LUB series vortex flowmeter manual

Project Overview

1. Overview of vortex flowmeter

1. Principle and scope of application

The vortex flow sensor is one of the main flow meter products in the world and is widely used in petroleum, Chemical industry, metallurgy and other industrial sectors and municipal construction, environmental protection projects. Detect and measure the flow of liquids, gases and vapors.

The vortex flowmeter is a fluid oscillating flow meter with excellent technical performance indicators developed based on the "Karman vortex" principle. A non-streamlined columnar flow meter is inserted into the sensor housing through which the fluid flows. When an object is hit, two rows of staggered vortices will be generated on both sides behind the cylinder, as shown in Figure (1).

Figure (1): Karman vortex street diagram (2) Relationship between St and Re

The frequency of vortex separation is proportional to the flow rate and inversely proportional to the width of the cylinder. It can be used The following formula is expressed:

f=

In the formula: x St …(1)

f : vortex separation frequency;

St: dimensionless constant (Strauhal number); V: average flow velocity of fluid in the pipe;

d: width of the upstream surface of the cylinder ;

D: Inner diameter of sensor housing.

By detecting the separation frequency, the fluid flow velocity and instantaneous flow rate can be measured. The Strouhal number St, for a specific columnar vortex generator, is a function of the Reynolds number Re within a certain flow range, St The linear part of the function with Re is the linear measurement range of the vortex flow sensor, as shown in Figure (2). Therefore, the average flow rate and volume flow rate of the fluid in the pipeline can be determined by detecting the separation frequency f.

The number of pulses generated by a unit volume of fluid flowing through the sensor is called the instrument coefficient, represented by K (Formula 2):

k=N/Q (1/m³)…(2)

In the formula: k: instrument coefficient;

N: number of pulses;

Q: Fluid volume.

The vortices separate alternately on both sides of the rear column, generating pressure pulsations, which subject the detection body (also called the probe) in the sensor to an alternating force. See Figure (3). The piezoelectric sensor embedded in the detection body The crystal element is subjected to the action of alternating force to generate a charge frequency signal. After being processed by the detection circuit, it is output in the form of a frequency signal or converted into a standard signal form. When equipped with flow totalizing instruments and temperature and pressure sensors, parameters can be corrected and calculated.

2. Installation

1. Installation environment and conditions

1.1 The sensor can be installed indoors or outdoors. Special orders for special occasions.

1.2 The sensor can be installed on the pipeline 360° in the vertical direction along the axis of the pipeline, and can be installed horizontally, vertically, or tilted. When measuring liquids, the pipe must be filled with liquid, so the sensor installed vertically or tilted,Fluid flow direction must be from bottom to top.

1.3 The sensor should be installed on a pipe without mechanical vibration as much as possible.

1.4 The sensor should be kept as far away from magnetic and electrical interference places as possible.

1.5 When installing the sensor, the inner diameter of the pipe must be the same as the inner diameter of the sensor. If they are not exactly the same, a pipe slightly larger than the diameter of the sensor should be used, error: ≤3%.

1.6 There should be a long enough straight pipe section on the upstream and downstream sides of the sensor. Due to the different differences between the front and rear, please install it according to the requirements in the table and Figure 5.

After years of development, Supmea Measurement and Control Technology Co., Ltd. has become a domestic enterprise with strong comprehensive strength in the industrial automatic control system device manufacturing industry. The company is currently mainly engaged in industrial automatic control system devices and engineering complete sets. R&D, production, sales, technical consulting, services and other businesses. It is in a leading position in the domestic industry.