اندازه گیری جریان سیال

اندازه گیری جریان جامد

جریان مایع از میان مسیر با سطح مقطع متغیر

اندازه گیری جریان سیال بر مبنای اختلاف فشار

سنسورهای اندازه گیری جریان سیال بر مبنای اختلاف فشار

لوله پیتو

Rota meter

Rota meter

پل ماکسول به عنوان سنسورثانویه

Ultrasonic flow meter

Ultrasonic Doppler flow meter

Ultrasonic Doppler flow meter

Drag force flow meter

Turbine flow meter

Mass flow meter A critical feature of modern airplanes is the ability to measure the fuel consumption with great accuracy. Nothing could be worse than running out of fuel on a transatlantic flight a couple of kilometers short of the airport. Now it is not the volume of fuel that is important, but the mass, since energy is directly proportional to mass. Most measurements of mass flow rates are based upon Where ρ is the density and is the volume flow rate. This means that we must know the density of the fuel – a quantity that varies with temperature. To avoid this, direct mass flow measurements are based upon the moment of momentum relationship where T=torque, V are the tangential velocities, r are radii, and the subscripts i and e represent inlet and exit velocities.

Mass flow meter A fluid flows from left to right while the element is being rotated by an electric motor. The flow comes in with no tangential velocity (either it has none to begin with or passes through a straightened before reaching the element). All of the fluid passes through the element and if the element is long enough leaves with Ve=r ω, thus T=(dm/dt)r2 ω . Since r and ω are constant, the torque T is a direct and linear measure of the mass flow rate.

Impeller-Turbine Flow meter The impeller-turbine-type mass flow meter uses two rotating elements in the fluid stream, an impeller and a turbine. Both elements contain channels through which the fluid flows. The impeller is driven at a constant speed by a synchronous motor through a magnetic coupling and imparts an angular velocity to the fluid as it flows through the meter. The turbine located downstream of the impeller removes all angular momentum from the fluid and thus receives a torque proportional to the angular momentum. This turbine is restrained by a spring that deflects through an angle that is proportional to the torque exerted upon it by the fluid, thus giving a measure of mass flow.

Twin-Turbine Flow meter In this instrument, two turbines are mounted on a common Shaft. They are connected with a calibrated torsion member. A reluctance-type pickup coil is mounted over each turbine, and a strong magnet is located in each turbine within the twin-turbine assembly. Each turbine is designed with a different blade angle; therefore, there is a tendency for the turbines to turn at different angular velocities. However, because the motion of the turbines is restricted by the coupling torsion member, the entire assembly rotates in unison at some average velocity, and an angular phase shift is developed between the two turbines. This angle is a direct function of the angular momentum of the fluid. Angular momentum can be measured by torque, and angular momentum is a function of mass flow. In the twin-turbine assembly, the turbines are not restrained by a spring, but the torsion member that holds them together is twisted. This torsion member has a well established torsion-spring rate (ft-lbf/rad). Therefore, the angle developed between the two turbines is a direct function of the twist or torque exerted by the system.

Rotor torque mass flow meter

With mass flow the tubes twist slightly. Coriolis mass flow meter Rotation without mass flow. With mass flow the tubes twist slightly. A rotating mass flow meter as illustration of the operating principle. The animations on the right do not represent an actually existing Coriolis flow meter design. The purpose of the animations is to illustrate the operating principle, and to show the connection with rotation. Fluid is being pumped through the mass flow meter. When there is mass flow, the tube twists slightly. The arm through which fluid flows away from the axis of rotation must exert a force on the fluid, to increase its angular momentum, so it bends backwards. The arm through which fluid is pushed back to the axis of rotation must exert a force on the fluid to decrease the fluid's angular momentum again, hence that arm will bend forward. In other words, the inlet arm (containing an outwards directed flow), is lagging behind the overall rotation, the part which in rest is parallel to the axis is now skewed, and the outlet arm (containing an inwards directed flow) leads the overall rotaton.

The principle design of a curved tube mass flow meter. The vibration pattern during no-flow. The vibration pattern with mass flow. The principle design of a curved tube mass flow meter. The animation on the right represents how curved tube mass flow meters are designed. The fluid is led through two parallel tubes. An actuator (not shown) induces equal counter vibrations on the sections parallel to the axis, to make the measuring device less sensitive to outside vibrations. The actual frequency of the vibration depends on the size of the mass flow meter, and ranges from 80 to 1000 Hz. The amplitude of the vibration is too small to be seen, but it can be felt by touch. When no fluid is flowing, the motion of the two tubes is symmetrical, as shown in the left animation. The animation on the right illustrates what happens during mass flow: some twisting of the tubes. The arm carrying the flow away from the axis of rotation must exert a force on the fluid to accelerate the flowing mass to the vibrating speed of the tubes at the outside (increase of absolute angular momentum), so it is lagging behind the overall vibration. The arm through which fluid is pushed back towards the axis of movement must exert a force on the fluid to decrease the fluid's absolute angular speed (angular momentum) again, hence that arm leads the overall vibration.The inlet arm and the outlet arm vibrate with the same frequency as the overall vibration, but when there is mass flow the two vibrations are out of sync: the inlet arm is behind, the outlet arm is ahead. The two vibrations are shifted in phase with respect to each other, and the degree of phase-shift is a measure for the amount of mass that is flowing through the tubes.

Laser Doppler anemometer

Hot wire anemometer

Electromagnetic flow meter