scholarly journals Heat-Induced, Pressure-Induced and Centrifugal-Force-Induced Exact Axisymmetric Thermo-Mechanical Analyses in a Thick-Walled Spherical Vessel, an Infinite Cylindrical Vessel, and a Uniform Disk Made of an Isotropic and Homogeneous Material

2017 ◽  
Vol 9 (2) ◽  
pp. 66-66 ◽  
Author(s):  
Vebil Yıldırım
Keyword(s):  
Centrifugal Force ◽  
Cylindrical Vessel ◽  
Homogeneous Material ◽  
Spherical Vessel ◽  
Uniform Disk

A Thermal Stress Mitigation Technique for Local Postweld Heat Treatment of Welds in Pressure Vessels

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Chunge Nie ◽  
Pingsha Dong
Keyword(s):  
Heat Treatment ◽  
Thermal Stresses ◽  
Postweld Heat Treatment ◽  
Pressure Vessels ◽  
Cylindrical Vessel ◽  
Spherical Vessel ◽  
Novel Method ◽  
Bull's Eye ◽  
Recommended Guidelines ◽  
Postweld Heat

This paper introduces a novel method for effectively mitigating high thermal stresses caused during local postweld heat treatment (PWHT) of welds in pressure vessels on which traditional heating method such as bull's eye heating arrangement has been proven difficult in meeting Code requirements for avoiding “harmful” temperature gradients. The method involves the use of a secondary heat band (SHB) that strategically positioned at some distance away from primary PWHT heat band (HB) in terms of vessel characteristic length parameter Rt, where R is vessel radius and t wall thickness. The basic principles associated with the SHB based technique are first demonstrated on a simple straight pipe girth weld configuration. Then, applications for treating nozzle welds in more complex spherical vessel, cylindrical vessel, and at end of cylindrical vessel are presented. Finally, a set of recommended guidelines are provided for defining both the SHB size and location for performing local PWHT on welds in three major nozzle/vessel weld configurations.

Thermal effects accompanying spontaneous ignition in gases. IV. The decomposition of diethyl peroxide in a cylindrical vessel and the effect of diluents on self-heating

1971 ◽  
Vol 325 (1561) ◽  
pp. 175-196 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Critical Temperature ◽  
Stationary State ◽  
Temperature Rise ◽  
Cylindrical Vessel ◽  
Spontaneous Ignition ◽  
Spherical Vessel ◽  
Average Value ◽  
Self Heating ◽  
Rate Of Dissipation

The investigation (see parts I to III) of the spontaneous ignition of gaseous diethyl peroxide as a thermal explosion is concluded by a series of experiments mainly in a cylindrical vessel, and including diluted mixtures. A very fine thermocouple (25 µ m diameter) has been used to probe the temperature distributions between the axis and the wall both in systems reacting subcritically and in systems on the verge of ignition. A multijunction thermocouple has also been employed to obtain instantaneous readings of distributed temperature in a spherical vessel. It is found that self heating is always present. In accordance with a conductive theory of heat losses, temperatures are not uniform throughout the reactant, but depend on the fractional distance ( z = r / r 0 ) from the vessel axis, being greatest at the axis and least at the walls. For the cylinder, the form of the profiles expected in a stationary state is ( T - T a )/( RT a 2 / E ) = 2 ln (1 + G )/(1 + Gz 2 ) and good agreement is found between theory and experiment. (The significance of G is discussed in the text.) This agreement, the symmetry of the profiles, and the absence of any temperature step at the walls confirm the absence of convection at the pressures concerned. A critical centre temperature rise exists above which ignition is inevitable. The greatest value of this increment is 23.3 K ; for simple theory, the predicted value is 19 K (1.39 RT a 2 / E ). Any temperature dependence of this critical increment lies beyond the discrimination of the present apparatus. Similar agreement is found between ‘measured’ and theoretically expected values for Frank-Kamenetskii’s δ . At criticality, the measured values average 2.25 against a theoretical value (uncorrected for finite vessel size or finite reaction rate) of 2 exactly. ‘Measured’ values for δ in subcritical systems are also in satisfactory accord with expectation. Other ‘indirect’ tests of thermal theory are also satisfied. Thus the curvature of the critical pressure limit (boundary on the p — T diagram between explosive and slow reaction) exactly corresponds to the activation energy measured in isothermal decomposition. Similar temperature-position profiles are found in diluted mixtures below criticality, and although critical explosion pressures depend on the degree of dilution, the critical temperature rise for ignition does not. The average value found is 19.0 K. Nor does the critical temperature gradient at the vessel boundary vary from the value ( — 2 exactly) predicted for any dilution of vessel geometry. There are the same influences on criticality as in the spherical vessel: in accord with stationary state conductive theory, thermal conductivity is the principal factor but its influence is distorted to varying degrees, first by the occurrence of dynamic heating accompanying gas entry, secondly by the rate of dissipation of this heating, which is governed by the thermal diffusivity, and thirdly by the departures from stationary state behaviour largely governed by the specific heat of the diluent. These influences explain an otherwise erratic dependence of critical ignition pressures on thermal conductivity.

Plastic Analysis of Radial Outlets From Spherical Pressure Vessels

1964 ◽  
Vol 86 (2) ◽  
pp. 193-198 ◽  
Author(s):  
N. C. Lind
Keyword(s):  
Static Loading ◽  
Local Deformation ◽  
Pressure Vessels ◽  
Cylindrical Vessel ◽  
Plastic Behavior ◽  
Spherical Vessel ◽  
Rigid Plastic ◽  
Limit Pressure ◽  
Plastic Analysis ◽  
Spherical Pressure

A method is described whereby the limit pressure may be determined for a radial juncture of a cylindrical vessel and a spherical vessel, assuming quasi-rigid plastic behavior. The limit pressure may for mild-steel vessels be interpreted as the pressure causing extensive local deformation at the juncture under static loading conditions.

Laminar Burning Speed Measurements of Premixed JP-8, Oxygen and He Flames

2006 ◽  
Author(s):  
Farzan Parinejad ◽  
Edwin Shirk ◽  
Kian Eisazadeh Far ◽  
Hameed Metghalchi
Keyword(s):  
High Temperatures ◽  
Power Law ◽  
Flame Structure ◽  
Cylindrical Vessel ◽  
Pressure Measurements ◽  
Pressure Data ◽  
Spherical Vessel ◽  
Combustion Pressure ◽  
Made In ◽  
Laminar Burning Speed

The focus of this study is the calculation of the laminar burning speed of JP-8, oxygen, and helium mixtures at high temperatures and pressures. Two constant volume combustion vessels were used for the analysis. The spherical vessel was primarily used for the collection of pressure data from which the burning speed was calculated. A cylindrical vessel was also used in conjunction with a shadowgraph system to observe the flame structure and the onset of instability. Observations of JP-8 with both nitrogen and helium as diluents were made in the cylindrical vessel and it was seen that at a temperature of 200° C over the range of 1-8 atmospheres pressure and equivalence ratios of 0.7-1.0 with helium as the diluent, the flame was laminar throughout its combustion. Pressure measurements of JP-8 and oxygen with helium as the diluent were then made in the spherical vessel. Laminar burning speed of JP-8 with oxygen and helium has been calculated using the spherical vessel pressure data for this range of temperatures, pressures and equivalence ratios. Power law correlations for burning speeds have been developed for these results.

Burning Speed Measurement of JP-8 Air Flames

2004 ◽  
Author(s):  
Farzan Parsinejad ◽  
Christian Arcari ◽  
Edwin Shirk ◽  
Hameed Metghalchi
Keyword(s):  
High Speed ◽  
Variable Temperature ◽  
Dynamic Pressure ◽  
Flame Structure ◽  
Pressure Rise ◽  
Ccd Camera ◽  
Cylindrical Vessel ◽  
Spherical Vessel ◽  
Speed Measurement ◽  
Wide Range

Burning speed measurement and structure of JP-8 air mixtures at a wide range of temperature and pressure have been studied using two matched constant volume chambers. The experimental facilities include a spherical chamber and cylindrical vessel with glasses at the end caps to enable us visualizing flame structure. Cylindrical vessel is located in a Schlieren set up including spherical mirrors and a high speed CCD camera. Facilities also include and oven which can raise the initial temperature of the mixtures in spherical vessel to 500 K and similar heating elements that perform the same task in cylindrical chamber. A thermodynamic model has been developed to calculate burning speeds using dynamic pressure rise in the chamber. The model considers a central burned gas core of variable temperature surrounded by an unburned gas shell with uniform temperature with a thermal boundary layer at the wall. Burning speed and flame structure of different gaseous fuel-air mixtures have been investigated. Autoignition characteristics of JP-8 air mixtures have also been determined by the sudden pressure rise in spherical vessel.

scholarly journals Influence of Explosion Chamber Shape on Timing Parameters of Disperser

2021 ◽  
Vol 29 (48) ◽  
pp. 143-148
Author(s):  
Zuzana Szabová ◽  
Richard Kuracina ◽  
Miroslav Mynarz ◽  
Marián Škvarka
Keyword(s):  
Delay Time ◽  
Cylindrical Vessel ◽  
Cylindrical Shape ◽  
Explosion Chamber ◽  
Spherical Vessel ◽  
Optimal Delay ◽  
Measurement Results ◽  
Optimal Delay Time ◽  
Time Parameters

Abstract A standardized device with a volume of 1 m3 or 20 L is used to determine explosion parameters. An explosion chamber where explosion takes place is of a spherical or cylindrical shape that suits the shape of a cubic container. In the case of a cylindrical vessel, the diameter and depth of the vessel are 1: 1. In this case, it is a spherical vessel with a volume of 365 liters. Time parameters of the disperser in the spherical vessel are compared with those of a truncated spherical vessel with a volume of 291 liters. Comparison of the measurement results showed that the optimal delay time of the explosion chamber with a volume of 291 liters is 290 ms, while the delay time of the explosion chamber with a volume of 365 liters is 350 ms.

Numerical simulation on structure effects for linked cylindrical and spherical vessels

SIMULATION ◽  
2018 ◽  
Vol 94 (9) ◽  
pp. 849-858
Author(s):  
C Yan ◽  
ZR Wang ◽  
F Jiao ◽  
C Ma
Keyword(s):  
Structural Changes ◽  
Flame Temperature ◽  
Cylindrical Vessel ◽  
Gas Explosion ◽  
Spherical Vessel ◽  
Airflow Velocity ◽  
Monitoring Point ◽  
Explosion Pressure ◽  
Simulation Results ◽  
Peak Value

This paper presents a simulation study on the methane–air mixture explosions through using the eddy-dissipation concept (EDC) model in FLUENT. The aims are to investigate the structure effects of methane–air mixture explosions in a spherical vessel, cylindrical vessel and different systems of cylindrical vessels connected with pipe. Meanwhile, in order to study the characteristics of methane-air mixture explosions in the linked vessels, changes of flame temperature and airflow velocity in the linked vessels are simulated and analyzed. The results suggest that the effect of structural changes of a single vessel on the gas explosion intensity is clear, and the explosion intensity of a spherical vessel is greater than that of a cylindrical vessel. The simulation results of different structural forms of a cylindrical vessel connected with pipelines show that the time to reach the peak value of explosion pressure is the shortest in the linked vessels, and the explosion pressure rising rate is highest at the vessel’s center. For the linked vessels, after ignition, the airflow ahead of the flame propagates to the secondary vessel, and the maximum airflow velocity of every monitoring point in the linked vessels increases. The detonation occurs when the flame propagates to the secondary vessel, which leads to a severe secondary explosion in the secondary vessel. The studies can provide an important reference for the safe design of industrial vessels.

Blast Adjustment Factors for Elevated Vertical Cylindrical PVBs

2014 ◽  
Author(s):  
Jihui Geng ◽  
Quentin Baker ◽  
Kelly Thomas
Keyword(s):  
Ground Level ◽  
Pressure Vessels ◽  
Cylindrical Vessel ◽  
Chemical Processing ◽  
Prior Work ◽  
Spherical Vessel ◽  
Blast Overpressure ◽  
Blast Effect ◽  
Adjustment Factors ◽  
Spherical Pressure

Pressure vessel burst (PVB) is an explosion scenario commonly encountered at chemical processing facilities. PVBs pose both blast and fragmentation hazards. Blast prediction methods specific to PVBs were first developed in the 1970s and revised blast curves were published in 1995. The published blast curves were developed for spherical vessel bursts. However, most pressure vessels are cylindrical rather than spherical. The blast wave originating from a cylindrical PVB is not spherical (i.e., as with a spherical vessel). Rather, the blast to the sides of a cylindrical vessel is stronger than on the ends, creating non-spherical pressure contours, particularly near the vessel. The cylindrical vessel directional blast effect has recently been investigated by the authors, resulting in a correlation to account for the directional effects. However, it was assumed in the prior work that the vessel was at ground level. This paper extends the prior work to elevated PVBs. Both elevated spherical and cylindrical PVBs are examined to provide new correlations for blast overpressure and impulse for a range of vessel geometries and burst conditions.

Pressure Vessel Burst Directional Effects

2011 ◽  
Author(s):  
Jihui Geng ◽  
Quentin Baker ◽  
Kelly Thomas
Keyword(s):  
Pressure Vessel ◽  
High Explosive ◽  
Spherical Shape ◽  
Pressure Vessels ◽  
Cylindrical Vessel ◽  
Chemical Processing ◽  
Spherical Vessel ◽  
Pressure Transducers ◽  
Blast Overpressure ◽  
Blast Effects

Pressure vessel burst (PVB) is a class of explosion for which there are hazards at virtually all chemical processing facilities. PVBs present both airblast and fragmentation hazards. Blast prediction methods specific to PVBs were first developed in the 1970s and revised blast curves were published in 1995. The published blast curves were developed for spherical vessel bursts, whereas most pressure vessels in use in industry are cylindrical. Blast effects around a bursting cylindrical vessel are not uniform as with a spherical vessel. The blast to the side of a cylindrical vessel is stronger than off the ends, creating non-circular pressure contours. The directional effects diminish with distance as the expanding shock wave approaches a spherical shape. A correlation was developed in the 1970s to account for directional effects using high explosive test data, the best available resource at the time. Like all test programs, pressure transducers extended to limited distances from the explosive charge, yet the data are often extrapolated to a far greater distance. This paper presents the results of recent work on directional effects specific to bursting cylindrical pressure vessels and provides new correlations for blast overpressure and impulse for a range of vessel geometries and burst conditions. The results can be used to predict the airblast hazards from cylindrical PVBs over the range of standoff distances for which directional effects exist.

Ion thinning of integrated circuit transverse specimens for transmission electron microscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1426-1427
Author(s):  
F. Shaapur
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Integrated Circuit ◽  
Substrate Surface ◽  
Homogeneous Material ◽  
Material System ◽  
Ion Milling ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Motion Profile

Non-uniform ion-thinning of heterogenous material structures has constituted a fundamental difficulty in preparation of specimens for transmission electron microscopy (TEM). A variety of corrective procedures have been developed and reported for reducing or eliminating the effect. Some of these techniques are applicable to any non-homogeneous material system and others only to unidirectionalfy heterogeneous samples. Recently, a procedure of the latter type has been developed which is mainly based on a new motion profile for the specimen rotation during ion-milling. This motion profile consists of reversing partial revolutions (RPR) within a fixed sector which is centered around a direction perpendicular to the specimen heterogeneity axis. The ion-milling results obtained through this technique, as studied on a number of thin film cross-sectional TEM (XTEM) specimens, have proved to be superior to those produced via other procedures.XTEM specimens from integrated circuit (IC) devices essentially form a complex unidirectional nonhomogeneous structure. The presence of a variety of mostly lateral features at different levels along the substrate surface (consisting of conductors, semiconductors, and insulators) generally cause non-uniform results if ion-thinned conventionally.

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