Gas turbine engine

Abstract

A gas turbine engine for an aircraft comprises: an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan comprising a plurality of fan blades; a bypass duct delimited by a bypass duct inner wall and a bypass duct outer wall and located radially outwardly from the engine core and downstream of the fan; and an outlet guide vane assembly, located within the bypass duct and, comprising a plurality of outlet guide vanes distributed circumferentially within the bypass duct, each outlet guide vane extending radially along a span between the bypass duct inner wall and the bypass duct outer wall, wherein a space-chord ratio of at least one outlet guide vane, at 50% of the span length from the bypass duct inner wall, is less than 0.72.

We claim: 
     
         1 . A gas turbine engine for an aircraft comprising:
 an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;   a fan located upstream of the engine core, the fan comprising a plurality of fan blades;   a bypass duct delimited by a bypass duct inner wall and a bypass duct outer wall and located radially outwardly from the engine core and downstream of the fan; and   an outlet guide vane assembly, located within the bypass duct and, comprising a plurality of outlet guide vanes distributed circumferentially within the bypass duct, each outlet guide vane extending radially along a span between the bypass duct inner wall and the bypass duct outer wall,   wherein a space-chord ratio of at least one outlet guide vane of the plurality of outlet guide vanes, at 50% of the span length from the bypass duct inner wall, is less than 0.72, and the space-chord ratio of the at least one outlet guide vane, at 70% of the span length from the bypass duct inner wall is more than 0.60,   wherein the space-chord ratio is defined by an average spacing of the outlet guide vanes at a respective span height divided by a true chord length of the at least one outlet guide vane at the respective span height, wherein the average spacing of outlet guide vanes at the respective span height is defined as a circumference of the bypass duct at the respective span height (2πr, where r is a radius at the respective span height from a principal rotational axis of the gas turbine engine) divided by the number of outlet guide vanes (N V ), (2πr/N V ).   
     
     
         2 . The gas turbine engine according to  claim 1 , wherein the space-chord ratio (s/c) of the at least one outlet guide vane at 70% of the span length from the bypass duct inner wall is more than 0.62. 
     
     
         3 . The gas turbine engine according to  claim 1 , wherein at a point from 65% to 70% of the span length from the bypass duct inner wall, the space-chord ratio of the at least one outlet guide vane is more than 0.60. 
     
     
         4 . The gas turbine engine according to  claim 1 , wherein at a point from 65% to 70% of the span length from the bypass duct inner wall the space-chord ratio (s/c) of the at least one outlet guide vane is less than 0.79. 
     
     
         5 . The gas turbine engine according to  claim 1 , wherein at every point from 65% to 70% of the span length from the bypass duct inner wall the space-chord ratio of the at least one outlet guide vane is in the range of from 0.62 to 0.79. 
     
     
         6 . The gas turbine engine according to  claim 1 , wherein at every point from 65% to 70% of the span length from the bypass duct inner wall the space-chord ratio of the at least one outlet guide vane is in the range of from 0.66 to 0.79. 
     
     
         7 . The gas turbine engine according to  claim 6 , wherein the fan has a fan diameter greater than 210 cm and a bypass ratio greater than 11.5 at cruise conditions. 
     
     
         8 . The gas turbine engine according to  claim 7 , wherein an overall pressure ratio is greater than 40 at cruise conditions. 
     
     
         9 . The gas turbine engine according to  claim 1 , wherein the fan has a fan diameter greater than 210 cm, a bypass ratio greater than 12.5 at cruise conditions, and a bypass ratio greater than 45 at the cruise conditions. 
     
     
         10 . The gas turbine engine according to  claim 1 , further comprising:
 a gearbox configured to receive an input from the core shaft and output drive to the fan so as to drive the fan at a lower rotational speed than the core shaft, wherein the gearbox has a gear ratio of at least 3.5.   
     
     
         11 . A gas turbine engine for an aircraft comprising:
 an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;   a fan located upstream of the engine core, the fan comprising a plurality of fan blades;   a bypass duct delimited by a bypass duct inner wall and a bypass duct outer wall and located radially outwardly from the engine core and downstream of the fan; and   an outlet guide vane assembly, located within the bypass duct and, comprising a plurality of outlet guide vanes distributed circumferentially within the bypass duct, each outlet guide vane extending radially along a span between the bypass duct inner wall and the bypass duct outer wall,   wherein a space-chord ratio of at least one outlet guide vane of the plurality of outlet guide vanes, at a point from 65% to 70% of the span length from the bypass duct inner wall, is more than 0.62,   wherein the space-chord ratio is defined by an average spacing of the outlet guide vanes at a respective span height divided by a true chord length of the at least one outlet guide vane at the respective span height, wherein the average spacing of outlet guide vanes at the respective span height is defined as a circumference of the bypass duct at the respective span height (2πr, where r is a radius at the respective span height from a principal rotational axis of the gas turbine engine) divided by the number of outlet guide vanes (N V ), (2πr/N V ).   
     
     
         12 . The gas turbine engine according to  claim 11 , wherein the space-chord ratio of the at least one outlet guide vane, at a point from 65% to 70% of the span length from the bypass duct inner wall, is more than 0.64. 
     
     
         13 . The gas turbine engine according to  claim 12 , wherein the space-chord ratio of the at least one outlet guide vane, at a point from 65% to 70% of the span length from the bypass duct inner wall, is more than 0.66 and less than 0.79. 
     
     
         14 . The gas turbine engine according to  claim 11 , wherein the space-chord ratio of the at least one outlet guide vane, at 50% of the span length from the bypass duct inner wall is less than 0.62. 
     
     
         15 . The gas turbine engine according to  claim 11 , wherein the space-chord ratio of the at least one outlet guide vane, at 50% of the span length from the bypass duct inner wall is more than 0.57. 
     
     
         16 . The gas turbine engine according to  claim 11 , wherein the space-chord ratio of the at least one outlet guide vane, at 70% of the span length from the bypass duct inner wall is more than 0.59. 
     
     
         17 . The gas turbine engine according to  claim 16 , wherein the space-chord ratio of the at least one outlet guide vane, at 70% of the span length from the bypass duct inner wall is more than 0.6. 
     
     
         18 . The gas turbine engine according to  claim 11 , wherein the space-chord ratio of the at least one outlet guide vane, at every point from 65% to 70% of the span length from the bypass duct inner wall, is less than 0.79. 
     
     
         19 . The gas turbine engine according to  claim 11 , wherein the fan has a fan diameter greater than 210 cm and the fan blades have a fan-to-tip ratio in a range of from 0.25 to 0.4. 
     
     
         20 . The gas turbine engine according to  claim 19 , wherein the fan-to-tip ratio is in a range of from 0.28 to 0.33, and optionally in the range of from 0.30 to 0.33.