PERFORMANCE EVALUATION OF A SHROUDED ROTOR IN FLOW NORMAL TO ITS AXIS 580144
This paper describes briefly a program conducted on one form of shrouded rotor. The form considered here could perhaps be reasonably described as a buried rotor, since the rotor is entirely enclosed in a form of ducting which will permit hovering conditions as well as forward flight conditions. The paper covers the reason for choosing this particular type of configuration along with a description of the testing program which has been started in order to evaluate its performance. By entirely enclosing a rotor in the manner described, it is possible to obtain very high hovering efficiency, and at the same time by ducting the air properly through the rotor, it is possible to use this system for forward propulsion. The results of the tests indicate the advantages that have been gained through this arrangement and also show what penalties can be expected to be paid for obtaining these advantages. By placing this rotor in a wing, it should be possible to obtain hovering efficiencies which are slightly less than those of a helicopter and yet be able to get forward flight speeds greater than those possible with a helicopter. It should also be possible to do this in a vehicle which utilizes basically one propulsion system, and which obtains its transition from hovering to forward flight by means of ducking air rather than by turning either the propulsion system or the vehicle itself. Although the work of this program is not yet complete, it should be clear from the indications of the results obtained so far that this configuration could be a very useful tool in the flight regime existing between the helicopter and the high speed airplane.