The application relates generally to aircraft engines and, more particularly, to systems and methods used to protect airfoils of such engines from foreign object damage.
In certain operating conditions, aircraft engines, such as turbofan engines, may be subjected to foreign object damage (FOD). FOD may occur when a foreign object (e.g., ice) is ingested by the engine and damages an airfoil of a rotor or a stator. The damaged airfoil is typically impacted at its leading edge. This may result in performance loss, imbalance, and so on. Improvements are therefore sought.
In one aspect, there is provided an aircraft engine, comprising: 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.
The aircraft engine may include any of the following features, in any combinations.
In some embodiments, the major portions of the leading edges include at least 50% of spans of the downstream stator vanes.
In some embodiments, the major portions include tip sections.
In some embodiments, the major portions are radially-outer portions.
In some embodiments, all of the downstream stator vanes are identical.
In some embodiments, the downstream stator includes baseline vane positions each associated with a respective one of the downstream stator vanes, the baseline vane positions separated from each other by a baseline pitch being constant, each vane of the first pair of circumferentially adjacent vanes of the first pair aligned with a respective one of the baseline vane positions, each vane of the second pair of circumferentially adjacent vanes being circumferentially offset from a respective one of the baseline vane positions.
In some embodiments, a ratio of the first pitch to the second pitch ranges from 1:1 to 1.10.
In some embodiments, the downstream stator includes baseline vane positions each associated with a respective one of the downstream stator vanes, a zone where major portions of baseline leading edges of the baseline vane positions are visible via spacing defined between the upstream stator vanes, the second pair of circumferentially adjacent vanes located within the zone.
In some embodiments, the zone includes a plurality of zones distributed around the central axis, the downstream stator vanes located within the zones being separated from each other by the second pitch, the downstream stator vanes located outside the zones being separated from each other by the first pitch.
In another aspect, there is provided a stator assembly, comprising: 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 through the stator assembly, 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.
The stator assembly may include any of the following features, in any combinations.
In some embodiments, the major portions of the leading edges include at least 50% of spans of the downstream stator vanes.
In some embodiments, the major portions include tip sections.
In some embodiments, the major portions are radially-outer portions.
In some embodiments, all of the downstream stator vanes are identical.
In some embodiments, the downstream stator includes baseline vane positions each associated with a respective one of the downstream stator vanes, the baseline vane positions separated from each other by a baseline pitch being constant, each of the first pair of circumferentially adjacent vanes of the first pair aligned with a respective one of the baseline vane positions, each vane of the second pair of circumferentially adjacent vanes being circumferentially offset from a respective one of the baseline vane positions.
In some embodiments, a ratio of the first pitch to the second pitch ranges from 1:1 to 1:10.
In some embodiments, the downstream stator includes baseline vane positions each associated with a respective one of the downstream stator vanes, a zone where major portions of baseline leading edges of the baseline vane positions are visible via spacing defined between the upstream stator vanes, the second pair of circumferentially adjacent vanes located within the zone.
In some embodiments, the zone includes a plurality of zones distributed around the central axis, the downstream stator vanes located within the zones being separated from each other by the second pitch, the downstream stator vanes located outside the zones being separated from each other by the first pitch.
In yet another aspect, there is provided 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 a circumferential position where vanes of the downstream stator would be susceptible to foreign object damage via spacing defined between vanes of the upstream stator if installed at baseline vane positions separated from each other by a first pitch being constant; outside the circumferential position, separating the downstream stator vanes by the first pitch; and within the circumferential position, separating two vanes of the downstream stator vanes by a second pitch different than the first pitch such that major portions of leading edges of the downstream stator vanes are overlapped by the upstream stator vanes.
The method may include any of the following features, in any combinations.
In some embodiments, the separating of the two vanes by the second pitch includes, for a vane of the downstream stator vanes located within the circumferential position: determining an exposure of a leading edge of the vane if the vane were installed at a corresponding baseline vane position; and determining the second pitch between the vane and a circumferentially adjacent one of the downstream stator vanes as a function of the exposure to ensure that the major portion of the leading edge of the vane is circumferentially overlapped by one of the upstream stator vanes.
Reference is now made to the accompanying figures in which:
Although illustrated as a turbofan engine, the gas turbine engine 10 may alternatively be another type of engine, for example a turboshaft engine, also generally comprising in serial flow communication a compressor section, a combustor, and a turbine section, and a fan through which ambient air is propelled. A turboprop engine may also apply. In addition, although the engine 10 is described herein for flight applications, it should be understood that other uses, such as industrial or the like, may apply. The engine may have one or more spools.
Still referring to
For the remainder of the present disclosure, the fan stator 23 will be referred to as an upstream stator 30 and the first stator 14C of the low-pressure compressor 14B will be referred to as a downstream stator 40. It will be understood that the principles of the present disclosure may apply to any combinations of two stators in serial flow communication with each other. These two stators may be located at any suitable locations along the core gaspath 24. Any pair of stators may benefit from the present disclosure.
Referring now to
A number of the upstream stator vanes 31 may be different (e.g., more, less) than a number of the downstream stator vanes 41. The number of the upstream stator vanes 31 may not be a multiple of the number of the downstream stator vanes 41 or vice-versa. Consequently, some of the downstream stator vanes 41 may be visible via spacing 32 defined between circumferentially adjacent upstream stator vanes 31. As shown in
The sensitive areas of the downstream stator vanes 41 may correspond to leading edges of the downstream stator vanes 41. In some cases, the sensitive areas may correspond to the trailing edges. The thinner areas of the airfoils may correspond to the sensitive areas. More specifically, tip sections of the leading edges of the downstream stator vanes 41 may be particularly prone to FOD. Herein, the expression tip sections of the leading edges may include a radially-outer 50% of a span of the leading edges of the downstream stator vanes 41. In some cases, the tip sections includes a radially-outer 40%, or a radially-outer 30% in some cases, of the span. In some cases, the outer section of the span may include from 40% to 50% of the span. It may include all of the span in some cases. In some embodiments, base sections of the downstream stator vanes 41 may be the sensitive areas; the base sections extending from 0% to 50% span from the radially-inner ends. In some other cases, the tip sections includes a radially-outer 20% of the span. The tip sections of the leading edges of the downstream stator vanes 41 may be more sensitive to FOD because the downstream stator vanes 41 may decrease in both chord and thickness towards tips of the downstream stator vanes 41. This, in turn, may result in the tip sections of the downstream stator vanes 41 less stiff than a remainder of the downstream stator vanes 41 and, consequently, more susceptible to FOD. In some embodiments, the thickness distribution of the vane is constant along their spans. In the embodiment shown, the exposed part of the vanes is increasing from inner ends to outer ends. In this case, for the lower part, only small ice pellet may impact. For the higher part bigger ice pellets may impact. Small ice pellets may have less energy and may make less damage than bigger ice pellets closer to the tip. This may be engine-dependent. Some engine will fly at low speed and may be susceptible to FOD near the tip. Some other engine will fly much faster and may be susceptible to FOD closer to the radially inner ends of the vane. Small ice pellet at high speed might cause more damage than big pellets at low speed.
Still referring to
Still referring to
In the embodiment shown, to at least partially alleviate the risk of FOD of the second vanes 43, the pitch between the downstream stator vanes 41 may be varied such that the downstream stator vanes that would otherwise be exposed to FOD are now shielded by the upstream stator vanes 31.
Referring now to
As illustrated in
As shown in
The downstream stator vanes 41 may all be identical whether they belong to the first pair 44 or the second pair 45. In other words, the downstream stator vanes 41 may all have airfoils having the same geometry (e.g., camber, stagger, chord, span, curvature, etc) and made of the same material (e.g., aluminum).
As shown in
Each of the downstream stator vanes 41 may be associated with a baseline vane position BL. The baseline vane positions are separated from each other by a baseline pitch being constant. This baseline pitch may correspond to the first pitch P1. Each of the downstream stator vanes of the first pair 44 is aligned with a respective one of the baseline vane positions. At least one of the vanes 41 of the second pair 45 is circumferentially offset from a respective one of the baseline vane positions.
Stated differently, the downstream stator 40 has a zone where major portions of baseline leading edges 41A′ of the baseline vane positions BL are visible via the spacing 32 defined between the upstream stator vanes 31. The second pair 45 of the downstream stator vanes 41 may be located within this zone. As shown in
In some embodiments, the downstream stator 40 may be a segmented ring including a plurality of segments circumferentially distributed about the central axis 11. First segments of the plurality of segments may include downstream stator vanes 41 separated from one another by the first pitch P1. Second segments of the plurality of segments may include downstream stator vanes 41 separated from one another by the second pitch P2, or by many different pitches. The first segments may be located between (i.e., outside) the zones of high FOD risk whereas the second segments may be located within the zones of high FOD risk.
Referring now to
In some embodiments, the separating of the two vanes by the second pitch at 406 includes, for a vane 41 of the downstream stator vanes 41 located within the circumferential position: determining an exposure of the leading edge 41A of the vane 41 if the vane were installed at a corresponding baseline vane position BL; and determining the second pitch P2 between the vane 41 and a circumferentially adjacent one of the downstream stator vanes 41 as a function of the exposure to ensure that the major portion of the leading edge 41A of the vane 41 is circumferentially overlapped by one of the upstream stator vanes 31.
The determining of the exposure may be done by plotting a graph as shown in
Referring to
The graph in
Still referring to
In some embodiments, the upstream stator vanes 31 may have non-constant pitch to protect the downstream stator vanes 41. Both of the upstream and downstream stator vanes 31, 41 may be disposed at different pitches to shield the downstream stator vanes 41 from FOD. In other words, the upstream stator vanes 31 may be distributed at different pitches to help protect the downstream stator vanes 41 from FOD.
By changing the pitch of the exposed airfoils or optimizing the overall configuration, the exposure may be reduced, and overall high-performance thinner airfoils may be used all around the downstream stator 40. With this change in pitch, it may not be required to redesign any of the vanes 41. The different pitches may help in mistuning dynamic excitation of the rotors disposed between the upstream and downstream stators.
Herein, the expression “about” implies variations of plus or minus 10%.
The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the present technology. Yet further modifications could be implemented by a person of ordinary skill in the art in view of the present disclosure, which modifications would be within the scope of the present technology.
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