Multi-stage mixed-flow water turbine interstage fixed guide vane design method, recording medium and system

Abstract

The invention belongs to the technical field of hydroelectric generation, and particularly relates to a design method, a recording medium and a system for inter-stage fixed guide vanes of a multi-stage mixed-flow water turbine. The design method comprises the steps that a first radial distance value between the inlet end of a blade bone line of the inter-stage fixed guide blade and a center shaft of the second-stage rotating wheel and a second radial distance value between the outlet end of the blade bone line of the inter-stage fixed guide blade and the center shaft are obtained; according to the water inlet direction of the second-stage runner, an inlet end placement angle value of a blade bone line is obtained; according to the water flow design parameters of the multi-stage mixed-flow water turbine, the design parameters of the second-stage runner and the obtained second radial distance value, the placement angle value of the outlet end of the blade bone line is obtained through calculation; according to the first radial distance value, the second radial distance value and the inlet end placement angle value and the outlet end placement angle value of the blade bone line, the placement angle value corresponding to each point on the blade bone line is calculated; and determining the space shape of the interstage fixed guide vane according to the placement angle value corresponding to each point on the blade bone line and the bone line equation of the interstage fixed guide vane.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydropower generation, and particularly relates to a design method, a recording medium and a system for an inter-stage stay vane of a multi-stage Francis turbine. Background Art

[0002] At high water heads, especially when the water head is greater than 700 m, impulse turbines are generally used. However, since the runner of the impulse turbine operates under the atmospheric pressure above the tail water surface, the jet velocity of the nozzle and the rotational speed of the bucket runner are high, and its single-unit capacity is limited by the runner material (the current maximum single-unit capacity of the impulse turbine is 423 MW). Moreover, when the water head is higher than 700 m and the sediment content in the river is relatively large, the sediment wear problem of the impulse turbine is serious, and the equipment maintenance period and service life are greatly shortened.

[0003] The Francis turbine operates entirely in the underwater flow passage, with a lower rotational speed and a larger single-unit capacity (the current maximum single-stage capacity is 1000 MW). In addition, compared with the impulse turbine, the Francis turbine has higher efficiency and better performance in resisting sediment. However, due to the limitation of the stable operation range of the Francis turbine runner, its water head range is within 30 m - 700 m. Especially for a single-stage Francis turbine generator unit with a relatively large capacity, after the water head exceeds 600 m, indicators such as the stable operation area and manufacturing difficulty deteriorate sharply, and it is difficult to reasonably select and manufacture the turbine generator unit. At present, the operating water heads in the western region of China where river hydropower development conditions are available are as high as 800 m - 1000 m. Due to the narrow river channel and limited layout space for the power station powerhouse, the single-unit capacity of the turbine generator unit needs to reach 500 MW - 800 MW, and these two indicators of the single-unit capacity and the operating water head respectively exceed the maximum single-unit capacity of the impulse turbine and the maximum operating water head of the single-stage Francis turbine.

[0004] For high-head power stations under the above development conditions, those skilled in the art have designed multi-stage Francis turbines and adopted a development scheme of a single-stage power station equipped with multi-stage Francis turbines to consume the water head in order to meet these two indicators of the single-unit capacity and the operating water head at the same time. However, the existing multi-stage Francis turbines usually have the problem of generating a non-uniform flow field at the outlet of the first-stage runner (when the water head exceeds a certain height, the same problem also occurs in the draft tube of the single-stage Francis turbine). And the above problems will have a greater impact on the stable operation of the multi-stage Francis turbine and the energy conversion of the second-stage runner. Therefore, it is necessary to develop a standardized design method for the inter-stage stay vane to optimize and adjust the outlet flow field of the first-stage runner and provide good inlet flow conditions for the second-stage runner, which is very necessary for improving the hydraulic performance of the multi-stage Francis turbine. Summary of the Invention

[0005] In view of the above problems, the present invention provides a design method for the stay vanes between stages of a multi-stage Francis turbine. The water inlet direction of the second-stage runner of the multi-stage Francis turbine is normal water inlet. The design method includes:

[0006] Obtain a first radial distance value between the inlet end of the blade camber line of the stay vane between stages and the central axis of the second-stage runner, and a second radial distance value between the outlet end of the blade camber line and the central axis;

[0007] According to the water inlet direction of the second-stage runner, obtain the installation angle value of the inlet end of the blade camber line; according to the water flow design parameters of the multi-stage Francis turbine, the design parameters of the second-stage runner, and the obtained second radial distance value, calculate and obtain the installation angle value of the outlet end of the blade camber line;

[0008] According to the obtained first radial distance value, second radial distance value, installation angle value of the inlet end of the blade camber line, and installation angle value of the outlet end, calculate and obtain the installation angle values corresponding to each point on the blade camber line;

[0009] According to the installation angle values corresponding to each point on the obtained blade camber line and the camber line equation of the stay vane between stages, determine the spatial shape of the stay vane between stages.

[0010] By designing the blade camber line of the stay vane between stages through the design method for the stay vane between stages of the multi-stage Francis turbine provided by the present invention, the velocity field distribution at the outlet of the first-stage runner can be effectively adjusted, ensuring a uniform distribution of the water flow velocity moment at the inlet of the second-stage runner, providing good inflow conditions for the inlet of the second-stage runner, so as to obtain a multi-stage Francis turbine with a rated efficiency higher than 800 m head, good hydraulic stability, and further providing a basis for the scheme of using a single-stage power station with a multi-stage runner Francis turbine for the development of ultra-high head and ultra-large capacity water energy in the western region of China.

[0011] Further, the water flow design parameters of the multi-stage Francis turbine include a first designed axial velocity value of the water flow at the outlet end of the blade camber line and a second designed axial velocity value of the water flow at the inlet end of the second-stage runner;

[0012] The design parameters of the second-stage runner include the designed circumferential velocity at the inlet end of the second-stage runner, the installation angle value at the inlet end of the second-stage runner, and a third radial distance value between the inlet end of the second-stage runner and the central axis.

[0013] Further, the method for calculating and obtaining the installation angle value of the outlet end of the blade camber line includes:

[0014] According to the designed circumferential velocity, the installation angle value at the inlet end of the secondary runner, and the second designed meridional velocity value, calculate the first velocity component in the circumferential direction of the absolute velocity of the water flow at the inlet end of the secondary runner under the condition of no shock at the inlet of the secondary runner;

[0015] According to the second radial distance value, the third radial distance value, and the obtained first velocity component, calculate the second velocity component in the circumferential direction of the absolute velocity of the water flow at the outlet end of the blade camber line under the condition of equal velocity moment;

[0016] According to the first designed meridional velocity value and the obtained second velocity component, calculate the installation angle value at the outlet end of the blade camber line.

[0017] By calculating the installation angle value at the outlet end of the blade camber line through the above method, while ensuring that the inlet of the secondary runner meets the no-shock condition, it also makes the velocity moment of the water flow in the circumferential direction at the outlet of the inter-stage fixed guide vane equal to the velocity moment of the water flow in the circumferential direction at the inlet end of the secondary runner, which can better ensure the uniform distribution of the velocity moment of the water flow at the inlet of the secondary runner and provide better inflow conditions for the inlet of the secondary runner.

[0018] Furthermore, the first velocity component is calculated using the following formula:

[0019]

[0020] where C u1 is the first velocity component; U 1 is the designed circumferential velocity; C m1 is the second designed meridional velocity value; β a is the installation angle value at the inlet end of the secondary runner.

[0021] Furthermore, the second velocity component is calculated using the following formula:

[0022]

[0023] where C u0 is the second velocity component; C u1 is the first velocity component; r a is the third radial distance value; r b is the second radial distance value.

[0024] Furthermore, the installation angle value at the outlet end of the blade camber line is calculated using the following formula:

[0025]

[0026] where is the outlet installation angle value of the blade camber line; C m0 is the first designed axial plane velocity value; C u0 is the second velocity component.

[0027] Furthermore, the obtained inlet installation angle value of the blade camber line is 90 degrees.

[0028] Since the water inlet direction of the second-stage runner of the multi-stage mixed-flow water turbine is normal water inlet, by setting the inlet installation angle value of the blade camber line to 90 degrees, the impact loss at the inlet of the inter-stage stay vanes can be effectively reduced.

[0029] Furthermore, the installation angle value corresponding to any point on the blade camber line is calculated by the following formula:

[0030]

[0031] Where:

[0032]

[0033] In the formula, l is the distance value in the radial direction of the second-stage runner between this point and the inlet end of the blade camber line; β l is the installation angle value corresponding to this point; β 0 is the inlet installation angle value of the blade camber line; l 0 is the distance value in the radial direction of the second-stage runner between the inlet end and the outlet end of the blade camber line; is the outlet installation angle value of the blade camber line; f(l) is the empirical function for calculating the installation angle value of the blade camber line.

[0034] Furthermore, the empirical function for calculating the installation angle value of the blade camber line is expressed as follows:

[0035]

[0036] In the formula, a, b, c, d, and e are all empirical coefficients.

[0037] By adjusting the values of the empirical coefficients a, b, c, d, and e, the spatial shape of the inter-stage stay vanes can be effectively adjusted according to the design requirements.

[0038] Furthermore, the camber line equation of the inter-stage stay vanes is:

[0039]

[0040] Where, is the included angle radian value of the blade camber line; l 0is the distance value in the radial direction of the secondary runner between the inlet end and the outlet end of the blade camber line; l is the distance value in the radial direction of the secondary runner between any point on the blade camber line and its inlet end; r l is the radial distance value between this point and the central axis of the secondary runner; β l is the setting angle value corresponding to this point.

[0041] According to the design method of the inter-stage stay vanes of a multi-stage mixed-flow water turbine provided by the present invention, the present invention also provides a non-transitory readable recording medium for storing one or more programs including a plurality of instructions, characterized in that when the instructions are executed, it will cause the processing circuit to execute the steps in the design method of the inter-stage stay vanes of the multi-stage mixed-flow water turbine provided by the present invention.

[0042] According to the design method of the inter-stage stay vanes of a multi-stage mixed-flow water turbine provided by the present invention, the present invention also provides a design system for the inter-stage stay vanes of a multi-stage mixed-flow water turbine, including a processing circuit and a memory electrically coupled thereto, characterized in that the memory is configured to store at least one program, the program includes a plurality of instructions, the processing circuit runs the program, and the design system for the inter-stage stay vanes of the multi-stage mixed-flow water turbine is used to execute the steps in the design method of the inter-stage stay vanes of the multi-stage mixed-flow water turbine provided by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0044] Figure 1 is a schematic structural diagram of the multi-stage mixed-flow water turbine in Embodiment 1;

[0045] Figure 2 is a flowchart of the design method of the inter-stage stay vanes of the multi-stage mixed-flow water turbine in Embodiment 1;

[0046] Among them, 1 - primary runner, 2 - inter-stage flow passage, 3 - secondary runner, 4 - inter-stage stay vane. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them.

[0048] Embodiment 1:

[0049] As Figure 1As shown in the figure, for the existing flow path sequence of a multi-stage mixed-flow water turbine, the water with high head and large flow rate passes through the power station water intake system to the inlet of the first volute, and after passing through the first runner 1, it drives the second runner 3 through the inter-stage flow path 2, and then the water flow enters the draft tube. The two-stage water turbine dissipates and converts energy in a mixed-flow manner.

[0050] As Figure 1 shown in the figure, in order to solve the problem of uneven flow field generated at the outlet of the first runner of a multi-stage mixed-flow water turbine, in this Embodiment 1, a method of setting an inter-stage fixed guide vane 4 at the outlet of the inter-stage flow path 2 is adopted to optimize and adjust the outlet flow field of the first runner 1, so as to provide good inlet flow conditions for the second runner 3. Since there is a lack of a standardized design method for inter-stage fixed guide vanes in the existing technology, it is necessary to develop a standardized design method for inter-stage fixed guide vanes to optimize and adjust the outlet flow field of the first runner 1 and provide good inlet flow conditions for the second runner 3, which is very necessary for improving the hydraulic performance of multi-stage mixed-flow water turbines.

[0051] As Figure 2 shown in the figure, this Embodiment 1 provides a design method for the inter-stage fixed guide vane of a multi-stage mixed-flow water turbine. Among them, the water inlet direction of the second runner 3 of the multi-stage mixed-flow water turbine is normal water inlet. The design method for the inter-stage fixed guide vane of the multi-stage mixed-flow water turbine includes:

[0052] Obtain the first radial distance value between the inlet end of the blade camber line of the inter-stage fixed guide vane 4 and the central axis of the second runner 3, and the second radial distance value between the outlet end of the blade camber line and the central axis.

[0053] According to the water inlet direction of the second runner 3, obtain the installation angle value of the inlet end of the blade camber line; according to the water flow design parameters of the multi-stage mixed-flow water turbine, the design parameters of the second runner 3, and the obtained second radial distance value, calculate and obtain the installation angle value of the outlet end of the blade camber line.

[0054] According to the obtained first radial distance value, second radial distance value, installation angle value of the inlet end of the blade camber line, and installation angle value of the outlet end, calculate and obtain the installation angle values corresponding to each point on the blade camber line.

[0055] According to the obtained installation angle values corresponding to each point on the blade camber line, and the camber line equation of the inter-stage fixed guide vane 4, determine the spatial shape of the inter-stage fixed guide vane 4.

[0056] By designing the blade camber line of the intermediate stay vane 4 using the design method of the intermediate stay vane of the multi-stage Francis turbine provided in this Embodiment 1, the velocity field distribution at the outlet of the first-stage runner can be effectively adjusted, ensuring a uniform distribution of the water flow velocity moment at the inlet of the second-stage runner 3, providing good inflow conditions for the inlet of the second-stage runner 3, so as to obtain a multi-stage Francis turbine with a rated efficiency higher than 800 m head and good hydraulic stability, and further providing a basis for the scheme of using a single-stage power station with a multi-stage runner Francis turbine for the development of ultra-high head and ultra-large capacity water energy in the western region of China.

[0057] Specifically, in this Embodiment 1, the water flow design parameters of the multi-stage Francis turbine include the first designed axial velocity value of the water flow at the outlet end of the blade camber line and the second designed axial velocity value of the water flow at the inlet end of the second-stage runner 3;

[0058] The design parameters of the second-stage runner 3 include the designed circumferential velocity at the inlet end of the second-stage runner 3, the installation angle value at the inlet end of the second-stage runner 3, and the third radial distance value between the inlet end of the second-stage runner 3 and the central axis.

[0059] Specifically, in this Embodiment 1, the method for calculating the installation angle value at the outlet end of the blade camber line includes:

[0060] According to the designed circumferential velocity, the installation angle value at the inlet end of the second-stage runner 3, and the second designed axial velocity value, calculate the first velocity component in the circumferential direction of the absolute velocity of the water flow at the inlet end of the second-stage runner 3 under the condition of no shock at the inlet of the second-stage runner 3;

[0061] According to the second radial distance value, the third radial distance value, and the obtained first velocity component, calculate the second velocity component in the circumferential direction of the absolute velocity of the water flow at the outlet end of the blade camber line under the condition of equal velocity moment;

[0062] According to the first designed axial velocity value and the obtained second velocity component, calculate the installation angle value at the outlet end of the blade camber line.

[0063] By calculating the installation angle value at the outlet end of the blade camber line through the above method, while the inlet of the second-stage runner 3 meets the condition of no shock, the velocity moment in the circumferential direction of the water flow at the outlet of the intermediate stay vane 4 is equal to the velocity moment in the circumferential direction of the water flow at the inlet end of the second-stage runner 3, which can better ensure a uniform distribution of the water flow velocity moment at the inlet of the second-stage runner 3 and provide better inflow conditions for the inlet of the second-stage runner 3.

[0064] Specifically, in this Embodiment 1, the first velocity component is calculated using the following formula:

[0065]

[0066] Where C u1is the first velocity component; U 1 is the designed peripheral velocity; C m1 is the second designed meridional velocity value; β a is the blade setting angle value at the inlet end of the second-stage runner 3.

[0067] Specifically, in this Embodiment 1, the second velocity component is calculated by the following formula:

[0068]

[0069] where C u0 is the second velocity component; C u1 is the first velocity component; r a is the third radial distance value; r b is the second radial distance value.

[0070] Specifically, in this Embodiment 1, the blade setting angle value at the outlet end of the blade camber line is calculated by the following formula:

[0071]

[0072] where is the blade setting angle value at the outlet end of the blade camber line; C m0 is the first designed meridional velocity value; C u0 is the second velocity component.

[0073] Specifically, in this Embodiment 1, the blade setting angle value at the inlet end of the obtained blade camber line is 90 degrees.

[0074] Since the water inlet direction of the second-stage runner 3 of the multi-stage mixed-flow water turbine is normal water inlet, by setting the blade setting angle value at the inlet end of the blade camber line to 90 degrees, the impact loss at the inlet of the inter-stage stay vane 4 can be effectively reduced.

[0075] Specifically, in this Embodiment 1, the blade setting angle value corresponding to any point on the blade camber line is calculated by the following formula:

[0076]

[0077] where:

[0078]

[0079] In the formula, l is the distance value in the radial direction of the second-stage runner 3 between this point and the inlet end of the blade camber line; β l is the blade setting angle value corresponding to this point; β 0 is the blade setting angle value at the inlet end of the blade camber line; l 0 is the distance value in the radial direction of the second-stage runner 3 between the inlet end and the outlet end of the blade camber line; is the outlet end installation angle value of the blade camber line; f(l) is the empirical function for calculating the installation angle value of the blade camber line.

[0080] Wherein, l 0 That is, the difference between the first radial distance value and the second radial distance value.

[0081] Specifically, in Embodiment 1, the empirical function for calculating the installation angle value of the blade camber line is expressed as follows:

[0082]

[0083] In the formula, a, b, c, d, and e are all empirical coefficients.

[0084] By adjusting the values of the empirical coefficients a, b, c, d, and e, the spatial shape of the inter-stage stationary guide vane 4 can be effectively adjusted according to design requirements.

[0085] Specifically, in Embodiment 1, the camber line equation of the inter-stage stationary guide vane 4 is:

[0086]

[0087] Wherein, is the included angle radian value of the blade camber line; l 0 is the distance value in the radial direction of the secondary runner 3 between the inlet end and the outlet end of the blade camber line; l is the distance value in the radial direction of the secondary runner 3 between any point on the blade camber line and its inlet end; r l is the radial distance value between this point and the central axis of the secondary runner 3; β l is the installation angle value corresponding to this point.

[0088] Embodiment 2:

[0089] According to the design method of the inter-stage stationary guide vane of the multi-stage mixed-flow water turbine provided in Embodiment 1, Embodiment 2 provides a non-transitory readable recording medium for storing one or more programs including a plurality of instructions, characterized in that when the instructions are executed, it will cause the processing circuit to execute the steps in the design method of the inter-stage stationary guide vane of the multi-stage mixed-flow water turbine provided in Embodiment 1.

[0090] Embodiment 3:

[0091] According to the design method of the inter-stage stationary guide vane of the multi-stage mixed-flow water turbine provided in Embodiment 1, Embodiment 2 provides a design system for the inter-stage stationary guide vane of a multi-stage mixed-flow water turbine, including a processing circuit and a memory electrically coupled thereto, characterized in that the memory is configured to store at least one program, the program includes a plurality of instructions, the processing circuit runs the program, and the design system for the inter-stage stationary guide vane of the multi-stage mixed-flow water turbine is used to execute the steps in the design method of the inter-stage stationary guide vane of the multi-stage mixed-flow water turbine provided in Embodiment 1.

[0092] The design method, recording medium and system of the inter-stage stay vanes of the multi-stage Francis turbine provided by the present invention at least have the following technical effects or advantages:

[0093] 1. By designing the blade camber line of the inter-stage stay vane 4 through the design method of the inter-stage stay vanes of the multi-stage Francis turbine provided by the present invention, the velocity field distribution at the outlet of the first-stage runner can be effectively adjusted, ensuring a uniform distribution of the water flow velocity moment at the inlet of the second-stage runner 3, providing good inflow conditions for the inlet of the second-stage runner 3, so as to obtain a multi-stage Francis turbine with a rated efficiency higher than 800 m head, good hydraulic stability, and further providing a basis for the scheme of using a single-stage power station with multi-stage runners for the development of ultra-high head and ultra-large capacity water energy in the western region of China.

[0094] 2. By calculating the outlet end setting angle value of the blade camber line through the above method, while the inlet of the second-stage runner 3 meets the non-impact condition, the velocity moment of the water flow in the circumferential direction at the outlet of the inter-stage stay vane 4 is equal to the velocity moment of the water flow in the circumferential direction at the inlet end of the second-stage runner 3, which can better ensure a uniform distribution of the water flow velocity moment at the inlet of the second-stage runner 3 and provide better inflow conditions for the inlet of the second-stage runner 3.

[0095] 3. Since the water inlet direction of the second-stage runner 3 of the multi-stage Francis turbine is normal water inlet, by setting the inlet end setting angle value of the blade camber line to 90 degrees, the impact loss at the inlet of the inter-stage stay vane 4 can be effectively reduced.

[0096] 4. By adjusting the values of the empirical coefficients a, b, c, d and e, the spatial shape of the inter-stage stay vane 4 can be effectively adjusted according to the design requirements.

[0097] The above are only specific application examples of the present invention, which do not constitute any limitation to the protection scope of the present invention. Any technical solutions formed by equivalent transformation or equivalent substitution fall within the scope of the protection of the present invention.

Claims

1. A method for designing interstage fixed guide vanes of a multi-stage mixed flow turbine, wherein the water inlet direction of the secondary runner of the multi-stage mixed flow turbine is normal water inlet, characterized in that: The design method comprises: Acquire a first radial distance value between an inlet end of a blade bone line of an inter-stage fixed guide vane and a central axis of the secondary runner, and a second radial distance value between an outlet end of the blade bone line and the central axis; According to the water inlet direction of the secondary runner, the inlet end placement angle value of the blade skeleton line is obtained; according to the water flow design parameters of the multi-stage mixed flow turbine, the design parameters of the secondary runner and the obtained second radial distance value, the outlet end placement angle value of the blade skeleton line is calculated; Calculate and obtain the placement angle value corresponding to each point on the blade bone line according to the first radial distance value, the second radial distance value, the inlet end placement angle value and the outlet end placement angle value of the blade bone line; The spatial shape of the inter-stage fixed guide vane is determined according to the obtained placement angle values ​​corresponding to each point on the blade bone line and the bone line equation of the inter-stage fixed guide vane.

2. The method for designing inter-stage fixed guide vanes of a multi-stage mixed flow turbine according to claim 1, characterized in that: The water flow design parameters of the multi-stage mixed flow turbine include a first design axial velocity value of the water flow at the outlet end of the blade skeleton and a second design axial velocity value of the water flow at the inlet end of the secondary runner; The design parameters of the secondary runner include the design circumferential speed of the inlet end of the secondary runner, the placement angle value of the inlet end of the secondary runner, and the third radial distance value between the inlet end of the secondary runner and the central axis.

3. The method for designing inter-stage fixed guide vanes of a multi-stage mixed flow turbine according to claim 2, characterized in that: The method for calculating the outlet end placement angle value of the blade bone line includes: According to the designed circumferential speed, the placement angle value of the inlet end of the secondary runner and the second designed axial speed value, a first velocity component of the absolute velocity of the water flow at the inlet end of the secondary runner in the circumferential direction under the condition of no impact at the inlet of the secondary runner is calculated; According to the second radial distance value, the third radial distance value and the obtained first velocity component, a second velocity component of the absolute velocity of the water flow at the outlet end of the blade bone line in the circumferential direction under the condition of constant velocity moment is calculated; According to the first design axial velocity value and the obtained second velocity component, the outlet end placement angle value of the blade bone line is calculated and obtained.

4. The method for designing inter-stage fixed guide vanes of a multi-stage mixed flow turbine according to claim 3, characterized in that: The first velocity component is calculated using the following formula: Among them, C u1 is the first velocity component; U1 is the designed circumferential velocity; C m1 is the second design axial velocity value; β a The angle value for the inlet end of the secondary runner.

5. The method for designing inter-stage fixed guide vanes of a multi-stage mixed flow turbine according to claim 3, characterized in that: The second velocity component is calculated using the following formula: Among them, C u0 is the second velocity component; C u1 is the first velocity component; r a is the third radial distance value; r b is the second radial distance value.

6. The method for designing inter-stage fixed guide vanes of a multi-stage mixed flow turbine according to claim 3, characterized in that: The outlet angle of the blade bone line is calculated using the following formula: in, C is the angle value of the outlet end of the blade bone line; m0 is the first design axial velocity value; C u0 is the second velocity component.

7. The method for designing inter-stage fixed guide vanes of a multi-stage mixed flow turbine according to claim 1, characterized in that: The obtained placement angle value of the inlet end of the blade bone line is 90 degrees.

8. The method for designing inter-stage fixed guide vanes of a multi-stage mixed flow turbine according to claim 1, characterized in that: The placement angle value corresponding to any point on the blade bone line is calculated using the following formula: in: Wherein, l is the distance between this point and the inlet end of the blade bone line in the radial direction of the secondary runner; β l is the placement angle value corresponding to the point; β0 is the placement angle value of the inlet end of the blade bone line; l0 is the distance value between the inlet end and the outlet end of the blade bone line in the radial direction of the secondary runner; is the placement angle value of the outlet end of the blade bone line; f(l) is the empirical function for calculating the placement angle value of the blade bone line.

9. The method for designing inter-stage fixed guide vanes of a multi-stage mixed flow turbine according to claim 8, characterized in that: The empirical function for calculating the placement angle of the blade bone line is expressed as follows: Where a, b, c, d and e are empirical coefficients.

10. The method for designing inter-stage fixed guide vanes of a multi-stage mixed flow turbine according to claim 1, characterized in that: The skeleton equation of the interstage fixed guide vane is: in, is the radian value of the wrap angle of the blade bone line; l0 is the distance between the inlet end and the outlet end of the blade bone line in the radial direction of the secondary runner; l is the distance between any point on the blade bone line and its inlet end in the radial direction of the secondary runner; r l β is the radial distance between this point and the central axis of the secondary runner; l is the placement angle value corresponding to this point.

11. A non-transitory readable recording medium for storing one or more programs including a plurality of instructions, characterized in that: When the instructions are executed, the processing circuit is caused to execute the steps of the method for designing inter-stage fixed guide vanes of a multi-stage mixed flow turbine according to any one of claims 1-10.

12. A system for designing inter-stage fixed guide vanes of a multi-stage mixed flow turbine, comprising a processing circuit and a memory electrically coupled thereto, characterized in that: The memory configuration stores at least one program, the program includes a plurality of instructions, the processing circuit runs the program, and the multi-stage mixed flow turbine inter-stage fixed guide vane design system is used to execute the steps in the multi-stage mixed flow turbine inter-stage fixed guide vane design method described in any one of claims 1-10.

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