Scope of this thesis is CFD simulation of fluid flow in a centrifugal compressor, which is an integral part of jet engines. When comparing centrifugal compressors with axial ones, one of the significant differences is the higher compression ratio. Computational fluid dynamics (CFD) is a frequently used methodology in engineering practice for the modelling of turbomachines, as an alternative or amendment to analytical and experimental methods. Computational fluid dynamics is based on the numerical solution of a system of equations in order to understand fluid flow in space and time, whilst the solutions as a result of the simulation allow the quantification of the flow in terms of forces, moments and performance of the observed system. The main objective of this thesis is to investigate the working area of ​​a centrifugal compressor, i.e. its behavior in nominal and non-nominal operating points using CFD software foam-extend. The challenge of simulating turbomachines lies in the complexity of the model geometry, which entails high demands on computer resources and the duration of the simulation, i.e. calculation. Therefore, in order to save as much time as possible, it is necessary to pay special attention to choosing a computational domain and generating a mesh for the chosen domain. This thesis first presents the theoretical basis for simulating the flow in a centrifugal compressor under conditions of compressible turbulent flow, followed by setting up the simulation which includes determining the computational domain, creating the mesh, setting the initial and boundary conditions, and finally starting the simulation. It should be emphasized that using the iteration method, the pressure difference at the inlet and outlet of the system is progressively changed until the required mass flow rate is reached. Finally, the results were compared with the results of Matej Čorak, which were obtained by simulating the flow through a single blade passage of a centrifugal compressor.