Circular impinging jet, which is widely used in accelerated control cooling （ACC） equipment to accelerate the cooling of hot rolled plates, is subject to breakup, and may result in undesirable cooling effect. Theref...Circular impinging jet, which is widely used in accelerated control cooling （ACC） equipment to accelerate the cooling of hot rolled plates, is subject to breakup, and may result in undesirable cooling effect. Therefore, the jet breakup should be avoided as possible in industrial production. The objective of this study is to find the relation of the processing parameters of the ACC equipment versus the breakup length of jet with weaker turbulence. To obtain quantitative findings, not only relative experimental study but also numerical simulation was carded out. For a weaker turbulent water jet, the breakup length increases with the increase of jet diameter, as well as with the jet velocity; jet diameter has a significant effect on the breakup length for a certain flow rate when compared with jet velocity; finally a suggested correlation of the jet breakup length versus jet Weber number is presented in this study.展开更多
For the solutions of random variations of metal jet breakup and difficulties in controlling and predicting the process parameters （e.g. jet length） in micro droplet deposition manufacturing technique, experimental m...For the solutions of random variations of metal jet breakup and difficulties in controlling and predicting the process parameters （e.g. jet length） in micro droplet deposition manufacturing technique, experimental methods combining with theoretical analyses have been developed. The jet formation, jet length and their dominant factors （oxygen concentration and disturbance frequency, etc.） are discussed. The statistical law of jet length is found that the probability density function （PDF） of jet length is a log-normal distribution. The results show that the formation and size accuracy of metal jet breakup are improved by adjusting the gas pressure and optimizing the disturbance frequency. Under this circumstance, the jet length and morphological deviation can be minimized, which provides a stable droplet stream for the subsequent manufacturing process.展开更多
为验证某水电站工程生态泄水道的生态泄量是否满足要求,研究生态泄水道过流能力、沿程水流速度、压力分布、挑距等水力学特性,采用FLUENT软件、标准紊流模型对泄水道建立三维数值模型。采用VOF法捕捉自由水面、半隐式SIMPLE(Semi-Implic...为验证某水电站工程生态泄水道的生态泄量是否满足要求,研究生态泄水道过流能力、沿程水流速度、压力分布、挑距等水力学特性,采用FLUENT软件、标准紊流模型对泄水道建立三维数值模型。采用VOF法捕捉自由水面、半隐式SIMPLE(Semi-Implicit Method for Pressure-Linked Equations)算法求解速度与压力耦合方程组,将数值模拟结果与模型试验结果对比验证,验证泄水道孔口尺寸的合理性,结果可为体型设计提供依据。展开更多
Correlations for the extension of a water vapor jet injected in a liquid pool were historically proposed considering the mass flux (kg/m2/s) as a constant. The results were satisfactory, however adjusting the values b...Correlations for the extension of a water vapor jet injected in a liquid pool were historically proposed considering the mass flux (kg/m2/s) as a constant. The results were satisfactory, however adjusting the values by linear regression. Although, it presents the following drawbacks: 1) the formulation is only valid for the specific range of data for what it was created;2) it does not allow the analytical evaluation of the heat transfer coefficient from the extension equation. This paper proposes a new formulation for the calculation of the mass flux, in such a way to remove both of these drawbacks.展开更多
文摘Circular impinging jet, which is widely used in accelerated control cooling （ACC） equipment to accelerate the cooling of hot rolled plates, is subject to breakup, and may result in undesirable cooling effect. Therefore, the jet breakup should be avoided as possible in industrial production. The objective of this study is to find the relation of the processing parameters of the ACC equipment versus the breakup length of jet with weaker turbulence. To obtain quantitative findings, not only relative experimental study but also numerical simulation was carded out. For a weaker turbulent water jet, the breakup length increases with the increase of jet diameter, as well as with the jet velocity; jet diameter has a significant effect on the breakup length for a certain flow rate when compared with jet velocity; finally a suggested correlation of the jet breakup length versus jet Weber number is presented in this study.
基金National High-tech Research and Development Program of China (2008AA03A238)Fund for the Doctoral Program of Higher Education of China (20070699076)Foundation for the Author of National Excellent Doctoral Dissertation of China (2007B3)
文摘For the solutions of random variations of metal jet breakup and difficulties in controlling and predicting the process parameters （e.g. jet length） in micro droplet deposition manufacturing technique, experimental methods combining with theoretical analyses have been developed. The jet formation, jet length and their dominant factors （oxygen concentration and disturbance frequency, etc.） are discussed. The statistical law of jet length is found that the probability density function （PDF） of jet length is a log-normal distribution. The results show that the formation and size accuracy of metal jet breakup are improved by adjusting the gas pressure and optimizing the disturbance frequency. Under this circumstance, the jet length and morphological deviation can be minimized, which provides a stable droplet stream for the subsequent manufacturing process.
文摘为验证某水电站工程生态泄水道的生态泄量是否满足要求,研究生态泄水道过流能力、沿程水流速度、压力分布、挑距等水力学特性,采用FLUENT软件、标准紊流模型对泄水道建立三维数值模型。采用VOF法捕捉自由水面、半隐式SIMPLE(Semi-Implicit Method for Pressure-Linked Equations)算法求解速度与压力耦合方程组,将数值模拟结果与模型试验结果对比验证,验证泄水道孔口尺寸的合理性,结果可为体型设计提供依据。
文摘Correlations for the extension of a water vapor jet injected in a liquid pool were historically proposed considering the mass flux (kg/m2/s) as a constant. The results were satisfactory, however adjusting the values by linear regression. Although, it presents the following drawbacks: 1) the formulation is only valid for the specific range of data for what it was created;2) it does not allow the analytical evaluation of the heat transfer coefficient from the extension equation. This paper proposes a new formulation for the calculation of the mass flux, in such a way to remove both of these drawbacks.
