Abstract: In order to study the impact of improved vaned diffuser ratio for stage performance in real gas condition for a basic stage with single-shaft multi-stage centrifugal compressor，vaned diffuser entrance angle was adjusted and performance close loop test was carried out with nitrogen and carbon dioxide，respectively. Test results show that on close loop real gas test system by adjusting vaned diffuser entrance angle，impeller and vaned diffuser matching was optimized and the basic stage performance has been improved. By further transferring the test performance into dimensionless performance，results show that energetic coefficient increases by 1.86%，polytropic efficient increases by 1.1%，surge and blocking margin is improved on the improved basic stage，and dimensionless performance deviation of nitrogen and carbon dioxide on the basic stage is small. This confirms the dimensionless performance of basic stage.

Key words: Centrifugal compressor；Basic stage；Performance improvement；Closed loop test；Dimensionless performance

摘要： 为研究真实气体条件下改进叶片扩压器扩压度对级性能的影响，基于真实气体闭式试验，对用于单轴多级离心压缩机的某基本级进行了扩压器入口安装角度调整，采用两种试验气体N2和CO₂，对调整后的基本级进行了真实气体闭式系统下的性能试验。试验结果表明:在真实气体闭式系统下，通过扩压器入口安装角度调整，叶轮和叶片扩压器匹配得到优化，基本级性能得到改进，基本级的能头系数增大1.86%，多变效率提高1.10%，喘振和阻塞裕度均有所改善。同时，两种试验气体N2和CO₂下基本级的无量纲性能偏差很小，表明无量纲性能是基本级的特性。

关键词: 离心压缩机；基本级；性能改进；闭式试验；无量纲性能