2001 Fiscal Year Final Research Report Summary
C0_2 selective EGR for Emission Reduction of Cogeneration Engine System
| Project/Area Number |
12650206
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Thermal engineering
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| Research Institution | The University of Tokushima |
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Principal Investigator |
MIWA Kei The University of Tokushima, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (00026147)
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| Co-Investigator(Kenkyū-buntansha) |
MOHAMMADI Ali The University of Tokushima, Graduate School of Engineering, Assistant, 大学院・工学研究科, 助手 (40314885)
KIDOGUCHI Yoshiyuki The University of Tokushima, Faculty of Engineering, Lecturer, 工学部, 講師 (70294717)
HAYASHI Hiroshi The University of Tokushima, Faculty of Engineering, Professor, 工学部, 教授 (00035627)
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| Project Period (FY) |
2000 – 2001
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| Keywords | Diesel Combustion / Emission / CO2 / NOx / Smoke / Exhaust Gas Recirculation / Hydrocarbons |
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| Research Abstract |
Cogeneration systems offer a high overall efficiency and are environmentally friendly. In small-scale domestic Cogeneration systems, diesel engines are usually employed which have high thermal efficiency and emit a low amount of CO_2. However, NOx and particulate matter (PM) emitted from employed diesel engines are still serious environmental problems. In diesel engines, NOx can be reduced by retarding fuel injection timing and exhaust gas recirculation EGR. However, these methods end with an increase of PM. Purpose of this study is to reduce both NOx and PM of diesel engines using a CO_2 selective EGR system. In this method, CO_2 gas emitted from a diesel engine is chemically absorbed by K_2CO_3 in a flow reactor and then CO_2 is extracted from the reactor by steam flashing. Finally, extracted highly pure CO_2 gas is introduced into the intake air of engine. Using this method one can obtained a considerable NOx reduction with a low amount PM. In this work, at first a small-scale flow
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reactor was used to examine the CO_2 absorption by K_2CO_3 on activated carbon (300g K_2CO_3/1000g Carbon). Reactor with a length of 300mm and an inner diameter of 20mm, which is heated, at constant temperature of 100℃. In order to simulate the diesel exhaust, mixture of CO_2 and nitrogen gas (CO_2 : 11.8 %) is humidified by a saturator and heated at 100℃. Then the gas is supplied through a heated line to the reactor. The concentration of the CO_2 at outlet of the reactor was measured to check the chemical absorption of CO_2 by K_2CO_3. Effect of reactor temperature, gas flow rate and moisture concentration on CO_2 absorption was examined. It was found that reactor temperature of 100℃ offers the highest CO_2 absorption while in the range this experiment effect of the gas flow rate was small. In CO_2 extraction experiment, the absorbed CO_2 gas was extracted by flashing the reactor content by a highly humidified nitrogen gas. It was observed that the steam flashing at a temperature of about 190℃ gives the highest CO_2 extraction and steam flushing with a high flow rate shorten the extraction period. Above experiment shows that mentioned technique has a great potential to obtain a highly pure CO_2 gas for selective EGR. In the last step of experiment, CO_2 selective EGR in a direct injection diesel engine was performed by adding pure CO_2 into the intake air of the engine. It was observed that only 3 % of CO_2 addition into the intake air could provides a considerable reduction of NOx and PM. Less
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