Design and forming method of streamline tunnel type rotating fluid machinery flow channel

Abstract

The present invention discloses a streamline tunnel type rotating fluid machinery flow channel design and forming method and includes the following steps: S1: obtain the relevant constraint parameters obtained by one-dimensional design; S2: obtain the center line expansion projection curve and construct it as a cubic Hermite curve; S3: after obtaining the center line expansion projection curve, restore the expansion plane to a cylinder, and obtain the equation of the cylindrical projection curve; S4: if the meridian form is known, it is easy to obtain the equation of the torus where the center line is located; S5: combine the above-mentioned cylindrical projection curve and the torus equation to obtain the equation of the actual flow channel center line; S6: according to the flow characteristics and speed conditions of the rotating machinery, the flow channel inlet and outlet areas are obtained, thereby forming a complete flow channel. The present invention can be easily expanded to the streamline design of more fluid machinery through the combined equation method, and is suitable for media such as gas, liquid, solid powder and multiphase mixed fluid, forming a design system from streamline to flow channel, low dimension to high dimension, and can make a more reasonable prediction of mechanical performance.

Description

Technical Field

[0001] The invention relates to the field of rotary fluid machinery, and in particular to a flow channel design and forming method of a streamline tunnel type rotary fluid machinery. Background Art

[0002] Rotation is the most common movement in the world, and rotary machinery is the most widely used machinery in the world. Rotary impeller machinery, such as gas turbines, steam turbines, turbochargers, blowers, fans, rotary compressors, rotor pumps, etc., are the most important fluid machinery and power transmission in today's society. Its media involve various media forms such as gas, liquid, solid powder, and even multiphase mixed fluids. For any kind of machinery and medium, whether the internal streamline can complete the required turning and whether the streamline is smooth and smooth are the decisive factors of mechanics and mechanical performance.

[0003] The current mainstream blade impeller machinery has mature theoretical research and is widely used. However, compared with traditional blade machinery, the new streamlined tunnel type rotary machinery has the advantages of low material strength requirements, large streamline design optimization space, small leakage loss, wide range of application materials, and adaptability to higher speeds. It can improve the power density of power machinery, reduce size, reduce weight, and further improve the efficiency of rotary machinery. U.S. Patents US4029431, US4278397 and US4293278 disclose the structure of axial flow streamlined tunnel type rotary fluid machinery, and international patents WO2004 / 022921A1 and WO2011 / 042863A2 disclose the structure of radial flow streamlined tunnel type rotary fluid machinery, but neither mentions the content about flow channel forming;

[0004] At present, there are few and in-depth studies on streamline tunnel rotating machinery, especially the lack of research on its design and forming methods. With the advancement of science and technology, additive manufacturing technology has matured, and the application of advanced manufacturing technologies such as 3D printing and injection molding can mass-produce this new type of machinery;

[0005] The typical characteristics of streamline tunnel-type rotating machinery are that the number of flow channels is as many as dozens and the flow area of ​​a single flow channel is small. Therefore, it has a stronger restraint on the fluid and determines the flow state of the fluid in the flow channel to a large extent, that is, there is more room for design optimization; therefore, the design of the flow channel centerline is particularly important. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] The purpose of the present invention is to propose a flow channel design and forming method for a streamline tunnel type rotary fluid machinery. The center line of the flow channel meets the constraints of the inlet and outlet parameters. The center line is used as the forming reference line of the strong constraint flow channel, so that the fluid in the flow channel can complete the required turning. Therefore, the above center line can also be regarded as the average streamline of the fluid in the flow channel, and the streamline curvature should change smoothly to reduce the flow loss.

[0008] The present invention provides a streamline tunnel type rotating fluid machinery flow channel design and forming method, the design and forming method comprising the following steps:

[0009] S1: Obtain relevant constraint parameters obtained from one-dimensional design;

[0010] S2: Select the cylindrical surface where the proximal end point of the center line is located, project the center line onto the cylindrical surface, and then unfold the cylindrical surface into a plane to obtain the center line unfolded projection curve. Using the projection point positions and derivative data of the proximal end point and the distal end point of the center line, the center line unfolded projection curve can be constructed as a cubic Hermite curve.

[0011] S3: After obtaining the centerline unfolded projection curve, restore the unfolded plane in step S2 to a cylinder, and set the azimuth and height of the projection point of the centerline far end point to zero, and obtain the equation of the cylinder projection curve;

[0012] S4: The surface formed by the meridian rotating around the rotor axis is the annular surface where the center line is located. If the form of the meridian is known, the equation of the annular surface where the center line is located can be easily obtained;

[0013] S5: Projecting the cylindrical projection curve in step S3 onto the torus surface in step S4, the projection is the actual center line, and the equation of the actual center line can be obtained by combining the cylindrical projection curve and the torus surface equation;

[0014] S6: The normal section of the flow channel perpendicular to the center line is a circle or an ellipse. The inlet and outlet areas of the flow channel are obtained according to the flow characteristics and speed conditions of the rotating machinery. The cross-sectional area changes uniformly along the center line, thus forming a complete flow channel.

[0015] Preferably, the constraint parameters include the radius of the two end points of the centerline distal end point and the centerline proximal end point, the structural angles at the two end points, the axial (z-axis direction) distance between the two end points, and the flow channel envelope angle.

[0016] Preferably, the proximal end point of the center line is an end point that is closer to the axis of the rotating machine, and the angle between the extension direction of the curve at the proximal end point of the center line and the tangent direction of the circle is set as a relative airflow angle.

[0017] Preferably, for radial flow machinery, the streamline direction at the distal end of the centerline is generally radial. At this time, the derivative at the projection point of the distal end may not be constrained, and the derivative at the projection point of the distal end of the centerline is temporarily set to an undetermined coefficient to preliminarily construct the Hermite curve described in step S2.

[0018] Preferably, the meridian is the center line in the meridian plane. For a streamlined tunnel type centripetal turbine or a centrifugal compressor, the meridian can be constructed as an elliptical arc; for a streamlined tunnel type mixed flow turbine or a mixed flow compressor, the meridian can be constructed as a parabola; for a streamlined tunnel type axial flow turbine or an axial flow compressor, the meridian can be constructed as an axial straight line.

[0019] Preferably, when the normal section of the flow channel perpendicular to each point on the center line is an ellipse, the projection of the major axis of the ellipse on the xy plane is perpendicular to the perpendicular line from the center point of the ellipse to the z axis, and the ratio of the major axis to the minor axis remains unchanged.

[0020] Preferably, the unknown coefficients can be obtained by making the second-order derivative at the projection point near the center line endpoint zero, thereby making the curvature change of the center line expansion projection curve near the endpoint smoother and avoiding the inflection point of the cubic function to appear inside the flow channel.

[0021] Beneficial effects of the present invention

[0022] The present invention flexibly uses the cylindrical coordinate system and the cylindrical projection method to combine the cylindrical projection curve and the torus where the center line is located into the actual center line equation. The cylindrical projection curve is a deformation of the cubic Hermite curve, and its curvature changes smoothly. The Hermite curve contains node derivative information, so the construction angle at the near end point of the flow channel can be accurately controlled. The meridian adopts the form of elliptical arc, circular arc, parabola, etc., which can ensure the smooth turning of the airflow between the radial and axial directions. Therefore, the center line equation constructed by the present invention can realize the required turning of the fluid, and the curvature of the curve transitions smoothly, which can ensure a smaller flow loss in the flow channel. The combined equation method is easy to expand to the streamline design of more fluid machinery, and is suitable for media such as gas, liquid, solid powder and multiphase mixed fluid, forming a design system from streamline to flow channel, low dimension to high dimension, so that a more reasonable prediction of mechanical performance can be made in the early stage of design. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 are the constraint parameters of radial flow rotating machinery obtained by one-dimensional design.

[0024] Figure 2 Unfold the projection curve for the centerline of a radial flow rotating machine.

[0025] Figure 3 It is the actual center line of the radial flow rotating machinery and the annular surface on which it is located.

[0026] Figure 4It is a schematic diagram of the complete flow channel and the normal cross section of the flow channel.

[0027] Figure 5 Expand the projected curve coordinate data for the centerline.

[0028] Explanation of the accompanying reference numerals: 1. Meridian; 2. Centerline unfolded projection curve; 3. Projection point of the far end point of the centerline; 4. Projection point of the near end point of the centerline; 5. Actual centerline; 6. Annular surface where the centerline is located; 7. Far end point of the centerline; 8. Near end point of the centerline; 9. Normal section of the flow channel; 10. Complete flow channel. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example

[0031] like Figure 1-Figure 5 As shown, the present invention provides a streamline tunnel type rotating fluid machinery flow channel design and forming method, the design and forming method comprises the following steps:

[0032] S1: Constraint parameters obtained from the one-dimensional design include: the radius of the two end points of the centerline distal end 7 and the centerline proximal end 8 of the flow channel, and the construction angles at the two end points of the centerline distal end 7 and the centerline proximal end 8, and the assumed flow channel envelope angle, the axial (z-axis direction) distance between the two end points of the centerline distal end 7 and the centerline proximal end 8;

[0033] S2: Consider the centerline proximal end point 8 which is closer to the axis. For a single-stage centrifugal turbine or centrifugal compressor, the absolute velocity at the centerline proximal end point 8 is generally close to the axial direction. Therefore, the relative velocity must be at a certain angle to the circumferential tangent, that is, the relative airflow angle. The flow channel also needs to have a corresponding structural angle. In order to facilitate constraining the construction angle at the proximal end point 8 of the center line, the cylindrical surface where the proximal end point 8 of the center line is located is selected, and the center line is projected onto the cylindrical surface, and then the cylindrical surface is unfolded into a plane, and the center line unfolded projection curve 2 can be obtained. The center line unfolded projection curve 2 cannot directly reflect the construction angle at the other end point (i.e., the distal end point 7 of the center line), but the construction angle at the distal end point 7 of the center line can also be mapped to the center line unfolded projection curve 2 through corresponding transformation. It is assumed that the construction angles at both end points are equal to the relative airflow angle, that is, the tangent directions at the two end points of the distal end point 7 of the center line and the proximal end point 8 of the center line are known. By using the projection point positions and derivative data of the two end points of the distal end point 7 of the center line and the proximal end point 8 of the center line, the center line unfolded projection curve 2 can be constructed as a cubic Hermite curve, that is, a cubic function determined by the two end point positions and tangent directions of the distal end point 7 of the center line and the proximal end point 8 of the center line;

[0034] S3: For axial flow rotating machinery, it is a special case, that is, the distances between the centerline distal end 7 and the centerline proximal end 8 and the axis are equal;

[0035] For radial flow (centrifugal, centripetal) machinery, the streamline direction at the far end point 7 of the center line is generally radial. At this time, the derivative at the projection point 3 of the far end point of the center line can be unconstrained. Therefore, there is an undetermined coefficient in the Hermite curve constructed in step S2. The second-order derivative at the projection point 4 of the near end point of the center line can be set to zero, thereby making the curvature change of the near end point of the above-mentioned center line expansion projection curve 2 smoother and avoiding the inflection point of the cubic function appearing inside the flow channel. At this time, the above-mentioned undetermined coefficient can be determined

[0036] S4: After obtaining the centerline unfolded projection curve 2, the unfolded plane in step S2 is restored to a cylinder, and the azimuth and height of the centerline far end projection point 3 are set to zero, and the equation of the cylinder projection curve can be obtained;

[0037] S5: The center line in the meridian plane is called meridian 1. The curved surface formed by the meridian 1 rotating around the rotor axis is the annular curved surface 6 where the center line is located. Meridian 1 can generally be constructed in various forms such as elliptical arcs, circular arcs, parabolas, etc. If the form of meridian 1 is known, the equation of the annular curved surface 6 where the center line is located can be easily obtained;

[0038] S6: Projecting the cylindrical projection curve in step S4 onto the torus surface in step S5, the projection is the actual center line 5, and the equation of the actual center line 5 can be obtained by combining the cylindrical projection curve and the torus surface equation;

[0039] S7: The normal section 9 of the flow channel perpendicular to the center line is a circle or an ellipse. When it is an ellipse, the projection of its major axis on the xy plane is perpendicular to the radius line of the point, and the ratio of the major axis to the minor axis remains unchanged. The inlet and outlet areas of the flow channel are obtained according to the flow characteristics and speed conditions of the rotating machinery. The cross-sectional area changes uniformly along the center line, thereby forming a complete flow channel 10;

[0040] like Figure 1 As shown, Figure 1 The upper part is the meridian view of the radial rotating machinery, and the lower part is the top view. The constraint parameters obtained from the one-dimensional design are shown in Figure 1 , the meridian 1 is the center line in the meridian plane, then the radius of the far end point 7 of the center line of the flow channel is R1, the radius of the near end point 8 of the center line is R2, and assuming the flow channel envelope angle γ, the axial (z-axis direction) distance between the two end points of the center line is H;

[0041] Project the center line onto a cylinder with a radius of R2, and then unfold the cylinder into a plane to form a center line unfolded projection curve 2, such as Figure 2 As shown, β is the relative airflow angle of the near end point, which can be assumed to be equal to the structural angle at the near end point, and the projection point 3 of the far end point of the center line is set as the origin, and the z-axis direction remains unchanged, then the coordinate data of the projection points 3 and 4 of the two end points of the center line can be obtained, see Figure 5 ;

[0042] Using two-point data, the centerline expansion projection curve 2 can be constructed as a cubic Hermite curve:

[0043]

[0044] Where λ is the undetermined coefficient related to the derivative at the projection point 3 of the far end point of the center line. The second-order derivative at the projection point 4 of the near end point of the center line is set to zero, which can make the curvature change at the projection point 4 of the near end point smoother and avoid the inflection point of the cubic function appearing inside the flow channel. At this time, the undetermined coefficient λ can be determined:

[0045]

[0046] Substituting λ into the above Hermite curve, we get:

[0047]

[0048] Restore the above unfolded plane to a cylinder, and set the azimuth and height of the projection point 3 of the center line far end point to zero, and you can get the equation of the cylindrical projection curve in the cylindrical coordinate system:

[0049]

[0050] A circular arc or elliptical arc meridian 1 can be used in radial flow rotating machinery. The curved surface formed by the meridian 1 rotating around the rotor axis (z axis) for one circle is the annular curved surface 6 where the center line is located. The equation of the curved surface in the cylindrical coordinate system is:

[0051]

[0052] Project the cylindrical projection curve onto the torus surface 6 where the center line is located. This projection is the actual center line 5. Combining the cylindrical projection curve and the torus surface equation, its equation in the cylindrical coordinate system can be obtained:

[0053]

[0054] This center line not only satisfies the position constraints of the radius of the two end points, the axial distance between the two end points and the envelope angle, but also satisfies the radial relative velocity at the far end point, the axial absolute velocity at the near end point, and the direction constraints of the relative airflow angle of the two end points. The curvature of the curve transitions smoothly, especially the curvature change is very small at the near end point, which not only ensures a small flow loss in the flow channel, but also ensures that the direction of this strong constraint flow channel at the two end points is consistent with the airflow angle.

[0055] The normal section 9 of the flow channel perpendicular to each point on the center line is a circle or an ellipse. When it is an ellipse, the projection of the major axis of the ellipse on the xy plane is perpendicular to the vertical line from the center point of the ellipse to the z axis, and the ratio of the major axis to the minor axis remains unchanged. The inlet and outlet areas of the flow channel are obtained according to the flow characteristics and speed conditions of the rotating machinery. The cross-sectional area changes uniformly along the actual center line 5, thereby forming a complete flow channel 10. The complete flow channel 10 and the normal section 9 of part of the flow channel are as shown in FIG. Figure 4 shown.

[0056] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A streamline tunnel type rotating fluid machinery flow channel design and forming method, characterized in that: The design and forming method comprises the following steps: S1: Obtain relevant constraint parameters obtained from one-dimensional design; S2: Select the cylindrical surface where the proximal end point of the center line is located, project the center line onto the cylindrical surface, and then unfold the cylindrical surface into a plane to obtain the center line unfolded projection curve. Use the projection point positions and derivative data of the proximal end point and the distal end point of the center line to construct the center line unfolded projection curve into a cubic Hermite curve. S3: After obtaining the centerline unfolded projection curve, restore the unfolded plane in step S2 to a cylinder, and set the azimuth and height of the projection point of the centerline far end point to zero, and obtain the equation of the cylinder projection curve; S4: The surface formed by the meridian rotating around the rotor axis is the annular surface where the center line is located. If the form of the meridian is known, the equation of the annular surface where the center line is located can be easily obtained; S5: Projecting the cylindrical projection curve in step S3 onto the torus surface in step S4, the projection is the actual center line, and combining the cylindrical projection curve and the torus surface equation to obtain the equation of the actual center line; S6: The normal section of the flow channel perpendicular to the center line is a circle or an ellipse. The inlet and outlet areas of the flow channel are obtained according to the flow characteristics and speed conditions of the rotating machinery. The cross-sectional area changes uniformly along the center line, thus forming a complete flow channel.

2. A streamline tunnel type rotating fluid machinery flow channel design and forming method according to claim 1, characterized in that: The constraint parameters include the radius of the two end points of the center line distal end point and the center line proximal end point, the construction angle at the two end points, the axial z-axis distance between the two end points, and the flow channel envelope angle.

3. A streamline tunnel type rotating fluid machinery flow channel design and forming method according to claim 1, characterized in that: The centerline proximal end point is an end point that is closer to the axis of the rotating machine, and the angle between the extension direction of the curve at the centerline proximal end point and the circumferential tangent is set as a relative airflow angle.

4. A streamline tunnel type rotating fluid machinery flow channel design and forming method according to claim 1, characterized in that: For radial flow machinery, the streamline direction at the far end of the centerline is radial. At this time, the derivative at the projection point of the far end of the centerline is not constrained, but the derivative at the projection point of the far end of the centerline is temporarily set to an undetermined coefficient to preliminarily construct the Hermite curve described in step S2.

5. A streamline tunnel type rotating fluid machinery flow channel design and forming method according to claim 1, characterized in that: The meridian is the center line in the meridian plane. For a streamlined tunnel type centripetal turbine or centrifugal compressor, the meridian is constructed as an elliptical arc; for a streamlined tunnel type mixed flow turbine or mixed flow compressor, the meridian is constructed as a parabola; for a streamlined tunnel type axial flow turbine or axial flow compressor, the meridian is constructed as an axial straight line.

6. A streamline tunnel type rotating fluid machinery flow channel design and forming method according to claim 1, characterized in that: When the normal section of the flow channel perpendicular to each point on the center line is an ellipse, the projection of the major axis of the ellipse on the xy plane is perpendicular to the perpendicular line from the center point of the ellipse to the z axis, and the ratio of the major axis to the minor axis remains unchanged.

7. A streamline tunnel type rotating fluid machinery flow channel design and forming method according to claim 4, characterized in that: The undetermined coefficient is obtained by making the second-order derivative at the projection point near the center line endpoint zero, thereby making the curvature change of the center line expansion projection curve near the endpoint smoother and avoiding the inflection point of the cubic function appearing inside the flow channel.

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