Performance Analysis And Structural Improvement Of The Static Components Within The Single-stage Centrifugal Compressor

With the obvious advantages of high efficiency, high reliability, compact structure and low emission and low cost, the micro gas turbine (MGT) is gaining an irreplaceable position in power industry and military. The research and application of the centrifugal compressor, a key component in the micro gas turbine, becomes the main research task in China. Static components such as diffusers and volutes play an important role in the centrifugal compressor because they can improve the performance of the compressor and broaden the operating range. But the flow in static components is complex because it is influenced by not only the rotating impeller upstream but also the block of their own structure. The comprehensive understanding of the flow mechanism in static components is crucial to design high quality components. This thesis tries to carry out a deeper investigation in this field.The main work in this thesis is on the optimization of the static components of the centrifugal compressor, a pivotal component in some type of micro gas turbine. Our research procedure is composed of design, modeling, computation, flow analysis and redesign, and we apply AUTOCAD, CAXA,PRO/Engineering and NUMECA to complete the frame construction and data analysis.A valuable work has done on the research of optimizing the diffuser. On the basis of the design of the vaneless diffuser and the numerical simulation of the flow field in the vaneless diffuser, the structure of the vaneless diffuser is improved by using a new method of a hub vane diffuser. Meanwhile, the method of a shroud vane diffuser is presented. The effect of the height of the hub/shroud vane to the performance of the diffuser is deeply discussed to seek the best structure of the hub/shroud vane diffuser. In addition, a method of the diffuser with the hub/shroud vane is applied to the original vane diffuser. Some valuable inference can be drawn from the attempt and research of the method. The result shows that the performance of the shroud vane diffuser with 0.4b height or the hub vane diffuser with 0.2b height is much better than that of the vaneless diffuser, and proves that the efficiency of the shroud vane diffuser with 0.4b height has been increased by more than 3 percent on the basis of the original vane diffuser.Based on one-dimensional aerodynamic design theory and correction of area parameters, the structure of the asymmetrical circle volute which has the same inside diameter is presented on the improving design of the volute. Through the numerical analysis of the complicated flow within the volute, the structure of the asymmetrical circle value is changed into the asymmetrical pyriform volute. Depending on the contrast and analysis of the two structures, the result can be found that the performance of the pyriform volute is improved obviously, and the total stage efficiency of the new centrifugal compressor with the changed volute has yielded approximately 2% increase of the original compressor efficiency. The work provides valuable experience and reference for future design and research of the volute in the centrifugal compressor.