Research On Air-leakage Test Mechanism And Application About External Direct-pressure

An important process to ensure products' quality and safety is seal ability testing for products with a closed volume.In industrial,the method of testing product sealing is traditional water detection,while this method is gradually replaced by pneumatic detection method because of its low efficiency.Pneumatic detection method includes direct pressure and differential pressure airtight detection.Differential pressure method,based on the standard container,can reduce the influence of temperature and other factors,and it has high detection precision.However,high cost and complicated structure make this method is not perfect.Meanwhile,direct pressure method has the advantages of low cost and simple structure.In general,these two methods are used to detect the internal pressure(differential pressure)of the tested parts to calculate the leakage flow.For many closed products,it is difficult to achieve the detection of its internal pressure and it is not easy to achieve rapid product of leak detection.Based on this point,this paper presents a method of external direct pressure air leakage detecting.At the same time,based on the simulation analysis,a set of direct pressure testing equipment for the camera is developed and the experimental research is carried out.The main work is listed as follows:(1)Combined with the detection object and parameter requirements,a method of external direct pressure air leakage detecting method with buffer vessel is proposed,and its basic principle is expounded.According to the theory of gas thermodynamics,the relevant mathematical model of the detection process is established.(2)The simulation model of inflating process and two kinds of small hole leakage process was established by MATLAB / Simulink.Based on the analysis of the simulation results,the derivation of the calculation formula of the leakage rate of the external direct pressure is completed,and the main factors influencing the detection accuracy and efficiency are summarized.(3)Based on the theoretical and simulation results,the overall scheme of the system is designed,and the mechanical structure of the electronic control system and the device are designed accordingly.Based on the analysis of the air tightness detection process and the data processing method,the PLC program of lower computer,the HMI human interaction interface and the LabVIEW experimental system software were developed to achieve the automatic detection of the camera leakage rate.(4)The experimental researches are carried out about the changes of the total time of the inflation equilibrium,the change trend of the pressure difference in the testing process and the change of the leakage rate under different conditions.Without affecting the detection accuracy of the case,the parameters of the various stages of time settings are optimized,which improve the detection period.Through the test of the leakage camera,the experimental results show that the scheme is feasible,the error range is less than 5%,and the system detection period is less than 40 s.