Vortex ventilation,which utilizes vortex airflow to effectively transport pollutants over long distances,is a promising method for pollution control in large spatial structures.The performance of vortex ventilation he...Vortex ventilation,which utilizes vortex airflow to effectively transport pollutants over long distances,is a promising method for pollution control in large spatial structures.The performance of vortex ventilation heavily depends on the stable generation and maintenance of column vortex airflow,necessitating a comprehensive understanding of the interactions among supply airflow,exhaust airflow,and pollutant airflow.In this study,experimental method and transient computational fluid dynamics(CFD)method were employed to quantitatively analyze the influence of supply airflow characteristics and parameters on the formation of vortex airflow.It was found that impingements between supply jet streams significantly affect the generation of vortex ventilation.Based on variations in the flow shape of supply jet streams,the process of vortex airflow formation can be divided into three stages:initiation,oscillation,and stabilization.As the airflow rate increases,the impingement effect between the air jet streams makes the vortex unstable and the vortex intensity decreases.Optimization strategies were proposed to modify system geometry,including increasing the number of supply air inlets,adjusting the horizontal deflection angle of supply air,and enlarging the size of supply air inlets.Increasing the horizontal deflection angle of supply air was shown to minimize the negative pressure within the flow field to a minimum of−12 Pa and reduce the coefficient of variation to a minimum of 0.01,which proved most effective in enhancing vortex stability.展开更多
The flow field in the tip region of an axial ventilation fan is investigated with a particle image velocimeter （PIV） system at the design condition. Flow fields with three different tip clearances are surveyed on th...The flow field in the tip region of an axial ventilation fan is investigated with a particle image velocimeter （PIV） system at the design condition. Flow fields with three different tip clearances are surveyed on three different circumferential planes, respectively. The phase-locked average method is used to investigate the generation and the development of a tip leakage vortex. The result from PIV system is compared with that from a particle dynamics anemometer（PDA） system. Both data are in good agreement and the structure of the tip leakage vortex for the rotor is illustrated. The characteristic of a leakage vortex is described in both velocity vectors and vortical contours. The unsteadiness of the leakage vortex and the position of the vortex are surveyed in detail, which interprets the discrepancy between the numerical simulation and PDA experimental results to a certain extent. The center loci of tip leakage vortex at different times and the mean center loci of the leakage vortex are displayed particularly. Finally, the trajectories of the tip leakage vortex by the experimental measurement are compared with predictions from the existing models for high speed and high-pressure compressors and turbines when appropriately interpreted. A good agreement is obtained.展开更多
基金financially sponsored by the National Natural Science Foundation of China(No.52278128 and No.52378110).
文摘Vortex ventilation,which utilizes vortex airflow to effectively transport pollutants over long distances,is a promising method for pollution control in large spatial structures.The performance of vortex ventilation heavily depends on the stable generation and maintenance of column vortex airflow,necessitating a comprehensive understanding of the interactions among supply airflow,exhaust airflow,and pollutant airflow.In this study,experimental method and transient computational fluid dynamics(CFD)method were employed to quantitatively analyze the influence of supply airflow characteristics and parameters on the formation of vortex airflow.It was found that impingements between supply jet streams significantly affect the generation of vortex ventilation.Based on variations in the flow shape of supply jet streams,the process of vortex airflow formation can be divided into three stages:initiation,oscillation,and stabilization.As the airflow rate increases,the impingement effect between the air jet streams makes the vortex unstable and the vortex intensity decreases.Optimization strategies were proposed to modify system geometry,including increasing the number of supply air inlets,adjusting the horizontal deflection angle of supply air,and enlarging the size of supply air inlets.Increasing the horizontal deflection angle of supply air was shown to minimize the negative pressure within the flow field to a minimum of−12 Pa and reduce the coefficient of variation to a minimum of 0.01,which proved most effective in enhancing vortex stability.
基金This project is supported by National Natural Science Foundation of China (No.50406017).
文摘The flow field in the tip region of an axial ventilation fan is investigated with a particle image velocimeter （PIV） system at the design condition. Flow fields with three different tip clearances are surveyed on three different circumferential planes, respectively. The phase-locked average method is used to investigate the generation and the development of a tip leakage vortex. The result from PIV system is compared with that from a particle dynamics anemometer（PDA） system. Both data are in good agreement and the structure of the tip leakage vortex for the rotor is illustrated. The characteristic of a leakage vortex is described in both velocity vectors and vortical contours. The unsteadiness of the leakage vortex and the position of the vortex are surveyed in detail, which interprets the discrepancy between the numerical simulation and PDA experimental results to a certain extent. The center loci of tip leakage vortex at different times and the mean center loci of the leakage vortex are displayed particularly. Finally, the trajectories of the tip leakage vortex by the experimental measurement are compared with predictions from the existing models for high speed and high-pressure compressors and turbines when appropriately interpreted. A good agreement is obtained.
