JPS6045287B2 - Mixed flow turbine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mixed flow turbine used in an exhaust turbine supercharger, a helium expansion turbine, and the like.

First, a conventional mixed flow turbine equipped with an impeller called a half-shroud type will be explained with reference to FIG.

The casing 3 houses an impeller 1 fixed to a shaft 7, is provided with a nozzle 2, and has a flow path 4 formed therein. A wall surface connected to the casing 3 part on the downstream side of the impeller 1 is an enlarged tough user 6. The working fluid flows from the flow path 4 to the tough user 6 via the nozzle 2 and the impeller 1 as shown by the arrow 5. In such a mixed flow turbine, a gap 8 must be provided between the impeller 1 and the casing 3 to prevent them from coming into contact with each other.

A portion of the working fluid does not pass through the impeller 1 but passes through the gap 8. The working fluid passing through the gap 8 generates power and also disturbs the flow within the impeller 1, thereby reducing the power generated by the turbine. That is, a mixed flow turbine incorporating a half-shroud impeller, which has advantages such as low manufacturing cost and easy machining accuracy, has the drawback of low efficiency. The purpose of this invention is to improve the efficiency of a mixed-flow turbine equipped with a half-shroud type impeller.The invention has a guide for adjusting the flow inside the impeller, a guide for adjusting the flow inside the impeller, and a guide for adjusting the flow inside the impeller, and a guide for adjusting the flow inside the impeller, and a guide for adjusting the flow inside the impeller. A seal is provided that prevents the working fluid from leaking from the gap between the guide and the seal, or a seal that functions as both the guide and the seal.

Next, one embodiment of the present invention will be explained with reference to FIG.

In this figure, the same reference numerals as in FIG. 1 represent the same parts. In a mixed flow turbine equipped with a half-shroud type impeller 1, among the gaps between the impeller 1 and the casing 3, the gap 10 near the impeller outlet 12 has a greater effect on performance than the gap 9 near the impeller inlet 11. , it is known that reducing the gap 10 improves efficiency.

This will be explained with reference to FIGS. 3 and 4. 3 is a sectional view taken along line 1 in FIG. 1, and FIG. 4 is a sectional view taken along line 1 in FIG. The working fluid passing through the gap between the blades 15 of the impeller 1 and the casing 3 flows along the gap 8 in FIG. It flows in, disrupts the flow between the blades 15, and creates a region 18 with low mechanical energy.

The formation of such a region 18 significantly increases the resistance to the working fluid and significantly reduces the efficiency of the turbine. The working fluid generates power when it flows between the blades 15 in FIG. 4 relative to the blades 15 as shown by the arrow 19.
When it flows relative to the blade 15 as shown by the arrow 17, no power is generated and it simply passes through. Since the blades 15 are bent as shown in FIG. 4 near the impeller outlet 12, a region 18 of low mechanical energy shown in FIG. 3 tends to develop.

Furthermore, if the gap 8 is narrow near the impeller outlet 12, the working fluid that has passed through the gap 8 near the impeller inlet 11 with a large angular momentum will have to pass through the flow path inside the impeller 1. , will generate power. For this reason, impeller outlet 1 in gap 8
It is thought that narrowing the area near 2 will greatly affect the efficiency of the turbine. This invention is based on the above, and the impeller 1
The outer edge near the outlet 12 of the tube is placed on a cylindrical surface centered on the shaft 7. A seal guide 14 of a type that does not cause damage even if the impeller 1 comes into contact with the inner circumferential surface of the casing 3 surrounding the outer edge 13 of the casing 3 is provided.

This seal guide 14 uses something like a honeycomb seal. The seal guide 14 is provided on the inner peripheral surface of the casing around the outer edge 13 of the impeller on the cylindrical surface, so even if the impeller 1 moves back and forth (in the axial direction) together with the shaft 7 during rotation. , the size of the gap between them does not change.

Moreover, the movement of the impeller 1 and the shaft 7 in the radial direction is almost negligible compared to the dimensions of the impeller 1 that is normally used. Since the seal guide 14 is of a type that does not cause damage even if it comes into contact with the impeller 1, the flow near the impeller outlet 12 can be significantly improved. Therefore, the efficiency of the turbine can be improved.
Here, the configuration and effects of the seal guide 14 will be described in detail. FIG. 5 is a plan view showing the seal guide 14 in relation to the seal guide 14, and FIG. 6 is a cross-sectional end view taken along the line 1--2 in FIG.

A fin 20 is provided on the side of the seal guide 14 facing the impeller 1. On the upstream side J2l, the fin 20 is located on the upstream side 2 of the seal guide 14 with respect to the tangential direction 23.
1 at the same angle as the absolute velocity 24 of the flow near the outer edge of the impeller 1 at a position facing the impeller 1, and forming the same angle as the absolute velocity 25 of the flow near the outer edge of the impeller 1 with respect to the tangential direction 23 toward the downstream. It reaches the downstream side 22. fin 2
The cross section of 0 is one with a sharp tip and spaced apart as shown in Fig. 6, one with a uniform thin thickness as shown in Fig. 7, and one with a sharp tip and a closely spaced one as shown in Fig. 8. What made me
As shown in Figure 9, the tips or the fins themselves, such as serrated ones, are thin, and the gap 10 between the impeller blades 15 and the fins is too small, causing damage to the impeller even if the impellers make contact. It is shaped so that it does not give any damage.

Since the fins 20 always extend from the upstream side to the downstream side along the absolute velocity of the flow, the flow in the impeller 10 is not disturbed. Further, the gap 26 between each fin is desirably narrower than the thickness of the blades 15 of the impeller, but may be narrower than the interval 27 between the blades 15. FIG. 10 shows the flow of the working fluid near the casing 3 of the impeller outlet 12 of FIG.

The flow 28 that does not pass through the blades 15 of the impeller 1 is indicated by the arrow 29
, 30. Since the gap between the fin 20 and the vane 15 is very small, the flow passing through this part can be ignored. Since these flows do not pass through the impeller 1, no power is generated, but since the flow within the impeller 1 is hardly disturbed, the loss of mechanical energy is reduced. Since the height of the fins 20 can be made small, each fin 2
The amount of working fluid flowing between the fins 20 and 0 is small, and the impeller 1
The reduction in mechanical energy loss of the internal flow is greater, and the output of the turbine can be increased. 11 and 12 are plan views of the seal guide according to the present invention, similar to FIG. 4.

In FIG. 11, the fins 20 are made straight in order to facilitate manufacturing. Although this seal guide is less effective, it improves workability. In Fig. 12, the fins are bent in the middle to ensure workability and to prevent reduction in effectiveness.

This embodiment allows for smoother flow compared to the embodiment of FIG. According to the invention described above, the efficiency of a mixed flow turbine equipped with an impeller without a front shroud can be easily improved.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional side view showing a conventional mixed flow turbine;
The figure is a cross-sectional side view showing one embodiment of the mixed flow turbine according to the invention of Tsuchi, and FIGS. 3 and 4 are explanatory diagrams showing the effect of the flow of working fluid through the gap between the impeller and the casing. is an enlarged cross-sectional view of Figure 1, and Figure 4 is an enlarged cross-sectional view of Figure 3.
-■Cross-sectional view is shown. FIG. 5, FIG. 11, and FIG. 12 are developed plan views showing different embodiments of the seal guide according to the present invention, and FIG.
9 to 9 are developed cross-sectional views showing different shapes of fins in the seal guide according to the present invention, and FIG. 10 is an explanatory view showing the flow in the seal guide section according to the present invention. 1... Impeller, 2... Nozzle, 3... Casing, 4... Channel, 6
...Teif user, 7...axis, 11...
・Impeller inlet, 12... Impeller outlet, 13
...Outer edge of the impeller on the cylindrical surface, 14...
... Seal guide, 15 ... Feather, 20 ...
Fin, 23...Tangential direction, 24...
Absolute speed, 25... Absolute speed.

Claims (1)

[Claims] 1. In a mixed flow turbine equipped with an impeller without a front shroud, the outer periphery of the impeller near the outlet is formed on a cylindrical surface centered on the axis of the impeller shaft, and the outer edge of the impeller is surrounded. Fins are formed on the inner circumferential surface of the casing to control the flow of fluid flowing through the gap between the impeller blades and the casing, and the shape of the fins is designed to control the flow near the outer circumference of the impeller facing the inlet side of the fins. It is characterized by being formed to extend in a direction inclined from the tangential direction at an angle intermediate between the angle between the absolute velocity of the impeller and the tangential direction and the angle between the absolute velocity of the flow near the outer periphery of the impeller outlet and the tangential direction. A mixed flow turbine.