. The reduction of NOx to N2 (De-NOx) at Cu sites was found to proceed via different paths at low and high temperatures. Consequently, the rate-limiting step of the SCR reaction at Cu sites varied with the temperature. The rate of NOx reduction at Cu sites below 200°C was determined by the rate of Cu oxidation. Conversely, the rate of NOx reduction above 300°C was determined by the rate of NH3 adsorption on Cu sites. Moreover, the redox state of the active Cu sites differed at low and high temperatures. To clarify the role of the chabazite Brønsted acid sites, experiments were also performed using a H-chabazite catalyst that lacks Cu sites. NOx reduction via the NO2-NH3 reaction was found to occur at Brønsted acid sites at high temperatures (up to 600°C). We also analyzed the…
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A Study on Combustion Characteristics of a High Compression Ratio SI Engine with High Pressure Gasoline Injection

Waseda Univ-Takashi Kaminaga, Kyohei Yamaguchi, Sok Ratnak, Jin Kusaka
Mazda Motor Corp-Takashi Youso, Tatsuya Fujikawa, Masahisa Yamakawa
Published 2019-09-09 by SAE International in United States
In order to improve thermal efficiency of spark ignition (SI) engines, an improved technology to avoid irregular combustion under high load conditions of high compression ratio SI engines is required. In this study, the authors focused on high pressure gasoline direct injection in a high compression ratio SI engine, which its rapid air-fuel mixture formation, turbulence, and flame speed, are enhanced by high-speed fuel spray jet. Effects of fuel injection pressure, injection and spark ignition timing on combustion characteristics were experimentally and numerically investigated. It was found that the heat release rate was drastically increased by raising the fuel injection pressure. The numerical simulation results show that the high pressure gasoline direct injection enhanced small-scale turbulent intensity and fuel evaporation, simultaneously. These two effects were considered as the main factors to increase the flame propagation speed, suggesting a new combustion concept different from conventional SI combustion controlled by in-cylinder bulk flow. This combustion method enables the delay of fuel injection and spark ignition timing up to near top dead center (TDC) which leads to avoid…
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A Numerical Study of the Effects of FAME Blends on Diesel Combustion and Emissions Characteristics Using a 3-D CFD Code Combined with Detailed Kinetics and Phenomenological Soot Formation Models

SAE International Journal of Fuels and Lubricants

Waseda Univ-XiaoDan Cui, Beini Zhou, Mitsuhiro Matsunaga, Yusuke Fujii, Jin Kusaka, Yasuhiro Daisho
  • Journal Article
  • 2013-01-2689
Published 2013-10-14 by SAE International in United States
The objective of the present research is to analyze the effects of using oxygenated fuels (FAMEs) on diesel engine combustion and emission (NOx and soot). We studied methyl oleate (MO), which is an oxygenated fuel representative of major constituents of many types of biodiesels. Engine tests and numerical simulations were performed for 100% MO (MO100), 40% MO blended with JIS#2 diesel (MO40) and JIS#2 diesel (D100). The effects of MO on diesel combustion and emission characteristics were studied under engine operating conditions typically encountered in passenger car diesel engines, focusing on important parameters such as pilot injection, injection pressure and exhaust gas recirculation (EGR) rate.We used a diesel engine complying with the EURO4 emissions regulation, having a displacement of 2.2 L for passenger car applications. In engine tests comparing MO with diesel fuel, no effect on engine combustion pressure was observed for all conditions tested. However, combustion was enhanced by using MO under low temperature and high EGR rate (high equivalence ratio) conditions. Using MO, soot emission was significantly reduced without a concomitant increase in…
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A Study on the Characteristics of Natural Gas Combustion at a High Compression Ratio by Using a Rapid Compression and Expansion Machine

Waseda Univ-Akira Kikusato, Hiroyuki Fukasawa, Kazutoshi Nomura, Jin Kusaka, Yasuhiro Daisho
Published 2012-09-10 by SAE International in United States
Natural gas is an attractive alternative fuel for internal combustion engines. Homogeneous charge compression ignition (HCCI) combustion is considered to be one of the most promising measures for increasing thermal efficiency and reducing emissions, but it is difficult to control and stabilize its ignition and combustion processes.This paper describes an experimental study of natural gas combustion utilizing two types of ignition assistance. Spark assistance, which is used for conventional spark ignition (SI) engines, and pilot diesel injection, hereinafter called diesel pilot, which generates multiple ignition points by using a small injection of diesel that accounts for 2% of the total heat release for the cycle. The performance of these two approaches was compared with respect to various combustion characteristics when burning homogeneous natural gas mixtures at a high compression ratio. A rapid compression and expansion machine (RCEM) was utilized to reproduce and visualize the inherent combustion processes. Inspection of combustion movies recorded using a high-speed video camera revealed that premixed flame is initiated at the spark plug or around the diesel spray, propagates and induces…
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Subscale Air Revitalization System by CO2 Reduction for Small Satellite Demonstration

Waseda Univ-Koushiro Usuku, Susumu Toda
JAXA Japan Aerospace Exploration Agency-Masato Sakurai, Shoichi Yoshihara, Naoko Nakayama, Mitsuo Oguchi, Mitsuru Ohnishi
Published 2009-07-12 by SAE International in United States
A regenerative Air Revitalization system has been developed by JAXA. Its major assemblies are a CO2 concentration assembly which contains membrane dryers to remove humidity and zeolite to remove CO2, a CO2 reduction assembly, and a water electrolysis assembly to which water is supplied in the vapor phase through molecule-size pores in a NAFION membrane rather than as liquid to solve the problem of gas-liquid separation in microgravity conditions. A small satellite mission using a subscale air revitalization system (for 1/10 person) is planned as an orbital demonstration of solving microgravity-related problems, interface problems between assembly, compaction problems and saving energy design. A small satellite is used because it has a greater chance of being selected for flight than ISS experiments, and it will be useful for mission assurance to perform small satellite experiments before an ISS manned mission.
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