Non intrusive measurements of the acoustic pressure and velocity fluctuations of fluids flowing in pipes (original) (raw)
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Laser ultrasonic for measurements of velocity distribution in pipes
Journal of Applied Research and Technology
The present work describes the development of a photoacoustic flowmeter with probe-beam deflection. A pulsed laser beam produces an acoustic pulse, whose propagation is registered by its deflection effects on two cw probe beams. The acoustic propagations, along and against the flow, are monitored by two cw probe beams. In the interaction, the probe beam undergoes a transient deflection that is detected by a fast response photodiode. The velocity distribution data profile of a square pipe is obtained by means of the acoustic pulse arrival time measured through its cross section applying the cylindrical shockwave model deveolped by Vlasses. The profiles determined with this experimental technique are compared with two turbulent pipe flow models.
Acoustic flowmeter for the measurement of the mean flow velocity in pipes
The Journal of the Acoustical Society of America, 2001
This paper proposes a new technique for measuring the gas flow velocity averaged along the finite length of a pipe as well as over its cross-sectional area. Unlike the conventional gas flowmeters, the proposed technique exploits the one-dimensional plane waves that propagate uniformly across the pipe cross-sectional area. When a fluid flows along the pipe, the plane waves are superposed with the flow field such that the positive-going and negative-going plane wave components undergo the change of their wave numbers. Such wave number variation due to the mean flow velocity has provided a major motivation for developing a new way of measuring the mean flow velocity in the pipe, which is referred to as the acoustic flowmeter. To examine the feasibility of the developed flow velocity measurement method, including its theoretical backgrounds, experimental setups are illustrated in this paper. Detailed experimental data for the flow velocity range of 2-27 m/s reveal the linearity of the proposed acoustic flowmeter and its salient environmental robustness for the different acoustic pressure patterns in the pipe and, furthermore, for different velocity profiles over the pipe cross-section area.
A practical two-transducer ultrasonic flow meter
2008
Nowadays ultrasonic transducers are extensively used. Many industrial systems carry out their measurement process by taking the advantage of ultrasound waves. Sound of frequencies above audible range is called ultrasound, ultrasonic waves are classified under category of mechanical waves. Likewise all other mechanical waves, ultrasound needs material environment called medium to propagate through by moving the particles. Since the end of seventies, ultrasonic flow meters have been widely designed and applied in different industrial plans mainly related to fluid mechanics, chemistry, oil industry, etc. However, the initial motive of this thesis was to design a reliable mass flow meter applicable in controling the precise amount of energy transferred through gas pipe lines.
FUNDAMENTALS OF ULTRASONIC FLOW METERS
Ultrasonic contrapropagation methods have been used to measure the flow of natural gas since the 1970s, flare gases since the 1980s, and smokestack gases in cem (continuous emissions monitoring) since the 1990s. Since the early 2000s, ultrasonic clamp-on flow measurements, previously restricted mainly to liquids, were found effective in measuring in standard steel pipes, the flow of steam, natural gas and other gases and vapors, including air, as long as the flow velocity was not so high as to cause excessive beam drift or excessive turbulence (in other words, below about Mach 0.1), and provided the acoustic impedance of the gas was equivalent to air above about six bar and no important molecular absorption or scattering mechanisms were present. Although the flow of gases by ultrasonics has long been thought to be more difficult to measure than liquids, in fact the measurement is easier in two important respects. One is, for the contrapropagation method, the upstream -downstream time difference is generally much greater for gases, as a consequence of the much lower sound speeds in gases compared to liquids. The other significant factor that becomes important in mass flow metering (including scfm output) is the existence of theoretical and/or empirical relationships between ultrasonic propagation and density, where either of such relationships is easier to exploit for gases than for liquids. To provide an idea of the scope of applications addressable with ultrasonic technology that is commercially available now or likely to be available in the near future, this paper starts with an analysis from the point of view of acoustic impedance; considers designs as a function of the number of nozzles, from zero to a dozen; and lists factors conducive to high accuracy versus factors detrimental to high accuracy, i.e., conducive to uncertainty.
Sensors
Clamp-on ultrasonic flow meters (UFMs) are installed on the outside of the pipe wall. Typically, they consist of two single-element transducers mounted on angled wedges, which are acoustically coupled to the pipe wall. Before flow metering, the transducers are placed at the correct axial position by manually moving one transducer along the pipe wall until the maximum amplitude of the relevant acoustic pulse is obtained. This process is time-consuming and operator-dependent. Next to this, at least five parameters of the pipe and the liquid need to be provided manually to compute the flow speed. In this work, a method is proposed to obtain the five parameters of the pipe and the liquid required to compute the flow speed. The method consists of obtaining the optimal angles for different wave travel paths by varying the steering angle of the emitted acoustic beam systematically. Based on these optimal angles, a system of equations is built and solved to extract the desired parameters. T...
Experimental validation of an ultrasonic flowmeter for unsteady flows
Measurement Science and Technology
An ultrasonic flowmeter has been developed for further applications in cryogenic conditions and for measuring flow rate fluctuations in the range of 0 to 70 Hz. The prototype was installed in a flow test rig and was validated experimentally both in steady and unsteady conditions for water flows. A Coriolis flow meter was used for the calibration under steady state conditions, whereas in the unsteady case the validation was done simultaneously against two methods, the particle image velocimetry (PIV) and with pressure transducers flush installed on the wall of the pipe. The results show that the developed flowmeter and the proposed methodology can accurately measure the frequency and the amplitude of the unsteady fluctuations in the experimental range of 0-9 l/s of the mean main flow rate and 0-70 Hz of the imposed disturbances.
Ultrasonic Transit-time Flowmeters for Pipes: A Short Review
2017
Flow measurement is essential in many process monitoring, instrumentation and control applications in various fields of science and technology. The ultrasonic flowmeters are one of the most popularly used devices for flow measurements. From the inception of first of its kind, enormous advancement has been registered in terms of its wave reflection such as Doppler and transit-time, and mounting to get completely non-invasive and non-intrusive measurements. The ultrasonic flowmeters have been used for various types of flow including sediment laden, viscous and slurry flow in different pipe materials and pipe sizes under fullyand partially-filled conditions. The flowmeters have been developed using both active and passive principles, and have achieved high accuracy using multiple paths. The technological advancements especially in signal processing, electronic circuitry and availability of high precision transducers have given an edge to the researchers and developers of ultrasonic flo...
Design and Proof-of-Concept of a Matrix Transducer Array for Clamp-On Ultrasonic Flow Measurements
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Common clamp-on ultrasonic flow meters consist of two single-element transducers placed on the pipe wall. Flow speed is measured non-invasively, i.e. without interrupting the flow and without perforating the pipe wall, which also minimizes safety risks and avoids pressure drops inside the pipe. However, before metering, the transducers have to be carefully positioned along the pipe axis to correctly align the acoustic beams and obtain a well-calibrated flow meter. This process is done manually, is dependent on the properties of the pipe and the liquid, does not account for pipe imperfections, and becomes troublesome on pipelines with an intricate shape. Matrix transducer arrays are suitable to dynamically steer acoustic beams and realize self-alignment upon reception, without user input. In this work, the design of a broadband 37x17 matrix array (center frequency of 1 MHz) to perform clamp-on ultrasonic flow measurements over a wide range of liquids (c = 1000 − 2000 m/s, α ≤ 1 dB/MHz.cm) and pipe sizes is presented. Three critical aspects were assessed: efficiency, electronic beam steering, and wave mode conversion in the pipe wall. A prototype of a proof-of-concept flow meter consisting of two 36-element linear arrays (center frequency of 1.1 MHz) was fabricated and placed on a 1 mm-thick, 40 mm-inner diameter stainless steel pipe in a custom-made flow loop filled with water. At resonance, simulated and measured efficiencies in water of the linear arrays compared well: 0.88 kPa/V and 0.81 kPa/V, respectively. Mean flow measurements were achieved by electronic beam steering of the acoustic beams and using both compressional and shear waves generated in the pipe wall. Correlation coefficients of R 2 > 0.99 between measured and reference flow speeds were obtained, thus showing the operational concept of an array-based clamp-on ultrasonic flow meter. Index Terms beam steering, clamp-on flow meter, ultrasound flow meter, Guided waves, transducer design. This work is part of the research programme FLOW+, which is financed by the Dutch Technology Foundation STW (project 15031) and industrial partners Bronkhorst and KROHNE.