Compressor surge based on a 1D-3D coupled method – Part 1: Method establishment

Abstract

Compressors are core components in gas turbines and turbocharged engines to feed air. No matter in axial compressors and centrifugal compressors, a fatal issue which can happen in the system is compressor surge, a violent flow oscillation throughout a compression system. Understanding internal flows of compressors in compressor surge is crucial to investigate surge precursors and post-surge behaviors. Aerodynamic behaviors of compressor surge are not only affected by compressors but also other parts in the system primarily including pipes, a plenum, and a throttle valve. It is necessary to look at compressor surge internal flows in the context of compressions systems. The purpose of this study is to establish a one-dimensional and three-dimensional (1D-3D) coupled method for simulating compressor surge in a compression system. The method can jointly solve one-dimensional flows through the piping, plenum, and valve and three-dimensional flows in the compressor. Compared with fully lumped parameter models, the 1D-3D coupled method can simulate overall responses of compressor surge without inputting compressor performance maps; furthermore, 3D flows can be obtained to reveal more details concerning compressor surge. In contrast with fully 3D simulations, the 1D-3D coupled method saves computational cost on the piping, plenum, and valve, which take large space of the system but are just dominated by 1D flows. Therefore, via the 1D-3D coupled method, compressor surge behaviors of a newly designed compressor can be evaluated swiftly once geometry models are given. The method is based on a combination of unsteady Reynolds-averaged Navier-Stokes simulations, the method of characteristics, and lumped parameter models. Boundary conditions and domain interfaces are carefully treated to reach a closed-form solution. A shock tube problem is modeled and simulated by the method to validate its implementation. 1D-3D coupled simulations are performed on the compression system of a centrifugal compressor, and the results are compared with experimental data. Typical phases of compressor surge are captured by the 1D-3D coupled simulation, and leading mode responses in spectrums are well reproduced by the method; however, the method fails to capture high-frequency modes and a quiet zone during a surge cycle, which are respectively attributed to rough temporal and turbulent resolutions and rotational speed variations during compressor surge. Improved identification of system parameters, finer temporal resolutions and the implementation of variable rotational speed are recommended for future developments of the method.