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Eliphas Wagner Simões, Rogerio Furlan, Roberto Eduardo Bruzetti Leminski, Mário Ricardo Gongora-Rubio, Marcos Tadeu Pereira, Nilton Itiro Morimoto
Micro fluidic Oscillator for Gas Flow Control and Measurement

Micro fluidic oscillators were obtained from wall attachment micro fluidic amplifiers using a feedback loop from the outputs to the control inputs. These devices can be used as actuators, as mixers, and also as flow meters, when the oscillation frequency is proportional to the volumetric flow in subsonic and moderately compressible conditions. The devices were then made in a SU-8 based epoxy photo resist using photolithography ultraviolet process. The article shows the results obtained in the experimental tests of the devices with gases (nitrogen, argon, and carbon dioxide). The dimensions are of the order of 280 µm. The typical variation of the frequency with volumetric flow presents a range close to thousands of Hz. The oscillation frequencies were obtained using hot wire filaments (in this case with 12 µm of diameter). The experimental results indicated which operation of the micro fluidic oscillator were direct function of the length of feedback loop and the velocity inside of the interaction region.

Jiun-Jih J. Miau, Chen-Fan Yeh, Chih-Chung Hu, Jung-Hua Chou
On Measurement Uncertainty of a Vortex Flowmeter

Measurement uncertainty of a T-shaped flowmeter was examined with a gas flow calibration facility, for Reynolds numbers, Red, in a range of 2.56 × 104 - 1.56 × 105. The total uncertainty interval of the Strouhal values deduced from a Fourier spectral analysis was ±0.745 %, and the linearity of the data was ±1.78 %. Meanwhile, a scheme based on pulses counting in reference to the analog signals measured gave the total uncertainty interval of the meter factor as ±0.568 %, with the linearity ±1.89 %.

Ernst von Lavante, Udo Banaszak
Effects of Shape Change due to Wear on the Accuracy of Vortex-shedding Flow Meters

In the present investigation, the problem of accurate determination of volumetric flows by means of the so-called vortex-shedding flowmeter in the case of shape changes from the original specifications due to wear was studied. To this end, the flow about the bluff body used in the presently studied vortex-shedding flow meter was numerically simulated using a solver of the unsteady, compressible Navier-Stokes equations in two and three dimensions. The computations were carried out for several Reynolds numbers using modified geometry in which rounded edges representing wear were introduced. The results were compared, where possible, with experimental data obtained by the manufacturer. The effects of turbulence were modeled by using the realizable k-e turbulence model. The resulting flow fields were analyzed using various methods, including visualization, evaluation of several of their global features and DFT of properly chosen variables.

Oliver Ricken, Volker Hans
Influence of the Variation of the Angle of Incidence in Vortex-shedding Metering

In vortex-shedding metering not only the shape of a bluff body is important but also the angle of incidence of the bluff body plays a major role in connection with production tolerances and unsymmetrical inflow. In the present investigation the influence of different angles of incidence of bluff bodies on the measured vortex frequency and the flow around the bluff body was studied by using ultrasonic barriers and rectangular and triangular shapes with 1:1 ratio of width to length for the bluff body. It became apparent that the vortices separate at different edges by inclination of the bluff body. The results were ensured by numerical simulations.

Yaoying Lin, Volker Hans
Influence of Inclination of Bluff Body in Flowmeters

This paper studies a factor which might influence the Strouhal number, that is, the inclination of the bluff body. The inclination of the bluff body happens in flow industry when the bluff body is inclined relative to its pipe parallel axis. Triangular bluff bodies are thoroughly discussed in this paper. Normally, the flat side is facing the inflow which is called conventional setup. It is turned around with 180 degrees facing the sharp side to the inflow, which is called unconventional setup in this paper. The inclination of bluff body has different influences in each setup. This paper shows that the flowmeter with bluff body in conventional setup makes lower Strouhal number but has more robustness to the inclination. On the contrary, it makes higher Strouhal number but less robustness. With fixed width, the different length of the triangular bluff body also causes influence to the Strouhal. In addition, the inclination of a rectangular plate bluff body is studied.

Wen Hanhang
The Research and Application of Critical-Flow-Subsonic Venturi Nozzle (The Extended Application of the ISO 9300 Critical Flow Venturi Nozzle)

The ISO 9300 Critical Flow Venturi Nozzle can be operated properly only in critical flow. If critical flow is not obtained, either a wrong measurement results, or the measurement is stopped if U > Ukp is confirmed. In addition, the measuring range of the Venturi nozzle is limited by the working pressure of the air source, therefore, the range of the measurement is small.
Per the ISO 9300 standard, the critical flow Venturi nozzle is transformed into a critical-flow-subsonic Venturi nozzle with function of taking pressure on the throat. A high accurate differential pressure convertor and the corresponding software are introduced, the multi-measuring range intelligent flowmeter with the function of determination of critical pressure ratio is constituted. During the measurement, the flow state is judged automatically. If U ≤ Ukp,the flow is critical. The calculation of the flow volume and the accuracy of measurement are completely same as the ISO 9300 critical flow Venturi nozzle type. If U > Ukp, the flow is subsonic. The pressure converter engaged in the calculation of flow volume, and a high accuracy of measurement is ensured.

Lei Lin, Li Ning, Wang Hou-Jun
Theory Conversion Method and Uncertainty Analysis for Critical Flow Coefficient of Venturi Nozzle

Without actual flow standard equipment of certain type of flow media or on the occasion of requiring no high measuring accuracy, critical flow coefficient of Venturi nozzle may be disposed by other methods instead of being actual flow calibrated through this flow media. The flow coefficient calibrated by other media, being enough analyzed and computed can be directly applied to a flow measurement of the other media. This article mainly researches on conversion method and analysis and computation of uncertainty of critical flow coefficient when Venturin nozzle works in critical flow state. In this article, on the premise of ensuring enough accuracy, the theory method of conversion between air and the natural gas, aiming at the flow coefficient of critical flow Venturin nozzle, is practical and feasible by experiments, furthermore this method may be popularized to other flow media on some conditions.

E. von Lavante, B. Mickan, R. Kramer
Numerical Investigation of Transitional Effects in Critical Venturi Nozzles

Several Venturi nozzles, operating at critical conditions and shaped according to the recommendations of the ISO Standard 9300 were selected for the present study. The flow in the nozzles was investigated numerically for a range of Reynolds numbers. The present results were compared with experimental data where available. The unsteady compressible viscous flow in the nozzles was simulated using the Navier-Stokes solver ACHIEVE, developed by the first author. Several models for predicting the laminar-turbulent transition were tested. Significant phenomena associated with the transition were observed, having an influence on the discharge coefficient CD.

Jae-Hyung Kim, Heuy-Dong Kim, Kyung-Am Park
Computational / Experimental Study of a Variable Critical Nozzle Flow

Recently, critical nozzles have been extensively utilized to measure the mass flow rate in a variety of industrial applications. For the measurement of the mass flow rates at a wide range of operation conditions, the critical nozzle is required to be designed with different diameters. The objective of the present study is to investigate the effectiveness of a variable critical nozzle. A rod with a small diameter is inserted into the critical nozzle to change the effective cross-sectional area of the critical nozzle. Experimental work is performed to measure the mass flow rate of the critical nozzle with rod. Computational work is carried out using the 2-dimensional, axisymmetric compressible Navier-Stokes equations which are discretized using a fully implicit finite volume method. The diameter of the rod is varied to obtain different mass flow rates through the variable critical nozzle. Computational results predict well the measured mass flow rates. The boundary layer displacement and momentum thickness at the throat of the critical nozzle are given as a function of Reynolds number. The discharge coefficient of the critical nozzle is given as an empirical equation.

Bodo Mickan, Rainer Kramer, Petra Kiesewetter, Dietrich Dopheide
Determination of Discharge Coefficients of Sonic Nozzles Obtaining Low Uncertainty without Knowledge of Throat Diameter

The paper presents a new approach for the determination of discharge coefficients of sonic nozzles. Innovating the conventional way, where the knowledge of throat diameter is always necessary, the new approach utilises a special mathematical characteristic of the equation cD = a +b·Re-0.5 to figure out a relationship of the parameter b as a function of the parameter a and to define a new parameter β with b =f(a,β).
It is shown in the paper by theory as well as by experimental results, that the parameter β can be determined only from measurements of flow rate and gas parameters without any knowledge about throat diameter.
With parameter a as a parameter which is very well known with low uncertainty from past research and theoretical studies, the discharge coefficient cD = a +b·Re-0.5 = a + f(a, β)·Re-0.5 can be determined now also for very small nozzles down to a Reynolds number Re = 1000 (throat diameter roughly 0.1 mm) with a very low uncertainty.
Additional to this, it is shown based on measurements of more than 300 nozzles, that the new parameter β is related to the inner geometry of the nozzle and a sensitive indicator of the quality of manufacturing and/or the measurements.

Page 161 of 977 Results 1601 - 1610 of 9762