Effect of ignition timing and hydrogen fraction on combustion and emission characteristics of natural gas direct-injection engine |
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Authors: | Jinhua Wang Zuohua Huang Bing Liu Ke Zeng Jinrong Yu and Deming Jiang |
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Affiliation: | (1) State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an, 710049, China |
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Abstract: | An experimental study on the combustion and emission characteristics of a direct-injection spark-ignited engine fueled with
natural gas/hydrogen blends under various ignition timings was conducted. The results show that ignition timing has a significant
influence on engine performance, combustion and emissions. The interval between the end of fuel injection and ignition timing
is a very important parameter for direct-injection natural gas engines. The turbulent flow in the combustion chamber generated
by the fuel jet remains high and relative strong mixture stratification is introduced when decreasing the angle interval between
the end of fuel injection and ignition timing giving fast burning rates and high thermal efficiencies. The maximum cylinder
gas pressure, maximum mean gas temperature, maximum rate of pressure rise and maximum heat release rate increase with the
advancing of ignition timing. However, these parameters do not vary much with hydrogen addition under specific ignition timing
indicating that a small hydrogen fraction addition of less than 20% in the present experiment has little influence on combustion
parameters under specific ignition timing. The exhaust HC emission decreases while the exhaust CO2 concentration increases with the advancing of ignition timing. In the lean combustion condition, the exhaust CO does not
vary much with ignition timing. At the same ignition timing, the exhaust HC decreases with hydrogen addition while the exhaust
CO and CO2 do not vary much with hydrogen addition. The exhaust NOx increases with the advancing of ignition timing and the behavior
tends to be more obvious at large ignition advance angle. The brake mean effective pressure and the effective thermal efficiency
of natural gas/hydrogen mixture combustion increase compared with those of natural gas combustion when the hydrogen fraction
is over 10%.
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Translated from Transactions of CSICE, 2006, 24(5): 394–401 译自:内燃机学报] |
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Keywords: | natural gas hydrogen ignition timing combustion emissions direct-injection |
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