A Brief Analysis of The Reason For Affecting The Accuracy of Vortex Shedding Flow Meter In Measuring

1. The overview of the article

The flow is an important parameter of the monitoring process of enterprise production, and is an important means to ensure high quality, efficiency, safety, stable operation and to improve the environment. The measurement of the gas flow has important significance in  the chemical industry, environmental protection, energy and other industries. It can strengthen material management and improve energy management, material transfer, trade settlement economic analysis and evaluation in accounting and benefit. In a sense, the measurement of flow is the eye of enterprise, and it also is a meter on efficiency. Modern enterprises have become increasingly demanding on measurement of the shedding flow. Gas measuring instruments like vortex shedding flow meter, turbine flow meter and ultrasonic flow meter are commonly used in industrial measurement of differential pressure flow meters. The vortex shedding flow meter has the advantages of simple and firm structure, and is suitable for multi type of fluid and the measurement of high precision, and has wide range and small pressure loss. With all these characteristics, it is widely used. The article is based on the analysis and improvement of some reasons that may easily affect the accuracy of the data in the gas measurement by vortex shedding flow meter, so as to improve the further accuracy of gas flow measurement.

2.The principle and structure of working

Vortex shedding flow meter is to place non-streamline vortex in a fluid. Fluid in the vortex generating body alternately releases regular and alternately ranged flow vortex on both sides of the two column separation. Within some ranges of vortex (Reynolds number), the  separation frequency and volume flow is proportional to the fluid of the vortex that flowing through the vortex flow sensor.

3. The analysis and solution of factors that affecting the accuracy

Because of characteristics of the structure and  the principle of measurement of the vortex shedding flow meter, vortex flow meter measurement accuracy will be influenced greatly by vibration, pulse interference, measurement medium, installation methods, the condition of the fluid and so on.

(1) Pipeline vibration

Vortex shedding flow meter essentially is a fluid oscillatory type flow meter. In addition to the piezoelectric detection type vortex shedding flow meter, vortex shedding flow meter is particularly sensitive to other mechanical vibration. Due to the output pulse of the vortex flow shedding meter is proportional to the flow rate, vortex lift of detection and velocity square is proportional to the measured fluid density, So in a small flow, vortex flow the sensor signal is of low frequency and small amplitude. If low-frequency interference is severely affected by the vibration of the pipeline, the output pulse error will be more; along with the increase of flow rate, vortex flow sensor signal frequency becomes large and the enhanced amplitude of interference effect of low frequency vibration of the pipeline. When the output pulse is weakened, error becomes smaller.

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