| Co-Investigator(Kenkyū-buntansha) |
ISHIYAMA Takuji Kyoto Univ., Grad. School of Energy Science, Professor, エネルギー科学研究科, 教授 (30203037)
SHIOJI Masahiro Kyoto Univ., Grad. School of Energy Science, Professor, エネルギー科学研究科, 教授 (80135524)
KAWANABE Hiroshi Kyoto Univ., Grad. School of Energy Science, Assoc. Professor, エネルギー科学研究科, 助教授 (60273471)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2005: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2004: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Research Abstract |
Internal combustion engines fueled by gas-oil, gasoline and natural gas have been expected with the innovative combustion systems which can provide clean exhaust emissions and high thermal efficiency. Recently, Premixed Charge Compression Ignition (PCCI) engine as a power source for stationary applications is under extensive investigation due to its great potential for high thermal efficiency and very low NOx emissions. However, in natural-gas engines, methane has a high auto-ignition temperature, therefore stable ignition of natural gas requires high compression ratio, intake air heating, internal EGR and so forth. In addition to such measures for elevating the compression temperature and pressure, addition of butane, hydrogen, NOx and ozone into intake gas are proposed to lower the ignition temperature. Although these methods exhibit positive effects on the engine performance and emissions, stable operation of PCCI natural-gas engines would require combination of these techniques and
… More
this demands further investigation.
In this research, possibility of ignition and combustion promotion in PCCI natural gas engine with intake ozone addition was experimentally investigated using a single cylinder port mixing natural gas PCCI engine when intake gas temperature was kept constant at 180℃. In addition, detail chemical kinetics was utilized to clarify the reason for achieved improvements. Followings are main understanding obtained in this study.
1. The experimental results indicate that small amount intake addition of ozone greatly promotes the auto ignition of natural gas typically under the low equivalence ratios. And under low equivalence ratios, ignition improvement by ozone addition results in improvements in thermal efficiency and reduction of unburned emissions such as THC and CO. However, this trend saturates with increase in the ozone concentration. Minimum ozone concentration to reach the saturation level depends on the equivalence ratio. For high equivalence ratios, even small ozone addition gives knock like combustion and therefore limits the maximum engine output power. Combustion analysis shows that ozone addition advances the ignition timing, increase the maximum in-cylinder pressure and heat release rate and greatly lowers the combustion fluctuation. However, these trends saturates with the increase in the ozone concentration. Rough estimation indicates that under experimental condition, of this study, addition of 100ppm of ozone corresponds to 40℃ increase in the intake gas temperature. Production of this amount of ozone requires electric power of 120W.
2. Chemical kinetic calculation results show that decomposition of ozone at the early stages of the compression stroke forms active species, which are mainly responsible for improvement in the ignition and combustion of natural gas. Saturation trend in ignition improvements by increase in ozone concentration was also confirmed by the calculation. The results show that this trend is due to limited effects of HO_2 and H_2O_2 on the natural gas ignition. Less
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