A combined casing treatment structure for an axial flow compressor

Abstract

The present invention discloses a combined casing treatment structure for an axial flow compressor, which includes the compressor rotor blades and the corresponding casing treatment structure. Two circumferential grooves are opened on the casing wall corresponding to the top of the compressor rotor blades, which are respectively located upstream and downstream of the leading edge of the blade tip. Above the circumferential grooves, a number of circular arc treatment slots that are circumferentially centrosymmetric are superimposed. The front end of the circumferential groove upstream of the leading edge is overlapped with the front end of the treatment slot and smoothly transitioned, and the rear end of the circumferential groove downstream of the leading edge is overlapped with the rear end of the treatment slot and smoothly transitioned. By reasonably combining the circumferential grooves and the axial slots, the present invention enables the main flow fluid at the blade tip to flow into and out of the treatment slots more smoothly, improves the ability of expanding and stabilizing, and reduces the flow loss.

Description

Technical Field

[0001] The present invention belongs to the field of turbomachinery, and particularly relates to a combined casing treatment structure for an axial compressor. Background Art

[0002] The flow process in the clearance region of a gas turbine compressor is very complex, and the loss caused by the clearance flow accounts for a large proportion of the total energy loss of the rotor blades and compressor stages. Moreover, the performance of the compressor is highly sensitive to the tip clearance. During operation, an increase in the clearance usually leads to a decline in the compressor performance. During actual service, the tip clearance may increase temporarily or permanently, thereby affecting the economy and stability of the gas turbine operation.

[0003] The end-wall treatment technology is an earlier studied and successfully applied method for controlling the compressor clearance flow, which can effectively broaden the compressor stability margin. Generally speaking, the adverse effect of the circumferential groove type casing treatment on the compressor efficiency is less than that of the axial slot type casing treatment, but the stability enhancement ability is weaker. This is because the space in the circumferential groove is small and a jet with strong energy cannot be formed. If the design characteristics of the axial slot type casing treatment are borrowed to enhance the jet intensity in the circumferential groove of the compressor, the stability enhancement ability can be enhanced while keeping the efficiency loss as small as possible. Summary of the Invention

[0004] The purpose of the present invention is to provide a combined casing treatment structure for an axial compressor based on the position of the leading edge of the rotor tip and the tip clearance size of the subsequent stages of the compressor. By reasonably combining the circumferential groove and the axial slot, the tip mainstream fluid can flow into and out of the treatment groove more smoothly, improving the stability enhancement ability and reducing the flow loss.

[0005] The present invention is implemented by adopting the following technical solutions:

[0006] A combined casing treatment structure for an axial compressor includes the compressor rotor blades and the corresponding casing treatment structure. Two circumferential grooves are opened on the casing wall corresponding to the top of the compressor rotor blades, located upstream and downstream of the tip leading edge respectively. Above the circumferential grooves, a number of circular arc treatment slots symmetrically arranged along the circumferential center are superimposed. The front end of the circumferential groove upstream of the leading edge is overlapped and smoothly transitioned with the front end of the treatment slot, and the rear end of the circumferential groove downstream of the leading edge is overlapped and smoothly transitioned with the rear end of the treatment slot.

[0007] A further improvement of the present invention lies in that the widths of the two circumferential grooves upstream and downstream are both 5%-10% of the axial chord length. The rear end of the upstream circumferential groove is about 4%-8% of the axial chord length away from the leading edge of the rotor tip, and the front end of the downstream circumferential groove is 4%-8% of the axial chord length away from the leading edge of the rotor tip. The depths g of the two circumferential grooves are both 4%-8% of the axial chord length, the width d of the circumferential groove is 4%-8% of the axial chord length, the included angle between the downstream circumferential groove and the upper end wall of the rotor in the meridional plane is α1, and the included angle between the upstream circumferential groove and the upper end wall is α2.

[0008] A further improvement of the present invention lies in that for the axial slot above the circumferential groove, the contour of the axial slot is designed in the meridional plane. Taking the leading edge point within the range of 90%-98% of the blade height as the center O1, an arc with a radius of r1 is made. The left endpoint of this arc is denoted as A, and the right intersection point with the parallel line g away from the upper part of the casing, which is the upper boundary of the circumferential groove, is denoted as B, and it is denoted as the arc

[0009] A further improvement of the present invention lies in that the arc The included angle between the arc and the upper boundary of the circumferential groove is β1, and β1 is equal to α1, and the value range is 30°-60°. Correspondingly, the value range of the radius r1 of this arc is: (τ + h) / cos30° ≤ r1 ≤ (τ + h) / cos60°, where τ is the size of the rotor tip clearance and h is the distance between the center O1 and the tip.

[0010] A further improvement of the present invention lies in that the connection line between the left endpoint A of the arc and the center O1 intersects the upper boundary of the circumferential groove at point D. The included angle between AD and the radial direction is θ, and the value range of θ is 0°-30°.

[0011] A further improvement of the present invention lies in that taking the midpoint of the connection line AD as the center O2 and AD as the diameter, an arc is made to intersect the upper boundary of the circumferential groove at point C, and it is denoted as the arc

[0012] A further improvement of the present invention lies in that the arc and the arc Together form the contour of the axial slot in the meridional plane. The axial slot type casing treatment formed by this contour has an included angle δ with the radial direction in the range of 30°-60°. The number of treatment slots is taken as 3-5 times the number of rotor blades, and the circumferential opening ratio Φ is taken as 30%-70%. The opening ratio Φ refers to the ratio of the opening area of the treatment slots on the casing to the area of the casing within the axial range where the treatment slots are located.

[0013] A further improvement of the present invention lies in that the radius r2 of the contour of the axial slot in the meridional plane is r2 = (r1 - DO1) / 2 = [r1 - (τ + h) / cos(θ + γ)] / 2, where γ is the included angle between the casing wall and the axial direction.

[0014] A further improvement of the present invention lies in that the included angle β2 between the tangent line at point C of the circular arc is equal to the value of α2 at the upper bound of the circumferential groove, and β2 = θ + γ.

[0015] The present invention has at least the following beneficial technical effects:

[0016] Compared with the prior art, the design configuration of the present invention uses circular arcs with smooth connections at both ends to construct axial treatment slots, and two circumferential grooves are opened below the axial slots. The downstream circumferential groove enables the mainstream fluid to enter the treatment slot relatively gently, and returns to the upstream through the cavity connected by the two circular arcs of the treatment slot, and enters the mainstream from the upstream circumferential groove. The mainstream flows into and out of the treatment slot at a relatively low speed through the circumferential groove, reducing the circulation loss in the slot and the loss of mixing with the mainstream, thereby widening the stability margin of the compressor on the premise of having a relatively small impact on efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a conventional circumferential groove type casing treatment structure.

[0018] Figure 2 is a schematic diagram of a conventional axial slot type casing treatment structure.

[0019] Figure 3 is a schematic diagram of the meridian plane structure of the present invention.

[0020] Figure 4 is a schematic diagram of the axial view of the present invention.

[0021] Figure 5 is a schematic diagram of the top view of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0023] As Figures 3 to 5 shown, a combined casing treatment structure for an axial compressor provided by the present invention includes:

[0024] 1) In the meridian plane view of the rotor, draw a parallel line at a distance g from the casing, which is called the upper bound of the circumferential groove, and the value range of g is:

[0025] g ∈ [5%c x,tip, 15% c x,tip

[0026] Among them, c x,tip is the axial chord length of the rotor tip.

[0027] 2) Take the leading edge points within the range of 90% - 98% of the blade height as the center O1, that is, the distance h between O1 and the leading edge of the rotor tip is 2% - 10% of H, where H is the rotor blade height;

[0028] 3) According to the center O1 determined in step 2), make an arc with a radius of r1 in the meridian plane, so that the arc intersects the upper bound of the circumferential groove at B;

[0029] 4) According to the B point determined in step 2), the included angle between the tangent line at point B and the upper bound of the circumferential groove can be known, that is, the included angle between the rear end of the treatment groove and the upper bound of the circumferential groove is β1, and the value range of β1 is:

[0030] β1 = arccos[(τ + h + g) / r1] ∈ [30°, 60°]

[0031] Among them, τ is the size of the rotor tip clearance. Therefore, the value range of r1 is:

[0032] (τ + h + g) / cos30° ≤ r1 ≤ (τ + h + g) / cos60°

[0033] 5) According to the arc determined in step 3), the connection line between the left - hand endpoint A of the arc and the center O1 intersects the connection line of the upper bound of the circumferential groove at D, and the included angle between AD and the radial direction is θ, θ ∈ [0°, 30°].

[0034] 6) According to the connection line AD determined in step 4), with the mid - point of AD as the center O2 and AD as the diameter, make an arc that intersects the upper bound of the circumferential groove at point C. According to the included angle γ between the casing wall and the axial direction, the radius r2 of the arc is:

[0035] r2 = (r1 - DO1) / 2 = [r1 - (τ + h + g) / cos(θ + γ)] / 2

[0036] 7) According to the arc determined in step 5) It can be known that the included angle between the tangent line at point C and the casing wall is:

[0037] β2 = θ + γ

[0038] 8) According to the two smoothly connected arcs determined by the above design steps and ​The profile shape of the axial slot is formed. For the axial slot type casing treatment formed with this profile, the number of treatment slots is generally taken as 3 - 5 times the number of rotor blades, and the circumferential opening ratio Φ is generally taken as 30% - 70%. The opening ratio Φ refers to the ratio of the opening area of the treatment slot on the casing to the area of the casing within the axial range where the treatment slot is located.

[0039] 9) Based on the axial slot profile, circumferential slots are designed upstream and downstream of the leading edge of the blade tip. The profile shape of the circumferential slot in the meridional plane is a parallelogram.

[0040] 10) The front end of the upstream circumferential slot coincides with the front end position of the axial slot profile, and the angle between the front end face of the slot and the casing wall is α1 = β1; the rear end of the downstream circumferential slot coincides with the rear end position of the axial slot profile, and the angle between the rear end face of the slot and the casing wall is α2 = β2; the depth of the two circumferential slots is g, and the width is d, d ∈ [4%c x,tip , 8%c x,ti .

[0041] Embodiment

[0042] Taking the first-stage rotor of a certain gas turbine high-pressure compressor as an example to illustrate the specific implementation manner of the present invention.

[0043] Some design parameters of this compressor rotor are shown in Table 1.

[0044] Table 1 Some design parameters of the first-stage rotor of a certain gas turbine high-pressure compressor.

[0045]

[0046] The present invention is further described in detail according to the content of the present invention:

[0047] 1) In the meridional plane view of the rotor flow field, taking the leading edge point at 95% blade height as the center O1, then h = 5%H = 6.75 mm;

[0048] 2) Select the circumferential slot height g to be 3 mm, and select β1 to be 45°, then r1 = (τ + h + g) / cosβ1 = 14.78 mm. Make an arc with O1 as the center and a radius of r1, which intersects the casing wall at point B;

[0049] 3) Select θ to be 15°, then determine the position of the left endpoint A of the arc. The line connecting the endpoint A and the center O1 intersects at D;

[0050] 4) Taking the midpoint of AD as the center O2 and AD as the diameter, make an arc that intersects the casing wall at point C. The radius r2 of the arc is:

[0051] r2 = (r1 - DO1) / 2 = [r1 - (τ + h) / cos(θ + γ)] / 2 = 3.33 mm

[0052] 5) According to the arc determined in step 4) It can be known that the included angle between the tangent line at point C and the casing wall surface is:[[]]

[0053] β2 = θ + γ = 23.6°

[0054] 6) The two smoothly connected arcs determined according to the above design steps and form the cross-sectional shape of the axial slot. For the axial slot type casing treatment formed by this profile, the included angle δ with the radial direction is taken as 30°, the number of treatment slots is taken as 129, and the circumferential opening ratio Φ is taken as 50%.

[0055] 7) The front end of the upstream circumferential slot is in the same position as the front end of the axial slot cross-sectional profile, and the included angle between the front end face of the slot and the casing wall surface is α1 = β1; the rear end of the downstream circumferential slot is in the same position as the rear end of the axial slot cross-sectional profile, and the included angle between the rear end face of the slot and the casing wall surface is α2 = β2; the depth g of the two circumferential slots is 3 mm, and the width d is 3 mm.

[0056] For the circumferential slot type casing treatment with jet strengthening according to the above structure, by using two smoothly connected arcs, the tip fluid can smoothly flow into the treatment slot from the rear of the treatment slot and be injected into the upstream of the leading edge from the front of the treatment slot, achieving the purpose of reducing flow loss and improving the margin broadening ability at the same time.

[0057] Although the present invention has been described in detail above with general descriptions and specific embodiments, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A combined casing treatment structure for an axial flow compressor, characterized in that, It includes a compressor moving blade and a corresponding casing treatment structure. Two circumferential grooves are opened on the casing wall surface corresponding to the top of the compressor moving blade, which are respectively located upstream and downstream of the leading edge of the blade tip. Above the circumferential grooves, a number of arc-shaped treatment seams that are symmetric about the circumferential center are superimposed. The front end of the circumferential groove upstream of the leading edge is overlapped with the front end of the treatment seam and smoothly transitioned. The rear end of the circumferential groove downstream of the leading edge is overlapped with the rear end of the treatment seam and smoothly transitioned; The widths of the upstream and downstream circumferential grooves are both 5%-10% of the axial chord length. The rear end of the upstream circumferential groove is about 4%-8% of the axial chord length away from the leading edge of the rotor blade tip. The front end of the downstream circumferential groove is 4%-8% of the axial chord length away from the leading edge of the rotor blade tip. The depths g of the two circumferential grooves are both 4%-8% of the axial chord length. The width d of the circumferential groove is 4%-8% of the axial chord length. The included angle between the downstream circumferential groove and the upper end wall of the rotor in the meridional plane is α1, and the included angle between the upstream circumferential groove and the upper end wall is α2; For the axial slot above the circumferential slot, the profile of the axial slot is designed in the meridian plane. Taking the leading edge point within the range of 90% - 98% of the blade height as the center O1, an arc with a radius of r1 is drawn. The left endpoint of this arc is denoted as A, and the intersection point of the parallel line g above the casing on the right side with the upper boundary of the circumferential slot is denoted as B, and it is denoted as the arc Arc The included angle with the upper bound of the circumferential groove is β1, and β1 is equal to α1, with a value range of 30° to 60°. Correspondingly, the value range of the radius r1 of this arc is: (τ + h) / cos30° ≤ r1 ≤ (τ + h) / cos60°, where τ is the size of the rotor tip clearance and h is the distance from the center O1 to the tip; Arc The connection line between the left endpoint A of and the center O1 intersects the upper bound of the circumferential groove at point D. The included angle between AD and the radial direction is θ, and the value range of θ is 0° to 30°.

2. The combined casing treatment structure for an axial flow compressor according to claim 1, wherein Taking the midpoint of the connecting line AD as the center O2 and AD as the diameter, draw an arc that intersects the upper bound of the circumferential groove at point C, denoted as the arc 3. The combined casing treatment structure for an axial compressor according to claim 2, characterized in that, Circular arc Together with the circular arc They jointly form the contour of the axial slot in the meridian plane. For the axial slot type casing treatment formed by this contour, the included angle with the radial direction is δ, and the value range of δ is 30° to 60°. The number of treatment slots is taken as 3 - 5 times the number of rotor blades, and the circumferential opening ratio Φ is taken as 30% - 70%. The opening ratio Φ refers to the ratio of the opening area of the treatment slot on the casing to the area of the casing within the axial range where the treatment slot is located, that is, Φ = W / (W + L), where W is the width of the treatment slot and L is the interval distance between the slots.

4. The combined casing treatment structure for an axial compressor according to claim 3, wherein, The radius r2 of the contour of the axial seam in the meridional plane is r2 = (r1 - DO1) / 2 = [r1 - (τ + h) / cos(θ + γ)] / 2, where γ is the included angle between the casing wall surface and the axial direction.

5. The combined casing treatment structure for an axial flow compressor according to claim 4, characterized in that, Arc The included angle β2 between the tangent line at point C of and the upper bound of the circumferential groove is equal to the value of α2, and β2 = θ + γ.

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