Assignment 1
ENT241 FLUID MECHANICS 1
ASSIGNMENT 1
An unloaded helicopter of mass 12,000 kg hovers at sea level while it is being loaded. In the unloaded hover mode, the blades rotate at 550 rpm. The horizontal blades above the helicopter cause a 18 m diameter air mass to move downward at an average velocity proportional to the overhead blade rotational velocity (rpm). A load of 14,000 kg is loaded onto the helicopter, and the helicopter slowly rises.
Take the density of atmospheric air to be 1.18 kg/m3. Assume air approaches the blades from the top through a large area with negligible velocity and air is forced by the blades to move down with a uniform velocity through an imaginary cylinder whose base is the blade span area.
(a) Determine the volumetric airflow rate downdraft that the helicopter generates during unloaded hover and the required power input.
(b) Determine the rpm of the helicopter blades to hover with the 14,000 kg load and the required power input.
(c) If you have to develop a new helicopter with the same mass of 12,000 kg and the maximum rpm of the motor only up to 550 rpm, suggest a minimum propeller blade width span to overcome the hovering with additional load of 14,000 kg and justify your answer.
ASSIGNMENT 1
An unloaded helicopter of mass 12,000 kg hovers at sea level while it is being loaded. In the unloaded hover mode, the blades rotate at 550 rpm. The horizontal blades above the helicopter cause a 18 m diameter air mass to move downward at an average velocity proportional to the overhead blade rotational velocity (rpm). A load of 14,000 kg is loaded onto the helicopter, and the helicopter slowly rises.
Take the density of atmospheric air to be 1.18 kg/m3. Assume air approaches the blades from the top through a large area with negligible velocity and air is forced by the blades to move down with a uniform velocity through an imaginary cylinder whose base is the blade span area.
(a) Determine the volumetric airflow rate downdraft that the helicopter generates during unloaded hover and the required power input.
(b) Determine the rpm of the helicopter blades to hover with the 14,000 kg load and the required power input.
(c) If you have to develop a new helicopter with the same mass of 12,000 kg and the maximum rpm of the motor only up to 550 rpm, suggest a minimum propeller blade width span to overcome the hovering with additional load of 14,000 kg and justify your answer.