Dovetail structure of fan

Abstract

The invention provides a dovetail structure of a fan which attaches the fan 20 having an inlet hub diameter smaller than an outlet hub diameter to a portion around a discoid disc 10 rotationally driven by a turbine. The disc 10 has a plurality of main dovetail grooves 12 extending in parallel to an axis 1 of a rotation axis from a leading edge to a trailing edge thereof. The fan 20 has a main dovetail portion 22 fitted to the main dovetail groove 12, and a sub engagement portion 24 for supporting a front centrifugal force. Further, the dovetail structure is provided with a spin cone 30 engaging with the sub engagement portion 24 so as to be capable of transmitting the front centrifugal force to the disc 10.

1 . A dovetail structure of a fan which attaches the fan having an inlet hub diameter smaller than an outlet hub diameter to a portion around a discoid disc rotationally driven by a turbine,
 wherein the disc has a plurality of main dovetail grooves extending in parallel to an axis of a rotation axis from a leading edge to a trailing edge thereof, and spaced at a fixed angle in a peripheral direction,   wherein the fan has a main dovetail portion fitted to the main dovetail groove so as to be capable of transmitting a rear centrifugal force applied to a portion from an intermediate portion to a trailing edge, and a sub engagement portion for supporting a front centrifugal force applied to a portion from a leading edge to the intermediate portion, and   wherein the dovetail structure is provided with a spin cone engaging with the sub engagement portion so as to be capable of transmitting the front centrifugal force to the disc.   
   
   
       2 . The dovetail structure of the fan as claimed in  claim 1 , wherein the fan is constituted by a zero hub ratio fan which is capable of sucking an air close to a center of rotation, and in which a substantial inlet hub diameter is zero or close to zero, and a hub/tip ratio is between 0 and 0.35. 
   
   
       3 . The dovetail structure of the fan as claimed in  claim 1 , wherein the sub engagement portion is constituted by a projection portion which is provided in an inner end portion of a forward end of the fan, and has an outer peripheral surface spaced at a fixed distance R from the axis of the rotating shaft, and
 the spin cone has a concave groove having an inner peripheral surface fitted to an outer peripheral surface of the projection portion, and a faucet portion fitted to a cylindrical inner surface provided in the disc.   
   
   
       4 . The dovetail structure of the fan as claimed in  claim 1 , wherein the sub engagement portion is constituted by a plurality of slope dovetail portions extending at a fixed angle with respect to the axis of the rotating shaft from the leading edge of the fan to the intermediate portion, and spaced at a fixed angle in a peripheral direction, and
 the spin cone has a plurality of slope dovetail grooves fitted to the slope dovetail portions, and a faucet portion fitted to the cylindrical inner surface provided in the disc.   
   
   
       5 . The dovetail structure of the fan as claimed in  claim 1 , wherein the sub engagement portion has a plurality of parallel dovetail portions extending in parallel to the axis of the rotating shaft from the leading edge of the fan to the intermediate portion, and spaced at a fixed angle in a peripheral direction, and
 the spin cone has a plurality of parallel dovetail grooves fitted to the parallel dovetail portions, and a faucet portion fitted to the cylindrical inner surface provided in the disc.   
   
   
       6 . The dovetail structure of the fan as claimed in  claim 1 , wherein the sub engagement portion is constituted by a plurality of expanded portions extending from the leading edge of the fan to the intermediate portion and spaced at a fixed angle in a peripheral direction, and
 the spin cone has a plurality of fitting grooves fitted to a front lower edge of the fan in an upper portion than the expanded portions, and a faucet portion fitted to the cylindrical inner surface provided in the disc.