Entecho has developed a unique aerodynamic lifting process, and with it, an entirely new type of aerial craft called the CAV, or Compact Aerial Vehicle. Entecho is now working on two CAV applications, the YouFly and the Mupod, using the latest technology in areas such as composites, flight control, and computational fluid dynamics, or CFD.
A Revolutionary Lifting Process
Entecho has overcome the key challenge of generating lift within a small vehicle envelope by employing a novel rotor fan and a unique combination of lifting surfaces. Unlike conventional fans which draw air from one side to the other, Entecho's centrifugal fan moves air radially from the center to its outside. Lift is generated as the radial flow from the fan is directed downward by the skirt. The skirt refers to the airtight flexible membrane which wraps circularly around the body of the craft and is located downstream of the rotor.
Airflow: As the drum fan rotates it pumps air radially through its blades. The air is drawn into the intake duct and is then accelerated as it passes through the fan. It is then directed downward by the skirt creating lift.
High Pressure: High pressure regions form as a result of the air being accelerated through the ducts by the rotating drum fan. These regions of higher pressure act on specific surfaces of the craft producing lifting forces.
Overall lift: The overall lifting force is a result of summing together all of the lifting forces.
Why a Centrifugal Fan?
The use of a centrifugal fan to produce vertical lift is the central concept of Entecho’s advanced lifting technology. This is primarily because it allows the creation of an extremely compact craft which has VTOL capabilities and high lifting efficiencies.
In order to understand why this is possible, first it is necessary to examine the aerodynamics of an ordinary helicopter rotor blade. Helicopter blades are axial and therefore the rotational velocity of the blade varies along its length, reaching a maximum at the blade tip. Since lift is proportional to velocity squared only the outer section of the blade is travelling with enough velocity to produce significant lift. This results in a small outer portion of the blade producing the majority of the lift and, consequently, longer blades are required to achieve the desired flight performance.
Unlike a helicopter rotor blade, the centrifugal Entecho rotor locates the entire span of the blades at the same maximum radius from the rotational axis. Hence, each blade is travelling through the air with the same rotational velocity for any given rotor RPM. This allows us to design a simple two dimensional blade geometry that will achieve maximum efficiency along its entire length. Moreover, each blade is now travelling at the maximum velocity possible at that RPM and radius of rotation. Hence, every blade has the maximum possible energy to perform work on the air and consequently produce lift.
Unique Control Techniques
The skirt is a flow vectoring nozzle that can generate high levels of control power. This skirt accesses the entire moving air stream, so by simply controlling the movement of the skirt, we can develop very desirable response characteristics both in translation and rotation.
Safety Focused Design
The blades of the hubless fan move at relatively low speeds, and are enclosed by the skirt. This eliminates the danger of high-speed, exposed blades that feature on helicopters and propeller planes. Furthermore, should a blade ever break for some reason, the broken blade will not penetrate the skirt since it is extremely light and will be moving relatively slowly. The lack of exposed blades means that safe operation near objects such as buildings and trees becomes possible.
The structure of Entecho’s YouFly incorporates a safety cell which has significant radial strength and maximizes the amount of energy that can be absorbed in a crash prior to any structure intruding into the central compartment.
Entecho has focussed initial development on a vehicle which is height controlled to approximately 1.5 m to maximize safety, but retains multi-terrain capability and the sensation of free flight.