JPS59505A - Steam turbine - Google Patents

Abstract

PURPOSE:To reduce the dynamic pressure caused by the steam revolution inside of a labyrinth and contrive the decreasing of a steam leakage quantity of the titled device by a method wherein a revolution preventing tooth parallel to the axial direction of a rotating body is provided as intersectional with the tooth of a labyrinth packing. CONSTITUTION:Plural revolution preventing teeth 6 parallel to the axial direction are provided at several locations in circumferential direction as intersectional with plural ring-shaped packing teeth 4 provided on a packing body material 5 of a labyrinth packing. The height of said revolution preventing teeth 6 are firmed as the same height of said packing teeth 4 or less than said height.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a steam turbine having an improved labyrinth packing that prevents leakage of steam from around a rotating body.

[Technical background of the invention and its problems]

The labyrinth packing type is generally used as a leakage prevention device for steam turbines at the following three locations as shown in FIG. That is, the first is the rotor casing end gland packing (1), the second is the rotor nozzle diaphragm inner diameter nozzle labyrinth packing (2), and the third is the radial spill strip between the blade tip and the nozzle diaphragm (3). Note that (11 is a turbine rotor, and aυ is a turbine casing.

FIG. 2 shows a longitudinal cross-sectional view of the conventional labyrinth packing used above. The labyrinth tooth (4) is attached to the packing base material (5
) is machined or caulked to the packing base material (5), and a plurality of sheets are installed perpendicularly to the steam outflow direction indicated by the arrow. By making the radial gap between the rotor (111<or blade tip) and the labyrinth tooth (4) a minute gap that can be safely punched, the differential pressure P before and after the labyrinth seal
ltP! This prevents leakage by providing flow path resistance to the steam that is about to flow.

The leakage amount is calculated according to Martin's (101) below.

! E is the labyrinth leakage amount (kf/H) K is the current coefficient (see curve (7) in Figure 3) f is the leakage area (cIrP) Here, f=π diameter (ffi) CI is the packing radial clearance (cIR) where Pl is the packing inlet pressure (kglcrl abs)
P is the pressure on the packing outlet side (kf/J abs) N is the number of packing teeth υ1 is the specific volume on the packing inlet side (-"/kf) The above leakage amounts are the thermal energy of the steam inside the turbine → blade rotation torque → Since the shaft end power bypasses the energy conversion system and cannot obtain regular work, its reduction is important for increasing turbine efficiency.

As an example, FIG. 4 shows the ratio of leakage loss to loss in a conventional general steam turbine, and the total amount reaches approximately 4196.

[Purpose of the invention]

An object of the present invention is to provide an efficient steam turbine by reducing the amount of steam leaking from the labyrinth.

[Summary of the invention]

In the present invention, by providing anti-swivel teeth that intersect with the annular packing teeth and are approximately parallel to the axial direction of the rotating body, steam swirl within the labyrinth is prevented, and the dynamic pressure due to the swirl is reduced. This reduces the amount of steam leakage.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 5 and 6. Note that the schematic elevational view of the steam turbine of this embodiment is similar to FIG. 1 described as a conventional example, so please refer to this as well.

In this embodiment, a plurality of annular packing teeth (4) K (which may be divided in the circumferential direction for convenience of assembly) are provided in parallel in the axial direction on the packing base material (5).
Rotation prevention teeth (6) that intersect and are substantially parallel to the axial direction (some inclination is acceptable) are provided at several locations in the circumferential direction. The height of this anti-swivel tooth (6) is the same as or lower than that of the packing tooth (4), so that the anti-swivel tooth 6) Reduce the chances of contact with the rotating body.

Next, the effect will be explained.

The labyrinth packing configured in this way prevents the steam between adjacent packing teeth (4), (4) from swirling in the direction of arrow a as the rotor Q1 (or blades) rotates. . This eliminates the conventional drawbacks of a drop in dynamic pressure due to swirling, an increase in differential pressure, and an increase in the amount of steam leakage. The arrow indicates the direction of steam leakage.

The pressure increase due to no rotation is expressed by the following equation (102), (10
3) The relationship is as shown in Eq.

,..., Pb > Pa...
...(103) P3 is the pressure when there is a swirling flow Pb is the pressure when there is no swirling flow ■ a is the swirling flow velocity V is the specific volume l is the gravitational acceleration The above action results in a decrease in the flow coefficient of the labyrinth packing. , is shown as curve (8) in Figure 3, and a reduction in the leakage amount can be obtained in equation (101).

However, when inserting the rotation prevention plate (6),
) is generally a composite of multiple circular arcs rather than a single circular ring around the entire circumference, so it is easy to implement as it only needs to be inserted between each circular arc.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but may include the following without changing the gist thereof:
Of course, it can be implemented with various modifications.

〔Effect of the invention〕

As explained above, according to the present invention, by using the anti-swivel teeth and a structure that prevents steam from swirling within the labyrinth, the dynamic pressure caused by swirling is reduced, and the amount of steam leakage is reduced. A highly efficient steam turbine can be provided.

[Brief explanation of the drawing]

Fig. 1 is a cutaway elevational view of essential parts showing the schematic structure of a steam turbine common to the conventional steam turbine and an embodiment of the present invention, Fig. 2 is a vertical sectional view showing the labyrinth packing in the conventional case, and Fig. 3 is a flow rate A curve diagram showing coefficients, FIG. 4 is a classification diagram showing the ratio of turbine loss, FIG. FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1... Rotor/casing end grand labyrinth para east 2... Rotor/nozzle diaphragm inner diameter nozzle labyrinth patch skin 3... Radial spill strip between vane tip/nozzle diaphragm 4... Labyrinth @ 5.・Packing base material 6
... Rotation prevention tooth 10 ... Rotor 11 which is a rotating body ... Turbine casing Fig. 1, 1 Fig. 2, ^ Fig. 3 One) Force lIQ gap Fig. 5 Fig. 6

Claims (1)

[Claims] In a steam turbine equipped with a labyrinth packing as a device to prevent steam leakage from around the rotating body, the labyrinth packing intersects with the annular packing teeth surrounding the outer periphery of the rotating body and rotates parallel to the axial direction of the rotating body. A steam turbine characterized by a groove provided with preventive teeth.