Lifting engine for VTOL aircrafts

• US 4,796,836 A
• Filed: 02/03/1987
• Issued: 01/10/1989
• Est. Priority Date: 02/28/1985
• Status: Expired due to Fees

• Current Assignee: Technolizenz Establishment
• Original Assignee: Dieter Schatzmayr
• Inventors: Buchelt, Benno
• Primary Examiner(s): Barefoot, Galen
• Assistant Examiner(s): Fiorito, L. M.
• Application Number:
  US07/010,360
• Time in Patent Office: 707 Days
• Field of Search: 244/12.2, 244/23 R, 244/23 H, 244/23 B, 244/23 C, 244/56, 244/66, 244/67, 244/62, 416/DIG. 2, 416/DIG. 5, 416/223 R, 416/223 A
• US Class Current: 244/23.00R
• CPC Class Codes: B64C 29/0016 the lift during taking-off being created by free or ducted propellers or by blowers

Abstract

A hovering or VTOL aircraft with a propulsion unit using a fan in a shroud whose upper end is toroidally shaped and rotationally symmetrical with a convex curvature with a radius of curvature between 0.2 r_f and 1 r_f from a location 1.4 r_f upstream of the blade plane to a location 0.2 r_f downstream thereof. The blade, whose tip radius is r_f has a twist at least from a range of ±0.25 r_f around a mean radius between hub and tip to the tip such that the airflow velocity through the meridian increases outwardly from the hub of the fan toward the periphery of the fan.

Claims

1. A propulsion apparatus for generating vertical lift in an aircraft, comprising:

a fan shroud defining a substantially vertical airflow passage having an axis, an upper inlet end and a lower outlet end, said passage being rotationally symmetrical about said axis but differing from a right-circular cylinder over its entire length;

a fan rotatable in said passage about said axis and having a plurality of generally radial blades where the radial axis of these blades is lying in a plane perpendicular to said axis between said inlet and outlet ends and where these fan blades can be also rotatable around their blade axis for control purposes;

a torus-like convexly curved part rotationally symmetrical about said axis and formed on said shroud at said inlet end of said passage, said torus-like convexly curved part extending from a location substantially 1.4 r_f upstream of said blades seen radially to a location substantially 0.2 r_f downstream of said blades seen axially where r_f is a tip radius of said blades measured from said axis to a tip of the blades, said tips of said blades defining a gap with said part which is at most 1/25 of the diameter of said fan; and

at least one engine operatively connected with said fan for rotating same,

said rotating blades being of airfoil cross section with the angle between the chord lines of the blades and the rotation plane of the fan blades decreasing from the hub of the fan to a radial midsection of the fan blades and increasing from the radial midsection towards the fan tip by an increment (AB) having a value in the range from 0 degrees up to 25 degrees to generate upon rotation of said fan a meridional airflow velocity through said passage which is nonuniform over the radius thereof and increases from a value proximal to said axis to a maximum at the periphery of said passage, said radial midsection of the fan blades being defined as a distance ±

0.25r_f around a means fan blade radius and as the arithmetic means between fan hub radius and fan tip radius, and

the meridional radii of curvature of said torus-like convexly curved part between said locations being 0.2r_f to 1r_f.

2. The propulsion apparatus defined in claim 1 wherein said fan is a single-stage fan, said shroud being formed as a diffuser downstream of said torus-like convexly curved part, said torus-like convexly curved part merging smoothly into said diffuser.

4. The propulsion apparatus defined in claim 1 wherein a maximal number of two airfoil-shaped rotationally symmetrical inlet shields is provided above said inlet end and partly overlaps said torus-like convexly curved part and has a concave surface juxtaposed therewith, and wherein a meridional tangent to said torus-like convexly curved part where it is intersected by said plane of said blade axis includes an angle of 30°

to 70°

with said plane so that a narrowest part of said passage is located downstream of said plane of said blade axis.

5. The propulsion apparatus defined in claim 1 wherein said inlet end is free from air-guiding shields and a meridional tangent to said torus-like convexly curved part where it is intersected by said plane of said blade axis includes an angle of 30°

to 70°

with said plane so that a narrowest part of said passage is located downstream of said plane of said blades.

7. The propulsion apparatus defined in claim 2 wherein said diffuser is formed with a trailing edge at the outlet end, further comprising means for retracting said edge axially toward said plane.

3. A propulsion apparatus for generating vertical lift in an aircraft, comprising:

a fan shroud defining a substantially vertical airflow passage having an axis, an upper inlet end and a lower outlet end, said passage being rotationally symmetrical about said axis but differing from a right-circular cylinder over its entire length;

a fan rotatable in said passage about said axis and having a plurality of generally radial blades where the radial axis of these blades is lying in a plane perpendicular to said axis between said inlet and outlet ends and where these fan blades can be also rotatable around their blade axis for control purposes;

a torus-like convexly curved part rotationally symmetrical about said axis and formed on said shroud at said inlet end of said passage, said torus-like convexly curved part extending from a location substantially 1.4 r_f upstream of said blades seen radially to a location substantially 0.2 r_f downstream of said blades seen axially where r_f is a tip radius of said blades measured from said axis to a tip of the blades, said tips of said blades defining a gap with said part which is at most 1/25 of the diameter of said fan;

at least one engine operatively connected with said fan for rotating same,

said rotating blades being of airfoil cross section with the angle between the chord lines of the blades and the rotation plane of the fan blades decreasing from the hub of the fan to a radial midsection of the fan blades and increasing from the radial midsection towards the fan tip by an increment (AB) having a value in the range from 0 degrees up to 25 degrees to generate upon rotation of said fan a meridional airflow velocity through said passage which is nonuniform over the radius thereof and increases from a value proximal to said axis to a maximum at the periphery of said passage, said radial midsection of the fan blades being defined as a distance ±

0.25r_f around a means fan blade radius and as the arithmetic means between fan hub radius and fan tip radius, and

the meridional radii of curvature of said torus-like convexly curved part between said locations being 0.2r_f to 1r_f ; and

a plurality of annular inlet shields with rotational symmetry about said axis positioned above said inlet end, each of said shields being of airfoil cross section and successive ones of said shields inwardly of said torus-like convexly curved part being of successively smaller diameters, each inlet shield of a smaller diameter always overlapping an inner ring portion of the inlet shield with the next larger diameter and the inlet shield of the largest diameter overlapping said torus-like convexly curved part, whereby said shields completely cover a major portion or completely said inlet end of said passage as seen from the above.

6. The propulsion apparatus defined in claim 3 which is integrated in an aircraft nacelle, further comprising means for retracting said inlet shields axially in the direction of said torus-like convexly curved part to completely cover said passage as seen from above in a closed condition of said passage.

8. A propulsion apparatus for generating vertical lift in an aircraft, comprising:

a fan shroud defining a substantially vertical airflow passage having an axis, an upper inlet end and a lower outlet end, said passage being rotationally symmetrical about said axis but differing from a right-circular cylinder over its entire length;

a fan rotatable in said passage about said axis and having a plurality of generally radial blades where the radial axis of these blades is lying in a plane perpendicular to said axis between said inlet and outlet ends and where these fan blades can be also rotatable around their blade axis for control purposes;

a torus-like convexly curved part rotationally symmetrical about said axis and formed on said shroud at said inlet end of said passage, said torus-like convexly curved part extending from a location substantially 1.4 r_f upstream of said blades seen radially to a location substantially 0.2 r_f downstream of said blades seen axially where r_f is a tip radius of said blades measured from said axis to a tip of the blades, said tips of said blades defining a gap with said part which is at most 1/25 of the diameter of said fan; and

at least one engine operatively connected with said fan for rotating same,

said rotating blades being of airfoil cross section with the angle between the chord lines of the blades and the rotation plane of the fan blades decreasing from the hub of the fan to a radial midsection of the fan blades and increasing from the radial midsection towards the fan tip by an increment (AB) having a value in the range from 0 degrees up to 25 degrees to generate upon rotation of said fan a meridional airflow velocity through said passage which is nonuniform over the radius thereof and increases from a value proximal to said axis to a maximum at the periphery of said passage, said radial midsection of the fan blades being defined as a distance ±

0.25r_f around a means fan blade radius and as the arithmetic means between fan hub radius and fan tip radius, and

the meridional radii of curvature of said torus-like convexly curved part between said locations being 0.2r_f to 1r_f, said axis of said radial blades lying in said plane forming the first stage of a multistage axial compressor in said passage having a number of blade planes and guide vanes spaced along said axis and the airfoil-cross-section blades of which have twists changing from stage to stage and successively approaching the twist of blades of a final stage in which the chord lines include angles with said circumferential direction of rotation which decreases continuously from the blade hub to the blade tip in contrast to the first stage blading.

9. The propulsion apparatus defined in claim 8 wherein said passage is formed with a flow-accelerating nozzle leading to said outlet end.

10. In a shrouded fan of the axial compressor type, located in a flowpath contour of convex curvature and rotational symmetry within a radius of 1.4 r_f from the fan axis, r_f being the fan tip radius, the convex curvature passing the fan tip in a distance of less than 1/25 of the fan diameter, the improvement wherein:

the angle (B, in FIG.

     6) between the cross sectional chord and the rotation plane of the fan blades decreases from the hub of the fan to a radial midsection of the fan blades and increases from the radial midsection towards the fan tip by an increment (Δ

B) having a value in the range from 0 degrees up to 25 degrees to generate upon rotation of said fan a meridional airflow velocity through said flow path contour which is nonuniform over the radius thereof and increases from a value proximal to the axis of rotational symmetry of the fan to a maximum at the periphery of the flow path contour, said radial midsection of the fan blades being defined as a distance ±

0.25r_f around a mean fan blade radius and as the arithmetic means between fan hub radius and fan tip radius.

11. The improvement defined in claim 10 wherein the flowpath curvature at the fan tip has curvature radii with values between 0.2 r_f and 1.0 r_f within a range on the flowpath contour from a location 1.4 r_f radially upstream of the fan to a location 0.2 r_f axially downstream of the fan.

12. The improvement defined in claim 10 wherein the flowpath has a contour such that the most narrow diameter of the flowpath is so far downstream of the fan, that the angle of tangent to the external flowpath contour in a place, where this contour intersects the plane of the fan blade axis, is 30°

to 70°

to the blade fan.

13. The improvement defined in claim 10, further comprising inlet shields covering an air inlet of the flowpath stream of the fan along the fan axix, the shields being axially retractable in a manner that they close completely the air entrance port to the fan in retracted condition.

14. The improvement defined in claim 10, further comprising a diffuser downstream of the fan, with a circular downwardly directed trailing edge forming the end of the diffuser flowpath, and wherein said annular trailing edge is axially retractable, performing a parallel motion when being retracted.

15. The improvement defined in claim 10 which comprises a multistage axial compressor with a first stage directly surrounded by a toroidal-shaped inlet flowpath with rotational symmetry within a radius of 1.4 r_f, where said first compressor stage has the twist of the fan blades according to claim 10, the last compressor stage has a layout of radial distribution of compressor blade twist according to which the angle of incidence (α

) continuously decreases from hub to tip, and wherein all stages between first stage and last stage provide a transition of the layout of the blade twist between the first stage to the last stage.