A Digital Design Method for High-Load Fans / Compressors

Abstract

The present invention discloses a digital design method for high-load fans / compressors, comprising: defining the operating parameters of the fan / compressor, calculating the specific speed, and determining the hub ratio. Calculating the hub diameter based on the hub ratio and the outer diameter of the impeller, and obtaining the axial velocity of the airflow in combination with the volume flow rate. Calculating the diameter, circumferential velocity, and airflow twist rate of the mid-span section of the impeller, and determining the airflow angle and turning angle through the velocity triangle. Selecting any span section, defining the span ratio factor, calculating its diameter, circumferential velocity, and airflow twist rate, determining the blade solidity, pitch, and chord length, and finally obtaining the blade geometric angle. Repeating the calculation of the parameters of different sections to complete the design of the impeller. At the same time, after designing the stator of the fan / compressor, the overall design of the fan / compressor is completed. The method of the present invention forms a digital and process-based design specification, greatly shortening the design cycle of the fan / compressor and reducing the R & D cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of machinery, and particularly relates to a digital design method for high-load fans / compressors. Background Art

[0002] Fans / compressors are important components of the cooling system of air-cooled engines. The cold air generated by the fans / compressors accumulates in the air pressure chamber, and a certain air pressure chamber pressure is established. Different air volumes are distributed according to the channel resistances of various components such as the cylinder head, cylinder block, oil cooler, and intercooler to ensure that each component can be reliably cooled. The selection and design quality of the fans / compressors directly affect the quality of the cooling system of air-cooled diesel engines, and then affect the reliability and economy of air-cooled diesel engines. Under the condition that the power consumed by driving the fans / compressors is equal, the air supply pressure of the fans / compressors of air-cooled diesel engines is required to be higher than that of water-cooled diesel engines. To increase the pressure coefficient, most fans / compressors choose to set static blades to increase the pressure, which further increases the design complexity. In recent years, with the improvement of diesel engine performance, the requirements for the cooling system have also been increasing day by day. A fast and accurate design method for high-load fans / compressors is particularly important.

[0003] For the design of high-load fans / compressors, traditional design methods mostly adopt empirical design, that is, by adjusting the geometric structure parameters of existing prototypes to create multiple design schemes, and then performing performance tests to screen the best scheme. However, given the numerous geometric structure parameters of fans / compressors and their complex influence on performance, it is difficult to achieve the optimal design only by experience, and at the same time, it also leads to a long R & D cycle and high R & D costs. Summary of the Invention

[0004] The purpose of the present invention is to provide a digital design method for high-load fans / compressors aiming at the technical defects existing in the prior art. By analyzing the working conditions, performance targets, and structural requirements of fans / compressors, under given conditions such as flow rate and pressure, the optimal matching of the diameter, hub ratio, and working speed of fans / compressors is determined, and then the blade profiles of the moving and static impellers are determined to realize the design of the fans / compressors of air-cooled engines.

[0005] To achieve the above purpose, the present invention provides a digital design method for high-load fans / compressors, including:

[0006] Specify the volume flow rate Q, rated speed n, total pressure P0, design efficiency η of the fan / compressor, and density ρ of the working medium; calculate the specific speed n according to the volume flow rate Q, rated speed n, and total pressure P0 s ;

[0007] According to the specific speed n s , determine the hub ratio ν, and the selection range of the hub ratio ν is:

[0008]

[0009] Among them, the fan / compressor includes a rotating impeller and a stationary impeller, and the rotating impeller and the stationary impeller have the same hub diameter D h and outer diameter D t ;

[0010] According to the hub ratio ν and the outer diameter D of the rotating impeller t , calculate the hub diameter D h ;

[0011] According to the outer diameter D of the rotating impeller t , hub diameter D h and volume flow rate Q, calculate the axial air velocity c z ;

[0012] According to the outer diameter D of the rotating impeller t and hub diameter D h , calculate the diameter D of the middle blade height section of the rotating impeller midspan ;

[0013] According to the diameter D of the middle blade height section of the rotating impeller midspan calculate the circumferential velocity u of the middle blade height section of the rotating impeller midspan ;

[0014] According to the design efficiency η of the fan / compressor, total pressure P0, density ρ of the working medium, circumferential velocity u of the middle blade height section of the rotating impeller midspan , calculate the air flow twist velocity Δc of the middle blade height section of the rotating impeller u,midspan ;

[0015] Calculate the inlet relative air flow angle β 1,midspan , outlet relative air flow angle β 2,midspan and air flow turning angle Δβ midspan of the middle blade height section of the rotating impeller according to the velocity triangle;

[0016] Select any blade height section of the rotating impeller for design, define the blade height ratio factor as ξ, calculate the diameter D of any blade height section, and the circumferential velocity u of any blade height section of the rotating impeller;

[0017] According to the design efficiency η of the fan / compressor, total pressure P0, density ρ of the working medium, circumferential velocity u of any blade height section of the rotating impeller, calculate the air flow twist velocity Δc of any blade height section of the rotating impeller u ;

[0018] Calculate the inlet relative air flow angle β1, outlet relative air flow angle β2 and air flow turning angle Δβ of any blade height section of the rotating impeller according to the velocity triangle;

[0019] Calculate the rated turning angle Δβ of any blade height section of the impeller * , the rated relative outlet air flow angle

[0020] According to the rated turning angle Δβ of any blade height section of the impeller * , the rated relative outlet air flow angle Use the rated characteristic curve of the cascade to select the blade pitch τ of any blade height section;

[0021] According to the hub ratio ν, select the number of blades z of the impeller;

[0022] According to the diameter D and the number of blades z of any blade height section of the impeller, calculate the pitch t of any blade height section;

[0023] According to the blade pitch τ and the pitch t of any blade height section of the impeller, calculate the chord length b of the blade of any blade height section of the impeller;

[0024] Select the rated incidence angle i of any blade height section of the impeller * , according to the rated incidence angle i * , the chord length b of the blade, the rated turning angle Δβ * , the relative outlet air flow angle β2, the pitch t, calculate the blade profile turning angle θ and the rated outlet air flow lag angle δ of any blade height section of the impeller * ;

[0025] According to the relative inlet air flow angle β1, the relative outlet air flow angle β2, the rated incidence angle i of any blade height section of the impeller * , the rated outlet air flow lag angle δ * , calculate the inlet blade geometric angle β 1A , the outlet blade geometric angle β 2A ;

[0026] Select different blade height sections of the impeller, repeat the calculation to obtain the relevant parameters of all blade height sections of the impeller, and complete the design of the impeller; at the same time, after designing the stator of the fan / compressor, complete the overall design of the fan / compressor.

[0027] Preferably, the specific speed n s The formula expression of is:

[0028]

[0029] Preferably, the hub diameter D h The formula expression of is:

[0030] D h = ν × D t

[0031] The axial air flow velocity cz The formula expression is:

[0032]

[0033] The diameter D of the middle blade height section of the impeller midspan The formula expression is:

[0034] D midspan =(D h +D t ) / 2

[0035] The circumferential velocity u of the middle blade height section of the impeller midspan The formula expression is:

[0036]

[0037] Preferably, the air flow twist velocity Δc of the middle blade height section of the impeller u,midspan The formula expression is:

[0038]

[0039] Calculate the inlet relative air flow angle β 1,midspan , outlet relative air flow angle β 2,midspan and air flow turning angle Δβ midspan of the middle blade height section of the impeller according to the velocity triangle. The formula expressions include:

[0040]

[0041] Δβ midspan =β 2,midspan -β 1,midspan

[0042] Select any blade height section of the impeller for design. Define the blade height ratio factor as ξ. The formula expressions for calculating the diameter D of any blade height section and the circumferential velocity u of any blade height section of the impeller include:

[0043] D = D h +(D t -D h )ξ

[0044]

[0045] Preferably, the air flow twist velocity Δc of any blade height section of the impeller u The formula expression is:

[0046]

[0047] The formula expressions for calculating the inlet relative air flow angle β1, the outlet relative air flow angle β2, and the air flow turning angle Δβ at any blade height section of the impeller according to the velocity triangle include:

[0048]

[0049] Δβ = β2 - β1

[0050] Calculating the rated turning angle Δβ of any blade height section of the impeller * and the rated outlet relative air flow angle The formula expressions include:

[0051] Δβ * = 0.8Δβ midspan

[0052]

[0053] Preferably, according to the rated turning angle Δβ of any blade height section of the impeller * and the rated outlet relative air flow angle The formula expression for selecting the blade pitch τ of any blade height section using the rated characteristic curve of the cascade is:

[0054]

[0055] Where

[0056]

[0057] Preferably, the formula expression for selecting the number of blades z of the impeller according to the hub ratio ν is:

[0058]

[0059] According to the diameter D of any blade height section of the impeller and the number of blades z, the formula expression for calculating the pitch t of any blade height section is:

[0060]

[0061] According to the blade pitch τ and the pitch t of any blade height section of the impeller, the formula expression for calculating the blade chord length b of any blade height section is:

[0062] b = τ × t.

[0063] Preferably, the formula expressions for calculating the blade profile turning angle θ and the rated outlet air flow lag angle δ * of any blade height section of the impeller include:

[0064]

[0065] where j = 0.3663 - 0.002β2;

[0066] Calculate the inlet blade geometric angle β 1A and the outlet blade geometric angle β 2A for any blade height section. The formula expressions include:

[0067] β 1A = β1 + i *

[0068] β 2A = β2 + δ * .

[0069] Preferably, the stationary impeller of the fan / compressor is selected as a pre-stationary impeller.

[0070] Preferably, the process of designing the stationary impeller of the fan / compressor includes:

[0071] Given that the inlet air flow angle α0 = 90° for any blade height section of the stationary impeller, calculate the tangential velocity c 1u at the outlet of the pre-stationary impeller for any blade height section according to the diameter D, total pressure P0, and working medium density ρ of any blade height section;

[0072] The formula expression is:

[0073]

[0074] where the value range of n1 is -0.5 to -0.6, and the angular velocity When the diameter D = D midspan of the middle blade height section of the stationary impeller is selected, c 1u = c 1u,midspan ;

[0075] Calculate the outlet air flow angle α1 of the stationary impeller for any blade height section; the formula expression is:

[0076]

[0077] When the middle blade height section of the stationary impeller is selected,

[0078] Replace the variable relative air flow angles β 1,midspan at the inlet and β 2,midspan at the outlet of the middle blade height section of the moving impeller with the air flow angles α 0,midspan = 90° at the inlet and α 1,midspan at the outlet of the middle blade height section of the pre-stationary impeller, and calculate the air flow turning angle Δα midspan :

[0079] Δα midspan = α 1,midspan-90°

[0080] Replace the variable moving impeller middle blade high air flow turning angle Δβ midspan , the rated turning angle Δβ of any blade height section * , the rated outlet relative air flow angle Outlet relative air flow angle β2, inlet relative air flow angle β1, inlet blade geometric angle β 1A , outlet blade geometric angle β 2A , with the relevant variables of the stationary impeller: the front stationary impeller middle blade high air flow turning angle Δα midspan , the rated turning angle Δα of any blade height section * , the rated outlet relative air flow angle Outlet relative air flow angle α1, inlet air flow angle α0, inlet blade geometric angle β 1A , outlet blade geometric angle β 2A , to obtain the calculation formula applicable to the design of the stationary impeller;

[0081] Select different blade heights of the front stationary impeller, and calculate the relevant parameters of all blade height sections of the front stationary impeller according to the replaced variables and the calculation formula applicable to the design of the stationary impeller, and complete the design of the front stationary impeller of the fan / compressor.

[0082] Compared with the prior art, the present invention has the following advantages and technical effects:

[0083] The high-load fan / compressor digital design method of the present invention uses theoretical formulas for calculation, avoiding a large number of trial-and-error attempts required for empirical calculation in the traditional design method, and can ensure that the designed fan / compressor is an optimal solution in principle.

[0084] The high-load fan / compressor digital design method of the present invention forms a digital and process-based design specification, greatly shortening the design cycle of the fan / compressor and reducing the R & D cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] The drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0086] Figure 1 is a schematic flow chart of the method of the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0087] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will refer to the drawings and combine the embodiments to detail this application.

[0088] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. And although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0089] As Figure 1 shown, in this embodiment, a digital design method for a high-load fan / compressor is provided, including the following steps:

[0090] (1) Given the volume flow rate Q, rated speed n, total pressure P0, fan / compressor design efficiency η, and working medium density ρ of the fan / compressor; calculate the specific speed n s , and the calculation formula is:

[0091]

[0092] (2) The fan / compressor includes a rotating impeller and a stationary impeller, and the rotating impeller and the stationary impeller have the same hub diameter D h and outer diameter D t . According to the specific speed n s , select a suitable hub ratio ν, and the selection range is:

[0093]

[0094] (3) Given the outer diameter D t of the rotating impeller, calculate the hub diameter D t according to the hub ratio ν and the outer diameter D h of the rotating impeller, and the calculation formula is:

[0095] D h = ν×D t (3)

[0096] (4) According to the outer diameter D t of the rotating impeller, the hub diameter D h , and the volume flow rate Q, calculate the axial air velocity c z , and the calculation formula is:

[0097]

[0098] (5) According to the outer diameter D t of the rotating impeller, the hub diameter D h , calculate the diameter D midspan of the middle blade height section of the rotating impeller, and the calculation formula is:

[0099] D midspan =(D h + D t ) / 2(5)

[0100] Calculate the circumferential velocity u of the middle blade height section of the impeller midspan , and the calculation formula is:

[0101]

[0102] (6) According to the fan / compressor design efficiency η, total pressure P0, working medium density ρ, and circumferential velocity u of the middle blade height section of the impeller midspan , calculate the airflow twist velocity Δc of the middle blade height section of the impeller u,midspan , and the calculation formula is:

[0103]

[0104] (7) Calculate the inlet relative airflow angle β, outlet relative airflow angle β, and airflow turning angle Δβ of the middle blade height section of the impeller according to the velocity triangle 1,midspan and outlet relative airflow angle β 2,midspan as well as the airflow turning angle Δβ midspan :

[0105]

[0106] Δβ midspan = β 2,midspan - β 1,midspan (10)

[0107] (8) Select any blade height section of the impeller for design. If its blade height ratio factor is ξ, then the calculation formula for the diameter D of any blade height section is:

[0108] D = D h + (D t - D h )ξ(11)

[0109] Calculate the circumferential velocity u of any blade height section of the impeller, and the calculation formula is:

[0110]

[0111] (9) According to the fan / compressor design efficiency η, total pressure P0, working medium density ρ, and circumferential velocity u of any blade height section of the impeller, calculate the airflow twist velocity Δc of any blade height section of the impeller u , and the calculation formula is:

[0112]

[0113] (10) Calculate the inlet relative airflow angle β1, outlet relative airflow angle β2, and airflow turning angle Δβ of any blade height section of the impeller according to the velocity triangle:

[0114]

[0115] Δβ = β2 - β1(16)

[0116] (11) Calculate the rated turning angle Δβ of any blade height section of the impeller * and the rated relative outlet air flow angle The calculation formula is:

[0117] Δβ * = 0.8Δβ midspan (17)

[0118]

[0119] (12) According to the rated turning angle Δβ of any blade height section of the impeller * and the rated relative outlet air flow angle Use the rated characteristic curve of the cascade to select the blade pitch τ of any blade height section. The formula is as follows:

[0120]

[0121] Where

[0122]

[0123] (13) According to the value of the hub ratio ν, select the number of blades z of the impeller. The calculation formula is:

[0124]

[0125] (14) According to the diameter D and the number of blades z of any blade height section of the impeller, calculate the pitch t of any blade height section. The calculation formula is:

[0126]

[0127] (15) According to the blade pitch τ and the pitch t of any blade height section of the impeller, calculate the blade chord length b of any blade height section of the impeller. The calculation formula is:

[0128] b = τ × t(22)

[0129] (16) Select the rated incidence angle i of any blade height section of the impeller * , generally between -5 and 5°. According to the rated incidence angle i * , the blade chord length b, the rated turning angle Δβ * , the outlet relative air flow angle β2, the pitch t, calculate the blade profile turning angle θ and the rated outlet air flow lag angle δ of any blade height section of the impeller * , the calculation formula is:

[0130]

[0131] Where, j = 0.3663 - 0.002β2

[0132] (17) According to the inlet relative air flow angle β1, outlet relative air flow angle β2 of any blade height section of the impeller, and the rated incidence angle i * , and the rated outlet air flow lag angle δ * , calculate the inlet blade geometric angle β 1A and outlet blade geometric angle β 2A of any blade height section. The calculation formula is as follows:

[0133] β 1A = β1 + i * (25)

[0134] β 2A = β2 + δ * (26)

[0135] (18) Select different blade height sections of the impeller, repeat steps (8) to (17) to calculate the relevant parameters of all blade height sections of the impeller, and complete the design of the impeller.

[0136] (19) Design the stationary impeller of the fan / compressor. To increase the load of the fan / compressor, a pre-stationary impeller is selected. The specific design steps are as follows:

[0137] Ⅰ) It is known that the inlet air flow angle α0 of any blade height section of the pre-stationary impeller is 90°. According to the diameter D of any blade height section, total pressure P0, and working medium density ρ of the pre-stationary impeller, calculate the tangential velocity c 1u at the outlet of any blade height section of the pre-stationary impeller. The calculation formula is as follows:

[0138]

[0139] Among them, n1 generally takes values from -0.5 to -0.6, and the angular velocity When selecting the middle blade height section of the stationary impeller with D = D midspan , c 1u = c 1u,midspan ;

[0140] Ⅱ) Calculate the outlet air flow angle α1 of any blade height section of the pre-stationary impeller. The calculation formula is as follows:

[0141]

[0142] When selecting the middle blade height section of the stationary impeller,

[0143] Ⅲ) Replace the variables in step (7): the inlet relative air flow angle β 1,midspan and outlet relative air flow angle β 2,midspan of the middle blade height section of the impeller with the inlet air flow angle α 0,midspan = 90° and outlet air flow angle α of the middle blade height section of the pre-stationary impeller1,midspan , according to Equation (10), the airflow turning angle Δα at the middle blade height section of the front stator impeller can be obtained midspan :

[0144] Δα midspan = α 1,midspan -90°(29)

[0145] Ⅳ) Replace the variables in steps (11) to (17): the airflow turning angle Δβ at the middle blade height of the rotor impeller midspan , the rated turning angle Δβ at any blade height section * , the rated outlet relative airflow angle the outlet relative airflow angle β2, the inlet relative airflow angle β1, the inlet blade geometric angle β 1A , the outlet blade geometric angle β 2A , with the relevant variables of the front stator impeller: the airflow turning angle Δα at the middle blade height of the front stator impeller midspan , the rated turning angle Δα at any blade height section * , the rated outlet relative airflow angle the outlet relative airflow angle α1, the inlet airflow angle α0, the inlet blade geometric angle β 1A , the outlet blade geometric angle β 2A , then the formula applicable to the design of the front stator impeller can be obtained. Select different blade heights of the front stator impeller, and repeat steps (11) to (17) with the replaced variables to calculate the relevant parameters of all blade height sections of the front stator impeller, and complete the design of the fan / compressor front stator impeller.

[0146] The following takes the design of the fan / compressor of a certain type of air-cooled diesel engine as an example for illustration:

[0147] (1) Given the volume flow rate Q = 3.876m 3 / s, the rated speed n = 6045r / min, the total pressure P0 = 5400Pa, the design efficiency η of the fan / compressor = 0.8, and the working medium density ρ = 1.29kg / m 3 . Calculate the specific speed n s = 27.93 according to Equation (1);

[0148] (2) Given the specific speed n s , select the hub ratio ν = 0.554 according to Equation (2);

[0149] (3) Given the outer diameter D of the rotor impeller t = 388mm, calculate the hub diameter D h = 215mm according to Equation (3);

[0150] (4) Calculate the airflow axial velocity c z = 56.8m / s according to Equation (4);

[0151] Calculate the diameter D of the middle blade height section of the impeller according to Equation (5). midspan = 0.3137 m, calculate the circumferential velocity u according to Equation (6). midspan = 99.29 m / s;

[0152] Calculate the air flow twist velocity Δc of the middle blade height section of the impeller according to Equation (7). u,midspan = 57.29 m / s;

[0153] Calculate the relative air flow angles β at the inlet and outlet of the middle blade height section of the impeller according to Equations (8), (9), and (10). 1,midspan = 30.70°, β 2,midspan = 56.12°, and the air flow turning angle Δβ midspan = 26°;

[0154] Select the blade root and blade tip sections for design, and the blade height ratio factor is ξ h = 0, ξ t = 1; calculate the diameters D h , D t ; calculate the circumferential velocity u h = 72.71 m / s, u t = 131.19 m / s;

[0155] Calculate the air flow twist velocity Δc of each section of the impeller according to Equation (13). u,h = 48.38 m / s, Δc u,t = 37.35 m / s;

[0156] Calculate the relative air flow angles β at the inlet and outlet of each section of the impeller according to Equations (14), (15), and (16). 1,h = 37.99°, β 2,h = 46.81°, β 1,t = 23.41°, β 2,t = 37.8°, and the air flow turning angle Δβ h = 10°, Δβ t = 14°;

[0157] Calculate the rated turning angle Δβ of the impeller according to Equations (17) and (18). * = 20.8, the rated outlet relative air flow angle of each section

[0158] Determine the blade pitch τ of each section of the impeller according to Equation (19). h = 0.67, τ midspan = 1.07, τ t = 1.47;

[0159] (13) According to Equation (20), select the number of impeller blades z = 11;

[0160] (14) Calculate the pitch t according to Equation (21) h = 61.96 mm, t midspan = 86.385 mm, t t = 110.81 mm;

[0161] (15) Calculate the chord length b of the impeller blades according to Equation (22) h = 90.80 mm, b midspan = 82.285 mm, b t = 90.80 mm;

[0162] (16) Select the rated incidence angle Calculate the rated outlet flow lag angle according to Equation (23) and Equation (24)

[0163] (17) Calculate the geometric angles β of the inlet and outlet blades of each section according to Equation (25) and Equation (26) 1A 、β 2A , and the calculation results of the impeller parameters are summarized in Table 1 as follows:

[0164] Table 1

[0165]

[0166]

[0167] (18) Design the stationary impeller of the fan / compressor:

[0168] Ⅰ) Select the fan / compressor configuration with a stationary impeller in front of the impeller, and calculate the tangential velocity c at the outlet of each blade height section of the stationary impeller in front according to Equation (27) 1u,h = -50.51 m / s, c 1u,midspan = -51.71 m / s, c 1u,t = -52.89 m / s;

[0169] Ⅱ) Calculate the outlet flow angle α of the stationary impeller in front according to Equation (28) 1,h = 143.75°, α 1,midspan = 138.46°, α 1,t = 132.96°;

[0170] Ⅲ) Calculate the flow turning angle Δα of the middle blade height section of the stationary impeller in front according to Equation (29) midspan = 48°;

[0171] Ⅳ) Replace the variables in steps (11) to (17): the high gas flow turning angle Δβ of the middle blade of the moving impeller midspan , the rated turning angle Δβ of any blade height section * , the rated relative gas flow angle at the outlet the relative gas flow angle β2 at the outlet, the relative gas flow angle β1 at the inlet, the geometric blade angle β at the inlet 1A , the geometric blade angle β at the outlet 2A , with the relevant variables of the front stationary impeller: the high gas flow turning angle Δα of the middle blade of the front stationary impeller midspan , the rated turning angle Δα of any blade height section * , the rated relative gas flow angle at the outlet the relative gas flow angle α1 at the outlet, the gas flow angle α0 at the inlet, the geometric blade angle β at the inlet 1A , the geometric blade angle β at the outlet 2A , then the formula applicable to the design of the front stationary impeller can be obtained. Select different blade heights of the front stationary impeller, and repeat steps (11) to (17) with the replaced variables to calculate the relevant parameters of all blade height sections of the front stationary impeller, completing the design of the front stationary impeller of the fan / compressor. The calculation results of the parameters of the front stationary impeller are shown in Table 2:

[0172] Table 2

[0173]

[0174] The high-load fan / compressor digital design method disclosed in this embodiment improves the design efficiency of the fan / compressor of the air-cooled machine on the premise of ensuring the high load and high total pressure requirements of the fan / compressor of the air-cooled machine. By analyzing the working conditions, performance objectives, and structural requirements of the fan / compressor, under given conditions such as flow rate and pressure, the optimal matching of the diameter, hub ratio, and working speed of the fan / compressor is determined, and then the blade profiles of the moving and stationary impellers are determined, realizing the digital design of the fan / compressor of the air-cooled machine. Applying this method to the digital design of the fan / compressor of the air-cooled machine can ensure that the designed fan / compressor is an optimal solution, and can significantly reduce the design time and lower the R & D cost.

[0175] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A digital design method for high-load fans / compressors, characterized in that, Including: Given the volume flow rate Q, rated speed n, total pressure P0, design efficiency η of the fan / compressor, and density ρ of the working medium; Calculate the specific speed $n_s$ based on the volume flow rate $Q$, the rated speed $n$, and the total pressure $P_0$. s ; According to the specific speed n s , determine the hub ratio ν, and the selection range of the hub ratio ν is as follows: Wherein, the fan / compressor includes a rotating impeller and a stationary impeller, and the rotating impeller and the stationary impeller have the same hub diameter D h and outer diameter D t ; According to the hub ratio ν and the outer diameter D of the impeller t , calculate the hub diameter D h ; According to the outer diameter D of the impeller wheel t , the hub diameter D h and the volume flow rate Q, calculate the axial velocity c of the air flow z ; According to the outer diameter D of the impeller t and the hub diameter D h , calculate the diameter D of the middle blade height section of the impeller midspan ; According to the middle blade height section diameter D of the impeller midspan calculate the circumferential velocity u of the middle blade height section of the impeller midspan ; According to the design efficiency η of the fan / compressor, the total pressure P0, the density ρ of the working medium, and the circumferential velocity u of the middle blade height section of the impeller midspan , calculate the airflow twist velocity Δc of the middle blade height section of the impeller u,midspan ; Calculate the inlet relative air flow angle β 1,midspan and the outlet relative air flow angle β 2,midspan at the middle blade height section of the impeller, as well as the air flow turning angle Δβ midspan ; Select any blade height section of the impeller for design, define the blade height ratio factor as ξ, calculate the diameter D of any blade height section, and the circumferential speed u of any blade height section of the impeller; Calculate the airflow swirl velocity Δc at any blade height section of the impeller according to the design efficiency η of the fan / compressor, the total pressure P0, the density ρ of the working medium, and the circumferential velocity u at any blade height section of the impeller u ; Calculate the inlet relative airflow angle β1, outlet relative airflow angle β2, and airflow turning angle Δβ of any blade height section of the impeller according to the velocity triangle; Calculate the rated turning angle Δβ of any blade height section of the impeller and the rated relative flow angle at the outlet * and the rated relative flow angle at the outlet According to the rated turning angle Δβ of any blade height section of the impeller wheel * , the rated relative air flow angle at the outlet select the blade pitch τ of any blade height section by using the rated characteristic curve of the cascade; Select the number of blades z of the impeller according to the hub ratio ν; Calculate the pitch t of any blade height section according to the diameter D of any blade height section of the impeller and the number of blades z; Calculate the chord length b of any blade height section of the impeller according to the blade solidity τ and pitch t of any blade height section of the impeller; Select the rated incidence angle i of any blade height section of the moving impeller * , according to the rated incidence angle i * , blade chord length b, rated turning angle Δβ * , relative outlet airflow angle β2, pitch t, calculate the blade profile turning angle θ and rated outlet airflow lag angle δ of any blade height section of the moving impeller * ; According to the inlet relative air flow angle β1, outlet relative air flow angle β2, rated incidence angle i of any blade height section of the impeller * , rated outlet air flow lag angle δ * , calculate the inlet blade geometric angle β 1A and outlet blade geometric angle β 2A ; Select different blade height sections of the impeller, repeat the calculation to obtain the relevant parameters of all blade height sections of the impeller, and complete the design of the impeller; at the same time, after designing the stationary impeller of the fan / compressor, complete the overall design of the fan / compressor.

2. The method according to claim 1, wherein The specific speed n s has the following formula expression:

3. The method according to claim 1, wherein The hub diameter D h has the following formula expression: D h = ν × D t The axial velocity c of the air flow z has the following formula expression: The intermediate blade height section diameter D of the impeller midspan The formula expression is: D midspan = (D h + D t ) / 2 The circumferential velocity u of the middle blade height section of the impeller midspan is expressed by the formula as follows:

4. The method according to claim 1, wherein The circumferential velocity difference Δc of the flow in the mid-height section of the rotating impeller u,midspan is expressed by the following formula: Calculate the inlet relative air flow angle β 1,midspan , outlet relative air flow angle β 2,midspan and air flow turning angle Δβ midspan The formula expressions are as follows: Δβ midspan = β 2,midspan - β 1,midspan The formula expressions for selecting any blade height section of the impeller for design, defining the blade height ratio factor as ξ, calculating the diameter D of any blade height section, and the circumferential speed u of any blade height section of the impeller include: D = D h +(D t -D h )ξ 5. The method according to claim 1, wherein The air flow swirl velocity Δc at any blade height section of the moving impeller u has the following formula expression: The formula expressions for calculating the inlet relative airflow angle β1, outlet relative airflow angle β2, and airflow turning angle Δβ of any blade height section of the impeller according to the velocity triangle include: Δβ = β2 - β1 Calculating the rated turning angle Δβ of any blade height section of the impeller * and the rated relative outlet air flow angle The formula expressions include: Δβ * = 0.8Δβ midspan 6. The method according to claim 1, wherein According to the rated turning angle Δβ of any blade height section of the impeller wheel * , the rated relative air flow angle at the outlet The formula expression for selecting the blade pitch τ of any blade height section by using the rated characteristic curve of the cascade is as follows: where 7. The method according to claim 1, wherein The formula expression for selecting the number of blades z of the impeller according to the hub ratio ν is: The formula expression for calculating the pitch t of any blade height section according to the diameter D of any blade height section of the impeller and the number of blades z is: The formula expression for calculating the chord length b of any blade height section of the impeller according to the blade solidity τ and pitch t of any blade height section of the impeller is: b = τ × t.

8. The method according to claim 1, wherein Calculate the blade profile turning angle θ and the rated outlet air flow lag angle δ at any blade height section of the impeller * The formula expressions for which include: where j = 0.3663 - 0.002β2; Calculate the inlet blade geometric angle β of any blade height section 1A and the outlet blade geometric angle β 2A The formula expressions are as follows: β 1A ＝β1+i * β 2A = β2 + δ * .

9. The method according to claim 1, wherein The stationary impeller of the fan / compressor selects a pre-stationary impeller.

10. The method according to claim 1, wherein The process of designing the stationary impeller of the fan / compressor includes: Given that the inlet air flow angle α0 of any blade height section of the stationary impeller is 90°, the tangential velocity c at the outlet of any blade height section of the pre-stage stationary impeller is calculated based on the diameter D, total pressure P0, and working medium density ρ of any blade height section. 1u ; The formula expression is: Among them, the value range of n1 is -0.5 to -0.6, and the angular velocity When the middle blade height section D = D of the stationary impeller is selected midspan At this time, c 1u = c 1u,midspan ; Calculate the outlet airflow angle α1 of any blade height section of the stationary impeller; the formula expression is: When selecting the middle blade height section of the stationary impeller, Replace the inlet relative flow angle β 1,midspan and the outlet relative flow angle β 2,midspan of the intermediate blade height section of the variable moving impeller with the inlet flow angle α 0,midspan = 90° and the outlet flow angle α 1,midspan of the intermediate blade height section of the pre-stage stationary impeller, and calculate the flow angle deviation Δα midspan : Δα midspan = α 1,midspan -90° Replace the variable moving impeller intermediate blade high gas flow turning angle Δβ midspan , any blade height section rated turning angle Δβ * , rated outlet relative gas flow angle outlet relative gas flow angle β2, inlet relative gas flow angle β1, inlet blade geometric angle β 1A , outlet blade geometric angle β 2A , with the corresponding variables of the stationary impeller: the front stationary impeller intermediate blade high gas flow turning angle Δα midspan , any blade height section rated turning angle Δα * , rated outlet relative gas flow angle outlet relative gas flow angle α1, inlet gas flow angle α0, inlet blade geometric angle β 1A , outlet blade geometric angle β 2A , to obtain the calculation formula applicable to the design of the stationary impeller; Select different blade heights of the pre-stationary impeller, and calculate the relevant parameters of all blade height sections of the pre-stationary impeller according to the replaced variables and the calculation formulas applicable to the design of the stationary impeller to complete the design of the pre-stationary impeller of the fan / compressor.

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