【作者】

Ryouta Minamino,Takao Kawabe

【摘要】

论文已在中国上海举行的第27届CIMAC大会上发表。论文的版权归CIMAC所有。Recent progress of fuel injection sys tem like a common rail system makes higher fuel injection pressure possible. With such a state-of-the-art higher injection pressure technology, diesel engine has been improved in all aspects of performance such as higher power density, lower fuel consumption, cleaner exhaust emissions, etc. Injection pressure of atest FiE systems for or passenge car reach around 3000 bar, but the most of such high injection pressure FlE systems are still under development. Their spray characteristics are investigated by using constant volume vessel, although condition are different from todays engines pressure and tem-perature. Soot and NOx emission from the engine uipped with such a higher injection pres till under investigation. Also, the optimal nozzle di mensions(i.e. number of holes and hole diameter)in accordance with higher injection pressure is still der investigation. In order to estimate emission perfor-nances, CFD coupled with many kinds of sub-models about spray combustion is applied as one of the avail-able method. However. a lot of constants in the simulation code have to be calibrated by use of spray measurement data. On the other hand, in this study, soot and NOx emission data from higher injection pressure is estimated by using engine equipped with practical fuel injection system. And optimized number of holes d hole-diameter for higher injection pressure is estimated. Increase in injection pressure causes the in rease in spray penetration and the promotion of at omization. As for the atomization, higher the injection ressure,less the improvement in atomization. Thus, in this study, spray penetration is focused on as a main parameter. According to the many empirical models of spray penetration, penetration is mainly determined by the difference between pressure of fuel injection and that of ambient gas. Emissions from higher injection pressure under the same excess air ratio is as sumed to be obtained by decreasing in-cylinder gas pressure instead of increasing injection pressure obtaining certain pressure difference that can keep same spray penetration. As for the calculation of spray penetration, this study applied Dents formula (1971)However. under the constant excess air ratio condition, decreasing in-cylinder gas pressure automatically yields to shorter injection duration. In this study, con injection pressure(as is shown in figure)is proposed to estimate how high injection pressure is required without decreasing in-cylinder gas pressure Converted injection pressure is calculated by Dent's ormula whose input is spray penetration experimen tally linked with engine out emission. In order to verify the concept of converted injection pressure, two different engines are applied in this study. At first, a natural aspirated engine with maximum 1600 bar common rail injection system is applied for building soot and NOx estimation models. In this engine test, wide range of emission data is obtained under the various conditions of excess air ratio and pressure difference between injection and in-cylinder gas. The result shows good relationship between converted injection pressure and measured soot. Using this re lationship, soot estimation model is built and proposed. In terms of NOx, it has a good relationship with injection duration. Then, in this study NO estimation model is also built base on injection duration. Next, a turbo charged engine with maximum 2000 bar injection common rail system is applied for evaluating this soot and NOx estimation model. It is found that relative changes of measured emissions follow estimated results. But there is a gap in their absolute value because of different combustion chamber shape and direction of nozzle hole axishus, it is found that proposed soot and NOx estimation model is only effective for their relative change against increase in injection pressure. At last, a trend of the optimal nozzle dimensions accomp

【会议名称】

第27届CIMAC会议

【会议地点】

上海

【下载次数】

1

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