Transit-time Ultrasonic Flowmeter Research Articles

Flow Rate and Volume Estimates from Variable Frequency Drive Operated Drainage Sump Pumps

Highlights This article provides an overview of operations and benefits of using a variable frequency drive to operate agricultural subsurface drainage system sump pumps. A methodology is proposed to monitor flow rates leaving agricultural subsurface drainage pump stations via a MATLAB algorithm. The results of this research were mixed because the algorithm estimates did not always match with the corresponding flowmeter measurements. Abstract. Subsurface drainage plays a crucial role in excess water removal through perforated pipes buried in the soil. The Red River Valley of eastern North Dakota and west central Minnesota often requires pumped drainage outlets due to its flat topography, with many modern systems incorporating variable frequency drives (VFD) for improved efficiency. VFDs adjust pump speeds to match drainage needs, but this dynamic operation complicates accurate flow rate estimation for edge-of-field monitoring. This project aimed to devise an automated method for calculating flow rate estimates from VFD pumping systems involving tank geometry, operational water levels, and pump duty cycling. Linear regressions with calibration data from a transit-time ultrasonic flowmeter produced mixed outcomes. Some linear regressions revealed errors in calculated versus measured flow rate of =14%, while other regressions showed errors nearing 40%. To address this, future efforts should explore methods incorporating the pump’s electrical characteristics. This approach would provide a more accurate representation of the unstable and intricate pumping operations during transient conditions. Keywords: Edge-of-field monitoring, Flow rate, Pump, Red River Basin, Subsurface drainage, Variable frequency drive

Time of Flight Measurement Method Combining Threshold Method and Cross-Correlation Method

With various benefits such as a large range ratio, suitability for large-diameter measurement, and lack of excess pressure drop, ultrasonic flowmeters (UFMs) have been widely adopted in natural gas measurement. The accuracy of flow measurement in transit-time UFMs is mostly dependent on the accurate measurement of time of flight (TOF). The threshold method, the cross-correlation (CC) method, and the model-based method are examples of traditional TOF calculation techniques. However, the threshold method is susceptible to such factors as waveform distortion, amplitude attenuation, and noise, the CC method is constrained by the sampling frequency, and the model-based method necessitates a significant investment in calculation time and resources. Based on the analysis of the shortcomings of traditional TOF measurement methods, a TOF measurement method that combines the threshold method and CC method is presented. This method integrates the advantages of the high measurement resolution of the threshold method and the strong robustness of the CC algorithm. The results demonstrate that the flow rate accuracy and the repeatability of the TOF are greatly improved by this method.

Examining Transit-Time Ultrasonic Flowmeter Inaccuracies during Changing Gas Velocity Profiles

This study investigates the impact of changes in velocity profiles on the measurement inaccuracies of gas flow streams detected by an ultrasonic flowmeter. The cross-sectional velocity profile was influenced by the downhill flow rate, causing variations in the shape factor coefficient. The flowmeter processing equation should consider the factor of shape coefficient variations. Consideration for these variations can result in errors in the measurement of the flow stream. The processing equation assumes a single, constant value for the shape factor coefficient, which can lead to inaccuracies. This article covers the inaccuracies of the transit-time ultrasonic flowmeter caused by a change in the velocity profile of the flowing gas, such as air. A realistic flow system was established with measured flow rates ranging from 43 m3/h to 225 m3/h. The findings of this study can serve as a valuable reference for the design and implementation of more accurate and efficient flow measurement systems that can enhance process efficiency.

A novel approach to multi-path ultrasonic transit time flow meter based on measurement model analysis to improve accuracy

Ultrasonic transit time flow meter (UTTFM) is commonly used in a wide range of applications. It is commonly believed amongst researchers, industrialists, and standard committee members that due to nonuniform flow velocity distribution inside the pipe (flow velocity profile) the measured flow velocity using UTTFM needs to be corrected by the flow profile. Mathematical analysis of UTTFM measured quantity shows that UTTFM measures flow correctly when flow is fully developed or laminar. However, the measurement results using flow profile correction factor produces erroneous values. The UTTFM measurement model assessment shows, when flow is not fully developed, there are unknown quantities contributed by flow velocity in the axial and diametrical direction to measurement results. These unknown quantities lead to erroneous measurement results when it is simply corrected by flow profile. Assessment of the UTTFM error model shows that using multi-path UTTFM can significantly reduce the impact of the unaccounted quantities and improve accuracy. A novel approach to UTTFM design utilizing multiple acoustic paths (using different planes and transmitting angles) is proposed to reduce potential error for UTTFM. This approach is consistent with the general measurement modeling method with incomplete information recommended by JCGM GUM-6:2020.

A miniaturized transit-time ultrasonic flowmeter based on ScAlN piezoelectric micromachined ultrasonic transducers for small-diameter applications

Transit-time ultrasonic flowmeters (TTUFs) are among the most widely used devices for flow measurements. However, traditional TTUFs are usually based on a bulk piezoelectric transducer, which limits their application in small-diameter channels. In this paper, we developed a miniaturized TTUF based on scandium-doped aluminum nitride (ScAlN) piezoelectric micromachined ultrasonic transducers (PMUTs). The proposed TTUF contains two PMUT-based transceivers and a π-type channel. The PMUTs contain 13 × 13 square cells with dimensions of 2.8 × 2.8 mm2. To compensate for the acoustic impedance mismatch with liquid, a layer of polyurethane is added to the surface of the PMUTs as a matching layer. The PMUT-based transceivers show good transmitting sensitivity (with 0.94 MPa/V surface pressure) and receiving sensitivity (1.79 mV/kPa) at a frequency of 1 MHz in water. Moreover, the dimensions of the π-type channel are optimized to achieve a measurement sensitivity of 82 ns/(m/s) and a signal-to-noise ratio (SNR) better than 15 dB. Finally, we integrate the fabricated PMUTs into the TDC-GP30 platform. The experimental results show that the developed TTUF provides a wide range of flow measurements from 2 to 300 L/h in a channel of 4 mm diameter, which is smaller than most reported channels. The accuracy and repeatability of the TTUF are within 0.2% and 1%, respectively. The proposed TTUF shows great application potential in industrial applications such as medical and chemical applications.

Industrial experiences show clamp-on ultrasonic transit time flow meters assumptions lead to erroneous measurement results

Clamp-on (externally mounted) ultrasonic transit time flow meters (UTTFM) are portable, non-intrusive, easy to use, applies to a wide range of pipe sizes, and manufacturers claim accuracy is about 1%. However, industrial field experiences show that the instrument reading are inconsistent (results of simultaneous measurements on the same pipe, location using identical instrument can deviate up to 43%). Researches into clamp-on UTTFM implementation show the process employs various assumptions. Theoretical evaluations of these assumptions show all of them lead to erroneous measurement results; field measurements confirm the results of theoretical analysis. This article identifies and systematically examines each assumptions and the potential impacts on UTTFM measurement results. Techniques to minimize the effects of the assumptions are also discussed.

ULTRASONIC MEASUREMENT TECHNOLOGY IN AUTOMATED CONTROL OF WATER RESOURCES

Control of water resources is becoming an important strategic issue. That is why authorities set the goal for wa-ter agencies to manage the availability of water and create regulations to its rational use. The main point in water control is measurement. There are three important aspects of measurements of water resources: at water extraction from nature, at the consumption and at custody transfer. Control of water consumption sometimes is based not on measurements, but on preliminary estimation, for example, by pumping.
 Ultrasonic measurement technology as a key feature of automated control of resources has a potential role in this market. In contrast to mechanical (turbine) meters, ultrasonic meters have a priority because they also give a possibility to realize smart metering. In contrast to electromagnetic meters, which also measure with high accuracy and realize smart functions, ultrasonic meters much more suitable for rough water, wastewater and sewage. Such water resources are usually poorly controlled, which means that no one knows their exact cost.
 Measurement is mandatory to control cost and for billing. Accuracy is important issue, especially when we say about measurements in large pipe diameters. There is practically no alternative to ultrasonic flow meters. Market of diverse meters concentrated on diameters under 400 mm. For larger diameters, only ultrasonic meters are in use. They have many chords, difficult algorithms for data processing. Thus, they are applicable over a very wide flow range.
 In this paper, we discover transit-time ultrasonic flow meters to understand features of their measurement theory taking into account all factors affecting their work. This article describes errors inherent in these flowmeters during measurements.
 As far as accuracy is significantly important in billing, the cost of 1% measurement error in consumption of water resources for small (DN50÷DN150 mm) and large (DN200÷DN1200 mm) pipe diameters has been evaluated and analyzed. The losses from the installation of low-quality metering devices are demonstrated and discussed.

Determination of Propagation Times of Finite Ultrasonic Signals in the UFM Measuring Path

This article provides a brief analysis of the error in calculating the discrete crosscorrelation function of the transit-time ultrasonic flowmeter signals. Special attention is paid to the study of the influence of the obtained discrete correlation function inaccuracy on the ultrasonic flowmeter’s propagation times determining error. It is known that for real time-limited acoustic signals, the discrete correlation function values are calculated with a significant error. The consequence of this is the appearance of the measurement error of the time delay between signals. The reason for this phenomenon is incorrect truncation of finite length digital sequences of the received acoustic signals. The report presents and describes an improved cross-correlation method for determining the time difference. The new algorithm takes into account the existing discretizing parameters of the received UPS – sampling frequency, sequence size and the truncated signal’s shape. Theoretical analytical expressions for the signals discrete cross-correlation function estimating are obtained as an approximation of a continuous function (the method of trapezoids and Simpson is used as an integral replacement). The numerical simulation by MatLab explains the error formation essence in the signal times difference calculating.

Peak Ratio Characteristic Value Sequence Based Signal Processing Method for Transit-Time Ultrasonic Gas Flowmeter

The transit-time ultrasonic gas flowmeter plays a vital part in the measurement field with its unique advantages. In recent years, it has developed into a research hotspot in the field of gas flow measurement. However, while the ultrasonic signal propagates in gas, the amplitude fluctuation of the ultrasonic signal is produced under the condition of energy attenuation and unstable flow field. This leads to inaccurate transit time of ultrasonic signal that causes flow calculation errors. Aiming at this problem, a signal processing method is proposed in this paper for the transit-time ultrasonic gas flowmeter based on the peak ratio characteristic value sequence (PRCVS). Through the research on the mathematical model of ultrasonic signal, the ratio of the amplitude of adjacent peaks is defined as the peak ratio characteristic value (PRCV) of the peak. According to the corresponding relationship between the PRCV and the peak serial number, a set of reference PRCVS is established. By matching the characteristic value of the ultrasonic signal with the reference characteristic value sequence, the peak serial number can be determined. In this research, the PRCVS-based signal processing method is applied to the gas flow measurement system based on time-to-digital converter (TDC) that has strict requirements on the peak serial number which can verify the validity of the method. The calibration experiment of basic measurement performance test and the unstable flow field experiment of the curved pipe were performed on the gas flow standard device, which verified the stability and validity of the method proposed in this paper.

An Algorithm to Minimize the Zero-Flow Error in Transit-Time Ultrasonic Flowmeters

Transit-time ultrasonic flowmeters are widely used in industry to measure fluid flow. In practice, ultrasonic flowmeters either show a zero-flow error or suffer from a significant random error due to a limited signal-to-noise ratio, requiring a significant amount of averaging to achieve good precision. This work presents a method that minimizes the zero-flow error while keeping the random error low, independent of the hardware used. The proposed algorithm can adjust to changing zero-flow errors, while a flow is present. The technique combines the benefits of two common methods of determining the transit time difference between the upstream and downstream ultrasonic waves: cross correlation and zero-crossing detection. The algorithm is verified experimentally using a flow loop. It is shown that the zero-flow error can be greatly reduced without compromising the random error or increasing circuit complexity.

Analyzing the Fluid Flow of Transit-Time Ultrasonic Flowmeter with Image Processing Technique and Developing a Quality Metric Depending on Pipe Profile

The ultrasonic transit-time method measures the velocity and quantity of fluids in circular type pipes by using the difference of transit time between the ultrasonic pulses propagating with and against the flow direction. This method gives the average velocity of the fluid along a particular acoustic path. At least two ultrasonic transducers are used for an acoustic path. The multipath ultrasonic flowmeters have more acoustic paths. In this paper, the acoustic path between two transducers is described as pixels for the turbulent flow and formed a flow map for ideal flow conditions such as no elbow or bend depending on pipe profile. Using the obtained pixel values, the average fluid velocity is calculated between two transducers. Finally, a quality metric that calculates the ideal average fluid velocity ratio between the acoustic paths for the turbulent flow is developed. Thus, researchers can evaluate their designs with this quality metric.

Ultrasonic-Based Sensor Fusion Approach to Measure Flow Rate in Partially Filled Pipes

Flow rate measurement in pipes is essential for many applications. Thus, there have been a variety of flow meters developed that incorporate different technologies. However, a typical limitation in flow meters is that the pipe must be full in order to get an accurate flow reading. In many cases, this is not possible for practical reasons. When the pipe is full, ultrasonic flow meters can calculate the flow rate using known properties of the pipe and fluid, namely the cross-section, propagation path and fluid sound velocity. However, when the pipe is only partially filled, the propagation path is unknown which leads to an inability to calculate the correct flow rate. This paper presents a cost-effective sensor fusion approach to extend the capabilities of transit time ultrasonic flow meters to handle such scenarios. The approach determines the propagation path using capacitance-based level sensing, combined with fluid velocities ascertained via an ultrasonic sensor, leading to a significantly more accurate estimation of flow rates. Experiments in low flow rate situations validated the efficacy of the proposed model, with a 92% reduction of mean error in the lowest water height when compared to a conventional ultrasonic flow meter.

Novel FMCW-Interferometry Method Testing on an Ultrasonic Clamp-On Flowmeter

Paper represents the extended version of the authors previous works on the transit-time ultrasonic flowmeters accuracy increasing problem. We deal with a new method of ultrasonic clamp-on transit-time flow measurements using the linear frequency modulated continuous wave (FMCW) signals and interferometry based time-of-flight (delay) estimation technique. The analog FMCW signals preprocessing is performed by the heterodyne based scheme of the receiver (the results are so-called the beat signals). A statistically effective time delay estimator for the digitized beat signal model is discussed. The algorithm for the flow velocity (thus the flow rate) measurement based on the proposed estimator is considered, which can be implemented on the modern microcontroller with the relatively high computation performance. The algorithm effectiveness was experimentally proved for the clamp-on ultrasonic liquid flowmeter in the cases of a well and relatively poor matching between the piezo-transducers and pipe material. Experiments show that the standard deviation ( i.e. , the square root of the variance) and the bias can be reduced at 7–10 times in comparison with the traditional FMCW signal processing techniques. Further, we consider application of our approach to a designed type of flowmeters based on the electromagnetic waves.

ASYMMETRIC FLOW VELOCITY MEASUREMENT USING MULTIPATH ULTRASONIC FLOWMETER WITH ADAPTIVE WEIGHTING METHOD GUIDED BY TOMOGRAPHY

A conventional transit time ultrasonic flowmeter (USM) has a high accuracy for symmetric flow profiles but inaccurate for asymmetric flow profiles. Flow profile shapes can also change over time and difficult to predict. USM with tomographic configuration (USM-Tomo) can adapt to the flow profile changes but result in low temporal resolution. Meanwhile, USM with an adaptive weighting method can measure asymmetric flow velocity but limited to specific asymmetric flow profiles. An alternative scheme to determine adaptive weighting in various asymmetric flow profiles, we proposed a hybrid USM-Tomo. This scheme proposes programmable acoustic path configuration that could set the path mode between USM and tomography. Reducing computation of time of flight in each acoustic can be done by applying the dual-transducers technique. An adaptive weighting of hybrid USM-Tomo is calculated based on the mapping function between the set of velocity on 6 parallel paths of USM and average flow velocity from USM-Tomo. The mapping function is determined using machine learning, i.e., Artificial Neural Network (ANN) and Support Vector Regression (SVR). In the measurement phase, the average flow velocity is determined using the mapping function with input 6 parallel acoustic paths. Based on various types of asymmetric flow profiles used in the experiment, the 6 parallel acoustic paths of USM could produce average flow velocity with error below 1% compared to USM-Tomo. Therefore, the proposed hybrid USM-Tomo scheme has potential to be an alternative scheme for flow meter in industrial application.

Stable Hemodynamics within "No-Touch" Saphenous Vein Graft.

Purpose: To investigate the hemodynamics characteristics of the “no-touch” saphenous vein graft (SVG) conduits by nicardipine intraluminal administration in vivo experiment.Methods: A total of 59 consecutive patients were enrolled and underwent a sequential SVG to three non-left anterior descending (LAD) targets with the average runoff ≤2 mm, 30 with “no-touch” harvest technique (group A) and 29 with conventional preparation (group B). The patients were subject to nicardipine intraluminal injection during off-pump coronary artery bypass grafting (CABG) procedure. The intraoperative flow was measured with the ultrasonic transit time flow meter (TTFM), and the graft patency testified by multi-detector computed tomography (MDCT) angiography, respectively.Results: The baseline blood flow was higher in group A than that in group B (p <0.05). However, the increases in blood flow of SVG conduits in group A were lower than those in group B with 19.7 ± 5.9 vs. 35.4 ± 9.2 mL/min, 14.8 ± 5.6 vs. 23.1 ± 6.8 mL/min, 6.6 ± 2.1 vs. 11.2 ± 4.3 mL/min before the first, second, and third anastomose after nicardipine intraluminal administration, respectively (all p <0.01).Conclusions: No-touch SVGs were associated with higher baseline blood flow and less rises after nicardipine intraluminal administration during off-pump CABG procedure compared with conventional preparation. The no-touch SVGs seemed to be less spastic and well-tolerated on flow dilatation.

Reducing the additional error caused by the time‐difference method in transit‐time UFMs

In transit-time ultrasonic flow meters (UFMs), one of the most commonly used methods in the time domain is the cross-correlation method which is a time-consuming and high computational requirement approach. Hence, the time-difference approaches are preferred to reduce the computational requirement and increase the response time. However, the time-difference methods in comparison to conventional ones have been suffering from an additional bias error (ABE). In this study, using a numerical simulation method, the ABE is analysed and some effective factors such as pipe diameter, flow velocity and medium temperature are introduced. Then, an approach for removing or reducing the ABE is presented. Since the time-difference method has been used for Mach numbers <;0.1, it is shown that by using a second-order approximation, this method can be used for Mach numbers of more than 0.1, and the ABE resulting from this method is reduced to nearly zero. An experiment has been carried out on a 6 in transit-time UFM with an eight-path x -configuration to verify the validity of the second-order approximation method. The test results confirm that the proposed method can be successfully used in UFMs with the flow velocity greater than Mach 0.1.

Remote ischaemic preconditioning may prolong permissible period of hypothermic circulatory arrest in a porcine model

Objectives. The hypothermic circulatory arrest (HCA) is still of paramount importance in aortic arch surgery, but the safe period of the arrest is limited. Remote ischaemic preconditioning (RIPC) prepares the cerebral tissue for ischaemic insult. Prolongation of the permissible period of HCA with RIPC may have a major impact on the outcome of aortic operations requiring cessation of blood flow by decreasing the rate of neurological deficits. Design. Twenty pigs were randomised into the RIPC group (n = 10) and the control group (n = 10). The RIPC group underwent four cycles of transient hind limb ischaemia. Both groups underwent cooling with cardiopulmonary bypass to 11 °C followed by a 45-minute HCA and re-warming to 36 °C. Cerebral blood flow was measured with a transit time ultrasonic flowmeter from the right common carotid artery, and the arteriovenous oxygen difference was calculated from sagittal sinus and arterial blood samples. Measurements were taken at several time points during cooling and warming. Temperature coefficient (Q10) was calculated to determine estimated permissible periods of HCA. Results. The Q10 was 2.27 (1.98–2.58) for the RIPC group and 1.87 (1.61–2.25) for the control group. The permissible period of HCA at 18 °C was 26 minutes (20–33) in the RIPC group and 17 minutes (13–25) in the control group (p = .063)(Data expressed in medians and interquartile ranges). Conclusions. RIPC tends to suppress cerebral metabolism during cooling with cardiopulmonary bypass and may prolong estimated permissible period of HCA.

Effects of Velocity Profiles on Measuring Accuracy of Transit-Time Ultrasonic Flowmeter

Ultrasonic wave carries the information for flowing velocity when it is propagating in flowing fluids. Flowrate can be obtained by measuring the propagation time of ultrasonic wave. The principle of transit-time ultrasonic flowmeters used today was based on that the velocity is uniform along the propagation path of the ultrasonic wave. However, it is well known that the velocity profiles in a pipe are not uniform both in laminar flow and turbulent flow. Emphasis on the effects of velocity profiles across the pipe on the propagation time of ultrasonic wave, theoretical flowrate correction factors considering the real velocity profile were proposed for laminar and turbulent flow to obtain higher accuracy. Experiment data of ultrasonic flowmeter and weighting method are compared to verify the proposed theoretical correction factors. The average relative error of proposed correction factor is determined to be 0.976% for laminar flow and 0.25% for turbulent flow.

Research on a transit-time liquid ultrasonic flowmeter under unstable flow fields

A transit-time ultrasonic flowmeter calculates a flow rate by measuring the transit time of the ultrasonic signal. In flow measurement, there are energy attenuation and noise interference, and sometimes the ultrasonic signal will fluctuate or even distort, which makes it impossible to find the reference position and obtain the correct transit time under unstable flow fields. Therefore, based on the mathematical model of the ultrasonic signal, the characteristics of the peak ratios of adjacent peaks in the ultrasonic signal are studied, and a peak ratio matching method-based signal processing method is proposed for ultrasonic flowmeters. Firstly, through the analysis of signal quality, a standard peak ratio array is set up, then the peak ratios are calculated to obtain a real-time peak ratio array in the flow measurement, and finally a matching algorithm for elements in the standard peak ratio array and elements in the real-time peak ratio array are used to find the reference position. The transit time of the ultrasonic signal can be obtained by the reference position and positive zero-crossing points. The signal processing method is implemented in real time in the system where a time-to-digital converter timing module is used to measure zero-crossing times, an analog-to-digital converter sampling module is used to sample the ultrasonic signal at the same time, and two STM32 (32-bit ARM Cortex-M Microcontroller) processors are used to analyze the signal quality and data processing. The effectiveness of this signal processing method is verified by a large number of experiments.

The Effect of Internal Pipe Wall Roughness on the Accuracy of Clamp-On Ultrasonic Flowmeters

Clamp-on transit-time ultrasonic flowmeters (UFMs) suffer from poor accuracy compared with spool-piece UFMs due to uncertainties that result from the in-field installation process. One of the important sources of uncertainties is internal pipe wall roughness which affects the flow profile and also causes significant scattering of ultrasound. This paper purely focuses on the parametric study to quantify the uncertainties (related to internal pipe wall roughness) induced by scattering of ultrasound and it shows that these effects are large even without taking into account the associated flow disturbances. The flowmeter signals for a reference clamp-on flowmeter setup were simulated using 2-D finite element analysis including simplifying assumptions (to simulate the effect of flow) that were deemed appropriate. The validity of the simulations was indirectly verified by carrying out experiments with different separation distances between ultrasonic probes. The error predicted by the simulations and the experimentally observed errors were in good agreement. Then, this simulation method was applied on pipe walls with rough internal surfaces. For ultrasonic waves at 1 MHz, it was found that compared with smooth pipes, pipes with only a moderately rough internal surface (with 0.2-mm rms and 5-mm correlation length) can exhibit systematic errors of 2% in the flow velocity measurement. This demonstrates that pipe internal surface roughness is a very important factor that limits the accuracy of clamp on UFMs.