Design Of The Two Stage Centrifugal Compressor With High Efficiency

Micro turbine has light weight, high power, high power density advantages, which has a widerange of application prospects in both military and civilian. As its important components, compressorperformance influences the performance of the engine directly. Therefore, it is necessary to conductin-depth study on the compressor. In this paper, a aerodynamic design on a two-stage centrifugalcompressor of a micro turbine with inter-stage cooling was carried out, and so did the study on theinfluence of the periphery to the non-uniformity of the volute.Firstly, the one-dimensional estimation procedures of the centrifugal compressor of the researchgroup was improved, so that it can be applied to the two stage compressor calculation, then the mostsuitable inter-stage pressure distribution and speed were worked out. Results show that the efficiencyof the compressor to achieve the best at the total pressure ratio5.4case, the first stage pressure ratio2.48. The speed calculation results show that the first stage centrifugal compressor efficiencyincreases with little speed change, while the second stage efficiency increases with high speed change.The size and the speed of the two-stage compressor were ensured after parameter optimization.Three-dimensional modeling design on two-stage centrifugal compressor impeller, diffuser andvolute was carried out. Based on the3D CFD calculation of the flow performance of every part apreferred final plan was chosen and analyzed. The united calculation results of the impeller anddiffuser showed that matching work reduced the diffuser performance, the main which caused thediffuser performance reduced was the great changes on spanwise inlet airflow angle of the diffuser.Improving the design of the diffuser to improve the whole level of performance to meet the designrequirements of the compressor and three-dimensional modeling.The non-axial symmetry of the volute influenced the diffuser and the impeller flow performance,the complete flow condition of diffuser and volute were obtained by calculating in the whole classenvironment. A channel formed by vaned diffuser and volute tongue made the flow conditionextraordinarily complex, and a low velocity zone was created at the convex side near the volutetongue in diffuser channel. The source of the major loss was the diffuser outlet jet and wake blendedwith each other, the loss of circumferential angle at0-180degrees was greater than180-360degrees.In the whole-stage calculation, the vane diffuser rotating a certain angle relative to the volute,then formed four different programs to explore the mutual influence law of the diffuser and volute indifferent locations of the diffuser vanes relative to the volute tongue. When there was a tangent between one blade of the diffuser and volute volute tongue, the performance of the whole level is thebest and only one channel had large separation. The number of diffuser channels of other angles withthe large separation was two. The volute wall close to the diffuser outlet that caused the blockage isthe main reason for large the separation.To the large separation in the diffuser, the article attempts to reduce the separation within thechannel by reducing the convex length of the blade within the diffuser channels adjacent to the volutetongue. The results show that reducing the length of the blade can surely reduce the separation zonewithin the channel, but there was no obvious impact on the entire stages performance, theperformance trends change of the impeller diffuser shape, the diffuser and the volute were differentafter changing the diffuser model. Remove one blade enables the big diffuser separation zonedisappears, the total pressure recovery coefficient of the diffuser is the highest, but the increase of theoutlet velocity caused the loss of the volute increase, and a further increase in the rate of diffusion ofthe diffuser, the pertinence optimization of volute should can improve the performance requirements.