Application Analysis of Ultrasonic Flow Meter

Abstract: The application analysis information of ultrasonic flow meter is provided to you by excellent flow meter and flow meter manufacturers. Abstract: Through the analysis of the measurement principle of ultrasonic flowmeter and the factors affecting ultrasonic measurement accuracy, the specific method to solve the measurement accuracy is elaborated, and the guiding suggestions for instrument selection and installation are provided. The flow is the middle weight of coalbed methane production gathering and transportation. More flowmeter manufacturers choose models and price quotations. You are welcome to inquire. The following is the application analysis article details of ultrasonic flowmeters. Through the analysis of the measurement principle of the ultrasonic flowmeter and the factors affecting the ultrasonic measurement accuracy, the specific method to solve the measurement accuracy is expounded in detail, and the guiding suggestions for the selection and installation of the instrument are provided. Flow rate is one of the important parameters in CBM production gathering and transportation. The accuracy of the flow measurement value will directly affect the stability of the system operation and the economic interests of both parties in the handover measurement. At present, there are many types of flowmeters based on various principles produced in China, such as positive displacement flowmeters, vortex flowmeters, differential pressure flowmeters, ultrasonic flowmeters, etc. Among them, the ultrasonic flowmeter is a kind of non-contact instrument that has only been practically applied with the rapid development of integrated circuit technology. Compared with other types of flowmeters, ultrasonic flowmeters have the characteristics of no pressure loss, high cost performance, and wide measurement range (generally up to 20:1). The measurement range of the ultrasonic flowmeter of the propagation velocity difference method can reach 300:1. Therefore, the use of ultrasonic flowmeters in the measurement of large-diameter CBM has outstanding advantages. Especially in urban gas transmission, there is a big difference between the peak gas consumption during the day and the trough of gas consumption at night, and the wide measurement range of the ultrasonic flowmeter can be well adapted to this. 1. Measuring principle of ultrasonic flowmeter The ultrasonic flowmeter converts electrical energy into ultrasonic energy by an ultrasonic converter, transmits and passes through the measured fluid in a certain way, and the receiver receives the ultrasonic signal for display and totalizing by the display totalizer. , to realize the detection and display of the flow. The two ultrasonic transducers (also known as ultrasonic probes) of the ultrasonic flowmeter are installed on both sides of the outer wall of the pipe, symmetrically at a certain inclination angle (see Figure la) or on the same side (see Figure 1b). Ultrasonic transducers are usually made of lead zirconate titanate ceramics. Under the excitation of electricity, the transducer generates ultrasonic waves that enter the pipe wall at a certain incident angle, and propagate into the fluid in the form of transverse waves in the pipe wall. The form propagates in the fluid, finally passes through the medium, and is received by another transducer through the wall of the tube. During the measurement, the two sensors are transmitting and receiving probes for each other. In order to ensure that the ultrasonic waves transmitted in the two directions are at the same gas flow rate, the two transducers are designed to transmit ultrasonic waves to each other at the same time. According to the different measurement parameters, the measurement principles can be divided into three types: time difference method, frequency difference method and phase difference method. Only the first two types that are commonly used are introduced. Taking Figure la as an example, the angle between the sensor and the pipeline normal isθ1,δis the wall thickness of the pipe, and D is the nominal diameter of the pipe. The propagation velocity of the ultrasonic pulse signal is c, the fluid velocity is v, and the angle between the connection line between the two sensors (T1 and T2) and the natural gas flow direction isθ, then the component vcos of the ultrasonic velocity in the natural gas flow directionθ, and the resultant velocity after superposition with the fluid velocity is c±vcosθ. That is, when the direction of the ultrasonic horizontal velocity component is consistent with the direction of the fluid velocity, the combined velocity of the two is c+vcosθ, and vice versa for c-vcosθ. 1.1 Measurement principle of difference method When T1 transmits and T2 receives, the transmission time from T1 to T2: When T2 transmits and receives T1, the transmission time from T2 to T1: After sorting out: Then the frequency difference between the two directions: from the formula (4) It can be seen that the gas velocity v can be obtained by measuring the frequency difference, and the volume flow can be calculated from this, that is, the daily production formula of natural gas can be obtained. and t21, two time parameters, the gas flow rate v can be obtained, and the formula of natural gas daily production can be obtained: From formulas (6) and (8), it can be seen that the daily natural gas production Q measured by the ultrasonic flowmeter is related to the ultrasonic The pulse signal speed is irrelevant. 2. Performance characteristics Compared with traditional flow meters such as orifice plate, turbine and vortex street, ultrasonic flowmeter has the characteristics of strong adaptability and convenient operation (see Table 1). 3. Factors that affect the accuracy of ultrasonic flow measurement There are many factors that affect the accuracy of ultrasonic flowmeters. The main factors are two aspects: the influence of the performance of the instrument itself; the influence of the installation quality. 3.1 Flowmeter selection The measurement principle of the propagation velocity difference method is to measure the average flow velocity on the ultrasonic propagation path. Whether this average flow velocity can correctly reflect the flow velocity on the flow section has an impact on the accuracy of the measurement. Therefore, a dual-channel or multi-channel flowmeter should be used in the design to improve the uncertainty of the average flow rate measured by a single channel. In actual use, the accuracy of the monophonic flowmeter is±2.0%, which can meet the requirements of process control. The accuracy of the multi-channel flowmeter is±1.0%, which can meet the requirements of custody transfer measurement. There are two types of measuring bodies of ultrasonic flowmeters: external clamping type and self-contained measuring tube type. The clamp-on ultrasonic flowmeter is convenient and flexible to use, especially suitable for renovation projects. However, the actual accuracy of field applications is often degraded by errors such as negligence in work, installation distance and flow area measurement. The use of ultrasonic flowmeters with measuring tubes reduces the influence of the flow velocity distribution in the upstream flow, reduces the influence of the length of the front and rear straight pipes, and eliminates the influence of the location of the converter installed in the field. It is recommended to use the measurement method with its own measuring tube when the on-site process conditions permit.
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