CHINESE JOURNAL OF SHIP RESEARCH， VOL.14， NO.4，AUG 2019 To cite this article： Lou J J, Li B, Zhang Z H, et al. Dynamic analysis on star type compressor based on cylinder pressure signal[J/ OL]. Chinese Journal of Ship Research, 2019, 14(4). http://www. ship-research.com/EN/Y2019/V14/I4/104. DOI ： 10.19693/j.issn.1673-3185. 01308 Received： 2018 - 08 - 02 Supported by: National Natural Science Foundation of China (51509253) Authors: Lou Jingjun, male, born in 1976, Ph.D., professor, doctoral supervisor. Research interest: vibration and noise control of ship power plant. E-mail: [email protected]Li Chaobo, male, born in 1989, Ph.D. candidate. Research interest: vibration and noise control of ship power plant. E-mail: [email protected]*Corresponding author： Li Chaobo Dynamic analysis on star type compressor based on cylinder pressure signal Lou Jingjun 1 ， Li Chaobo *2 ， Zhang Zhenhai 1 ， Ning Ronghui 2 1 College of Naval Architecture and Ocean Engineering， Naval University of Engineering， Wuhan 430033， China 2 College of Power Engineering， Naval University of Engineering， Wuhan 430033， China Abstract：［Objectives ］ For star type multistage high-pressure reciprocating compressor, the change of cylinder pressure under different working conditions has not been mastered accurately, and the related dynamic analysis can only be calculated on the basis of theoretical value. Measurement of the actual cylinder pressure of the compressor is helpful to improve the accuracy of the dynamic analysis of the star type compressor. ［Methods ］In this paper， on the premise of not damaging the cylinder structure， each cylinder pressure under different working conditions is successfully measured by the valve stem drilling method， and the vibration acceleration of the cylinder head and base is tested. and the self-balance performance of compressor has good for second-order inertia force is obtained by theoretical analysis. The crank connecting rod mechanism is simplified to establish ADAMS dynamic model ， and the parameterized design method is used to obtain the optimum balance weight. Under the working condition of 25 MPa exhaust pressure， the measured gas force is converted into a force applied to the piston and then loaded on the piston centroid，and then the force of the main bearing is obtained. ［Results ］The results show that the stress of the main bearing is the first-order and three-order inertia forces， the change of the compressor working condition mainly affects the three-stage and four-stage cylinder pressures， and the vibration of the first cylinder is relatively severe. ［Conclusions ］The crank connecting rod mechanism of the compressor has good self-balance. The test results provide reference for mastering the characteristics of the cylinder pressure of the star type compressor and analyzing the vibration characteristics of the compressor. Key words： compressor； cylinder pressure； vibration acceleration level； ADAMS model； balance weight CLC number: U664.5 + 1 0 Introduction Reciprocating compressors are widely used in pe⁃ troleum, chemical, metallurgical and shipping indus⁃ tries due to their high exhaust pressure, wide output pressure coverage and low manufacturing accuracy requirements [1] . A reciprocating compressor is often regarded as the "heart" of ship's pneumatic system. The compressed air produced by it is mainly used to start the diesel engine and astern stop for the ship, strengthen the adjacent cabin after sea damage, and blow off various pipe valves. Most of the special ships use multistage series reciprocating compres⁃ sors, and their models are diverse [2] . The star type re⁃ ciprocating compressor has been gradually applied due to its compact structure, reasonable dynamic de⁃ sign and low vibration [3] . Although relevant models have been put into production in China, relevant the⁃ oretical research is still in its infancy. The moving parts of the star type compressor use the crank connecting rod mechanism to convert the mechanical energy into gas pressure energy, which is the reverse process for the internal combustion en⁃ gine. However, star type compressor has lower cylin⁃ der arrangement requirements than internal combus⁃ tion engine. This type of compressor taking the ad⁃ 62 downloaded from www.ship-research.com
Transcript
CHINESE JOURNAL OF SHIP RESEARCH，VOL.14，NO.4，AUG 2019To cite this article：Lou J J, Li B, Zhang Z H, et al. Dynamic analysis on star type compressor based on cylinder pressure signal[J/
OL]. Chinese Journal of Ship Research, 2019, 14(4). http://www. ship-research.com/EN/Y2019/V14/I4/104.DOI：10.19693/j.issn.1673-3185. 01308
Received：2018 - 08 - 02Supported by: National Natural Science Foundation of China (51509253)Authors: Lou Jingjun, male, born in 1976, Ph.D., professor, doctoral supervisor. Research interest: vibration and noise control of
ship power plant. E-mail: [email protected] Chaobo, male, born in 1989, Ph.D. candidate. Research interest: vibration and noise control of ship power plant.E-mail: [email protected]
*Corresponding author：Li Chaobo
Dynamic analysis on star type compressorbased on cylinder pressure signal
1 College of Naval Architecture and Ocean Engineering，Naval University of Engineering，Wuhan 430033，China2 College of Power Engineering，Naval University of Engineering，Wuhan 430033，China
Abstract：［Objectives］ For star type multistage high-pressure reciprocating compressor, the change of cylinderpressure under different working conditions has not been mastered accurately, and the related dynamic analysis canonly be calculated on the basis of theoretical value. Measurement of the actual cylinder pressure of the compressor ishelpful to improve the accuracy of the dynamic analysis of the star type compressor.［Methods］In this paper，on thepremise of not damaging the cylinder structure， each cylinder pressure under different working conditions issuccessfully measured by the valve stem drilling method，and the vibration acceleration of the cylinder head and baseis tested. and the self-balance performance of compressor has good for second-order inertia force is obtained bytheoretical analysis. The crank connecting rod mechanism is simplified to establish ADAMS dynamic model，and theparameterized design method is used to obtain the optimum balance weight. Under the working condition of 25 MPaexhaust pressure，the measured gas force is converted into a force applied to the piston and then loaded on the pistoncentroid，and then the force of the main bearing is obtained.［Results］The results show that the stress of the mainbearing is the first-order and three-order inertia forces，the change of the compressor working condition mainly affectsthe three-stage and four-stage cylinder pressures，and the vibration of the first cylinder is relatively severe.［Conclusions］The crank connecting rod mechanism of the compressor has good self-balance. The test results providereference for mastering the characteristics of the cylinder pressure of the star type compressor and analyzing thevibration characteristics of the compressor.Key words：compressor；cylinder pressure；vibration acceleration level；ADAMS model；balance weightCLC number: U664.5+1
0 Introduction
Reciprocating compressors are widely used in pe⁃troleum, chemical, metallurgical and shipping indus⁃tries due to their high exhaust pressure, wide outputpressure coverage and low manufacturing accuracyrequirements [1]. A reciprocating compressor is oftenregarded as the "heart" of ship's pneumatic system.The compressed air produced by it is mainly used tostart the diesel engine and astern stop for the ship,strengthen the adjacent cabin after sea damage, andblow off various pipe valves. Most of the specialships use multistage series reciprocating compres⁃
sors, and their models are diverse [2]. The star type re⁃ciprocating compressor has been gradually applieddue to its compact structure, reasonable dynamic de⁃sign and low vibration[3]. Although relevant modelshave been put into production in China, relevant the⁃oretical research is still in its infancy.
The moving parts of the star type compressor usethe crank connecting rod mechanism to convert themechanical energy into gas pressure energy, which isthe reverse process for the internal combustion en⁃gine. However, star type compressor has lower cylin⁃der arrangement requirements than internal combus⁃tion engine. This type of compressor taking the ad⁃
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vantage of the cylinder arrangement can effectivelybalance its second-order inertia force while ensuringthe output pressure, so that the compressor vibrationcan be reduced to some extent [4]. Because the com⁃pressor cylinder has high temperature and high pres⁃sure environment (the highest pressure can reachmore than 20 MPa, and the general maximum pres⁃sure of the internal combustion engine will not ex⁃ceed 10 MPa), the requirements on sensor and seal⁃ing conditions are high to effectively measure the cyl⁃inder pressure.
In China, the research on reciprocating compres⁃sors mostly focuses on the dynamic characteristics ofcrankshaft [5], dynamic balance [6], joint clearance [7]
and so on. During the operation of the compressor,the load on the main bearing changes periodically, socrankshaft bending and torsional vibration are gener⁃ated, which directly affects the safety and stability ofthe whole machine. This phenomenon is more obvi⁃ous in multi-row and high-speed compressors [8]. Dy⁃namic balance is a common problem in the study ofcrank connecting rod mechanism. The most basicmethod is to use the balance weight to eliminate partof the inertia force. There is also a method of usingbalance shaft. If the second-order inertia force isneeded to be fully balanced, the twin balancer shaftssystem would be required [9]. However, due to the bal⁃ance shaft has high cost, complicated structure andlarge occupied space, the balance weight method isusually adopted. The joint clearance is a researchhotspot in recent years [10]. The research mainly focus⁃es on the effects of kinematic pair materials, axial di⁃mension, modeling method, clearance size, collisionand friction on its dynamic characteristics, but the re⁃lated research is still in theory stage [11–14].
In this study, the HTT-04CA cylinder pressuresensor and the valve stem drilling method were usedto measure the curve of cylinder pressure with crankangle under different working conditions. Throughtheoretical derivation and establishment of ADAMSdynamic model, the influences of the inertia forceand balance weight of the main bearing on the bear⁃ing capacity of the main shaft were analyzed. Themeasured cylinder pressure signal was used and itscycle was extended to construct the SPLINE curvewith a certain time domain length which was thenloaded onto the centroid of each piston of the AD⁃AMS dynamic model. The force condition of themain bearing was simulated and analyzed. The vibra⁃tion test data of the cylinder head and the base wereanalyzed to study the vibration of the measuring
points of the whole machine.1 Air compressor structure
This type of compressor has a single-acting verti⁃cal star type structure, which adopts water-coolingand four-stage compression. The cylinders of differ⁃ent stages are centered on the vertical crankshaft,and are arranged in a 90° star shape. The connectingrods of different levels are arranged side by side onthe same crank pin, so as to shorten the length of thecrankshaft and increase the natural frequency of thecrankshaft, thus making the whole machine morecompact. Wherein, the one-stage and two-stage cyl⁃inders are symmetrically arranged with three-stageand four-stage cylinders, respectively, and theone-stage and two-stage connecting rods are locatedat both ends of the crank to furthest balance ofself-inertia force. The body is mounted on the basethrough the crankcase bracket. The crank connectingrod mechanism and the cylinder distribution areshown in Fig. 1. When the compressor is working,the motor drives the crankshaft to rotate through theelastic coupling, and the connecting rod drives thepiston to reciprocate. The air is filtered by the intakesilencer and then enters the one-stage cylinder. Thecompressed gas is cooled by the cooler, enters theoil-water separator, and then successively enters thenext-stage cylinder for compression, cooling, andseparation. After the compression by the four-stagecylinder, the compressed gas is exhausted from the fi⁃nal-stage outlet. The cylinders of different stagescomplete the four processes of aspiration-compres⁃sion-exhaust-expansion in sequence.
Motor
Machine legBase
Vibrationisolator
Three-stage
Two-stage
Four-stage
One-stage
yz
x
x
Fig.1 Schematic diagrams for the distribution of the crankconnecting rod mechanism and cylinder
Two-stage
Three-stage One-stage
Four-stage
90°
（a）Fornt view of compressor body （b）Top view of compressor body
（c）Three-dimensional diagramof crank three-rod
（d）Top view of the crankconnecting rod
Lou J J, et al. Dynamic analysis on star type compressor based on cylinder pressure signal 63
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CHINESE JOURNAL OF SHIP RESEARCH，VOL.14，NO.4，AUG 2019
2 Crank connecting rod mechanism
2.1 Inertia force and moment
The schematic diagram of the Cartesian coordi⁃nates of the crank connecting rod mechanism isshown in Fig. 2 (where φ3 is the angle between thecenterlines of cylinders in adjacent two stages). Thenthe first-order reciprocating inertia force can be cal⁃culated as follows:
F 1xs = m srω
2 cos θ sin 0 + m srω2 cos(θ - π)sin π +
m srω2 cos(θ + π
2)sin(- π
2) + m srω
2 cos(θ - π2
)sin π2=
2m srω2 sin θ
F1y
s = m srω2 cos θ cos 0 + m srω
2 cos(θ - π)cos π +
m srω2 cos(θ + π
2)cos(- π
2) + m srω
2 cos(θ - π2
)cos π2=
2m srω2 cos θ
F 1s = (F 1x
s )2 + (F1y
s )2 = 2msrω2 （1）
where m s is the reciprocating mass, r is the crank ra⁃dius, ω is the crank angle velocity, and θ is thecrank angle.
The inertia force of the crank connecting rodmechanism acting on the main bearing is subjectedto Taylor series expansion. The index n is the orderof the inertia force. In general, only the inertia forcein the first two orders is considered. The calculationformula of angle θ1 between the y -axis and thefirst-order reciprocating inertia force is shown as be⁃low:
θ1 = arctanF 1x
s
F1y
s
= θ （2）The first-order reciprocating inertia moment can
be calculated as follows:M 1x
s = - a2
m srω2 sin θ + a
2m srω
2 sin θ = 0 （3）M
1y
s = - 3a2
m srω2 sin θ + 3a
2m srω
2 sin θ = 0（4）
M 1s = (M 1x
s )2 + (M1y
s )2 = 0 （5）In theory, the balance weight can be increased to
balance the first-order inertia force and the moment.Similarly, the second-order reciprocating inertiaforce and moment can be calculated as below:
F 2s = 0 （6）
M 2s = (M 2x
s )2 + (M2y
s )2 = 10 aλm srω2 cos 2θ（7）
where λ is the length ratio of the crank connectingrod and a is the axial distance of the adjacent twocolumns of connecting rods. Since the spacing a be⁃tween the columns is small, the second-order inertiamoment is also small, and the first-order reciprocat⁃ing inertia force is mainly considered when balanc⁃ing the reciprocating inertia force.2.2 ADAMS dynamic model
The crank connecting rod mechanism of this typeof compressor has a total of 113 parts, which are com⁃bined into a total of 9 parts of 4 pistons, 4 connectingrods and 1 crankshaft based on the Boolean opera⁃tion through CATIA, and the oil holes, chamfers andother details of the model are removed. Since the da⁃ta exchange between CATIA and ADAMS is not veryconvenient, after saving the CATIA model as a stpformat file, we could import it into PROE and saveas *. x_t format file, thereby obtaining the Parasolidentity. The entity is imported into ADAMS/View andthe mass attribute is defined. The different parts areconnected by the prismatic pair and revolving pairand fixed by the balance iron and crankshaft. Thecrankshaft drive is added to obtain a rotation speedof 1 480 r/min. The dynamic model is shown inFig. 3 [15-16]. The piston mass is defined as 5 kg; thecrankshaft and connecting rod are obtained based onthe steel material property; the crankshaft mass is33 kg; the mass of the one-stage and two-stage con⁃necting rods is 3.96 kg; the mass of the three-stageand four-stage connecting rods is 3.98 kg.
Fig.2 Cartesian coordinates of the crank connecting rodmechanism
1432
O
a2
a
O
3
2
4
1y
x
θ
ω
φ3
（a）Schematic diagram ofcrank structure
（b）Schematic diagram ofconnecting rod motion
y
zx
Fig.3 ADAMS dynamic model of the crank connecting rodmechanism
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Each component is defined as a rigid body, andthe shape and position of the balance iron remain un⁃changed relative to the crankshaft. Considering thesymmetry of the star type arrangement, the minimumforce of the main bearing in the x direction is theoptimization target, and the change of the balanceweight with the force loaded on the main bearing inthe x direction is shown in Fig. 4 (a). With the in⁃crease in the balance weight m, the force Fx on themain bearing in the x direction first decreases andthen increases. The theoretical optimum mass is5.65 kg, which can minimize the force on the mainbearing in x direction. In the case where the opti⁃mum balance weight is obtained, the frequency do⁃main diagram of the force on the crankshaft revolv⁃ing pair is shown in Fig. 4 (b). Since the three-stageand four-stage connecting rods are 0.02 kg heavierthan the one-stage and two-stage connecting rods,the second-order inertia force is not completely bal⁃anced but smaller than the first-order and third-or⁃der inertia force.
3 Cylinder pressure test
3.1 Test plan
The main equipment for this compressor cylinderpressure test includes cylinder pressure sensors, a24 V DC power supply, an NI data acquisition cardand a notebook computer. Due to the interface issue
between sensor and acquisition card, a channel con⁃necting BNC connector and a 500 Ω precision resis⁃tor are also required. In order to avoid the channel ef⁃fect during the cylinder pressure collection process,we place the pressure sensor on the top of the facingpiston, and it is measured after the high pressure gasis taken out from the hole drilled from the valvestem. The sensor arrangement is shown in Fig. 5.Starting from 5 MPa, every 5 MPa is set as one work⁃ing condition till reaching 25 MPa. In other words, atotal of five working conditions will be measured.Since there are only two cylinder pressure sensors,only two cylinders can operate simultaneously eachtime of data collection, and then stopped for ex⁃change. The four cylinder pressures are connected toeach other, and the real-time correspondence of thefour cylinder pressures is determined by overlappingthe cylinder pressure of one of the cylinders.
3.2 Test data analysis
The exciting force of the complete air compressormainly includes gas force, friction force, gas valveimpact force, piston side thrust and exciting force onmain bearing, among which gas force plays a leadingrole. Although the calculation can be performed bythe relevant formula, the reliability of the calculationneeds to be verified. Cylinder pressure is collectedby pressure sensors to obtain reliable cylinder pres⁃sure values. The cylinder pressure under variousworking conditions is shown in Fig. 6. In theory, thesuction pressure and exhaust pressure of the com⁃pressor remain unchanged, but this is not the case.The suction pressure and exhaust pressure are highlydependent on the performance of the valve.
In the whole test process, the cylinder pressure of
Fig.4 Force diagram of the main bearing in unloaded state
（a）Variation of balance weight
（b）Optimum balance weigth
1 6001 4001 2001 000
800600400200
0
F x/N
3 4 5 6 7m/kg
X:5.65Y:31.89
0 50 100 150 200f/Hz
160140120100
80604020
0
F x/N
X:24.29Y:152
X:74.39Y:42.5
X:48.8Y:10.66
Valve stemLeaf spring
Pressuremeasuringchannel Intake valve hole
Exhaustvalve holeValve seat Upper part of
valve seat
Valve stembolt hole
Valve hole（a）Gas valve profile （b）3D illustration of valve seat
Fig.5 Arrangement of cylinder pressure sensor
Cylinder
Piston Pressuresensor
10 cm
（c）Sensor arrangement plan （d）Sensor installation diagram
Lou J J, et al. Dynamic analysis on star type compressor based on cylinder pressure signal 65
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CHINESE JOURNAL OF SHIP RESEARCH，VOL.14，NO.4，AUG 2019the one-stage cylinder does not change much, andthe maximum cylinder pressure of the two-stage cyl⁃inder is also at 1.4–1.6 MPa. It can be seen that thechange of final exhaust pressure has little influenceon the one-stage and two-stage cylinders. The maxi⁃mum negative pressure of the one-stage cylinder canreach 0.16 MPa under 25 MPa working conditions.In the exhaust stage, the cylinder pressure of thethree-stage and four-stage cylinders fluctuates sig⁃nificantly, mainly because of the high exhaust pres⁃sure, which causes the flutter of the valve. The maxi⁃mum cylinder pressure of the three-stage cylindervaries from 5.7 MPa to 9.2 MPa, while the four-stagecylinder fluctuates greatly with the final exhaustpressure. Under the working condition of 5 MPa,the four-stage cylinder has no effect on raising thegas pressure, while under the working condition of25 MPa, the cylinder pressure of the four-stage cyl⁃inder rises from 6.8 MPa to 25 MPa.4 Dynamics analysis
4.1 Dynamics analysis of crankconnecting rod mechanism
Under 25 MPa working condition, when the cylin⁃der pressure is converted into the gas force on thepiston with the help of the cylinder sectional area,the variation rule of the gas force on the piston withthe crank angle is shown in Fig. 7. The gas force onthe piston is subjected to periodic extension to con⁃struct the SPLINE curve, and it is loaded on the AD⁃AMS model. The time domain curve of force F on themain bearing is shown in Fig. 8. It takes 0.405 s forthe crank connecting rod mechanism to rotate by onecycle, during which the force on the main bearinghas two obvious peaks. This reduces the stress fluctu⁃ation twice compared with the general one-stage tofour-stage cylinder compression. The time domainsignal in Fig. 8 is converted to the frequency domainsignal, and the force curve in the frequency domainof the main bearing is shown in Fig. 9. Since there isa very low frequency component in the signal, whichwill cause the distortion of the low frequency signal,it is unnecessary to pay attention to the force signalbefore the first trough in the frequency domain [17].The main bearing mainly bears the first-order inertiaforce, followed by the third-order inertia force. Dueto the imbalance of the gas force on the piston, thesecond-order inertia force has a certain rise, but it isstill lower than the third-order inertia force, so thisstructure still has a certain inhibitory effect on the
6543210
-1
Cylind
erpres
sure/M
Pa
0 100 200 300Crank angle θ /（°）（a）5 MPa
0 100 200 300Crank angle θ /（°）
1210
86420
-2
Cylind
erpres
sure/M
Pa
（b）10 MPa
0 100 200 300Crank angle θ /（°）（c）15 MPa
15
10
5
0
Cylind
erpres
sure/M
Pa
0 100 200 300Crank angle θ /（°）（d）20 MPa
Fig.6 Variation curves of cylinder pressure under differentworking conditions
second-order inertia force.4.2 Vibration signal analysis
Sensors are arranged on the corresponding cylin⁃der heads in the motion directions of the pistons atall stages, and the time domain curve of vibration sig⁃nals of cylinder head in the test is shown in Fig. 10.It can be seen from the figure that the vibration inten⁃sity of the one-stage cylinder is significantly higherthan those of the other three stages of cylinders. Themain reason is that the cylinder diameter of theone-stage cylinder is large, resulting in insufficientlocal structural rigidity. In addition, the one-stage
cylinder has a large negative pressure in the suctionprocess, and the force situation is complex. Besides,the silencer vibration caused by the suction makesthe vibration of the one-stage cylinder more intensi⁃fied. The frequency domain curve of vibration sig⁃nals of cylinder head is shown in Fig. 11. As can beseen from the figure, the vibration of the one-stagecylinder is mainly concentrated in the high-frequen⁃cy band and not prominent at the low-frequencyband.
The equation of the total vibration level L is as fol⁃lows [18]:
L = 20* lgåi = 1
N
a2i ´ b
a0
（8）where ai is frequency domain acceleration, m/s2; bis the bandwidth of acceleration, m/s2; a0 = 10-6, isthe reference acceleration, m/s2.
The total vibration levels of the 1-4 measuringpoints of machine legs are shown in Table 1. In orderto compare the changing rules of the histogram andthe total vibration level, we subtract 129 dB from theacceleration vibration level of all points (if 129 dB isnot subtracted, the difference of the histogram can⁃
2.01.51.00.5
0-0.5-1.0
Gasforc
eonp
iston/N
0 50 100 150 200 250 300 350Crank angle θ /（°）
Fig.7 Variation curves of the gas force on the piston with thecrank angle
Lou J J, et al. Dynamic analysis on star type compressor based on cylinder pressure signal 67
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CHINESE JOURNAL OF SHIP RESEARCH，VOL.14，NO.4，AUG 2019not be seen by naked eyes). The relationship be⁃tween the reference acceleration level and the work⁃ing condition of the compressor is shown in Fig. 12.Under the same working condition, the maximum dif⁃ference of vibration acceleration levels between themeasuring points of the base is 4.1 dB, indicatingthat the center of gravity of the compressor is offsetfrom the center line of the base. According to theoverall trend, the influence of working condition vari⁃ation on the acceleration level of the base vibrationis no more than 1.8 dB, and the vibration is differentunder the working conditions below 10 MPa (includ⁃ing 10 MPa) and above 10 MPa.
5 Conclusions
In this paper, star type compressor is taken as theresearch object, and cylinder pressure and vibrationacceleration are tested through experiments. Be⁃sides, dynamics analysis of star type compressor iscarried out with the established ADAMS model ofcrank connecting rod mechanism. The following con⁃clusions are drawn:
1) Theoretically, the cylinder arrangement of thistype of compressor can effectively balance the sec⁃ond-order inertia force. Due to the deviation in thedistribution of connecting rod mass, the second-or⁃der inertia force will increase, but it is still less thanthe third-order inertia force.
2) The one-stage cylinder has a large negativepressure during the operation of the compressor, and
its vibration is more violent than that of other cylin⁃ders. The working condition variation of the compres⁃sor has little influence on the cylinder pressure ofone-stage and two-stage cylinders and mainly af⁃fects the cylinder pressure of the three-stage andfour-stage cylinders.
3) Under the low-pressure working condition, fourcylinders have little effect on raising the exhaustpressure, but will aggravate the vibration of the base.Therefore, this type of compressor is not suitable forworking under the condition of less than 10 MPa.The influence of the change in compressor workingcondition on the vibration acceleration level of thebase is not more than 1.8 dB, and the vibration accel⁃eration level of the base is relatively stable in theworking conditions of 15 MPa or above.
4) In this study, test results of cylinder pressureare directly considered reliable within the errorrange. The influence of the length and diameter ofthe pressure measurement channel on the test resultscan be studied later. It requires further analysis ofthe vibration mechanism, and the vibration test re⁃sults should be compared with the finite element sim⁃ulation results.References［1］ Xu Z J. The research on the dynamic characteristics of
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