| As the primary standard device,the pVTt method gas flow standard device is widely used,but its verification method needs to undergo a gas flow stabilization process after gas pumping and aeration,so that the verification efficiency is relatively low.Based on the previous studies,this paper proposes a thermal active compensation method to improve the flow field stabilization speed through active heating or cooling of the charge and discharge process.The main research contents are as follows:(1)The principle of pVTt gas flow standard device is summarized systematically.The research status of pVTt method temperature measurement program at home and abroad is introduced.Finally,the important role of temperature field research in the whole verification process is discussed,and the significance of the research is explained.(2)According to the design specification,the overall scheme design of the pVTt thermal compensation device is carried out by a combination of theoretical analysis,numerical simulation and experimental exploration.The mathematical model of temperature field is established,including two stages of air intake process and temperature stabilization process,which provides theoretical basis for subsequent simulation and experiment.(3)The hardware design and software debugging of the thermal active compensation system of pVTt gas flow standard device are carried out.The whole system is divided into three modules: nozzle verification,thermal active compensation and data acquisition.(4)The ANSYS software was used to simulate the air intake process and temperature stabilization process in the standard container.On the basis of verifying the grid independence,two models of active compensation module and no active compensation module were established to study the temperature inside the container.The specific changes of the field show that adding the active compensation module for dynamic compensation will shorten the time required for temperature field stabilization and greatly improve the verification efficiency.(5)Finally,according to the verification procedure,the whole system was tested for air tightness,volume calibration experiment,etc.The results show that the whole device is airtight,and under the action of the active compensation module,the standard container stabilization time is shortened from ten minutes to within one minute,the verification efficiency was significantly improved,which was consistent with the simulation results. |
