Sanehiro Wada

Development of Pulse Ultrasonic Doppler Method for Flow Rate Measurement in Power Plant Multilines Flow Rate Measurement on Metal Pipe

Ultrasonic Doppler method for a flow metering system has been developed. The method has the capability to obtain instantaneous velocity profiles along the ultrasonic beam. Our purpose is to apply the ultrasonic Doppler method to a flow rate measurement of feed- or recirculation- water in power plants. The principle of the flow measurement method is based on the integration of an instantaneous velocity profile over a pipe diameter. Hence, it is expected to eliminate installation problems such as entry length, also to follow transient flow rate precisely by increasing ultrasonic transducers. In this paper, we report that the errors are less than 1% just below a bend and sudden expansion pipe employing three measuring lines. And then, for constructing a basic system of a flow rate measurement in power plants, a transmission of ultrasound through a metallic wall is investigated, at first. Afterward, since there is no ultrasonic reflectors in the feedwater in power plants, cavitation bubbles are induced as ultrasonic reflectors and the results are appeared that cavitation bubbles are effective when the pipe material is metallic.

Analysis of Ultrasound Propagation in High-Temperature Nuclear Reactor Feedwater to Investigate a Clamp-on Ultrasonic Pulse Doppler Flowmeter

The flow rate of nuclear reactor feedwater is an important factor in the operation of a nuclear power reactor. Venturi nozzles are widely used to measure the flow rate. Other types of flowmeters have been proposed to improve measurement accuracy and permit the flow rate and reactor power to be increased. The ultrasonic pulse Doppler system is expected to be a candidate method because it can measure the flow profile across the pipe cross section, which changes with time. For accurate estimation of the flow velocity, the incidence angle of ultrasound entering the fluid should be estimatedusing Snells law. However, evaluation of the ultrasound propagation is not straightforward, especially for a high-temperature pipe with a clamp-on ultrasonic Doppler flowmeter. The ultrasound beam path may differ from what is expected fromSnells law due to the temperature gradient in the wedge and variation in the acoustic impedance between interfaces. Recently, simulation code for ultrasound propagation has come into use in the nuclear field for nondestructive testing. This article analyzes and discusses ultrasound propagation, using 3D-FEM simulation code plus the Kirchhoff method, as it relates to flow profile measurement in nuclear reactor feed-water with the ultrasonic pulse Doppler system.

Development of ultrasonic pulse-train Doppler method for velocity profile and flowrate measurement

We present a novel technique for measuring the velocity profile and flowrate in a pipe. This method, named the ultrasonic pulse-train Doppler method (UPTD), has the advantages of expanding the velocity range and setting the smaller measurement volume with low calculation and instrument costs in comparison with the conventional ultrasonic pulse Doppler method. The conventional method has limited measurement of the velocity range due to the Nyquist sampling theorem. In addition, previous reports indicate that a smaller measurement volume increases the accuracy of the measurement. In consideration of the application of the conventional method to actual flow fields, such as industrial facilities and power plants, the issues of velocity range and measurement volume are important. The UPTD algorithm, which exploits two pulses of ultrasound with a short interval and envelope detection, is proposed. Velocity profiles calculated by this algorithm were examined through simulations and excellent agreement was found in all cases. The influence of the signal-to-noise ratio (SNR) on the algorithm was also estimated. The result indicates that UPTD can measure velocity profiles with high accuracy, even under a small SNR. Experimental measurements were conducted and the results were evaluated at the national standard calibration facility of water flowrate in Japan. Every detected signal forms a set of two pulses and the enveloped line can be observed clearly. The results show that UPTD can measure the velocity profiles over the pipe diameter, even if the velocities exceed the measurable velocity range. The measured flowrates were under 0.6% and the standard deviations for all flowrate conditions were within ±0.38%, which is the uncertainty of the flowrate measurement estimated in the previous report. In conclusion, UPTD provides superior accuracy and expansion of the velocity range.

Study on the Optimal Number of Transducers for Pipe Flow Rate Measurement Downstream of a Single Elbow Using the Ultrasonic Velocity Profile Method

This paper presents a new estimation method to determine the optimal number of transducers using an Ultrasonic Velocity Profile (UVP) for accurate flow rate measurement downstream of a single elbow. Since UVP can measure velocity profiles over a pipe diameter and calculate the flow rate by integrating these velocity profiles, it is also expected to obtain an accurate flow rate using multiple transducers under nondeveloped flow conditions formed downstream of an elbow. The new estimation method employs a wave number of velocity profile fluctuations along a circle on a pipe cross-section using Fast Fourier Transform (FFT). The optimal number of transducers is estimated based on the sampling theorem. To evaluate this method, a preliminary experiment and numerical simulations using Computational Fluid Dynamics (CFD) are conducted. The evaluating regions of velocity profiles are located at 3 times of a pipe diameter () for the experiment, and 1 and for the simulations downstream of an elbow, respectively. Reynolds numbers for the experiment and simulations are set at and , respectively. These results indicate the efficiency of this new method.

Effect of low-frequency ultrasound on flow rate measurements using the ultrasonic velocity profile method

This study presents a low-frequency ultrasonic propagation analysis using the finite-element method (FEM). Experimental results of flow rate measurements using the ultrasonic velocity profile (UVP) method are also presented. The ultrasound frequency, pipe diameter, and pipe wall thickness are 0.274 MHz, 590.6 mm, and 9.5 mm, respectively. Six waves are generated per ultrasound pulse. To analyze the entire pipe region, the FEM is combined with the Kirchhoff method. The experiments of flow rate measurements are conducted using the high Reynolds number calibration facility at the National Metrology Institute of Japan. The range of the Reynolds number is from 4.4×106 to 1.7×107. Wide spreading of the ultrasonic beam in the axial direction of the pipe is observed because of multiple reflections in the pipe wall. This wide beam affects the measured velocity profile, particularly in the region near the pipe wall. In addition, the flow rate errors are approximately 10% (deviating by 1.1%) across the investigated range of Reynolds number. This result suggests that the experimental flow rate errors might be used as correction factors of flow rate measurements using the UVP method.

The optimum distribution of cavitation bubbles for a flow rate measurement using ultrasonic Doppler method

An ultrasonic Doppler method (UDM) can achieve high accurate flow rate measurement in underdeveloped flow or transient flow. In the conventional method, the UDM for flow rate measurement requires suspending particles in fluid as reflectors. However, in some applications, for example, a flow rate measurement in clean water, any particle does not exist in the flow and hence, the conventional UDM cannot be applied to the measurement. The authors group has proposed the ultrasonic cavitation bubbles as reflectors in the flow measurement by UDM. The cavitation bubbles inside the pipe are excited by the low frequency Langevin transducer attached to the outside wall. The distribution of the cavitation bubbles has a large influence on the accuracy of the measurement. In this report, the optimum distribution of the cavitation bubbles was examined. The intensity of the harmonic components of the measure sound pressure corresponds to the intensity of cavitations bubbles. In order to examine the measurement accuracy of the flow rate against the intensity of cavitation bubble, the sound pressure distribution in the cavitation excitation part was measured by the hydrophone.

Effects of out-of-plane double bent pipe on ultrasonic flow metering

Ultrasonic Velocity Profile (UVP) method can be applied and succeeded for complicated flow as short inlet length from the double bent pipe. However, the flow of out-of-plane double bent pipe is more complicated and also more difficult to measure the highly accurate flowrate compare to in-plane double bent pipe. To solve this difficultly, the precise three-dimensional velocity profile forming is necessary. Multiple measurement lines are investigated for the out of plane double bent pipe to form the three-dimensional velocity profile. Moreover, the multiple measurement lines ultrasonic flow metering needs to optimize the number of measurement lines. In addition, the distance from the outlet to the measurement point as inlet length is also important. Therefore, the aims of this study are both estimate the optimal number of measurement lines and find out the minimum inlet length to measure the accurate flowrate on the out-of-plane double bent pipe by using a sampling transducers rating estimation method with signal processing technique. The minimization of the inlet length was started from 3 D, 4 D and 5 D. The estimation of optimal number of measurement lines was executed in the condition of Re~40,000. The out-of-plane double bent pipe was spread the out-of- plane angle at 0°, 8° and 16°. In this study, the circumferential velocity profiles are reconstructed from many velocity profiles measured around the center of pipe using single measurement lines. These circumferential velocity profiles come as the form of wave. Fourier Transform technique (FT) changes the waveform data to design the number of measurement lines by using sampling rate theory.

Development of Plus Ultrasonic Doppler Method for Flow Rate Measurements of Power Plant: Multiline Flow Rate Measurement for Non Developed Flow

Flow metering system is being developed using plus ultrasonic Doppler method. The principle is an integration of instantaneous velocity profile over a pipe diameter so that it is expected to be able to eliminate installation problems such as entry length as well as to follow transient flow rate precisely. Flow metering principle by plus ultrasonic Doppler method in a circular pipe depends on the alignment of measuring lines. In this paper, influence of number of measuring lines on the flow rate measurements for power plant have been investigated for non developed flows in a vertical pipe.Copyright