JP2002530574A - Low aspect ratio compressor casing structure - Google Patents

Abstract

A compressor (10) for a gas turbine engine has an inner surface proximate a tip of a row of rotor blades (16) and forming a plurality of circumferentially spaced grooves (36). A casing (26) is provided. Each groove (36) has a depth that is less than its width to increase off-design surge margins without adversely affecting compressor performance under normal operating conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

【Technical field】

The present invention relates to turbine engines, and more particularly, to an axial compressor and a centrifugal compressor applied to such an engine.

[0002]

[Background Art]

A compressor used in a gas turbine engine compresses a gas such as air and introduces the compressed gas into a combustion chamber of the gas turbine engine. Such compressors generally have a rotor section, which is provided with a plurality of radially extending blades which are mounted on a rotating shaft inside a casing or shroud as a fixed body. I have. By the rotation of the rotor section, gas is sucked into the rotor section, and the gas is sent to the combustion chamber of the gas turbine engine in a highly compressed state.

[0003] A typical phenomenon of such a compressor is generally a surge under a predetermined operating condition. Typically, surges are caused by destabilization of the air flow in the compressor. Compressor surges are typically characterized by a complete stoppage of the flow, a reversal of flow through the compressor, or a clear reduction in the ability of the airflow to handle the rotational speed during operation. The value of the air flow rate-pressure ratio when a surge occurs is called a surge point. The surge line connects all surge points, and defines the limit at which a stable airflow can be obtained according to the rotation speed. The compressor needs to be designed with a sufficient margin between an air flow-pressure ratio that can be actually operated and an air flow-pressure ratio that causes a surge phenomenon.

Therefore, various attempts have been made to increase the surge margin under all operating conditions. For example, Friedman et al., U.S. Pat.
U.S. Pat. No. 5,137,419 issued Aug. 11, 1992, discloses a plurality of circumferentially spaced slots on the inner surface of the casing. A compressor formed close to the tip is disclosed. The shapes and positions of the plurality of slots are set so as to extend upstream or downstream of the blade.

[0005] However, the compressor casing described in the above-mentioned patent publication is effective in improving the margin for surge, but on the other hand, the radial displacement of the gas flow is increased, and the pressure loss is increased.

[0006]

DISCLOSURE OF THE INVENTION

Therefore, one object of the present invention is to provide a compressor capable of improving a surge margin under normal operating conditions.

Another object of the present invention is to provide a compressor capable of improving air flow characteristics.

It is another object of the present invention to provide a compressor shroud structure capable of improving a surge margin.

According to the present invention, a compressor of a gas turbine engine has a shroud surrounding a rotor portion having a plurality of blades extending radially, and each blade is provided with a leading edge, a trailing edge, and a tip, On the inner surface of the shroud, a plurality of grooves arranged in parallel and spaced apart in the circumferential direction are formed in proximity to the tip, each groove has a depth D and a width W, and the depth D is It is set to less than half of the width W.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating a preferred embodiment of the present invention.

In the above drawings, particularly FIG. 1, a centrifugal compressor 10 according to one embodiment of the present invention is shown.

More specifically, the centrifugal compressor 10 has an impeller 12 mounted on a central shaft 14 so as to be rotatable around the axis, as is well known. The impeller 12 is provided with a plurality of blades 16 extending radially. As shown in FIG. 3, each blade 16 has a low or convex surface 20 and a high or concave surface 18 extending from a leading edge 22 to a trailing edge 24. Further, the centrifugal compressor 10 includes a blade 16
And a casing 26 including a cylindrical shroud 28 as a fixed body disposed in the vicinity of a radially outer edge, that is, a distal end 30 of the casing. A diffusion part 32 is provided at an outlet part of the impeller 12.

In the present invention, the shroud 28 is provided with a guide portion 34 having a plurality of grooves 36 that are spaced apart in parallel in the circumferential direction. As shown in FIGS. 4 and 5, each groove 36 has a depth D, a width W, and a length L, and the leading edge 22 and the trailing edge 2 of the blade 16.
The shape and the position are set so as not to extend over four. Groove 36
Are relatively long straight side edges 38 and semi-circular ends 40 facing each other.
And

Further, it has been found that by making the depth D of the groove 36 smaller than half the width W, the surge margin can be improved without adversely affecting the overall compression efficiency. Further, by setting the ratio D / W to less than 0.5, the gas constantly passes through the groove 36 during operation of the compressor 10, thereby preventing accumulation of dust and the like in the groove 36. Thus, the main rated performance of the compressor 10 is ensured. More specifically,
Experiments have shown that setting the ratio D / W in the range of about 0.15 to about 0.35 further improves the surge margin. The dimensions of the groove 36 as a typical example according to the present invention are shown below.

[0015]

D = 0.075 inch W = 0.225 inch L = 0.410 inch As shown in FIGS. 4 and 5, the adjacent groove 36 is one of the shroud wall portions connecting the two grooves 36. Are separated by a land 37 as a part. Even when the distance between the grooves 36, specifically, the width A of the land 37 is equal to or smaller than the depth D of the groove 36, the surge margin is improved. Typically, the land width A is set in a range from about 0.06 inches to about 0.08 inches.

As shown in FIG. 3 and FIG. 4, the groove 36 is oriented in a direction orthogonal to the average angular direction in the blade longitudinal direction within a range of ± 15 °, and the center axis 14 of the centrifugal compressor 10 is In a direction of about 45 ° with respect to. Each blade 16 always extends over at least three grooves 36.

During operation, gas moves from the high pressure surface 18 side of the blade 16 to the low pressure surface 20 side. The high-pressure gas activates the low-pressure gas on the low-pressure surface 20 side of the blade 16, thereby delaying the stall under operating conditions that deviate from the design values. The parameters of the groove 36, such as the length L, width W, depth D, and the arrangement angle thereof, are set so as to allow sufficient flow to increase the stall allowance outside the operating speed range. Such a groove 3
By virtue of 6, the high energy gas is continuously supplied to the low pressure surface 20 side beyond the desired blade length. As a result, the stall at the tip is delayed, and the pumping ability of the blade is improved. As a result, the efficiency of the compressor 10 under operating conditions that deviate from the design values is improved. Under operating conditions within the design range, the turbulence of the flow caused by the groove 36 is minimized by minimizing the radial component of the gas flow velocity. As a result, losses due to the radial component of the flow velocity are minimized. By optimizing the direction of flow velocity based on the direction of the groove and minimizing the flow rate based on the depth of the groove, the secondary flow is kept to a minimum, resulting in a performance at operating conditions within the design range Loss is reduced or eliminated.

Furthermore, noise in a high band is reduced at the same time. In addition, the groove 36 suppresses a change in performance due to the radial clearance of the blade tip (gap between the tip of the blade 36 and the inner surface of the shroud 28). Although the clearance at the tip of the blade is slightly increased by several thousandths of an inch, such a rate of increase in the radial gap is sufficiently small compared to the depth D of the groove 36. I can say.

In one embodiment of the present invention, circumferentially spaced grooves 36 are formed during machining of shroud 28 and then joined to the outer surface of shroud 28 as shown in FIG. Surrounded by a liner 42. Therefore, the liner 42 forms the bottom surface of each groove 36.

As described above, the case where the present invention is applied to the centrifugal compressor has been described.
The casing structure having a low aspect ratio described above is suitably applied to an axial compressor.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing a part of a compressor of a gas turbine engine provided with a shroud according to the present invention.

FIG. 2 is a perspective view of the shroud.

FIG. 3 is a side view of the shroud.

FIG. 4 is a top view partially showing a radially inner surface of the shroud.

FIG. 5 is a sectional view taken along the line 5-5 in FIG. 4;

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] October 6, 2000 (2000.10.6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

More specifically, the centrifugal compressor 10 has an impeller 12 mounted on a central shaft 14 so as to be rotatable around the axis, as is well known. The impeller 12 is provided with a plurality of blades 16 extending radially. As shown in FIG. 4 , each blade 16 has a low or convex surface 20 and a high or concave surface 18 extending from a leading edge 22 to a trailing edge 24. Further, the centrifugal compressor 10 includes a blade 16
And a casing 26 including a cylindrical shroud 28 as a fixed body disposed in the vicinity of a radially outer edge, that is, a distal end 30 of the casing. A diffusion part 32 is provided at an outlet part of the impeller 12.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

[0015]

[Number 1] As shown in D = 0.075 inches (0.19cm) W = 0.225 inches (0.57cm) L = 0.410 inches (1.04 cm) 4 and 5, adjacent The grooves 36 are separated by lands 37 that are part of the shroud wall connecting the grooves 36. Even when the distance between the grooves 36, specifically, the width A of the land 37 is equal to or smaller than the depth D of the groove 36, the surge margin is improved. Typically, the width A of the land is set in the range of about 0.06 inches (0. 152cm) to about 0.08 inches (0.203 cm).

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

As shown in FIGS. 3 and 4, the groove 36 is oriented in a direction orthogonal to the chord line of the tip of the blade airfoil within a range of ± 15 °, and the centrifugal compressor 10 Extend in a direction of about 45 ° with respect to the central axis 14. Each blade 16 always extends over at least three grooves 36.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

Furthermore, noise in a high band is reduced at the same time. In addition, the groove 36 suppresses a change in performance due to the radial clearance of the blade tip (gap between the tip of the blade 36 and the inner surface of the shroud 28). The clearance at the tip of the blade is slightly increased by several thousandths of an inch (one thousandth of an inch is 0.00254 cm ) . Depth D
Can be said to be sufficiently small compared to.

[Procedure amendment 6]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

FIG. 3

FIG. 4

FIG. 5

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Claims (9)

[Claims] 1. A shroud enclosing a rotor portion having a plurality of radially extending blades, each blade having a leading edge, a trailing edge, and a tip, and spaced circumferentially parallel to an inner surface of the shroud. A plurality of grooves to be arranged are formed near the tip, each groove having a depth D and a width W, wherein the depth D is less than half of the width W. Compressor. 2. Each of the grooves has a pair of front and rear ends, wherein the front end is located substantially downstream of the front edge of the blade, and wherein the rear end is 2. The blade of claim 1, wherein said blade is disposed substantially upstream of said trailing edge.
A compressor according to claim 1. 3. The compressor according to claim 1, wherein D / W is set in a range from about 0.15 to about 0.35. 4. The compressor according to claim 1, wherein the groove is oriented in a direction substantially orthogonal to the blade within a range of ± 15 °. 5. The compressor according to claim 4, wherein said groove extends in a direction approximately 45 ° with respect to a longitudinal axis of said compressor. 6. The compressor according to claim 1, wherein the distance between the grooves is equal to or smaller than D. 7. The compressor according to claim 1, wherein each groove has a pair of side walls extending linearly. 8. The compressor according to claim 7, wherein each of the grooves has semicircular arc-shaped ends facing each other. 9. The compressor according to claim 1, wherein each of said blades always extends over at least three grooves.