| The pVTt Gas flow calibration facility which measures qualityindirectly is a a kind of original flow standard. Its mainly use is quantitytransmission for sonic nozzle. Our domestic pVTt facilities now existed arefew in number, and the efficiency is low in common. In response to thissituation, this paper presented a set of pVTt calibration device, it can realizerapid test of stand flow meter and sonic nozzle in the flow range of0.016~1024m~3/h.Firstly, designed scheme based on pVTt principle and technicalrequirements. Extended flow range by multi-standard containers installed inparallel. Buffer container makes a constant flow. Fan and duct was placed in26m3and6m3standard containers, and0.5m3,0.05m3and0.01m3containerswas soaked in constant temperature water channel. Secondly, the3-D spacemodal was developed, which covered fan model, water-bath structure andexchangeable test line for sonic nozzle and stand flow meter. The standcontainer was verified safe in excogitation. Then, simulation research ontemperature characterization in the collection tank of pVTt facility.3D modelwas built up in constant-temperature condition and nature environmentrespectively. Calculated the time-varying characteristic of temperature fieldby FLUENT from intake process to homogeneity period. Simulation Resultsshow that constant temperature measures can greatly shorten the waiting timein calibration process. Fan mixing made the temperature field steady-stateprocess of26m3container ahead of time by53.3%. And water-bath made theprocess of0.5m3container ahead of time by54%. Constant temperaturemeasures improved distribution of steady temperature field in tank. Steadytemperature field in water-bath condition distributed symmetrically with theaxis of the tank and the maximum temperature difference is0.01℃. Theserious temperature gradient existed in nature environment disappeared in fan-mode condition. Fourthly, temperature measuring point was decoratedcombined simulation data with isometric arithmetic. Finally, modified themass flow of pVTt device and analyzed its mass flow uncertainty.The massflow uncertainty of pVTt equipment is better than0.05%(k=2). |
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