Jeerasak Pitakarnnop, Rugkanawan Wongpithayadisai, Sutham Masri
SLIP-FLOW IN SONIC NOZZLES FOR FLOW RATE MEASUREMENTS

Sonic nozzles are wildly employed as a flow standard owing to their advantages in mechanical simplicity and long-term stability. The flow behaviours through the nozzles in normal conditions are well understood. However, in the applications where the size and the operating pressure are very small, the continuum assumption begins to break. Slip-flow, which is beyond the scope of ISO9300, becomes dominant. The scope of this study is to validate the method used to predict the effects in the nozzle.

Zhang Xiaozhong, Meng Fanqin, Song Shengkui, Wang Jiehui
A METHOD OF LIGHT FUEL MASS FLOW MEASUREMENT BY ULTRASONIC FLOWMETER

The mass flow measurement is generally necessary in light fuel oil delivery, but measurement value of the ultrasonic flow meter is volume flow rate, it cannot meet the requirement of mass flow measurement. In this paper, relationship between the light fuel ultrasonic velocity, fuel density and temperature is analyzed through a large number of experimental data, the neural network model of different light fuel density and temperature and its ultrasonic propagation velocity is found. By use of this network model, a method of mass flow measurement by a ultrasonic flow meter has been given. Compared with the density compensation method,this method do not need to enter the fuel standard density, and can further improve the light liquid fuel mass measurement accuracy,density error is less than 0.23%, error of mass flow is less than 0.35%.

Dennis W. K. Lee, Aaron Y. K. Yan, Henry K. L. Chiu, Raymond W. M. Leung
CALIBRATION OF GAS FLOW RANGING 1 TO 45 SLM AT THE STANDARDS AND CALIBRATION LABORATORY

This paper demonstrates different configurations of the SCL’s reference flow standard used in calibrating a mass flow controller at various line pressures, and elaborates on methods to improve the calibration efficiency and accuracy by using a back pressure regulator. This paper also studies the sensitivity of the reference flow standard to various line pressures. It is revealed that the deviation of relative reading errors is less than the uncertainties of the reference flow standard.

Zdeněk Krajíček, Martin Vičar, Dominik Pražák, Jiří Tesař, Tomáš Hajduk, Ladislav Peksa, Tomáš Gronych, Martin Jeřáb
EXPERIENCE WITH GRAVIMETRIC FLOW STANDARD (GFS) IN VACUUM AND HERMETIC MODE

The Czech national standard of low gas flow is based on a gravimetric flow standard (GFS) principle. It means it defines the flow as the mass loss of gas from a pressure bottle which is continuously weighed. This weighing is performed in an ambient atmosphere which causes that the main source of uncertainty results from the buoyancy correction. This buoyancy correction is complicated by the instabilities of the atmospheric environment and by the fact that volume of the weighed pressure bottle is dependent both on temperature and internal pressure. By modifying the experimental set-up of the GFS utilizing weighing in vacuum, it is possible to suppress the problematic buoyancy effects and moreover to eliminate other impractical side effects such as water vapour condensation on the pressure bottle due to cooling below dew point for the higher flow rates. This presentation describes the practical problems of the vacuum modification of the GFS together with the uncertainty analysis of the modified experimental set-up and the measurement results. The hermetic mode and its main applicability is also introduced.

Denis F. Hinz
REPEATABILITY OF LASER-DOPPLER VELOCIMETRY EXPERIMENTS FOR INDUSTRIAL PIPE-FLOW ANALYSIS

We study the repeatability of laser-Doppler velocimetry experiments for pipe-flow analysis. For single-point velocity measurements, we find repeatability standard deviations of approximately 0.5 % in the core region whereas measurements close to the wall are de-facto unrepeatable. We discuss how repeatability data may be used to verify uncertainty budgets and how it could be included in revised uncertainty budgets in view of established guidelines such as GUM and ISO 21748.