JPS5851121B2 - Turbine paragraph structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an axial flow rotary machine such as a steam or gas turbine, and particularly to a turbine stage structure composed of stationary blades and rotor blades.

The output stage of an axial flow machine such as a turbine is composed of a stationary blade row and a rotor blade row.

A specific example is shown in FIG.

A plurality of stator blades 2 are fixed in an annular shape by a diaphragm outer ring 1a and an inner ring 1b, and are installed in the vehicle compartment 5 to form a stator blade row.

On the other hand, a plurality of rotor blades 3 are attached on the rotor disk 4 on the downstream side of the stator blades, forming a row of rotor blades.

As shown in FIG. 2, the working fluid 6 flows in from the stator blade inlet 2a and flows out from the stator blade outlet 2b downstream of the stator blade.

Thereafter, it flows into the rotor blade 3 from the rotor blade population 3a, and flows out from the outlet 3b while rotating the rotor blade.

Here, R indicates the rotation direction. Now, downstream of rotor blade 2,
Since a diffusion region of the boundary layer developed on the blade surface of the stationary blade 2, that is, a wake occurs, the distribution of the working fluid does not become a uniform flow, but becomes a fluctuating speed distribution 6a having periodic speed defects.

This non-uniform speed distribution causes an increase in airfoil loss, particularly unsteady loss, of the rotor blades 3, and reduces turbine performance.

Furthermore, since it acts on the rotor blade 3 as a periodic fluctuating force, it becomes a cause of resonance fatigue failure of the rotor blade.

Figure 3a shows the mechanism by which unsteady loss occurs.

Airfoil loss of moving blades, stationary blades, etc. is greatly influenced by the inflow angle of the working fluid flowing into the blade, and the inlet angle βm unique to the blade shape,
When the working fluid inflow angles βS match, that is, the deviation angle i−
When βS−βm is O, the loss is the smallest.

As shown in FIG. 3b, the loss increases as the difference between the inlet angle βS and the inlet angle βm increases, that is, as the deviation angle i departs from 0.

This tendency of increase in loss is particularly remarkable in rotor airfoils with low recoil.

Therefore, in the turbine stage, the airfoil shape and blade device are selected so that the deviation angle i=o in the average flow direction.

However, in the actual flow inside the turbine,
As described above, the flow downstream of the stationary blade 2 is a non-uniform fluctuating flow.

The inflow angle βS of the flow flowing into the rotor blade 3 is determined by the absolute outflow velocity U from the stator blade 2 and the rotational circumferential speed W as shown in Fig. 3a. The speed becomes Vd, and the deviation angle i increases.

Therefore, the rotor blade loss increases.

Furthermore, the fluctuating component of the flow velocity interferes with the boundary layer that develops on the blade surface of the rotor blade, increasing the airfoil loss.

The purpose of the present invention is to reduce unsteady loss by reducing the non-uniformity of the flow downstream of the turbine stator blades as described above by using the contraction effect and increasing the uniformity of the flow. The object of the present invention is to obtain a high-performance turbine and to obtain a turbine with higher stability by reducing the vibration stress of the rotor blades due to fluctuating fluid force.

The present invention is characterized by a tendency for the flow behind the blade row to become uniform;
In other words, we focused on the experimental fact that recovery from wake velocity loss is faster when the flow acceleration is higher. A channel groove is provided so that the channel can be accommodated inside, and the channel groove is
A straight groove having a constant width is formed up to the stator blade inlet, and a curved groove along the outer contour of the stator blade is formed from the stator blade inlet to the groove end, and the straight groove has a constant groove depth. and the curved groove portions are formed such that the groove depth from the stator blade outlet to the groove end gradually decreases toward the groove end, so that the flow path area from the stator blade outlet to the rotor blade inlet is It gradually decreases in the flow direction to create a contracted flow path, accelerates the flow, improves the flow uniformity at the rotor blade inlet, and further corrects the flow deflected toward the wake velocity defect to improve the stator blade outflow. This improves angular uniformity, reduces unsteady loss and excitation force in the rotor blades, and realizes a high-performance, highly safe turbine.

Hereinafter, one embodiment of the turbine stage structure of the present invention will be described with reference to FIGS. 4 to 8.

In FIG. 4, a plurality of stator blades 12 (e.g., a plurality of stator blades are fixed in an annular shape by an outer ring 11a and an inner ring 11b of the diaphragm 11 to form a stator blade row and are attached to a vehicle compartment 15.

On the other hand, the moving blade 13 has a rotor disk 1 on the downstream side of the stationary blade.
A plurality of rotor blades are attached to the rotor blade row.

As shown in FIG. 2, the working fluid 6 flows in from the stator blade inlet 12a and flows out downstream from the stator blade outlet 12b.

Thereafter, it flows into the rotor blade 13 from the rotor blade population 13a, rotates the rotor blade 13, and flows out from the outlet 13b.

In FIGS. 4 to 8, the diaphragm outer ring 11a
A channel wall of the inner ring 11b is provided with a channel groove 17 extending from the inflow end to the outflow end of the working fluid for each stator vane to house the stator vane therein.

The flow path groove 17 is formed as a straight groove portion 1γa having a constant width 1 up to the stator blade 12 population portion, and as a curved groove portion 17b along the outer contour of the stator blade 12 from the stator blade inlet portion to the groove end. (Figure 5).

The straight groove portion 17a is formed to have a constant groove depth h, and the curved groove portion 17b is formed such that the groove depth from the stationary blade outlet to the groove end gradually decreases toward the groove end (
6 to 8), from the stator blade outlet 12b to the rotor blade human power 1
The cross-sectional area of the flow path reaching 3a is gradually reduced to form a contraction flow path.

The flow path area of the stator blade row is as shown in FIG.
a (I in the figure) to the exit 12b (■ in the figure).

In addition, in the conventional example, the flow path area from the stationary blade outlet (■ in the figure) to the rear end of the diaphragm (■ in the figure) is constant as shown by the dashed line in the figure, whereas in the present invention, the groove depth gradually decreases. Due to the curved groove portion, the flow path area is reduced to the stationary blade outlet 12b (■ in the figure).
It further decreases as shown by the solid line up to the rear end of the diaphragm, that is, the end of the groove (■ in the figure).

For this reason, the working fluid 6 after the stationary blade outlet 12b (■ in the figure)
In the conventional example, the velocity is a constant flow velocity as shown by the dashed line,
In other words, it becomes an equilibrium flow, whereas in the present invention, as shown by the solid line, it becomes an accelerated flow whose velocity further increases up to the rear end of the diaphragm (■ in the figure).

Figures 10a and 10b show a diffusion state of the trailing stream of the blade row, that is, a state in which the velocity deficit Ud of the trailing stream is recovered and equalized.

The horizontal axis X in FIG. 10b is the distance from the stationary blade outlet 12b to the downstream side, and the vertical axis is the ratio of the maximum deficit speed Udo of the blade row wake shown in FIG. 10a to the main stream speed Um, that is, speed recovery. Show rate.

As shown in Figure 10b, the wake velocity loss is caused by the blade exit 12.
The farther downstream from b, the more it recovers and becomes more uniform.

The recovery state of this velocity deficit differs depending on whether the flow condition is accelerated flow or equilibrium flow, and the recovery rate in accelerated flow is better than in other conditions.

Therefore, the speed distribution in the rotor blade population 13a is
As shown in the figure, since the present invention is accelerated by the contraction action of the inner wall of the diaphragm, the velocity distribution is as shown in 18a (solid line in the figure), and the velocity distribution is as shown in 18b (dotted chain line in the figure) in the case of the conventional example. The wake center velocity Ud compared to the velocity distribution in equilibrium flow.

The flow is also high and highly uniform.

As a result, in the case of the present invention, the relative inflow velocity at the inlet 13a of the rotor blade 130 is determined by the wake center velocity Udo, the flow velocity from the rotor blade rotation peripheral speed W to Vd, and the deviation angle i, as shown in FIG. 11b.
It flows into the rotor blades 13 with the force.

On the other hand, in the case of the conventional example, since the wake center velocity Udo' is lower than Udo, the fluid flows into the rotor blade 13 with a flow velocity Vd' and a deviation angle j', so that i'>i.

Therefore, the unsteady loss ξ in the rotor blade is reduced compared to the loss ξ' of the conventional example, as shown in FIG. 11c.

Further, in the present invention, the flow path groove 17 provided on the diaphragm wall surface is formed by a straight groove portion 17a and a curved groove portion 17b along the outer contour of the stator blade, and the flow path from the stator blade outlet to the rotor blade inlet is contracted. Since it is formed in the flow channel, the flow after the exit of the stator vane 12 as shown in FIG. 12a is deflected toward the center Udo of the wake velocity defect, as shown in FIG. 12b.

Therefore, the outflow angle β of the flow is not uniform as shown by the curve 9a in FIG. Since the flow channel substantially coincides with the center of the wake, it serves to send the flow to the velocity deficit part of the wake.

As a result, the deflection of the flow toward the wake center is corrected, and the first
The uniformity of the outflow angle β is increased as shown by line 9b in Figure 2d.

Therefore, the deviation angle i of the flow flowing into the rotor blade 13 from the rotor blade proper population angle described in FIG. 11b is reduced, and unsteady loss and vibration stress can be reduced.

As explained above, according to the turbine stage structure of the present invention, the uniformity of the flow at the rotor blade inlet is improved by the two rectifying effects, and unsteady loss and vibration stress are reduced.
We can provide highly efficient turbines.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a conventional turbine stage structure, Fig. 2 is an A-A cross section in Fig. 1 and a flow state diagram, and Figs. 3a and 3b are explanatory diagrams showing the state of occurrence of unsteady loss. ,
FIG. 4 is a sectional view showing one embodiment of the turbine stage structure of the present invention, FIG. 5 is a BB sectional view of FIG. 4, FIG. 6a is a CC sectional view of FIG. 5, and FIG. 6b is the same < DD sectional view, FIG. 7 is a view taken along the line E-E in FIG. 4, FIG. 8 is a view taken along the same <F-F arrow, and FIG. Figures 11a to 11c and 10b are explanatory diagrams showing the behavior characteristics of the trailing flow of the blade row, which is the principle of the present invention, and Figures 11a to 11c and 1
2a to 12d are explanatory diagrams showing the reason for the reduction of unsteady loss according to the present invention. 11...Diaphragm, 11a...Outer ring, 11b...Inner ring, 12...Stator blade,
12a... Stator blade inlet, 12b... Stator blade outlet, 13... Moving blade, 13a... Moving blade inlet, 13b... Moving blade outlet, 14...
Rotor disk, 15...- Vehicle interior, 17...
...Flow path groove, 17a...Straight groove part, 17b...
...Curved groove.

Claims (1)

[Claims] 1. In a turbine stage structure consisting of stator blades and rotor blades of an axial flow rotating machine, a diaphragm wall is provided with a structure that allows each stator blade to be housed inside the diaphragm wall from the inflow end to the outflow end of the working fluid. A flow path groove is provided, and the flow path groove is formed as a straight groove portion having a constant width up to the stator blade inlet portion, and as a curved groove portion along the outer contour of the stator blade from the stator blade inlet portion to the groove end. At the same time, the straight groove portion is formed to have a constant groove depth, and the curved groove portion is formed such that the groove depth from the stator blade outlet to the groove end gradually decreases as it goes toward the groove end. A turbine stage structure characterized in that the flow path area leading to the rotor blade inlet gradually decreases in the flow direction of the working fluid.