Numerical and Experimental Investigation of Inter-Stage Bleed in Axial Compressors of Industrial Gas Turbine

Abstract

Abstract. To provide a practical design basis for the compressor bleed system design, this paper uses numerical simulation and rig tests to evaluate the influence of bleed system design parameters on bleed performance. The research focuses on a multistage axial compressor of a real industrial gas turbine. Through numerical simulations, the complex three-dimensional (3D) flow in the bleed system is analyzed. It is found that at high bleed rates—specifically 15.2% during the startup process of the distributed energy gas turbine, which is designed for antisurge protection—the pressure loss is mainly in the bleed annular cavity and off-take duct, accounting for over 80% of the total loss. The bleed annular cavity design affects the jet in the cavity and flow loss in the off-take duct. There is an optimal axial position for the off-take duct inlet (OTDI) to minimize pressure loss. When the high-speed jet from the bleed slot (BST) outlet faces the off-take duct inlet directly, the circumferential static pressure nonuniformity reaches its maximum. At a high bleed rate of 15.2%, the static pressure nonuniformity at the throat increases by nearly 40% compared to the optimal axial position, revealing the sensitivity of the parametric design of bleed systems to the circumferential nonuniformity of the flow field. The bleed annular cavity impacts the circumferential uniformity of the mainstream flow field differently under various bleed system designs. A well-designed bleed system can prevent nonuniform interstage bleed from causing significant unit performance degradation; however, it still affects the unit's stall or surge characteristics, specifically altering the location where rotational stall occurs and the stall frequency in the mainstream flow field. This highlights the need to balance antisurge functionality with compressor spatial constraints during design, guiding optimized layouts that mitigate flow instability risks.