Imported pipeline type natural gas flowmeter

Imported pipeline type natural gas flowmeterIn a flowing fluid, if a cylinder is placed perpendicular to the flow direction, regular vortices known as Karman vortices will alternate on both sides behind the cylinder within a certain Reynolds number range. The rotation direction of the vortex is inward, with the upper column rotating clockwise and the lower column rotating counterclockwise. The vortices are arranged asymmetrically downstream of the vortex generator.

Imported pipeline type natural gas flowmeterThe sensor consists of two parts: a vortex generator (fluid barrier), a detection element, and an instrument body; The converter includes a preamplifier, filtering and shaping circuit, D/A conversion circuit, output interface circuit, terminals, bracket, protective cover, etc. In recent years, intelligent flow meters have also incorporated microprocessors, display communication, and other functional modules into the converter.

Structural principle:
The pipeline natural gas flowmeter consists of two parts: the sensor and the converter. The sensor includes a vortex generator (resistance fluid), a detection element, and an instrument body; The converter includes a preamplifier, filtering and shaping circuit, D/A conversion circuit, output interface circuit, terminals, bracket, protective cover, etc. In recent years, intelligent flow meters have also incorporated microprocessors, display communication, and other functional modules into the converter.
(1) Vortex generator is the main component of the detector, which is closely related to the flow characteristics (instrument coefficient, linearity, range, etc.) and resistance characteristics of the instrument. The requirements for it are as follows:
① Can control the synchronous separation of vortices along the axis direction of the vortex generator.
② Within a wide range of Reynolds numbers, there are stable vortex separation points that maintain a constant Strouhal number.
③ It can generate strong vortex streets and has a high signal-to-noise ratio.
④ The shape and structure are simple, easy to process and standardize geometric parameters, as well as the installation and combination of various detection components.
⑤ The material should meet the requirements of fluid properties, namely corrosion resistance, wear resistance, and temperature change resistance.
⑥ The natural frequency is outside the frequency band of the vortex signal. Various shapes of vortex generators have been developed, which can be divided into two categories: single vortex generators and multi vortex generators. The basic shapes of a single vortex generator include cylindrical, rectangular, and triangular columns, as well as other shapes; All shapes are deformations of these basic forms. The triangular cylindrical vortex generator is one of the most widely used types. D in the figure represents the diameter of the instrument. To improve the strength and stability of vortices, multiple vortex generators can be used, but their application is not widespread.
(2) There are five ways to detect vortex signals using flow meters.
① Directly detect the differential pressure on both sides of the vortex generator using detection elements installed inside the generator.
② A pressure hole is opened on the vortex generator, and a detection element is installed in the pressure hole to detect the differential pressure on both sides of the generator.
③ Detecting the alternating circulation around the vortex generator‘
④ Detect the alternating differential pressure on the back of the vortex generator.
⑤ Detecting vortex columns in the wake. According to these 5 detection methods, different types of vortex flowmeters can be constructed using different detection techniques such as thermal sensitivity, ultrasound, stress, strain, capacitance, electromagnetic, optoelectronic, optical fiber, etc.