Experimental studies of high-speed cryogenic magnetic fluid seals

A possibility for the practical application of magnetic fluid in magnetic fluid seals for sealing high-vacuum chambers around a powerful cold rotor with as high as 60 m/s rotation velocity has been experimentally studied. The influence of geometric parameters of the magnetic system and of the physical properties of magnetic fluids on the efficiency of the seal operation has been defined in the temperature range from -50 to +150°C. The development of powerful cryoturbogenerators (CTG) is greatly dependent on the successive realization of hyper- or superconducting inductors (rotors), and minimization of the external heat fluxes to maintain the required temperature there. The heat insulation is mainly produced by high-vacuum, which in most CTG is made as a sealed chamber rotating together with the rotor. In any closed chamber, however, and especially in a chamber with a great number of welds and other connections, which is typical for any real CTG rotor, after switching off the pumping system the pressure gradually increases due to both the gas desorption from the surface of components and the external gas diffusion. Therefore active vacuum control cannot be performed without stopping the rotor.