Papers by Keyword: Leakage

Abstract: Oil spill at sea by pipeline cracks can cause environmental damage. Knowledge of interfacial phenomena of immiscible liquids helps to study the dispersion of pollutants in oceans, favoring thus flow behavior of the forecast in the vicinity of the leak in submerged pipelines. This study aims to numerically study the leakage of behavior in a submerged pipeline carrying oil. It adopted a two-dimensional model based on mass conservation equations, linear momentum and the model k-ε standard turbulence. We used the Ansys CFX for meshing with 40,510 hexahedral elements. The results of pressure fields and volumetric fraction of oil are analyzed and discussed.

Abstract: We studied the effect of annealing and Co ion doping on the structure, leakage current, ferroelectric polarization and magnetism of BiFeO₃ samples. X-ray diffraction patterns demonstrate that an appropriate Co doping concentration is favor of suppressing the secondary phase but annealing treatment is apt to the growth of both the main and the secondary phases. The current density as a function of an electric field indicates that Co doping increases the leakage current density as samples before annealing but suppresses it after annealing. Annealing treatment improves the leakage for Co-doped sample and reduces it for the undoped sample. Ferroelectric hysteresis loops reflect that Co ions doping is liable to increase the ferroelectric polarization, while the sample is annealed it will do opposite effect. However the annealing treatment do improve the ferroelectricity for pure BiFeO₃ sample. The magnetic hysteresis at room temperature shows the obvious enhancement of ferromagnetic properties with the sample after annealing.

Abstract: Established two-dimensional axisymmetric staggered tooth shape labyrinth seal grid model by GAMBIT software, simulated oil-air two-phase mixture flow field within labyrinth seal by fluent software, confirmed the best grid size of numerical calculation, studied the seal mechanism and influence of gap width variation on the leakage. The results show that when fluid flows through the narrow clearance, its velocity increases and pressure decreases. The optimized clearance width within 0.5mm to 1.0mm is preferable.

Abstract: The objective of this paper is to study the different acoustic emission (AE) activities from material integrity and leakage which were obtained from CNG steel cylinder during pressurization. CNG type I cylinders were employed to test by hydrostatic stressing. The pressure was continuously increased to over 1.1 time of operating pressure or leakage occurrences. AE sensors, resonance frequency of 150 kHz, were mounted on the outside cylinder wall to detect the AE activities throughout the testing. AE activities were compared between AE of material expansion and leakage by amount of AE signals detected then analyzed by AE parameters. AE parameters including Amplitude, Count, Energy (MARSE), Duration and Rise time were analyzed to distinguish the AE data. The AE wave form in time and frequency domain were also considered in analysis process. The location of AE sources were located by the calculation the arriving differenced time of 2 or more sensors to indicate the position of cylinder faults. The results showed the AE signals of material expansion were randomly detected throughout the pressurization until the Enegy and Amplitude of detected signals were increased by high incresing rate where was leakage occurrences. AE parameters of Amplitude and Energy can be significantly represented the difference between material expansion and leakage. Addition, the Hit rate monitoring cloud be a notice activity before cylinder leaks. The benefits of this work are the AE characterization of the material expansion, leakage and noise for improvement of Type-1 CNG cylinder tests.

Abstract: Since external loads affect the sealing performance of bolted flanged joints, this paper calculated external loads of bolted flanged joints by using CAESAR II software and evaluated the effects of external loads on the sealing performance from the viewpoint of changes in contact gasket stress and flange rotation by using ANSYS software. The FE results showed that the contact gasket stress decreases a lot at the tension side and increases a little at the compression side. The paper also evaluated the stress distribution in bolted flanged joints subjected to external loads. The results suggested that the flange rotation and the overall stress increased compared with that of flange without external loads. External loads can induce unexpected leakage and strength failure of the bolted flanged joints during operation.

Abstract: In order to study the working features of automotive air conditioning scroll compressor, this paper uses mathematical model of working process to analyze it. After studying working process, a equation of suction volume is given. The thermodynamic model of compression chamber and back pressure chamber includes mass conservation and energy conservation. Based on Hydromechanics, leakage models of radial leakage and tangential leakage are discussed. The model lays a foundation of automotive air conditioning scroll compressor performance simulation.

Abstract: Built-in VOF model and k-ε turbulence model in Fluent were used to simulate the evaporation and diffusion of the pool formed by leaked UDMH on a cliff. Different situations in three wind speeds were calculated, and the diffusion mode and concentration distribution law were analyzed. The results show that there is a large poisoned area formed on the cliff, and people under the cliff should escape to upwind immediately and the emergency personnel should access the accident spot along the back of the cliff.

Abstract: In hot rolling mills the plastic deformation of the strip is realized at high force and plastic strain speed controlled by electro-hydraulic servo actuators. These hydraulic servo actuators - hydraulic capsules – are capable to adjust the rolling gap at great rolling force dynamically. The dynamic behaviour of the rolling mill’s AGC (automatic gap adjustment) system mainly depends on the correct operation of hydraulic actuators and servo valves. These equipments are great value, planned maintenance is essential for reliable correct operation. The maintenance includes the refurbish of damaged, worn surfaces inside the cylinder and replacement of worn out seals. In the study a laboratory hydraulic positioning system was used to examine the effect of hydraulic actuator internal leakage to dynamic behaviors of the positioning system. Because the laboratory test system is similar to the hydraulic gap adjustment system therefore the laboratory test results can be extended to the rolling mill’s Hydraulic Gap Control system.

Abstract: Lip seal, widely used in industries, is usually applied to seal pressure chamber. Leakage of lip seal has always been a primary problem. In the present study, hydrodynamic property of lubricating film and elastic deformation of sealing lip are analyzed numerically by coupling Reynolds equation and elastic deformation equation. A numerical model for calculating leakage is proposed, results of the analysis will be of help to interference design and structure optimization for auto water pump bearing’s seal.

Abstract: In order to decrease leakage faults and improve efficiency of fault detection for pipe network in hot-water district heating, this study proposed a model for hydraulic-condition of node leakage based on the network graph theory. This mathematical model can be utilized to simulate and predict node leakage condition through plane topology of heating network. For fixed pump head of the simulated sample network, some aspects of hydraulic-condition are discussed, including various leakage nodes and flow rate at supply and return run-out. Simulation results denote that both users’ pressure and flow decrease for the supply run-out leak while results are opposite if return run-out leaks. For users located before leakage node, the nearer to the leakage node, the greater they are influenced. However, users behind the leakage node change in the same way and more than the former.