Research on the gas-leakage rate of unsteady ventilated supercavity

Abstract The liquefied gas has been widely used in modern chemical, energy and environment protection industries. To support the integrity management and risk assessment of liquefied gas storage tanks, it is necessary to study the leakage process of liquefied gas with limited holes. There are few researches about the liquefied gas leakage rate from the crack. At present, most measurement methods used to measure leakage rate are flow meter or weighing before and after discharge, which are not suitable for liquefied gas discharge. The discharge of liquefied gas can easily form a two-phase flow in the crack and cannot be measured by the flow meter. However, the method of weighing before and after discharge cannot measure the leakage rate in real time. To realize the leakage rate real-time, online measurement, the new liquefied gas leakage rate measurement device was set up in this study. And the detachable crack leakage modules with different diameters were designed and manufactured. Using R134a refrigerant as leakage experiment medium, the relationship between crack morphology, size, pressure and leakage rate of liquefied gas was studied on the liquefied gas leakage measurement device. The new device can be used as an experimental test platform for evaluating the consequences of different liquefied gas discharge accidents or optimizing the leakage flow coefficient of the specific leakage situation, so as to better simulate the liquefied gas discharge accidents.

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Optimization of Labyrinth Seal for Screw Compressor

ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference, Volume 1 ◽

10.1115/ht2007-32275 ◽

2007 ◽

Cited By ~ 1

Author(s):

M. Selvaraji ◽

Sam P. Joseph ◽

N. Nirmal

Keyword(s):

Heat Transfer ◽

Pressure Ratio ◽

Labyrinth Seal ◽

Leakage Rate ◽

Heat Transfer Analysis ◽

Lubricating Oil ◽

Screw Compressor ◽

Labyrinth Seals ◽

Gas Leakage ◽

Working Medium

There is a growing demand for compressed air in the industry for various applications. Majority of industrial requirements is in line with screw compressor operating range. Design and construction of screw compressors are demanding tasks that require advanced calculations and theoretical knowledge. Clearances play a major role in the performance and reliability aspects of a screw compressor. Seals are provided in compressors to fit around rotor shafts in order to prevent the leakage of lubricating oil and working medium. However there is a small clearance between the seal and rotor shaft, which can cause potential leakage of the working medium. The performance of the compressor is directly related to the leakage rate through the seals. The labyrinth seal is a special type of seal, used in screw compressors and turbo-machinery for sealing purpose. Labyrinth seal is a non-contacting type seal that uses a tortuous path to minimize the gas leakage. The pressure drop occurs at each labyrinth tooth as the medium is squeezed between the labyrinth tooth and the rotor. The leakage through the seal is directly related to the labyrinth profile and also the clearance between the rotor and the labyrinth tooth. The present work is carried out to reduce the leakage through the labyrinth seal by optimising the tooth profile and operating clearances. Heat transfer analysis is carried out on the housing of the labyrinth seal to find out the boundary temperature of the seal. Also the heat transfer analysis on the labyrinth seal followed by Thermo-structural analysis is carried out to find out the accurate operating clearance of the seal. By using CFD as a tool, the optimisation is carried out on different design configurations of labyrinth seal by comparing the deviation in leakage rates. Effect of rotor speed, width of seal and pressure ratio on air leakage rate is also investigated. A set of labyrinth seals has been designed based on the above optimisation and tested in the compressor. The results have been compared with the CFD prediction.

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Probing into gas leakage characteristics of ventilated supercavity through bubbly wake measurement

Ocean Engineering ◽

10.1016/j.oceaneng.2021.110457 ◽

2022 ◽

Vol 245 ◽

pp. 110457

Author(s):

Siyao Shao ◽

Jiaqi Li ◽

Kyungduck Yoon ◽

Jiarong Hong

Keyword(s):

Gas Leakage ◽

Bubbly Wake ◽

Leakage Characteristics ◽

Ventilated Supercavity

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On GCLs' Gas Permeability for Modelling of Gas Leakage Rate through GM/GCL Composite Liner Due to a Defect in the Geomembrane

Geo-Frontiers 2011 ◽

10.1061/41165(397)207 ◽

2011 ◽

Author(s):

H. M. Abuel-Naga ◽

A. Bouazza

Keyword(s):

Gas Permeability ◽

Leakage Rate ◽

Composite Liner ◽

Gas Leakage

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Numerical Simulation of Stress-Relief Effects of Protective Layer Extraction / Symulacja numeryczna skutków odprężenia warstwy zabezpieczającej w trakcie jej wybierania

Archives of Mining Sciences ◽

10.2478/amsc-2013-0035 ◽

2013 ◽

Vol 58 (2) ◽

pp. 521-540

Author(s):

Jia Tian-Rang ◽

Zhang Zi-Min ◽

Tang Chun-An ◽

Zhang Yong-Jun

Keyword(s):

Gas Permeability ◽

Vertical Direction ◽

Protective Layer ◽

Stress Relief ◽

Leakage Rate ◽

Gas Leakage ◽

Fracture Evolution ◽

Simulation Results ◽

Layer Extraction ◽

Rock Strata

Field test and laboratory analog model test on the stress-relief effects of protective layer extraction are time-consuming and laborious. In this paper, on the basis of full consideration of rock heterogeinity and in combination with gas geology at Pingdingshan Mine 5, a numerical model was estalished with the gas-solid coupling rock failure process analysis system RFPA-Gas to simulate the stress variation law, roof and floor deformation, fracture evolution law, displacement in the protected seam, change in gas permeability and gas migration law during protective layer extraction. The simulation results repoduced stress variations in coal and rock strata, roof and floor deformation and fracture evolution process during protective layer extraction. The movement of rock strata were characterized by upper three zones and lower two zones: caving zone, fracture zone and bending subsidence zone in the vertical direction in the overlying strata; floor deformation and failure zone and elasto-plastic deformation zone in the vertical direction in the underlying strata. It showed that stress relief occurred in the protected seam, which led to vertical and horizontal displacements, significant increase in gas permeability, gas desorption and migration. Hence, the outburst threat in the protected seam was eliminated. Meanwhile, with comprehensive analysis of variaition of stress state, deformation characteristics and fracture distribution in coal seam and with consideration of changes in gas leakage rate, gas pressure and permeability, according to gas leakage rate, the floor strata of the protecive layer were divided into four leakage zones. They corresponded to four zones with different stress states and fracture development: original leakage zone - slow reducing leakage zone - dramatic increasing leakage zone- steady increasing leakage zone. This classification provides a clear direction for gas control in the protective layer. The simulation results are in good agreement with the stress-relief effects in field.

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Modeling of methane migration from gas wellbores into shallow groundwater at basin scale

Environmental Earth Sciences ◽

10.1007/s12665-020-09170-5 ◽

2020 ◽

Vol 79 (18) ◽

Author(s):

Reza Taherdangkoo ◽

Alexandru Tatomir ◽

Martin Sauter

Keyword(s):

Water Saturation ◽

Shallow Groundwater ◽

Field Studies ◽

Lateral Spreading ◽

Leakage Rate ◽

Residual Water ◽

Two Phase ◽

Upward Migration ◽

Gas Leakage ◽

Basin Scale

Abstract Methane contamination of drinking water resources is one of the major concerns associated with unconventional gas development. This study assesses the potential contamination of shallow groundwater via methane migration from a leaky natural gas well through overburden rocks, following hydraulic fracturing. A two-dimensional, two-phase, two-component numerical model is employed to simulate methane and brine upward migration toward shallow groundwater in a generic sedimentary basin. A sensitivity analysis is conducted to examine the influence of methane solubility, capillary pressure–saturation relationship parameters and residual water saturation of overburden rocks, gas leakage rate from the well, tilted formations, and low-permeability sediments (i.e., claystones) on the transport of fluids. Results show that the presence of lithological barriers is the most important factor controlling the temporal–spatial distribution of methane in the subsurface and the arrival time to shallow groundwater. A pulse of high leakage rate is required for early manifestation of methane in groundwater wells. Simulations reveal that the presence of tilted features could further explain fast-growing methane contamination and extensive lateral spreading reported in field studies.

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