Ultrasonic Gas Flowmeter Research Articles

Multipath ultrasonic gas flow-meter based on multiple reference waves

Several technologies can be used in ultrasonic gas flow-meters, such as transit-time, Doppler, cross-correlation and etc. In applications, the approach based on measuring transit-time has demonstrated its advantages and become more popular. Among those techniques which can be applied to determine time-of-flight (TOF) of ultrasonic waves, including threshold detection, cross correlation algorithm and other digital signal processing algorithms, cross correlation algorithm has more advantages when the received ultrasonic signal is severely disturbed by the noise. However, the reference wave for cross correlation computation has great influence on the precise measurement of TOF. In the applications of the multipath flow-meters, selection of the reference wave becomes even more complicated. Based on the analysis of the impact factors that will introduce noise and waveform distortion of ultrasonic waves, an averaging method is proposed to determine the reference wave in this paper. In the multipath ultrasonic gas flow-meter, the analysis of each path of ultrasound needs its own reference wave. In case study, a six-path ultrasonic gas flow-meter has been designed and tested with air flow through the pipeline. The results demonstrate that the flow rate accuracy and the repeatability of the TOF are significantly improved by using averaging reference wave, compared with that using random reference wave.

Development of a New Type Ultrasonic Gas Flowmeter

In this paper, a new method on how to design ultrasonic gas flow meter is presented. Ultrasonic sensor with large area and center frequency 120kHz is selected and ultrasonic sensor driving circuit based on IRF7389 is designed to drive the sensor, the received ultrasonic signal can reach 1000mv in the distance of 30cm, thus can make the amplifying circuit easy to design. In the ultrasonic receiving circuit, the no inverting amplifier is used to realize preliminary amplification; followed by the second-order band pass filter with the center frequency for 120kHz to filter out the noise, gain adjustable amplifier circuit is designed based on digital potentiometer, ultrasonic signal after comparison circuit outputs square wave to control chip time TDC-GP2 to achieve time interval measurements. Finally, the system is calibrated and the calibration results show that the measurement accuracy is 1%.

A Model-Based Transit-Time Ultrasonic Gas Flowrate Measurement Method

Based on the transit-time ultrasonic gas flowrate measurement principle, a new model-based time-of-flight (TOF) measurement method is proposed. The proposed TOF measurement method includes two parts, the signal preprocessing and the model-fitting. Zero-phase filtering and independent component analysis with reference (ICA-R) are used to realize the signal preprocessing. The least-squares algorithm is used to implement the model-fitting and hence to obtain the TOF. A new single-acoustic-path ultrasonic gas flowmeter prototype with the inner diameter of 100 mm is developed and experiments are carried out to test the performance of the prototype. Experimental results show that the proposed signal preprocessing can effectively correct the distorted/noise-polluted measurement signal. In addition, the proposed model-based TOF measurement method is effective and can implement TOF measurement with higher repeatability and low standard deviation. For the gas flowrate ranges from 5 to 50 $\text{m}^{3}$ /h, the repeatability error of gas flowrate measurement is less than 1.99% and the maximum relative error of flowrate measurement is less than 3.27%. For the gas flowrate ranges from 50 to 500 $\text{m}^{3}$ /h, the repeatability error of gas flowrate measurement is less than 0.51% and the maximum relative error of flowrate measurement is less than 1.43%.

Variable ratio threshold and zero-crossing detection based signal processing method for ultrasonic gas flow meter

Abstract Ultrasonic gas flow meter has unique advantages and good application prospects for measuring the gas flow rate in medium to large diameter pipelines. However, there is energy attenuation in the ultrasonic wave propagation process, and the propagation path of the ultrasonic wave will shift with the gas flow rate increasing, which makes it difficult for the commonly used transit-time method to determine the feature point and obtain the accurate measurement results. Therefore the characteristics of the ultrasonic echo signal are studied, and a variable ratio threshold and zero-crossing detection based digital signal processing method is proposed for ultrasonic gas flow meter. The ultrasonic echo signal is normalized, and the ratio value is used as the threshold value to determine the feature point. Based on the analysis of the amplitude of the extreme points under different flow rates, the threshold value is determined according to the intersection of the amplitude interval of the extreme points. According to the feature point, the zero-crossing method is adopted to calculate the ultrasonic wave propagation time. This digital signal processing method is implemented in real time in the digital system with the FPGA (Field Programmable Gate Array) and the DSP (Digital Signal Processor) as the double cores, and the gas flow calibration experiments are conducted to verify the effectiveness of the proposed digital signal processing method and developed system.

Flow profile identification with multipath transducers

Accuracy of flow rate determination is very critical to an ultrasonic gas flowmeter, which is sensitive to the flow profile under measurement and cannot be obviously improved with traditional weighted integration methods for multipath transducers. Therefore, on one hand, more attentions are paid to intelligent learning algorithms (e.g. artificial neural networks) in recent studies to accurately construct the mapping relation between multipath velocities and the flow rate. However, the bottleneck that a trained network is only customized for a certain flow profile greatly restricts its application. On the other hand, many researchers turn to reconstruct the flow field but so far all flow visualization methods cost too much and are difficult to realize online. In this paper, an intelligent method of flow profile identification for multipath ultrasonic flowmeters is developed to solve the above predicament. Based on support vector machine, a multiclass identifier is constructed to automatically identify the flow profile to be measured from 65 typical flow patterns. Extremely high identification accuracy of 99.49% for test and 100% for training is achieved while the test result still reaches 88.46% even when a measurement uncertainty of ±2% is considered. A comparison with extreme leaning machine further reveals the identification performance and robustness of the proposed flow profile identifier. Different piping configurations, installation positions and angles can be therefore accurately identified, which indirectly realizes the flow visualization and can comprise an intelligent system of ultrasonic flow measurement when combined with the intelligent flow rate determination algorithms.

Improvement of gas ultrasonic flowmeter measurement non‐linearity based on ray tracing method

Gas ultrasonic flowmeters are widely used in natural gas industry. When flow velocity achieves to tens of meters per second, the measurement error may appear significant non-linearity with flow velocity increased. In order to solve this problem, reasons of non-linearity are discussed based on the ray acoustics theory. First, the two-dimensional ray tracing method is introduced and realised by Matlab. Second, both DN100 and DN500 diametric single path gas ultrasonic flowmeters are simulated, respectively. The ultrasonic wave propagation trajectory, transit time, path angle and receiving position of transducer are analysed with increasing flow velocities 1–50 m/s. Third, it is noted that the assumption of traditional velocity measurement model is not consistent with the actual ultrasound propagation. Therefore, a corrected model is proposed. Through comparing results of traditional and corrected models, the measurement error is reduced up to 4%, and the measurement non-linearity is improved.

Mathematical Modeling of Ultrasonic Gas Flow Meter Based on Experimental Data in Three Steps

According to experimental data, the features of ultrasonic echo are studied, and a new mathematical model of ultrasonic gas flow meter is built so as to reflect the effects of the excitation signal and gas flow rate on ultrasonic echo. This mathematical model consists of three parts, and is established in three steps. An amplitude sub-model expressed as a polynomial is set up with the curve fitting method to express the non-linear relationship between the echo amplitude and the gas flow rate. A process sub-model described as an output-error model is established by the system identification method to reveal the influence of excitation on the echo shape. A delay time sub-model is built with piecewise fitting to obtain a relationship between the propagation time and the gas flow rate. These sub-models can quantitatively analyze the relationship between the excitation signals, gas flow rates, ultrasonic echo amplitudes, shapes, and propagation time.

Application of extreme learning machine to gas flow measurement with multipath acoustic transducers

To reduce the large integration errors brought by traditional methods in gas flow measurement under complex flow field, artificial neural network, support vector machine and other intelligent algorithms have been put into use. But these intelligent methods consume much time for training and need intensive user intervention for network design. This paper proposes to apply extreme learning machine to multipath ultrasonic flowmeters, which can analytically determine the output weights of networks instead of error backpropagation algorithm and iterative tuning of the parameters, and therefore provide high metering accuracy at extremely fast learning speed as well as require least human intervention. To test its effectiveness under different flow field and sensitivity to complex flow profiles, extreme learning machine is applied to determine the flow rate under two piping configurations, which can produce mild and severe flow disturbances. The determination errors are compared with a traditional integration method on the position of 5D and 10D as well as with the path orientation of 0° and 90°. Then 7 installation angles and 9 installation positions are respectively configured to study the performance and sensitivity of UFMs to installation effects. Finally, a comparison between extreme learning machine and other two intelligent algorithms is made in training and test time, the mean squared error and the maximal metering error under severe flow disturbance. It is found that extreme learning machine has rather high determination accuracy for flow rate at extremely fast learning speed and it is insensitive to the installation effects of ultrasonic gas flowmeter.

Optimization of Neural Network by Genetic Algorithm for Flowrate Determination in Multipath Ultrasonic Gas Flowmeter

Artificial neural network (ANN) was proposed as an effective method to help multipath ultrasonic flowmeter (UFM) reduce its measurement error when determining the flowrate of complex flow field. However, the effectiveness of the ANN method heavily depends on the network architecture specified by the designer, and also the provided initial weights and layer biases. This hinders the ANN to be widely used in actual UFMs. This paper proposes a genetic algorithm (GA) optimized ANN method (GANN) to be used in UFMs. The GA is utilized to determine ANN architecture based on its efficient parallel advantage in global search to replace traditional trial and error approach or empirical method. In addition, the initial weights and biases are optimized by GA, which is capable to avoid the network getting stuck with local minimum and qualify it for good generalization ability. Tests are implemented on numerical models simulating a six-path UFM installed downstream single or double elbows with complex flow field passing through it. Comparisons between the results of classical Gaussian quadrature, existing ANN, and proposed GANN are given for verification. The flowrate determination error of GANN is only 40% ~ 62% of existing ANN, which is extremely smaller than the Gaussian quadrature method. In addition, the output of GANN is much more stable than existing ANN, as proper initial weights and layer biases will be generated by GA for iteration process even random data are given for training.

Energy transfer model and its applications of ultrasonic gas flow-meter under static and dynamic flow rates.

Most of the ultrasonic gas flow-meters measure the gas flow rate by calculating the ultrasonic transmission time difference between the downstream and upstream. Ultrasonic energy attenuation occurs in the processes of the ultrasonic generation, conversion, transmission, and reception. Additionally, at the same time, the gas flow will also affect the ultrasonic propagation during the measurement, which results in the ultrasonic energy attenuation and the offset of ultrasonic propagation path. Thus, the ultrasonic energy received by the transducer is weaker. When the gas flow rate increases, this effect becomes more apparent. It leads to the measurement accuracy reduced, and the measurement range narrowed. An energy transfer model, where the ultrasonic gas flow-meter under without/with the gas flow, is established by adopting the statistical analysis and curve fitting based on a large amount of experimental data. The static sub model without the gas flow expresses the energy conversion efficiency of ultrasonic gas transducers, and the dynamic sub model with the gas flow reflects the energy attenuation pattern following the flow rate variations. The mathematical model can be used to determine the minimum energy of the excitation signal for meeting the requirement of specific measurement range, and predict the maximum measurable flow rate in the case of fixed energy of excitation signal. Based on the above studies, a method to enhance the excitation signal energy is proposed under the output power of the transmitting circuit being a finite value so as to extend the measurement rage of ultrasonic gas flow-meter.

Gas ultrasonic flow rate measurement through genetic-ant colony optimization based on the ultrasonic pulse received signal model

For gas ultrasonic flowmeters, the signals received by ultrasonic sensors are susceptible to noise interference. If signals are mingled with noise, a large error in flow measurement can be caused by triggering mistakenly using the traditional double-threshold method. To solve this problem, genetic-ant colony optimization (GACO) based on the ultrasonic pulse received signal model is proposed. Furthermore, in consideration of the real-time performance of the flow measurement system, the improvement of processing only the first three cycles of the received signals rather than the whole signal is proposed. Simulation results show that the GACO algorithm has the best estimation accuracy and ant-noise ability compared with the genetic algorithm, ant colony optimization, double-threshold and enveloped zero-crossing. Local convergence doesn’t appear with the GACO algorithm until –10 dB. For the GACO algorithm, the converging accuracy and converging speed and the amount of computation are further improved when using the first three cycles (called GACO-3cycles). Experimental results involving actual received signals show that the accuracy of single-gas ultrasonic flow rate measurement can reach 0.5% with GACO-3 cycles, which is better than with the double-threshold method.

Numerical Analysis of Transducer Installation Effect on Ultrasonic Gas Flow Meter

As for ultrasonic gas flow meters, special attention should be paid to transducer installation effect as the flow disturbed by transducers will greatly affect the transit time determination and accordingly reduce metering accuracy. This paper presents a numerical method to analyze the disturbed effects based on Computational Fluid Dynamic (CFD), which can give valuable guides for transducer installations. Different pipe configurations covering a wide velocity range are modelled to simulate the actual flow field in different chords for three transducer installations including protrusion, recess and half protrusion. Then, detailed results are presented and the mechanism is analyzed to give suggestions about better transducer installations and a modified weighting factor method to improve the incredible error is also given in this paper.

Double threshold ultrasonic distance measurement technique and its application.

The double threshold method realized by hardware circuits and high performance timing chip TDC-GP21 was successfully adapted to solve the key problem of ultrasonic distance measurement, the accurate time-of-flight (TOF) measurement of ultrasonic wave. Compared with other techniques of TOF measurement, the double threshold method presented in this work can suppress noise in the received signal, and achieve a time resolution of around 22 ps and real-time. This method is easy to realize and pertains the advantage of low cost. To compensate temperature and pressure deviations, a temperature measurement module of 10 mK in precision as well as a pressure measurement module of 0.01% in accuracy was developed. The system designed in this work can be exactly used as a two paths ultrasonic gas flowmeter without any adjustment of the hardware circuit. The double threshold method was further corroborated using experiment results of both the ultrasonic distance measurement and ultrasonic gas flow measurement. In distance measurement, the maximum absolute deviation and the maximum relative error are 0.69 mm and 0.28%, respectively, for a target distance range of 100-600 mm. In flow measurement, the maximum absolute deviation and the worst repeatability are 1.16% and 0.65% for a flow in the range of 50-700 m(3)/h.

CFD Aided Investigation of Multipath Ultrasonic Gas Flow Meter Performance Under Complex Flow Profile

This paper presents a systematic investigation of the influence of complex flow profiles on the performance of multipath ultrasonic gas flow meter by using computational fluid dynamics (CFDs) simulation. To guarantee the overall agreement between the CFD predictions and the measurements, the meshing approaches, generation of boundary layers, turbulence models, and wall treatment methods for CFD simulation are elaborated carefully. The performances of a multipath ultrasonic gas flow meter under complex flow profiles, regarding to an out-plane double-elbow with a half-moon block and an out-plane double-elbow with a half-moon block equipped with a Spearman conditioner, are investigated. The simulation results demonstrate that for complex flows with strong asymmetric and swirling velocity profiles inside an out-plane double-elbow pipeline with a half-moon block, a four-path ultrasonic flow meter located at 20-D right after the second elbow together with a Spearman conditioner installed 16-D upstream the meter is of providing a flow velocity estimation that the error is within ±0.5%, while the Reynolds number ranges from 3.25×103 to 3.25×105. The effect of sound path orientation on the performance of flow meter is also discussed.

Flow Measurement Model of Ultrasonic Flowmeter for Gas-Liquid Two-Phase Stratified and Annular Flows

An error correction model for ultrasonic gas flowmeter was proposed to explore the potential of an ultrasonic flowmeter for metering gas-liquid stratified and annular flows. The gas and liquid mass flowrates could be obtained provided that the gas quality and physical prosperities were known. A single-path ultrasonic flowmeter was investigated and the error of the apparent volumetric flowrate was considered as mainly resulting from the shrinkage of the gas flow path due to the presence of a liquid phase. Fourteen void fraction models were selected for the stratified and annular flows and evaluated against experimental data. It was demonstrated that the root-mean-square error of the gas mass flowrate can be reduced from 19.0% to below 5% by employing either of Lockhart & Martinelli, Baroczy, Spedding & Chen, or Wallis void fraction models. Lockhart & Martinelli model is recommended due to its higher accuracy, simpler formulation, sounder theoretical support, and stronger immunity to pressure variation. The error correction model proposed in this work provides a basis for developing new combination measurement methods with an ultrasonic flowmeter as one component.

Numerical Simulating Nonlinear Effects of Ultrasonic Propagation on High-speed Ultrasonic Gas Flow Measurement

The effects of nonlinear ultrasonic propagation on high-speed ultrasonic gas flow measurement are analyzed based on the sound line equation derived from Snell's geometric acoustic law. A math ematical model for the ultrasonic propagation path in ultrasonic flowmeter pipe is built, and the relationship between x and r is calcula ted by MATLAB programming and ode45 simulating. The ultrasonic propagation path at the flow rate of 3 � 30m/s is simulated in the assumed boundary conditions of the pipeline, transducer installation and fluid state. It shows that the nonlinear propagation characte ristics cause the large deviations of the position of received ultrasonic waves in conditions of different flow rates, which strongly aff ects the stability and accuracy of flow measurement. The simulated offset data of the receiving position are useful for the high-s peed gas ultrasonic flowmeter installation and dry calibration on clamp-on ultrasonic flowmeters.

Realization of a multipath ultrasonic gas flowmeter based on transit-time technique

A microcomputer-based ultrasonic gas flowmeter with transit-time method is presented. Modules of the flowmeter are designed systematically, including the acoustic path arrangement, ultrasound emission and reception module, transit-time measurement module, the software and so on. Four 200kHz transducers forming two acoustic paths are used to send and receive ultrasound simultaneously. The synchronization of the transducers can eliminate the influence caused by the inherent switch time in simple chord flowmeter. The distribution of the acoustic paths on the mechanical apparatus follows the Tailored integration, which could reduce the inherent error by 2–3% compared with the Gaussian integration commonly used in the ultrasonic flowmeter now. This work also develops timing modules to determine the flight time of the acoustic signal. The timing mechanism is different from the traditional method. The timing circuit here adopts high capability chip TDC-GP2, with the typical resolution of 50ps. The software of Labview is used to receive data from the circuit and calculate the gas flow value. Finally, the two paths flowmeter has been calibrated and validated on the test facilities for air flow in Shaanxi Institute of Measurement & Testing.

Improving interference immunity of ultrasonic gas flowmeters with clamp-on probes

The possibility of detecting a weak desired signal passed through gas among signals propagating in the pipe wall when sounding the flow with clamp-on probes is demonstrated. The possibility of applying this method to measurement of gas flow rate in large-size pipelines is also shown.

A Study of Velocity Distribution Impact of Wall Roughness on Ultrasonic Gas Flowmeter

In order to study the effects of velocity distribution of ultrasonic gas flow meter based on wall roughness, , a full developed turbulence model is established based on the theory of prandtl mixing length and flow loss coefficent λ has been calculated by using Colebrook friction correlation formula after analyzing time interval difference measuring method of ultrasonic flow meter. Through Matlab calculating and simulating velocity distribution in different conditions of wall roughness about the model shows and through Fluent simulating, velocity vector and pressure distribution in smooth and rough tube have been compared and analyzed. The experimental results shows that quantification of velocity distribution based on wall roughness can been solved with the model, and the analysis results have certain instructive significance to the development of ultrasonic gas flow meter.

Note: Ultrasonic gas flowmeter based on optimized time-of-flight algorithms

A new digital signal processor based single path ultrasonic gas flowmeter is designed, constructed, and experimentally tested. To achieve high accuracy measurements, an optimized ultrasound driven method of incorporation of the amplitude modulation and the phase modulation of the transmit-receive technique is used to stimulate the transmitter. Based on the regularities among the received envelope zero-crossings, different received signal's signal-to-noise ratio situations are discriminated and optional time-of-flight algorithms are applied to take flow rate calculations. Experimental results from the dry calibration indicate that the designed flowmeter prototype can meet the zero-flow verification test requirements of the American Gas Association Report No. 9. Furthermore, the results derived from the flow calibration prove that the proposed flowmeter prototype can measure flow rate accurately in the practical experiments, and the nominal accuracies after FWME adjustment are lower than 0.8% throughout the calibration range.