滞止压力对音速喷嘴流出系数的影响研究

发布时间：2018-09-17 19:40

【摘要】：音速喷嘴因稳定性好,价格低等诸多优点,国内外普遍采用其作为标准表,对其它类型的气体流量计进行量值传递。流出系数是衡量音速喷嘴流量特性的重要指标,其值由滞止压力密切相关。本论文基于高压p VTt法气体流量标准装置,就滞止压力对音速喷嘴流出系数的影响开展了系统研究。2014年底,中国计量科学研究院建成一套高压气体流量标准装置,包括高压p VTt气体流量原级标准装置、高压音速喷嘴法气体流量次级标准装置及高压环道气体流量工作标准装置。作为本论文的实验平台的高压p VTt气体流量原级标准装置,其扩展不确定度为0.06%(k=2),通过对实验过程的严格控制,校准音速喷嘴流出系数的扩展不确定度为0.08%(k=2)。基于高压pVTt气体流量标准装置测试能力,选取了喉径(1.921~12.444)mm范围内,共计18支音速喷嘴,在滞止压力(0.1~2.5)MPa范围内,就滞止压力对流出系数的影响进行研究,得到以下三点结论:1)不同滞止压力下,同一块音速喷嘴的流出系数变化可达2.3%。流出系数随音速喷嘴边界层的转变呈现显著的规律:层流边界层,流出系数持续显著增加;过渡边界层内,流出系数随雷诺数增加产生一个减小的“跳跃”;湍流边界层内,流出系数缓慢增加;2)基于ISO9300-n模型和NMIJ-2013模型,本文提出NIM-2016模型,该模型对实验结果预测不确定度低于0.30%(k=2);以3支音速喷嘴作为传递标准,通过新建pVTt标准装置与原有p VTt装置及德国PTB的气体流量装置间的比对,比对结果的一致性对新建高压装置的测量能力和NIM-2016模型予以了验证。3)音速喷嘴边界层过渡的雷诺数与喉径直接相关,基于实验结果,本文提出音速喷嘴边界层过渡雷诺数与喉径间的经验公式,并通过已有他人实验结果对其进行了验证。
[Abstract]:Because of its good stability and low price, sonic nozzles are widely used as standard tables at home and abroad to transfer the values of other types of gas Flowmeters. The efflux coefficient is an important index to measure the flow characteristics of sonic nozzles, and its value is closely related to the stagnation pressure. Based on the gas flow standard device of high pressure p VTt method, this paper has carried out a systematic study on the effect of stagnation pressure on the efflux coefficient of sonic nozzles. At the end of 2014, a set of high pressure gas flow standard equipment was built in the China Institute of Metrology. It includes high pressure p VTt gas flow primary standard device, high pressure sonic nozzle method gas flow secondary standard device and high pressure loop gas flow working standard device. As the experimental platform of this paper, the expansion uncertainty of the high pressure p VTt gas flow level standard device is 0.06% (KG ~ 2). Through strict control of the experimental process, the extended uncertainty of calibrating the outflow coefficient of the sonic nozzle is 0.08% (KN ~ 2). Based on the test capability of high pressure pVTt gas flow standard device, 18 sonic nozzles with throat diameter (1.921 ~ 12.444) mm were selected to study the effect of stagnation pressure on efflux coefficient in the range of (0.1 ~ 2.5) MPa. The following three conclusions: 1) under different stagnation pressure, the efflux coefficient of the same sonic nozzle can reach 2.3. The efflux coefficient changes with the boundary layer of the sonic nozzle, such as laminar flow boundary layer, the outflow coefficient increases significantly, in the transition boundary layer, the outflow coefficient produces a small "jump" with the increase of Reynolds number, and in the turbulent boundary layer, the outflow coefficient increases with the increase of Reynolds number. On the basis of ISO9300-n model and NMIJ-2013 model, this paper presents a NIM-2016 model, which has less than 0.30% (km2) uncertainty in predicting experimental results, and takes three sonic nozzles as the transfer standard. By comparing the new pVTt standard device with the original p VTt device and the gas flow device of PTB in Germany, The consistency of the comparison results verifies that the Reynolds number of the boundary layer transition of the sonic nozzle is directly related to the throat diameter for the measurement capability and NIM-2016 model of the newly built high-pressure device, and based on the experimental results, the Reynolds number of the boundary layer of the sonic nozzle is directly related to the throat diameter. This paper presents an empirical formula between the Reynolds number of the boundary layer and the throat diameter of the sonic nozzle, which has been verified by other experimental results.
【学位授予单位】：河北大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH814

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