# Aerodynamic and Structural Characteristics of a Centrifugal Compressor Impeller
## 1 Introduction  
Impellers are required to be designed to withstand the centrifugal force due to the rotation of rotor assemblies and the pressure forces due to the three-dimensional viscous fluid flow inside blade channels [1; 2]. Both the inertial forces due to rotation and hydrodynamic forces due to the flow result in stress acting on the impeller blade surfaces. Currently, power cycle systems demand higher pressurizing components with a wider operating range. Moreover, impeller with reduced weight can operate at high speed with lesser input power. Designing an impeller to meet such prerequisites with reliability is a challenging task and requires a coupled fluid-structure interaction analysis. The centrifugal and Coriolis forces generated in the centrifugal compressor impeller can be determined using Computational Fluid Dynamics (CFD) analysis, and the stresses acting on the impeller can be determined using the Fluid-Structure Interaction (FSI) analysis. The stress values obtained from the analysis are then applied to perform the pre-stressed analysis.  
The FSI analyzes the behavior of the structure under the action of the flow field, and it can be one-way or two-way depending on the transfer of the analysis results. In the one-way FSI, the CFD results are transferred to the structural analysis by one-way coupling, while in two-way FSI, the deformations in the structure obtained from the transfer of the CFD results are fed back to the CFD environment, to determine the deviation in the flow created as a result of the structural deformation [3]. Several researchers [4; 5; 6; 7; 8] studied the effect of FSI on radial forces, pressure distribution, equivalent stress, and rotor deflection in a centrifugal compressor and pump. [PERSON] et al. [9] suggested that the complete compressor performance analysis should involve both fluid and solid mechanics and found that the fluid pressure influences the von Mises stress significantly. [PERSON] et al. [10] quantitatively analyzed the distribution of stress and deformation in the impeller of the multistagepump. [PERSON] et al. [11] investigated a mixed-flow pump with an unshrouded impeller by one-way coupled FSI, and the distribution of stress on the impeller was obtained. [PERSON] et al. [12] concluded that to ensure the safe operation of a rotating structure for every flow rate, the analysis of stress and deformation on the impeller in the unstable operation region needs to be solved by the consideration of FSI. [PERSON] and [PERSON] [13] pointed out that structural safety needs to be evaluated because the impeller receives fluid pressure load and centrifugal force during the operation.  
In the system of FSI, there are some interactions between two different physical fields on the coupling interface. Field force, which interacts on the structure surface, has an influence on the movement of the structure, and the deformation of the structure also changes the fluid calculation area and the boundary conditions, which affect the flow field [14]. Thus, it becomes necessary to analyze the effects of the impeller blade shape on its aerodynamic performance and structural safety by using FSI. To evaluate the structural integrity and stability of the impeller during the lifespan, a fluid-solid interaction is required to assess the stresses. Similarly, to acquire a superior design, a reasonable compromise between the aerodynamic, stress, and rotor dynamics is needs to be found. Depending on the mechanical design criteria, the model with the lowest overall von Mises nodal stress has been sought to determine the best impeller design [5; 15]. The structural part deforms due to the pressure or temperature load from the fluid domain. One-way coupled FSI analysis is performed using the pressure load results from CFD. The pressure load is imposed in carrying out the pre-stressed structural analysis. The present study focuses on the flow characteristics, the aerodynamic performance analysis, and the structural safety of the centrifugal compressor impeller.