Test unit for gas dynamic tests of low consumption stages of centrifugal compressors

Abstract

An experimental test unit is created for studying low-consumption stages of centrifugal compressors with a rotor magnetic suspension system (MSS) and a torsional moment transducer. In addition, this unit makes it possible to perform MSS studies in the area of functional construction, analysis and synthesis of dynamic characteristics of the rotor-MSS system. The rotation speed of the model rotor is 1000-25000 rpm. In order to reduce the loss of power in bearings, a rotor magnetic suspension device is used, developed and manufactured in the V. B. Shnepp Turbocompressor Research Institute. The torsional moment transducer, installed in a coupling between the set-up gear and the bearing support, provides the possibility of measuring power in the impeller shaft with compression of the working gas.In view of the expansion of the field of using centrifugal compressors and, specifically, use of compressors with low productivity (Φ 0 < 0.025), a requirement arises in experimental studies for low consumption stages and the development of new procedures for their design and planning. As a rule, creation of new design procedures in centrifugal compressor construction is based on reliable experimental data.Using a thermal balance method in order to determine stage characteristics, it is necessary to consider thermal losses of the capacity, losses in friction of the air impeller and in flow through compaction, and also the error in measuring temperature and pressure. It is impossible to estimate heat losses precisely, and in order to reduce errors in temperature and pressure measurement expensive highly accurate transducers and secondary measuring equipment are required. Therefore, it has been decided in order to determine stage characteristics to use a torsional moment transducer that makes it possible to measure the moment and power in a shaft. However, the power used by a low-consumption stage, commensurate with the power loss in oil bearings, is the same as in magnetic bearings and these losses are small.Taking account of these factors, the problem was set of creating an experimental test unit for studying the low-consumption stages of centrifugal compressors with a magnetic suspension system (MSS) for the rotor and a torsional moment transducer, and also for studying the magnetic suspension system with the aim of functional construction, analysis and synthesis of the dynamic characteristics of the rotor-MSS system.The following conditions were taken into account in developing the system: • the working gas is air;• the circuit is open;