How to Build a model of Magnetohydrodynamic Generator (MHD)

model of a Magnetohydrodynamic Generator

The magnetohydrodynamic generator (MHD) transforms energy into electricity directly. It has no moving parts at all. The working media in this generator is the hot plasma - it is the moving conductor. To generate electric current the plasma should go through a magnetic field, and this fields separates negatively charged electrons and positively charged ions by directing them into different trajectories. Positively charged ions go to the cathode, and negatively charged ones go to the anode, therefore there will be produced electric current.

To build this model we need ten horseshoe magnets, put them together with the poles in the same direction. In the middle magnets are fixed with two aluminium plates. This plates are connected together in the middle and at the ends with bolts and nuts. The width of this plates is about 50 mm, the thickness is 1..2 mm. Bend both ends of this plates for 90 degree and insert them into the laboratory support stand as shown in Figure.

Two copper plates are used in this installation as electrodes, each plate with length of 300 mm, width of 20 mm and thickness of 2 mm. The upper ends of this plates is bent at right angles, the plates are installed in the support stand. The ammeter is connected to the terminals of the plates.

As a gas burner can be used a Bunsen burner or similar burner that produces high-temperature vertical flame.

Install electrodes between the poles of the horseshoe magnets and keep the distance between this two electrodes of 1..2 mm to do the magnetic field lines be parallel to the plane of the electrodes. Ignite the burner and get a blue (hot) flame, put the burner under the electrodes (under the gap between them). The needle of the ammeter will slowly moving from zero to 0.15 mA. The current will depend on the strength of the magnetic field. A more powerful magnetic field will produces stronger currents.

How it works. The burner flame is a low-temperature plasma that contains positive and negative ions of air and combustion gases. Ions moving upwards and crossing the magnetic field lines at right angle. Every ion in the magnetic field experiencing the Lorentz force that changes the ions trajectory towards an electrode. As a result the positive ions gather at the cathode, and the negative ions gather at the anode. Because the electrodes charged with different charges (positive and negative), this effect will produce the Electromotive Force.