Turbomachine having inner and outer fans with hub-tip ratios
An axial flow turbomachine ( 102 ) for producing thrust to propel an aircraft is shown. The turbomachine has an inner duct ( 202 ) and an outer duct ( 204 ), both of which are annular and concentric with one another. An inner fan ( 206 ) is located in the inner duct, and is configured to produce a primary pressurised flow (P). An outer fan ( 207 ) is located in an outer duct, and is configured to produce a secondary pressurised flow (S). The outer fan has a hollow hub ( 208 ) through which the inner duct passes. A hub-tip ratio of the outer fan is from 1.6 to 2.2 times a hub-tip ratio of the inner fan.
1. An axial flow turbomachine for producing thrust to propel an aircraft, comprising:
an inner duct and an outer duct, both of which are annular and concentric with one another;
an inner fan located in the inner duct, the inner fan being configured to produce a primary pressurized flow;
an outer fan located in the outer duct, the outer fan being configured to produce a secondary pressurized flow and having a hollow hub through which the inner duct passes,
a first electric machine configured to drive the inner fan, the first electric machine having a rotor integral with a hub of the inner fan and a stator located radially inward of the rotor,
wherein a hub-tip ratio of the outer fan is from 1.6 to 2.2 times a hub-tip ratio of the inner fan,
wherein, in operation, the primary pressurized flow and the secondary pressurized flow exit respective ones of the inner and outer ducts, whereupon the secondary pressurized flow substantially shrouds the primary pressurized flow,
wherein a second electric machine is configured to drive the outer fan, the second electric machine having a rotor integral with the hub of the outer fan and a stator located radially inward of the rotor and radially outward of the inner duct,
wherein a trailing edge of the outer duct is located axially downstream of the inner duct for mixing of the first and secondary pressurized flows, and
wherein the outer fan has a diameter of from 2.5 to 3.5 times a diameter of the inner fan.
2. The turbomachine of claim 1 , wherein the hub-tip ratio of the outer fan is from 1.6 to 2.0 times the hub-tip ratio of the inner fan.
3. The turbomachine of claim 1 , wherein the hub-tip ratio of the outer fan is from 1.6 to 1.8 times the hub-tip ratio of the inner fan.
4. The turbomachine of claim 1 , wherein the hub-tip ratio of the outer fan is 0.4, and the hub-tip ratio of the inner fan is 0.25.
5. The turbomachine of claim 1 , in which the inner fan is configured to rotate counter to the outer fan.
6. The turbomachine of claim 1 , wherein the inner fan is configured to rotate at a rate greater than the outer fan.
7. The turbomachine of claim 1 , wherein the inner fan and the outer fan partially or fully overlap in an axial direction.
8. The turbomachine of claim 1 , wherein a swept area of the outer fan is from 2 to 20 times greater than a swept area of the inner fan.
9. The turbomachine of claim 1 , wherein a swept area of the outer fan is from 7.5 to 13 times greater than a swept area of the inner fan.
10. The turbomachine of claim 1 , wherein the outer fan has a diameter of from 2.8 to 3.3 times a diameter of the inner fan.
11. The turbomachine of claim 1 , wherein the inner fan is configured to have, in operation, a tip speed of from 1 to 3 times that of the outer fan.
12. The turbomachine of claim 1 , wherein the inner fan is configured to have, in operation, a tip speed of from 1.3 to 2.5 times that of the outer fan.
13. The turbomachine of claim 1 , wherein the inner fan is configured to have, in operation, a rate of rotation of from 3 to 8 times that of the outer fan.
14. An aircraft comprising one or more turbomachine according to claim 1 .