Initial Cycle Analysis and Stage Sizing
TURBOdesign Pre was used to investigate the choice of design point, rotational speed selection and the pressure ratio split between the 1st and 2nd compressor stage. Both the cycle analysis and the compressor dimension/performance are available using the cycle/meanline coupled simulation. A preliminary performance map prediction was also provided by TURBOdesign Pre analysis. Based on a parametric study the design flow rate and RPM were selected and the optimum pressure ratio split between 1st and 2nd stage was determined.
TURBOdesign1 was used to design an initial first and 2nd stage impeller with full blade (no splitters). Through CFD evaluation the key aspects of the impeller design that impact manufacturing requirements such as power consumption and axial thrust were confirmed. An unshrouded impeller was used for the study because of manufacturing requirements.
3D Design and Optimization of Compressor Stage
In order to meet the wide operating range requirements splitter blades were used for the final design. TURBOdesign1, by specifying the loading distribution for the full and splitter blade independently can design high efficiency impellers with splitter blades which don’t necessary have the same shape as full blade. Therefore, the blade surface pressure distribution can be controlled by using the aerodynamic inputs, in comparison to the conventional design methods where blade angles and camber line profile are specified in a trial-error practise and where the splitter blade are generally placed at mid-pitch location and have the same geometry as the full blade. The commercial CFD code (ANSYS CFX) was used to verify the performance of the impeller under various operating conditions. For the 2nd stage inlet conditions, some pipe loss was assumed. Some design iterations were carried out to meet the high-capacity requirement.
Following the aerodynamic design, the FEA and modal analysis were conducted on the impeller structure. TURBO design Volute was used to design the volutes for each stage.