A diagonal fan is disclosed and includes a frame and an impeller. The frame includes an inlet, an outlet, an accommodation space and a guiding wall. The inlet and the outlet are communicated through the accommodation space. The guiding wall is extended along an axial direction to the accommodation space. The impeller is accommodated within the accommodation space and includes a conical section shell. When the impeller is rotated, an airflow flowing is generated. The outer diameter of the hub of the impeller is expended gradually in a direction from the inlet toward the outlet, so that the flowing direction of the airflow is expended gradually around the peripheral of the impeller. A gap having a spacing distance is substantially maintained to form a backflow channel. A backflow is transported through an intake section, a horizontal section and an exhaust section of the backflow channel, and converged with the airflow.

A boundary layer ingestion fan system for location aft of the fuselage of an aircraft is shown. It comprises a nacelle defining a duct, and a fan located within the duct. The fan comprises a hub arranged to rotate around a rotational axis and a plurality of blades attached to the hub, each of which has a span from a root at the hub defining a 0 percent span position (r.sub.hub) to a tip defining a 100 percent span position (r.sub.tip) and a plurality of span positions therebetween (r∈[r.sub.hub, r.sub.tip]). The hub has a negative hade angle (γ) with respect to the rotational axis at an axial position coincident with the leading edge of the blades.

A boundary layer ingestion fan system for location aft of the fuselage of an aircraft is shown. It comprises a nacelle defining a duct, and a fan located within the duct. The fan comprises a hub arranged to rotate around a rotational axis and a plurality of blades attached to the hub, each of which has a span from a root at the hub defining a 0 percent span position (r.sub.hub) to a tip defining a 100 percent span position (r.sub.tip) and a plurality of span positions therebetween (r∈[r.sub.hub, r.sub.tip]). A plurality of outlet guide vanes are positioned aft of the fan. An afterbody is located aft of the plurality of outlet guide vanes and which tapers to an apex having an apex angle with respect to the rotational axis of between 35 and 45 degrees.

The aspects of the disclosed embodiments are directed to a fan for displacing a fluid, which fan includes a rotor rotating around its axis of rotation and surfaces, such as blades, forming a flow when the rotor rotates. The rotor is arranged to displace fluid simultaneously with at least two different flows (F1, F2).

A disclosed gas turbine engine includes a gas generator section for generating a gas stream flow and a propulsor section for generating propulsive thrust as a mass flow rate of air through a bypass flow path. The propulsor section includes a fan driven by a power turbine through a speed reduction device at a second rotational speed lower than a first rotational speed of the power turbine. An Engine Unit Thrust Parameter (“EUTP”) defined as net engine thrust divided by a product of the mass flow rate of air through the bypass flow path, a tip diameter of the fan and the first rotational speed of the power turbine is between 0.05 and 0.13 during operation of the gas turbine engine.

A turbofan engine includes a fan section that drives air along a bypass flow path in a bypass duct. An epicyclic gear system in driving engagement with the fan shaft and has a gear mesh lateral stiffness and a gear mesh transverse stiffness. A gear system input to the gear system defines a gear system input lateral stiffness and a gear system input transverse stiffness. The gear system input lateral stiffness is less than 5% of the gear mesh lateral stiffness. A first performance quantity is defined as the product of a first speed squared and a first area and a second performance quantity is defined as the product of a second speed squared and a second area. A performance quantity ratio of a first performance quantity to a second performance quantity is between 0.5 and 1.5.

A propeller fan includes: a rotation-axis part that serves as a center of rotation; and a plurality of blades provided on an outer circumferential side of the rotation-axis part, the plurality of blades being joined to adjoining blades at leading edges and trailing edges thereof. A first rib projecting towards the center of rotation of the rotation-axis part to surround the rotation-axis part, and second ribs projecting towards the center of rotation to extend from the rotation-axis part toward the first rib are provided on pressure surfaces of the plurality of blades. Among ends of the second ribs in the direction of the center of rotation, the ends distant from the pressure surfaces project away from the pressure surfaces farther than an end of the first rib distant from the pressure surfaces, among the ends of the first rib in the direction of the center of rotation.

An impeller is provided, including a metal housing, a shaft, and a plastic member. The metal housing has a shaft mounting hole. The inner surface of the shaft mounting hole includes three or more contact points, and the contact points are closer to the shaft than other portions of the inner surface of the shaft mounting hole. The shaft passes through the shaft mounting hole and is affixed by the contact points. The metal housing divides the shaft into an upper section, a middle section, and a lower section. The plastic member passes through the shaft mounting hole and is in contact with the middle section.

An airflow-doubling vane structure includes an axle, an inner vane unit, and an outer vane unit. The inner vane unit includes a plurality of vanes provided around a center defined by the axle and can be rotated along with the axle. The vanes of the inner vane unit are centrifugal vanes. The outer vane unit includes a plurality of vanes provided around the center defined by the axle and around the inner vane unit and can be rotated along with the axle. The vanes of the outer vane unit are axial-flow vanes and extend a certain radial distance from the vanes of the inner vane unit.

A counter-rotating fan, comprising two impellers and a motor. The motor is used for driving the two impellers to rotate. The two impellers are axially spaced apart from each other, and are divided into a first-stage impeller and a second-stage impeller. When the counter-rotating fan operates, airflow is blown to the direction of the second-stage impeller by means of the first-stage impeller. At least one impeller has turns of blades arranged in the radial direction of the impeller. Blades of each turn are spaced apart from each other around a hub of the impeller, and a spacer ring is connected between two adjacent turns of blades. The counter-rotating fan is stable in rotation and good in cooling effect, it is not easy to deform, and the wind is strong in the center.