Influence of Liquid Viscosity on Performance of Turbine Flow Meters

Abstract: The information on the influence of liquid viscosity on the performance of turbine flowmeters is provided by excellent flowmeter and flowmeter manufacturers. 1 Principle structure and concept Turbine flowmeter uses the average flow rate of the impeller to feel the fluid in the suspended fluid to deduce the instantaneous flow and cumulative flow of the measured fluid. Generally, the impeller, the deflector, the magnetic steel, the induction coil, and the preamplifier are used. composed of other parts. eddy. More flowmeter manufacturers choose models and price quotations. You are welcome to inquire. The following is the details of the article on the influence of liquid viscosity on the performance of turbine flowmeters. 1 Principle structure and concept Turbine flowmeter uses the average flow rate of the impeller to feel the fluid in the suspended fluid to deduce the instantaneous flow and cumulative flow of the measured fluid. Generally, the impeller, the deflector, the magnetic steel, the induction coil, and the preamplifier are used. composed of other parts. The structure of the turbine flowmeter is shown in Figure 1. 1—impeller; 2—deflector; 3—*Magnetic steel; 4—induction coil; 5—preamp; 6—shell. Figure 1 Structure of turbine flowmeter (1) Fluid viscosity. Due to the internal magic friction when the fluid flows, the speed of each layer is different. There is a pair of equal and opposite forces on the contact surface of the adjacent layers. The faster flow layer drives the slower layer, so that the If the speed is accelerated, the slower layer retards the faster layer and decelerates it. This blocking force is called internal friction, and the fluid viscosity is a measure of internal friction and the ability of the fluid to resist deformation. The viscosity of various fluids varies. For general fluids, viscosity is a function of temperature and pressure. The viscosity mentioned in the text is the kinematic viscosity, the unit is cSt, 1cSt=10-6m2/s. (2) Coefficients. The meter coefficient K refers to the number of pulses sent by a unit volume of fluid through the flow meter, and the unit is L-1. The calculation formula is as follows: In the formula: Kij is the coefficient at the jth verification of the i-th verification point, L-1; Nij is The flowmeter at the j-th verification of the i-th verification point displays the number of pulses measured by the meter; Vij is the actual volume measured by the standard device during the j-th verification of the i-th verification point, L;βis the volume expansion coefficient of the verification liquid under the verification state; (θs)ij, (θm)ij is the liquid temperature at the standard device and the flow rate at the jth verification at the ith verification point, °C; κ is the compressibility of the verification liquid in the verification state; (ps)ij and (pm)ij are respectively the ith The liquid gauge pressure at the standard device and the flow rate at the j-th verification of the verification point, Pa; n is the number of verifications at each point; (Ki)max is the maximum value of Ki obtained by the flowmeter at the flow verification point; (Ki)min is The minimum value of Ki obtained by the flowmeter at the flow verification point. (3) Linearity. Under specified conditions, the percentage between the maximum deviation between the turbine flowmeter calibration curve and the fitted straight line and the full scale output is called linearity. The smaller the value, the better the linearity. The calculation formula is as follows: In the formula: E is the linearity of the flowmeter. 2 Testing equipment and conditions (1) Atmospheric pressure: 101818Pa. (2) Medium: aviation lubricating oil. (3) Verification device: standard device for aviation lubricating oil flow. (4) The instrument to be inspected: the model is LWGY-15A, the serial number is 0906280, and the manufacturer is Shanghai Ziyi Jiu Instrument. 3 Experimental data and analysis According to the above testing equipment and conditions, according to JJG1037—2008 'Verification Regulations for Turbine Flow Meters', 5 points are verified under four different viscosities, and each point is verified 3 times. The data obtained are shown in Table 1 to Table 4. The frequency, flow rate, temperature, coefficient in the data table All are the averages of 3 tests for each point. The linearity of the meter obtained from Table 1 is 8.9%, and the meter coefficient is 528.61L-1; the linearity of the meter obtained from Table 2 is 6.3%, and the meter coefficient is 553.89L-1; the linearity of the meter obtained from Table 3 is 2.6%, the meter The coefficient is 596.18L-1; the linearity of the instrument obtained from Table 4 is 2.2%, and the instrument coefficient is 622.44L-1. Table 1 Data when viscosity is 93.24cSt Table 2 Data when viscosity is 52.14cSt Table 3 Data when viscosity is 16.28cSt Table 4 Data when viscosity is 7.16cSt Because the fluid is viscous, oil is generated when it passes through the flow meter Viscous drag torque. It can be seen from Table 1 to Table 4 that the viscosity of lubricating oil is from 93.24cSt→52.14cSt→16.28cSt→When 7.16cSt changes, the coefficient of the turbine flowmeter (528.61L-1→553.89L-1→596.18L-1→622.44L-1), linearity (8.9%→6.3%→2.6%→2.2%) are gradually undergoing significant changes. When the viscosity of the flowmeter is up to 93.24cSt (Data Table 1), the linearity of the entire flowmeter is only 8.9%, and it cannot be used at all. To meet the requirements of use, only reduce the range. Through observation and calculation, it is found that only when the flow rate is 2.8990～4.1497m3/h, the linearity is (575.86-569.50)/(575.86+569.50)×100%=0.56% to meet JJG1037—The maximum error allowed by the 2008 'Verification Regulations for Turbine Flowmeters' is 1.0%, which means that this flowmeter is qualified only if it is used within the range of these two points. When the viscosity decreases to 7.16cSt, the linearity range becomes wider. When the flow rate is 1.0196～4.0465m3/h, the linearity is (631.96-620.88)/(631.96+620.88)×100%=0.88%, which fully complies with the maximum allowable error of the regulations.

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