共查询到5条相似文献,搜索用时 0 毫秒
1.
U. B. Azimov K. S. Kim D. S. Jeong Y. G. Lee 《International Journal of Automotive Technology》2009,10(3):265-276
The concept of Low Temperature Combustion (LTC) has been advancing rapidly because it may reduce emissions of NOx and soot
simultaneously. Various LTC regimes that yield specific emissions have been investigated by a great number of experiments.
To accelerate the evaluation of the spray combustion characteristics of LTC, to identify the soot formation threshold in LTC,
and to implement the LTC concept in real diesel engines, LTC is modeled and simulated. However, since the physics of LTC is
rather complex, it has been a challenge to precisely compute LTC regimes by applying the available diesel combustion models
and considering all spatial and temporal characteristics as well as local properties of LTC. In this paper, LTC regimes in
a constant-volume chamber with n-Heptane fuel were simulated using the ECFM3Z model implemented in a commercial STAR-CD code.
The simulations were performed for different ambient gas O2 concentrations, ambient gas temperatures and injection pressures. The simulation results showed very good agreement with
available experimental data, including similar trends in autoignition and flame evolution. In the selected range of ambient
temperatures and O2 concentrations, soot and NOx emissions were simultaneously reduced. 相似文献
2.
3.
文中以一款增压直喷汽油机燃烧系统开发为例,从低速及高速两种工况,研究了气道及燃烧室形状、油束布置方案等因素对缸内混合气形成过程的影响。分析结果显示改变进气道及燃烧室屋脊形状、增加缸盖排气侧挤气面积以及调整油束喷射角度,可以提高缸内滚流运动强度、加强油气混合过程,从而有效改善了点火前缸内混合气的分布情况。研究了高转速下喷油时刻对混合气形成及燃油湿壁情况的影响,结果显示喷油起始角为390°CA时综合效果较好。采用较优方案组合进行的初步性能试验表明,外特性及部分负荷工况下的燃烧效率较高,动力性及经济性基本达到既定目标。 相似文献
4.
5.
If a vehicle that meets emission regulations operates sufficiently for a long time under low speed and low load conditions,
soot contained in the exhaust gas is accumulated on the inner surface of the exhaust system. This soot deposition problem
occurs frequently in all diesel cars. However, when a vehicle is placed under the conditions of sudden start and sudden acceleration
after city mode driving for a long time, the deposited soot is abruptly blown up with the soot produced during fuel combustion.
In the present study, the main cause of the abrupt outburst of deposited soot is investigated to overcome this adverse phenomenon.
First, we developed a method to quantify the amount of the exhausted soot particles (or the accumulated soot particles) by
measuring the opacity that represents the contamination level of the exhaust gas due to soot particles. Using this measuring
scheme for deposited soot, we found the critical conditions for engine speeds and load conditions at which soot particles
are emitted into the air without accumulation in the exhaust system using main muffler composed of three chambers. In order
to meet these critical conditions and thus to drastically reduce soot accumulation, the exhaust system using the main muffler
applied in this study must be designed to ensure that the flow velocity of the exhaust gas is higher than 62 m/s when the
back pressure at the exit of the turbocharger is under 0.08 bars. 相似文献