The problem of creating effective structures that ensure mutual rotation of the rotor and stator of an electric generator. The wide practical application of counter-rotor wind-electric generators, which provide a significant increase in specific power, is hindered by the disadvantages and low reliability of existing systems for removing electric energy from the windings of a rotating counter-rotor, due to the dry friction mode. It is possible to increase the reliability of the contact removal of electrical energy from the counter rotor (rotating stator) by replacing solid brushes with liquid metal contact groups, which will lead to a certain increase in the resistivity of the contact group, compensated by the contact area of the liquid metal with the contact ring. It is most advisable to use liquid metal contact groups based on gallium, which will raise the permissible temperature limit of operation by about 2 times compared to the achieved level to 275 °C and, thereby, additionally raise the specific power of the electric generator.

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possibility possibility possibility devising it;Since the early 1970s the N. D. Kuznetsova Samara Scientific and Technical Complex Joint-Stock Company (N. D. Kuznetsova STNK AO) has been developing aircraft-type gas turbine engines (GTE) for the gas industry. Already in the late 1960s Academician N. D. Kuznetsov suggested that aircraft GTEs, after the end of their service life in aircraft, be used in various kinds of power installations on the ground on condition that the working temperature of the gases ahead of the turbine (the basic parameter determining the reliability and life of GTEs) be 150-200~ lower than in aircraft. This makes it possible to extend the life of engines on the ground by ten thousands of hours. It was found, moreover, that engines designed for work on the ground can use up to 70% of the parts and assemblies of aircraft engines, and that greatly reduces labor requirements and production costs of these engines. On the order of the Ministry of the Gas Industry the first gas-turbine engine (NK-12ST) was designed on the basis of the NK-12S turboprop aircraft engine used in the Tu-95, Tu-ll4, An-22 Antei aircraft, and it has been in operation since the end of 1974 in GPA-Ts-6,3 gas-pumping planm (GPP). At present these engines operate in 117 compressor stations in 852 GPPs. Most of the NK-12ST engines operated for about 600,000 h without repair.During the stages of design and operation of these engines the main postulates concerning the conversion of aircraft engines into various GTEs for the economy were formulated: high level of thermodynamic and gas-dynamic parameters; high technical level of design, enduring the building of GTE with large power, great reliability, and long life, and with small weight and overall dimensions of the assemblies; high level of production technology ensuring stability and good quality of production with high coefficient of metal utilization, lowering of metal content, reduced laboriousness, and production costs of the engines; possibility of using aircraft engines as gas generators of GTEs after they had been modified under test and operating conditions in aircraft; possibility of transporting them by helicopter to badly accessible regions, modular design; simplicity of operation of GTEs and no need of change of the external operating conditions; short time of starting and of attaining the nominal regime at low temperatures of the environment; of rapid assembly and start of the engine; of unification of engines for different purposes; of independent laboratory tests of separate assemblies of the engine so as to reduce time and costs of possibility of high-quality repair of engines under shop conditions. The conversion of aircraft engines into gas-turbine" installations for driving boosters of GPPs of electric power generators was carried out with a view to the following requirements: to ensure maximal possible efficiency of the power plant; trouble-free operation and longer life than in the basic engine; maximal ease of operation at gas-pumping stations and in pow...

Owing to the proved advantages of the Jet method of ventilation of open-cut mines, machlne-buildlng institutes are at present planning ventilators based on alrscrews.Thus we are faced with the problem of using various designs to improve the aerodynamic characteristics of the ventilation jets created by airscrew ventilators.These design features include, in particular, annular nozzles.In research on the operation of airscrews in nozzles, estimates were given of the influence of the nozzles on the draft of the airscrew, the power expended by it, and the efficiency of the system; no consideration was given to their influence on the parameters of the free jet.In particular, these investigations established that the draft of the system airscrew-plus-nozzle can be increased by 26.2% for the same expended power as when working without the nozzle [I]. A study of the influence of the nozzles on the jet parameters is undoubtedly of practical interest, because the efficiency of the jet is ultimately estimated in terms of the momentum of the entrained air masses.The influence of nozzles on the parameters of a free jet created by an alrscrew was first studied by us in [2]. We found that very simply shaped nozzles with large radial gaps always impair the aerodynamic parameters of the jet and are not advisable.In this article we give the results of an investigation of the effect of shaped nozzles with annular cross section on the parameters of the jet created by an airscrew.We used a jet test rig, observing the conditions of hydrodynamic similarity [3].We tested nozzles with annular radii of r a = 1.15R (R = radius of airscrew), with ra = 0.40R, and a cylindrical nozzle (Fig. i).In all the experiments the alrscrew was placed at the center of the cylindrical part of the nozzle, the length of which was I = 0.SR.The gap between the tips of the blades and the walls of the duct was 0.9% of the alrscrew diameter (relative gap 0.021).Jets created by isolated alrscrews and by alrscrews with nozzles were investigated in the self-modeling region for Reynolds numbers of (0.66-1.25).10 s, which were calculated from the expressionwhere B0.Ts is the width of the airscrew blades at a radius of 0.75R, R is the radius of the airscrew, ~ is the angular velocity of the alrscrew, and ~ is the kinematic viscosity of air.Institute of Mining, Ministry of Ferrous Metallurgy, Sverdlovsk.