Fan assembly

Abstract

A fan assembly includes a first fan adapted to rotate in a first direction and a second fan adapted to rotate in a second direction opposite to the first direction. The first fan includes a shroud having an inner surface defining a flow chamber, and a plurality of first blades arranged circularly around a central axis of the first fan and extending radially inwardly from the shroud towards the central axis of the first fan. Each of the plurality of first blades is arranged inside the flow chamber and includes an outer edge connected to the inner surface of the shroud. The second fan has a plurality of second blades arranged inside the flow chamber and coaxially to the plurality of first blades. The second fan is arranged upstream or downstream of the first fan.

What is claimed is: 
     
         1 . A fan assembly, comprising:
 a first fan configured to rotate in a first direction and including
 a shroud having an inner surface defining a flow chamber, and 
 a plurality of first blades arranged circularly around a central axis of the first fan and extending radially inwardly from the shroud towards the central axis of the first fan, wherein each of the plurality of first blades is arranged inside the flow chamber and includes an outer edge connected to the inner surface of the shroud; and 
   a second fan configured to rotate in a second direction opposite to the first direction and having a plurality of second blades arranged inside the flow chamber and coaxially to the plurality of first blades, wherein the second fan is arranged upstream or downstream of the first fan.   
     
     
         2 . The fan assembly of  claim 1 , wherein the second fan includes a ring circumferentially surrounding the plurality of second blades such that tips of the second blades are engaged with an inner surface of the ring, wherein the ring is arranged inside the flow chamber defining a radial gap therebetween. 
     
     
         3 . The fan assembly of  claim 2  further including a drive assembly arranged inside the radial gap and configured to rotate the first fan and the second fan. 
     
     
         4 . The fan assembly of  claim 1  further including a gearbox arranged inside the flow chamber and operatively connecting the first fan to the second fan to rotate the second fan. 
     
     
         5 . The fan assembly of  claim 4  further including a motor arranged substantially centrally to the first fan and configured to rotate the first fan. 
     
     
         6 . The fan assembly of  claim 4  further including a drive mechanism having a motor arranged outside the shroud and operatively coupled to the shroud to rotate the first fan. 
     
     
         7 . The fan assembly of  claim 1 , wherein the first fan and the second fan are rotated independently of each other. 
     
     
         8 . A heat transfer system, comprising:
 a heat exchanger; and   a fan assembly arranged upstream or downstream of the heat exchanger to facilitate a flow of air through the heat exchanger, wherein the fan assembly is configured to direct the air to the heat exchanger in a substantially axial direction, the fan assembly includes
 a first fan configured to rotate in a first direction and including
 a shroud having an inner surface defining a flow chamber, and 
 a plurality of first blades arranged circularly around a central axis of the first fan and extending radially inwardly from the shroud towards the central axis of the first fan, wherein each of the plurality of first blades is arranged inside the flow chamber and includes an outer edge connected to the inner surface of the shroud, and 
 
 a second fan configured to rotate in a second direction opposite to the first direction and having a plurality of second blades arranged inside the flow chamber and coaxially to the plurality of first blades, wherein the second fan is arranged upstream or downstream of the first fan. 
   
     
     
         9 . The heat transfer system of  claim 8 , wherein the second fan includes a ring circumferentially surrounding the plurality of second blades such that tips of the second blades are engaged with an inner surface of the ring, wherein the ring is arranged inside the flow chamber defining a radial gap therebetween. 
     
     
         10 . The heat transfer system of  claim 9 , wherein the fan assembly includes a drive assembly arranged inside the radial gap and configured to rotate the first fan and the second fan. 
     
     
         11 . The heat transfer system of  claim 8 , wherein the fan assembly includes a gearbox arranged inside the flow chamber and operatively connecting the first fan to the second fan to rotate the second fan. 
     
     
         12 . The heat transfer system of  claim 11 , wherein the fan assembly includes a motor arranged substantially centrally to the first fan and configured to rotate the first fan. 
     
     
         13 . The heat transfer system of  claim 11 , wherein the fan assembly includes a drive mechanism having a motor arranged outside the shroud and operatively coupled to the shroud to rotate the first fan. 
     
     
         14 . The heat transfer system of  claim 8 , wherein the first fan and the second fan are rotated independently of each other. 
     
     
         15 . A propulsion system, comprising:
 a power source for generating power; and   a fan assembly configured to direct a flow of air in a substantially axial direction, the fan assembly includes
 a first fan configured to rotate in a first direction and including
 a shroud having an inner surface defining a flow chamber, and 
 a plurality of first blades arranged circularly around a central axis of the first fan and extending radially inwardly from the shroud towards the central axis of the first fan, wherein each of the plurality of first blades is arranged inside the flow chamber and includes an outer edge connected to the inner surface of the shroud, and 
 
 a second fan configured to rotate in a second direction opposite to the first direction and having a plurality of second blades arranged inside the flow chamber and coaxially to the plurality of first blades, wherein the second fan is arranged upstream or downstream of the first fan. 
   
     
     
         16 . The propulsion system of  claim 15 , wherein the second fan includes a ring circumferentially surrounding the plurality of second blades such that tips of the second blades are engaged with an inner surface of the ring, wherein the ring is arranged inside the flow chamber defining a radial gap therebetween. 
     
     
         17 . The propulsion system of  claim 16 , wherein the fan assembly includes a drive assembly arranged inside the radial gap and configured to rotate the first fan and the second fan. 
     
     
         18 . The propulsion system of  claim 15 , wherein the fan assembly includes a gearbox arranged inside the flow chamber and operatively connecting the first fan to the second fan to rotate the second fan. 
     
     
         19 . The propulsion system of  claim 18 , wherein the fan assembly includes a motor arranged substantially centrally to the first fan and configured to rotate the first fan. 
     
     
         20 . The propulsion system of  claim 18 , wherein the fan assembly includes a drive mechanism having a motor arranged outside the shroud and operatively coupled to the shroud to rotate the first fan.