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Effects of Ambient Pressure and Injection Pressure on Diesel and Natural Gas Dual Fuel Spray
( Changsheng Shao ),( Qian Wang ),( Xiaoqiang Tan ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-
Dual fuel engines operating with direct injected natural gas (NG) and pilot diesel has been attracted by many engine researchers. With this system, small quantities of diesel auto-ignite, and NG is then ignited by the pilot diesel flame. This stratified combustion technique provides better fuel economy and more efficient combustion, maintaining the power output of an equivalently-sized conventional diesel engine. Comparatively lower emissions of NOx and particulate matter were also recorded. For the further understanding of dual fuel spray, effects of ambient pressure and injection pressure on diesel and NG dual fuel spray are investigated. Both NG and diesel are directly injected into an optical constant volume chamber by a dual fuel injector combiner for different injection pressure and ambient pressure. Schlieren photography is used to visualize the development of dual fuel spray. A Matlab processing script was developed to extract useful qualitative and quantitative information from each video frame. A comparison is made between NG jet characteristics in single fuel model (SFM) and dual fuel model (DFM). Results shows that in both SFM and DFM, the tip penetration decreased with the increase of the ambient pressure and the decrease of NG injection pressure, while the cone angle increased with the increase of the ambient pressure and the decrease of NG injection pressure. At different ambient pressure, the diesel spray has little influence on NG tip penetration, however it has impact on NG cone angle. The cone angle in DFM is higher than that in SFM. With the increase of ambient pressure, the diesel spray has less impact on NG cone angle. At different NG injection pressure, the diesel spray has influence on both NG tip penetration and cone angle. With the increase of NG injection pressure, diesel spray has less impact on NG cone angle.
Qian Wang,Changsheng Shao,Qing Liu,Zhourong Zhang,Zhixia He 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.4
Effects of Injection rates on combustion process and emissions of engines operating with directly injected natural gas and pilot diesel were numerically investigated. Injection rates of natural gas and diesel were investigated separately utilizing five types of injection rates. An impact factor was defined to present the effects of the initial and terminal injection rates of diesel and natural gas on the combustion and emissions more intuitionally. Based on the simulation results, cylinder pressure and temperature were more sensitive to terminal injection rates of pilot diesel than initial injection rates, and lower terminal injection rates of pilot diesel can achieve lower NO and Soot emission level. However, there is a trade-off between NO and Soot emissions affected by different natural gas injection rates. The impact factors of pilot diesel injection rates on pressure show a double-peak trend. However, the impact factors of natural gas injection rates on pressure show a single-peak trend.