Design method of tube diffuser meridian flow channel center line

Abstract

The present application relates to a kind of tubular diffuser meridional flow passage center line design method, including the diffuser meridional flow passage center line is divided into inlet straight section, elbow transition section and outlet axial straight section three parts, then after the total length of diffuser meridional flow passage center line is segmented normalization, the inclination angle distribution of diffuser meridional flow passage center line with the normalization change is defined, and the total length of diffuser meridional flow passage center line is calculated, finally the diffuser meridional flow passage center line coordinate distribution obtained by design is calculated and output, complete the configuration design of diffuser meridional flow passage center line.The present application method can quickly build the tubular diffuser structure satisfying engineering demand, with higher geometric configuration freedom degree, facilitate subsequent development its aerodynamic performance optimization design, significantly expand the engineering applicability and design space of tubular diffuser.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of design of a tubular diffuser of a compressor in an aero-engine. BACKGROUND

[0002] With the rapid development of unmanned aerial vehicles, light aircraft and micro power systems, modern small aero-engines have higher requirements for the compactness and efficiency of compressors. The compactness of the compressor refers to further reducing the radial or axial size of the compressor components based on the original size to achieve compact space structure and weight reduction. How to achieve high pressure ratio and high efficiency in a limited space has become the core challenge of current compressor design. As a key component of the compressor, the geometric structure of the diffuser needs to ensure aerodynamic performance while meeting size requirements. Especially for the diffuser of a centrifugal or mixed flow compressor, how to efficiently guide airflow and achieve deceleration and pressure increase in a limited axial and radial space is the core of diffuser design.

[0003] In small aero-engines, the compressor often adopts a single-stage centrifugal or mixed flow configuration with high pressure ratio. The tubular diffuser has been applied to such single-stage high-pressure-ratio centrifugal / mixed flow compressors due to its flexible design and superior performance. Compared with traditional blade diffusers, tubular diffusers have the potential to further reduce radial size while ensuring the aerodynamic performance of the compressor.

[0004] Publication No. CN119026282A provides a tubular diffuser design method with a dovetail leading edge. Based on the given centerline coordinates of the centrifugal compressor diffuser meridian, the three-coordinate space coordinates are constructed through the spatial angle distribution of the centerline, and the cross-sectional shape along the centerline is determined by combining the area distribution, finally realizing the design and modeling of the tubular diffuser.

[0005] However, the application does not explicitly describe the design method of the diffuser meridian centerline, and the embodiment still uses the original diffuser meridian centerline of the prototype. This fixed form of diffuser meridian centerline cannot meet the urgent need for further reducing the radial size and achieving compact design of the tubular diffuser, and lacks design flexibility, which further limits the full play of the performance of the tubular diffuser. SUMMARY

[0006] The purpose of the present application is to avoid the shortcomings of the prior art and provide a tubular diffuser meridian centerline design method that realizes high design flexibility and low design complexity for centrifugal or mixed flow compressor tubular diffusers.

[0007] To achieve the above purpose, the technical solution adopted by the present application is as follows: a tubular diffuser meridian centerline design method, comprising the following steps:

[0008] Step one, in the design coordinate system of the diffuser meridional flow passage center line, the impeller outlet radius, the axial coordinate corresponding to the impeller meridional flow passage center line outlet, and the radial and axial dimensions of the diffuser meridional flow passage center line inlet and the radial dimension of the diffuser meridional flow passage center line outlet are given, and the diffuser meridional flow passage center line is divided into three parts: an inlet straight section, a bend transition section and an outlet axial straight section;

[0009] Further, the proportion of the inlet straight section and the outlet axial straight section in the diffuser meridional flow passage center line is determined; at the same time, the ratio of the radial dimension of the diffuser meridional flow passage center line inlet and the radial dimension of the diffuser meridional flow passage center line outlet to the impeller outlet radius is determined, and the included angle of the diffuser meridional flow passage center line inlet and the diffuser meridional flow passage center line outlet with the horizontal plane is determined;

[0010] Step two, based on the three parts of the diffuser meridional flow passage center line, the total length of the diffuser meridional flow passage center line is segmented and normalized, and then the inclination angle distribution of the diffuser meridional flow passage center line varying with the normalization is defined, which includes the inclination angle distribution of the inlet straight section, the inclination angle distribution of the outlet axial straight section and the inclination angle distribution of the bend transition section;

[0011] Among them, the inclination angle distribution of the inlet straight section is constant as the included angle of the diffuser meridional flow passage center line inlet with the horizontal plane; the inclination angle distribution of the outlet axial straight section is constant as the included angle of the diffuser meridional flow passage center line outlet with the horizontal plane;

[0012] The inclination angle distribution of the bend transition section is controlled by a first-order or second-order or third-order Bezier curve, which is used to realize the smooth transition from the inclination angle distribution of the inlet straight section to the inclination angle distribution of the outlet axial straight section, that is:

[0013] The starting end horizontal and vertical coordinates of the Bezier curve are recorded as the proportion of the inlet straight section in the diffuser meridional flow passage center line and the included angle of the diffuser meridional flow passage center line inlet with the horizontal plane, respectively;

[0014] The terminal end horizontal and vertical coordinates of the Bezier curve are recorded as the proportion of the outlet axial straight section in the diffuser meridional flow passage center line and the included angle of the diffuser meridional flow passage center line outlet with the horizontal plane, respectively;

[0015] The intermediate control points of the Bezier curve are defined and controlled according to design requirements;

[0016] Step three, calculate the total length of the diffuser meridional flow passage center line;

[0017] Step four, based on the total length and the inclination angle distribution of the diffuser meridional flow passage center line, obtain the two-dimensional coordinate distribution of the diffuser meridional flow passage center line, that is, complete the geometric design of the diffuser meridional flow passage center line.

[0018] Further, the diffuser is a centrifugal or mixed flow compressor;

[0019] When the angle between the diffuser meridional flow passage center line and the horizontal plane at the inlet is 90 degrees, it is a centrifugal compressor, at this time, the inlet straight line segment is recorded as the inlet radial straight line segment;

[0020] When the angle between the diffuser meridional flow passage center line and the horizontal plane at the inlet is less than 90 degrees and greater than 0 degrees, it is a mixed flow compressor, at this time, the inlet straight line segment is recorded as the inlet oblique straight line segment;

[0021] At the same time, when the proportion of the inlet radial straight line segment or the inlet oblique straight line segment in the diffuser meridional flow passage center line is 0, the diffuser meridional flow passage center line is only composed of the elbow transition segment and the outlet axial straight line segment.

[0022] Further, the step two is to segment and normalize the total length of the diffuser meridional flow passage center line, that is, to normalize the dimensionless form of the three parts corresponding to the diffuser meridional flow passage center line, respectively represented as:

[0023] The inlet straight line segment is , the elbow transition segment is , and the outlet axial straight line segment is ;

[0024] Wherein, represents the proportion of the inlet straight line segment in the diffuser meridional flow passage center line, represents the proportion of the outlet axial straight line segment in the diffuser meridional flow passage center line;

[0025] Further, in the inclination angle distribution of the diffuser meridional flow passage center line, the angle between the diffuser meridional flow passage center line and the horizontal plane at the inlet is recorded as , and the angle between the diffuser meridional flow passage center line and the horizontal plane at the outlet is recorded as ;

[0026] In the inclination angle distribution of the elbow transition segment, the horizontal and vertical coordinates of the starting end of the Bezier curve are recorded as and , respectively, and the horizontal and vertical coordinates of the terminal end of the Bezier curve are recorded as and ;

[0027] At this time, the uniform distribution of the horizontal coordinate control point is used as the initial arrangement, that is:

[0028] If it is a first-order Bezier curve, that is, the control point coordinates corresponding to the first-order Bezier curve are and ;

[0029] If it is a second order Bezier curve, i.e. there are control point coordinates corresponding to the second order Bezier curve as , and ;

[0030] and in actual design, the adjustment range of the control point coordinates complies with:

[0031] the starting end to the terminal end horizontal coordinates satisfy , and the starting end to the terminal end vertical coordinates satisfy ;

[0032] If it is a third order Bezier curve, i.e. there are control point coordinates corresponding to the third order Bezier curve as: , , and ;

[0033] and in actual design, the adjustment range of the control point coordinates complies with:

[0034] the starting end to the terminal end horizontal coordinates satisfy , and the starting end to the terminal end vertical coordinates satisfy .

[0035] Further, in step three, the total length of the diffuser meridional flow passage center line is:

[0036]

[0037] In the formula, is the impeller outlet radius, is the radial dimension of the diffuser meridional flow passage center line inlet, is the radial dimension of the diffuser meridional flow passage center line outlet, is the ratio of the radial dimension of the diffuser meridional flow passage center line inlet to the impeller outlet radius , is the ratio of the radial dimension of the diffuser meridional flow passage center line outlet to the impeller outlet radius , and the function represents the inclination angle distribution of the diffuser meridional flow passage center line; is the number of discrete division points of the inclination angle distribution, and is used to ensure the accuracy of the calculated value; when , represents the inclination angle at the th discrete point on the diffuser meridional flow passage center line, such as represents the inclination angle at the 1st discrete point, This represents the inclination angle at the last discrete point;

[0038] At the same time, it also satisfies:

[0039]

[0040] In the formula, The angle between the diffuser meridional channel centerline inlet and the horizontal plane. It is the angle between the centerline outlet of the diffuser meridional channel and the horizontal plane.

[0041] Furthermore, step four specifically involves:

[0042] By discretizing the inclination angle distribution of the diffuser meridional channel centerline, and calculating the positional changes of the diffuser meridional channel centerline in the axial and radial directions by accumulating the results in an integral, the two-dimensional discrete point coordinate distribution of the diffuser meridional channel centerline is obtained as follows:

[0043]

[0044] In the formula, , These are the coordinates of each discrete point on the centerline of the obtained diffuser meridional channel in the axial and radial directions, respectively. The total length of the centerline of the diffuser meridional channel; function This indicates the angle distribution of the centerline of the diffuser meridional channel; The number of discrete division points for the tilt angle distribution, and This is used to ensure the calculated results The value is precise; when hour, Indicates the first [unit / item] on the center line of the diffuser meridional channel. The inclination angle at discrete points, such as This represents the inclination angle at the first discrete point. This represents the inclination angle at the last discrete point;

[0045] at the same time, Also satisfies:

[0046]

[0047] In the formula, The angle between the diffuser meridional channel centerline inlet and the horizontal plane. It is the angle between the centerline outlet of the diffuser meridional channel and the horizontal plane.

[0048] Furthermore, it also includes the redesign steps for the existing given diffuser meridional centerline:

[0049] In the design coordinate system of the diffuser meridional channel centerline, the total length of the given diffuser meridional channel centerline is obtained based on the two-dimensional discrete point coordinate distribution of the given diffuser meridional channel centerline.

[0050] Then, based on adjacent two-dimensional coordinate points, the inclination angle distribution of the given diffuser meridional channel centerline is obtained. Furthermore, the given diffuser meridional channel centerline is divided into an inlet straight segment, a bend transition segment, and an outlet axial straight segment, and the proportion of each segment to the total length of the given diffuser meridional channel centerline is determined respectively, thus obtaining the inclination angle distribution of the diffuser meridional channel centerline as normalization changes.

[0051] Furthermore, for the inclination distribution of the bend transition section of a given diffuser meridional channel centerline, the Levenberg-Marquardt algorithm is used to fit a third-order Bezier curve, thereby achieving a parameterized characterization of the entire section of the given diffuser meridional channel centerline.

[0052] Finally, by adjusting the control points of the Bézier curve of the bend transition section, the parametric fitting and modification design of the bend transition section of the given diffuser meridional channel centerline was completed.

[0053] The present invention also provides a tubular diffuser with reduced radial dimensions obtained by the design method of the meridional centerline of the tubular diffuser as described above, wherein:

[0054] The proportion of the straight section at the inlet in the centerline of the diffuser meridional channel The range is 0 to 0.15.

[0055] The proportion of the straight section of the outlet axial direction in the centerline of the diffuser meridional channel The value is 0.1~0.5;

[0056] Radial dimension of diffuser meridional channel centerline outlet The ratio of the impeller outlet radius to the impeller outlet radius The value is 1.2~1.3, a conventional design. The value is above 1.4.

[0057] The beneficial effects of this invention are as follows: The method of this invention can quickly construct tubular diffuser structures that meet engineering requirements, while possessing a high degree of geometric freedom, facilitating subsequent aerodynamic performance optimization design, and significantly expanding the engineering applicability and design space of tubular diffusers. On the other hand, this method can also parametrically fit the centerline of the meridional channel of existing diffusers, enabling rapid reproduction and modification design of existing diffuser channels.

[0058] Compared with the traditional "straight-ellipse-straight" design method, the method has the following advantages: on the one hand, the transition section of the elbow pipe is regulated by the Bezier curve, which has higher modeling freedom and can flexibly adapt to the special mixed flow compressor; on the other hand, the outlet radial size is flexible and adjustable, which can realize the radial size reduction of the diffuser and accurately meet the compact structure requirement of the compressor part of the small aero-engine.

[0059] In the engineering application level, the method has the following advantages: first, the design of the meridian flow passage center line of the centrifugal or mixed flow compressor pipe diffuser is quickly completed; second, relying on the parametric design logic, it has a good program implementation foundation, which is convenient for integration into the automatic modeling process and performance optimization platform, and effectively improves the design efficiency and performance level of the pipe diffuser. In addition, when the diffuser casing and hub profile of a certain type of diffuser are known, the discrete point coordinates of the existing diffuser meridian flow passage center line can be extracted; according to the segmentation logic and design parameter fitting strategy of the method, the existing diffuser meridian flow passage center line can be reproduced, and based on this, the diffuser modification and optimization design can be carried out, and the aerodynamic performance of the prototype compressor can be further improved. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 is a schematic diagram of the diffuser meridian flow passage center line suitable for a centrifugal impeller of the application;

[0061] Figure 2 is a schematic diagram of the diffuser meridian flow passage center line suitable for a mixed flow impeller of the application;

[0062] Figure 3 is a schematic diagram of the diffuser meridian flow passage center line of the application, which changes with the normalized inclination angle distribution;

[0063] Figure 4 is a verification diagram of the independence of the number of discrete points and the total length of the diffuser meridian flow passage center line in the calculation of the total length of the diffuser meridian flow passage center line in the embodiment of the application;

[0064] Figure 5 is a comparison diagram of the diffuser meridian flow passage center line obtained in the embodiment of the application and the NASA HECC prototype diffuser meridian flow passage center line;

[0065] Figure 6 is a comparison diagram of the radial size reduction pipe diffuser model based on the diffuser meridian flow passage center line obtained by the method in the embodiment of the application and the radial size reduction pipe diffuser model based on the NASA HECC prototype diffuser meridian flow passage center line;

[0066] Figure 7It is the center line of the meridian flow passage of the NASA HECC diffuser obtained by parameter fitting based on the design method of the application, and a comparison chart with the center line of the meridian flow passage of the original NASA HECC diffuser. DETAILED DESCRIPTION

[0067] The principles and characteristics of the application are described below in combination with the drawings, and the examples are only used to explain the application and not to limit the scope of the application.

[0068] The diffuser meridian flow passage center line obtained based on the application can be used to design and model the tubular diffuser according to the design method of the tubular diffuser provided with a dovetail leading edge mentioned in the publication No. CN119026282A, and specifically includes:

[0069] According to the absolute Mach number at the outlet of the tubular diffuser, the mass flow of the centrifugal compressor, the total pressure and total temperature at the outlet of the centrifugal impeller, the total pressure and total temperature at the outlet of the tubular diffuser, the absolute Mach number at the inlet of the tubular diffuser, the inlet and outlet blockage coefficients of the tubular diffuser, the inlet throat area and the outlet area of the tubular diffuser are determined;

[0070] According to the inclination angle of the tubular diffuser, the proportion of the inlet straight section in the diffuser meridian flow passage center line and the two-dimensional discrete point coordinate distribution of the diffuser meridian flow passage center line, the outlet metal angle of the radial-taper pipe section of the tubular diffuser and the three-coordinate distribution of the corresponding center line in space are determined;

[0071] According to the outlet metal angle of the radial-taper pipe section of the tubular diffuser, the outlet metal angle of the tubular diffuser and the two-dimensional discrete point coordinate of the diffuser meridian flow passage center line, the three-coordinate distribution of the corresponding center line in space of the radial-rotation axial pipe section of the tubular diffuser is determined;

[0072] According to the three-coordinate distribution of the corresponding center line in space of the radial-taper pipe section and the radial-rotation axial pipe section of the tubular diffuser, the three-coordinate distribution of the corresponding center line in space of the tubular diffuser is obtained by merging;

[0073] According to the two-dimensional discrete point coordinate distribution of the diffuser meridian flow passage center line, the geometric throat length coefficient of the tubular diffuser, the expansion angle of the taper pipe section, the inlet throat area, the outlet area of the tubular diffuser and the proportion of the inlet straight section in the diffuser meridian flow passage center line , the cross-sectional area distribution law of the tubular diffuser from the inlet to the outlet is determined;

[0074] Further, the different cross-sectional distributions along the center line in space are determined, and the single-channel modeling design of the tubular diffuser is completed by sweeping;

[0075] Finally, according to the radial dimension of the inlet of the meridian flow passage center line of the diffuser, the inclination angle of the tubular diffuser, the number of the circumferential channels of the tubular diffuser and the inlet throat area of the tubular diffuser, the dovetail type leading edge design is completed, and the overall modeling of the tubular diffuser is completed.

[0076] In order to achieve the overall modeling purpose of the tubular diffuser, the present application provides the following specific embodiments:

[0077] Embodiment 1: A method for designing a meridian flow passage center line of a tubular diffuser, comprising the following steps:

[0078] S01, in the design coordinate system of the meridian flow passage center line of the diffuser, the outlet radius of the impeller, the axial coordinate corresponding to the outlet of the meridian flow passage center line of the impeller, and the radial and axial dimensions of the inlet of the meridian flow passage center line of the diffuser and the radial dimension of the outlet of the meridian flow passage center line of the diffuser are given, and the meridian flow passage center line of the diffuser is divided into three parts: an inlet straight section, a bend transition section and an outlet axial straight section;

[0079] Further, the proportion of the inlet straight section and the outlet axial straight section in the meridian flow passage center line of the diffuser is determined; at the same time, the ratio of the radial dimension of the inlet of the meridian flow passage center line of the diffuser and the radial dimension of the outlet of the meridian flow passage center line of the diffuser to the outlet radius of the impeller is determined, and the included angle of the inlet of the meridian flow passage center line of the diffuser and the outlet of the meridian flow passage center line of the diffuser with the horizontal plane is determined.

[0080] S02, based on the three parts of the meridian flow passage center line of the diffuser, the total length of the meridian flow passage center line of the diffuser is segmented and normalized, that is, the normalized dimensionless form of the three parts of the meridian flow passage center line of the diffuser is represented as:

[0081] The inlet straight section is , the bend transition section is , and the outlet axial straight section is ;

[0082] wherein, the proportion of the inlet straight section in the meridian flow passage center line of the diffuser is represented by , and the proportion of the outlet axial straight section in the meridian flow passage center line of the diffuser is represented by

[0083] S03, further define the inclination angle distribution of the meridian flow passage center line of the diffuser with the normalized change, the inclination angle distribution specifically includes the inclination angle distribution of the inlet straight section, the inclination angle distribution of the outlet axial straight section and the inclination angle distribution of the bend transition section;

[0084] wherein, the inclination angle distribution of the inlet straight section is always the included angle between the inlet of the meridian flow passage center line of the diffuser and the horizontal plane, denoted as The angle distribution of the straight segment along the outlet axis is always the angle between the outlet of the diffuser meridional channel centerline and the horizontal plane, denoted as . ;

[0085] The inclination angle distribution of the bend transition section is controlled by a third-order Bézier curve to achieve a smooth transition from the inclination angle distribution of the inlet straight section to the inclination angle distribution of the outlet axial straight section. Furthermore, the horizontal and vertical coordinates of the starting point of the Bézier curve are respectively denoted as the proportion of the inlet straight section within the diffuser meridional channel centerline. The angle between the diffuser meridional channel centerline inlet and the horizontal plane ;

[0086] The x and y coordinates of the terminal ends of the Bézier curve are denoted as the proportion of the straight segment along the outlet axis in the centerline of the diffuser meridional channel, respectively. The angle between the diffuser meridional channel centerline outlet and the horizontal plane ;

[0087] At this point, if the initial arrangement is based on a uniform distribution of control points on the horizontal coordinate, then:

[0088] A third-order Bézier curve, that is, the coordinates of the control points corresponding to a third-order Bézier curve, are: , , and ;

[0089] Furthermore, in actual design, the control point coordinate adjustment range follows:

[0090] The x-coordinate from the starting point to the ending point satisfies The ordinate from the starting end to the ending end satisfies .

[0091] This allows the intermediate control points of the Bézier curve to be defined and controlled according to design requirements.

[0092] S04. Calculate the total length of the diffuser meridional channel centerline. for:

[0093]

[0094] In the formula, Where is the impeller outlet radius. This refers to the radial dimension of the diffuser meridional channel centerline inlet. The radial dimension of the diffuser meridional channel centerline outlet. The radial dimension of the diffuser meridional channel centerline inlet With impeller outlet radius The ratio, the radial dimension of the meridional passage centerline of the diffuser at the exit is a function of the ratio of the meridional passage centerline exit radius of the diffuser to the impeller exit radius ; represents the inclination distribution of the meridional passage centerline of the diffuser; is the number of discrete points of the inclination distribution, and is used to ensure the accuracy of the calculated value; when , represents the inclination at the th discrete point on the meridional passage centerline of the diffuser, for example, represents the inclination at the 1st discrete point, represents the inclination at the last discrete point;

[0095] At the same time, it also satisfies:

[0096]

[0097] wherein, is the angle between the meridional passage centerline entrance of the diffuser and the horizontal plane, is the angle between the meridional passage centerline exit of the diffuser and the horizontal plane.

[0098] S05, by discretizing the inclination distribution of the meridional passage centerline of the diffuser, the position changes of the meridional passage centerline of the diffuser in the axial and radial directions are calculated in the form of integration, so as to obtain the two-dimensional discrete point coordinate distribution of the meridional passage centerline of the diffuser, which is expressed as:

[0099]

[0100] wherein, , are the coordinates of each discrete point of the obtained meridional passage centerline of the diffuser in the axial and radial directions, respectively; is the total length of the meridional passage centerline of the diffuser; the function represents the inclination distribution of the meridional passage centerline of the diffuser; is the number of discrete points of the inclination distribution, and is used to ensure the accuracy of the calculated value;

[0101] when , represents the inclination at the th discrete point on the meridional passage centerline of the diffuser, for example, represents the inclination at the 1st discrete point, represents the inclination at the last discrete point;

[0102] At the same time, Also satisfied:

[0103] ,

[0104] In the formula, is the included angle between the inlet of the diffuser meridional passage center line and the horizontal plane, is the included angle between the outlet of the diffuser meridional passage center line and the horizontal plane, that is, the geometric design of the diffuser meridional passage center line is completed.

[0105] Example 2: as Figure 1 Example 1, except that the diffuser is a centrifugal compressor, so that the included angle between the inlet of the diffuser meridional passage center line and the horizontal plane is 90 degrees, at this time, the inlet straight line segment is recorded as the inlet radial straight line segment;

[0106] As Figure 1 shown in the figure, is the proportion of the inlet radial straight line segment in the diffuser meridional passage center line, is the proportion of the outlet axial straight line segment in the diffuser meridional passage center line, is the outlet radius of the centrifugal impeller, is the radial size of the inlet of the diffuser meridional passage center line, is the radial size of the outlet of the diffuser meridional passage center line;

[0107] At the same time, when the proportion of the inlet radial straight line segment in the diffuser meridional passage center line is 0, the diffuser meridional passage center line is only composed of the elbow transition section and the outlet axial straight line segment.

[0108] At this point, the final obtained pipe diffuser meridional passage center line of the pipe diffuser is:

[0109] The proportion of the inlet radial straight line segment in the diffuser meridional passage center line is 0~0.15;

[0110] The proportion of the outlet axial straight line segment in the diffuser meridional passage center line is 0.1~0.5;

[0111] The ratio of the radial size of the outlet of the diffuser meridional passage center line to the outlet radius of the impeller is 1.2~1.3, and the value of the conventional design is above 1.4; by reducing to achieve the design purpose of reducing the radial size of the pipe diffuser.

[0112] Example 3: as Figure 2As shown, the same as example 1, except that the diffuser is a mixed flow compressor, then the angle between the diffuser meridional flow passage center line and the horizontal plane is less than 90 degrees and greater than 0 degrees, at this time, the inlet inclined straight line segment is recorded as the inlet inclined straight line segment in the diffuser meridional flow passage center line;

[0113] As shown in the figure Figure 2 , is the proportion of the inlet inclined straight line segment in the diffuser meridional flow passage center line, is the proportion of the outlet axial straight line segment in the diffuser meridional flow passage center line, is the outlet radius of the mixed flow impeller, is the radial size of the inlet of the diffuser meridional flow passage center line, is the radial size of the outlet of the diffuser meridional flow passage center line;

[0114] At the same time, when the proportion of the inlet inclined straight line segment in the diffuser meridional flow passage center line is 0, then the diffuser meridional flow passage center line is only composed of the elbow transition section and the outlet axial straight line segment.

[0115] At this point, the final diffuser meridional flow passage center line of the tubular diffuser is obtained:

[0116] The proportion of the inlet inclined straight line segment in the diffuser meridional flow passage center line is 0~0.15;

[0117] The proportion of the outlet axial straight line segment in the diffuser meridional flow passage center line is 0.1~0.5;

[0118] The ratio of the radial size of the outlet of the diffuser meridional flow passage center line to the outlet radius of the impeller is 1.2~1.3, and the value of the conventional design is above 1.4; by reducing to achieve the design purpose of reducing the radial size of the tubular diffuser.

[0119] Example 4: the same as example 1, except that the inclination distribution of the elbow transition section is controlled by a first-order Bezier curve, which is used to realize the smooth transition from the inclination distribution of the inlet straight line segment to the inclination distribution of the outlet axial straight line segment, and in the inclination distribution of the elbow transition section, the horizontal and vertical coordinates of the starting end of the Bezier curve are recorded as and , and the horizontal and vertical coordinates of the terminal end of the Bezier curve are recorded as and ; at this time, the uniform distribution of the horizontal coordinate control points is used as the initial arrangement, then the first-order Bezier curve, that is, the control point coordinates corresponding to the first-order Bezier curve are and .

[0120] Example 5: The inclination angle distribution of the elbow transition section is controlled by a second-order Bezier curve, which is used to achieve smooth transition from the inclination angle distribution of the inlet straight section to the inclination angle distribution of the outlet axial straight section. In the inclination angle distribution of the elbow transition section, the starting end of the Bezier curve is denoted as and , and the terminal end of the Bezier curve is denoted as and .

[0121] At this time, the initial arrangement is in the form of uniform distribution of the horizontal coordinate control points, and then

[0122] In the inclination angle distribution of the elbow transition section, the starting end of the Bezier curve is denoted as and , and the terminal end of the Bezier curve is denoted as and . At this time, the initial arrangement is in the form of uniform distribution of the horizontal coordinate control points, and then the second-order Bezier curve is obtained, that is, the control point coordinates corresponding to the second-order Bezier curve are , and . In actual design, the adjustment range of the control point coordinates follows: the horizontal coordinates from the starting end to the terminal end satisfy , and the vertical coordinates from the starting end to the terminal end satisfy .

[0123] Example 6: The same as example 1, except that it further includes the modification design steps of the existing given diffuser meridional flow passage center line:

[0124] In the design coordinate system of the diffuser meridional flow passage center line, according to the two-dimensional discrete point coordinate distribution of the given diffuser meridional flow passage center line, the total length of the given diffuser meridional flow passage center line is obtained;

[0125] Then, based on the adjacent two-dimensional coordinate points, the inclination angle distribution of the given diffuser meridional flow passage center line is obtained, and then the given diffuser meridional flow passage center line is divided into an inlet straight section, an elbow transition section and an outlet axial straight section, and the proportion of each section in the total length of the given diffuser meridional flow passage center line is determined, to obtain the inclination angle distribution of the diffuser meridional flow passage center line with normalized change;

[0126] Furthermore, for the inclination distribution of the bend transition section of a given diffuser meridional channel centerline, the Levenberg-Marquardt algorithm is used to fit a third-order Bezier curve, thereby achieving a parameterized characterization of the entire section of the given diffuser meridional channel centerline.

[0127] Finally, by adjusting the control points of the Bézier curve of the bend transition section, the parametric fitting and modification design of the bend transition section of the given diffuser meridional channel centerline was completed.

[0128] like Figure 1 and Figures 3-7 To further illustrate the technical solution and effects of the present invention, the following specific design examples are provided.

[0129] Specific design example 1:

[0130] This example uses the diffuser meridional centerline design of the NASA HECC high-ratio centrifugal compressor (model information from the NASA public report "NASA-High Efficiency Centrifugal Compressor") as an example to implement a radially reduced tubular diffuser meridional centerline design. Finally, a model of a radially reduced tubular diffuser is constructed, applicable to the meridional centerline form of the NASA HECC centrifugal impeller, as shown below. Figure 1 As shown, it includes the following steps:

[0131] Step 1: Determine the design input parameters:

[0132] Based on the one-dimensional outlet parameters of the centrifugal impeller, determine the required input variables, mainly including: the outer diameter of the centrifugal impeller outlet. Axial coordinates corresponding to the outlet of the impeller meridional channel centerline Diffuser meridional channel centerline inlet radial dimension outer diameter of centrifugal impeller outlet ratio Diffuser meridional channel centerline outlet radial dimension outer diameter of centrifugal impeller ratio It should be noted that the NASA HECC prototype diffuser This example aims to significantly reduce This method reduces the radial dimension of the tubular diffuser, achieving a compact design for the tubular diffuser.

[0133] Angle between the diffuser meridional channel centerline inlet and the horizontal plane The angle is 90 degrees, the angle between the diffuser meridional channel centerline outlet and the horizontal plane. The proportion of the inlet radial straight section in the meridian flow passage center line of the diffuser The proportion of the outlet axial straight section in the meridian flow passage center line of the diffuser ;

[0134] Step two, the normalized diffuser meridian flow passage center line length is obtained, and its corresponding partitions in the inlet radial straight section, elbow transition section and outlet axial straight section are determined, respectively as follows:

[0135] Inlet radial straight section , that is ;

[0136] Elbow transition section , that is ;

[0137] Outlet axial straight section , that is ;

[0138] Step three, the inclination angle distribution of the diffuser meridian flow passage center line is constructed, as shown in the accompanying drawings, and the specific conditions are as follows: Figure 3 The inclination angle distribution of the inlet radial straight section is constant at 90 degrees, and the corresponding horizontal coordinate interval is

[0139] ;

[0140] The inclination angle distribution of the elbow transition section is controlled by a second-order Bezier curve, and the coordinates of the middle control point are , and the corresponding horizontal coordinate interval of the elbow transition section is ;

[0141] The inclination angle distribution of the outlet axial straight section is constant at 0 degrees, and the corresponding horizontal coordinate interval is ;

[0142] Step four, according to the inclination angle distribution of the diffuser meridian flow passage center line constructed in step three, the total length of the diffuser meridian flow passage center line is determined by numerical integration :

[0143] To verify the correlation between the calculation accuracy and the discrete division point number , the convergence test is performed on different discrete division point number values in this example, as shown in the accompanying drawings. The horizontal coordinate Figure 4 ( is the discrete division point number), and the vertical coordinate is the corresponding calculation value. From the figure, it can be seen that when the discrete division point number , the calculation value of tends to be stable, and it is considered that when , the calculation accuracy can be guaranteed​ The calculation accuracy is determined accordingly. Based on this, this embodiment selects the number of discrete partitioning points. The final calculated total length of the diffuser meridional channel centerline ;

[0144] Step 5: Two-dimensional discrete point coordinate distribution of the centerline of the output diffuser meridional channel :

[0145] Based on the inclination distribution of the diffuser meridional centerline and the total length of the diffuser meridional centerline The coordinate distribution of two-dimensional discrete points on the centerline of the diffuser meridional channel was calculated sequentially. This example outputs a total of 60 points, as shown in Table 1. Table 1 shows the coordinates of two-dimensional discrete points on the centerline of the diffuser meridional channel with radially reduced dimensions. The data in the table is in mm and will be used for the design and modeling of subsequent tubular diffusers.

[0146] Table 1

[0147]

[0148] Figure 5 This is a schematic diagram comparing the centerline of the diffuser meridional channel with radial dimension reduction obtained in Specific Design Example 1 (radial dimension reduction marked in the figure_R42=1.2) with the centerline of the diffuser meridional channel of the NASA HECC centrifugal compressor prototype (NASAHECC prototype_R42=1.409).

[0149] As can be clearly seen from the figure, the radial dimension of the diffuser meridional channel centerline is much smaller than that of the prototype design, which verifies the effectiveness of the design method proposed in this invention.

[0150] Figure 6 To maintain consistent design parameters, based on respectively Figure 5 A comparative schematic diagram of the three-dimensional models of tubular diffusers constructed using the centerlines of the meridional channels of two different diffusers is shown. The results show that the tubular diffuser model constructed using the design method of this invention has a significant reduction in radial dimensions, further verifying the potential of this method to achieve radial dimension reduction of diffusers and achieve the goal of compact diffuser design.

[0151] Specific design example 2:

[0152] The present example takes NASA HECC high pressure ratio centrifugal compressor as an example, realizes the parametric fitting of the given diffuser meridional flow passage center line, and compares the fitted diffuser meridional flow passage center line with the given diffuser meridional flow passage center line, including the following steps:

[0153] Step one, according to the two-dimensional discrete point coordinate distribution of the given diffuser meridional flow passage center line, the total length of the diffuser meridional flow passage center line is calculated ;

[0154] Step two, based on the two-dimensional discrete point coordinate distribution, the inclination distribution of the diffuser meridional flow passage center line is obtained, and the proportion of the inlet radial straight line segment in the diffuser meridional flow passage center line is obtained through the inclination distribution , the proportion of the outlet axial straight line segment in the diffuser meridional flow passage center line , the angle between the inlet of the diffuser meridional flow passage center line and the horizontal plane is 90 degrees, and the angle between the outlet of the diffuser meridional flow passage center line and the horizontal plane is 0 degrees;

[0155] Step three, for the inclination distribution of the elbow transition section, the present example adopts Levenberg-Marquardt algorithm for 3-order Bezier curve fitting, and the coordinates of the four points corresponding to the Bezier curve are respectively 、 、 and ;

[0156] Step four, based on the inclination distribution of the diffuser meridional flow passage center line obtained after parametric fitting, the total length of the diffuser meridional flow passage center line is recalculated , and the two-dimensional discrete point coordinate distribution of the diffuser meridional flow passage center line is output.

[0157] Figure 7 The comparison figure of the diffuser meridional flow passage center line (HECC diffuser center line (fitting)) obtained in the specific design example 2 and the given diffuser meridional flow passage center line (HECC diffuser center line (prototype)) is shown in the figure. As can be seen from the figure, the two diffuser meridional flow passage center lines basically coincide, and in the elbow transition section, the diffuser meridional flow passage center line obtained by the present method has a slight deviation from the given diffuser meridional flow passage center line. This difference may mainly be caused by the insufficient order of the Bezier curve used, thereby verifying the feasibility of the present design method for parameterizing the given diffuser meridional flow passage center line.

[0158] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for designing a meridional flow passage centerline of a vaneless diffuser, characterized by, The method comprises the following steps: Step one, in the design coordinate system of the diffuser meridian flow passage center line, the impeller outlet radius, the axial coordinate corresponding to the impeller meridian flow passage center line outlet, the radial and axial dimensions of the diffuser meridian flow passage center line inlet and the radial dimension of the diffuser meridian flow passage center line outlet are given, and the diffuser meridian flow passage center line is divided into three parts, namely, an inlet straight section, a bend transition section and an outlet axial straight section; Further, the proportion of the inlet straight section and the outlet axial straight section in the diffuser meridian flow passage center line is determined; meanwhile, the ratio of the radial dimension of the diffuser meridian flow passage center line inlet and the radial dimension of the diffuser meridian flow passage center line outlet to the impeller outlet radius is determined, and the included angle of the diffuser meridian flow passage center line inlet and the diffuser meridian flow passage center line outlet with the horizontal plane is determined; Step two, based on the three parts of the diffuser meridian flow passage center line, the total length of the diffuser meridian flow passage center line is segmented and normalized, and then the inclination angle distribution of the diffuser meridian flow passage center line varying with the normalization is defined, which specifically includes the inclination angle distribution of the inlet straight section, the inclination angle distribution of the outlet axial straight section and the inclination angle distribution of the bend transition section; The inclination angle distribution of the inlet straight section is always the included angle of the diffuser meridian flow passage center line inlet with the horizontal plane; the inclination angle distribution of the outlet axial straight section is always the included angle of the diffuser meridian flow passage center line outlet with the horizontal plane; The inclination angle distribution of the bend transition section is controlled by a first-order or second-order or third-order Bezier curve, which is used to realize the smooth transition from the inclination angle distribution of the inlet straight section to the inclination angle distribution of the outlet axial straight section, so that: The starting end horizontal and vertical coordinates of the Bezier curve are respectively recorded as the proportion of the inlet straight section in the diffuser meridian flow passage center line and the included angle of the diffuser meridian flow passage center line inlet with the horizontal plane; The terminal end horizontal and vertical coordinates of the Bezier curve are respectively recorded as the proportion of the outlet axial straight section in the diffuser meridian flow passage center line and the included angle of the diffuser meridian flow passage center line outlet with the horizontal plane; The middle control point of the Bezier curve is defined and controlled according to design requirements; Step three, the total length of the diffuser meridian flow passage center line is calculated; Step four, based on the total length and the inclination angle distribution of the diffuser meridian flow passage center line, the two-dimensional coordinate distribution of the diffuser meridian flow passage center line is obtained, that is, the geometric design of the diffuser meridian flow passage center line is completed.

2. The tubular diffuser meridional passage centerline design method of claim 1 wherein, The diffuser is a centrifugal or mixed flow compressor; When the included angle of the diffuser meridian flow passage center line inlet with the horizontal plane is 90 degrees, it is a centrifugal compressor, at this time, the inlet straight section is recorded as an inlet radial straight section; When the included angle of the diffuser meridian flow passage center line inlet with the horizontal plane is less than 90 degrees and greater than 0 degree, it is a mixed flow compressor, at this time, the inlet straight section is recorded as an inlet oblique straight section; At the same time, when the proportion of the inlet radial straight section or the inlet oblique straight section in the diffuser meridian flow passage center line is 0, the diffuser meridian flow passage center line is only composed of the bend transition section and the outlet axial straight section.

3. The tubular diffuser meridional passage centerline design method of claim 1 wherein, The step two is to segment and normalize the total length of the diffuser meridional flow passage center line, that is, to normalize the three parts of the diffuser meridional flow passage center line into dimensionless forms, respectively denoted as: The inlet straight section is , the elbow transition section is , and the outlet axial straight section is ; wherein, represents the proportion of the inlet straight line segment in the diffuser meridian flow passage center line, represents the proportion of the outlet axial straight line segment in the diffuser meridian flow passage center line; Further, in the distribution of the inclination angle of the meridian flow passage center line of the diffuser, the included angle between the inlet of the meridian flow passage center line of the diffuser and the horizontal plane is denoted as ; and the included angle between the outlet of the meridian flow passage center line of the diffuser and the horizontal plane is denoted as . In the inclination distribution of the elbow transition section, the initial end of the Bezier curve is denoted as and respectively, and the terminal end of the Bezier curve is denoted as and respectively. At this time, the initial arrangement is in the form of uniform distribution of the abscissa control points, and then: If it is a first order Bezier curve, there are control point coordinates corresponding to the first order Bezier curve and ; If it is a second order Bezier curve, that is, there are control point coordinates corresponding to the second order Bezier curve , and ; And in the actual design, the adjustment range of the control point coordinates complies with: The starting end to the terminal end horizontal coordinate satisfies The starting end to the terminal end vertical coordinate satisfies ; If it is a third order Bezier curve, there are three control points corresponding to the third order Bezier curve, and the coordinates of the control points are: , , and ; And in the actual design, the adjustment range of the control point coordinates complies with: The starting end to the terminal end horizontal coordinate satisfies The starting end to the terminal end vertical coordinate satisfies .

4. The tubular diffuser meridional passage centerline design method of claim 1 wherein, In step three, the total length of the centerline of the diffuser meridional passage is: Ldiffuser = Ldiffuser,1 + Ldiffuser,2 + Ldiffuser,3 ， wherein is the outlet radius of the impeller, is the radial dimension of the inlet of the meridional flow passage of the diffuser, is the radial dimension of the outlet of the meridional flow passage of the diffuser, is the radial dimension of the inlet of the meridional flow passage of the diffuser is the ratio of the radial dimension of the inlet of the meridional flow passage of the diffuser to the outlet radius of the impeller is the ratio of the radial dimension of the outlet of the meridional flow passage of the diffuser to the outlet radius of the impeller is the ratio of the radial dimension of the outlet of the meridional flow passage of the diffuser to the outlet radius of the impeller is the ratio of the radial dimension of the outlet of the meridional flow passage of the diffuser to the outlet radius of the impeller is the ratio of the radial dimension of the outlet of the meridional flow passage of the diffuser to the outlet radius of the impeller represents the distribution of the inclination angle of the meridional flow passage of the diffuser; is the number of discrete points of the distribution of the inclination angle, and is used to ensure the accuracy of the calculated value of ; when , represents the inclination angle at the discrete point of the meridional flow passage of the diffuser, represents the inclination angle at the first discrete point, represents the inclination angle at the last discrete point. Meanwhile, it also satisfies: ， wherein is the angle between the inlet of the diffuser meridional flow passage center line and the horizontal plane, is the angle between the outlet of the diffuser meridional flow passage center line and the horizontal plane.

5. The tubular diffuser meridional passage centerline design method of claim 1 wherein, The step four is specifically: By discretizing the inclination distribution of the diffuser meridional flow passage center line, the position changes of the diffuser meridional flow passage center line in the axial and radial directions are calculated in the integral form, so as to obtain the two-dimensional discrete point coordinate distribution of the diffuser meridional flow passage center line, denoted as: ， wherein , are the coordinates of each discrete point of the obtained diffuser meridional passage center line in axial and radial directions, respectively; is the total length of the diffuser meridional passage center line; the function represents the inclination distribution of the diffuser meridional passage center line; is the number of discrete division points of the inclination distribution, and is used to ensure the accuracy of the calculated value; when , represents the inclination at the discrete point on the diffuser meridional passage center line, represents the inclination at the first discrete point, represents the inclination at the last discrete point; At the same time, Also satisfied: ， In the formula, is the angle between the inlet of the meridian flow passage center line of the diffuser and the horizontal plane, is the angle between the outlet of the meridian flow passage center line of the diffuser and the horizontal plane.

6. The tubular diffuser meridional passage centerline design method of any of claims 1-5, wherein, It also includes the retrofit design steps of the existing given diffuser meridional flow passage center line: In the design coordinate system of the diffuser meridional flow passage center line, according to the two-dimensional discrete point coordinate distribution of the given diffuser meridional flow passage center line, the total length of the given diffuser meridional flow passage center line is obtained; Then, based on the adjacent two-dimensional coordinate points, the inclination distribution of the given diffuser meridional flow passage center line is obtained, and then the given diffuser meridional flow passage center line is divided into an inlet straight section, a bend transition section and an outlet axial straight section, and the proportions of each section in the total length of the given diffuser meridional flow passage center line are determined, so as to obtain the inclination distribution of the diffuser meridional flow passage center line varying with the normalization; Further, for the inclination distribution of the bend transition section of the given diffuser meridional flow passage center line, the Levenberg-Marquardt algorithm is used for third-order Bezier curve fitting, so as to realize the parameterization representation of the whole given diffuser meridional flow passage center line. Finally, by adjusting the Bezier curve control points of the bend transition section, the parameterization fitting and retrofit design of the bend transition section of the given diffuser meridional flow passage center line are completed.

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