A one-step optimization method for a compressor wheel of a microturbine engine

The work deals with the design acceleration of optimal turbomachines. For its solution, it is proposed to apply mathematical optimization methods at the initial design stage. The goal of the study was to develop a one-step algorithm for optimal compressor wheel design. The application of the algorithm has a decisive advantage in comparison to the traditional iterative method for turbomachines design. The task of designing a turbomachine is multi-parameter and interdisciplinary and involves different requirements, which often contradict each other, consequently several optimality criteria can be used simultaneously. The traditional method consists in performing one-dimensional thermal and gasdynamic calculations with subsequent refinement using numerical study. Further fine-tuning of the wheel geometry includes variation of the blade angle at the exit from the impeller, as well as of the height of the flow path at the exit from the wheel. One-step global optimization was performed by using a particle swarm algorithm involving eleven variable parameters. The objective function is thermodynamic efficiency, calculated by stagnation parameters. The authors compare the results of calculating the geometry of the centrifugal compressor wheel by the traditional sequential method and by the newly developed global optimization method. The compressor wheel has an outer diameter of 200 mm, the diameter of the hub is 52 mm, the rotational speed is 60,000 rpm and the required compression ratio is 3.7. In the traditional optimization method, the blade angles and the profile thickness are varied in three or four blade cross sections. The novelty of the developed one-step algorithm consists in the optimization of the initially three-dimensional shape of the flow path. Testing has shown that the one-step global optimization method provides an efficiency gain of about 2 %. Compared to the traditional method, the required time decreased 6 to 18 times. The proposed method can be applied to the design of turbomachines of various dimensions. The developed algorithm can be used as a basis for external modules in various existing packages, such as Ansys, Comsol and SolidWorks.