CN114218733A - Vibration reduction method for reciprocating compressor pipeline system of CNG gas station - Google Patents
Vibration reduction method for reciprocating compressor pipeline system of CNG gas station Download PDFInfo
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Abstract
The invention discloses a vibration reduction method for a reciprocating compressor pipeline system of a CNG gas station. Carrying out grid independence verification on an outlet pipeline of the gas inlet pipeline, a safety diffusion pipeline and the like by establishing a pipeline model of the reciprocating compressor; then calculating the natural frequency of each pipeline structure and the natural frequency of the air column of the compressor piping system based on finite element analysis software, providing a vibration check standard of the compressor piping system, and carrying out resonance analysis on the compressor piping system according to the resonance check standard; performing bidirectional transient fluid-solid coupling between gas in the pipeline and the pipeline, monitoring the displacement condition and the gas pulsation condition of the pipeline, and checking the compressor pipeline according to the API618 specification; and finally, providing specific application measures for reducing the structure resonance and the gas column resonance based on model calculation. The invention fits finite element software and a fluid-solid coupling analysis method to solve and calculate the piping system, provides a CNG compressor piping system vibration check standard to check the calculation result, and provides a specific application measure for reducing the structure resonance and the gas column resonance.
Description
Technical Field
The invention relates to the technical field of energy utilization, in particular to a vibration reduction method for a reciprocating compressor pipeline system of a CNG gas station.
Background
The economic and social development can not be kept away from the sustainable and effective energy supply. The promotion of a clean, low-carbon and high-efficiency natural gas power generation system to replace a coal-fired power generation system is an important measure for the improvement of green energy in China. At present, the holding amount of automobiles is continuously increased, and natural gas automobiles have quite wide development space on the basis of the large background. From the total amount of natural gas automobiles, CNG automobiles accelerate the fastest. With the increasing number of CNG automobiles, CNG gas stations are in a high-speed development trend.
Reciprocating compressors, also called reciprocating piston compressors and piston compressors, are widely used in CNG gas stations at present. From the mechanical structure, the reciprocating compressor is composed of a motion mechanism, a machine body part, a motor, a cylinder part, a control system and an auxiliary part, and the working principle of the reciprocating compressor is shown in figure 1.
Because the piston can periodically exhaust and suck gas, the reciprocating compressor can cause natural gas in the pipeline to form pulsating pressure when in operation, and the pipeline is likely to vibrate due to the impact of fluid, so that the operation of the device is influenced to a certain extent. In addition, the frequency of the pipe structure vibration system and the fluid vibration system is fixed, and if the vibration frequency of the compressor operation is similar to or consistent with one of the vibration frequencies, the pipe system may resonate, so that the safe production operation of the gas station is significantly affected.
Certain branch of Shanxi chemical enterprises have developed fire in 2006 and caused explosion. The reason is that the valve suddenly drops due to the vibration of the outlet pipeline of the hydrogen compressor of the plant, so that a lot of hydrogen rapidly leaks, and a fire is caused. When a single compressor debugging work is carried out in certain chemical fertilizer production factory in the south of Henan in 2007, process gases such as hydrogen and nitrogen mixed gas are introduced to carry out compression test run, so that severe vibration occurs to pipelines, the welding position of an outlet pipeline is broken, and gas leakage causes fire disasters, so that many people are killed. Gas leakage accidents also occurred in 1996 at a certain CNG gas station in Sichuan, and the accidents occurred mainly because the natural gas leakage was caused by fatigue fracture of the compressor outlet pipelines in a micro-vibration environment for a long time.
Chenjie professor of Beijing science and technology university makes statistics on accident cases which are representative of 100 CNG gas stations, and the Chenjie professor considers that the current CNG gas stations mainly have the following safety problems: the problems of compressor and pipe system vibration, natural gas quality, gas selling quality, gas storage container, misoperation and unqualified gas cylinders of CNG automobiles are solved. In all accidents, the accidents caused by the vibration of the compressor and the pipe system thereof account for the third place and reach 16 percent.
The reciprocating compressor pipeline system (hereinafter referred to as CNG compressor piping system) is the key component of CNG gas station, and its operation state is closely related to the operation benefit of station and the safety of production. If vibration occurs in the pipeline system, great negative effects are inevitably caused, such as: the long-time displacement causes the looseness of the connection positions of accessories such as instruments, pipeline supports and the like, and the probability of breakage of the connection bolts at the flange is improved; the natural gas leakage caused by the pipeline rupture causes the explosion accident; the pipeline vibrates seriously, can form great noise, and if the staff is in work in the relatively poor environment for a long time, its physical and mental health will certainly receive the influence. Therefore, the consequences caused by the vibration of the CNG compressor piping system are unfavorable for the physical and mental development of staff, and natural gas leakage is caused to cause fire and even explosion, and sometimes the safety of the CNG production operation is affected.
Therefore, the vibration generated in the operation process of the CNG compressor piping system is analyzed, the influence of the vibration on the piping system is analyzed, and effective vibration reduction measures are provided based on the analysis, so that the production safety, stability and orderliness of a gas station and the operation safety of a gas station pipeline system can be effectively ensured while the influence of the compressor vibration on the gas station is prevented.
Disclosure of Invention
The invention aims to provide a vibration reduction method for a CNG gas station reciprocating compressor pipeline system, which is used for improving the production safety, stability and orderliness of a gas station and the safety of the gas station pipeline system.
The invention provides a vibration reduction method for a pipeline system of a CNG gas station reciprocating compressor, which mainly adopts the following design ideas:
(1) analyzing the vibration problem of the compressor pipeline system of the CNG gas station, and establishing the compressor pipeline system (a compressor air inlet pipeline model, a compressor outlet pipeline model, a compressor sewage pipeline model and a compressor safety diffusion pipeline model).
(2) And calculating the natural frequency of the gas column and the structure natural frequency of the pipeline system, comparing the natural frequency with the vibration exciting frequency of the compressor, and analyzing the resonance condition of the pipeline.
(3) And providing a vibration check standard of the CNG compressor piping system and carrying out resonance analysis on the compressor piping system according to the resonance check standard.
(4) And performing bidirectional transient fluid-solid coupling, performing dynamic analysis on the pipeline system, analyzing the pipeline displacement condition and the gas pulsation condition, and checking the compressor pipeline system according to the API618 specification.
(5) Based on the research and calculation, corresponding vibration reduction measures are provided.
The invention provides a vibration reduction method for a pipeline system of a CNG gas station reciprocating compressor, which comprises the following steps:
s1, establishing a reciprocating compressor model by utilizing Solidworks software, and verifying the grid independence of an outlet pipeline of an air inlet pipeline, a safety diffusing pipeline and a sewage pipeline; and modeling the reciprocating compressor set pipeline according to the process condition and the installation diagram.
S2, providing a vibration check standard of a CNG compressor pipe system and checking the standard according to resonance
The two most important parameters in the resonance check standard are the exciting frequency and the resonance range of the compressor, and the exciting frequency f of the compressor pipeline of a certain CNG gas stationexFor example, 29.25Hz, it is generally considered that 0.8 to 1.2 times the excitation frequency is the resonance region, and the compressor resonance range is 23.4Hz to 35.1 Hz.
The pipe system is a relatively complex vibrating system, with natural frequencies typically of the order n. And the gas flows in the pipeline system, and the shape of the gas column is similar to the appearance of the pipeline. When a certain order or several orders of the natural frequency of the gas column coincide with the resonance area of the excitation frequency of the compressor, the pipeline can resonate, and the resonance is called gas column resonance; the pipe also resonates when a certain order or orders of the natural frequency of the structure coincide with the resonance zone of the excitation frequency of the compressor, this resonance being called structural resonance. The air column resonance and the structural resonance have the same consequences (both the consequences are the resonance of the pipeline), but the names are used for distinguishing because the reasons for the occurrence are different.
S3, natural frequency calculation and resonance analysis are carried out on the pipeline structure
And calculating the inherent frequency of the pipeline structure based on a Modal module in ANSYS Workbench software to obtain the inherent frequencies of the front 10 orders of the air inlet pipeline, the air outlet pipeline, the safety diffusing pipeline and the sewage discharge pipeline of the compressor.
The natural frequency of the air column is calculated by adopting a Model Acoustics module in ANSYS Workbench software.
And S4, performing bidirectional transient fluid-solid coupling between the gas in the pipeline and the pipeline, monitoring the displacement condition and the gas pulsation condition of the pipeline, and checking the compressor pipeline according to the API618 specification.
In the running process of the compressor, gas in the pipeline and the pipeline are mutually influenced, the actual conditions of corners and variable diameters of the compressor pipeline are more, and the gas flow can influence the pipeline to cause pipeline deformation; meanwhile, the gas in the pipeline is regarded as an elastic body with quality, and the deformation of the pipeline can also adversely affect the gas.
The method is characterized in that bidirectional Transient Fluid-solid coupling is performed based on a Transient Structural (ANSYS) module and a Fluid Flow (Fluid) module in ANSYS Workbench software, the displacement condition and the gas pulsation condition of a pipeline are monitored, and a compressor piping system is checked according to the API618 specification.
S5 provides a vibration control method for compressor piping
The basic methods for changing the natural frequency of the structure are as follows: 1. increasing or decreasing the number of supports; 2. the supporting mode is changed.
The basic methods for changing the shape of the gas column are: 1. changing the diameter and the length of the pipeline; 2. changing the angle of the pipe corner, such as changing a 90-degree right-angle turn into a 45-degree turn; 3. adding a buffer and a buffer tank; 4. a header is added.
Based on the steps, specific vibration reduction measures are provided for the specific compressor, and the aim of vibration reduction optimization is achieved.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
Fig. 1 is an operational schematic diagram of a reciprocating compressor.
FIG. 2 is a schematic plan view of the compressor piping.
Figure 3 is a schematic diagram of a reciprocating compressor pipeline three-dimensional model.
FIG. 4 is a schematic view of a compressor air inlet line model.
FIG. 5 is a diagram of a compressor outlet line model.
FIG. 6 is a schematic view of a compressor relief line model.
FIG. 7 is a model view of a compressor blowdown line.
FIG. 8 is a cloud of stresses experienced by the inner wall of the inlet duct.
FIG. 9 is a cloud of amplitudes experienced by the inner wall of the inlet duct.
FIG. 10 is a gas pressure cloud for a gas inlet line.
FIG. 11 is a cloud of stresses experienced by the inner wall of the outlet conduit.
FIG. 12 is an outlet conduit amplitude cloud.
FIG. 13 is an outlet duct gas pressure cloud.
FIG. 14 is a cloud of stress experienced by the inner wall of the safety relief pipeline.
FIG. 15 is a safe diffusion pipeline amplitude cloud.
Fig. 16 is a cloud of safe diffusion pipeline gas pressures.
FIG. 17 is a graph of the stress experienced by the inner wall of the trapway versus time.
Fig. 18 is a sewer amplitude cloud.
Fig. 19 is a sewer line gas pressure cloud.
FIG. 20 is an optimized front intake duct clamp layout.
FIG. 21 is an optimized intake duct clamp layout.
FIG. 22 is a comparison of natural frequencies of the front and rear ten-step structure before and after intake duct optimization.
Fig. 23 is optimization scheme 1 (header size Φ 32 × 3.5).
FIG. 24 shows the optimization scheme 2 (header size. phi.38X 4).
Fig. 25 is the optimization scheme 3 (header size Φ 40 × 4).
FIG. 26 is a comparison of the natural frequency of the first ten steps of the gas column before and after optimization of the outlet duct.
Fig. 27 is an explanatory abstract drawing.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
The vibration reduction method of the CNG gas station reciprocating compressor is explained in detail by taking a CNG gas station reciprocating compressor in a certain city as an example. The method comprises the following steps:
s1, establishing a reciprocating compressor model by utilizing Solidworks software, and verifying the grid independence of an outlet pipeline of an air inlet pipeline, a safety diffusing pipeline and a sewage pipeline;
the plan view of the layout of the CNG compressor piping system is shown in FIG. 2, and the main parameters of the model are shown in Table 1.
TABLE 1 model principal parameter table
| Name (R) | Unit of | Numerical value |
| Material | — | No. 20 steel |
| Modulus of elasticity | Pa | 2.06x108 |
| Poisson ratio | — | 0.3 |
| Minimum yield strength | MPa | 275 |
| Compressor outlet pipe diameter | mm | Ф22×3.5 |
| Compressor inlet pipe diameter | mm | Ф108×5 |
| Safe diffusing pipe diameter | mm | Ф57×4 |
| Pipe diameter of sewage pipe | mm | Ф57×4 |
And modeling the reciprocating compressor set pipeline according to the process condition and the installation diagram. The piping air inlet pipeline model, the high-pressure air outlet pipeline model, the safety relief pipeline and the sewage discharge pipeline model are shown in figures 4-7. Wherein the black arrows represent the fluid flow direction.
And (5) calculating by a model module to obtain the first two-order natural frequency of each model under different grid numbers, and obtaining the results shown in tables 2 to 3.
TABLE 2 verification of the independence of the pipeline structure model mesh
TABLE 3 air column model grid independence validation
When the error of the calculation result of the density of two adjacent grids of the model is within 5%, the calculation result is not sensitive to the number of the grids, the grids of the model are subjected to independence verification, the model is effective, and the grid independence threshold can be obtained. The independent thresholds for each model are shown in table 2.
TABLE 4 model independent thresholds
S2, providing a vibration check standard of a CNG compressor pipe system and checking the standard according to resonance
The two most important parameters in the resonance check standard are the exciting frequency and the resonance range of the compressor, and the exciting frequency f of the compressor pipeline of a certain CNG gas stationexFor example, 29.25Hz, it is generally considered that 0.8 to 1.2 times the excitation frequency is the resonance region, and the compressor resonance range is 23.4Hz to 35.1 Hz.
The pipe system is a relatively complex vibrating system, with natural frequencies typically of the order n. And the gas flows in the pipeline system, and the shape of the gas column is similar to the appearance of the pipeline. When a certain order or several orders of the natural frequency of the gas column coincide with the resonance area of the excitation frequency of the compressor, the pipeline can resonate, and the resonance is called gas column resonance; the pipe also resonates when a certain order or orders of the natural frequency of the structure coincide with the resonance zone of the excitation frequency of the compressor, this resonance being called structural resonance. The air column resonance and the structural resonance have the same consequences (both the consequences are the resonance of the pipeline), but the names are used for distinguishing because the reasons for the occurrence are different.
At present, China's checking standard in the aspect mainly refers to standard API618 reciprocating compressor for petrochemical industry and natural gas industry compiled by American Petroleum institute. The allowable compressor pipe vibration value standard checked based on the standard is shown in table 5.
TABLE 5 compressor piping vibration allowable value Standard
| Vibration region | Displacement double amplitude allowable value (mm) |
| Curve 1-mean perception Limit | 0.046 |
| Curve 2-design Limit | 0.128 |
| Curve 3-is a boundary between design and modification | 0.25 |
| Curve 4-modified Limit | 0.51 |
| Curve 5-hazard Limit | 1.30 |
S3, natural frequency calculation and resonance analysis are carried out on the pipeline structure
And calculating the inherent frequency of the pipeline structure based on a Modal module in ANSYS Workbench software to obtain the inherent frequencies of the front 10 orders of the air inlet pipeline, the air outlet pipeline, the safety diffusing pipeline and the sewage discharge pipeline of the compressor. The results of the calculations are shown in tables 6 to 9.
TABLE 6 natural frequency of the first 10 th order of the inlet duct
| Order of the |
1 | 2 | 3 | 4 | 5 |
| Frequency (Hz) | 10.512 | 11.23 | 12.505 | 16.362 | 22.194 |
| Order of the |
6 | 7 | 8 | 9 | 10 |
| Frequency (Hz) | 30.498 | 34.215 | 36.537 | 56.26 | 68.544 |
TABLE 7 natural frequency of the first 10 th order of the outlet duct
| Order of the |
1 | 2 | 3 | 4 | 5 |
| Frequency (Hz) | 9.1687 | 14.37 | 20.127 | 24.064 | 37.729 |
| Order of the |
6 | 7 | 8 | 9 | 10 |
| Frequency (Hz) | 41.91 | 47.008 | 58.972 | 78.36 | 85.906 |
TABLE 8 safe dissipation of the first 10 natural frequencies of the pipeline
| Order of the |
1 | 2 | 3 | 4 | 5 |
| Frequency (Hz) | 56.32 | 78.375 | 80.646 | 102.88 | 121.47 |
| Order of the |
6 | 7 | 8 | 9 | 10 |
| Frequency (Hz) | 128.61 | 152.79 | 153.06 | 156.27 | 166.01 |
TABLE 9 Natural frequency of the first 10 th order of the sewer
| Order of the |
1 | 2 | 3 | 4 | 5 |
| Frequency (Hz) | 10.098 | 11.459 | 14.974 | 15.619 | 18.754 |
| Order of the |
6 | 7 | 8 | 9 | 10 |
| Frequency (Hz) | 21.95 | 23.872 | 31.61 | 35.447 | 40.848 |
The calculation result shows that the sixth order (30.498Hz) and the seventh order (34.215Hz) of the natural frequency of the air inlet pipeline structure are in the resonance range, the pipeline can generate structural resonance, the 4 th order (24.064Hz) of the natural frequency of the outlet pipeline structure is in the resonance range, the pipeline can generate structural resonance, the natural frequency of the safe diffusing pipeline structure is not in the resonance range, the pipeline cannot generate structural resonance, the seventh order (23.872Hz) and the eighth order (31.61Hz) of the natural frequency of the sewage pipeline structure are in the resonance range, and the pipeline can generate structural resonance.
The natural frequency of the air column is calculated by adopting a Model Acoustics module in ANSYS Workbench software. The calculation results are shown in tables 10 to 13.
TABLE 10 inherent frequency of the first ten-step gas column of the intake duct
| Order of the |
1 | 2 | 3 | 4 | 5 |
| Frequency (Hz) | 18.991 | 37.993 | 57.058 | 76.031 | 95.044 |
| Order of the |
6 | 7 | 8 | 9 | 10 |
| Frequency (Hz) | 108.17 | 113.94 | 133. | 151.95 | 171.06 |
TABLE 11 inherent frequency of the first ten stages of gas column in the outlet duct
| Order of the |
1 | 2 | 3 | 4 | 5 |
| Frequency (Hz) | 18.616 | 30.464 | 43.319 | 57.36 | 66.678 |
| Order of the |
6 | 7 | 8 | 9 | 10 |
| Frequency (Hz) | 78.28 | 91.933 | 106.07 | 116.02 | 132.5 |
TABLE 12 safe bleeding of the first ten-step gas column natural frequency of the pipeline
| Order of the |
1 | 2 | 3 | 4 | 5 |
| Frequency (Hz) | 45.848 | 49.853 | 111.53 | 117.1 | 168.06 |
| Order of the |
6 | 7 | 8 | 9 | 10 |
| Frequency (Hz) | 174.85 | 180.71 | 180.76 | 182.71 | 182.73 |
TABLE 13 inherent frequency of the first ten-step gas column of the blow-down pipe
| Order of the |
1 | 2 | 3 | 4 | 5 |
| Frequency (Hz) | 15.901 | 15.902 | 16.753 | 17.66 | 20.421 |
| Order of the |
6 | 7 | 8 | 9 | 10 |
| Frequency (Hz) | 40.1 | 45.936 | 48.65 | 74.121 | 74.138 |
The calculation result shows that the air inlet pipeline of the compressor does not resonate; the natural frequency (30.464Hz) of the second-stage air column of the outlet pipeline is just in the resonance range, and the outlet pipeline can generate air column resonance; the natural frequency of the gas column of the safe diffusion pipeline is gradually increased from the first order to the tenth order, the natural frequency of the gas column of the first order of the pipeline is far greater than the maximum value (35.1Hz) of the resonance range, the natural frequency from the second order to the tenth order cannot fall into the resonance range, and the pipeline cannot generate gas column resonance; the compressor blow-off pipe will not resonate.
The resonance analysis is summarized from the above and is shown in Table 14.
TABLE 14 summary of resonance analysis
| Name of pipeline | Whether or not gas column resonance occurs | Whether or not structural resonance occurs | Remarks for note |
| Air inlet pipeline | Whether or not | Is that | 5 th and 6 th order |
| Outlet duct | Is that | Whether or not | 2 nd order |
| Safe diffusion pipeline | Whether or not | Whether or not | / |
| Sewage pipes | Whether or not | Is that | 7 th and 8 th order |
And S4, performing bidirectional transient fluid-solid coupling between the gas in the pipeline and the pipeline, monitoring the displacement condition and the gas pulsation condition of the pipeline, and checking the compressor pipeline according to the API618 specification.
The pressure pulsation of the fluid in the pipe can cause the vibration of the pipeline system, and in order to ensure the working reliability of the compressor and the connecting pipeline thereof, the stress distribution of the pipeline system and the deformation of the pipeline caused by the airflow pulse force need to be analyzed, and the analysis of the stress borne by the pipeline and the amplitude of the pipeline is called pipeline dynamic characteristic analysis. The analysis is shown in fig. 8 to 19.
In the running process of the compressor, gas in the pipeline and the pipeline are mutually influenced, the actual conditions of corners and variable diameters of the compressor pipeline are more, and the gas flow can influence the pipeline to cause pipeline deformation; meanwhile, the gas in the pipeline is regarded as an elastic body with quality, and the deformation of the pipeline can also adversely affect the gas.
The method is characterized in that bidirectional Transient Fluid-solid coupling is performed based on a Transient Structural (ANSYS) module and a Fluid Flow (Fluid) module in ANSYS Workbench software, the displacement condition and the gas pulsation condition of a pipeline are monitored, and a compressor piping system is checked according to the API618 specification. The checking results are shown in Table 15.
TABLE 15 compressor piping dynamics and verification results
S5 provides a vibration control method for compressor piping
(1) Avoiding structural resonance:
the basic methods for changing the natural frequency of the structure are as follows: 1. increasing or decreasing the number of supports; 2. the supporting mode is changed.
According to the analysis and calculation of the previous steps, the natural frequency of the pipeline structure is changed by adding the pipe clamps, and the distance between the pipe clamps is reduced by adding the pipe clamps on the basis of unchanged positions of the pipe clamps (as shown in FIG. 20) (as shown in FIG. 21).
The purpose of adding the pipe clamp is to increase the radial constraint of the pipe. Modal analysis is performed on the air inlet pipeline with the increased number of supports. And (4) importing the pipeline model into ANSYS Workbench software, and carrying out grid division and constraint setting on the pipeline model to finally obtain the first 10-order natural frequency of the pipeline.
Table 16 shows the natural frequency values of the front ten-step structure of the optimized intake duct and the contrast-increased values before optimization.
TABLE 16 increasing the front 10 th order natural frequency of the inlet duct behind the pipe clamp
The comparison curve of the natural frequency results of the first 10 th order of the pipeline before and after optimization is shown in FIG. 22. In fig. 22, the abscissa represents the natural frequency order of the intake duct structure, ranging from 1 to 10 orders; the ordinate represents the natural frequency value; the blue diamond-shaped marked curve is a structural natural frequency change curve before optimization of the air inlet pipeline, and it can be seen that the 6 th and 7 th order structural natural frequencies are in a resonance range before optimization, and the pipeline can generate structural resonance; the yellow square marked curve is a ten-order natural frequency change curve before the optimized air inlet pipeline, and the natural frequencies of the ten-order structure before the optimized air inlet pipeline are not in the resonance range, so that the pipeline resonance is avoided, and the optimization is successful.
(2) Avoiding air column resonance:
the basic methods for changing the shape of the gas column are: 1. changing the diameter and the length of the pipeline; 2. changing the angle of the pipe corner, such as changing a 90-degree right-angle turn into a 45-degree turn; 3. adding a buffer and a buffer tank; 4. a header is added.
For the outlet pipeline of the compressor of a certain CNG gas station in the example, the method for increasing the buffer tank is not feasible due to the fact that the pipeline is short in length and small in pipe diameter. Changing the diameter of the manifold can be used to change the natural frequency of the gas column.
Obtaining a pipeline wall thickness calculation formula according to gas transmission pipeline engineering design specifications (GB 50251-2015):
in the formula:
delta-pipe calculated wall thickness, cm;
p is design pressure (gauge pressure), MPa;
d, the outer diameter of the pipeline is mm;
σsthe minimum yield strength of the steel pipe is 245MPa for 20# steel;
f, strength design coefficient (related to regional grade), 0.4 is taken;
t is the temperature reduction coefficient, and when the temperature is less than 120 ℃, 1 is taken.
The diameter of the outlet pipeline is phi 22 multiplied by 3.5, three optimization schemes are provided, the outer diameters of the pipelines of the optimization schemes 1 to 3 are 1, 2 and 3 grades higher than the outer diameter of the original outlet pipeline, the wall thickness of the pipeline is calculated by using a formula 5-1, and after the outer diameter and the minimum wall thickness of the pipeline are confirmed, the size of the manifold in the optimization schemes 1 to 3 is selected according to the outer diameter and the wall thickness of the common steel pipe in table 1 in the seamless steel pipe size, shape, weight and allowable deviation (GB/T17395-2008). The outer diameter and wall thickness dimensions of the pipes in schemes 1-3 are shown in Table 17.
The optimization schemes 1-3 are shown in the pipeline model diagrams in figures 23-25.
And respectively carrying out modal analysis on the three optimized outlet pipelines. And (4) guiding the pipeline model into ANSYS Workbench software, and carrying out grid division and constraint setting on the pipeline model to finally obtain the first 10-order natural frequency of the gas column. Tables 18-20 show the values of the natural frequency of the first ten-step gas column of the outlet pipeline after optimization in the optimization schemes 1, 2 and 3 and the amplitude increase values before optimization.
TABLE 18 optimization scheme 1 gas column first 10 th order natural frequency
| Order of the |
1 | Amplification of | 2 | Amplification of | 3 | Amplification of | 4 | Amplification of | 5 | Amplification of |
| Frequency (Hz) | 21.651 | 16.3％ | 32.156 | 5.55％ | 45.169 | 4.27％ | 68.148 | 18.8％ | 79.186 | 18.8％ |
| Order of the |
6 | Amplification of | 7 | Amplification of | 8 | Amplification of | 9 | Amplification of | 10 | Amplification of |
| Frequency (Hz) | 95.18 | 21.6％ | 113.25 | 23.2％ | 135.12 | 27.4％ | 146.25 | 26％ | 163.12 | 23.1％ |
TABLE 19 optimization scheme 2 gas column first 10 th order natural frequency
| Order of the |
1 | Amplification of | 2 | Amplification of | 3 | Amplification of | 4 | Amplification of | 5 | Amplification of |
| Frequency (Hz) | 40.21 | 116％ | 45.231 | 48.5％ | 61.236 | 41.4％ | 82.12 | 43.2％ | 95.13 | 42.7％ |
| Order of the |
6 | Amplification of | 7 | Amplification of | 8 | Amplification of | 9 | Amplification of | 10 | Amplification of |
| Frequency (Hz) | 116.232 | 48.5％ | 145.23 | 58.0％ | 167.21 | 58.0％ | 170.36 | 46.8％ | 203.64 | 53.7％ |
TABLE 20 optimization scheme 3 gas column first 10 th order natural frequency
| Order of the |
1 | Amplification of | 2 | Amplification of | 3 | Amplification of | 4 | Amplification of | 5 | Amplification of |
| Frequency (Hz) | 45.32 | 143％ | 59.462 | 95.1％ | 82.169 | 89.7％ | 113.25 | 97.4％ | 129.23 | 93.8％ |
| Order of the |
6 | Amplification of | 7 | Amplification of | 8 | Amplification of | 9 | Amplification of | 10 | Amplification of |
| Frequency (Hz) | 139.32 | 78.0％ | 169.21 | 84％ | 189.32 | 78.5％ | 190.21 | 64.0％ | 236.21 | 78.3％ |
The comparison curve of the natural frequency results of 10 orders before the air column in the optimization schemes 1-3 is shown in FIG. 26.
In fig. 26, the abscissa represents the number of orders of the natural frequency of the outlet pipe gas column, ranging from 1 to 10 orders; the ordinate represents the natural frequency value; the blue diamond-shaped marked curve is a structural natural frequency change curve before optimization of the air inlet pipeline, and it can be seen that the natural frequency of the 2 nd-order structure before optimization is in a resonance range, and the pipeline can generate air column resonance; orange squares, gray triangles and yellow multiplied-shaped marking curves are first ten-order natural frequency change curves of optimization schemes 1, 2 and 3, and it can be seen that after the optimization scheme 1 is optimized, the 1 st order and the 2 nd order of natural frequency of an outlet pipeline gas column are still in a resonance range, and the optimization is unsuccessful; after the optimization schemes 2 and 3 are optimized, the natural frequency of the front ten-order gas column of the outlet pipeline is not in the resonance range, so that the pipeline resonance is avoided, and the optimization is successful.
The calculation result can obtain an optimized scheme 2, namely the size of the header is phi 38 multiplied by 4, and the air column resonance can be effectively avoided. In general, the natural frequency of each stage of the air column in the optimization schemes 1-3 is higher than that of the air column before optimization, and the natural frequency of the air column in the optimization scheme 2 obviously avoids the resonance range of a compressor pipeline system from 23.4Hz to 35.1 Hz. And can derive from the comparison graph of the natural frequency of the gas column of the first ten grades of scheme 1-3, the straight tube section of the same length, the larger the pipeline internal diameter is, the higher the natural frequency of the gas column is, thereby avoid the resonance range, avoid the gas column to produce resonance, guaranteed the safe operation of compressor pipe-line system.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (5)
1. A vibration reduction method for a pipeline system of a reciprocating compressor of a CNG gas station is characterized by comprising the following steps:
s1, establishing a reciprocating compressor model, and verifying the grid independence of an air inlet pipeline outlet pipeline, a safety diffusing pipeline and a sewage discharge pipeline;
s2, providing a vibration check standard of a CNG compressor piping system and checking the standard according to resonance;
s3, calculating the natural frequency of the pipeline structure and the gas column and carrying out resonance analysis;
s4, performing bidirectional transient fluid-solid coupling between gas in the pipeline and the pipeline, monitoring the displacement condition and the gas pulsation condition of the pipeline, and checking the compressor pipeline according to the API618 specification;
s5, specific application measures for eliminating the structural resonance and the air column resonance are provided. The method specifically comprises the following substeps:
s51, avoiding structural resonance measures;
and S52, avoiding air column resonance measures.
2. A method for damping vibration in a CNG gas station reciprocating compressor pipeline according to claim 1, wherein the calibration criteria provided in step S2 are: performing resonance checking standard; checking the standard of airflow pulsation; and stress checking and amplitude checking.
3. A method of damping vibration in a pipe of a reciprocating compressor of a CNG gas station as claimed in claim 1, wherein the resonance analysis of step S2 is performed by calculating and performing resonance analysis on the pipe system based on ANSYS finite element software.
4. A method of damping vibration in a CNG gas station reciprocating compressor pipe according to claim 1, wherein the method of step S5 is: the objective is to avoid structural and gas column resonances, including increasing the pipe clamp and increasing the internal diameter of the manifold.
5. A method for damping vibration in a pipeline of a reciprocating compressor of a CNG gas station as claimed in claim 1, wherein in step S1, a flow simulation software Solidworks is used to create a model based on a pipe section in a pipe trench of a compressor room most affected by vibration of the compressor.
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