Abstract
The measurement of flow velocities inside metal melts is particularly challenging. Due to the high temperatures of the melts it is impossible to employ measurement techniques that require either mechanical contact with the melt or are only adaptable to translucent fluids. In the past years a number of electromagnetic techniques have been developed that allows a contact-free measurement of volume flows. One of these techniques is the so-called Lorentz Force Velocimetry (LFV) in which the metal flow is exposed to an external, permanent magnetic field. The interaction between the metal and the magnet not only leads to a force on the fluid, but also on the magnet. The force can be measured and is proportional to the velocity of the melt. Moreover, by using a small permanent magnet it is possible to resolve spatial structures inside the flow. We will demonstrate this using a model experiment that has been investigated with different reference techniques previously. The experimental setup is a cylindrical vessel filled with a eutectic alloy which is liquid at room temperature. The liquid metal can be set into motion by means of a propeller at the top of the liquid. Depending on the direction of rotation of the propeller, the flow inside the vessel takes on different states. Beside the vessel, we place a Lorentz Force Flowmeter (LFF) equipped with a small permanent magnet. By measuring the force on the magnet at different positions and different rotation speeds, we demonstrate that we can qualitatively and quantitatively reconstruct the flow field inside the vessel.
Highlights
Industrial flows like metal melts or glass melts are typically chemically aggressive and very hot
The measurement of flow velocities inside these fluids has been a challenge until recently, before several flow meters have been developed that use electromagnetic techniques to determine the volume flux without or only indirect contact to the fluid [1,2,3,4,5,6]. One of these techniques is Lorentz Force Velocimetry (LFV, [4]), a non-contact electromagnetic method that exposes the flow to a magnetic field and uses the resulting force on the magnet to determine the velocity of the flow
It is expected that the force on the magnet should increase with increasing rotation speed of the propeller, i.e. with an increased flow velocity inside the vessel [4]
Summary
Industrial flows like metal melts or glass melts are typically chemically aggressive and very hot. The measurement of flow velocities inside these fluids has been a challenge until recently, before several flow meters have been developed that use electromagnetic techniques to determine the volume flux without or only indirect contact to the fluid [1,2,3,4,5,6] One of these techniques is Lorentz Force Velocimetry (LFV, [4]), a non-contact electromagnetic method that exposes the flow to a magnetic field and uses the resulting force on the magnet to determine the velocity of the flow. LFV has been applied successfully to industrial type flows and to electrolytes in the laboratory [7,8,9] All of these measurements have been volume flux measurement. The sensor that utilizes the small magnet is called Local Lorentz Force Flowmeter, in short L2F2
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