Abstract
The effects of various parameters on the hovering performance of an annular lift fan aircraft are investigated by using numerical scheme. The pitch angle, thickness, aspect ratio (chord length), number of blades, and radius of duct inlet lip are explored to optimize the figure of merit. The annular lift fan is also compared with a conventional circular lift fan of the same features with the same disc loading and similar geometry. The simulation results show that the pitch angle of 27°, the thickness of 4% chord length, the aspect ratio of 3.5~4.0, 32 blades, and the radius of inlet lip of 4.7% generate the maximum figure of merit of 0.733. The optimized configuration can be used for further studies of the annular lift fan aircraft.
Highlights
Humans have been dreaming of building an airplane that can do “substantially everything that a bird can do in the air”, as revered New York University aeronautical engineer AlexanderKlemin described, that can take off, land and hover anywhere like a helicopter and fly as fast as a fixed-wing plane
According to the computational fluid dynamics (CFD) simulation results [10], the annular lift fan aircraft with the same size of the Apache rotor can have higher lift efficiency in a hover and may fly much faster than helicopters in a cruise based on the3,aerodynamic drag predictions
We focused on the optimization of parameters of the annular lift fan system for hovering efficiency
Summary
Humans have been dreaming of building an airplane that can do “substantially everything that a bird can do in the air”, as revered New York University aeronautical engineer Alexander. There are four types of successful and practical VTOL aircraft so far, which include helicopters, vectored jet aircraft, tiltrotors and ducted lift fan aircraft These aircraft provide solutions to this problem, and have some disadvantages. The annular duct around the fuselage can greatly increase the lift fan area to achieve low disc loading and can be shut off by shutters and louvers during cruise flight to provide aerodynamic lift and reduce drag. According to the computational fluid dynamics (CFD) simulation results [10], the annular lift fan aircraft with the same size of the Apache rotor can have higher lift efficiency in a hover and may fly much faster than helicopters in a cruise based on the3,aerodynamic drag predictions
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