Experimental And Simulated Study Of Flows For Parallel Flow Push-Pull Ventilation

Because parallel flow push-pull ventilation can control pollutant avoiding its transmission perpendicular to flow direction and good control effect, it has a good prospect in industrial pollution control field. However, the traditional researches of push-pull ventilation were mailly aimed at industrial slot push-pull ventilation. There are less study on the low velocity parallel flow push-pull ventilation. In especial, flow quality of parallel flow push-pull ventilation is scarcely any studied. If results based on the studies of high speed push-pull ventilation are directly used in low velocity parallel flow push-pull ventilation, a signicant bias can be generated. In order to solve these problems, some studies are carried out in the thesis.The research work can be divided into three parts: study on the axial velocity law of parallel flow push-pull ventilation; the study on the critical section of push-pull ventilation and its influencing factor; contrast study on pollution control of push-pull ventilation.Firstly, the axial velocity character of parallel flow push-pull ventilation is experimental studied. The researches show that the axial velocity of parallel flow push-pull ventilation follows the regular of exponential function. However the axial velocity of the traditional high speed push-pullventltion follows the regular of power function. By the contrast analysis between the power function of the traditional high speed push-pullventltion and the parallel flow push-pull ventilation experimental results, it indicates that there is prodigious error. The maximum error is 232%, and the minimum error is 70.7%. Secondly, The effects of space between air diffuser and exhaust inlet, size of air diffuser, size of exhaust inlet, velocity of jet and size baffle varied on the critical section are studied, which shows there is no critical section when the ratio of L and d₁ is less than 5. While the ratio of L and d₁ is more than 5, there is critical section in flow field. The location of critical section is mainly affected by space between air diffuser and exhaust inlet and size of exhaust inlet. According to the multiple linear regression analysis of simulated data, compulational formula of critical section is obtained.At last, the effect of parallel flow push-pull ventilation controlling pollution is studied when the same pollution source is located in the beginning section of jet, main part of jet and critical section. The results show that the effect of controlling pollution is the best when the pollution source lies in the beginning of jet. The control effect is the worst as the pollution source lies in the critical section. However, the air diffuser must not be arranged close to the pollution source because the pollution source will seriously influence flow field and lead to the push-pull ventilation control ability of pollution sharp declin. Finally, the paper gives the parameter of parallel flow push-pull ventilation device in order to providing the reference for actual project.In a word, the study of this paper promotes the development of parallel flow push-pull ventilation theory, and provides theoretical basis and guidance for the application of push-pull ventilation.