Semester

Spring

Date of Graduation

2008

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Abstract

One of the most maintenance intensive components of all present-day helicopters is the swash-plate, and its associated control linkages. This mechanism is also the major contributing factor to fatal accidents associated with helicopter flight. However, the swash-plate is an essential component in providing controlled flight, by transmitting the pilot's control-inputs to the main rotor. Another side-effect of using the swash-plate is that it increases the diameter of the main rotor shaft assembly, slightly increasing the total drag of the aircraft. Thus, there are several benefits that could be achieved by removing the swash-plate of the helicopter.;To enable the removal of the swash-plate from a rotorcraft, a method is needed to augment the aerodynamic performance of the main rotor blades as a function of azimuth angle, while maintaining the traditional cyclic and collective pilot controls. Circulation control can provide a means of changing the aerodynamic performance without physically changing the angle of attack of the blade, as is currently done by the swash-plate. Thus, the current project was conceived to investigate the use of surface-mounted valves to control leading and trailing edge circulation control blowing as a means of decreasing the flow establishment time for circulation control wing lift augmentation.;Both experimental and computational methods were implemented in this study. From the experimental results, a lift augmentation ratio (C 1/Cmu) of 47 could be achieved in 56 msec, with the model at an angle of attack of 0.68 degrees. The computational study yielded a force establishment time of 55 to 60 msec to achieve a lift coefficient greater than 5 at 0 degree angle of attack. From this data it is concluded that the use of a circulation control airfoil, with blowing jet controlled at or near the airfoil surface, can effectively be used on a helicopter main rotor if the rotor speed is less than 275 rpm with four defined force control points per revolution. The rotational speed is within the operational range of current technology rotor speeds.

Download

Share

COinS