NISTの研究者は、音響波で気体を「くすぐり」、容器から出る速さを測定している。 NIST researchers “tickle” a gas with acoustic waves to measure how fast it exits a vessel.
2023-03-31 米国国立標準技術研究所(NIST)
この方法は、気体の平均温度を決定するために音波を使用し、容器の体積を確定するためにマイクロ波を使用することで、大型コンテナからの気体の流れや漏れを特によく測定できます。
この技術は、天然ガスパイプラインで使用されるガス流量計を正確に校正することができ、天然ガスの経済的価値が高いため、消費者と天然ガスプロバイダーの両方にとって重要な問題です。
＜関連情報＞
- https://www.nist.gov/news-events/news/2023/03/sounding-out-new-way-measure-gas-flow
- https://aip.scitation.org/doi/10.1063/5.0143819
音響共鳴トラッキングを用いたガス流の動的計測 Dynamic measurement of gas flow using acoustic resonance tracking
Jodie G. Pope, James W. Schmidt, and Keith A. Gillis
Review of Scientific Instruments Published:21 March 2023
DOI:https://doi.org/10.1063/5.0143819
ABSTRACT
The National Institute of Standards and Technology measured gas flows exiting large, unthermostated, gas-filled, pressure vessels by tracking the time-dependent pressure P(t) and resonance frequency fN(t) of an acoustic mode N of the gas remaining in each vessel. This is a proof-of-principle demonstration of a gas flow standard that uses P(t), fN(t), and known values of the gas’s speed of sound w(p,T) to determine a mode-weighted average temperature ⟨T⟩φ of the gas remaining in a pressure vessel while the vessel acts as a calibrated source of gas flow. To track fN(t) while flow work rapidly changed the gas’s temperature, we sustained the gas’s oscillations using positive feedback. Feedback oscillations tracked ⟨T⟩φ with a response time of order 1/fN. In contrast, driving the gas’s oscillations with an external frequency generator yielded much slower response times of order Q/fN. (For our pressure vessels, Q ∼ 103–104, where Q is the ratio of the energy stored to the energy lost in one cycle of oscillation.) We tracked fN(t) of radial modes in a spherical vessel (1.85 m3) and of longitudinal modes of a cylindrical vessel (0.3 m3) during gas flows ranging from 0.24 to 12.4 g/s to determine the mass flows with an uncertainty of 0.51 % (95 % confidence level). We discuss the challenges in tracking fN(t) and ways to reduce the uncertainties.
