KR20190048671A - Compact and simplifying design method of diffuser for mixed flow pump, diffuser designed by the method and mixed flow pump having the same - Google Patents

Abstract

Provided is a method for designing a diffuser. The method for designing a diffuser comprises the following steps: determining an objective function by considering a shape of the diffuser in order to simplify the design of a diffuser which is connected to an impeller to discharge a fluid introduced through the impeller to the outside, and to compactly design the diffuser; determining a design variable affecting a value of the objective function; and deriving a shape of the diffuser by using the design variable.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffuser design method for a compact and simple multistage pump, a diffuser designed thereby, and a multistage pump having the diffuser design.

The present invention relates to a method for designing a diffuser of a compact and simplified multistage pump, a diffuser designed thereby and a multistage pump having the diffuser.

Pumps are used in the transportation of fluids in general households and industries, and in various plant industries (such as chemical, nuclear power, power plants and offshore plants). There are various pumps depending on the requirements.

A sludge pump is a fluid machine that uses a centrifugal force generated by an impeller that is rotated by receiving power from the outside to perform a pumping action of fluid, that is, a transportation action of fluid or a pressure.

In this case, the diffuser is installed at the rear end of the impeller to perform the function of diffusing the fluid or changing the velocity and pressure. Therefore, the design of the impeller and the diffuser is the most basic work in centrifugal and fluid pump design.

The conventional multistage pump has many design variables and the design of the diffuser has been difficult, so that it has been difficult to accurately design many design parameters, and therefore, there is a limit to satisfy the accurate head.

An embodiment of the present invention provides a diffuser design method for a multistage pump that can simplify the design while maintaining a high efficiency and a high degree of lift, and is easy to manufacture and compact and can reduce the maintenance cost, a diffuser designed thereby, and a multistage pump having the diffuser do.

According to an aspect of the present invention, there is provided a method for designing a diffuser, which simplifies a design of a diffuser that is connected to an impeller and discharges a fluid introduced through the impeller to the outside, and a compact design of a diffuser, A design variable determining step of influencing a value of the objective function and a shape deriving step of a diffuser using the design variable.

In this case, in consideration of the shape of the diffuser, the specific speed in the design parameter and objective function determination step is determined by the flow quantity Q, the head Ht and the rotational speed N, which are design specifications, It can be within Ns.

In this case, in consideration of the shape of the diffuser, the objective function in the objective function determination step may be a head Ht and efficiency (t) for analyzing the performance of the diffuser.

At this time, the design parameter determination step of the diffuser may include: a diffuser meridional surface design parameter determination step of expressing a shape of a blade of the diffuser to generate a three-dimensional shape of the diffuser; And determining the diffuser wing angle design variable expressing the wing angle of the diffuser.

At this time, in the meridional surface design parameter determination step of the diffuser, the meridional surface design parameters of the diffuser are such that the meridional surface design parameters of the diffuser are the radius (R3_h) of the hub portion at the diffuser inlet, the blade width (b3) at the front end of the diffuser wing, The radius of the hub portion at the diffuser outlet (R4_h), the blade width at the rear end of the diffuser wing (b4), the inclined angle at the rear end of the diffuser wing (4), the angle between the diffuser inlet and the diffuser outlet An axial length Z4, and an axial length Z3 between the hub portion of the impeller outlet and the hub portion of the diffuser inlet.

At this time, in the blade design parameter determination step of the diffuser, the blade development design parameter includes a TE start point, a product of a sweep angle of the diffuser and a mean radius (r_theta_total), an entrance angle (beta1_ (h, m, s) ), The exit angle (beta2_ (h, m, s)), the length of the entrance rectilinear section (beta_LE_ (h, m, s) (H, m, s) of the exit portion and an inclination angle (d_theta (h, s)) inclined in the rotation direction, an adjustment point (CP_LE_ can do.

At this time, the first design point (x) and the second design point (y) of the entrance portion are determined at the diffuser meridian plane in the shape deriving step of the diffuser by using the design variables, and at the first design point and the second design point And can be linearly connected from the meridional plane to the outlet of the diffuser.

At this time, the first design point may be located at the hub side diffuser inlet at x% of the length of the meridional plane, and the second design point may be at y% of the length of the meridian plane at the shroud side diffuser inlet.

Here, x may be 30% and y may be 10%.

According to another aspect of the present invention, there is provided a diffuser designed by the above-described method of designing a diffuser.

According to another aspect of the present invention, there is provided a diffuser, And a casing having an impeller installed inside the diffuser, an inlet formed to suck the fluid in front of the impeller, and a discharge port configured to discharge the sucked fluid to the outer periphery of the impeller.

The design method of the diffuser for a domestic pump according to an embodiment of the present invention, the diffuser designed by the present invention, and the hydrodynamic pump having the same, can simplify the design while maintaining the existing high efficiency and high lifting, .

1 is a flowchart illustrating a method of designing a diffuser according to an embodiment of the present invention.
2 is a cross-sectional view of a hydrodynamic pump having a diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention.
3 is a perspective view illustrating a diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention.
4 is a cross-sectional view illustrating a meridional plane of a diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention.
5 is a cross-sectional view illustrating a comparison of the meridional planes of a diffuser and a reference diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention.
FIG. 6 is a schematic view showing blade design parameters of a diffuser in a method of designing a diffuser according to an embodiment of the present invention. FIG.
7 is a perspective view illustrating a diffuser and a reference diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention.
FIG. 8 is a graph according to a numerical analysis result of the head of a diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention.
9 is a graph illustrating a numerical analysis result of the efficiency of the diffuser designed by the method of designing the diffuser according to the embodiment of the present invention.
10 is a perspective view illustrating a numerical analysis boundary condition and a lattice system of a diffuser designed by a method of designing a diffuser according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

In this specification, the terms "comprises" or "having" and the like refer to the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, where a section such as a layer, a film, an area, a plate, or the like is referred to as being "on" another section, it includes not only the case where it is "directly on" another part but also the case where there is another part in between. On the contrary, where a section such as a layer, a film, an area, a plate, etc. is referred to as being "under" another section, this includes not only the case where the section is "directly underneath"

1 is a flowchart illustrating a method of designing a diffuser according to an embodiment of the present invention.

Referring to FIG. 1, a method for designing a diffuser according to an embodiment of the present invention includes an objective function determination step (S10) in consideration of a shape of a diffuser, a design parameter determination step (S20) And deriving the shape of the diffuser using a design parameter (S30).

Accordingly, by designing the diffuser 5 according to the embodiment of the present invention, it is possible to simplify the design while maintaining the high efficiency and the high temperature, so that the manufacture can be easily performed and the maintenance cost can be reduced.

2 is a cross-sectional view of a hydrodynamic pump having a diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention.

2, the suction port 3 of the multistage pump is defined forward from the drive shaft 30 of the motor, and the drive shaft 30 side of the motor is defined downstream from the suction port 3 of the multistage pump Explain.

Referring to FIG. 2, the hydrodynamic pump 1 according to an embodiment of the present invention may include a diffuser 5 designed by a method of designing a diffuser. At this time, a centrifugal and sump pump impeller 10, which sucks and discharges the fluid while rotating at a high speed between the suction port 3 and the discharge port (not shown), may be incorporated into the sludge pump 1.

2, in an embodiment of the present invention, the impeller 10 and the diffuser 5 of the extruder pump may be installed in the casing 2. [ In addition, a suction port 3 through which the fluid is sucked is formed in the front center portion of the extruder pump impeller 10, and the sucked fluid is discharged to the outer circumferential portion of the extruder pump impeller 10 in the radial direction.

At this time, in one embodiment of the present invention, the diffuser 5 may be formed with a discharge port so that the fluid introduced through the impeller 10 is discharged to the outside.

Referring to FIG. 2, in one embodiment of the present invention, the impeller 10 may include an impeller hub 11, an impeller blade 13, and an impeller shroud 15. In an embodiment of the present invention, the impeller hub 11 is a part coupled to the motor drive shaft 30 to receive the rotational force of the motor, and may be a material having high rigidity suitable for high-speed rotation.

At this time, the impeller hub 11 may be formed to have a conical shape in which the cross-sectional area is reduced while moving backward. That is, the hub 11 is formed at the center of the impeller 10, and the driving shaft 30 is coupled to the impeller hub, so that the rotational force of the motor can be transmitted to the impeller 10.

2, a plurality of impeller blades 13 may be radially formed on the circumferential surface of the impeller hub 11 as a center. At this time, the plurality of impeller blades 13 may be composed of five, but the embodiment of the present invention is not limited thereto.

The impeller shroud 15 may be formed to surround the entire outer end of the impeller blade 13 while connecting the outer ends of the plurality of impeller blades 13 disposed in the impeller hub 11. This impeller shroud 15 can be connected to each of the impeller blades 13.

3 is a perspective view illustrating a diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention.

Referring to FIG. 3, the diffuser 5 designed according to the design method of the diffuser according to an embodiment of the present invention may be formed in a columnar shape. The diffuser 5 may also include a diffuser hub 7, a diffuser wing 6 and a diffuser shroud 9.

2, in the embodiment of the present invention, the diffuser hub 7 is installed at the rear end of the impeller 10 to diffuse the fluid when discharging the fluid discharged through the impeller to the outside, Can be converted.

At this time, the diffuser hub 7 may be formed so as to have an arc shape having a curved sectional area while moving backward. That is, the hub 11 is formed in the circumferential portion of the diffuser 5, and the impeller 10 is coupled to the hub, and the fluid discharged through the impeller can be transferred to the diffuser hub 7.

3, a plurality of diffuser blades 6 may be radially formed on the circumferential surface of the diffuser hub 7 as a center. At this time, the plurality of diffuser blades 6 may be composed of seven, but the embodiment of the present invention is not limited thereto.

The diffuser shroud 9 may also be formed to enclose the entire outer end while connecting the outer ends of a plurality of diffuser vanes 6 disposed in the diffuser hub 7. [ This diffuser shroud 9 can be connected to each diffuser wing 6.

Referring to FIG. 1, a method of designing a diffuser according to an embodiment of the present invention may include an objective function determination step (S10) in consideration of the shape of a diffuser. At this time, considering the shape of the diffuser, it is possible to determine the flow specifications (Q), heading (Ht) and number of rotations (N), which are design specifications required when designing the diffuser (5) have.

The flow specifications Q, the head Ht and the number of revolutions N are specifications required for designing the diffuser 5. At this time, the flow rate Q and the head Ht are basically satisfactory specifications while the impeller 10 rotates, and the rotation speed N can be determined according to the diameter of the motor drive shaft 30.

On the other hand, the diffuser 5 can be designed so that the efficiency is high at a given flow rate and head. That is, since the diffuser 5 is designed to maintain high efficiency and high lifting, the impeller blade shape and meridional surface shape can be changed and are not limited to any impeller.

Therefore, in order to analyze the performance of the diffuser according to the design variables considering the shape of the diffuser, the objective function for the design purpose should be defined. At this time, the objective function for the design purpose may be the pump efficiency and the flushing which indicate the performance of the diffuser.

Meanwhile, in one embodiment of the present invention, the type of the pump can be determined by determining the specific speed in the design parameter selection and the objective function determination step S10 in consideration of the shape of the diffuser. In this case, The type of pump may be a sour pump.

At this time, Specific Speed (Ns) is defined by the following equation.

……(식 1)

... ... (Equation 1)

Where Q = flow rate, Ht = heading, and N = number of revolutions.

Given the flow specifications Q, head Ht, and number of revolutions N, which are the design specifications of the extruder pump impeller 10, the specific speed can be determined using Equation 1. [

At this time, the non-velocity is used as an index to distinguish the kind of the pump, and it is possible to distinguish the kind of the pump having the velocity. In an embodiment of the present invention, the smaller the specific speed, the more distinction is made between a centrifugal pump and a non-accelerated axial pump.

That is, the specific speed of the centrifugal pump is determined in the range of 150 to 600 Ns, the specific speed of the extruder pump is determined in the range of 400 to 1200 Ns, and the axial flow pump can be determined in the range of 1200 Ns or more.

However, in the present invention, the design parameters of the diffuser according to the specific speed are limited to the constant flow tendency, and the centrifugal and axial flow pumps will be omitted.

At this time, the non-velocity is a dimensionless number, and the kind of the pump can be represented by the relational expression of the flow rate Q, the head Ht, and the number of rotations N. Thus, in one embodiment of the present invention, And thus the specific velocity may be 400 to 1200 Ns.

In the embodiment of the present invention, the design parameter determination step S20, which affects the objective function value, is a step of determining a meridional surface design parameter of a diffuser expressing a wing shape to generate a three-dimensional shape of the diffuser 5 And a wing angle design variable determining step of expressing the wing angle of the diffuser. At this time, the meridian plane is a part of the cross section of the diffuser including the center line of the hub 11.

4 is a cross-sectional view illustrating a meridional plane of a diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention. 5 is a cross-sectional view illustrating a meridional plane of a diffuser and a reference diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention.

Referring to FIG. 4, in an embodiment of the present invention, the diffuser is connected to the rear end of the impeller, so that the design of the meridional surface of the diffuser may be correlated with the impeller meridian.

On the other hand, in the determination of the meridional surface design parameters of the diffuser, the meridional surface design parameters of the diffuser are the radius (R3_h) of the hub portion at the diffuser inlet, the blade width (b3) at the front of the diffuser wing, (R4_h) of the hub portion at the diffuser outlet, a blade width (b4) at the rear end of the diffuser wing, a tilted angle (? 4) at the rear end of the diffuser wing, an axial length (Z4) between the diffuser inlet and the diffuser outlet, And the axial length Z3 between the hub portion of the diffuser inlet and the hub portion of the diffuser inlet.

That is, according to the method of designing the diffuser according to the embodiment of the present invention, the diffuser 5 is designed by selecting eight design parameters of the diffuser, thereby simplifying the design while maintaining high efficiency and high lifting, can do.

5, when the first design point x and the second design point y of the inlet portion are determined in the diffuser meridian plane in the shape deriving step S30 of the diffuser by using design variables in the embodiment of the present invention, It can be connected straight to the part. In this case, the first design point may be x% position based on the length of the meridian surface at the hub side diffuser inlet, and the second design point may be y% position based on the length of the meridian surface at the shroud side diffuser inlet. Where x can be 30% and y can be 10%. At this time, if eight design variables are determined, the first design point and the second design point can be determined.

In this case, eight design parameters are the meridional design parameters of the diffuser, the radius (R3_h) of the hub at the diffuser inlet, the blade width (b3) at the front of the diffuser wing, the tilted angle The radius (R4_h) of the hub portion, the blade width (b4) at the rear end of the diffuser wing, the inclined angle (4) at the rear end of the diffuser wing, the axial length Z4 between the diffuser inlet and the diffuser outlet, And the axial length Z3 between the hub portions of the diffuser inlet.

The method of designing the diffuser according to an embodiment of the present invention may use a straight line to connect the first design point and the second design point of the diffuser to the outlet side of the hub side and the shroud side diffuser respectively. In other words, diffuser meridian is connected by two straight lines in hub and shroud, unlike impeller meridian.

Referring to FIG. 6, in the blade angle design variable determining step for expressing the blade angle of the diffuser, the blade development design variable of the diffuser is determined by the exit start point TE start point, the sweep angle of the diffuser and the averaged radius r_theta_total (h, m, s (H, m, s), the exit angle beta2_ (h, m, s), the length of the inlet straight line portion% beta_LE_ (h, m, s), and the length of the exit straight line portion% beta_TE_ (H, m, s) of the entrance portion and the adjustment point% CP_TE_ (h, m, s) of the exit portion include the angle d_theta (H, m, s), the exit angle beta2_ (h, m, s), the length of the inlet straight line portion% beta_LE_ (h, m, s), and the length of the exit straight line portion% beta_TE_ , s) and an angle d_theta (h, s) inclined at the exit in the rotational direction.

In the present invention, the diffuser blade development design variables are defined in accordance with the curve control method, namely, the Bezier curve control method and the classical curve control method. Here, the Bezier curve control method has an advantage that the blade length can be controlled because the sweep angle of the blade is included as a variable.

Here, referring to FIG. 6, the parameter h is a diffuser hub, m is a diffuser mid, and s is a diffuser shroud.

7 is a perspective view illustrating a diffuser and a reference diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention.

5 and 7, in the embodiment of the present invention, the meridional surface design parameters of the conventional diffuser are the radius (R3_h) of the hub portion at the diffuser inlet portion, the blade width (b3) at the front end of the diffuser wing, The angle at the outermost point of the diffuser (4), the radius at the exit of the diffuser (4), the angle at the outermost point of the diffuser (5) at the diffuser outlet, the tilted angle (5) at the diffuser outlet, the hub-side diffuser inlet adjustment point (% CP1h), the hub- (% CP2h,% CP3h), the hub side diffuser outlet adjustment point (% CP4h), the angle (? 1h) of the hub curve at the diffuser inlet with the horizontal line, the angle? 4h formed by the hub curve at the diffuser exit with the horizontal line, (% CP1s) at the diffuser inlet at the wood side, the first and second diffuser depths at the shroud side (% CP2s,% CP3s), the diffuser exit adjustment point (% CP4s) at the shroud side, the angle (θ1s) the shroud curve of the diffuser inlet with the horizontal line, and the shroud curve at the diffuser exit, And an angle [theta] 4s formed between them.

In other words, the conventional diffuser meridian design parameters are 24 design parameters, and the shape of the diffuser 5a designed through the diffuser meridian design parameters may be similar to the shape of the jar as shown in FIG. 7 (a). In this case, the diffuser 5 designed by the diffuser designing method according to the embodiment of the present invention may be formed into a cylindrical shape as shown in FIG. 7 (b)

Referring to FIG. 8, numerical simulation conditions are generated by the eight design parameters that affect the head and the efficiency of the diffuser in an embodiment of the present invention. At this time, the working fluid passing through the extruder pump diffuser 5 is made of water at 25 degrees. Also, the boundary condition of the inlet is the atmospheric pressure in the uniform state, and the outlet condition is the mass flow rate.

The method of designing a diffuser according to an embodiment of the present invention may further include a step (S40) of determining whether the derived diffuser design is valid based on the shape of the derived diffuser and the result of numerical analysis of the reference diffuser .

Table 1 compares the objective function obtained by numerical analysis of the diffuser designed by the reference diffuser and the design method of the diffuser according to the embodiment of the present invention.

Head (m) efficiency(%) The reference diffuser 5a 13.64 90.57 The derived diffuser (5) 13.46 88.48

As a result of the design, the objective function of the diffuser designed by the design method of the diffuser according to the embodiment of the present invention is 13.45 and the efficiency is calculated as 88.48%. Therefore, it can be confirmed that the reference diffuser 5a maintains the head and hull even when compared with the high-efficiency model.

8 is a graph showing the head of a hydrodynamic pump having a diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention. 9 is a graph showing the efficiency of a hydrodynamic pump having a diffuser designed according to a method of designing a diffuser according to an embodiment of the present invention.

Referring to FIGS. 8 and 9, it can be seen that the head and the efficiency of the hydrodynamic pump having the diffuser designed by the diffuser designing method according to the embodiment of the present invention are similar to those of the reference diffuser. At this time, Q / Qd is the flow rate ratio, which means the flow rate of the reference model to the design flow rate.

10 is a perspective view illustrating a numerical analysis boundary condition and a lattice system of a diffuser designed by a method of designing a diffuser according to an embodiment of the present invention.

At this time, in the step of comparing by numerical analysis, the design target value of the multistage pump can be obtained through analysis of a shear stress transport (SST) turbulent flow model based on K-ω using the commercial code ANSYS CFX-16.0 of the finite volume corporation ANSYS .

At this time, ANSYS Blade-Gen and Turbo-Grid can be used for blade shape definition and grid generation, respectively.

Referring to FIG. 10, a 3D geometry of the impeller was generated using the ANSYS CFX-BladeGen program, and a structured grid was created using the ANSYS CFX TurboGrid, a fluid mechanical grid generation program, for the generated blade shape.

The number of blades of the impeller is 5 and the number of blades of the diffuser is 7. However, since the impeller and diffuser used for the numerical analysis have the same blade shape, the period of the impeller and the diffuser Numerical analysis was performed only for the wing area.

The governing equations used in the numerical analysis are discretized by the finite volume method and the high resolution scheme with the second order or higher accuracy is used as the discretization method.

The shear stress transport k-ω model, which is suitable for predicting the flow separation, was used as the turbulence model used for the analysis of the turbulent flow.

At the boundary condition, the atmospheric pressure was uniformly applied to the inlet of the impeller and the outlet of the diffuser, and the mass flow rate was applied to the outlet, and the impeller rotation speed was 2400 rpm. At this time, water was used as the working fluid.

The design method of the diffuser for a domestic pump according to an embodiment of the present invention, the diffuser designed by the present invention, and the hydrodynamic pump having the same, can simplify the design while maintaining the existing high efficiency and high lifting, .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

1: Centrifugal and extruder pump 2: Casing
3: Suction port 5: Drive shaft of the motor
10: impeller 30: diffuser
32: diffuser wing 34: diffuser hub
36: diffuser shroud x: 1st design point
y: 2nd design point

Claims (11)

A diffuser design method for simplifying a design of a diffuser connected to an impeller and discharging a fluid introduced through the impeller to the outside, and for designing a diffuser compactly,
Determining an objective function in consideration of the shape of the diffuser;
A design variable determining step of influencing a value of the objective function;
And deriving the shape of the diffuser using the design variables. The method according to claim 1,
The non-velocity is determined by the flow quantity (Q), the heading (Ht), and the number of rotations (N), which are design specifications, in the design variables and objective function determining step in consideration of the shape of the diffuser, and the specific velocity is within 400 to 1200 Ns Method of designing an in - diffuser. 3. The method of claim 2,
Wherein the objective function in the objective function determination step considering the shape of the diffuser is a head Ht and efficiency (t) for analyzing the performance of the diffuser. The method of claim 3,
The design variable determining step of the diffuser
A diffuser meridional surface design parameter determination step of expressing a shape of a blade of the diffuser to generate a three-dimensional shape of the diffuser;
And determining the design variables of the diffuser wing to express the wing angle of the diffuser. 5. The method of claim 4,
In the meridional surface design parameter determination step of the diffuser, the meridional surface design parameters of the diffuser are such that the meridional surface design parameters of the diffuser are the radius (R3_h) of the hub part at the diffuser inlet, the blade width (b3) at the front end of the diffuser wing, The radius of the hub portion at the diffuser outlet (R4_h), the blade width at the rear end of the diffuser wing (b4), the inclined angle at the rear end of the diffuser wing (4), the axial length between the diffuser inlet and the diffuser outlet (Z4), the axial length (Z3) between the hub portion of the impeller outlet and the hub portion of the diffuser inlet. 5. The method of claim 4,
In the wing angle design variable determining step of the diffuser, the vane development design parameter includes an exit start point (TE start point), a product of the sweep angle of the diffuser and the averaged radius (r_theta_total), the entrance angle (beta1_ (h, m, s) (H, m, s)), the length of the exit rectilinear section (% beta_TE_ (h, m, s) (H, m, s) including an adjustment point (CP_LE_ (h, m, s)) of the exit portion and an inclination angle d_theta Design method. The method according to claim 1,
The first design point (x) and the second design point (y) of the entrance portion are determined in the diffuser meridian plane in the shape deriving step of the diffuser using the design variables, and at the first design point and the second design point, A method of designing a diffuser in a straight line from the meridian to the exit of 8. The method of claim 7,
Wherein the first design point is at the hub side diffuser inlet at x% of the length of the meridian face and the second design point is at y% of the length of the meridian at the shroud side diffuser inlet. 9. The method of claim 8,
Wherein x is 30% and y is 10%. A diffuser designed by a method of designing a diffuser according to any one of claims 1 to 9. A diffuser according to claim 10;
An impeller installed inside the diffuser and
And a casing having an inlet formed to suck a fluid in front of the impeller and a discharge port configured to discharge the sucked fluid to an outer periphery of the impeller.

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