Fan rotor for air cycle machine

1. A fan rotor comprising:

a rotor body having a plurality of fan blades for rotation about a central axis and a radially inwardly extending annular wall; and

a hub body extending axially from the annular wall and defining a central hub bore with a hub bore diameter D b , the hub body further defining a first cylindrical hub portion around the central hub bore on one axial side of the annular wall and a second cylindrical hub portion around the central hub bore on an opposite axial side of the annular wall, the first cylindrical hub portion defining a first outer diameter D 1 and the second cylindrical hub portion defining a second outer diameter D 2 , where a ratio D 1 /D b is 1.996-2.007 and a ratio D 2 /D b is 2.051-2.063;

wherein the hub body includes a first circumferential groove located between the first cylindrical hub portion and the annular wall, and a second circumferential groove located between the second cylindrical hub portion and the annular wall.

2. The fan rotor as recited in claim 1 , wherein each of the first circumferential groove and the second circumferential groove define a radius of curvature R c and meet an outer peripheral surface of the respective first cylindrical hub portion or second cylindrical hub portion at a complimentary angle alpha (α) such that a ratio alpha/R c is 1055-1378 degrees per inch.

3. The fan rotor as recited in claim 1 , wherein the first circumferential groove and the second circumferential groove each have a semi-circular cross-section.

4. The fan rotor as recited in claim 1 , wherein the first cylindrical hub portion includes a chamfer.

5. The fan rotor as recited in claim 1 , wherein the rotor body includes an axially extending wall having a cylindrical outer surface and defining a non-uniform radial thickness.

6. The fan rotor as recited in claim 1 , wherein the rotor body defines a first rotor body portion that extends axially at a radially outer end of the annular wall.

7. An air cycle machine comprising:

a main shaft having a compressor rotor and a turbine rotor mounted for rotation thereon;

a thrust shaft mounted on the main shaft, the thrust shaft having a shaft body defining a disk at a first end and a cylindrical shaft portion extending from the disk to a second end, the shaft body having a shaft bore defining a shaft bore diameter D s ; and

a fan rotor mounted on the cylindrical shaft portion and including:

a rotor body having a plurality of fan blades for rotation about a central axis and a radially inwardly extending annular wall; and

a hub body extending axially from the annular wall and defining a central hub bore with a hub bore diameter D b , the hub body further defining a first cylindrical hub portion around the central hub bore on one axial side of the annular wall which is received into the shaft bore of the thrust shaft and a second cylindrical hub portion around the central hub bore on an opposite axial side of the annular wall, the first cylindrical hub portion defining a first outer diameter D 1 such that a ratio D 1 /D s is 1.002-1.007;

wherein the hub body includes a first circumferential groove located between the first cylindrical hub portion and the annular wall, and a second circumferential groove located between the second cylindrical hub portion and the annular wall.

8. The air cycle machine as recited in claim 7 , further comprising a fan rotor ring that is mounted over the second cylindrical hub portion of the hub body, the fan rotor ring having a fan ring bore with a fan ring bore diameter D R2 , and the second cylindrical hub portion defining a second outer diameter D 2 such that a ratio D 2 /D R2 is 1.002-1.007.

9. The air cycle machine as recited in claim 7 , wherein the second cylindrical hub portion defines a second outer diameter D 2 such that D 2 /D b is 2.051-2.063.

10. The air cycle machine as recited in claim 7 , wherein a ratio D 1 /D b is 1.996-2.007.

11. The air cycle machine as recited in claim 7 , wherein each of the first circumferential groove and the second circumferential groove define a radius of curvature R c and meet an outer peripheral surface of the respective first cylindrical hub portion or second cylindrical hub portion at a complimentary angle alpha (α) such that a ratio alpha/R c is 1055-1378 degrees per inch.

12. The air cycle machine as recited in claim 7 , wherein the first circumferential groove and the second circumferential groove each have a semi-circular cross-section.

13. A method of installing a fan rotor on an air cycle machine, the method comprising:

extending a main shaft having a compressor rotor and a turbine rotor mounted for rotation thereon through a central hub bore of a fan rotor that includes:

a rotor body having a plurality of fan blades for rotation about a central axis and a radially inwardly extending annular wall; and

a hub body extending axially from the annular wall and defining the central hub bore with a hub bore diameter D b , the hub body further defining a first cylindrical hub portion around the central hub bore on one axial side of the annular wall and a second cylindrical hub portion around the central hub bore on an opposite axial side of the annular wall, the first cylindrical hub portion defining a first outer diameter D 1 and the second cylindrical portion defining a second outer diameter D 2 ;

inserting the first cylindrical hub portion of the fan rotor into a shaft bore of a cylindrical shaft portion of a thrust shaft that is mounted on the main shaft, the thrust shaft having a shaft body defining a disk at a first end and the cylindrical shaft portion extending from the disk to a second end, the shaft bore having a shaft bore diameter D s such that a ratio D 1 /D s is 1.002-1.007;

securing a nut on the main shaft to secure the main shaft, thrust shaft, and fan rotor together for co-rotation with the compressor rotor and the turbine rotor;

wherein the hub body includes a first circumferential groove located between the first cylindrical hub portion and the annular wall, and a second circumferential groove located between the second cylindrical hub portion and the annular wall.

14. The method as recited in claim 13 , further comprising, prior to securing the nut on the main shaft, inserting a fan rotor ring on the fan rotor by inserting the second cylindrical hub portion of the hub body into a fan ring bore of the fan rotor ring, the fan ring bore having a fan ring bore diameter D R2 such that a ratio D 2 /D R2 is 1.002-1.007.

15. The method as recited in claim 13 , wherein each of the first circumferential groove and the second circumferential groove define a radius of curvature R c and meet an outer peripheral surface of the respective first cylindrical hub portion or second cylindrical hub portion at a complimentary angle alpha (α) such that a ratio alpha/R c is 1055-1378 degrees per inch.

16. The method as recited in claim 13 , wherein the first circumferential groove and the second circumferential groove each have a semi-circular cross-section.