Axial Flow Compressor Real-Time Tip Clearance Analysis and Experimental Verification

Abstract

The tip clearance of the compressor has always been a key part in both the design and operation of gas turbine. Surge margin and aerodynamic performance of the compressor will be affected if the tip clearance is too large, while risk of rubbing between the blades and casing will arise if the tip clearance is too small. Generally speaking, the calculation and analysis of tip clearance under stable design condition is relatively easy, because the metal temperature field of both rotor and stator components that significantly affect the tip clearance is in stable condition at that time. However, the transient tip clearance under start-up and shut-down condition is difficult to be calculated and analyzed, due to the fact that both the aerodynamic parameters and metal temperature field are instable, and complicated heat-exchange occurs between the metal components and gas. In this paper, the transient deformation of both rotor and stator components of compressor of a certain gas turbine is analyzed in detail by using thermo-solid coupling analysis technology, finally obtained real-time tip clearance. The non-contact measurement technology is used to measure the tip clearance during operation of the unit. The experimental result indicates that the real-time tip clearance value obtained by the calculation method in the paper is in a very good agreement with the measured value. In addition, both the analysis and experimental results show that the moment of smallest tip clearance usually happens at shut-down progress and the influence of tip clearance must be considered when designing unit’s running curve.