Study On The Flow Structure Parameters Of Micro Centrifugal Pump Impeller And Its Characterization

Centrifugal pumps are turbomachinery with an extensive range of applications.Among them,micro centrifugal pumps,which are widely used in microfluidic transmission and medical equipment due to their special size range,are attracting more and more attention of researchers.As a special-size centrifugal pump,the micro centrifugal pump has some key problems in its daily use,such as instability and low efficiency.Correctly grasp and accurately capture the internal flow structure of the pump and its temporal and spatial evolution have great significance to understand the operation instability of micro-centrifugal pump,internal flow structure and the cause of flow instability.In this paper,the model pump of micro centrifugal pump was taken as the research object to capture and analyze the flow structure inside the impeller under different operating conditions.Combining with the internal flow parameters such as velocity,pressure,streamline and separation vortices,the analysis of the spatiotemporal evolution and unstable characterization of the internal flow structure were carried out.Under different flow rate,the vortices of the impeller internal flow and the impeller circumferential pressure pulsation were analyzed.Based on the numerical analysis,and combined with the energy gradient theory,the research on the evolution of internal flow structure of multi flow rate of micro centrifugal pump was carried out from the perspective of energy field.It provides more research ideas and analysis basis for the analysis of internal flow structure and optimization design of micro centrifugal pump.The main work of this paper includes:1.The steady numerical simulation of micro centrifugal pump was carried out,and the head curve was obtained.The flow characters such as its internal velocity field,pressure field,streamline and vortex core under different flow rates were qualitatively and quantitatively analyzed.Based on the energy gradient theory,the internal flow structure of the micro centrifugal pump was analyzed,and the flow conditions inside the impeller under different flow rate were researched.It is found that the energy gradient function K can capture internal flow fields with the abrupt of mechanical energy gradient and the abrupt of shear force,and could reflect the flow instability on the blade surface caused by the strong shear stress in the outer eddy of large-scale vortices.2.The unsteady numerical simulation of micro centrifugal pump was carried out,and the time evolution of flow structure inside the impeller was analyzed.Based on the energy gradient theory,the flow parameters in the impeller are extracted and analyzed from the energy viewpoint.The relationship between the internal flow field and energy gradient function K was studied.It is found that as the impeller moves closer to the tongue,the scale of the small scale vortex gradually increases,and the magnitude of pressure fluctuation in the flow field near the tongue is aggravated by the development of vortices.3.The unsteady numerical simulation of the micro centrifugal pump under the periodic variable flow rate was carried out.The flow rate function of the sine wave was used to analyze the internal flow in impeller of centrifugal pump.The internal field under the flow rate increasing section,the flow rate decreasing section and the special flow rate of the flow function were analyzed.It is found that during the change of flow rate,the velocity and pressure difference of the flow field near the pressure surface are huge.It has exacerbated the degree of mechanical energy gradient change on the pressure surface.And the flow instability in the pump impeller is more likely to occur in the flow rate increasing section than the decreasing section.Finally,according to the flow characteristics of the pump impeller under various working conditions,it is found that the flow characteristics of the micro centrifugal pump impeller are different under different operating conditions,while phenomena such as the large flow losses,the complex flow structure and the local flow field pressure fluctuations are interaction with each other.The instability regions are often accompanied by sudden changes of flow parameters such as velocity,pressure and shear stress.Therefore,it is feasible and reasonable to use the energy gradient theory to analyze the internal flow field characteristics from the energy perspective.