Abstract
In recent years, few studies focused on adjusting the load distribution of contra-rotating fan (CRF) blades. To improve the overall performance of CRFs, we used a design code to build 32 sets of CRFs to determine the effects of three factors—the front and rear rotor load matching, the load distribution of each rotor and the axial distance between the rotors—on the total pressure rise and efficiency of CRFs using numerical calculations. The relationship between the CRF blades load and velocity components was theoretically analyzed using blade element analysis and the forward problem method. According to the performance curve, it can be concluded that the rear rotor (RR) is the key factor that determines the performance of CRFs. Through analyzing Mach number contours from different perspectives, the relationship between velocity and adjustment load was verified. Furthermore, the flow field characteristics for three specific CRFs were explored at the stall points, design points and choke points to reveal their flow mechanisms. This study provides a reference for the CRF blade design method.
Highlights
The baseline model used in this paper was a contra-rotating fan (CRF) designed according to the free vortex design method
Two specific combinations were selected from the 32 sets of CRFs that could lead their design points to move to the highest and lowest performance regions, enlarging the differences with the baseline CRF as a result
Value a = 0.6, axial gap = 0.5, while the load control was applied to the front rotor (FR)
Summary
The baseline model used in this paper was a CRF designed according to the free vortex design method. The blade profile in each element from the hub to the shroud was designed according to NACA-65 series cascade profiles experimental data from Mellor [12]. Their load distribution ensured better performance in low subsonic compressors.
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