Parameterized design for three-dimensional geometry of the pipe diffuser was preformed based on programmed model-construct method.The flow field and attack angle characteristics were investigated using time-averaged numerical method

and design parameters of the pipe diffuser were analyzed and optimized subsequently.Compared with the prototype vane diffuser

the performance of a pipe diffuser with traditional circle inlet was evaluated.Further study initiated a pipe diffuser with ellipse-like inlet which would expand the working range of centrifugal compressor

and suggested the mechanism of the improvement.