Numerical Simulation of the Flow Field in a High Speed Multistage Compressor: Study of the Time Discretization Sensitivity

Abstract

The following numerical investigations are performed in the frame of a research project that aims at a better understanding of the flow unsteadiness that develops in a multistage high-speed axial compressor. First, the paper presents a new version of the 3.5 stages high-speed axial compressor CREATE (Compresseur de Recherche pour l’Etude des effets Aérodynamiques et TEchnologiques), which has been designed by Snecma and is based at the LMFA (Laboratory for Fluid Mechanics and Acoustics) on a 2MW test rig. This paper is based on numerical results obtained with 3D steady and unsteady RANS computations using the CREATE configuration. The unsteady RANS simulations are carried out over the whole spatial and temporal periodicity of the compressor. The main numerical setup has been fixed according to the state of the art. Second, the effect of three different time discretizations on the flow field in CREATE is discussed. The global performance of the compressor is not significantly affected. However the change in the time discretization impacts the structure of the flow at specific locations. The main focus of this study lies on the transport of flow structures and the analysis of their interactions. A double modal decomposition method, which highlights the specific contribution of the interactions on the overall flow field, is applied for the study of the highly complex and unsteady flow field. It allows identifying which interactions are more sensitive to the change in the time discretization.

CFD Modelling of a Centrifugal Compressor with Experimental Validation through Radial Diffuser Static Pressure Measurement

“…Interface. Following [4,6,7,9,[15][16][17], the computational domain was partitioned into the stationary inlet, rotating impeller, and stationary diffuser with frozen rotor interfaces between adjacent domains. The domain partitioning is shown in Figure 5.…”

“…Centrifugal compressors are widely used in a range of applications including refrigeration and air conditioning, power generation, aeronautics, turbochargers, and the oil and gas industry; and their design is an important factor in the performance and efficiency of the systems in which they are incorporated. Thus the simulation of centrifugal compressors is becoming increasingly important and has been applied to investigate a range of phenomena such as noise generation [1,2], tip clearance [2,3], effect of volute and diffuser geometry [4,5], compressor performance [6][7][8], and the flow field through the compressor [9,10]. An important aspect of developing a numerical model is the validation stage, which usually involves a comparison with experimental data.…”

“…Out of the accumulation of a body of work, a number of common approaches have resulted in terms of CFD model settings with regard to turbulence models [11][12][13][14], interface settings [4,6,7,9,[15][16][17], and boundary conditions [7,11,18]. There are a number of turbulent models which can be applied in a RANS simulation.…”

Validation of a Radial Compressor CFD Analysis

“…In literature there are many numerical studies to simulate compressible flow in radial compressors. In the studies [1][2][3][4][5] the researchers investigated different CFD modeling settings about interfaces and boundary conditions to successfully model compressible flow in various types of high speed compressors. Liu and Hill [5] discussed different interface models that can be implemented to rotational and stationary parts of the turbo-compressor and pointed out that the results from circumferential averaging type interface approach were more similar to transient analysis than the frozen rotor interface for a vaned diffuser radial compressor.…”

Observations on Rotating Instabilities and Spike Type Stall Inception in a High-Speed Multistage Compressor

“…Consequently one temporal period corresponds to 1/16th of a rotor revolution. A profound knowledge-base has been acquired with CREATE for numerical and experimental methods aiming at flow field investigations in the high-speed multistage compressor environment [10][11][12][13]. Standard tip gap sizes are implemented compared to increased tip gaps in rotors 2 and 3 in the previous version of CREATE.…”