Transit-time Ultrasonic Flowmeter Research Articles

Study of the influence of temperature on the measurement accuracy of transit-time ultrasonic flowmeters

PurposeThe purpose of this study is to deal largely with the influence of temperature variation on the measurement accuracy of transit-time ultrasonic flowmeter.Design/methodology/approachThe causes of measurement error due to temperature are qualitatively and quantitatively analyzed, and a mathematical model is established. The experimental data are processed and analyzed, and the temperature compensation coefficient of flow measurement is obtained.FindingsThe experimental results show that the flow measurement results by temperature compensation are helpful in improving the measurement accuracy of the ultrasonic flowmeter.Practical implicationsThis study has certain application value, which can provide theoretical support for the design of high-precision ultrasonic flowmeters and design guidance.Originality/valueIt is worth emphasizing that there are few research studies on the influence factors of temperature. This paper focuses on the influence of the temperature change on the flowmeter that is modeled, and the high precision flow parameter test system is designed based on the established model.

Fourier Collocation Approach With Mesh Refinement Method for Simulating Transit-Time Ultrasonic Flowmeters Under Multiphase Flow Conditions.

A numerical model for transit-time ultrasonic flowmeters operating under multiphase flow conditions previously presented by us is extended by mesh refinement and grid point redistribution. The method solves modified first-order stress-velocity equations of elastodynamics with additional terms to account for the effect of the background flow. Spatial derivatives are calculated by a Fourier collocation scheme allowing the use of the fast Fourier transform, while the time integration is realized by the explicit third-order Runge-Kutta finite-difference scheme. The method is compared against analytical solutions and experimental measurements to verify the benefit of using mapped grids. Additionally, a study of clamp-on and in-line ultrasonic flowmeters operating under multiphase flow conditions is carried out.

Applicability of hybrid ultrasonic flow meter for wide-range flow-rate under distorted velocity profile conditions

In transit-time ultrasonic flow meters (TOF), the flow rate is derived from the transit time of an ultrasonic pulse between two ultrasonic transducers. To convert the transit time into flow rate, a profile factor (PF) is required. Because the PF strongly depends on the velocity profile, a precise calibration of the PF is essential to the accuracy of the TOF. Hence, a field calibration, referred to as on-site calibration, is desirable. In this study, a hybrid ultrasonic flow meter that helps calibrate the TOF using ultrasonic Doppler velocimetry (UDV) is proposed for on-site calibration by integrating the velocity profiles over the cross-sectional area of a pipe. Thus, a new system of hybrid ultrasonic flow meter was developed. The maximum flow rate measured using a conventional UDV is significantly lower than that measured using the TOF. Therefore, a system was developed to measure higher velocities and flow rates. The system is novel in that the transit time and velocity profile can be simultaneously measured using a de-aliasing method. To evaluate the influence of the velocity profile on the PF, experiments were conducted under a wide range of flow-rate conditions, which otherwise cannot be implemented using the conventional UDV. To evaluate the influence of the velocity profile in the pipe, an obstacle plate was placed at 8D upstream the test section. Radially arranged measuring lines were employed. The experimental results show that increasing the number of measuring lines did not improve the accuracy of the TOF. On the other hand, the flow rate could be accurately obtained using the proposed UDV by measuring the velocity profile even under distorted flow conditions. Furthermore, the calibration of the PF based on the flow rate obtained using the proposed UDV was found to be feasible.

A Fourier Collocation Approach for Transit-Time Ultrasonic Flowmeter Under Multi-Phase Flow Conditions

A numerical model for a clamp-on transit-time ultrasonic flowmeter (TTUF) under multi-phase flow conditions is presented. The method solves equations of linear elasticity for isotropic heterogeneous materials with background flow where acoustic media are modeled by setting shear modulus to zero. Spatial derivatives are calculated by a Fourier collocation method allowing the use of the fast Fourier transform (FFT) and time derivatives are approximated by a finite difference (FD) scheme. This approach is sometimes referred to as a pseudospectral time-domain method. Perfectly matched layers (PML) are used to avoid wave-wrapping and staggered grids are implemented to improve stability and efficiency. The method is verified against exact analytical solutions and the effect of the time-staggering and associated lowest number of points per minimum wavelengths value is discussed. The method is then employed to model a complete TTUF measurement setup to simulate the effect of a flow profile on the flowmeter accuracy and a study of an impact of inclusions in flowing media on received signals is carried out.

Research and realisation of reciprocal electronic circuits for gas ultrasonic flow meter

The transit-time ultrasonic flow meters often show non-zero-flow rate when the flow is stationary due to the variations between transducers, which results in a zero-flow error. Moreover, the zero-flow error may change along with the measurement environment which causes the zero-drift error. The zero-flow error and zero-drift error will lead to false flow detection and influence the measurement stability at low velocities. Reciprocal operation theory has been proven to be an effective technique to eliminate zero-flow error. Therefore, reciprocal electronic circuits for gas ultrasonic flow meter are designed in this study. The circuits are first modelled in PSpice to validate its effectiveness. It is shown that both the zero-flow error and the zero drift are reduced significantly with the reciprocal circuits. Besides, the optimum matched resistor is determined by simulation. Second, three experiments are carried out to test the reciprocal circuits including transducers paired experiment, temperature test and flow calibration. Finally, it is verified that the reciprocal circuits can improve the measurement accuracy and stability for gas ultrasonic flow meter and the calibration results show that the gas ultrasonic flow meter (USM) with reciprocal circuits can achieve 1.0% measurement accuracy in 0.3-30 m/s.

Impact of Portal Hemodynamic Changes in Partial Liver Grafts on Short-Term Graft Regeneration in Living Donor Liver Transplantation.

Regeneration of partial liver grafts is critical for successful living donor liver transplantation (LDLT), especially in adult recipients. The purpose of this study was to investigate the intraoperative hemodynamic changes in partial liver grafts and characterize their potential impact on post-transplant liver regeneration in LDLT. We examined the portal venous flow (PVF) and hepatic arterial flow (HAF) to partial liver grafts by means of ultrasonic transit time flowmeter of donors immediately before graft retrieval and of the corresponding recipients after vascular reconstruction in 48 LDLT cases. We evaluated post-transplant liver regeneration according to the changes in graft liver volume between the time of transplantation and the 7th post-transplant day. There was a significant increase in PVF to the partial liver grafts in recipients (rPVF) compared with that in donors. In contrast, graft HAF in recipients significantly decreased compared with that in donors. The rPVF inversely correlated with graft weight (GW)-recipient body weight ratio (GRWR), whereas HAF volume showed no significant correlation. The rPVF/GW positively correlated with the rate of liver regeneration (GRR), which inversely correlated with GRWR. The rPVF/GW was significantly higher, and GRR tended to be larger in the small graft group than in the non-small graft group. Intraoperative portal hemodynamic changes in partial liver grafts strongly affect their post-transplant regeneration. In particular, in small liver grafts, an immediate and remarkable increase in graft PVF may contribute to rapid liver regeneration after LDLT if the increased PVF remains within a safe range.

An Enhanced Technique for Ultrasonic Flow Metering Featuring Very Low Jitter and Offset.

This paper proposes a new, improved method for water flow metering. It applies to a transit time ultrasonic flow meter device. In principle, the flow of a given liquid in a pipe is obtained by measuring the transit times of an ultrasonic wave in the upstream and downstream directions. The difference between these times is, in theory, linearly proportional to the liquid flow velocity. However, the fainter the flow is, the smaller the transit time difference (TTD) is. This difference can be as low as a few picoseconds, which gives rise to many technical difficulties in measuring such a small time difference with a given accuracy. The proposed method relies on measuring the TTD indirectly by computing the phase difference between the steady-state parts of the received signals in the upstream and downstream directions and by using a least-square-sine-fitting technique. This reduces the effect of the jitter noise and the offset, which limit measurement precision at very low flow velocity. The obtained measurement results illustrate the robustness of the proposed method, as we measure the TTD at no-flow conditions, with a precision as low as 10 ps peak-to-peak and a TTD offset of zero, within a temperature range from room temperature to 80 °C. This allows us to reach a smaller minimum detectable flow when compared with previous techniques. The proposed method exhibits a better trade-off between measurement accuracy and system complexity. It can be completely integrated in an ASIC (application specific integrated circuit) or incorporated in a CPU- or micro-controller-based system.

Numerical Simulation of Transit-Time Ultrasonic Flowmeters by a Direct Approach.

This paper deals with the development of a computational code for the numerical simulation of wave propagation through domains with a complex geometry consisting in both solids and moving fluids. The emphasis is on the numerical simulation of ultrasonic flowmeters (UFMs) by modeling the wave propagation in solids with the equations of linear elasticity (ELE) and in fluids with the linearized Euler equations (LEEs). This approach requires high performance computing because of the high number of degrees of freedom and the long propagation distances. Therefore, the numerical method should be chosen with care. In order to minimize the numerical dissipation which may occur in this kind of configuration, the numerical method employed here is the nodal discontinuous Galerkin (DG) method. Also, this method is well suited for parallel computing. To speed up the code, almost all the computational stages have been implemented to run on graphical processing unit (GPU) by using the compute unified device architecture (CUDA) programming model from NVIDIA. This approach has been validated and then used for the two-dimensional simulation of gas UFMs. The large contrast of acoustic impedance characteristic to gas UFMs makes their simulation a real challenge.

伝播時間差式超音波流量計の精度に及ぼす速度分布の影響

The transit time ultrasonic flow meter (TOF) has been widely applied in industry due to its advantages, such as applicability to larger diameter pipe, small pressure loss, etc. Since the TOF derives flow rate from the change of the trantis time between two sensors, the accuracy of TOF is strongly influenced by velocity profile in the pipe. Velocity profile is influenced by not only the upstream condition but also the shape of tranducer pocket on the pipe wall. In this paper, in order to evaluate influence of velocity distribution on the accuracy of TOF, a system to measure the tiransit time and the velocity profile simulataneouly was developed. In experiments, an obstacle plate was installed to distort velocity profiles. The velocity profiles and their transit times of ultrasonic pulses were compared. As a result, line-averaged velocities calculated from the transit time were good agreement with the line-averaged velocities obtained by using UDM.

Model Study for Upgrading of Sungai Belibis Pump Sump

Experimental study of hydraulic physical model investigates the flow characteristics in the pump sump. The model features four pumps (7.91 L/s for pump 1 and 2, and 4.74 L/s for pump 3 and 4) with a total of 9 cases of study. Different values of water depth (180mm, 200mm, and 300mm) and pump flow rate (15L/s, 20L/s, and 25L/s) were conducted. Velocity measurements at the dividing cross section were obtained by an Acoustic Doppler Velocimeter (ADV), pump flow rate by flow meter (Dyna Handheld Transit Time Ultrasonic Flow Meters) and swirl angle in the suction intakes were measured by a vortimeter/rotometer. No vortices were occurred near the suction intake at the high and medium water level conditions. In the low water level condition with high flow rate (25L/s), vortex Type 4 or 5 were observed near the suction intake and this condition is unacceptable. Since this condition indicate the presence of vortices more than Types 2 and an uneven flow through the suction intake, this can be categorized as the worst case and not recommended for pump sump operation.

3D Isosceles Triangular Ultrasonic Path of Transit-Time Ultrasonic Flowmeter: Theoretical Design and CFD Simulations

Increasing the coverage rate of ultrasonic path to flow field is helpful to improve measurement results' accuracy of transit-time ultrasonic flowmeters while asymmetric flow or turbulence exists. In this paper, a 3D isosceles triangular ultrasonic path is presented considering the width of the ultrasonic signal and the maximum coverage rate of the ultrasonic path to flow field. To evaluate the feasibility and effectiveness of the path proposed, computational fluid dynamics simulations of three pipeline configurations, including straight pipeline, single elbow, and contracted pipeline upstream ultrasonic flowmeter 3D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pipe</sub> (diameter of pipeline, D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pipe</sub> ), 5D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pipe</sub> , or 8D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pipe</sub> long are performed. In particular, inlet velocity of flow ranges from 0.1 to 10 m/s. Meanwhile, control simulation of U-type ultrasonic path is discussed to verify the effect of coverage rate of ultrasonic path to flow field on measurement results. It is shown that the proposed 3D isosceles triangular ultrasonic path, whose coverage rate is 54%, does well in improving the stability and accuracy of measurement results while pipeline configuration upstream flowmeter changes.

Parallel strip waveguide for ultrasonic flow measurement in harsh environments.

Wetted ultrasonic transit time flow meters typically consist of one or more pairs of transducers, containing piezoelectric elements, which alternate between transmitting and detecting an ultrasonic pulse. Typical piezoelectric materials and the adhesives used to attach the piezoelectric element in such devices can be damaged by hostile environments, such as extreme temperature, potentially limiting possible applications of ultrasonic flow measurement techniques. We have investigated a design for a flow meter with an integrated thermal buffer waveguide consisting of five parallel stainless steel strips. These, in addition to thermal protection, may function as a transducer array, with the possibility of steering the emitted field. Because the buffer strips used in the transducer assembly are thin, one might expect Lamb-like guided waves to propagate along it. However, the finite width of the strips has a significant effect on the propagation characteristics of the guided waves. In this work, the effect of the waveguide's small rectangular cross-section has been studied. Additionally, we have examined the effect of thermal gradients on the average sound speed and dispersion characteristics of such strip waveguides. We also suggest modifications to the plate geometry, which can alter both the frequency content and the shape of the transmitted pulse, potentially giving a better signal to use in flow measurement.

Continuous flow phantom for the calibration of an ultrasonic transit-time flowmeter

INTRODUCTION: Ultrasound Transit-Time flowmeters are based on the fact that the time required for an ultrasound pulse to propagate through a given distance in a moving medium is a function of the vectorial sum of pulse propagation velocity and medium velocity. The most common application of this flowmeter in medicine is in the evaluation of blood flow in arteries and veins during heart vascular surgery. The present article describes the design, construction and evaluation of a flow phantom for transit-time flowmeters calibration. METHODS: Basically, it is a hydraulic circuit containing degassed and distilled water. In such a circuit, a constant differential water level is established between two columns that are interconnected by tubes with defined resistance, which determines a known flow rate. A basic theoretical model to estimate the system Reynolds Number and resistance was developed. RESULTS: A flow range between 4.43 ± 0.18 ml.min-1 and 106.88 ± 0.27 ml.min-1 was found to be compatible with physiological values in small vessels. The pressure range was between 0.20 ± 0.03 cmH2O and 12.53 ± 0.07 cmH2O, and the larger Reynolds Number was 1134.07. Experimental and theoretical resistance values were similar. CONCLUSION: A reproducible phantom was designed and built to be assembled with standard low-cost materials and is capable of generating adjustable and continuous flows that can be used to calibrate TTFM systems.

Electronic circuit design for reciprocal operation of transit-time ultrasonic flow meters

The reciprocal operation theory has been used in the circuit design of transit-time ultrasonic flow meters (USMs) to promote their zero flow performances. In this paper, the authors analyzed the transfer functions of the inter-conversion between acoustic and electric signals on each transducer, indicated that the equivalent load consistency for each transducer between the transmitting and the receiving phases would guarantee the transmitting and the receiving transfer functions equal, and thus guarantee the reciprocal operation of the USM system. In order to achieve the “load consistency” condition in practical systems with non-ideal parameters, a method of applying short pulse excitation and fixing the equivalent load in the “free oscillation period” of the transmitting transducer is proposed. Based on this method, several circuit designs are shown in the paper, the impedance preferences are also analyzed. Practical experiments done with these circuits show clear improvement in both promoting the accordance of the signals received in both directions and reducing the zero flow error in the measurement.

Excitation signal's influence on ultrasonic transit time flow meter's performance

Ultrasonic flow meter performance was analyzed. Ultrasound transit time was used for flow rate estimation. Time of flight was measured using cross correlation processing. Simultaneous channels excitation was used. Ultrasonic signals were excited using low voltage (4V pp) signal generator, received signals were amplified 30 dB and simultaneously acquired by 100 Ms/s 10 bit analog-to-digit converters. Subsample delay estimation was used. Flow rate was varied from 10 l/h to 200 l/h. Measurement channel diameter 8 mm was used. It is complicated to obtain the unbiased reference signal for correlation processing. Various combinations of signals travelling in measurement channel were used for cross-correlation processing. Performance of correlation function and time of flight estimator variance were studied. Variable gain amplifier usually is used for signal dynamic range matching to A/D converter input. Gain influence on time of flight was a subject to study. It has been concluded that gain control introduces systematic errors in time of flight estimator. Influence of the temperature of electronics (pulser, receiver, A/D converter, reference clock etc.) and ultrasonic transducers on the delay estimator was studied. It was concluded that the major temperature-related systematic error comes from the pulser. Performance of the meter was studied when narrowband and spread spectrum signals were used for ultrasound excitation across temperature and flow rate range. It has been concluded that spread spectrum signal allows for better zero flow stability over temperature and lower time of flight variation.

Numerical Analysis of Flow Field Characteristics in Three-Z-Shaped Ultrasonic Flowmeter

The flow field characteristics in U-typed bend has been extensively studied for transit time ultrasonic flowmeters designing, but for the flowmeter with three-Z-shaped round pipe there is still lack of corresponding research. This paper presents a computational fluid dynamics (CFD) approach for modeling of the three-Z-shaped ultrasonic flowmeter and studying of internal fluid field characteristics based on Reynolds stress model (RSM). The fluid velocity profile in the three ultrasound path is obtained using CFD and secondary flow in cross section also is analyzed. The simulation results show that the internal flow fields in the flowmeter are not fully developed turbulence with asymmetric axial velocity distribution and dramatic changes along the flow direction, and there are obvious secondary cross flows on theirs cross-sections. The CFD simulations provide useful insights into the flow field associated with ultrasonic flowmeters design.

Acoustic propagation in viscous fluid with uniform flow and a novel design methodology for ultrasonic flow meter

Ultrasonic flow meter with non-invasive no-moving-parts construction has good prospective application for space on-orbit fluid gauging. In traditional pulse transit time flow meter, inconsistency of ultrasonic transducers leads to measurement error and plane wave theory, bases of transit time flow meter, is valuable only for low-frequency wave propagation in inviscid fluid and will lose feasibility when fluid viscosity is considered. In this paper, based on the hydrodynamics of viscous fluid, wave propagation with uniform flow profile is mathematically formulated and a novel solution for viscous fluid using potential theory is firstly presented. Then a novel design methodology of continuous ultrasonic flow meter is proposed, where high measurement rangeability and accuracy are guaranteed individually by solving the integral ambiguity using multi-tone wide laning strategy and the fractional phase shift using phase lock loop tracking method. A comparison with transit time ultrasonic flow meter shows the advantage of proposed methodology. In the end, parametric analysis of viscosity on wave propagation and ultrasonic flow meter is compressively investigated.

Intraoperative Hemodynamic Evaluation of the Latissimus Dorsi Muscle Flap: A Prospective Study

The aim of this study was to assess intraoperatively the hemodynamic changes in the donor vessel of free latissimus dorsi (LD) flap before and after denervation and to analyze flow changes after flap transfer. Twenty-seven patients underwent LD muscle microvascular reconstruction for lower-limb soft tissue defects. Measurements of blood flow were performed intraoperatively by using a 2- to 5-mm probe ultrasonic transit-time flowmeter around the dissected vessels. Registrations were made in the thoracodorsal artery before and after harvesting the flap, after compressing and cutting the motor nerve, and after anastomosis. Mean blood flow of in situ harvested thoracodorsal artery as measured intraoperatively by transit-time flowmeter was (mean ± standard deviation) 16.6 ± 11 mL/min and was significantly increased after raising the flap to 24.0 ± 22 mL/min (p <0.05); it was 25.6 ± 23 mL/min after compressing the motor nerve and was significantly increased after cutting the motor nerve to 32.5 ± 26 mL/min (p <0.05). A significant increase of blood flow to 28.1 ± 19 mL/min was also detected in the thoracodorsal artery after flap transplantation with end-to-side anastomosis (p <0.05). Vascular resistance in the thoracodorsal artery significantly decreased after flap raising and anastomosis (from 7.5 ± 3.4 to 4.0 ± 1.9 and to 4.5 ± 2.4, respectively, p <0.05). LD flap harvesting increases blood flow and decreases resistance in the thoracodorsal artery, especially after denervation.

Online monitoring of transit-time ultrasonic flowmeters based on fusion of optical observation

It is well-known that transit-time ultrasonic flowmeters (TTUF) are unsuitable for bubble-contained flows. This paper presents a new online monitoring method based on optical observation, which monitors the functionality of the TTUF in the presence of bubbles in the fluid. The method avoids the unnecessary Emergency Shutdowns (ESD) due to bubble presence in the fluid by bubble detection. The proposed method accomplishes bubble identification through a combination of image processing and wavelet analysis. In addition, a new method is proposed which estimates single bubble size in horizontal pipes using a data fusion approach.

Direct measurement of hepatic blood flow during living donor liver transplantation in children

Background The changes in liver blood flow associated with living donor liver transplantation (LDLT) in children have not yet been studied. The aim of the present study was to investigate changes in hepatic hemodynamics before and after pediatric partial liver transplantation. Methods In 7 pediatric recipients with congenital cholestasis and native liver Child-Pugh classes B and C, portal vein flow (PVF) and hepatic arterial flow (HAF) were measured using an ultrasonic transit time flow meter before removal of the native liver and after transplantation and compared with donor left PVF and donor left HAF. Results The mean portal contribution to total hepatic blood flow was markedly decreased in the recipient native liver compared with that in the donor (69% ± 15% vs 32% ± 15%; P = .0003) and after reperfusion changed to almost the same ratio as that in the donor liver (73% ± 18%; P < .0001). Conclusion The extreme imbalance between PVF and HAF that is common in implanted partial liver in adult LDLT recipients was not observed in pediatric LDLT. After transplantation of an appropriately sized liver graft, the portal contribution to total liver blood flow normalized to the value for normal liver.