Aircraft engine with stator having varying pitch
An aircraft engine, has: an upstream stator having upstream stator vanes circumferentially distributed about a central axis; and a downstream stator having downstream stator vanes circumferentially distributed about the central axis, the downstream stator located downstream of the upstream stator relative to an airflow flowing within a core gaspath of the aircraft engine, a number of the upstream stator vanes being different than a number of the downstream stator vanes, major portions of leading edges of the downstream stator vanes circumferentially overlapped by the upstream stator vanes, the downstream stator vanes including: a first pair of circumferentially adjacent vanes of the downstream stator vanes spaced apart by a first pitch, and a second pair of circumferentially adjacent vanes of the downstream stator vanes spaced apart by a second pitch different than the first pitch.
1 . A method of manufacturing a downstream stator of a stator assembly, the stator assembly including an upstream stator and the downstream stator located downstream of the upstream stator, the method comprising:
determining exposures of leading edges of vanes of the downstream stator to spacing defined between vanes of the upstream stator such that the vanes of the downstream stator would be susceptible to foreign object damage if installed at baseline vane positions separated from each other by a first pitch being constant, the vanes of the downstream stator and the vanes of the upstream stator defining a non-zero angle between a central axis of the stator assembly and chords of the vanes of the downstream stator and chords of the vanes of the upstream stator;
for a first vane of the vanes of the downstream stator for which a corresponding first exposure of the exposures is less than a threshold, maintaining the first vane at a corresponding first baseline vane position of the baseline vane positions; and
for a second vane of the vanes of the downstream stator for which a corresponding second exposure of the exposures is greater than or equal to the threshold, offsetting the second vane from a corresponding second baseline vane position of the baseline vane positions such that a modified exposure of the second vane to the spacing defined between the vanes of the upstream stator is less than the threshold.
2 . The method of claim 1 , wherein the offsetting of the second vane from the corresponding second baseline vane position includes:
determining a second pitch between the second vane and a circumferentially adjacent one of the downstream stator vanes as a function of the second exposure.
3 . The method of claim 2 , wherein the determining of the second pitch includes separating the two vanes by the second pitch, wherein a ratio of the first pitch to the second pitch ranges from 1:1 to 1:10.
4 . The method of claim 1 , wherein the determining of the includes determining circumferential positions where the vanes of the downstream stator would be visible via the spacing defined between the vanes of the upstream stator along a line of sight being parallel to a central axis of the downstream stator.
5 . The method of claim 1 , wherein the determining of the exposures includes determining circumferential positions where major portions of the leading edges of the downstream stator would be visible via the spacing.
6 . The method of claim 5 , wherein the major portions include tip sections of the vanes.
7 . The method of claim 5 , wherein the major portions include radially-outer portions of the vanes.
8 . The method of claim 1 , wherein all of the downstream stator vanes are identical to one another.
9 . The method of claim 1 , comprising disposing the downstream stator vanes around a central axis of the downstream stator such that circumferential overlaps defined between the upstream stator vanes and leading edges of the downstream stator vanes are non-uniform around the central axis.
10 . A method of manufacturing a downstream stator of a stator assembly, the stator assembly including an upstream stator and the downstream stator located downstream of the upstream stator, the method comprising:
identifying circumferential locations being visible through spacing defined between each two adjacent ones of vanes of the upstream stator and along a line of sight being parallel to a central axis of the stator assembly; and
disposing vanes of the downstream stator around the central axis such that portions of leading edges of the vanes of the downstream stator are circumferentially offset from the circumferential locations to maintain exposures of the leading edges of the vanes of the downstream stator below a threshold above which the vanes of the downstream staior are susceptible to foreign object damage, the vanes of the downstream stator and the vanes of the upstream stator defining a non-zero angle between the central axis and chords of the vanes of the downstream stator and chords of the vanes of the upstream stator.
11 . The method of claim 10 , wherein the disposing of the vanes includes disposing the vanes of the downstream stator such that major portions of the leading edges are circumferentially offset from the circumferential locations.
12 . The method of claim 11 , wherein the major portions include tip sections of the vanes.
13 . The method of claim 11 , wherein the major portions include radially-outer portions of the vanes.
14 . The method of claim 10 , wherein the disposing of the vanes includes:
disposing a first vane adjacent a second vane, the first vane being spaced apart from the second vane by a first pitch;
determining that a third vane disposed adjacent the second vane and spaced apart from the second vane by the first pitch would be in register with one of the spacing between the vanes of the upstream stator; and
disposing the third vane adjacent the second vane and spaced apart from the second vane by a second pitch different than the first pitch.
15 . The method of claim 14 , wherein the disposing of the third vane includes separating the third vane from the second vane by a second spacing, wherein a ratio of the first pitch to the second pitch ranges from 1:1 to 1:10.
16 . The method of claim 10 , wherein all of the vanes of the downstream stator are identical to one another.
17 . The method of claim 10 , comprising disposing the downstream stator vanes around the central axis of the downstream stator such that circumferential overlaps defined between the upstream stator vanes and leading edges of the downstream stator vanes are non-uniform around the central axis.