Авіаційно-космічна техніка та технологія (Dec 2018)
DIAGNOSTICS OF PRE-SURGE CONDITION OF THE AXIAL COMPRESSOR WITH THE ANNULAR GROOVES CASING TREATMENT
Abstract
Ensuring the gas-dynamic stability of gas turbine engine, still remains one of the actual problem of modern aircraft engine building. To date, a significant number of studies have been conducted. This studies are the foundation for different techniques of diagnosing the pre-surge condition condition. Also known that one of the ways to solve the problem of increasing gas-dynamic stability is the use of casing treatment. However, there are no clearly formulated techniques that allow diagnosing the surge line in an axial compressor with casing treatment. Consequently, the problem of their development is relevant. The paper addresses the results of experimental and computational studies of unsteady flows in an axial compressor with the casing treatment in the form of annular grooves. Specific features of the transition to the regime of rotating stall (with break of the compressor characteristic) by an axial compressor with the annular grooves are formulated. The temporary conditions are provided for the formation of the reliable diagnostic signal of the axial compressor pre-surge operating mode with the annular grooves casing treatment by stabilization of the partial rotating stall condition were displayed. Calculation techniques for estimating informative criteria for detecting of the compressor pre-surge condition were proposed. One of them is the appearance of a discrete component of the amplitude-frequency characteristic of the total pressure pulsations (in the direction of rotation of the rotor) in the cavity of the groove of the casing treatment located above the leading edge of the blades. This discrete component appears at the frequency of a single-zone rotating stall, so it can serve as a trigger pulse for surge prevention automatic control system. The second informative criterion is the appearance of the gradientless region in the distribution of pressure on the bounding wall of the airgas channel above the blade. The position of the gradientless section in the pressure distribution on the bounding wall of the airgas channel above the blade with respect to the meridional projection of the chord of the tip end of the blade has been determined experimentally and by calculation according to the developed technique. Comparison of the proposed mathematical models with experimental data was performed. Their qualitative and quantitative conformity to the experiment were shown.
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