# Flow Control of Radial Inlet Chamber and Downstream Effects on a Centrifugal Compressor Stage
[29] found that the circumferentially nonuniform variable inlet guide vanes in the radial inlet chamber were more adaptable to the incoming flow angle, which could reduce the flow loss by 40%. In addition to the optimization of the radial inlet chamber itself, its impact on the downstream components is also a key issue to the performance of the entire compressor. [PERSON] et al. [30] studied the effects of radial inlet chambers on the performance of a centrifugal compressor stage with inlet guide vanes. The results indicated that, compared with the uniform axial intake, the efficiency and total pressure ratio of the compressor stage with a radial inlet chamber decreased by an average of 2.5% and 1%, respectively, over the entire operating range, and the regulation performance of the inlet guide vanes was also adversely affected. [PERSON] et al. [31] carried out experimental and numerical studies on the radial inlet stages of two different industrial centrifugal compressors and analyzed the effects of the internal flow loss and the outlet distortion of the inlet chambers on the performance of the downstream components. According to the literature review, it was found that flow loss and distortions were the two main factors that affected the performances of the inlet chamber itself and the downstream components in the compressor. However, the influence mechanism of the radial inlet chamber on the entire centrifugal compressor has still not been completely revealed, and the following problems remain unsolved. First, in the previous research, the optimization objects of the radial inlet chambers were either to reduce the flow loss or increase the uniformity of the outlet flow without considering these two factors together. This approach has limited a more comprehensive improvement of the radial inlet chamber. Second, although it is known that the flow uniformity at the impeller inlet is essential for the compressor stage, the complex flow distortions induced by the radial inlet chamber involve many parameters (e.g., the uneven distributions of pressures, velocity magnitudes and distortions of different velocity components), and which is the most important to the performance of the entire compressor is still unknown. This hinders further improvement in the performances of centrifugal compressors with radial inlet chambers. Meanwhile, the inlet guide vanes analyzed in the previous studies are generally arranged downstream or without the inlet chamber, while there is less research related to the guide vanes inside the radial inlet chambers. With the development of numerical theory and computational technology, CFD methods are widely used for flow analysis and structure improvement in various engineering applications [32; 33; 34]. Therefore, in this paper, numerical simulations are performed on the radial inlet chamber with and without guide vanes to figure out the mechanism of flow loss and distortions generated in the inlet chamber. Then, in order to solve the first problem, the flow loss and distortions are considered together to obtain an improved design of the radial inlet chamber. Finally, for the second problem, the major parameters related to the flow uniformity are investigated at the impeller inlet, expecting to develop an in-depth understanding of the influence mechanism and provide guidance for further improvement of centrifugal compressors with radial inlet chambers.