Method for increasing maximum flow of middle stage of compressor based on blade cutting

Abstract

The invention provides a method for increasing the maximum flow of the middle stage of a compressor based on blade cutting. The method comprises the following steps that S1, the expected maximum flow Mm2 of a target compressor computational domain A is obtained; s2, an existing compressor is analyzed through a CFD method, the maximum flow Mkm1 of an existing compressor computational domain B is obtained, the maximum flow Mkm1 of the existing compressor computational domain B is compared with the expected maximum flow Mm2 of the target compressor computational domain A, and whether the ratio of the maximum flow Mkm1 of the existing compressor computational domain B to the expected maximum flow Mm2 of the target compressor computational domain A meets a preset coefficient Lk or not is judged; if yes, the step S8 is carried out; if not, performing the step S3; according to the method, the meridian profile of the middle stage can be kept unchanged, the cutting position of the front edge of the impeller of the middle stage is determined through CFD sub-calculation analysis, the local structure of the compressor is changed, the maximum flow of the model stage is increased, the requirement for scheme changing is met, and meanwhile the unit changing cost is reduced to the maximum extent.

Description

Technical Field

[0001] The present application belongs to the technical field of compressors, and in particular relates to a method for increasing the maximum flow rate of a compressor intermediate stage based on blade cutting. Background Art

[0002] Generally speaking, compressor manufacturers use selection software to reasonably arrange a series of compressor model levels to meet the user's performance requirements. At present, common design methods for compressor model levels include: (1) one-dimensional / quasi-three-dimensional / CFD new model level optimization design, (2) meridian cutting method based on the parent level to achieve pie level design. The characteristic of method 1 is that the obtained model level blade shape and meridian are all brand new designs; the meridian of method 2 is a brand new design. However, under some special conditions, the above design methods cannot fully meet the actual needs.

[0003] For example, a single-shaft three-stage compressor unit has been processed or put into operation on site, and the impeller of the five-stage compressor is installed on the shaft in sequence. At this time, due to process changes or processing and manufacturing problems, the flow rate of the intermediate stage of the compressor needs to be increased. At this time, the most direct way is to change the design scheme and use a compressor model stage with a larger flow coefficient at this stage instead of the existing scheme. The cost of adopting this solution is that at least the rotor and stator parts of the intermediate stage compressor need to be re-produced. In some cases, the shaft and the stator parts of the front and rear stages may need to be re-processed, which means that at least one-fifth of the material processing fee of a unit needs to be increased, and the construction period will be delayed, and the machine tools will be occupied, which may eventually increase the cost of the unit significantly, greatly reducing the company's profitability. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] In order to solve the above problems, the present application provides a method for increasing the maximum flow rate of the intermediate stage of the compressor based on blade cutting, comprising the following steps:

[0006] S1, obtaining the expected maximum flow rate Mm2 of the target compressor calculation domain A;

[0007] S2, using CFD method to analyze the existing compressor, and obtain the maximum flow Mkm1 of the calculation domain B of the existing compressor, and compare the maximum flow Mkm1 of the calculation domain B of the existing compressor with the expected maximum flow Mm2 of the calculation domain A of the target compressor to determine whether the ratio satisfies the preset coefficient Lk; if so, proceed to step S8; if not, proceed to step S3;

[0008] S3, according to the maximum flow Mkm1 of the existing compressor calculation domain B, obtain the maximum flow inlet airflow angle αm1 and the blade installation angle β0 at the maximum flow operating point, and obtain the minimum negative attack angle γmm;

[0009] S4, obtaining a proportional coefficient L required to increase the expected maximum flow rate Mm2 of the target compressor calculation domain A relative to the maximum flow rate Mkm1 of the existing compressor calculation domain B;

[0010] S5, performing parameterized modeling on the existing compressor impeller to obtain a function of the area change A of the blade passage and the blade installation angle β changing with the chord length;

[0011] S6, according to the minimum negative attack angle γ mm , the blade installation angle β and the blade passage cross-sectional area Ah determine the blade leading edge cutting position;

[0012] S7, using CFD method to calculate the maximum flow Mcm2 of the calculation domain B of the compressor blade after cutting, the maximum flow Mcm2 of the calculation domain B of the compressor blade after cutting is compared with the expected maximum flow Mm2 of the calculation domain A of the target compressor, and judging whether the ratio satisfies the preset coefficient Lk; if so, proceed to step S8; if not, proceed to step S6;

[0013] S8, calculating the maximum flow rate of the calculation domain A of the compressor after cutting to determine whether it meets the design requirements, if so, the design ends; if not, proceeding to step S9;

[0014] S9. Optimize the number, thickness and installation angle of the return flow device blades of the compressor after cutting until the design requirements are met.

[0015] Optionally, in S3, the minimum negative angle of attack γ mm =α m1 -β0.

[0016] Optionally, the S6 includes:

[0017] S61. Analyze the CFD calculation results of the maximum flow of the existing compressor to determine the minimum negative attack angle γ that the impeller leading edge can withstand mm ;

[0018] S62, determining the blade leading edge cutting position according to the existing compressor outlet projection area Aht1 and the target compressor outlet projection area Aht2.

[0019] Optionally, the S62 includes:

[0020] S621. The relative airflow angle α at the blade tip can be calculated based on the rotation speed and the required target compressor maximum flow Mm2. m2 ;

[0021] S622. The projection area Aht1 of the existing compressor outlet is expressed as follows:

[0022] Aht1=Ah1*cos(α m1 -β0)-Arm

[0023]

[0024] Where: α m1 - maximum flow inlet airflow angle; β0- blade installation angle in the existing state; γ mm - minimum negative angle of attack;

[0025] S623. When the leading edge of the blade is cut at different relative chord length positions, the target compressor port projection area Aht2 is expressed as follows:

[0026] Aht2(M)=Ah2(M)*cos(α m2 -β m )-Arm

[0027]

[0028] In the formula, α m2 -Relative airflow angle at the blade tip; β m - blade installation angle after cutting at chord length m; γ mm - minimum negative angle of attack;

[0029] S624. The projection area of ​​the nozzle of the existing compressor changes with the change of the cutting position. When Aht2(M2)=L*Aht1 is satisfied, the cutting position of the leading edge of the blade can be determined, and L is the proportionality coefficient.

[0030] Optionally, in step S1 and step S2, the rotation speed of the target compressor and the existing compressor are the same.

[0031] Optionally, between steps S1 and S2, a calculation model needs to be established based on existing compressor geometry data.

[0032] Beneficial Effects

[0033] A method for increasing the maximum flow of the intermediate stage of a compressor based on blade cutting provided in an embodiment of the present invention can keep the meridian profile of the intermediate stage unchanged, determine the cutting position of the leading edge of the intermediate stage impeller through CFD sub-calculation analysis, realize the local structural change of the compressor, increase the maximum flow of the model stage, meet the requirements of the change plan, and minimize the cost of unit change. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flow chart of the present invention;

[0035] Figure 2 It is a structural diagram of the calculation domain A of the present invention;

[0036] Figure 3 It is the flow field distribution diagram of the maximum flow condition of the prior art;

[0037] Figure 4 It is a structural diagram showing the variation of the installation angle and the relative area of ​​the channel of the present invention;

[0038] Figure 5 It is the flow diagram of the calculation domain B after cutting of the present invention;

[0039] Figure 6 This is the flow diagram of the calculation domain A after cutting according to the present invention.

[0040] The reference numerals are as follows:

[0041] 1. Intermediate stage inlet 1; 2. Diffuser outlet 2; 3. Intermediate stage outlet 3. DETAILED DESCRIPTION

[0042] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0043] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0044] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0046] See also Figure 1-6 As shown, according to an embodiment of the present application, a method for increasing the maximum flow of a compressor intermediate stage based on blade cutting is provided, comprising the following steps:

[0047] S1. According to the thermodynamic calculation of the compressor, it can be determined that the maximum flow rate of the intermediate stage of the existing compressor when the operating speed is N is Mm1. Since the existing Mm1 cannot meet the actual operation requirements, it is necessary to increase the maximum flow rate of the existing compressor Mm1 to Mm2 to meet the actual operation requirements. Mm2 is the expected maximum flow rate of the target compressor calculation domain A;

[0048] Among them, Figure 2 As shown, the compressor calculation domain A is the area constructed by all components between the intermediate stage inlet 1 and the intermediate stage outlet 3.

[0049] S2. According to the geometric data of the intermediate stage of the existing compressor, a calculation model is established, and the CFD method is used to analyze the maximum flow Mkm1 of the calculation domain B of the existing compressor when the speed is N. The preset coefficient Lk is set. The preset coefficient Lk is usually set based on the engineer and is not limited here. The maximum flow Mkm1 of the calculation domain B of the existing compressor is compared with the expected maximum flow Mm2 of the calculation domain A of the target compressor. When the ratio is greater than the preset coefficient Lk, it means that the impeller flow of the intermediate stage of the existing compressor meets the design requirements, and step S8 is performed; if it is not greater than, step S3 is performed to continue processing the existing compressor.

[0050] Among them, Figure 2 As shown, the compressor calculation domain B is the area constructed by all components between the intermediate stage inlet 1 and the diffuser outlet 2.

[0051] S3. Compare the maximum flow Mkm1 of the existing compressor calculation domain B with the expected maximum flow Mm2 of the target compressor calculation domain A. When the ratio is not greater than the preset coefficient Lk, analyze the maximum flow Mkm1 of the existing compressor calculation domain B according to the CFD calculation results to obtain the maximum flow inlet airflow angle α at the maximum flow operating point. m1 With the blade installation angle β0, the minimum negative angle of attack γ is obtained mm ;

[0052] Among them, γ mm =α m1 -β0.

[0053] S4. Obtain the proportional coefficient L required to increase the expected maximum flow Mm2 of the target compressor calculation domain A relative to the maximum flow Mkm1 of the existing compressor calculation domain B, where L = Mm2 / Mkm1+Lk-1, and L is the magnification of the target compressor flow relative to the existing compressor. According to the flow characteristics of the gas inside the compressor, the projection area Aht of the internal port area Ah of the compressor calculation domain A along the flow direction at the same speed is the main reason affecting the maximum flow. Therefore, the design goal is to increase Aht2 of the target compressor to L*Aht1, where Aht2 is the port projection area of ​​the target compressor, and Aht1 is the port projection area of ​​the existing compressor.

[0054] S5. Parametric modeling of the blade profile of the existing compressor impeller is performed to obtain the curve of the area A of the blade passage changing with the chord length and the curve of the blade installation angle β changing with the chord length. The area A can be expressed as a function of the relative chord length M of the blade, A=A(M), and the blade installation angle β can also be expressed as a function of the relative chord length M of the blade, β=β(M), where the blade installation angle of the existing solution is β0;

[0055] S6, according to the minimum negative angle of attack γ mm , the blade installation angle β0 and the blade channel cross-sectional area Ah determine the blade leading edge cutting position, where the opening area Ah = min(A(M)), that is, Ah is also a function of the relative chord length M, which can be expressed as Ah = Ah(M). At this time, Ah is the minimum area position in the area A of the compressor blade channel; the process of determining the blade leading edge cutting position is:

[0056] S61. Analyze the CFD calculation results of the maximum flow of the existing compressor to determine whether flow separation occurs. If flow separation occurs, it is necessary to determine the relative area Ar occupied by the flow separation. At this time, determine γ m is the minimum negative angle of attack that the impeller leading edge can withstand at speed N; if flow separation does not occur, Ar=0;

[0057] S62, determining the blade leading edge cutting position according to the existing compressor outlet projection area Aht1 and the target compressor outlet projection area Aht2;

[0058] The S62 includes:

[0059] S621. The relative airflow angle α at the blade tip can be calculated based on the rotation speed and the required target compressor maximum flow Mm2. m2 ;

[0060] S622. The projection area Aht1 of the existing compressor outlet is expressed as follows:

[0061] Aht1=Ah1*cos(α m1 -β0)-Arm

[0062]

[0063] Where: α m1 - maximum flow inlet airflow angle; β0- blade installation angle in the existing state; γ mm - minimum negative angle of attack;

[0064] S623. When the leading edge of the blade is cut at different relative chord length positions, the target compressor port projection area Aht2 is expressed as follows:

[0065] Aht2(M)=Ah2(M)*cos(α m2 -β m )-Arm

[0066]

[0067] In the formula, α m2 -Relative airflow angle at the blade tip; β m - blade installation angle after cutting at chord length m; γ mm - minimum negative angle of attack;

[0068] Among them, γ m Calculated using CFD analysis;

[0069] According to the attached Figure 3 It can be seen that the area occupied by the vortex state in the left figure is the Ar area, which accounts for about 10%; the area occupied by the dark black in the right figure is the Ar area, which accounts for about 10%.

[0070] S624, the projection area of ​​the existing compressor port changes with the change of the cutting position. When Aht2(M2)=L*Aht1 is satisfied, M2 is the cutting position of the blade front edge, and L is the proportional coefficient. After the cutting position is determined, the blade can be cut.

[0071] S7, using CFD method to calculate the maximum flow Mcm2 of the calculation domain B of the compressor blade after cutting, and compare the maximum flow Mcm2 of the calculation domain B of the compressor blade after cutting with the expected maximum flow Mm2 of the calculation domain A of the target compressor. When the ratio is greater than the preset coefficient Lk, proceed to step S8; if less than, proceed to step S6, fine-tune the cutting position, and re-cut;

[0072] S8, calculating the maximum flow rate of the calculation domain A of the compressor after cutting, that is, the area constructed by all components from the intermediate stage inlet 1 to the intermediate stage outlet 3, and judging whether the maximum flow rate of the calculation domain A of the compressor after cutting meets the design requirements, if so, the design ends; if not, proceeding to step S9;

[0073] S9. Optimize the number, thickness and installation angle of the return flow device blades of the compressor after cutting until the design requirements are met.

[0074] Example 1

[0075] The maximum flow rate of the intermediate stage of the existing compressor when the speed is N is Mm1. According to actual needs, the expected maximum flow rate of the target compressor calculation domain A is Mm2, where Mm2=Mm1*1.2. CFD analysis is performed on the intermediate stage of the compressor of the existing scheme. The calculation domain B is the area constructed by all components between the intermediate stage inlet 1 and the diffuser outlet 2. The maximum flow rate Mkm1 of the calculation domain B is calculated. According to the preset coefficient determined by the engineer as Lk=1.20, Mkm1 / Mm2=1.03 is calculated, 1.03≤1.2, which does not meet the flow requirement. The maximum flow rate Mkm1 of the calculation domain B of the existing compressor is analyzed based on the CFD calculation results, and the negative attack angle γ is determined at the 95% blade height section of the calculation domain B. m = -10 degrees. Calculate the proportional coefficient L = Mm2 / Mkm1 + Lk-1 = 1.17, then Aht2 = 1.17*Aht1. Parametric modeling is performed on the intermediate stage impeller of the existing scheme to determine the change curve of the area A of the blade channel and the installation angle β. The change curve is shown in the attached figure. Figure 4 shown.

[0076] According to the negative angle of attack γ m , blade installation angle β and the change of the port area Ah determine the leading edge cutting position. The CFD calculation results of the maximum flow condition of the existing compressor intermediate stage are analyzed. Flow separation occurs at the maximum flow point, Ar = 10%, so γ m is the minimum negative angle of attack of this blade type. The flow separation is shown in the attached figure. Figure 3 shown.

[0077] The relative airflow angle α at the blade tip can be calculated based on the rotation speed N and the required maximum flow rate Mm2. m2 =47.7°. According to step S622 and step S623, the existing compressor port projection area Aht1 and the target compressor port projection area Aht2 are calculated respectively, where Aht2 = Aht2(M), which is a function of M. When Aht2(M2) = 1.17*Aht1 is satisfied, the position of the cutting front edge can be determined. Figure 4 As shown in the middle scheme, 15% of the relative chord length was removed.

[0078] The target solution and the existing solution are analyzed by CFD method. The calculation domain B is from stage inlet 1 to diffuser outlet 2. The calculation results are shown in the attached figure. Figure 5 As shown, Mkm2 / Mm2=1.17, which basically meets the requirement of ≥1.17, and the whole-stage CFD analysis is performed. The whole-stage CFD analysis performance cannot meet the requirements, and the return flow blades need to be optimized.

[0079] Such as possession 5 and Figure 6 As shown in the figure, after optimizing the return flow blades, the performance of the target solution is compared with the existing solution. The maximum flow of the target solution is increased by 20%, which meets the design requirements. According to the calculation, the processing cost of the target solution is less than 5% of the total processing cost of the unit.

[0080] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application. The above are only preferred implementations of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present application, and these improvements and variations should also be regarded as the protection scope of the present application.

Claims

1. A method for increasing the maximum flow rate of the intermediate stage of a compressor based on blade cutting, It is characterized in that The following steps are involved: S1, obtaining the expected maximum flow rate Mm2 of the target compressor calculation domain A; S2, using CFD method to analyze the existing compressor, and obtain the maximum flow Mkm1 of the calculation domain B of the existing compressor, and compare the maximum flow Mkm1 of the calculation domain B of the existing compressor with the expected maximum flow Mm2 of the calculation domain A of the target compressor to determine whether the ratio satisfies the preset coefficient Lk; if so, proceed to step S8; if not, proceed to step S3; S3, according to the existing compressor calculation domain B maximum flow Mkm1, obtain the maximum flow inlet airflow angle α at the maximum flow operating point m1 Angle β with blade 0 , and get the minimum negative angle of attack γ mm ; S4, obtaining a proportional coefficient L required to increase the expected maximum flow rate Mm2 of the target compressor calculation domain A relative to the maximum flow rate Mkm1 of the existing compressor calculation domain B; S5. Perform parameterized modeling on the existing compressor impeller to obtain a function of the area A of the blade passage and the blade installation angle β varying with the chord length; S6, according to the minimum negative attack angle γ mm , the blade installation angle β and the blade passage cross-sectional area Ah determine the blade leading edge cutting position; S7, using CFD method to calculate the maximum flow Mcm2 of the calculation domain B of the compressor blade after cutting, the maximum flow Mcm2 of the calculation domain B of the compressor blade after cutting is compared with the expected maximum flow Mm2 of the calculation domain A of the target compressor, and judging whether the ratio satisfies the preset coefficient Lk; if so, proceed to step S8; if not, proceed to step S6; S8, calculating the maximum flow rate of the calculation domain A of the compressor after cutting to determine whether it meets the design requirements, if so, the design ends; if not, proceeding to step S9; S9. Optimize the number, thickness and installation angle of the return flow device blades of the compressor after cutting until the design requirements are met.

2. The method for increasing the maximum flow rate of the intermediate stage of the compressor based on blade cutting according to claim 1, It is characterized in that In S3, the minimum negative angle of attack γ mm =α m1 -β 0 .

3. The method for increasing the maximum flow rate of the intermediate stage of the compressor based on blade cutting according to claim 1, It is characterized in that The S6 includes: S61. Analyze the CFD calculation results of the maximum flow of the existing compressor to determine the minimum negative attack angle γ that the impeller leading edge can withstand mm ; S62, determining the blade leading edge cutting position according to the existing compressor outlet projection area Aht1 and the target compressor outlet projection area Aht2.

4. The method for increasing the maximum flow rate of the intermediate stage of the compressor based on blade cutting according to claim 3, It is characterized in that The S62 includes: S621. The relative airflow angle α at the blade tip can be calculated based on the rotation speed and the required target compressor maximum flow Mm2. m2 ; S622. The projection area Aht1 of the existing compressor outlet is expressed as follows: Aht1=Ah1*cos(α m1 -b 0 )-Arm Where: α m1 - Maximum flow inlet airflow angle; β 0 - blade installation angle in the existing state; γ mm - minimum negative angle of attack; S623. When the leading edge of the blade is cut at different relative chord length positions, the target compressor port projection area Aht2 is expressed as follows: Aht2(M)=Ah2(M)*cos(α m2 -b m )-Arm In the formula, α m2 -Relative airflow angle at the blade tip; β m - blade installation angle after cutting at chord length m; γ mm - minimum negative angle of attack; S624. The projection area of ​​the nozzle of the existing compressor changes with the change of the cutting position. When Aht2(M2)=L*Aht1 is satisfied, the cutting position of the leading edge of the blade can be determined, and L is the proportionality coefficient.

5. The method for increasing the maximum flow rate of the intermediate stage of the compressor based on blade cutting according to claim 1, It is characterized in that In step S1 and step S2, the rotation speeds of the target compressor and the existing compressor are the same.

6. The method for increasing the maximum flow rate of the intermediate stage of the compressor based on blade cutting according to claim 1, It is characterized in that Between steps S1 and S2, a calculation model needs to be established based on existing compressor geometry data.

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