2008 Volume 2008 Issue 7-2 Pages 509-514
The common ways used to find leak include traditional bubbling test, ultrasonic positioning and helium mass-spectrometer detection, etc. However, each of them has deficiencies of varying degrees, especially low-efficiency in bubbling and mass spectrometry means and poor anti-jamming capability in ultrasonic means. In order to search a better approach to do this job, a new method is introduced in this paper, which is based on infrared thermography. In the experiment, test vessel is firstly aerated with absolute pressure of 0.6-0.7 Mpa and then the temperature field surround the vessel is monitored and acquired by an IR camera. On account of leakiness, compressed air expanses from the leak hole to ambient and heat-absorption effect has taken place around it on the basis of Joule-Thomson Effect, so the temperature difference between the leak area and normal area will be reflected in the thermal images. Moreover, Freon cooler is also set in the pneumatic circuit for the sake of enhancing the phenomenon. During the test, several frames of thermal images in time sequence are transferred to the computer for pre-processing and fusion operating by the use of local entropy difference algorithm. From results, it is shown that the method achieves a good resolution and sensitivity in the application of air-leakage detection and localization. Some modeling and simulating work by finite element analysis is also carried out in this paper.
