Design of a Transonic High Flow Coefficient Centrifugal Compressor by Using Advanced Design Methods

Abstract

A high flow coefficient centrifugal compressor was designed in a joint cooperation of DLR and MAN Diesel & Turbo SE Berlin. The main goal of this work is to increase the flow coefficient in the aerodynamic design point by 20% in comparison to the reference design. Besides a significant increase in flow coefficient, isentropic efficiency should be at least equal to the reference design. Design methods of the last decades are not able to reach a high flow coefficient without a reasonable compromise in efficiency. Furthermore, common design methods introduce splitter blades to gain a higher flow coefficient. Usually splitter blades lead to structural mechanical issues by introducing different eigenfrequencies. Reference impeller and vaned diffuser as well as the main design goals and constraints are provided by MAN Diesel & Turbo SE Berlin. DLR performed the design studies using their in-house design suite including TRACE as the CFD solver, PERMAS as the CSM program and AutoOpti for the multiobjective optimization tool. In preliminary design investigations it was found that a reduction of blade and vane number is necessary to avoid diffuser choking at high flow coefficients. Finally, a favorable geometry is chosen for a future test rig configuration at MAN Diesel & Turbo SE Berlin. The new design works totally in transonic conditions. The selected design fulfills all aerodynamic and structural mechanical design goals.