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1. Working principle of gas turbine flow meters A gas turbine flow meter consists of a turbine placed within the fluid to be measured. When gas enters the flow meter, it is streamlined and accelerated thanks to a specially designed rectifier; within a certain flow range, the angular velocity of the turbine is proportional to the flow rate. The principle of electromagnetic induction is utilized to generate a pulse signal that is proportional to the volumetric flow rate of the fluid. This signal is amplified by a pre-amplifier and shaped to determine the actual flow rate, which is then displayed on the LCD screen. If the signals detected by temperature and pressure sensors are fed into an intelligent flow integrator for processing, the flow rate under standard conditions can be determined and displayed on the LCD screen as well. 2. Structural principle of gas turbine flowmeters Impeller-type flowmeters are a type of velocity-based flowmeter, including turbine flowmeters, split-vane flowmeters, water meters, and impeller anemometers. The turbine flowmeter is the main type of impeller flowmeter; it has been in industrial use worldwide for nearly half a century. Production of this type of flowmeter began in China in the 1960s, and now a full range of such instruments is available. It takes advantage of the fact that the rotational angular velocity of the impeller placed in the fluid is proportional to the fluid flow rate; by measuring the speed of rotation of the impeller, it is possible to determine the volume flow rate through the pipe. It is a highly accurate meter that is well-developed among flow measurement instruments today. A turbine flowmeter consists of a turbine flow sensor and a flow display instrument, and it is capable of measuring both instantaneous flow rate and cumulative flow volume. The sensor outputs a pulse frequency signal that is proportional to the flow rate; this signal is transmitted over transmission lines to a device located away from the meter, facilitating accumulation and display. Furthermore, the pulse frequency signal output by the sensor can be used independently with a computer; the computer can take over the function of the flow display instrument to perform density or temperature/pressure compensation, thereby displaying the mass flow rate or gas volume flow rate. Instruments of this type are suitable for measuring the total volume of fluids. Today, turbine flowmeters are widely used in various fields such as petroleum, chemical industry, scientific research, national defense, and metrology. 3. Structure of the turbine flow sensor (1) Components of the turbine flow sensor As mentioned earlier, the structure of a gas turbine flow meter sensor mainly consists of an instrument housing, a guide vane, an impeller (turbine), bearings, and a signal detection amplifier. As shown in the figure below, (2) the functions of various components in the flow meter: 1) Instrument housing – The instrument housing is generally made of non-magnetic stainless steel or cemented carbide; for large-diameter sensors, a composite structure using carbon steel and stainless steel can also be used. The housing is the main component of the sensor; it serves to withstand the pressure of the fluid being measured, to hold the sensing elements in place, and to connect the pipes. Inside the housing are found guides, impellers, shafts, and bearings, while a signal detection amplifier is installed on the outer wall of the housing. 2) The guide vanes are usually made of non-magnetic stainless steel or hard aluminum; they are installed at the inlet and outlet of the sensor to guide and straighten the flow of fluid as well as to support the impeller, thereby preventing disturbances in the fluid from affecting the impeller. 3) The turbine, also known as the impeller, is generally made of highly magnetic materials such as 2Cr13 or Cr17Ni2; it serves as the sensing element of the sensor. Its function is to convert the kinetic energy of a fluid into mechanical energy. Impellers come in various types such as straight-plate blades, spiral blades, and T-shaped blades; a porous shroud ring filled with numerous magnetic guides can also be used to increase the rotation frequency of turbines with a certain number of blades. 4) The shafts and bearings are usually made of stainless steel (such as 2Cr13, 4Cr13, Cr17Ni2, or 1Cr18Ni9Ti, etc.) or cemented carbide; they form a pair of moving pairs that support and enable the impeller to rotate freely. It needs to have sufficient stiffness, strength, hardness, wear resistance, corrosion resistance, and so on. It determines the reliability and service life of the sensor. Sensor failure is usually caused by the shaft and bearings; therefore, the design of the sensor, the choice of materials, and maintenance are important considerations. 5) Signal detection amplifiers: The commonly used signal detection amplifiers in China are generally of the variable reluctance type; they consist of magnets, magnetic conductive rods, coils, and so on. Its function is to convert the mechanical rotation signal of the turbine into an electrical pulse signal for output. Due to the magnetic drag torque generated by the attraction of the magnets to the blades made of highly magnetic materials, in the case of small-diameter sensors at low flow rates, this magnetic drag torque becomes the dominant factor among all the torque types. For this reason, magnets are available in two sizes; smaller sizes are used for small-diameter sensors in order to reduce the magnetic drag torque. Generally, the signal generated by the coil is weak, so thousands of amplifiers are used to amplify it and shape it into electrical pulse signals with larger amplitudes. When the RMS value of the coil’s output signal is above 10 mV, a flow computer can be used directly. For more information, please visit the company’s official website at http://www.yb1518.com/. Please keep this link when reproducing the content! http://www.yb1518.com/UploadFiles/2012717173158206.jpg