A method for diffuser passage design for a double outlet centrifugal compressor

Abstract

The application discloses a diffuser passage design method for a double-outlet centrifugal compressor, wherein the diffuser passage is composed of a diffuser and two center-symmetrical rectification sections, and a gas flow collecting section is arranged between the diffuser and the rectification sections; gas flow from the centrifugal compressor flows into the diffuser from the diffuser inlet, is deflected by the diffuser blades, and then enters the two center-symmetrical rectification sections at the interface; and finally, the gas enters two single-pipe combustion chambers from two outlets respectively. The application reduces the flow process of the gas in the diffuser passage, is beneficial to loss reduction, and thus improves the efficiency; on the other hand, the diffuser passage of the double-outlet centrifugal compressor is in a center-symmetrical layout, and the two single-pipe combustion chambers connected are also in a center-symmetrical layout, so that the volume of a single combustion chamber is reduced, the overall size of the gas turbine is controlled, and the application range of the gas turbine is wider.

Description

Technical Field

[0001] This invention relates to the field of diffuser channel design, and in particular to a diffuser channel design method for a dual-outlet centrifugal compressor. Background Technology

[0002] Centrifugal compressors are widely used in micro gas turbines due to their compact structure and high single-stage pressure ratio. Furthermore, micro gas turbines often employ a single-tube combustor to ensure combustion efficiency. To further decelerate and pressurize the airflow at the compressor outlet, a diffuser is needed between the compressor and the combustor.

[0003] Most existing diffusers are single-outlet designs, meaning the diffuser is connected downstream to a single-tube combustion chamber. This results in a longer gas flow path and greater flow losses, affecting the efficiency of the gas turbine. Furthermore, the combustion chamber requires a larger volume, impacting the overall size and layout of the gas turbine and limiting the application scenarios for micro gas turbines. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a diffuser channel design method for a dual-outlet centrifugal compressor, which can shorten the gas flow path in the diffuser channel, reduce flow losses, and limit the overall size of the gas turbine, thus having a wide range of applications.

[0005] Therefore, the technical solution of the present invention is: a diffuser channel design method for a dual-outlet centrifugal compressor, wherein the diffuser channel consists of a diffuser and two centrally symmetrical rectification sections, and an airflow collection section is provided between the diffuser and the rectification sections;

[0006] 1) Diffuser flow channel design:

[0007] The diffuser has a diffuser inlet in the middle with a radius of r2; the diffuser has several blades inside, with the leading edge of the blades on a circle with a radius of r3 and the trailing edge of the blades on a circle with a radius of r4; the interface between the diffuser and the rectifier section is circular with a corresponding radius of r5; the axial thickness of the diffuser is b.

[0008] The angle between the absolute velocity direction of the airflow at the leading edge of the blade and the radial direction is α3, and the angle between the tangent at the trailing edge of the blade and the radial direction is specified as α4, and 0 < α4 < α3 < 90° is satisfied.

[0009] The distance from the origin is r C The angle α between the tangent at point C on the mid-arc line and the radial direction. C ,but:

[0010]

[0011] The coordinates of point C (X) C ,YC ):

[0012]

[0013]

[0014] Where R is the radius of the arc corresponding to the mid-arc in polar coordinates:

[0015]

[0016] The dimensionless relative offset of the diffuser blade profile is but:

[0017] Two-dimensional coordinates of the suction surface airfoil at point C (X SS ,Y SS ):

[0018]

[0019]

[0020] Two-dimensional coordinates of the pressure surface airfoil at point C (X PS ,Y PS ):

[0021]

[0022]

[0023] 2) Airflow collection section design:

[0024] The airflow collection section is composed of multiple segments, and its outer contour can be divided into five segments: V1V2, V2V3, V3V4, V4V5, and the downstream segment of V5. Segment V1V2 is a straight line with an angle of α5 to the radial direction. Segment V2V3 has a symmetrical radial cross-section and a semi-circular outer contour. A tangent spline curve is set at each end of the semi-circular arc, and the other end of the spline curve is tangent to the diffuser surface. The distance between any point S3 on the semi-circular arc and the origin O is r5 + Φ. θ ,

[0025] in:

[0026]

[0027] Based on the principles of gas dynamics, we can approximate α5 = α4; ε is a scaling factor, ranging from 1 to 1.5.

[0028] Sections V3 and V4 are transition sections, and the downstream section of V5 is the rectification section.

[0029] Based on the above scheme and as a preferred scheme: the angle between the absolute velocity direction of the airflow at the diffuser inlet and the radial direction is α2, and the annular region from radius r2 to radius r3 is the bladeless diffuser section. According to the principle of gas dynamics, the angle between the absolute velocity direction of the airflow at the leading edge of the blade and the radial direction is approximately equal to α2, that is, approximately α3=α2.

[0030] Based on the above scheme and as a preferred embodiment of the above scheme: the number of diffuser blades is within the range of -5 to +5 of the number of compressor blades, and the greatest common divisor of the diffuser blades and the number of compressor blades is 1; after determining the position of one blade, the positions of the other blades can be obtained by rotating the array.

[0031] Based on the above scheme and as a preferred scheme: the starting point V1 of the airflow collection section is located at the interface between the diffuser and the rectifier section, and the angle between the line connecting V1 and the origin O and the X-axis is θ1, where θ1 is 5° to 15°. The V1V2 segment corresponds to a plane in three-dimensional space.

[0032] Based on the above scheme and as a preferred embodiment of the above scheme: the angle between the line connecting V3 and the origin O and the X-axis is θ3, where θ3 is 140° to 160°; V3, V4, and V5 are on the same straight line, which is perpendicular to OV3.

[0033] Based on the above scheme and as a preferred embodiment of the above scheme: a point V6 is provided at the inner contour of the V4V5 segment, the point V6 is on the same straight line as the starting point V1 of the airflow collection segment on the other side, and is parallel to V3V5; the radial cross section of the downstream segment of V5 is circular, and the diameter of the circle is the distance between V3V5 and V1V6.

[0034] Based on the above scheme and as a preferred embodiment of the above scheme: the radial cross sections of the V3V4 and V4V5 segments can be obtained by sweeping.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: the airflow from the compressor is divided into two streams, which, after deceleration and pressurization, enter two centrally symmetrically arranged single-tube combustion chambers respectively. Compared with the traditional single-outlet diffuser channel, the present invention reduces the flow path of the gas in the diffuser channel, which is beneficial to reducing losses and thus improving efficiency. On the other hand, the diffuser channel of the dual-outlet centrifugal compressor is centrally symmetrically arranged, and the two connected single-tube combustion chambers are also centrally symmetrically arranged, thereby reducing the volume of a single combustion chamber, controlling the overall size of the gas turbine, and making the application range of the gas turbine wider. Attached Figure Description

[0036] The following detailed description, in conjunction with the accompanying drawings and embodiments of the present invention, will provide further information.

[0037] Figure 1 This is a schematic diagram of the structure of the present invention;

[0038] Figure 2 This is a schematic diagram of the diffuser flow channel design of the present invention;

[0039] Figure 3 This is a schematic diagram of the airflow collection section design of the present invention;

[0040] Figure 4 This is a schematic diagram of the radial cross-section of each part of the airflow collection section of the present invention.

[0041] The following are marked in the figure: diffuser inlet 1, blade 2, blade leading edge 21, blade trailing edge 22, mid-curve 23, suction surface 24, pressure surface 25, airflow collection section 3, and interface between diffuser and rectifier section 4. Detailed Implementation

[0042] In the description of this invention, it should be noted that the directional terms such as "center", "horizontal (X)", "longitudinal (Y)", "vertical (Z)", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific protection scope of this invention.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features. Thus, the use of "first" and "second" to define a feature may explicitly or implicitly include one or more of that feature. In the description of this invention, "several" or "a number" means two or more, unless otherwise explicitly specified.

[0044] See the attached diagram. The diffuser channel design method described in this embodiment comprises a diffuser and a rectifying section. The diffuser has a diffuser inlet 1 in the middle, which connects to a centrifugal compressor. The diffuser has several evenly arranged blades 2, and two centrally symmetrical rectifying sections are located on the outer side of the diffuser. An airflow collection section 3 is located between the diffuser and the rectifying sections. The airflow from the centrifugal compressor flows into the diffuser through the diffuser inlet, and after being deflected by the diffuser blades, enters the two centrally symmetrical rectifying sections at the interface. After passing through the rectifying sections, the gas finally enters two single-tube combustion chambers from the outlets of the two rectifying sections, respectively.

[0045] 1) Diffuser flow channel design methods, such as Figure 2 As shown:

[0046] In the XY plane, the diffuser inlet 1 is circular with a radius of r2; the blade leading edge 21 is on a circle with a radius of r3, and the blade trailing edge 22 is on a circle with a radius of r4; the interface between the diffuser and the rectifier section is circular with a corresponding radius of r5; at the same time, the axial thickness of the diffuser is b.

[0047] The angle between the absolute velocity direction of the airflow at the diffuser inlet and the radial direction is α2. Since the annular region from radius r2 to radius r3 is a bladeless diffuser section, according to the principles of gas dynamics, the angle α3 between the absolute velocity direction of the airflow at the leading edge of the blade and the radial direction is approximately equal to α2, that is, approximately α3=α2. The angle α4 between the tangent at the trailing edge of the blade and the radial direction is specified, satisfying 0<α4<α3<90°.

[0048] The blade has a central arc line 23 in the middle, and any point C on the central arc line is r away from the origin. C The angle α between the tangent at point C and the radial direction. C ,but:

[0049]

[0050] The coordinates of point C (X) C ,Y C ):

[0051]

[0052]

[0053] Where R is the radius of the arc corresponding to the mid-arc in polar coordinates:

[0054]

[0055] The dimensionless relative offset of the diffuser blade profile is but:

[0056] The suction surface at point C has a 24-leaf-shaped two-dimensional coordinate (X) SS ,Y SS ):

[0057]

[0058]

[0059] The pressure surface at point C has a 25-degree airfoil two-dimensional coordinate (X) PS ,Y PS ):

[0060]

[0061]

[0062] The number of diffuser blades is generally taken to be within the range of -5 to +5 of the number of compressor blades, and it must be ensured that the greatest common divisor of the diffuser and compressor blades is 1. After determining the position of one blade, the positions of the other blades can be obtained by rotating the array.

[0063] The above determines the geometry of the diffuser channel.

[0064] 2) Airflow collection section design methods, such as Figure 3 , Figure 4 As shown:

[0065] The airflow collection section is composed of multiple segments. Based on its outer contour, it is divided into five segments: V1V2, V2V3, V3V4, V4V5, and the downstream segment of V5. The angle θ between the line connecting any point on the XY plane to the origin O and the X-axis is defined as follows.

[0066] The starting point V1 of the airflow collection section is located at the interface 4 between the diffuser and the rectifier section. The angle between the line connecting V1 and the origin O and the X-axis is θ1, where θ1 is 5° to 15°. V1V2 is a straight line, and the angle between it and the radial direction is α5. V1V2 corresponds to a plane in three-dimensional space.

[0067] The cross-section of segment V2V3 along the radial direction is shown in AA. S3 is the outer contour point (located on V2V3), and S2S3S4 is a semicircular arc. S1S2 is a spline curve that is tangent to S2S3 and the diffuser surface; S4S5 is a spline curve that is tangent to S3S4 and the diffuser surface.

[0068] The distance between S3 and the origin O is r5+Φ θ .

[0069] in:

[0070]

[0071] b, r5, α5 and Figure 2 The definitions are consistent; according to the principles of gas dynamics, we can approximate α5 = α4; ε is a scaling factor, which is generally taken as 1 to 1.5.

[0072] V3V4 and V4V5 are transition sections, and the downstream section of V5 is the rectification section. In the XY plane, the line connecting V3 and the origin O makes an angle θ3 with the X-axis, where θ3 is between 140° and 160°. Points V3, V4, and V5 are collinear, and this line is perpendicular to OV3. Point V6 is located on the inner contour corresponding to the position of V4V5. Point V6 is collinear with the starting point V1 of the airflow collection section on the other side and parallel to V3V5. The radial section DD of the downstream section of V5 is circular, and the diameter of this circle is the distance between sections V3V5 and V1V6.

[0073] Based on the established geometry, the cross sections BB and CC corresponding to the transition segments of V3V4 and V4V5 can be obtained by sweeping.

[0074] The geometry of the airflow collection section has been determined in the above.

[0075] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for designing a diffuser channel for a dual-outlet centrifugal compressor, characterized in that: The diffuser channel consists of a diffuser and two centrally symmetrical straightening sections, with an airflow collection section between the diffuser and the straightening sections. 1) Diffuser flow channel design: The diffuser has a diffuser inlet in the middle with a radius of r2; the diffuser has several blades inside, with the leading edge of the blades on a circle with a radius of r3 and the trailing edge of the blades on a circle with a radius of r4; the interface between the diffuser and the rectifier section is circular with a corresponding radius of r5; the axial thickness of the diffuser is b. The angle between the absolute velocity direction of the airflow at the leading edge of the blade and the radial direction is α3, and the angle between the tangent at the trailing edge of the blade and the radial direction is specified as α4, and 0 < α4 < α3 < 90° is satisfied. The distance from the origin is r C The angle α between the tangent at point C on the mid-arc line and the radial direction. C ,but: The coordinates of point C (X) C ,Y C ): Where R is the radius of the arc corresponding to the mid-arc in polar coordinates: The dimensionless relative offset of the diffuser blade profile is but: Two-dimensional coordinates of the suction surface airfoil at point C (X SS ,Y SS ): Two-dimensional coordinates of the pressure surface airfoil at point C (X PS ,Y PS ): 2) Airflow collection section design: The airflow collection section is composed of multiple segments, and its outer contour can be divided into five segments: V1V2, V2V3, V3V4, V4V5, and the downstream segment of V5. Segment V1V2 is a straight line with an angle of α5 to the radial direction. Segment V2V3 has a symmetrical radial cross-section and a semi-circular outer contour. A tangent spline curve is set at each end of the semi-circular arc, and the other end of the spline curve is tangent to the diffuser surface. The distance between any point S3 on the semi-circular arc and the origin O is r5 + Φ. θ , in: Based on the principles of gas dynamics, we can approximate α5 = α4; ε is a scaling factor, ranging from 1 to 1.

5. Sections V3 and V4 are transition sections, and the downstream section of V5 is the rectification section.

2. The diffuser channel design method for a dual-outlet centrifugal compressor as described in claim 1, characterized in that: The angle between the absolute velocity direction of the airflow at the diffuser inlet and the radial direction is α2. The annular region from radius r2 to radius r3 is the bladeless diffuser section. According to the principle of gas dynamics, the angle between the absolute velocity direction of the airflow at the leading edge of the blade and the radial direction is approximately equal to α2, that is, approximately α3=α2.

3. The diffuser channel design method for a dual-outlet centrifugal compressor as described in claim 1, characterized in that: The number of diffuser blades is within the range of -5 to +5 of the number of compressor blades, and the greatest common divisor of the diffuser blades and the number of compressor blades is 1. Once the position of one blade is determined, the positions of the other blades can be obtained by rotating the array.

4. The diffuser channel design method for a dual-outlet centrifugal compressor as described in claim 1, characterized in that: The starting point V1 of the airflow collection section is located at the interface between the diffuser and the rectifier section. The angle between the line connecting V1 and the origin O and the X-axis is θ1, where θ1 is 5° to 15°. The V1V2 section corresponds to a plane in three-dimensional space.

5. The diffuser channel design method for a dual-outlet centrifugal compressor as described in claim 1, characterized in that: The angle between the line connecting V3 and the origin O and the X-axis is θ3, where θ3 is 140° to 160°; V3, V4, and V5 are on the same straight line, which is perpendicular to OV3.

6. The diffuser channel design method for a dual-outlet centrifugal compressor as described in claim 1, characterized in that: A point V6 is provided at the inner contour of the V4V5 segment. Point V6 is on the same straight line as the starting point V1 of the airflow collection segment on the other side and is parallel to V3V5. The radial section of the downstream segment of V5 is circular, and the diameter of the circle is the distance between V3V5 and V1V6.

7. The diffuser channel design method for a dual-outlet centrifugal compressor as described in claim 1, characterized in that: The radial cross sections of segments V3V4 and V4V5 can be obtained by sweeping.

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