The Optimal Design Of Gas Bleeding Structure For Centrifugal Compressor

Centrifugal compressors are widely employed in aerospace, power plant, chemical industry, metallurgy and many other fields. In the petrochemical industry, as the requirement of the process, addition or extraction of gas maybe needed during the compression. And in the traditional gas bleeding structure design, the common practice was to lead the flow to a bit cavity first and then make an aperture on some position of the wall which connected to the discharge pipe system. The structure was simple to realize but might cause flow distortion problem, affecting the operating efficiency, or even resulting in rotating stall that might threaten the safety operation of the machine.CFD method was applied to study the principle of the flow in between stages and to get the optimal design of the gas bleeding structure. Volute structure was adopted and optimized to ensure the circumferential uniformity of the flow field upstream and downstream of the bleeding structure in-between the stages. A complete model, including the impeller, the diffuser, the curved conduit, the gas bleeding structure and the return channel, was built in order to specify the right boundary condition and to obtain the correct flow solution. The volute and the clapboard of the structure were designed carefully to meet the requirement of the mass flow rate of the bleeding flow and to establish a proper flow field around the clapboard. Numerical simulation was carried out using the CFD software FINE-TURBO. Based on the analytic results, modifications of the design of the bleeding structure were proposed and experimented numerically.. The final results indicate that a satisfactory performance of the stage can be secured and right amount of the bleeding mass flow can be obtained. The design method developed in this thesis may provide a guideline for all kinds of the bleeding structures in-between centrifugal compressors.