One-dimensional optimization method and system for carbon dioxide centrifugal compressor based on optimal specific speed

Abstract

The present invention discloses a one-dimensional optimization method and system for a carbon dioxide centrifugal compressor based on an optimal specific speed, determines the optimal stage number and speed combination, and then determines the stage average isentropic enthalpy increase Δh of the compressor according to the total stage number j and the operating speed r of the compressor. s,m Average specific speed N s,m ; 2) According to the average isentropic enthalpy increase Δh of the compressor stage s,m Average specific speed N s,m The enthalpy increase of each stage is adjusted on the basis of the average enthalpy increase of each stage, so that the speed ratio of each stage of the compressor is in the optimal range, and the one-dimensional optimization of the carbon dioxide centrifugal compressor based on the optimal speed ratio is completed. This method and system can effectively prevent the speed ratio of each stage of the compressor from deviating from the optimal range.

Description

Technical Field

[0001] The invention belongs to the technical field of supercritical carbon dioxide cycle power generation, and relates to a one-dimensional optimization method and system for a carbon dioxide centrifugal compressor based on an optimal specific speed. Background Art

[0002] With the development of power generation technology in recent years, studies have shown that the use of supercritical carbon dioxide instead of water vapor as a circulating working fluid in power generating units has the advantages of high circulation efficiency, compact equipment structure, and small initial infrastructure investment within a certain power range. Therefore, the supercritical carbon dioxide circulation power generation system is a very promising power generation method.

[0003] For the current supercritical carbon dioxide cycle power generation technology, since the carbon dioxide compressor operates near the critical point of the working fluid, and the efficiency and safety of its operation directly determine the efficiency of the carbon dioxide cycle power generation unit.

[0004] The equal diameter design method of impellers at each stage currently used in domestic compressor design will inevitably lead to the speed ratio of the subsequent stages of the compressor deviating from the optimal range. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a one-dimensional optimization method and system for a carbon dioxide centrifugal compressor based on an optimal specific speed. The method and system can effectively prevent the specific speeds of each stage of the compressor from deviating from the optimal range.

[0006] To achieve the above object, the one-dimensional optimization method of the carbon dioxide centrifugal compressor based on the optimal specific speed of the present invention comprises the following steps:

[0007] 1) According to the compression design boundary conditions, the total number of compressor stages j and the speed r, calculate the average specific speed N of each stage under the number of compressor stages and each speed combination s,m ; The calculated compressor number of stages and the average specific speed N of each stage under each speed combination s,m Sort the products j*r from small to large, determine the stage number and speed information whose stage average specific speed value is within the preset range, then select the optimal stage number and speed combination from the determined stage number and speed information, and then determine the stage average isentropic enthalpy increase Δh of the compressor according to the total number of stages j and the operating speed r of the compressor. s,m Average specific speed N s,m ;

[0008] 2) According to the average isentropic enthalpy increase Δh of the compressor stage s,m Average specific speed N s,mThe enthalpy increase of each stage is adjusted on the basis of the average enthalpy increase of the stage, so that the speed ratio of each stage of the compressor is in the optimal range, completing the one-dimensional optimization of the carbon dioxide centrifugal compressor based on the optimal speed ratio.

[0009] In step 1), according to the compression design boundary conditions, the average specific speed of each stage of the compressor under each combination of the number of stages and speed is calculated according to the total number of compressor stages j from 1, 2, 3, ..., 10 and the speed r from 3000, 6000, 9000, ..., 30000 r / min.

[0010] In step 1), Among them, ω=2πr / 60 is the rotor angular velocity, is the average isentropic enthalpy increase, β l,m is the average leakage loss coefficient of the stage, is the average inlet volume flow rate of the stage, where q v,in and q v,out The volume flow rate of the whole machine inlet and outlet respectively.

[0011] In step 1), the preset interval is [0.5-0.9].

[0012] The specific operations of step 2) are:

[0013] 2.1) According to the preset isentropic efficiency η at each level s,i 、Gas leakage loss coefficient β at each level l,i , stage average specific speed N s,m And the volume flow rate q of the first stage 0-0 section v,01 Calculate the first-stage isentropic enthalpy increase Δh s,1 , and then calculate the first-stage outlet 7-7 section according to the preset stage isentropic efficiency, and obtain the second-stage inlet volume flow rate q according to the first-stage outlet 7-7 section v,02 ;

[0014] 2.2) Repeat step 2.1) until the isentropic enthalpy increase Δh of each stage of the compressor is obtained. s,i ;

[0015] 2.3) Determine the sum of isentropic enthalpy increases at each level ∑Δh s,i Is it equal to the isentropic enthalpy increase Δh of the whole machine? s , when the sum of the isentropic enthalpy increases at each level ∑Δh s,i Equal to the isentropic enthalpy increase of the whole machine Δh s When the final stage average specific speed N is obtained s , isentropic enthalpy increase Δh at each level s,i , Actual enthalpy increase at each level Otherwise, calculate the sum of the isentropic enthalpy increases at each level ∑Δh s,i The isentropic enthalpy increase Δh s The percentage of difference;

[0016] 2.4) Correct the average specific speed according to the percentage calculated in step 2.3), and use the corrected average specific speed to replace the uncorrected average specific speed in step 2.2), and then go to step 2.2).

[0017] In step 2.3), the sum of all isentropic enthalpy increases ∑Δh s,i The isentropic enthalpy increase Δh s The percentage difference is

[0018] Corrected average specific speed

[0019] The first-stage outlet 7-7 section is the second-stage 0`-0` section state parameter.

[0020] The one-dimensional optimization system of the carbon dioxide centrifugal compressor based on the optimal specific speed of the present invention comprises:

[0021] The calculation module is used to calculate the average specific speed N of each stage under each speed combination according to the total number of compressor stages j and speed r according to the compression design boundary conditions. s,m ; The calculated compressor number of stages and the average specific speed N of each stage under each speed combination s,m Sort the products j*r from small to large, determine the stage number and speed information whose stage average specific speed value is within the preset range, then select the optimal stage number and speed combination from the determined stage number and speed information, and then determine the stage average isentropic enthalpy increase Δh of the compressor according to the total number of stages j and the operating speed r of the compressor. s,m Average specific speed N s,m ;

[0022] The regulating module is used to adjust the average isentropic enthalpy increase Δh according to the compressor stage s,m Average specific speed N s,m The enthalpy increase of each stage is adjusted on the basis of the average enthalpy increase of the stage, so that the speed ratio of each stage of the compressor is in the optimal range, completing the one-dimensional optimization of the carbon dioxide centrifugal compressor based on the optimal speed ratio.

[0023] The present invention has the following beneficial effects:

[0024] The one-dimensional optimization method and system of the carbon dioxide centrifugal compressor based on the optimal specific speed of the present invention first selects the optimal stage number and speed combination during specific operation, and then calculates the average isentropic enthalpy increase Δh of the compressor stage. s,m Average specific speed N s,m , then the average isentropic enthalpy increase Δh in the compressor stage s,m Average specific speed N s,mOn the basis of this, the enthalpy increase of each stage is adjusted on the basis of the average enthalpy increase of the stage, so that the speed ratio of each stage of the compressor is in the optimal range, avoiding the speed ratio of the subsequent stage of the compressor deviating from the optimal range. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in combination with the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments, and is not intended to limit the scope of the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should belong to the scope of protection of the present invention.

[0026] The one-dimensional optimization method of the carbon dioxide centrifugal compressor based on the optimal specific speed of the present invention comprises the following steps:

[0027] 1) According to the compression design boundary conditions, the average specific speed of each stage of the compressor under each stage number and speed combination is calculated according to the total number of compressor stages j from 1, 2, 3, ..., 10 and the speed r from 3000, 6000, 9000, ..., 30000 r / min, among which the average specific speed after stage leakage loss is calculated Among them, ω=2πr / 60 is the rotor angular velocity, is the average isentropic enthalpy increase, β l,m is the average leakage loss coefficient of the stage, is the average inlet volume flow rate of the stage, where q v,in and q v,out The volume flow rate of the whole machine inlet and outlet respectively;

[0028] The calculated compressor number of stages and the average specific speed N of each stage under each speed combination are s,m Sort the j*r products from small to large, determine the stage number and speed information where the stage average specific speed value is in the range of [0.5-0.9], and then select the optimal stage number and speed combination from the determined stage number and speed information according to the actual situation, and then determine the total number of compressor stages j and operating speed r, and then determine the average isentropic enthalpy increase Δh of the compressor stage s,m Average specific speed N s,m ;

[0029] 2) For the determined average specific speed N s,mIn order to avoid the increase of density and decrease of flow rate in the rear stage of the compressor, which will lead to the decrease of compressor specific speed and design efficiency, the enthalpy increase of each stage is adjusted on the basis of the average enthalpy increase of the stage, increasing the enthalpy increase of the front stage and reducing the enthalpy increase of the rear stage, so that the specific speed of each stage is in the optimal range and approximately equal. The specific optimization process is as follows:

[0030] 2.1) According to the preset isentropic efficiency η at each level s,i 、Gas leakage loss coefficient β at each level l,i , stage average specific speed N s,m And the volume flow rate q of the first stage 0-0 section v,01 Calculate the first-stage isentropic enthalpy increase Δh s,1 Then, according to the preset isentropic efficiency, the first-stage outlet 7-7 section, that is, the state parameter of the second-stage 0`-0` section, is calculated, and the second-stage inlet volume flow rate q is obtained according to the first-stage outlet 7-7 section v,02 ;

[0031] 2.2) Repeat step 2.1) until the isentropic enthalpy increase Δh of all stages is obtained s,i ;

[0032] 2.3) Determine the sum of all isentropic enthalpy increases ∑Δh s,i Is it equal to the isentropic enthalpy increase Δh of the whole machine? s , when the sum of all isentropic enthalpy increases ∑Δh s,i Equal to the isentropic enthalpy increase of the whole machine Δh s When the final stage average specific speed N is obtained s , isentropic enthalpy increase Δh at each level s,i , Actual enthalpy increase at each level Otherwise, calculate the sum of all isentropic enthalpy increases ∑Δh s,i The isentropic enthalpy increase Δh s Percentage of Difference

[0033] 2.4 The percentage-corrected average specific speed calculated according to step 2.3) The corrected average specific speed is used to replace the uncorrected average specific speed in step 2.2), and then go to step 2.2).

[0034] 3) For the algorithm involved in step 2.1), the unknown section parameters need to be calculated from the known section parameters. When all the state parameters of the aa section and the velocity c are known a , velocity c of section bb b (or area A b ), the total enthalpy increase ΔH from section aa to section bb ab and loss ab,loss , where the loss h ab,loss Included in the total enthalpy increase ΔH abIn the equation, let k represent the number of iterations. The iterative algorithm for finding the state parameters of the bb section is:

[0035] 3.1) When the velocity of section b is known, then c b,k =c b ; When the cross-sectional area of ​​bb is known, the cross-sectional velocity of bb is Among them, q m represents the mass flow rate, v b,k represents the specific volume of the bb section. The first iteration uses the aa section density as the initial value, that is, v b,0 =v a , in subsequent iterations, the v obtained in the previous iteration is used b,k ;

[0036] 3.2) Find the static enthalpy increase of process ab and the static enthalpy value h of the bb section b =h a +Δh ab ;

[0037] 3.3) According to the static enthalpy value h of the bb section b and entropy value s b =s a , find the parameters of the bb section during the isentropic process, that is, the isentropic pressure p b,s , isentropic temperature T b,s , and calculate

[0038] 3.4) Calculate σ m,k , where, for the impeller, stage or complete machine, ΔH ab ≠0; p b >p a ,but For the expansion channel, ΔH ab =0; p b >p a ,but For the convergent channel, ΔH ab =0; p b <p a ,but

[0039] Take the initial value at the first iteration p b,0 =p b,s , where κ is the adiabatic index of the ab process;

[0040] 3.5) Utilization Calculate T b,k ;

[0041] 3.6) Using h b and Tb,k Calculate p according to physical property parameters b,k and v b,k ;

[0042] 3.7) Repeat steps 3.1) to 3.6) until |v b,k -v b,k-1 |<10 -6 , let c b =c b,k 、p b =p b,k 、v b =v b,k 、T b =T b,k and σ m =σ m,k , thereby determining the bb section state parameters.

[0043] Embodiment 2

[0044] The one-dimensional optimization system of the carbon dioxide centrifugal compressor based on the optimal specific speed of the present invention comprises:

[0045] The calculation module is used to calculate the average specific speed N of each stage under each speed combination according to the total number of compressor stages j and speed r according to the compression design boundary conditions. s,m ; The calculated compressor number of stages and the average specific speed N of each stage under each speed combination s,m Sort the products j*r from small to large, determine the stage number and speed information whose stage average specific speed value is within the preset range, then select the optimal stage number and speed combination from the determined stage number and speed information, and then determine the stage average isentropic enthalpy increase Δh of the compressor according to the total number of stages j and the operating speed r of the compressor. s,m Average specific speed N s,m ;

[0046] The regulating module is used to adjust the average isentropic enthalpy increase Δh according to the compressor stage s,m Average specific speed N s,m The enthalpy increase of each stage is adjusted on the basis of the average enthalpy increase of the stage, so that the speed ratio of each stage of the compressor is in the optimal range, completing the one-dimensional optimization of the carbon dioxide centrifugal compressor based on the optimal speed ratio.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A one-dimensional optimization method for a carbon dioxide centrifugal compressor based on optimal specific speed, characterized in that: The following steps are involved: 1) According to the compression design boundary conditions, the total number of compressor stages j and the speed r, calculate the average specific speed N of each stage under the number of compressor stages and each speed combination s,m ; The calculated compressor number of stages and the average specific speed N of each stage under each speed combination s,m Sort the products j*r from small to large, determine the stage number and speed information whose stage average specific speed value is within the preset range, then select the optimal stage number and speed combination from the determined stage number and speed information, and then determine the stage average isentropic enthalpy increase Δh of the compressor according to the total number of stages j and the operating speed r of the compressor. s,m Average specific speed N s,m ; 2) According to the average isentropic enthalpy increase Δh of the compressor stage s,m Average specific speed N s,m The enthalpy increase of each stage is adjusted on the basis of the average enthalpy increase of the stage, so that the speed ratio of each stage of the compressor is in the optimal range, completing the one-dimensional optimization of the carbon dioxide centrifugal compressor based on the optimal speed ratio.

2. The one-dimensional optimization method of a carbon dioxide centrifugal compressor based on optimal specific speed according to claim 1, characterized in that: In step 1), according to the compression design boundary conditions, the average specific speed of each stage of the compressor under each combination of the number of stages and speed is calculated according to the total number of compressor stages j from 1, 2, 3, ..., 10 and the speed r from 3000, 6000, 9000, ..., 30000 r / min.

3. The one-dimensional optimization method of a carbon dioxide centrifugal compressor based on optimal specific speed according to claim 1, characterized in that: In step 1), Among them, ω=2πr / 60 is the rotor angular velocity, is the average isentropic enthalpy increase, β l,m is the average leakage loss coefficient of the stage, is the average inlet volume flow rate of the stage, where q v,in and q v,out The volume flow rate of the whole machine inlet and outlet respectively.

4. The one-dimensional optimization method of a carbon dioxide centrifugal compressor based on an optimal specific speed according to claim 1, characterized in that: In step 1), the preset interval is [0.5-0.9].

5. The one-dimensional optimization method of a carbon dioxide centrifugal compressor based on optimal specific speed according to claim 1, characterized in that: The specific operations of step 2) are: 2.1) According to the preset isentropic efficiency η at each level s,i 、Gas leakage loss coefficient β at each level l,i , stage average specific speed N s,m And the volume flow rate q of the first stage 0-0 section v,01 Calculate the first-stage isentropic enthalpy increase Δh s,1 , and then calculate the first-stage outlet 7-7 section according to the preset stage isentropic efficiency, and obtain the second-stage inlet volume flow rate q according to the first-stage outlet 7-7 section v,02 ; 2.2) Repeat step 2.1) until the isentropic enthalpy increase Δh of each stage of the compressor is obtained. s,i ; 2.3) Determine the sum of isentropic enthalpy increases at each level ∑Δh s,i Is it equal to the isentropic enthalpy increase Δh of the whole machine? s , when the sum of the isentropic enthalpy increases at each level ∑Δh s,i Equal to the isentropic enthalpy increase of the whole machine Δh s When the final stage average specific speed N is obtained s , isentropic enthalpy increase Δh at each level s,i , Actual enthalpy increase at each level Otherwise, calculate the sum of the isentropic enthalpy increases at each level ∑Δh s,i The isentropic enthalpy increase Δh s The percentage of difference; 2.4) Correct the average specific speed according to the percentage calculated in step 2.3), and use the corrected average specific speed to replace the uncorrected average specific speed in step 2.2), and then go to step 2.2).

6. The one-dimensional optimization method of a carbon dioxide centrifugal compressor based on an optimal specific speed according to claim 5, characterized in that: In step 2.3), the sum of all isentropic enthalpy increases ∑Δh s,i The isentropic enthalpy increase Δh s The percentage difference is 7. The one-dimensional optimization method of a carbon dioxide centrifugal compressor based on optimal specific speed according to claim 5, characterized in that: Corrected average specific speed 8. The one-dimensional optimization method for a carbon dioxide centrifugal compressor based on an optimal specific speed according to claim 5, characterized in that: The first-stage outlet 7-7 section is the second-stage 0`-0` section state parameter.

9. A one-dimensional optimization system for a carbon dioxide centrifugal compressor based on optimal specific speed, characterized in that: include: The calculation module is used to calculate the average specific speed N of each stage under each speed combination according to the total number of compressor stages j and speed r according to the compression design boundary conditions. s,m ; The calculated compressor number of stages and the average specific speed N of each stage under each speed combination s,m Sort the products j*r from small to large, determine the stage number and speed information whose stage average specific speed value is within the preset range, then select the optimal stage number and speed combination from the determined stage number and speed information, and then determine the stage average isentropic enthalpy increase Δh of the compressor according to the total number of stages j and the operating speed r of the compressor. s,m Average specific speed N s,m ; The regulating module is used to adjust the average isentropic enthalpy increase Δh according to the compressor stage s,m Average specific speed N s,m The enthalpy increase of each stage is adjusted on the basis of the average enthalpy increase of the stage, so that the speed ratio of each stage of the compressor is in the optimal range, completing the one-dimensional optimization of the carbon dioxide centrifugal compressor based on the optimal speed ratio.

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