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( Genmiao Guo ),( Zhixia He ),( Zhou Chen ),( Shenxin Sun ),( Zhengyang Zhang ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-
Flow inside nozzles and atomization dynamics in vicinity of the nozzle were crucial to diesel spray and combustion. And the tapered nozzle have attracted the researchers’ attention in recent years because of the better flow characteristics without the geometry induced cavitation. This paper presented the experimental and numerical analysis of string cavitation and near - nozzle spray dynamics. The string cavitation flow transient characteristics inside the tapered nozzle with the movement of needle were obtained based on the high speed digital microscopic imaging technique. Simultaneously, the formation and compression of initial air bubbles at the SOI (Start-of-Injection), and the air suction after the EOI (End-of-Injection) were captured clearly. The study indicates that the string cavitation was the direct cause of the spray instability. The various spray structures were observed at different injection pressures and different injection cycles under the same injection pressure. They might contain a clear single mushroom, tail region and intact liquid column, or had a tail in front of the mushroom. Occasionally, it presented as a double-mushroom shape, or did not include a clear mushroom. The difference of spray patterns may be due to the residual air bubbles surviving from the last injection or sucking into the nozzle during the needle opening. In order to explain the various spray patterns, effects of air bubbles distribution on initial spray patterns at the start stages of injections were investigated in a single-hole injector with a combination of the LES (Large Eddy Simulation) method and VOF (Volume of Fluid) model. The study confirmed that various spray patterns were affected by the injection pressure and initial air bubbles.
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( Zhaomin Hu ),( Yang Lan ),( Zhixia Zhang ),( Xingjuan Cai ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.2
Nowadays, recommendation systems (RSs) are applied to all aspects of online life. In order to overcome the problem that individuals who do not meet the constraints need to be regenerated when the many-objective evolutionary algorithm (MaOEA) solves the hybrid recommendation model, this paper proposes a many-objective particle swarm optimization algorithm based on multiple criteria (MaPSO-MC). A generation-based fitness evaluation strategy with diversity enhancement (GBFE-DE) and ISDE+ are coupled to comprehensively evaluate individual performance. At the same time, according to the characteristics of the model, the regional optimization has an impact on the individual update, and a many-objective evolutionary strategy based on bacterial foraging (MaBF) is used to improve the algorithm search speed. Experimental results prove that this algorithm has excellent convergence and diversity, and can produce accurate, diverse, novel and high coverage recommendations when solving recommendation models.
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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.
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