阅读说明：本技术 超临界二氧化碳轴流压缩机防止叶片共振的调频运行方法 (Frequency modulation operation method for preventing blade resonance of supercritical carbon dioxide axial flow compressor ) 是由 李凯伦 李红智 姚明宇 张一帆 高炜 吴帅帅 杨浦 张旭伟 于 2021-08-10 设计创作，主要内容包括：一种超临界二氧化碳轴流压缩机防止叶片共振的调频运行方法,所述方法在测试静频率和换算动频率的基础上,通过绘图法得到若干个压缩机叶片共振频率。然后,通过取合适的避开率得到若干个叶片共振频率的危险区间,再取压缩机运行频率范围与共振频率危险区间的差集,可以得到若干个压缩机安全运行转速档。在调节过程中,当压缩机安全运行在某一转速档下时,若需要调节出力则首先采用调门进行调节,当调门达到其调节上下限时,再通过压缩机转速档位进行调节。本发明通过二氧化碳压缩机入口调门和转速的联合调节,使压缩机运行频率远离叶片共振频率,同时保持压缩机大开度高效率运行,为二氧化碳轴流式压缩机的安全高效运行提供了可行的控制方案。(A frequency modulation operation method for preventing blade resonance of a supercritical carbon dioxide axial flow compressor is characterized in that on the basis of testing static frequency and converting dynamic frequency, a plurality of compressor blade resonance frequencies are obtained through a drawing method. Then, a plurality of dangerous intervals of blade resonance frequency are obtained by taking a proper avoidance rate, and then a difference set of the running frequency range of the compressor and the dangerous intervals of the resonance frequency is taken, so that a plurality of safe running speed gears of the compressor can be obtained. In the adjusting process, when the compressor safely operates under a certain speed gear, the adjusting door is firstly adopted for adjusting if the output force needs to be adjusted, and when the adjusting door reaches the upper limit and the lower limit of the adjustment, the rotating speed gear of the compressor is adjusted. The invention leads the running frequency of the compressor to be far away from the resonance frequency of the blade through the combined regulation of the inlet throttle and the rotating speed of the carbon dioxide compressor, simultaneously keeps the compressor to run with large opening degree and high efficiency, and provides a feasible control scheme for the safe and high-efficiency running of the carbon dioxide axial flow compressor.)

1. A frequency modulation operation method for preventing blade resonance of a supercritical carbon dioxide axial flow compressor is characterized in that the frequency range f of a variable frequency motor of the compressor is 20 Hz-50 Hz, the number of magnetic pole pairs is P, the temperature range t of a working medium in a cavity of the compressor is 80-150 ℃, the compressor is n stages in total, and the number of blades at each stage is Z; the frequency modulation operation method comprises the following implementation steps: obtaining the first three static frequencies of the n-stage blades of the compressor through a knocking test, and obtaining the first three dynamic frequencies of the n-stage blades through frequency conversion; step two: solving the intersection point of the dynamic frequency and the operating frequency of the first three orders and the intersection point of the dynamic frequency and the blade passing frequency by a drawing method so as to obtain the blade resonance frequency and the resonance rotating speed; step three: a preset avoidance value is taken for the resonant frequency of the blade, and a complementary set is taken after the dangerous interval of the resonant frequency is refined and segmented, so that the allowable operating frequency intervals of a plurality of compressors are obtained; step four: taking a median value for an allowed operating frequency opening interval of the compressor, thereby obtaining a plurality of compressor speed gears; step five: and when the opening degree reaches the maximum opening degree or the minimum opening degree, the adjustment is continued through the increase or decrease of the rotating speed gear, so that a theoretical basis is provided for the switching of the compressor between the high gear and the low gear.

2. The frequency modulation operation method for preventing blade resonance of supercritical carbon dioxide axial flow compressor as claimed in claim 1, wherein in the first step, the first three static frequencies of n-stage blades obtained by field knock test are respectively F^* _1i、F^* _2iAnd F^* _3iWherein i is 1,2,3 … n; obtaining the first three-order dynamic frequency F of the n-stage blade through frequency conversion_1i(f,t)、F_2i(F, t) and F_3i(f, t), wherein the dynamic frequency is changed along with the change of the running frequency f of the variable frequency motor and the temperature t of the working medium in the compressor.

3. The method for frequency modulation operation of a supercritical carbon dioxide axial flow compressor to prevent blade resonance as claimed in claim 1, wherein in the second step, the first three-order dynamic frequency F is solved by using a Campbell drawing method_1i(f,t)、F_2i(f,t)、F_3i(f, t) and the first three-order operating frequencies f, 2 f, 3 f of the compressor in f e [20/P, 50/P ]]Inner cross point, and first third order dynamic frequency F_1i(f,t)、F_2i(f,t)、F_3i(f, t) passing frequencies fZ, 2 x fZ and 3 x fZ of the first three stages of the blades of the compressor are within f e [20/P x Z, 50/P x Z]The inner intersection points are assumed to obtain m intersection points, and the frequency f values corresponding to the m intersection points are the blade resonance frequencies and are respectively numbered as f_jWhere j is 1,2,3 … m.

4. The frequency modulation operation method for preventing blade resonance of supercritical carbon dioxide axial flow compressor according to claim 1, wherein in the third step, 3% -5% avoidance rate is adopted for each blade resonance frequency, and for 3% avoidance rate, the danger interval of each blade resonance frequency is obtained as [0.97 f [/]_j,1.03*f_j]Wherein j is 1,2,3 … m; taking a difference set [20,50 ] of dangerous intervals of the operating frequency range of the compressor and the resonant frequency of the blade]\Σ[0.97*f_j,1.03*f_j]I.e. the complement of the dangerous interval of the blade resonance frequency in the compressor operating frequency range, so as to obtain the open interval (f) of the allowable operating frequencies of the k compressors_si,f_ei) Where i is 1,2,3 … k^*(ii) a If a certain open interval f_ei-f_siIf the frequency is more than 5Hz, the open interval is divided into two parts: (f)_si,(f_si,+f_ei) /2) and ((f)_si,+f_ei)/2，f_ei) Until k compressors are finally obtainedOpen interval of operation (f)_si,f_ei) Wherein i is 1,2,3 … k, and f_ei-f_si＜5Hz。

5. The frequency modulation operation method for preventing blade resonance of supercritical carbon dioxide axial flow compressor as claimed in claim 1, wherein in the fourth step, the median f of the allowable operation frequency open interval of k compressors is taken_gi＝(f_si,+f_ei) And 2, obtaining frequency values of k compressor variable frequency motors capable of safely operating, wherein the frequency values correspond to k rotation speed gears of the compressor, and when the compressor operates under the k rotation speed gears, the compressor cannot generate a blade resonance phenomenon.

6. The frequency modulation operation method for preventing blade resonance of the supercritical carbon dioxide axial flow compressor as claimed in claim 1, wherein in the fifth step, the method for obtaining the corresponding relationship between the minimum opening degree of the high-order speed gear and the maximum opening degree of the low-order speed gear comprises the following steps: for the ith compressor gear, 1 < i < k +1, the only minimum regulating valve opening X required for output exists_iWhen the compressor is operated in the ith speed gear and the inlet adjusting opening is X_iWhen the compressor is in the state of the i-1 th speed gear, the output of the compressor is equal to the output of the compressor, and the opening of the inlet is adjusted to be 100%.

7. The method for frequency modulation operation of an axial flow compressor for supercritical carbon dioxide to prevent blade resonance as claimed in claim 1, wherein in the fourth step, the frequency span between the rotational speed gears of each compressor is less than 5Hz, and the minimum opening X of the damper required for ensuring output force is ensured_iThe value range is 70-100%, wherein i is more than 1 and less than k + 1.

8. The method as claimed in claim 1, wherein in step five, when the compressor is operated at the i-th speed stage, 1 < i < k +1, the opening of the damper is decreased when the compressor needs to decrease the output, and the damper is decreased when the compressor needs to decrease the outputOpening degree is reduced to X_iWhen the speed is higher than the preset speed, quickly reducing the compressor to an i-1 rotation speed gear and keeping the opening degree of the throttle at 100 percent; when the compressor needs to increase the output, the opening of the throttle is increased, and when the opening of the throttle is increased to 100%, the compressor is quickly increased to an i +1 speed gear and the opening of the throttle is kept to be X_i+1。

9. The frequency modulation operation method for preventing the blade resonance of the supercritical carbon dioxide axial flow compressor as claimed in claim 1, wherein the compressor adopts a method of jointly adjusting the rotational speed gear and the opening degree in actual operation, so that on one hand, the compressor can be ensured to be far away from the blade resonance frequency, on the other hand, the compressor can be kept to operate at a higher opening degree, the compressor keeps higher operation efficiency, and meanwhile, the safety and the economical efficiency are kept.

Technical Field

The invention relates to the technical field of supercritical carbon dioxide cyclic power generation, in particular to a frequency modulation operation method for preventing blade resonance of a supercritical carbon dioxide axial flow compressor.

Background

With the development of power generation technology in recent years, research shows that a generator set adopts supercritical carbon dioxide to replace steam as a circulating working medium, and has the advantages of high circulating efficiency, compact equipment structure, low capital investment and the like in a certain power range, so that the supercritical carbon dioxide circulating power generation system is a power generation mode with great technical prospect.

Disclosure of Invention

Based on the above consideration, the invention aims to provide a frequency modulation operation method for preventing blade resonance of a supercritical carbon dioxide axial flow compressor, which has the main advantage that the operation frequency of the compressor is far away from the blade resonance frequency through the combined adjustment of an inlet throttle and the rotating speed of the carbon dioxide compressor, and the compressor is kept to operate at high efficiency with large opening.

In order to achieve the purpose, the invention adopts the technical scheme that:

a frequency modulation operation method for preventing blade resonance of a supercritical carbon dioxide axial flow compressor is characterized in that the frequency range f of a variable frequency motor of the compressor is 20 Hz-50 Hz, the number of magnetic pole pairs is P, the temperature range t of a working medium in a cavity of the compressor is 80-150 ℃, the compressor is divided into n stages, and the number of blades of each stage is Z; the frequency modulation operation method comprises the following implementation steps: obtaining the first three static frequencies of the n-stage blades of the compressor through a knocking test, and obtaining the first three dynamic frequencies of the n-stage blades through frequency conversion; step two: solving the intersection point of the dynamic frequency and the operating frequency of the first three orders and the intersection point of the dynamic frequency and the blade passing frequency by a drawing method so as to obtain the blade resonance frequency and the resonance rotating speed; step three: a preset avoidance value is taken for the resonant frequency of the blade, and a complementary set is taken after the dangerous interval of the resonant frequency is refined and segmented, so that the allowable operating frequency intervals of a plurality of compressors are obtained; step four: taking a median value for an allowed operating frequency opening interval of the compressor, thereby obtaining a plurality of compressor speed gears; step five: and when the opening degree reaches the maximum opening degree or the minimum opening degree, the adjustment is continued through the increase or decrease of the rotating speed gear, so that a theoretical basis is provided for the switching of the compressor between the high gear and the low gear.

In the first step, the first three-order static frequencies of the n-stage blades obtained through the field knocking test are respectively F^* _1i、F^* _2iAnd F^* _3iWherein i is 1,2,3 … n; obtaining the first three-order dynamic frequency F of the n-stage blade through frequency conversion_1i(f,t)、F_2i(F, t) and F_3i(f, t), wherein the dynamic frequency is changed along with the change of the running frequency f of the variable frequency motor and the temperature t of the working medium in the compressor.

In the second step, the first three-order dynamic frequency F is solved by adopting a drawing Campbell method_1i(f,t)、F_2i(f,t)、F_3i(f, t) and the first three-order operating frequencies f, 2 f, 3 f of the compressor in f e [20/P, 50/P ]]Inner cross point, and first third order dynamic frequency F_1i(f,t)、F_2i(f,t)、F_3i(f, t) passing frequencies fZ, 2 x fZ and 3 x fZ of the first three stages of the blades of the compressor are within f e [20/P x Z, 50/P x Z]The inner intersection points are assumed to obtain m intersection points, and the frequency f values corresponding to the m intersection points are the blade resonance frequencies and are respectively numbered as f_jWhere j is 1,2,3 … m.

In the third step, 3% -5% of avoidance rate is taken for the resonant frequency of each blade, and for the 3% of avoidance rate, the dangerous interval of the resonant frequency of each blade is obtained as [0.97 f [ ]_j,1.03*f_j]Wherein j is 1,2,3 … m; within the operating frequency range of the compressorSet of differences [20,50 ] from the danger zone of the blade resonance frequency]\Σ[0.97*f_j,1.03*f_j]I.e. the complement of the dangerous interval of the blade resonance frequency in the compressor operating frequency range, so as to obtain the open interval (f) of the allowable operating frequencies of the k compressors_si,f_ei) Where i is 1,2,3 … k^*(ii) a If a certain open interval f_ei-f_siIf the frequency is more than 5Hz, the open interval is divided into two parts: (f)_si,(f_si,+f_ei) /2) and ((f)_si,+f_ei)/2，f_ei) Until k open intervals (f) allowing the operation of the compressor are obtained_si,f_ei) Wherein i is 1,2,3 … k, and f_ei-f_si＜5Hz。

In the fourth step, the median f of the open interval of the allowable operating frequencies of the k compressors is taken_gi＝(f_si,+f_ei) And 2, obtaining frequency values of k compressor variable frequency motors capable of safely operating, wherein the frequency values correspond to k rotation speed gears of the compressor, and when the compressor operates under the k rotation speed gears, the compressor cannot generate a blade resonance phenomenon.

In the fifth step, the method for obtaining the corresponding relationship between the minimum opening degree of the high-order rotation speed gear and the maximum opening degree of the low-order rotation speed gear comprises the following steps: for the ith compressor gear, 1 < i < k +1, the only minimum regulating valve opening X required for output exists_iWhen the compressor is operated in the ith speed gear and the inlet adjusting opening is X_iWhen the compressor is in the state of the i-1 th speed gear, the output of the compressor is equal to the output of the compressor, and the opening of the inlet is adjusted to be 100%.

In the fourth step, the frequency span between the rotating speed gears of each compressor is less than 5Hz, and the minimum opening X of the regulating valve required by output force is ensured_iThe value range is 70-100%, wherein i is more than 1 and less than k + 1.

In the fifth step, when the compressor runs at the ith rotating speed gear in actual operation, and the i is more than 1 and less than k +1, when the compressor needs to reduce the output, the opening degree of the throttle is reduced, and when the opening degree of the throttle is reduced to X_iWhen the speed is higher than the preset speed, quickly reducing the compressor to an i-1 rotation speed gear and keeping the opening degree of the throttle at 100 percent; when the compressor needs to increase the output, the opening of the regulating valve is increased, and when the opening of the regulating valve is increased to 100 percentThen quickly regulating the compressor to i +1 speed gear and keeping the opening of the regulating valve at X_i+1。

In actual operation, the compressor adopts a combined adjusting method of a speed gear and an opening degree, on one hand, the compressor can be ensured to be far away from the resonance frequency of the blades, on the other hand, the compressor can be kept to operate under a higher opening degree, the compressor keeps higher operation efficiency, and meanwhile, the safety and the economical efficiency are kept.

Compared with the prior art, the invention has the following advantages:

1) the danger interval and the safety interval are identified and marked by adopting a number domain interval concept, so that the operability is stronger, and the whole process of implementation can be automatically operated;

2) through the joint adjustment of the rotating speed step and the opening degree, the resonance of the blades is avoided, and meanwhile, the compressor is always kept to operate in a high-efficiency interval.

Detailed Description

The present invention will be described in further detail with reference to examples.

The invention provides a frequency modulation operation method for preventing blade resonance of a supercritical carbon dioxide axial flow compressor, which is characterized by comprising a compressor (1), a compressor inlet throttle (2), a variable frequency motor (3) and compressor blades (4), wherein the frequency range f of the variable frequency motor of the compressor is 20 Hz-50 Hz, the temperature t range of a working medium in a cavity of the compressor is 80-150 ℃, the compressor is n stages in total, and the number of the blades at each stage is Z.

1. Firstly, obtaining the first three-order static frequencies of each stage of the n-stage blade as F through a field knocking test^* _1i、F^* _2iAnd F^* _3iWherein i is 1,2,3 … n. Obtaining the first three-order dynamic frequency F of the n-stage blade through frequency conversion_1i(f,t)、F_2i(F, t) and F_3i(f, t), wherein the dynamic frequency is changed along with the change of the running frequency f of the variable frequency motor and the temperature t of the working medium in the compressor.

2. Secondly, solving the first three-order dynamic frequency F by adopting a drawing Campbell diagram method_1i(f,t)、F_2i(f,t)、F_3i(f, t) and the first three-order operating frequencies f, 2 f, 3 f of the compressor in f E [20,50 [ ]]The point of intersection of the inner portions,and the first third order dynamic frequency F_1i(f,t)、F_2i(f,t)、F_3i(f, t) passing frequencies fZ, 2 x fZ and 3 x fZ of the first three stages of blades of the compressor in f e [20,50 [ ]]The inner intersection points are assumed to obtain m intersection points, and the frequency f values corresponding to the m intersection points are the blade resonance frequencies and are respectively numbered as f_jWhere j is 1,2,3 … m.

3. The avoidance rate of 3% is taken for the resonant frequency of each blade, and the danger interval of the resonant frequency of each blade is obtained to be [0.97 f%_j,1.03*f_j]Where j is 1,2,3 … m. Taking a difference set [20,50 ] of dangerous intervals of the operating frequency range of the compressor and the resonant frequency of the blade]\Σ[0.97*f_j,1.03*f_j]To obtain k^*An open interval (f) of allowable operating frequency of the compressor_si,f_ei) Where i is 1,2,3 … k^*. If a certain open interval f_ei-f_siIf the frequency is more than 5Hz, the open interval is divided into two parts: (f)_si,(f_si,+f_ei) /2) and ((f)_si,+f_ei)/2，f_ei) Until k open intervals (f) allowing the operation of the compressor are obtained_si,f_ei) Where i is 1,2,3 … k, and f_ei-f_si＜5Hz。

4. Taking the median f of the open interval of the allowable operating frequencies of k compressors_gi＝(f_si,+f_ei) And 2, obtaining k frequency values of safe operation of the compressor, namely k speed steps, wherein when the compressor operates at the k speed steps, the compressor does not have the problem of blade resonance.

5. For the ith compressor gear (1 < i < k +1), there is a unique minimum throttle opening X required for power take-off_iWhen the compressor is operated at the ith speed gear and the inlet is adjusted to X degree of opening_iWhen the compressor is in the i-1 th speed gear, the output of the compressor is equal to the output of the compressor, and the opening degree of the inlet is adjusted to be 100%.

The frequency span between the rotating speed gears of each compressor is less than 5Hz, so that the minimum opening X of the regulating valve required by output force can be ensured_iThe value range is 70-100%, wherein i is more than 1 and less than k + 1.

6. When the compressor is operated at the ith rotating speed gear (1 < i) in actual operation< k +1), when the compressor needs to reduce the output, the opening of the throttle valve is preferentially reduced, and when the opening of the throttle valve is reduced to X_iWhen the speed is higher than the preset speed, the compressor is adjusted to the i-1 speed gear, and the opening degree of the adjusting valve is kept at 100 percent; when the compressor needs to increase the output, the opening of the throttle is preferentially increased, and when the opening of the throttle is increased to 100%, the compressor is increased to the i +1 rotation speed gear and the opening of the throttle is kept to be X_i+1。