JPH02298604A - Blade tip leakage preventing device for axial flow fluid machine - Google Patents

Abstract

PURPOSE:To reduce a force acting upon a seal member and rotor blades whose tip ends are opposed to the seal member upon contact therebetween by locking the seal member in a groove formed in a casing so that the seal member may be moved relatively freely only in a radial direction. CONSTITUTION:Rotor blades 1 are rotated together with a rotor 2 so as to ensure a predetermined clearance Cl between itself and an abradable seal 4 attached to a stationary casing 3. The attaching part 5 of the seal 4 is formed in a T-like cross-sectional shape, and is then fitted in a T-like cross-sectional shape groove 6 formed in the casing 3. The attaching part 5 makes contact, at its radial and axial joint surfaces 7, 8, with the groove 6. Further, a spring 9 is disposed between the attaching part 6 and the groove 6. With this arrangement, the seal 4 is moved radially outward when the clearance Cl becomes zero, that is, the rotor blades 1 and the seal 4 make contact with each other, thereby it is possible to reduce a force acting upon both members 1, 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a device for preventing blade tip leakage of an axial fluid machine with an improved abradable seal mounting structure.

(Prior art) In axial fluid machines such as compressors and turbines, it is structurally necessary to provide a certain amount of clearance between the tip of the rotor blade that rotates at high speed and the casing. Since losses caused by leakage of working fluid greatly affect the performance of axial fluid machines, efforts have been made to reduce these losses. This leak, as mentioned above! ? Since there is a gap between the tip of II''A and the casing, it is clear that the loss is reduced by reducing this gap.

However, this amount of clearance is complicatedly influenced by elongation of the rotor blades due to centrifugal force, deformation of the blades or casing due to heat, and the rise of ijX of the rotor during one revolution, and changes depending on the operating state of the machine. Moreover, for this reason, even the child side whose gap amount is accurate will be in trouble. Furthermore, in the unlikely event that the rotor blades come into contact with the casing and are damaged.

The casing is closest to the minimum clearance amount (i.e., !fi]'A that is considered theoretically possible, including the possibility of a serious accident affecting the entire machine and problems with machining accuracy. It is necessary to provide a certain margin for the amount of clearance (the amount of clearance is the minimum required under the operating conditions). Therefore, in reality, there is a limit to how small this gap can be made. Therefore, in order to reduce this leakage loss and improve the performance of fluid machinery, several methods have been devised and put into practical use. However, among these methods, the method of arranging an abradable seal member (abradable seal) at a position facing the rotor blade of the casing is the simplest and most effective and is therefore quite widely used.

(For example, US, PAT [ENT No. 3,580,6
92 or documents such as AGAPD-CP-237) This method allows even if the tips of the rotor blades contact each other,
This method prevents damage to the rotor blades due to wear or deformation of the abradable seal, but by using this method, it is possible to reduce the above-mentioned clearance margin, and it is also possible to It is also possible to set the amount of clearance so that the blade and the abradable seal are in contact with each other.

This abradable seal has been devised to use honeycomb, sintered metal fibers, soft metal coating, etc., but when honeycomb is used, it also reduces leakage due to the labyrinth effect. You can expect it.

(Problem to be solved by the invention) Although it is expected that the blade tip leakage loss of an axial fluid machine can be reduced by using an abradable seal in this way, when the abradable seal and the rotor blade come into contact, It is desirable that the force exerted on the rotor blade be as small as possible in order to prevent damage to the blade, and when selecting an abradable seal, careful consideration was needed to this point.

This becomes an important problem especially when this technology is applied to compressor rotor blades with thin blade thickness. On the other hand, the force applied to the rotor blades varies greatly depending on the contact situation. Furthermore, when using an abradable seal member and expecting a labyrinth effect, it is undesirable for the rotor blades to come into contact and deform the honeycomb.

For the reasons mentioned above, there has been a desire for a method to prevent excessive force from being applied even when the abradable seal and the rotor blade come into contact with each other, thereby preventing damage to the blade or the abradable seal.

An object of the present invention is to provide an abradable seal mounting part that can maintain a relative relationship between the rotor blade and the abradable seal so that no excessive force is applied even when the abradable seal and the tip of the rotor blade come into contact with each other. The present invention provides a blade tip leakage prevention device for an axial fluid machine.

[Structure of the invention]

(Means for Solving the Problems) In the blade tip leakage prevention device for an axial fluid machine according to the present invention, abradable seals divided in the circumferential direction are not fixedly attached to the casing.

It is characterized in that it is mounted by a mounting portion whose axial position is limited by a groove cut in the circumferential direction of the casing, and which allows relatively free movement in the radial direction.

(Function) According to the present invention, since the abradable seal is installed relatively freely in the radial direction, there is a large amount of contact between the rotor blade tip and the abradable seal, and excessive force may not be applied. In such cases, the abradable seal can move radially outward to reduce this force and prevent the wing or abradable seal from taking over.

(Example) The present invention will be described below with reference to an example shown in FIGS. 1 and 2. In FIG. 1, f! The lJ blade 1 rotates together with the rotor 2, and maintains a clearance amount CIA from the abradable seal 4 attached to the stationary casing 3. .

In the present invention, the mounting portion 5 of the abradable seal has a T-shaped cross section as shown in FIG. 1, and fits into a groove 6 provided in the casing which also has a T-shaped cross section. It is rare. The mounting portion 5 is in contact with the groove 6, the radial joint surface 7, and the axial joint 8, and the radial joint 7 prevents movement in the radial direction.
Movement to the left in the axial direction is restrained by the axial joint surface 8.

In Fig. 1, we are considering a situation where the pressure is higher on the right side than on the left side of the figure, that is, the pressure is higher on the downstream side than the upstream side of the working fluid, so the abradable seal 4 and the mounting part 5 are pressed against the left side of the figure, and in the axial direction. The position of is completely constrained. - Some radial outward movement of the oyster is allowed. Further, a spring 9 is arranged between the mounting portion 5 and the mounting groove 6.

Further, in the present invention, the abradable seal 4 and the mounting portion 5 are divided in the circumferential direction and have an arcuate cross-sectional shape, as shown in FIG. The spring 9 has the simplest L-shape.

In the blade tip leakage prevention device for an axial fluid machine of the present invention configured as described above, when the clearance QCQ decreases due to changes in operating conditions and cfl=o, the tip of the dynamic fluid R1 and the The braidable seal 4 will come into contact.

If the clearance amount CQ further decreases and becomes negative,
If the abradable seal 4 were fixedly attached to the casing 3, the abradable seal 4 would be scraped off by the rotor blade 1 by approximately lll. At this time, the speed ACI at which the rotor blade tip enters the abradable seal
Δ has a large influence on the force exerted by II. That is, if the clearance amount CQ suddenly decreases, a large force will be generated, causing damage to the blade.

According to the present invention, when the clearances M and CQ suddenly decrease and come into contact, the abradable seal 4 and the mounting portion 5 move radially outward to reduce the applied force. I can do it. In the present invention, the mounting portion 5
The spring 9 disposed between the abradable seal 4 and the mounting groove 6 presses the mounting portion 5 radially inward, thereby increasing the accuracy of the radial position of the abradable seal 4 and acting upon contact. The force and amount of wear of the abradable seal 4 can be controlled.

In this way, in the present invention, even when the tip of the rotor blade 1 and the abradable seal 4 come into sudden contact and there is a risk of damage to the blade, the abradable seal 4 is relatively free in the radial direction. Since it is locked by the mounting part 5 which is movable in the radial direction, it is possible to move radially outward and reduce the force acting on the mounting part 5.

Note that in the present invention, the abradable seal member 4
However, when a honeycomb-shaped sealing member is used, a reduction in the amount of leakage due to the labyrinth effect can also be expected.

Furthermore, instead of the honeycomb-shaped seal member, an abrasive seal member made of porous material, metal fiber, or other abrasive material may be used, and it is also possible to use a rail member whose surface is coated with a soft metal such as aluminum. You can expect the following effects.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, even when the tip of the rotor blade and the seal member suddenly come into contact and a large force is applied to the blade and the seal member, there is a risk of damage. The relatively free radial mounting of the seal member and mounting allows for radial outward movement of the seal member to reduce forces on the wing and seal member and prevent damage. be.

[Brief explanation of drawings]

FIG. 1 is a thermal cross-sectional view showing an embodiment of the blade tip leakage prevention device for an axial fluid machine according to the present invention, and FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1. 1... Moving blade 2... Rotor 3...
・Casing 4...Abradable seal 5...Mounting part 6...Mounting groove 9...
Spring CQ...Clearance amount agent
Patent Attorney Noriyuki Chika Yudo Ken Daishimaru

Claims (1)

[Claims] A seal member divided in the circumferential direction is arranged in a portion of the casing facing the tip of the rotor blade, and this seal member has axial movement limited by a circumferential groove provided in the casing, and radial movement limited. A blade tip leakage prevention device for an axial fluid machine, characterized in that the blade tip is locked so as to be relatively free.