Compressor Piping Systems Research Articles

Vibroacoustic modeling of a compressor piping system

The paper presents a finite element model of the compressor piping, developed in the Ansys software package using the APDL language. The finite element model was developed taking into account the real conditions of fastening pipeline sections in the form of installed supports. The calculation of the pipeline system began with the calculation of flow pulsations generated by the compressor, which were converted into pressure pulsations. The calculation results in the form of pipe vibration amplitude were obtained for each piping pipeline. The results obtained were compared with the vibration parameters recommended by GOST 32569-2013.

Vibration analysis and reduction optimization study of a reciprocating compressor piping system under multi-boundary coupling

In response to the characteristics of variable working conditions of shale gas extraction, in order to ensure the operational safety of shale gas compressors, this paper takes a certain type of shale gas compressor piping system in Weiyuan as the research object. Based on the plane wave theory and vibration theory, the research on the distribution law of gas pulsation of the piping system and the vibration characteristics under multi-boundary coupling was carried out, and the area of gas pulsation exceeded and the part of amplitude exceeding the piping system were locked. The vibration test of the piping system was carried out and the results showed that the amplitude of the piping system exceeded the standard and the agreement between the test and simulation results was high, which verified the correctness of the simulation model. In response to the problem of excessive vibration of the piping system, orifice plate aperture ratio orthogonal test and piping system structure optimization were carried out. After optimization, the amplitude of gas pulsation and vibration was significantly reduced, and they all met the requirements of the API 618 standard, which reduced the risk of structural damage to the piping system and improved the reliability and safety of the shale gas compressor unit.

Stress and Pressure Pulsation Analysis of Low Temperature Compressor Piping System in LNG Vaporizing Station

LNG (Liquefied Natural Gas) vaporizing stations are usually built in the cities and towns, and the BOG (Boiled Off Gas) pressurizing system is a very important element. In the pressurizing system, the severe vibration of the low-temperature reciprocating compressor may lead to a failure of the pipeline system and the equipment. Therefore, this paper analyzes the stress and pressure pulsation of the BOG compressor piping system in the LNG vaporizing station. The beam model was used to establish the pipe model. The static, harmonic and modal analysis were carried out based on the plane-wave theory and the pressure-fluctuation theory, and the influence factors of support spacing, the settlement of the fulcrum foundation, pipe pressure and elbow angle were analyzed. The main conclusions are as follows: (1) the unbalanced excited force caused by pressure pulsation greatly affects the stress of the exhaust pipe and compressor outlet pipe, and has less influence on the stress of the suction pipe and compressor inlet pipe; (2) although unbalanced excited force is generated in the elbow, it also has an impact on the straight pipe stress; (3) adding an expansion joint to the pipe of the BOG compressor can effectively reduce the stress of the pipe its the displacement, and can increase the flexibility of the pipe.

Dynamic analysis of a reciprocrating compressor piping system

Dynamic analysis of a reciprocrating compressor piping system

Attenuation of pulsations in the reciprocating compressor piping system with an elbow-shaped surge tank

An elbow-shaped surge tank is proposed to suppress the pressure pulsations. The transfer matrix method was developed and the mathematical model was established to predict the distribution of pressure pulsations in the piping system (on which a surge tank was already installed) with an elbow-shaped surge tank. Simulation work of the whole piping system was performed. The results show that the elbow-shaped surge tank has good performance to attenuate the pressure pulsations. The frequency analysis shows that the amplitude for the first pulsation frequency is attenuated to a low level. The impulse response was analyzed to examine the efficiency of suppressing pulsations by using the suppressor. The theoretical analysis showed that there exists the optimal suppression performance when setting the distance between the elbow-shaped surge tank and the existing one. Meanwhile, modifying the ratio of length to diameter with a fixed surge volume could also impact the pressure pulsations. The analysis results can be used as a reference in designing and installing the elbow-shaped surge tank.

Development of a transient gas dynamic model for the simulation of pulsation in reciprocating compressor piping systems

The subject of this paper is to develop a nonlinear transient dynamic model for simulating the pressure pulsation in reciprocating compressor piping systems. The model allows the interaction between the piping response and compressor processes. The two-step Lax–Wendroff method is employed to obtain solutions to the unsteady flow equations at internal points in a pipe, and the Trapezoidal version of the method of characteristics is adopted for handling boundary conditions. The compressor, which serves as a boundary condition for predicting the piping's pressure pulsation, is modeled comprehensively on the basis of the first law of thermodynamics, the valve dynamics assumed as a one-degree-of-freedom system and the flow through valve by introducing an effective area for flow through the valve throat. It is worth to note that, to solve the compressor boundary condition, all the related equations are necessary to be solved simultaneously to obtain the pulsating pressure in the pipe end, pressure variation in the cylinder, valve response, mass flow rate, indicated power, and other compressor performance parameters. Numerical results based on these proposed modeling techniques show a good agreement with previous measured data.

Pulsation attenuation in a reciprocating compressor piping system using a volume-perforated pipe-volume suppressor

A volume-perforated pipe-volume suppressor is introduced to study its performance in attenuating pressure pulsations. On the basis of plane wave theory, the work developed a mathematical model to predict the distribution of pressure pulsations in a reciprocating compressor piping system with the proposed suppressor. The theoretical predictions were verified through experiments and three-dimensional fluid dynamics transient simulations, and good agreements were attained. Results proved that the pressure pulsations were attenuated significantly when the suppressor was used. In the frequency domain, the amplitude at the first pulsation frequency was decreased considerably. Both the perforation and cross-sectional areas of the perforated pipe could influence the attenuating capacity. Given a fixed ratio of perforation area to cross-sectional area, the best damping performance could be obtained by increasing the number of perforated holes and reducing the hole diameter. The geometric recommendations produced in this work are useful to control pulsations and vibrations under different functioning conditions.

Pulsation suppression in a reciprocating compressor piping system using a two-tank element

Gas pulsations excited by reciprocating compressors could introduce severe vibrations and noise in piping systems. When pulsating gas flows through the reducers, the changes in flow characteristics, such as velocity and damping coefficient, will affect the pressure pulsations. To circumvent these constraints, a two-tank element is introduced to control the gas pulsation that is still strong in the piping system with a surge tank. Installing another surge tank to form a two-tank element is more flexible and costs lower than replacing the original surge tank with a larger one. In this work, a theoretical model based on the wave theory was proposed to study the transferring mechanism of gas pulsations in the pipeline with the two-tank element. By considering the damping coefficient and the Mach number, the distributions of the pressure pulsations were predicted by the theoretical model and agreed with the three-dimensional fluid dynamics transient analysis. Three experiments were conducted to prove that the suppression capability of the two-tank element is as good as that of a single-tank element (surge tank) with the same surge volume. The volume optimization of the two-tank element is implemented by selecting the best allocations of the two tanks’ volumes to achieve larger reductions of pressure pulsations. Assuming that the total surge volume is constant, we found that the smaller the volume of the front tank (near the cylinder) is, the lower the pulsation levels are. The optimized result proves that in some conditions the two-tank element could control pulsations better than the single-tank element with the same surge volume.

Effect of a cross-flow perforated tube on pressure pulsation and pressure loss in a reciprocating compressor piping system

This paper experimentally investigates the effects of a cross-flow perforated tube on the pressure pulsation attenuation and pressure loss in a reciprocating compressor piping network, with particular focus on the structure parameters and installation positions. The results demonstrate that significant pressure fluctuation attenuation and less pressure loss in the whole piping system can be achieved when a well-designed cross-flow perforated tube is installed downstream of the pulsating bottle. The pressure pulsation is reduced as the perforated rate decreases and as the perforated tube length increases, while the hole diameter has little effect upon the pulsation attenuation. In the aspect of reducing pressure loss, the perforated rate should be larger than 0.05 and the hole diameter should be larger than 8 mm. In addition, a pressure pulsation computation model based on the linear acoustic wave theory and transfer matrix method is developed to predict the pulsating pressure in compressor piping systems with an installed cross-flow perforated tube. With favorable agreement between the model prediction and the present experimental results (maximum deviation within 6.8%), the predicted pulsating pressure can be attenuated for the reciprocating compressor piping system with various compressor speeds when a cross-flow perforated tube is reasonably designed and installed.

Influence of a tapered cylinder nozzle on pressure pulsations in a variable high-speed reciprocating compressor piping system

This paper investigates the influence of a tapered cylinder nozzle (TCN) on pressure pulsations in a high-speed reciprocating compressor piping system. Numerical methods, the 3D frequency-domain finite element method (FEM) and the 3D time-domain computational fluid dynamics (CFD) were used to separately calculate gas column natural frequencies and pressure pulsations. With favorable agreement between model predictions and experimental data, it is concluded from predictions that an installed TCN changes both the values and distribution of frequencies because installation of a TCN filter can alter gas column structure in the piping system. The order of frequency dominated by cylinder nozzle response increases sharply as the TCN diameter ratio increases and the TCN length to diameter ratio decreases. Pressure fluctuations can be effectively attenuated in piping system under different functioning conditions, e.g. variable compressor speeds and variable discharge pressures.

Testing and Modeling of an Acoustic Instability in Pilot-Operated Pressure Relief Valves

Pressure relief valves (PRVs) are included as an essential element of many compressor piping systems in order to prevent overpressurization and also to minimize the loss of process gas during relief events. Failure of the valve to operate properly can result in excessive quantities of vented gas and/or catastrophic failure of the piping system. Several mechanisms for chatter and instability have been previously identified for spring-loaded relief valves, but pilot-operated relief valves are widely considered to be stable. In this paper, pilot-operated PRVs are shown to be susceptible to a dynamic instability under certain conditions where valve dynamics couple with upstream piping acoustics. This self-exciting instability can cause severe oscillations of the valve piston, damaging the valve seat, preventing resealing, and possibly causing damage to attached piping. Two case studies are presented, which show damaging unstable oscillations in a field installation and a blowdown rig, and a methodology is presented for modeling the instability by coupling a valve dynamic model with a 1D transient fluid dynamics simulation code. Modeling results are compared with measured stable and unstable operation in a blowdown rig to show that the modeling approach accurately predicts the observed behaviors.

Numerical analysis of gas pulsation attenuation characteristics of a perforated tube in a reciprocating compressor piping system

This paper presents a non-linear mathematical model to simulate the pulsating flow in a compressor piping system with perforated tube geometries. The governing equations are numerically solved by a composite scheme incorporating the two-step Lax–Wendroff method with the trapezoidal integration version of the method of characteristics at the pipe boundaries. The validity of the mathematical model and the methodology was verified by comparing the analytical predictions with experimental results. On basis of the confirmed model, the effects of a perforated tube on pressure pulsations in the piping system were investigated. A further investigation on the effects of the geometrical parameters and compressor functioning conditions was also conducted. The results demonstrated that pressure fluctuations at the compressor cylinder nozzle could be significantly reduced with a ratio of 53.1% when a perforated tube was installed between compressor and surge volume, but it had little influence on the pressure pulsations in the piping downstream of the surge volume. It is worth mentioning that a longer perforated tube yielded a better damping performance while the hole diameter had little effect on the pressure pulsations. The magnitude to which the perforated tube could damp the pulsations changed under different functioning conditions and the damping capacity was less sensitive to the mean pressure in the piping than to the compressor running speed.

Influence of an orifice plate on gas pulsation in a reciprocating compressor piping system

This paper presents an investigation of the influence of the orifice plate parameters and installation positions on the attenuation of gas pulsation in a reciprocating compressor piping system. The acoustic wave theory and transfer matrix approach were applied to establish the simulation model, in which the valve chamber was assumed to be the pipe–volume–pipe element. Based on the model, the effects of the size and installation positions of the orifice plate on the gas column natural frequencies and pressure pulsation amplitudes were analyzed for the discharge piping system of a two-stage reciprocating air compressor. A test rig was built to validate the simulation results. The gas column natural frequencies and pressure pulsation amplitudes at different locations of the piping system were measured to verify the model. A favorable agreement was noted, with a maximum error of 2.1% for the natural frequencies and 6.3% for the pulsating amplitudes. The influence of the orifice plate on the gas column natural frequency varied according to its position and parameters. The results showed that all orders of natural frequencies decreased slightly as the inner diameter of the orifice plate decreased when the orifice plate was installed downstream of the vessel. However, the distribution of the gas column natural frequency changed when the orifice plate was installed upstream of the vessel. The pressure fluctuations in the piping system could be attenuated substantially by placing an orifice plate of reasonable parameter downstream of the vessel, within a distance of 0.4 m. The degree to which the orifice plate could attenuate the gas pulsation varied under different operating conditions. However, its attenuation effect was more sensitive to the compressor speed than to the discharge pressure.

The Vibration Characteristics Analysis of U-Shaped Pipe Based on Finite Element and Modal Experiment

The U-shaped pipe located in the compressor piping system of the lyophilizer is studied in this paper. Its finite element modal analysis is carried out through the software ABAQUS, and at the same time, the experimental modal analysis is conducted by the software LMS Test.lab and its corollary equipment. Through the comparison between the finite element modal analysis results and the experimental modal results, it can be seen that the two results have good consistence, which verifies that the finite element model is reasonable. This paper provides reference for the further studies of the curving pipe vibration.

Vibration analysis of compressor piping system with fluid pulsation

A piping system connected to a rotary compressor is an essential component for refrigerant transport in air-conditioning systems. The vibration of the pipes has been thought to be generated only by the mechanical forces due to the compressor operation. In this study, the fluid pulsation in the pipe is considered to be a source of the vibration, as well as the mechanical forces by the compressor operation. The mechanical force was first identified experimentally using measured acceleration signals over the shell. The calculation of the fluid force resulting from the pulsating fluid in the pipe was then derived theoretically. The estimation used the pressure pulsation signal in the pipe measured by a pressure transducer. Both sources of the vibration were finally applied to the finite element model of the piping system. Conclusively, the prediction of the vibration response to both sources showed better agreement with the experimental results than prediction considering only the mechanical force. Therefore the theoretical process deriving the fluid force was valid.

Attenuation of Gas Pulsation in a Reciprocating Compressor Piping System by Using a Volume-Choke-Volume Filter

This paper presents an investigation of the use of a volume-choke-volume low-pass filter to achieve gas pulsation attenuation in a reciprocating compressor piping system, with a focus on its frequency response characteristics and influence on the actual attenuation effects. A three-dimensional acoustic model of the gas pulsation was established for a compressor discharge piping system with and without the volume-choke-volume filter, based on which the gas column natural frequencies of the piping system and the pressure wave profiles were predicted by means of the finite element method. The model was validated by comparing the predicted results with the experimental data. The results showed that the characteristic frequency of the filter was sensitive to both diameter and length of the choke but independent of the parameters of the piping beyond the filter. It is worth noting that the characteristic frequency of the filter constituted one order of the gas column natural frequencies of the piping system with the filter. The pressure pulsation levels in the piping system downstream of the filter could be significantly attenuated especially for the pulsation components at frequencies above the filter’s characteristic frequency. The measured peak-to-peak pressure pulsation at the outlet of the filter was approximately 61.7% lower than that of the surge bottle with the same volume.

Vibration Analysis and Control for Reciprocating Compressor Piping System

Following the adequate model of the reciprocating compressor piping system and the compressor design parameters, operating conditions and gas parameters, the mechanical system of compressor piping, gas-column system, pressure pulsations and of vibration response are numerically simulated. And the main factor bringing to the compressor piping system vibration is identified. A reasonable way to controlling piping vibration is developed to achieve a better efficiency. Keywords: Compressor; Pipe vibration; Vibration Analysis; numerical simulation.

Transient Pressure Loss in Compressor Station Piping Systems

“Dynamic pressure loss” is often used to describe the added loss associated with the time varying components of an unsteady flow through a piping system in centrifugal and reciprocating compressor stations. Conventionally, dynamic pressure losses are determined by assuming a periodically pulsating 1D flow profile and calculating the transient pipe friction losses by multiplying a friction factor by the average flow dynamic pressure component. In reality, the dynamic pressure loss is more complex and is not a single component but consists of several different physical effects, which are affected by the piping arrangement, structural supports, piping diameter, and the level of unsteadiness in the flow stream. The pressure losses due to fluid-structure interactions represent one of these physical loss mechanisms and are presently the most misrepresented loss term. The dynamic pressure losses, dominated at times by the fluid-structure interactions, have not been previously quantified for transient flows in compressor piping systems. A number of experiments were performed by Southwest Research Institute (SwRI) utilizing an instrumented piping system in a compressor closed-loop facility to determine this loss component. Steady and dynamic pressure transducers and on-pipe accelerometers were utilized to study the dynamic pressure loss. This paper describes the findings from reciprocating compressor experiments and the various fluid modeling studies undertaken for the same piping system. The objective of the research was to quantitatively assess the individual pressure loss components, which contribute to dynamic pressure (nonsteady) loss based on their physical basis as described by the momentum equation. Results from these experiments were compared with steady-state and dynamic pressure loss predictions from 1D and 3D fluid models (utilizing both steady and transient flow conditions to quantify the associated loss terms). Comparisons between the fluid model predictions and experiments revealed that pressure losses associated with the piping fluid-structure interactions can be significant and may be unaccounted for by advanced 3D fluid models. These fluid-to-structure losses should not be ignored when predicting dynamic pressure loss. The results also indicated the ability of an advanced 1D Navier–Stokes solution at predicting inertial momentum losses. Correspondingly, the three-dimensional fluid models were able to capture boundary layer losses affected by 3D geometries.

Pulsation Analysis of Reciprocating Compressor Piping System by Convolution Integral.

A method for calculating the pulsation response of reciprocating compressor piping systems using convolution integral is proposed. The method considers the interaction between the valve motion of compressors and the pulsation of piping systems. Compressors are simulated by integrating the deferential equations, and pulsations in piping systems are simultaneously calculated by convolution integrals. Impulse responses of piping systems are evaluated as Fourier transforms of the impedances that are calculated by admittance matrix method including attenuations by mean flow. By this approach, Complex piping systems connected to multiple compressors are easily analyzed. Experiments were carried out with a model piping system that had a reciprocating compressor and a vibrating piston. Impedances of the piping system with mean flows were measured using an accelerometer on the vibrating piston and pressure sensors at the pipes. Predicted impedances and simulated pressures for the piping system were compared with the experimental results and good agreement was obtained.

The acoustic simulation and analysis of complicated reciprocating compressor piping systems, II: Program structure and applications

The main objectives of the investigation reported in this paper, Part II, and its companion paper, Part I, are (a) to provide a formulation, including the mean flow effects and suitable for digital computer automation, of the acoustics of complicated piping systems, and (b) to develop a comprehensive digital computer program for the simulation and analysis of complicated reciprocating compressor piping systems. In this paper, the digital computer program structure and applications of the program developed, written in Fortran IV, are described. It is concluded that the computer program is versatile and user-friendly. It is capable of providing a great deal of information from one set of input data, and is open-ended and modular for updating.