JPS5960009A - Axial flow turbo machine - Google Patents

Abstract

PURPOSE:To reduce the loss of energy of diffuser by designating the ratio of the axial direction distance of the axial direction end of the diffuser of an axial flow turbo machine and the axial direction of the side wall of an exhaust chamber to the axial direction distance between the outlet end of the final stage blade and the side wall of the exhaust chamber to be within a given value range. CONSTITUTION:A diffuser 7 provided extensionally from a casing 3 into the exhaust chamber 5 of an axial flow turbo machine is shaped into a form such that it extends toward the axial line direction of a rotor 1, then gradually curves outwards, and finally turns toward the radial direction. The ratio of the axial direction distance X between the axial direction end of the diffuser 7 and the side wall 9 of the exhaust chamber 5 to the axial direction distance L between the outlet end of the final stage mobile blade 2 and the side wall 9 of the exhaust chamber 5 is designated to the relationship 0.5<=X/L<=0.8. Therefore, the axial direction length of the rotor 1 can be shortened, and energy loss in the diffuser 7 can be lessened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an axial flow turbomachine whose axial length is limited, such as a steam turbine, and particularly to an improvement in the shape of a diffuser of an exhaust chamber thereof.

[Technical background of the invention and its problems]

In general, in axial flow turbomachines such as steam turbines, fluid that has completed work is not discharged in the axial direction at the high-pressure intermediate-pressure stage outlet and the low-pressure stage outlet, but in the radial direction perpendicular to the axial direction. There are many. That is, in the exhaust chamber of an axial flow turbomachine, the high-speed fluid exiting the rotor blades is oriented almost at right angles and guided to the exhaust port while being decelerated, resulting in loss due to wall friction and vortex flow. Reducing this loss in the exhaust chamber is an important issue in improving the performance of turbomachines.

FIG. 1 shows a conventional exhaust chamber of the aforementioned axial flow turbomachine. In FIG. 1, a rotor 1 has a plurality of rotor blades 2 protruding in its circumferential direction, and stator blades 4 protruding from a casing 3 surrounding the rotor 1 are opposed to the rotor blades 2. and make up a paragraph. Further, an exhaust chamber 5 having an exhaust port 6 is formed at the exit of the final stage, and the casing 3 extends curvedly in the axial and radial intermediate directions of the exhaust chamber 5 to create a diffuser 7. It consists of Note that a middle portion of the exhaust chamber 5 defined by the diffuser 7 is a scroll chamber 8.

According to the above-mentioned configuration, the fluid that has completed its work in the turbine stage converts the kinetic energy of the fluid into pressure energy in the diffuser 7 and decelerates it without wasting it, and then is led to the scroll chamber 8, and from this scroll chamber 8 to the exhaust port. 6.

However, in the conventional device described above, since the exhaust chamber 5 having a large volume is formed, the rotor 1
This increases the length of the rotor, requires more rotor material, increases costs, and requires a larger installation space for the axial flow turbomachine. Furthermore, if the length of the rotor 1 is increased, its natural frequency becomes smaller, and there is a risk of resonance with the rotational speed of the rotor 1.

Therefore, the length of the rotor 1 is shortened so that the natural frequency of the rotor 1 is greater than the rotational speed of the rotor 1.
Axial flow turbomachines as shown in the figure have been used conventionally.

However, in the case shown in FIG. 2, the length of the rotor l is made shorter than that shown in FIG. It's dark.

As a result, when the fluid that has completed its work is led to the scroll chamber 8, the direction of the flow changes rapidly from the axial direction to the radial direction, so that the fluid that has completed its work collides with the side wall 9 of the exhaust chamber 5. , all of the kinetic energy of the fluid becomes thermal energy and disappears, resulting in a large loss.

[Purpose of the invention]

The present invention eliminates the drawbacks of the conventional ones mentioned above,
An object of the present invention is to provide an axial flow turbomachine in which the axial length of the rotor is short and energy loss is small (3).

[Summary of the invention]

According to the present invention, the above-mentioned objective is to satisfy the following equation: 0.
This is achieved by reducing energy loss due to fluid friction by satisfying =L= 5<'<0.8.

[Embodiments of the invention]

The present invention will be explained below with reference to embodiments shown in the drawings.

FIG. 3 shows an embodiment of the present invention, and the shape of the exhaust chamber 5 is smaller than that of FIG. 1, similar to the conventional one explained in FIG. In this case, the related dimensions of the diffuser 7 and the exhaust chamber 5 are special.

That is, the diffuser 7 extending from the casing 3 into the exhaust chamber 5 covers the inside of the exhaust chamber 5 of ξ. and an axial distance X between the axial end of the diffuser 1 and the side wall 9 of the exhaust chamber 5 extending in the radial direction;
The ratio T of the axial distance between the outlet end of the final stage rotor blade 2 and the side wall 9 of the exhaust chamber 5 is closely related to energy loss.

Assuming that the distance is constant, the larger the distance X is, the shorter the effective length of the diffuser 7 will be, and the kinetic energy will not be effectively decelerated and will be lost as heat, increasing energy loss. . This relationship is shown by the dashed line A in FIG.

Further, as the distance X becomes smaller, the fluid in the lower outlet & of the diffuser 7 is compressed by the side wall 9 of the exhaust chamber 5, and the flow velocity increases. This relationship is shown by dashed line B in FIG.

The energy loss at the output lower part a of the diffuser 7 can be determined by combining the chain line A and the broken line B in FIG. 4, and this energy loss is shown by the solid line C in FIG. This solid line C
According to , when - becomes thicker than 0.8, the effective length of the diffuser 7 becomes shorter, resulting in a rapid increase in energy loss.
Also, when T becomes smaller than 0.5, the side wall 9 of the exhaust chamber 5
Energy loss in the exhaust chamber 5 rapidly increases due to fluid friction in the exhaust chamber 5. Therefore, it is desirable to set the value of 0.5≦÷≦0.8 (1).

Next, the radial end of the diffuser 7 and the exhaust chamber 50
The ratio Y between the radial distance Y to the peripheral wall 10 and the distance X is also closely related to energy loss.

That is, as is clear from the experimental results shown in FIG. 5, this relationship holds that when T is smaller than 1.0, the scroll chamber 8
The flow velocity of the fluid at the 0 inlet 8a increases, and the sieve energy loss increases due to fluid friction on the circumferential wall 10 of the exhaust chamber 50.
Furthermore, when T becomes larger than 1.2, as shown in FIG. 6, the fluid separates at the tip of the diffuser 7 and a vortex 11 is generated, resulting in a sharp increase in energy loss. Therefore, it is desirable that the value of Y be set so as to satisfy 1.0≦÷≦1.2 (2).

According to the above-described configuration, the distance X%Y%L is mutually expressed by the formula (1
), By setting the dimensions of each member to satisfy (2), the fluid leaving the final stage rotor blade 4 is decelerated by the diffuser 7 without losing much of its kinetic energy. It is guided to the outlet lower a, then guided from the diffuser 7 into the scroll chamber 8, rotates within the scroll chamber s with almost no energy loss, and is discharged from the outlet 6.

Therefore, an axial flow turbomachine with excellent energy efficiency can be obtained.

〔Effect of the invention〕

As explained above, the axial flow turbomachine according to the present invention has
Since the axial distance X between the axial end of the diffuser and the side wall of the exhaust chamber and the outlet end of the final stage rotor blade and the side wall of the exhaust chamber satisfy the formula 0.5≦÷≦0,8, Even if the length of the rotor in the axial direction is shortened, an excellent effect is achieved in that energy loss in the diffuser can be extremely reduced.

[Brief explanation of drawings]

1 and 2 are longitudinal sectional views showing main parts of a conventional axial turbomachine, FIG. 3 is a longitudinal sectional view showing an embodiment of an axial turbomachine according to the present invention, and FIGS. 4 and 5 Each figure is a graph showing energy loss, and FIG. 6 is a longitudinal cross-sectional view showing the state of fluid flow near the tip of the diffuser. 1... Rotor, 2... Motion picture, 3... Casing,
4... Stationary blade, 5... Exhaust chamber, 7... Diffuser, 8... Scroll chamber. Applicant's agent Hisada Hatano / Head No. 2 Diagram ξi 弗 3 Diagram

Claims (1)

[Claims] 1) An exhaust chamber is provided for deflecting and discharging the fluid discharged from the final stage rotor blade in a radial direction from the axial direction of the rotor, and the end of the casing is extended into the exhaust chamber to form a diffuser. In the axial flow turbomachine, the axial pressure #Ix between the axial end of the diffuser and the side wall of the exhaust chamber, and the axial distance between the outlet end of the final stage rotor blade and the side wall of the exhaust chamber. An axial flow turbomachine characterized in that the equation 0.5≦+≦0.8 t- is satisfied. 2) The radial distance Y between the radial end of the diffuser and the peripheral wall of the exhaust chamber and the axial distance X are 1.0≦÷≦
1.2. The axial flow turbomachine according to claim 1, wherein the axial flow turbomachine satisfies condition 1.2.