Numerical Modeling of a Fluidic Actuator dedicated to Flow Control on an Axial Compressor
Creators: name:  C. RANNOU 
name:   A. DAZIN 
name:   J. MARTY 
name:   G. TANGUY 
name:   L. CASTILLON 
name:   J. DELVA 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: FLOW CONTROL
AEROSPACE

description: The operating range of axial compressors can be limited by the presence of unstable flow phenomena such as rotating stall, which can severely reduce the surge margin of the engine. These phenomena prevent the compressor to reach high-pressure ratio, and often to obtain better efficiency. They are thus one of the main limitations of jet engines performances [1]. To push the stability limit of the compression machines and improve the Surge Margin, recent studies have shown the benefit of active control or passive control like casing treatments [2] [3]. More recently, one of the promising ways is to inject a small amount of flow at blade tip to alter the physical mechanism of the stall onset. Using active flow control systems, which can easily be turned off and on, is thus a very attractive alternative [4]. Before including control device in a real compressor configuration, investigations on CFD strategies are required to correctly capture the effects of the control system, due to the complexity of the flows involved and the size and geometric complexity of the device. As the final configuration (active flow control in a compressor) is the single stage compressor CME2, located at the Lille Laboratory of Fluid Mechanics (LMFL) [4], the injector device must be studied in similar conditions. Thus, the test bench dedicated to fluid actuator characterization located at ONERA Lille is used for CFD validation. The present study aims at determining a methodology taking account computational domain, mesh, numerical methods, and turbulence modeling. The goal is to optimally capture the behavior of internal flows within the control device consisting in an isolated fluidic actuator on a flat plate, blowing air. As the actuator geometry corresponds to the ones located on the CME2 test bench, numerical set up is characterized to be similar to the experimental conditions ensuring the same actuator mass flow rate and boundary conditions. Another operating condition consists in a jet in free flow configuration, i.e. without boundary layer over the flat plate. This paper is presenting a first research focusing on different types of mesh such as structured, unstructured, and hybrid mesh. Mesh convergence study is carried out for each mesh strategy with specific refinement. Reynolds Averaged Navier-Stokes (RANS) simulations are performed with CFD elsA code, with the same boundary conditions. Then, an analysis on turbulence model effect is also provided, by assessing different models such as Spalart-Allmaras, k-l, k-?, and k-? turbulence models to determine the best results with acceptable convergence. Results of the simulation are compared with those of injector characterization experimental tests obtained on the ONERA test bench, and representative of the case of the CME2. Satisfying agreements between numerical and experimental data are provided with similar flow behavior. In addition, this paper presents a parametric study on the effect of the mesh on the numerical flow fields in the case of a jet blowing in a boundary layer (case corresponding to the final application) and a jet blowing in free flow. These simulations permit to investigate different mesh strategies and the effect on the flow behavior.