JP6001330B2 - Inner peripheral surface shape of casing of axial flow compressor - Google Patents

Description

  The present invention relates to the shape of the inner peripheral surface of a casing that surrounds the outer periphery of a vane of a stator that is radially arranged on the downstream side of a rotor of an axial-flow compressor.

  The shape of the inner peripheral surface (chip-side peripheral surface) of the fan casing that surrounds the outer periphery of the fan stator of the turbofan engine is formed in a substantially cylindrical shape centering on the shaft. The shape of the line that intersects the inner peripheral surface of the casing is often a straight line. Further, the stator vanes of the fan stator of the turbofan engine may be swept backward from the hub side toward the tip side in order to reduce shock wave loss and noise.

  In Patent Document 1 below, the bus bar shape of the inner peripheral surface of the fan casing surrounding the outer periphery of the inlet guide vane (stator vane) of the turbine has outer peripheral convex portions Cv2 and Cv4 directed radially inward on the upstream side, and on the downstream side. It is described that the outer peripheral recesses Cc2 and Cc4 directed radially outward are provided to suppress the pressure flow by suppressing the secondary flow radially inward from the tip side toward the hub side.

  Further, in Patent Document 2 described below, the bus bar shape of the inner peripheral surface of the casing surrounding the outer periphery of the stationary blade of the compressor of the gas turbine engine is provided with a recess 18 directed radially outward, so that the rear side of the stationary blade (negative It is described that the flow velocity on the pressure side is reduced to suppress separation and reduce pressure loss.

JP 2008-274926 A Japanese Patent Laid-Open No. 7-247996

  By the way, especially in the stator vane of the fan stator swept rearward from the hub side toward the tip side, the circumferential static pressure gradient from the pressure surface side to the suction surface side of the stator vane is near the hub side end wall. It becomes larger in the latter half of the row, and the isostatic pressure line from the hub side to the tip side on the negative pressure surface of the stator vane is inclined with respect to the main stream, so that the hub side on the stator vane surface goes to the tip side. There is a problem that the pressure loss increases due to acceleration of the movement of the low momentum fluid.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to reduce the pressure loss by suppressing the movement of the low momentum fluid from the vane hub side of the stator of the axial flow type compressor toward the tip side.

In order to achieve the above object, according to the first aspect of the present invention, there is provided an inner peripheral surface shape of a casing surrounding an outer periphery of a stator vane radially disposed behind a rotor of an axial compressor. , generatrix of the casing, the front edge with a recess region recessed radially outward over a position behind the trailing edge from the forward position than, the recessed region of said vane includes a first recess of the front side, A rear second concave portion, a first convex portion that continues in front of the first concave portion, a second convex portion that swells radially inward at an intermediate position in the front-rear direction of the concave portion region, and a rear side of the second concave portion. The second convex portion bulges beyond the trailing edge of the vane, and the second concave portion starts to be recessed from the rear of the trailing edge of the vane. Proposed the inner peripheral surface shape of the casing of the axial compressor It is.

According to the invention described in claim 2 , in addition to the configuration of claim 1 , the first convex portion, the first concave portion, the second convex portion, the second concave portion, and the third convex portion are A shape of the inner peripheral surface of the casing of the axial-flow compressor characterized by being smoothly continuous is proposed.

According to the invention described in claim 3 , in addition to the configuration of claim 1 or claim 2 , the vane sweeps the tip side end portion backward with respect to the hub side end portion. A characteristic axial shape of the casing of the axial compressor is proposed.
Is proposed.

Incidentally, in response to the rotor of the fan rotor 15 is the invention of the embodiment corresponds to the stator of the fan stator 16 according to the present invention of the embodiment, the stator vanes 23 of the embodiment to correspond to the vane of the present invention The

According to the above configuration, the bus bar of the casing surrounding the outer periphery of the vane of the stator disposed behind the rotor of the axial flow compressor has a diameter extending from the front position to the rear position from the rear edge to the rear edge. a recess region recessed towards the outside, so and a second convex portion bulging radially inwardly in the longitudinal direction intermediate position of the concave region, the recessed area of the by the second convex portion remote front radial direction of the surface of the vane improves static pressure distribution, and by increasing the static pressure of the chip side by the recess region of the second projecting portion by remote rear, pressure loss by suppressing the movement of the low momentum fluid directed from the hub side to the tip side Can be reduced.

  The concave region includes a first concave portion on the front side, a second concave portion on the rear side, a first convex portion that continues in front of the first concave portion, and a second convex that bulges radially inward at an intermediate position in the front-rear direction of the concave portion area. Part, a second convex part constituting the convex part region, and a third convex part continuing behind the second concave part and smoothly continuing, so that the flow of airflow along the inner peripheral surface of the casing is smooth Become.

  In addition, since the vane sweeps the tip side end portion toward the rear with respect to the hub side end portion, it is possible to reduce shock wave loss and noise. Although the low-momentum fluid easily moves from the hub-side end portion to the tip-side end portion by the sweep of the vane, the movement of the low-momentum fluid is effectively suppressed by the inner peripheral surface shape of the casing of the present invention.

The schematic diagram which shows the whole structure of a turbofan engine. FIG. 2 is an enlarged view of part 2 of FIG. 1. FIG. 4A and 4B direction arrow view of FIG. The figure which shows the state of the wake of a stator vane. The figure which shows the streamline along the negative pressure surface of a stator vane. The graph which shows the change of the total pressure loss accompanying the change of mass flow rate. The graph which shows distribution of the total pressure loss along the span direction of a stator vane.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. In the present specification, the upstream side and the downstream side in the airflow direction are defined as the front and the rear, respectively, and the radially inner side and the radially outer side around the axis L are defined as the hub side and the tip side, respectively.

  As shown in FIG. 1, the turbofan engine E for aviation includes a substantially cylindrical outer casing 11 and an inner casing 12 that are rotating bodies having an axis L as a center. Inside the outer casing 11 and the inner casing 12, a low-pressure shaft 13 positioned on the axis L and a high-pressure shaft 14 fitted to the outer periphery of the low-pressure shaft 13 are arranged coaxially.

  A fan rotor 15 is provided at the front end of the low pressure shaft 13, and a fan stator 16 is provided behind the fan rotor 15. The front portion of the outer casing 11 constitutes an outer portion 17A of the fan casing 17, and the tip side of the fan rotor 15 faces the inner peripheral surface of the outer portion 17A of the fan casing 17. Further, the chip side of the fan stator 16 is fixed to the inner peripheral surface of the outer portion 17A of the fan casing 17, and the hub side of the fan stator 16 is fixed to the outer peripheral surface of the inner portion 17B of the fan casing 17.

  A low pressure compressor 18 is provided on the low pressure shaft 13 behind the fan stator 16, and a low pressure turbine 19 is provided on the rear end of the low pressure shaft 13. A high pressure compressor 20 facing the rear of the low pressure compressor 18 is provided at the front end of the high pressure shaft 14, and a high pressure turbine 21 facing the front of the low pressure turbine 19 is provided at the rear end of the high pressure shaft 14. A plurality of combustion chambers 22 are arranged between the high-pressure compressor 20 and the high-pressure turbine 21.

  Therefore, after the air compressed by the fan rotor 15 rotating with the low-pressure shaft 13 is rectified by the fan stator 16, a part of the air passes rearward through the bypass duct 24 formed between the outer casing 11 and the inner casing 12. The discharged portion is supplied into the inner casing 12 and compressed by a low-pressure compressor 18 that rotates with the low-pressure shaft 13 and a high-pressure compressor 20 that rotates with the high-pressure shaft 14, and then mixed with fuel in the combustion chamber 22 for combustion. Provided. Combustion gas exiting from the combustion chamber 22 passes through the high-pressure turbine 21 to drive the high-pressure shaft 14, passes through the low-pressure turbine 19 and drives the low-pressure shaft 13, and then is discharged rearward from the rear end of the inner casing 12. The air that has passed through the bypass duct 24 merges.

  FIG. 2 shows the stator vane 23 of the fan stator 16 disposed between the outer portion 17A and the inner portion 17B of the fan casing 17. The stator vane 23 has a radially inner hub side end 23c connected to the outer peripheral surface of the inner portion 17B of the fan casing 17, and a radially outer tip side end 23d of the inner side surface of the outer portion 17A of the fan casing 17. Connected to. The front edge 23a and the rear edge 23b of the stator vane 23 are swept so that the tip side end 23d is biased rearward with respect to the hub side end 23c. Therefore, the quarter code line 23e of the stator vane 23 is also The tip side is swept so as to be biased backward with respect to the hub side. Thereby, by reducing the code direction component of the flow velocity of the airflow flowing on the surface of the stator vane 23, the critical Mach number can be increased to delay the generation of the shock wave, and the shock wave loss and noise can be reduced. .

  The present invention is characterized by the shape of the inner peripheral surface of the outer portion 17A of the fan casing 17 in the vicinity of the tip side end 23d of the stator vane 23. Since the fan casing 17 is basically a substantially cylindrical member that is a rotating body centered on the axis L, the shape of the inner peripheral surface of the fan casing 17 is the shape of a generatrix (intersection with a plane passing through the axis L). Represented by

  The shape of the bus bar on the inner peripheral surface of the outer portion 17A of the fan casing 17 to which the chip side end 23d of the stator vane 23 is connected extends from the front position to the rear edge 23b from the front position to the front edge 23a. Basically, a concave region 31 that is recessed radially outward is provided. The recessed region 31 includes a first recessed portion 32 positioned slightly in front of the front edge 23a of the tip side end portion 23d of the stator vane 23 and slightly in front of the rear edge 23b, and a rear edge 23b of the stator vane 23. A second concave portion 33 that is located further rearward, a second convex portion 35 that bulges radially inward so as to connect the first and second concave portions 32 and 33 slightly in front of the rear edge 23b, and a first concave portion 32. The first convex portion 34 connecting the front end of the second concave portion 33 to the inner peripheral surface of the outer portion 17A of the fan casing 17, and the third convex portion connecting the rear end of the second concave portion 33 to the inner peripheral surface of the outer portion 17A of the fan casing 17. 36. That is, the recessed area 31 is configured by smoothly connecting the first convex part 34, the first concave part 32, the second convex part 35, the second concave part 33, and the third convex part 36 from the front to the rear. The position of the connecting portion of the first convex portion 34, the first concave portion 32, the second convex portion 35, the second concave portion 33, and the third convex portion 36 becomes an inflection point at which the direction of the curvature of the bus bar is switched.

  2 indicate the shapes of the inner peripheral surface of the fan casing 17 and the outer peripheral surface of the inner casing 12 of the comparative example.

  3 and 4 show the static pressure distribution around the stator vane 23. FIG. 3 shows the static pressure distribution at the section 3-3 in FIG. 2 (chip side end 23d of the stator vane 23). The static pressure distribution of the suction surface (back surface) of the stator vane 23 corresponding to the 4A and 4B direction arrows of FIG. 3 is shown. In FIGS. 3 and 4, it is shown that the darker portion (the shaded portion is denser) has a higher pressure, and the lighter portion (the shaded portion is lesser shaded) has a lower pressure.

  According to the embodiment, the first and second recesses 32 and 33 are formed on the inner peripheral surface of the outer portion 17A of the fan casing 17 to which the tip side end portion 23d of the stator vane 23 is connected. The static pressure increases as the flow velocity of the airflow flowing along the first and second recesses 32 and 33 decreases.

  As apparent from the comparison example and the embodiment in FIGS. 3 to 5, in the embodiment, the static pressure on the pressure surface of the stator vane 23 is higher than that of the comparison example due to the action of the first recess 32 of the fan casing 17. (See FIG. 3). Furthermore, in the embodiment, it can be seen that the static pressure at the rear position of the rear edge 23b of the stator vane 23 is increased with respect to the comparative example by the action of the second recess 33 of the fan casing 17 (see FIG. 4). ).

  As is clear from FIG. 4, in the embodiment, the isostatic line along the negative pressure surface of the stator vane 23 stands up from the comparative example by the action of the first recess 32 of the fan casing 17. That is, in the embodiment, the isostatic pressure lines are generally aligned in the radial direction, whereas in the comparative example, the radially outer side of the isostatic pressure line is retracted rearward, and accordingly, the radial direction of the isostatic pressure line is A static pressure distribution is formed in which the inner region (lower side in the figure) becomes high pressure and the radially outer region (upper side in the figure) of the isostatic pressure line becomes low pressure, and the hub side end portion 23c of the stator vane 23 starts. A secondary flow toward the tip side end portion 23d is induced. On the other hand, in the embodiment, since the isostatic line has almost no receding angle, the secondary flow is hardly induced.

  By the way, the rotor hub of the fan rotor 15 located in front of the fan stator 16 has a cone-like diameter increasing from the front to the rear, so that the airflow passing through the stator vane 23 of the fan stator 16 is increased in diameter from the inner side in the radial direction. A secondary flow toward the outside in the direction is easily induced, and when the stator vane 23 is swept, the air flow easily flows from the hub side to the tip side, and the secondary flow is further strengthened. As described above, when a secondary flow is generated along the stator vane 23 from the radially inner side to the radially outer side, the low momentum generated at the hub side end 23c of the stator vane 23 as shown in the comparative example of FIG. There is a problem that the pressure loss in the fan stator 16 increases because the wake (wake) tends to spread outward in the radial direction.

  However, according to the embodiment, the action of the first recess 32 of the fan casing 17 raises the isostatic line along the negative pressure surface of the stator vane 23 to suppress the secondary flow from the hub side toward the tip side. At the same time, due to the action of the second recess 33 of the fan casing 17, the secondary flow from the hub side toward the chip side is increased by increasing the static pressure at the rear position from the rear edge 23 b of the chip side end 23 d of the stator vane 23. By suppressing, as shown in the embodiment of FIG. 5, the pressure loss can be reduced by minimizing the region where the low-momentum wake spreads.

  FIG. 6 shows streamlines of the airflow along the suction surface of the stator vane 23. In the comparative example, the airflow flowing into the front edge 23a along the hub side end portion 23c of the stator vane 23 is radial in the rear edge 23b. The wake area Wh on the hub side is greatly biased to the outside, but in the embodiment, the secondary flow from the hub side to the chip side is suppressed, so that the wake area Wh on the hub side is reduced. I understand that. The secondary flow from the tip side toward the hub side is caused by the action of the second recess 33 of the fan casing 17 to increase the static pressure at the rear position of the rear edge 23b of the tip side end portion 23d of the stator vane 23. Therefore, the wake area Wt on the chip side of the embodiment is slightly larger than that of the comparative example, but overall, the wake area can be reduced to reduce pressure loss.

  FIG. 7 is a graph showing changes in the total pressure loss when the mass flow rate is changed, and in the illustrated mass flow rate, the total pressure loss of the embodiment is 20% of the total pressure loss of the comparative example. It can be seen that it is less than.

  FIG. 8 is a graph showing the distribution of the total pressure loss along the span direction of the stator vane 23 when the mass flow rate is 1.0, and is a partial region on the chip side (80% to 90% in the span direction). In the embodiment, the tip side wake region Wt becomes larger, so that the total pressure loss is increased compared to the comparative example. In other regions, the total pressure loss of the embodiment is the total pressure of the comparative example. It turns out that it becomes smaller than a loss.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. Is possible.

  For example, in the embodiment, the present invention is applied to the fan casing 17 of the turbofan engine E for aviation, but the present invention can only be applied to a turbofan engine for any use other than aviation. In addition, the present invention can be applied to an axial flow type compressor casing for any application.

  Moreover, although the stator vane 23 of the embodiment is swept, the present invention can also be applied to a stator vane that is not swept.

15 Fan rotor (rotor)
16 Fan stator (stator)
17 Casing 23 Stator vane (vane)
23a Front edge 23b Rear edge 23c Hub side end 23d Chip side end 31 Recess area 32 First recess 33 Second recess 34 First protrusion 35 Second protrusion (convex area)
36 3rd convex part

Claims (3)

The inner peripheral surface shape of the casing (17) surrounding the outer periphery of the vane (23) of the stator (16) arranged radially behind the rotor (15) of the axial compressor,
A concave region (31) in which the bus bar of the casing (17) is recessed radially outward from the front position to the rear edge (23b) from the front edge (23a) of the vane (23). The concave region (31) includes a front first concave portion (32), a rear second concave portion (33), and a first convex portion (34) continuous in front of the first concave portion (32). And a second convex portion (35) that swells radially inward at the intermediate position in the front-rear direction of the concave portion region (31), and a third convex portion (36) that continues to the rear of the second concave portion (33). And
The second convex portion (35) bulges beyond the rear edge (23b) of the vane (23), and the second concave portion (33) is recessed from the rear of the rear edge (23b) of the vane (23). The shape of the inner peripheral surface of the casing of the axial-flow compressor characterized by starting . The first convex portion (34), the first concave portion (32), the second convex portion (35), the second concave portion (33), and the third convex portion (36) are smoothly continuous. The shape of the inner peripheral surface of the casing of the axial flow compressor according to claim 1 . The axial flow type according to claim 1 or 2 , wherein the vane (23) has a tip side end portion (23d) sweeping backward with respect to the hub side end portion (23c). The inner peripheral shape of the compressor casing.

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