Low-noise, high-efficiency fan assembly combining unequal blade spacing angles and unequal blade setting angles

A vehicle fan assembly for circulating air to cool an engine, said fan assembly comprising:

• a central hub;
• a plurality of blades disposed circumferentially around and extending radially outward from said central hub between a blade root joined to said central hub and a blade tip with a blade span formed between said root and said tip;
• unequal spacing angles by which said blades are spaced circumferentially from each other around said central hub, said unequal spacing angles minimizing noise produced by said fan assembly;
• unequal setting angles by which said blades are positioned at a radial location along a blade span, said unequal setting angles increasing the maximum efficiency of said fan assembly;
• and
• one of an electric motor and a hydraulic motor imparting mechanical energy to said fan assembly.

A process for designing a vehicle fan assembly circulating air to cool an engine and having a central hub and a plurality of blades disposed circumferentially around and extending radially outward from said central hub between a blade root joined to said central hub and a blade tip with a blade span formed between said root and said tip, said process comprising:

• (a) determining the unequal spacing angles, by which said blades are spaced circumferentially from each other around said central hub, required to minimize noise produced by said fan assembly;
• (b) calculating velocity triangles for each of several radial sections along said span of each blade of said fan assembly;
• (c) optimizing, from the velocity triangles, the setting angles required at each radial section along said span of each blade to produce substantially equal loading on each blade of said fan assembly;
• and
• (d) positioning said blades of said fan assembly at the determined unequal blade spacing angles and optimized unequal blade setting angles.