Matching Ram-rotor Centrifugal Compressor Aerodynamic Design

As a new compression system, the ram-rotor has acquired the advantages of high single-stage pressure ratio, high total efficiency, small size of aerodynamic losses, compact structure, light weight, high reliability, easy maintenance, low cost and so on. One of the problems of the ram-rotor in practice is matching problems between airflow with large exit flow angle and combustion chamber.This paper intends to design a high efficient centrifugal compressor, which adjusts the air outlet angle from the ram-rotor, and makes it easy to match with the combustion chamber. However, the rotor is impossible to directly connect with the centrifugal compressor blades. So this paper also designs a transition section which connects the ram-rotor and the centrifugal compressor.In the design process of transition section, by adopting VB programming, it generates four transition curves of the upper and lower walls:Vickers curve. Axis vickers curve. Double cubic curve. Five times curve. It generates three-dimensional model and grids in GAMBIT. By FLUENT, it can be concluded that the model in the transition section takes Vickers curve as the upper and lower walls’curve. The exit flow field is relatively uniform, the exit flow angle is relatively small, the total pressure recovery coefficient is relatively high and the internal flow is better.In the process of centrifugal compressor design, by using NREC software, it completes the process of model establishment and optimization from one-dimension to three-dimension. The centrifugal compressor model is divided into grids and taken into simulations, and it obtains the compressor efficiency and pressure ratio characteristic curve of three different flow angles, which proves that the compressor designed has better variable conditions adaptability. By analyzing the internal flow field, it acquires the size of the curvature of the compressor blade root and blade tip and the greater impact of the trailing edge and inlet flow angle on the performance.At last, by the design from one-dimension to three-dimension and numerical calculation, it obtains a centrifugal compressor whose impeller is ante version and sweepback, with the diameter of hub being100mm, the outer diameter of impeller inlet being160mm, the diameter of impeller outlet being224mm and the number of blades being11.