Study On Condensation Conditions Of Vacuum Suction Circuit In Pneumatic Negative Pressure System

With the wide application of vacuum attraction technology, the condensation problem in vacuum attraction circuits have become an urgent problem. Although compressed air in the pneumatic system will be conducted to remove water before use, there will still be a small amount of water vapor existing in the system. The water vapor in the compressed air will condense if the temperature is lower than the dew point temperature of the compressed air during the system operation. When the condensed water droplets are stayed in the system and accumulated gradually, the condensation will occur. The condensation in the vacuum attraction circuit will put a great impact on the lubrication, longevity and reliability of the system. In this paper, the theoretical analysis of condensation in vacuum attraction circuit of the pneumatic negative pressure system is conducted. Then the experimental programs are designed and the automated experimental devices of condensation in vacuum attraction circuit is built up. Thus a large number of vacuum attraction circuit condensation experiments are finished. The influence of experimental factors on the condensation of the system is achieved based on the analysis of the theoretical and experimental results. The identification methods and preventive measures of condensation in the pneumatic negative pressure system are first proposed.The main research work in this paper is as following:1. The mathematical model of deflation in the pipes of pneumatic negative pressure system is established. Then the flow field parameters are calculated and the changes of relative humidity are researched in the process of a single deflation.2. An automated experimental system has been developed to satisfy the experimental requirements. The parameters such as vacuum-relief air pressure, vacuum pressure and switching frequency can be adjusted by the system and the humidity generation circuit is built up to produce a constant humidity. A small humidity plug-collecting device is made to measure the dynamic accumulation process of humidity and the results are analyzed.3. The influence of experimental factors to the condensation in vacuum attraction circuit is achieved based on the analysis of the experimental results, including pipe length, dew point of the vacuum-relief air (relative humidity of the vacuum-relief air), pipe diameter, pressure difference (vacuum-relief air pressure and vacuum pressure), switching frequency and so on.4. Based on the analysis of conclusions of the theoretical and experimental data, the identification methods and preventive measures of condensation in vacuum attraction circuit of the pneumatic negative pressure system are first proposed.Based on the study of condensation in vacuum attraction circuit in different conditions, the influence of experimental factors to the condensation have been obtained. The identification methods and preventive measures of condensation in vacuum attraction circuit are proposed. This would provides a technical reference for research works and engineering applications of pneumatic negative pressure system.