JPS6133968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stage internal structure of a multi-stage axial flow machine, such as a multi-stage axial flow turbine.

With reference to FIGS. 1 to 6, the flow and loss of working fluid in the stage internal structure of a conventional multistage axial flow turbine will be explained.

FIG. 1 shows the stages of a multistage axial flow turbine, and in the axial direction of the rotor R, the upstream stage A
and a subsequent stage B. The previous stage A
has a stator blade 1 and a rotor blade 3, and the stator blade 1 is arranged between an outer diaphragm 2a and an inner diaphragm 2b.
A plurality of rotor blades are fixed in the circumferential direction to form a stator blade row, and a rotor blade 3 is arranged downstream of the stator blade 1, and a plurality of rotor blades are fixed in the circumferential direction of the rotor disk 4 to form a rotor blade row. are doing. Further, a plurality of tips of the rotor blades 3 are connected via a shroud 5. On the other hand, the subsequent stage B has a stator blade 1' and a rotor blade 3', and the stator blade 1' has an outer diaphragm 2a' and an inner diaphragm 2a'.
A plurality of rotor blades 3' are fixed in the circumferential direction between the stator blades 1' and a stator blade row. A plurality of rotor blades 3' are connected to each other via a shroud 5', forming a row of blades. Note that the reference numeral 6 in FIG. 1 indicates a vehicle interior.

In this multi-stage axial flow turbine, the working fluid 9
passes through the stator blade 1 of the preceding stage A, and its thermal energy is converted into interlocking energy, rotates the rotor blade 3 and performs work, then enters the succeeding stage B, passes through the stator blade 1', and generates the rotor blade 3. ', and as in the previous stage A, the rotor blades 3' are rotated to perform work.

By the way, various losses occur in the above-mentioned axial flow turbine.

FIG. 2 particularly shows the losses occurring in the row of stator blades, and FIG. 2b shows the distribution of losses in the stator blades in the blade span direction. Losses in stationary blades include airfoil shape loss E _P caused by friction loss between the blade surface and the fluid, and sidewall losses occurring near the inner side of the diaphragm 2a, which is the outer side wall, and near the outer side of the diaphragm 2b, which is the inner side wall. Loss of rules E _W
It is broadly divided into. In particular, the sidewall loss E _W is an energy loss of 5 to 10% in a stage with a short blade length, and is a major factor in reducing the efficiency of an axial flow turbine.
In addition, sidewall loss E _W consists of sidewall friction loss and secondary flow loss, both of which are caused by the boundary layer that develops near the sidewall. The larger the boundary layer thickness δ ₁ at the inlet of 1, the greater the sidewall loss E _W . Note that the reference numeral 13 in FIG.
b indicates stator blade loss, sidewall loss, and airfoil loss, respectively.

FIG. 3 explains the mechanism by which the secondary flow loss occurs. The fluid near the outer diaphragm 2a and the inner diaphragm 2b, which are the side walls of the stationary blade 1, flows at a very low velocity due to the existence of the boundary layer 13. Therefore, within the boundary layer 13, the centrifugal force of the fluid and the dorsal side 1a and ventral side 1 of the stationary blade 1 are generated.
The balance with the pressure difference between the two sides is lost, and a secondary flow 10 is generated from the high-pressure ventral side 1b toward the dorsal side 1a. This secondary flow 10 generates a vortex 10a at the corner of the back side 1a, resulting in loss. In this way, the secondary flow 10 is generated within the boundary layer 13 in a low energy state, and the thicker the boundary layer 13 on the side wall, the greater the kinetic energy lost by the secondary flow 10. , resulting in increased sidewall losses of the stator vanes.

Experiments have shown that the sidewall loss of the stator vane is significant on the outer sidewall of the stator vane 1 and is several times greater than the loss near the inner sidewall. The reason for this is that, in addition to the three-dimensional effect of the fluid flow, the boundary layer thickness δ ₁ at the inlet of the vane 1 is thicker on the outer side wall than on the inner side wall. and,
The main reason why the boundary layer on the outer side wall of the stator blade 1 develops significantly is the non-uniformity of the flow in the rotor blade 3 of the front stage A. Note that the reference numeral 9' in FIG. 3 indicates the mainstream.

FIG. 4 shows the flow of the main flow 9' between the rotor blade rows and the flow of the tip leakage flow 11 from the gap between the shroud 5, which is the rotor blade tip side member, and the diaphragm 2a, which is the outer member. As shown in FIG. 4a, the main flow 9' passes between the blades of the rotor blade row and flows away. On the other hand, the tip leakage flow 11 leaks from the gap between the shroud 5 and the radial fin 7, which is installed for the purpose of minimizing the tip leakage flow 11. The tip leakage flow 11 of the rotor blade 3 becomes a flow having a component in the rotational direction S of the rotor blade 3 due to the frictional force with the shroud 5 and flows out to the downstream side of the rotor blade 3. Therefore, the flow velocity distribution 9 downstream of the rotor blade 3
a' is a swirling flow 9 at the tip, as shown in Figure 4b.
It becomes a twisted flow with a''.

FIG. 5 illustrates the above-mentioned flow mechanism on a rotating coordinate system and in a relative velocity field. Figure 5 a,
As shown in Fig. b, the main flow 9' passing between the blades of the rotor blade row is turned and flows out at the rotor blade 3, whereas the tip leakage flow 11 leaking from the gap between the shroud 5 and the radial fin 7 is Since it flows out almost in the axial direction of the rotor, there is a large difference in the direction of the two outflows. Therefore, the outflow angle α at the rotor blade outlet becomes twisted as shown by reference numeral 15 in FIG. 5d.

Next, FIG. 6 explains how the flow flowing out from between the blades of the rotor blade row of the preceding stage A behaves in the vicinity of the side wall of the stationary blade 1' of the succeeding stage B. As shown in FIG. 6a, the flow 9a' flowing out from between the blades of the rotor blade row of the preceding stage A passes near the side wall of the stationary blade 1' of the succeeding stage B, and develops a boundary layer 13. It reaches the inlet of the stationary blade 1'. By the way, as mentioned above, the tip of the rotor blade 3' of the front stage A has a twisted flow due to the tip leakage flow 11, but as shown in FIG. 6b, the leakage flow absolute velocity 11a is It heads in the direction of turning angle γ, which is a combination of the speed 12 component and the relative speed 11b component. For this reason, the stationary blade 1' of the succeeding stage B
The flow 16 near the diaphragm 2a', which is the outer side wall of the
It takes a large detour to reach the inlet of the stationary blade 1'. As a result, the run-up distance l of the flow near the diaphragm 2a', which is the outer side wall, becomes significantly longer than the distance la from the inlet of the diaphragm 2a' to the inlet of the stationary blade 1'. The boundary layer thickness δ ₁ at the inlet of the stationary blade 1' is proportional to the run-up distance l. That is, δ ₁ ∝l Therefore, as shown in Fig. 6c, the larger the swirl angle γ due to the leakage flow, the longer the run-up distance l becomes, and the boundary layer thickness δ ₁ at the stationary blade inlet increases. , the side wall loss E _W of the stationary blade 1' of the succeeding stage B increases as described above.

In short, in a conventional multi-stage axial flow turbine, the flow swirl caused by the tip leakage flow leaking from the gap between the tip side member of the rotor blade of the preceding stage A and the member outside thereof causes the outer side wall of the stator blade 1' of the succeeding stage B to There is a drawback that the side wall loss E _W occurring in the vicinity increases significantly.

An object of the present invention is to reduce the sidewall loss that occurs near the outer sidewall of the stator blade in the subsequent stage due to swirling of the tip leakage flow leaking from the gap between the tip side member of the rotor blade in the previous stage and the member outside thereof. An object of the present invention is to provide a stage internal structure of a multistage axial flow machine that can significantly reduce the

A feature of the present invention is that a tip leakage flow leaks from a gap between a rotor blade tip side member and a member outside the rotor blade between a rotor blade in a preceding stage and a succeeding stage and at a position on the tip side of the rotor blade. This structure consists of a plurality of baffle plates installed in the circumferential direction to divert the current to the outflow direction of the main stream. The structure has been obtained.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 7 to FIG. 11 show an embodiment of the present invention, and show a case where the present invention is applied to a multi-stage axial flow turbine. In this embodiment, as shown in FIG. 7, FIG. 8a, b, and FIG. A plurality of rectifier plates 8 are arranged at equal intervals in the circumferential direction at the tip side of the rotor blade 3.
Each baffle plate 8 is formed of a relatively thin plate material, and as shown in FIG. When the chord length at the tip is _BW , H=0 to _0.7BW . Further, the shaping plate 8 is arranged parallel to the rotor, which is the rotation axis of the rotor blade, and is
It is fixed to a stationary outer wall 2c formed by extending the outer diaphragm 2a in the direction of the succeeding stage B, and as clearly shown in FIG. Tip leakage flow 1 leaking from the gap with the radial fin 7 which is a member
1 in the outflow direction of the main stream 9'.

Next, based on FIGS. 10 and 11,
The reason why the distance between the inner edge 8a of the baffle plate 8 and the tip of the rotor blade should be set to H=0 to _0.7BW as described above will be explained.

The baffle plate 8 is placed immediately after the rotor blade 3 of the front stage A, but in order to avoid contact or interference between the rotor blade 3, which is a rotating body, and the baffle plate 8, which is a fixed plate, the baffle plate 8 is
In particular, as shown in FIG.
Between the rear edge 5a and the front edge 8b of the current plate 8
spaced at mm intervals. As a result, the tip leakage flow 11 and the main flow 9' are mixed until they reach the front edge 8b of the baffle plate 8. Therefore, the flow at the front edge 8b of the baffle plate 8 is in a flow state similar to that of the conventional example shown in FIG. This is the area up to the position H in the direction of the blade root. Therefore, by setting the inner end edge 8a of the baffle plate 8 at a position extending by H from the tip of the rotor blade in the direction of the root of the rotor blade, the flow straightening function can be better exhibited. Incidentally, if the height H is made larger than _0.7BW , as shown in FIG. 11b, the fluid friction loss E _F of the baffle plate 8 itself increases, which is not effective. According to the results of experiments, it is more preferable to set H=0.3 to _0.7BW .

Next, Figures 6, 9, 10 and 11
The operation will be explained with reference to the figures.

In the above-mentioned paragraph internal structure, the tip leakage flow 11 leaking from the gap between the shroud 5 and the radial fin 7 at the tip of the rotor blade is directed in the rotating direction S of the rotor blade, as shown in FIGS. 9 and 10a. After flowing out, the direction of the flow is changed by the current plate 8 to the outflow direction of the main stream 9'. As a result, the state of the flow after passing through the current plate 8 becomes a flow that does not have a swirling component, as shown by reference numeral 9a. Therefore, as shown in FIG. 10b, in the conventional multi-stage axial flow turbine, the flow between the stages becomes a flow 15' having a swirling component in the rotating direction of the rotor blade at the tip of the blade, whereas this In the present invention, due to the rectifying action of the rectifier plate 8, a uniform flow 15 without swirling components is created as shown in FIG. 10c.

As a result, in the conventional multi-stage axial flow turbine, as shown in FIG. According to the invention, it is possible for the angular flow 16 to flow in the same direction as the main flow 9' flowing in the axial direction of the rotor, so that the invention provides a flow in the outer side wall of the vane 1'. The run-up distance l can be reduced to a minimum, and the boundary layer thickness _δ1 at the stator blade inlet near this outer sidewall can be made extremely thin, so that the stator blade 1' can be significantly reduced.

In the embodiment shown in FIGS. 7 to 11, the structure and operation of other parts are similar to the conventional one shown in FIG. 1.

FIG. 12 shows another embodiment of the present invention, in which the shape of the current plate is different.

That is, the current plate 8 shown in this embodiment is
As shown in FIG. 12a, the upstream half of the tip leakage flow in the portion extending from the tip position of the rotor blade toward the root of the rotor blade is an inclined surface that gradually increases the distance m from the trailing edge 3a of the rotor blade tip. 8c and the twelfth
As shown in FIGS. b and d, the portion having the inclined surface 8c is curved in a direction opposite to the rotating direction S of the rotor blade.

Therefore, as shown in FIGS. 12b and 12c, when the angle between the center line of the rotor in the axial direction of the baffle plate 8 and the circumferential direction at the front edge 8b of the baffle plate 8 is defined as the baffle plate inlet angle β _n . , this baffle plate inlet angle β _n is matched with the outflow angle β _s of the flow at the rotor blade outlet of the front stage A shown by the broken line in FIG. It has become possible to achieve this effectively. As a result, in the embodiment shown in FIG. 12, loss due to collision between the tip leakage flow 11 and the baffle plate 8 can be prevented, and the turbine efficiency can be further improved.

Furthermore, FIG. 13 shows another embodiment of the present invention, in which the current plate 8 is connected to the subsequent stage B.
The diaphragm 2 which is the outer side wall of the stationary blade 1'
Stationary outer wall 2 with a′ extended toward the rotor blade 3 side of the front stage A
It is similar to the embodiment shown in FIG. 12 except that it is attached to c'.

The embodiments shown in FIGS. 7 to 13 above have been described in detail with respect to the case where the present invention is applied to a multi-stage axial flow turbine, but the present invention is not limited to this, and it goes without saying that the present invention can be applied to multi-stage axial flow machines in general. It is.

The present invention has the configuration and operation described above, and according to the present invention, it is possible to significantly reduce the side wall loss in the stator vane of the succeeding stage of a multi-stage axial flow machine, thereby significantly increasing the efficiency of the axial flow machine. There is an effect that can be improved.

[Brief explanation of the drawing]

Figure 1 is a meridional cross-sectional view of a conventional multistage axial turbine, and Figures 2 a, b, and c are the stator blade structure of a coaxial turbine, the loss in the stator blade, and the relationship between sidewall loss and boundary layer thickness at the inlet of the stator blade. Figure 3 is an explanatory diagram showing the mechanism of secondary flow loss generation in the stator blade rows of a coaxial flow turbine. Figures 4 a and b are perspective views of the coaxial flow turbine viewed from the rotor blade outlet side. , and explanatory diagrams of the mainstream flowing out from the rotor blade outlet, Figures 5a, b, c, and d show the flow flowing through the coaxial flow turbine rotor blade, the outflow angle of the mainstream, the state of leakage flow, and the flow from the rotor blade. An explanatory diagram of the outflow angle, Figures 6a, b, and c are the front view of the flow between the stages of a coaxial flow turbine, the view from line bb in Figure 6a, and the outer side wall of the stationary blade. FIG. 2 is an explanatory diagram showing the relationship between the swirl angle of the flow and the sidewall loss. Next, FIG. 7 is a meridional cross-sectional view showing an embodiment in which the present invention is applied to a multi-stage axial flow turbine, FIGS. View from bb in a,
Figures 9a and 9b show the rectifying action of the baffle plate as seen from the rotor blade outlet side, and an explanatory diagram of the mainstream flow;
Figures 10a, b, and c are explanatory diagrams of the swirling angle of the flow on the rotor blade outlet side, the swirling angle of a conventional multistage axial flow turbine, and the swirling angle due to the action of the baffle plate constituting the present invention, and Figure 11a and b is an explanatory diagram of the relationship between the baffle plate and the preceding moving blade, and the relationship between the height dimension of the baffle plate and the stator blade loss, and Fig. 12 a, b, c, and d are other embodiments of the present invention. Viewed from the front, 12th
Figure 13 is a diagram showing the state seen from the line XIIb-XIIb in Figure a, the relationship between the baffle plate inlet angle and the outflow angle of the flow at the rotor blade outlet, and the state of the baffle plate seen from the slope. It is an enlarged front view showing an example. A...Previous stage of a stage of a multi-stage axial flow machine, B...Subsequent stage, R...Rotor, 1...Stator vane of the previous stage, 1'...Stator vane of the subsequent stage, 2a, 2b...Outer and inner diaphragms of the previous stage, 2a ', 2b'...Outer and inner diaphragm of the succeeding stage, 3... Moving blade of the preceding stage, 3'... Moving blade of the succeeding stage, 5... Shroud of the preceding stage, 5'... Shroud of the succeeding stage, 7... Radial fin, 8 ...straightening plate, 8a
...Inner edge of the baffle plate, 8b...Front edge, 8c...Slanted surface, H...Height of the portion of the baffle plate extending from the moving blade tip position to the root direction of the moving blade, B _W ...Chord of the moving blade tip Length, 9...Working fluid, 9'...Main stream, 11...Leakage flow at the tip of the rotor blade, m...Distance from the rear edge of the tip of the rotor blade to the front edge of the baffle plate.

Claims (1)

[Claims] 1. In a multi-stage axial flow machine in which a plurality of stages each having a plurality of stator blade rows and a rotor blade row arranged in the circumferential direction are provided in the axial direction of the rotor, A rectifier for diverting a tip leakage flow leaking from a gap between a tip part of a rotor blade and a member on its outer circumferential side to the outflow direction of the main flow between the stationary blade of a succeeding stage and at a position near the tip side of the rotor blade. A stage internal structure of a multistage axial flow machine characterized by a plurality of plates attached in the circumferential direction. 2. The height H of the portion of the baffle plate extending from the tip of the rotor blade toward the root of the rotor blade is set to H=0 to 0.7B _W (where B _W is the chord length of the tip of the rotor blade). A stage internal structure of a multistage axial flow machine according to claim 1. 3. The upstream half of the tip leakage flow of the rotor blade in the portion of the baffle plate extending from the rotor blade tip position toward the root of the rotor blade is an inclined surface that gradually increases the distance from the rear edge of the rotor blade tip, and The stage internal structure of a multistage axial flow machine according to claim 1, characterized in that the stage is formed in a shape curved in a direction opposite to the rotation direction.