DEVELOPMENT HISTORY AND PROSPECTIVE APPLICATION FIELDS OF SOLID LUBRICATION COATINGS FOR THE GAS-DYNAMIC FOIL BEATINGS OF HIGH-SPEED ELECTRIC TURBO MACHINES

Abstract

High-speed electrical turbo machines (ETMs) with rotor speeds of tens or hundreds of thousands rpm are currently the key functional component of prospective microturbine-based power installations for small-scale distributed power generation systems, for autonomous power supply, as well as for high-speed centrifugal compressors and air blowers. Practical implementation of such ETMs has become possible due to development of contactless support systems with gaseous lubrication, namely, gas-dynamic foil bearings (GDFBs), application of which makes it possible to do away with oil lubrication and cooling systems. In addition, GDFBs remain operational in wide ranges of temperatures and external heat inleaks; they also feature high damping properties and resistance to vibration. The required reliability and lifespan of GDFBs are achieved owing to the properties and serviceability of solid lubrication coatings (SLCs) applied to the foil bearing surfaces. The main purpose of SLC is "lubrication" of the bearing at the friction pair contact operation stages during startups and shutdowns in transient and emergency modes of ETM operation. SLCs shall have high adhesion to the metal base, high thermal and temperature resistance, low wear and friction coefficient, and good, , running-in ability. The development history of SLCs for GDFBs in the former Soviet Union is reviewed. Special attention is given to investigations aimed at putting in commercial use the AIS-2 compound. This compound, which is based on fluoroplastic and polyimide, was developed in the 1990s at the Novocherkassk Works of Synthetic Products under the leadership of Cand. Chem. Sci. G.E. Andreychikova. The article describes the approach to designing, selecting the components, thickness and thermal treatment conditions in forming the AIS-2 compound. The operating temperature of such coating does not exceed 300°С, which is obviously insufficient at present. The article outlines the plans of works aimed at developing new high-temperature SLCs AIS-3 and AIS-4 with operating temperatures up to 500°С, which are supposed to be carried out at the laboratory of the Moscow Power Engineering Institute National Research University's Department for Electrical Systems of Autonomous Facilities and Electric Vehicles.