The elbow flowmeter belongs to the category of differential pressure flowmeters, and the elbow sensor uses the principle of fluid inertia to generate differential pressure. When the fluid passes through the elbow, the fluid constrained by the elbow tube is forced to make a similar circular motion. The centrifugal force generated when the fluid moves in a circular motion acts on both the inside and outside of the elbow so that the inside and outside of the elbow sensor are generated between both sides. A pressure difference, the pressure difference (that is, differential pressure) is related to the density of the fluid, is related to the average flow velocity of the fluid, and is related to the radius of curvature of the fluid as a circular motion. They follow the laws of Newton's laws of motion that must be observed for circular motion objects. The successful development of elbow flowmeter has solid theoretical research foundation and experimental research foundation. In theory, the main method is to directly solve the numerical solution of the differential equations of the fluid flowing through the elbow to fully reveal the flow law of the fluid flowing through the elbow. In the experimental research, there are a large number of experimental studies in the laboratory, and there are authoritative verifications of flow measurements in different media at the national traffic verification stations (Kaifeng large flow, Yantai steam, and Huayang natural gas). The verification of the type identification (opening and water) of the family shows that due to the diversion effect of the elbow, the fluid flowing through the elbow presents a very complicated flow state. The numerical solution of the Navier-Stokes differential equation (NS equation) can be animated to show that this flow state mainly includes the main flow along the main pipeline, the double spiral flow perpendicular to the main flow, and the outlet. The whirlpool and other subject matter have a strong regularity. According to the fact that the true viscous fluid passes through the inside and outside of the elbow, the pressure difference is proportional to the relationship, and it has a good correlation. According to dimensional analysis principle, the average flow velocity through the elbow and the pressure difference between the inside and outside of the elbow can be given by the following formula: The fluid flows through a pipe at a certain temperature and pressure, and when it passes through a turn, The fluid will do the corresponding circular rotary motion. According to the fluid forced swirling theory, the fluid in the pipe makes a circular motion similar to the solid in the space state, so the fluid will inevitably produce the inertia centrifugal force, the size of the centrifugal force and the fluid flow velocity, the fluid density and the circular motion The radius of curvature (that is, the radius of curvature of the bend sensor) is related to other factors. Since the radius of curvature of the elbow sensor is known, the density of the fluid flowing through the elbow sensor can be accurately obtained by measuring the parameters of the fluid temperature, pressure, etc., using a computer of the host computer, so that the centrifugal force generated on the elbow sensor is generated. The size is simply a function of the fluid velocity. As long as the size of the centrifugal force is measured, the flow rate of the fluid in the pipe can be measured. The flow rate is multiplied by the cross-sectional area of ​​the pipe and the density of the fluid. The flow rate of the fluid can be calculated and determined. The calculation relationship is as follows: Equation 1 gives a functional expression of the average flow velocity and the differential pressure value of the flow through the elbow: V = a [(P1-P2) / Ï] β -------- 1 where : V --- average flow velocity of the fluid; a --- comprehensive flow coefficient, a = f (bending ratio of bends, Reynolds number, dynamic viscosity of the medium, roughness of the pipe, etc.), among which the most important effect is the ratio of the bend diameter Important: P1-P2----- pressure difference between the inside and outside of the pipe bend; Ï----density of the fluid; β----index; Calculate the average flow velocity V to obtain the functional expression of the calculated flow rate. : Q=S*V*Ï-----------2 Where: S----cross-sectional area of ​​the elbow; V--average flow rate of the fluid; applicable range 1. nominal diameter: 25mm≤DN≤2000mm 2. Nominal pressure: PN≤10MPa 3. Medium temperature: t≤450°C (t>450°C when ordering) 4. Reynolds number range: ReD>104 5. Accuracy class: Level 1, Level 1.5 6, R/D≥1.25
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