MHD generator

MHD generatorMagnetohydrodynamic generator, or MHD generator, is a device for generating electric power. This installation transforms energy of a moving actuating medium into electric power.So what is an actuating medium?In this case this is a current-conducting medium. This can be a liquid metal, an electrolyte, or plasma. Movement of these media is characterized by magnetic hydrodynamics. So this is why the generator has such name. Its operating principle and design are relatively simple.The principle idea is to let the actuating medium pass through the channel in a magnetic field which is generated by an electromagnet. The medium moves at a high speed which can be supersonic. In this case the external magnetic field "sorts out" negatively charged electrons and positively charged ions of the actuating medium by directing them into different trajectories.Direction of force effect can be determined with the help of the left-hand rule. As a result positively charged ions settle on the cathode while negatively charged ones settle on the anode. Electromotive force occurs between electrodes since they acquire unlike charges. In this case electric current will flow through the conductor which connects electrodes.The generator has a nice feature as it does not have such moving parts as a rotor. Theoretically this allows to generate great power - i.e. of thousand megawatts. In general power is proportional to conductivity of the actuating medium, as well as to square values of its speed and magnetic field intensity.So why are such generators not used everywhere?Well, there are several unresolved issues in practice.First of all it is quite costly to create the actuating medium. It is difficult to use liquid metals as this method had not been recognized. But if we want to use gas then we have to heat it up to ionization temperature - and this is about 10 000 degrees Kelvin! We can introduce alkali metal additives such as potassium into gas stream. This will help to reduce temperature down to 2.5-3 thousand degrees Kelvin. However, it is not only costly to heat up gas to such temperature but it is also inefficient as certain parts of the generator cannot withstand such temperature. Thus the generator will not last long.All in all functional models of such generators do exist. There are combined installations which generate power. However, in order to use them widely we'll have to resolve certain issues. This area is actually researched nowadays - if we learn how ...

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