Fast algorithm for calculating the pressure pulsation in a reciprocating compressor system with stepless capacity regulation

2019 ◽  
Vol 233 (6) ◽  
pp. 1280-1291
Author(s):  
Lanlan Yang ◽  
Xiaohan Jia ◽  
Haojie Qi ◽  
Jianmei Feng ◽  
Xueyuan Peng ◽  
...  
Keyword(s):  
Fast Algorithm ◽  
Pressure Pulsation ◽  
Negative Impact ◽  
Dynamic Pressure ◽  
Excitation Frequency ◽  
Pipeline System ◽  
Domain Modeling ◽  
Closing Time ◽  
Delayed Closure ◽  
Good Agreement

Stepless capacity regulation through delayed closure of suction valves plays an important role in energy conservation for reciprocating compressors. Serious gas pulsation usually occurs with a suction valve unloader, and its analysis and suppression is a challenge owing to the varied components of the pulsation excitation under different conditions. In this study, a fast algorithm was proposed to calculate the gas pulsation of a compressor system with stepless capacity regulation and was further incorporated into the frequency-domain modeling of the gas pulsation. A test rig was constructed, and the model was experimentally verified. The dynamic pressure at positions in the suction and discharge valve chambers was measured, as the compressor capacity was varied by changing the closing time of the suction valves. The experimental data were compared with the simulated results and indicated a good agreement. The results showed that the suction valve unloader had a negative impact on the gas pulsation in the suction pipeline system. The pressure pulsation of the main excitation frequency increased in the suction pipeline system and decreased in the discharge pipeline, as the opening time of the suction valve increased.

Pressure Pulsation Analysis of Aircraft Hydraulic Power Pipelines System

2010 ◽  
Vol 97-101 ◽  
pp. 2861-2864 ◽  
Author(s):  
Wei Liu ◽  
Tao Wei ◽  
Zhu Feng Yue
Keyword(s):  
Hydraulic System ◽  
Pressure Pulsation ◽  
Excitation Frequency ◽  
Pipeline System ◽  
Transient Pressure ◽  
Hydraulic Power ◽  
Network Chain ◽  
Output Pressure ◽  
Fluid Network ◽  
Pulsation Model

The output pressure pulsation model for the aircraft hydraulic power pipelines was established by the methods of transfer function and fluid network chain-rules; the dissipation caused by frequency-dependent friction was taken into account. Dynamic characteristics of hydraulic system were discussed in frequency-domain and time-domain respectively, the pumping excitation frequency influenced the frequency-response of hydraulic pipeline system, and several resonance frequency bands were obtained. The inverse fast Fourier transform was applied to simulate the transient pressure pulsation waves under pump starting and steady-running state.

scholarly journals Potentiometric Surfactant Sensor Based on 1,3-Dihexadecyl-1H-benzo[d]imidazol-3-ium for Anionic Surfactants in Detergents and Household Care Products

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3627
Author(s):  
Nikola Sakač ◽  
Dubravka Madunić-Čačić ◽  
Dean Marković ◽  
Lucija Hok ◽  
Robert Vianello ◽  
...  
Keyword(s):  
Anionic Surfactants ◽  
Negative Impact ◽  
Ion Pair ◽  
Two Phase ◽  
Potentiometric Response ◽  
Titration Curves ◽  
Signal Change ◽  
Nernstian Slope ◽  
Good Agreement

A 1,3-dihexadecyl-1H-benzo[d]imidazol-3-ium-tetraphenylborate (DHBI-TPB) ion-pair implemented in DHBI-TPB surfactant sensor was used for the potentiometric quantification of anionic surfactants in detergents and commercial household care products. The DHBI-TPB ion-pair was characterized by FTIR spectroscopy and computational analysis which revealed a crucial contribution of the C–H∙∙∙π contacts for the optimal complex formation. The DHBI-TPB sensor potentiometric response showed excellent analytical properties and Nernstian slope for SDS (60.1 mV/decade) with LOD 3.2 × 10−7 M; and DBS (58.4 mV/decade) with LOD 6.1 × 10−7 M was obtained. The sensor possesses exceptional resistance to different organic and inorganic interferences in broad pH (2–10) range. DMIC used as a titrant demonstrated superior analytical performances for potentiometric titrations of SDS, compared to other tested cationic surfactants (DMIC > CTAB > CPC > Hyamine 1622). The combination of DHBI-TPB sensor and DMIC was successfully employed to perform titrations of the highly soluble alkane sulfonate homologues. Nonionic surfactants (increased concentration and number of EO groups) had a negative impact on anionic surfactant titration curves and a signal change. The DHBI-TPB sensor was effectively employed for the determination of technical grade anionic surfactants presenting the recoveries from 99.5 to 101.3%. The sensor was applied on twelve powered samples as well as liquid-gel and handwashing home care detergents containing anionic surfactants. The obtained results showed good agreement compared to the outcomes measured by ISE surfactant sensor and a two-phase titration method. The developed DHBI-TPB surfactant sensor could be used for quality control in industry and has great potential in environmental monitoring.

The penetration and ricochet of ogive-nosed rigid projectiles obliquely impacting metallic targets

2021 ◽  
pp. 204141962110377
Author(s):  
Yaniv Vayig ◽  
Zvi Rosenberg
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Dynamic Pressure ◽  
Oblique Impacts ◽  
Simulation Results ◽  
The Impact ◽  
Penetration Depths ◽  
Resistance To Penetration ◽  
Good Agreement

A large number of 3D numerical simulations were performed in order to follow the trajectory changes of rigid CRH3 ogive-nosed projectiles, impacting semi-infinite metallic targets at various obliquities. These trajectory changes are shown to be related to the threshold ricochet angles of the projectile/target pairs. These threshold angles are the impact obliquities where the projectiles end up moving in a path parallel to the target’s face. They were found to depend on a non-dimensional entity which is equal to the ratio between the target’s resistance to penetration and the dynamic pressure exerted by the projectile upon impact. Good agreement was obtained by comparing simulation results for these trajectory changes with experimental data from several published works. In addition, numerically-based relations were derived for the penetration depths of these ogive-nosed projectiles at oblique impacts, which are shown to agree with the simulation results.

Analytical and Experimental Simulation of Loose Pedestal Dynamic Effects on a Rotating Machine Vibrational Response

1991 ◽  
Author(s):  
Pavel Goldman ◽  
Agnes Muszynska
Keyword(s):  
Excitation Frequency ◽  
Experimental Studies ◽  
Experimental Simulation ◽  
Physical Parameters ◽  
Vibrational Response ◽  
Rotating Machine ◽  
Qualitative Pattern ◽  
The Impact ◽  
Good Agreement ◽  
Periodic Changes

Abstract This report presents experimental, analytical, and numerical results describing vibrational phenomena in a rotating machine with one loose pedestal. The loose-pedestal machine rotor vibrations represent unbalance-related excited vibrations of synchronous and fractional subsynchronous regimes. In this study the loose-pedestal machine is first simulated by a simple vibrating beam excited by a shaker mounted on it. The shaker simulates an unbalanced machine rotor. The beam occasionally enters in contact with the foundation. The excited vibrations are modified by impacting occurrences, and by periodic changes in system stiffness. A new model of the impact has been developed. The results of analytical and experimental studies stand in a good agreement. They illustrate the existence of the synchronous regime and several subsynchronous fractional regimes in various excitation frequency ranges. The analysis adequately predicts the occurrence of these regimes and determines the physical parameters affecting them. The analytical and experimental results are then compared with the responses of experimental rotor rig with one bearing pedestal looseness. They show the same qualitative pattern.

Aerodynamic Similarity Principles and Scaling Laws for Windmilling Fans

2018 ◽  
Author(s):  
Dilip Prasad
Keyword(s):  
Rotational Speed ◽  
Pressure Loss ◽  
Scaling Laws ◽  
Dynamic Pressure ◽  
Stagnation Pressure ◽  
Design Parameters ◽  
Similarity Parameter ◽  
Wide Range ◽  
Simulation Results ◽  
Good Agreement

Windmilling requirements for aircraft engines often define propulsion and airframe design parameters. The present study is focused is on two key quantities of interest during windmill operation: fan rotational speed and stage losses. A model for the rotor exit flow is developed, that serves to bring out a similarity parameter for the fan rotational speed. Furthermore, the model shows that the spanwise flow profiles are independent of the throughflow, being determined solely by the configuration geometry. Interrogation of previous numerical simulations verifies the self-similar nature of the flow. The analysis also demonstrates that the vane inlet dynamic pressure is the appropriate scale for the stagnation pressure loss across the rotor and splitter. Examination of the simulation results for the stator reveals that the flow blockage resulting from the severely negative incidence that occurs at windmill remains constant across a wide range of mass flow rates. For a given throughflow rate, the velocity scale is then shown to be that associated with the unblocked vane exit area, leading naturally to the definition of a dynamic pressure scale for the stator stagnation pressure loss. The proposed scaling procedures for the component losses are applied to the flow configuration of Prasad and Lord (2010). Comparison of simulation results for the rotor-splitter and stator losses determined using these procedures indicates very good agreement. Analogous to the loss scaling, a procedure based on the fan speed similarity parameter is developed to determine the windmill rotational speed and is also found to be in good agreement with engine data. Thus, despite their simplicity, the methods developed here possess sufficient fidelity to be employed in design prediction models for aircraft propulsion systems.

Aerodynamic Similarity Principles and Scaling Laws for Windmilling Fans

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Dilip Prasad
Keyword(s):  
Rotational Speed ◽  
Pressure Loss ◽  
Scaling Laws ◽  
Dynamic Pressure ◽  
Stagnation Pressure ◽  
Design Parameters ◽  
Similarity Parameter ◽  
Wide Range ◽  
Simulation Results ◽  
Good Agreement

Windmilling requirements for aircraft engines often define propulsion and airframe design parameters. The present study is focused on two key quantities of interest during windmill operation: fan rotational speed and stage losses. A model for the rotor exit flow is developed that serves to bring out a similarity parameter for the fan rotational speed. Furthermore, the model shows that the spanwise flow profiles are independent of the throughflow, being determined solely by the configuration geometry. Interrogation of previous numerical simulations verifies the self-similar nature of the flow. The analysis also demonstrates that the vane inlet dynamic pressure is the appropriate scale for the stagnation pressure loss across the rotor and splitter. Examination of the simulation results for the stator reveals that the flow blockage resulting from the severely negative incidence that occurs at windmill remains constant across a wide range of mass flow rates. For a given throughflow rate, the velocity scale is then shown to be that associated with the unblocked vane exit area, leading naturally to the definition of a dynamic pressure scale for the stator stagnation pressure loss. The proposed scaling procedures for the component losses are applied to the flow configuration of Prasad and Lord (2010). Comparison of simulation results for the rotor-splitter and stator losses determined using these procedures indicates very good agreement. Analogous to the loss scaling, a procedure based on the fan speed similarity parameter is developed to determine the windmill rotational speed and is also found to be in good agreement with engine data. Thus, despite their simplicity, the methods developed here possess sufficient fidelity to be employed in design prediction models for aircraft propulsion systems.

On the Experimental Dynamic Force Performance of a Squeeze Film Damper Supplied Through a Check Valve and Sealed With O-Rings

2021 ◽  
Author(s):  
Luis San Andrés ◽  
Bryan Rodríguez
Keyword(s):  
Dynamic Pressure ◽  
Excitation Frequency ◽  
Check Valve ◽  
Forced Response ◽  
Single Frequency ◽  
Squeeze Film ◽  
Dynamic Force ◽  
Viscous Damping ◽  
Test Rig ◽  
Force Coefficients

Abstract In rotor-bearing systems, squeeze film dampers (SFDs) assist to reduce vibration amplitudes while traversing a critical speed and also offer a means to suppress rotor instabilities. Along with an elastic support element, SFDs are effective means to isolate a rotor from its casing. O-rings (ORs), piston rings (PRs) and side plates as end seals reduce leakage and air ingestion while amplifying the viscous damping in configurations with limited physical space. ORs also add a centering stiffness and damping to a SFD. The paper presents experiments to quantify the dynamic forced response of an O-rings sealed ends SFD (OR-SFD) lubricated with ISO VG2 oil supplied at a low pressure (0.7 bar(g)). The damper is 127 mm in diameter (D), short in axial length L = 0.2D, and the film clearance c = 0.279 mm. The lubricant flows into the film land through a mechanical check valve and exits through a single port. Upstream of the check valve, a large plenum filled with oil serves to attenuate dynamic pressure disturbances. Multiple sets of single-frequency dynamic loads, 10 Hz to 120 Hz, produce circular centered orbits with amplitudes r = 0.1c, 0.15c and 0.2c. The experimental results identify the test rig structure, ORs and SFD force coefficients; namely stiffness (K), mass (M) and viscous damping (C). The ORs coefficients are frequency independent and show a sizeable direct stiffness, KOR ∼ 50% of the test rig structure stiffness, along with a quadrature stiffness, K0∼0.26 KOR, demonstrative of material damping. The lubricated system damping coefficient equals CL = (CSFD + COR); the ORs contributing 10% to the total. The experimental SFD damping and inertia coefficients are large in physical magnitude; CSFD slightly grows with orbit size whereas MSFD is relatively constant. The added mass (MSFD) is approximately four-fold the bearing cartridge mass; hence, the test rig natural frequency drops by ∼50% once lubricated. A computational physics model predicts force coefficients that are just 10% lower than those estimated from experiments. The amplitude of measured dynamic pressures upstream of the plenum increases with excitation frequency. Unsuspectedly, during dynamic load operation, the check valve did allow for lubricant backflow into the plenum. Post-tests verification demonstrates that, under static pressure conditions, the check valve does work since it allows fluid flow in just one direction.

Optimization of pipeline system with multi-hoop supports for avoiding vibration, based on particle swarm algorithm

2020 ◽  
pp. 095440622094711 ◽  
Author(s):  
Xudong Liu ◽  
Wei Sun ◽  
Ye Gao ◽  
Hui Ma
Keyword(s):  
Excitation Frequency ◽  
Particle Swarm ◽  
Element Model ◽  
Optimization Method ◽  
Operational Reliability ◽  
Particle Swarm Algorithm ◽  
Pipeline System ◽  
Pipe System ◽  
Swarm Algorithm ◽  
Single Pipe

In the dynamics design of aero-engine pipeline systems, it is necessary to avoid the excitation frequency of the engine (mainly including the rotational frequencies of high pressure and low pressure rotor systems) to improve the operational reliability of the pipeline system. In this study, a single-pipe system with multi-hoop supports was chosen as the research object, and a method based on the particle swarm algorithm was developed to optimize the layout of the hoops for effectively avoiding vibration of the pipeline system. A finite element model (FEM) of the pipeline system was created and the group of spring elements with non-uniform distribution of stiffness values was used to simulate the hoop support for improving the analysis accuracy of the model in the modeling process. Taking the hoop position as design variable, an optimization model of the pipe hoop layout was established, which aims at avoiding one or two excitation frequencies at the same time. Furthermore, the calculation procedure of optimizing pipe hoop layout using the particle swarm algorithm was given. Finally, a case study was carried out, the rationality of the created FEM was validated by experiments, and the optimal layout of hoops was obtained using the proposed optimization method.

Analysis of Piezoelectric Power Harvesting with Composite Energy Converter in Thermal Environments

2010 ◽  
Vol 139-141 ◽  
pp. 2340-2345
Author(s):  
Sheng Wen ◽  
Tie Min Zhang ◽  
Xiu Li Yang
Keyword(s):  
Excitation Frequency ◽  
Electrical Energy ◽  
Induced Voltage ◽  
Energy Converter ◽  
Power Harvesting ◽  
Thermal Environments ◽  
Piezoelectric Energy ◽  
Different Diameters ◽  
Composite Energy ◽  
Good Agreement

A composite piezoelectric energy converter intended for Micro-electromechanical Systems (MEMS) from background vibrations is presented. The converter is composed of a piezoelectric circular plate bonded to a brass substrate with different diameters. The vibration of the structure is analyzed based on the thermal-piezoelectric-elastic theory and Kirchhoff’s assumption. The vibration solutions and the relation between the vibration and output charge are obtained. The effects of geometric characteristics and environment temperatures on the electrical energy generation are numerically discussed. The numerical results show that the vibration-induced voltage is proportional to the excitation frequency and the thickness of the device, but is inversely proportional to the temperature of the environment. The experimental data show good agreement with the energy conversion analytical model.

Pipeline Vibration Analysis and Control for the First Booster of Ethylene

2013 ◽  
Vol 313-314 ◽  
pp. 777-784 ◽  
Author(s):  
Wei Yi Zhang ◽  
Yong Ming An ◽  
Shu Feng Wang ◽  
Hang Wu ◽  
Jun Yong Lei
Keyword(s):  
Frequency Response ◽  
Natural Frequency ◽  
Pressure Pulsation ◽  
Exhaust Valve ◽  
Pipeline System ◽  
Exhaust Pipe ◽  
Pulsation Frequency ◽  
Suction Pipe ◽  
The Law ◽  
Pipeline Vibration

For existing local severe vibration problems on the pipeline system of conveying ethylene booster in ethylene cracking system of a petrochemical company, the detailed analysis by CAESARII was carried out to its pipeline system natural frequency and vibration modal; The flow of ethylene gas within the booster pipeline from the suction pipe to exhaust pipe inside including the buffer tank was analyzed using fluid analysis software--FLUENT, the pressure field and velocity field of the flow was obtained. According to the law of the suction and exhaust valve open-closed mouth, dynamic boundary conditions was set on the suction valve and exhaust valve. The ethylene flow non-steady-state analysis calculations was carried out within the pipeline from the suction tube inlet to suction valve and from the exhaust valve to the exhaust tube outlet , the law of the pressure pulsation frequency response was obtained on the suction pipe inlet and the exhaust pipe outlet. The results show that ethylene gas pipeline pressure pulsation frequency response was basically equal to the frequency of the suction and exhaust valve open-closed mouth; The actual pipe vibration modals of the pipeline system on the scene and the pipeline vibration modals a few corresponding to the natural frequencies of the pipeline system close to the pulsation frequency in flow pressure are very similar, indicating that the vibration of the pipeline system is due to the pressure pulse frequency of the ethylene gas internal pipeline close to the natural frequency of the local pipeline, caused due to local resonance. Changing the form of hangers in vibration system can change the natural frequency of pipeline to avoid resonance. Tube fluid dynamic pressure caused by the stress of the pipeline is limited and will not cause damage to the tube material. Mass flow rate does not match with the tube diameter will cause too large flow velocity, the inertia force caused by the larger on the suction valve and exhaust valve before and after, resulting in the forced vibration of the compressor body.

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