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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.
He Jia,Shao Xiaoqiang,Su Qin,Zhao Donglin,Feng Shaojie,오원춘 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.1
A series of novel cobalt ion-doped ZnCr2−xCoxO4 (x = 0, 0.1, 0.15, 0.2) spinel oxides were synthesized with the hydrothermal method. X-ray diffraction, scanning electron microscope, specific surface area, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption of oxygen, and other analytical techniques were used to characterize the structure, morphology, and catalytic performance of each sample. Experiment results showed that the doping of cobalt ion significantly promoted the phase crystallization of spinel oxide. Cobalt ion-doped ZnCr2−xCoxO4 (x = 0.1, 0.15, 0.2) nanoparticles with high specific surface area were synthesized at 773 K, with ZnCr2O4 forming a spinel phase at 1173 K. Catalytic experiments revealed that the catalytic activity of ZnCr2−xCoxO4 was effectively improved. Cobalt ion-doped ZnCr1.85Co0.15O4 catalyst catalyzed methane combustion reaction temperature at T90% (the temperature where 90% of methane was converted) of about 573 K, while the undoped ZnCr2O4 sample had the highest catalytic performance at T90% of about 773 K. The order of catalytic activity was: ZnCr1.85Co0.15O4 > ZnCr1.9Co0.1O4 > ZnCr1.8Co0.2O4 > ZnCr2O4. Results of catalytic experiments showed that the surface area of the catalyst increased after partial replacement of chromium ions by cobalt ions and that the increase in surface area of the catalyst provided more active sites, thus improving the reaction activity.