Experimental And Numerical Investigation Of The Internal Flow In A High Speed Centrifugal Compressor With Vaned Diffuser

Centrifugal compressor is widely used in aeroengine.When the centrifugal compressor operates under the condition of small flow,there will be instable flow phenomena such as stall and surge in each component,which will limit the stable operation range of the centrifugal compressor and even cause irreversible damage to the centrifugal compressor.In order to avoid this situation and enhance the safety and reliability of centrifugal compressor in operation,it is necessary to study the unsteady flow phenomenon of centrifugal compressor under the condition of small flow.In this paper,the high speed centrifugal compressor with vaned diffuser is tested,and the performance and internal dynamic data of flow field of high-speed centrifugal compressor with vaned diffuser under different rotating speeds and different flow rates are obtained,and the unsteady flow phenomena such as stall and surge are captured.The steady and unsteady characteristics of the internal flow field of the centrifugal compressor are analyzed by CFD numerical simulation method.The analysis results provide further reference for the study of the unsteady flow phenomenon of the highspeed centrifugal compressor with vaned diffuser.The specific contents of this paper are as follows1.Participated in the construction of high-speed centrifugal compressor test-bed,mastered the operation method of high-speed centrifugal compressor,mastered the static and dynamic aerodynamic parameters testing technology.The performance curves and the dynamic data of the internal pressure of the centrifugal compressor are obtained.2.The performances of the vaned diffusers at three different installation angles(18 °,14.5 °,21.5 °)are studied by experiments.The complexity of the flow in the high-speed centrifugal compressor with vaned diffuser is shown by the dynamic pressure data.3.The steady numerical calculation method of single channel is used to simulate the centrifugal compressor with vaned diffuser.The performance curves at different rotating speeds are obtained.After comparison and verification with the experimental results,the flow field characteristics under three representative conditions(blocking condition,design condition,near instability condition)are analyzed.4.The unsteady numerical simulation of a high-speed centrifugal compressor with vaned diffuser is carried out by using a full circle flow passage.It is found that the steady and unsteady results are close at low rotating speed(70% of design speed),while the steady and unsteady results of high rotating speed(design speed)are quite different.From the comparison of the flow field,it can be found that the unsteady calculation captures the influence of the reverse flow caused by the diffuser on the impeller and the influence of reverse flow on the working capacity of the impeller lead to the difference between the steady and unsteady calculation.5.The surge process of centrifugal compressor is captured in the experiment.Based on the dynamic pressure data and numerical calculation,the mechanism of unsteady flow in the centrifugal compressor is analyzed.Through detailed study of the internal flow field of vaned diffuser under unstable condition,the development and propagation process of the unsteady flow structure in the highspeed centrifugal compressor is clearly demonstrated.