Research on the influence of different heating zone lengths on pressure waves and a newly designed method of pressure wave mitigation in railway tunnels

2022 ◽  
Vol 122 ◽  
pp. 104379
Author(s):  
Junyan Wang ◽  
Tiantian Wang ◽  
Mingzhi Yang ◽  
Bosen Qian ◽  
Lei Zhang ◽  
...  
Keyword(s):  
Pressure Wave ◽  
Pressure Waves ◽  
Heating Zone

Transient Analysis on Helium Coolant Tube Break Accident of Dual-Functional Lithium Lead Test Blanket Module

2016 ◽  
Author(s):  
Qian Sun ◽  
Tianji Peng ◽  
Zhiwei Zhou ◽  
Zhibin Chen ◽  
Jieqiong Jiang
Keyword(s):  
Pressure Wave ◽  
Transient Analysis ◽  
Structural Integrity ◽  
Maximum Pressure ◽  
Pressure Waves ◽  
Operating Pressure ◽  
Pressure Shock ◽  
Dual Functional ◽  
Short Time ◽  
Helium Coolant

Dual-functional Lithium Lead Test Blanket Module (DFLL-TBM) was proposed by China for testing in the International Thermonuclear Experimental Reactor (ITER).When an in-TBM helium coolant tube breaks, high pressure helium will discharge into the Pb-Li breeding zones. The pressure shock in the TBM will threaten the structural integrity and safety of ITER. Simulation and analysis on helium coolant tube break accident of DFLL-TBM was performed, and two cases with different break sizes were considered. Computational results indicate that intense pressure waves spread quickly from the break to the surrounding structures and the variation of pressure in the TBM breeding box is drastic especially when the pressure wave propagation encounters large resistance such as at the bending corner of the flow channel, the inlet and outlet of Pb-Li, etc. The maximum pressure in the TBM breeding box which is even higher than the operating pressure of helium also occurs in these zones. Although the pressure shock lasts for a very short time, its effect on the structural integrity of DFLL-TBM needs to be paid attention to.

Cinematographic Analysis of Counter Jet Formation in a Single Cavitation Bubble Collapse Flow

2011 ◽  
Vol 27 (2) ◽  
pp. 253-266 ◽  
Author(s):  
S.-H. Yang ◽  
S.-Y. Jaw ◽  
K.-C. Yeh
Keyword(s):  
Flow Field ◽  
Cavitation Bubble ◽  
Pressure Wave ◽  
Bubble Surface ◽  
Bubble Collapse ◽  
Solid Boundary ◽  
Liquid Jet ◽  
Pressure Waves ◽  
Field Variation ◽  
Critical Position

ABSTRACTThis study utilized a U-shape platform device to generate a single cavitation bubble for the detail analysis of the flow field characteristics and the cause of the counter jet during the process of bubble collapse induced by pressure wave. A series of bubble collapse flows induced by pressure waves of different strengths are investigated by positioning the cavitation bubble at different stand-off distances to the solid boundary. It is found that the Kelvin-Helmholtz vortices are formed when the liquid jet induced by the pressure wave penetrates the bubble surface. If the bubble center to the solid boundary is within one to three times the bubble's radius, a stagnation ring will form on the boundary when impacted by the penetrated jet. The liquid inside the stagnation ring is squeezed toward the center of the ring to form a counter jet after the bubble collapses. At the critical position, where the bubble center from the solid boundary is about three times the bubble's radius, the bubble collapse flows will vary. Depending on the strengths of the pressure waves applied, either just the Kelvin-Helmholtz vortices form around the penetrated jet or the penetrated jet impacts the boundary directly to generate the stagnation ring and the counter jet flow. This phenomenon used the particle image velocimetry method can be clearly revealed the flow field variation of the counter jet. If the bubble surface is in contact with the solid boundary, the liquid jet can only splash radially without producing the stagnation ring and the counter jet. The complex phenomenon of cavitation bubble collapse flows are clearly manifested in this study.

Numerical Method for Studying Bearing Gap Pressure Wave Development and Subsequent Performance Mapping of Externally Pressurized Gas Journal Bearings

2019 ◽  
Author(s):  
Tom M. Lawrence ◽  
Marvin D. Kemple
Keyword(s):  
Numerical Method ◽  
Cross Section ◽  
Mass Flow ◽  
Pressure Wave ◽  
Design Space ◽  
Numerical Study ◽  
Pressure Waves ◽  
Wide Range ◽  
Wave Development ◽  
Static Instability

Abstract In previous work, numerical methods were developed to determine the pressure waves (pressure distribution) in the bearing gap of round externally pressurized gas bearings (EPB’s) that were pressurized through porous liners (PL bearings) or through liners with rows of feedholes (FH bearings). When integrated and differentiated these pressure portraits yield the net hydrodynamic force (FH) between the shaft and the bushing and the mass flow rates through the bearing gap. These results successfully replicated force-deflection curves and mass flow rate data for experimentally tested prototype FH and PL bearings over a wide range of mass flow constriction and clearances. Subsequently the numerical study was expanded to a broader design space of clearance and mass flow compensation. Also, a bearing performance mapping method of mapping the normalized bearing load over the clearance-eccentric deflection plane was developed for different levels of mass compensation. These performance maps produced a very interesting result as they indicated certain areas in the design space of FH bearings where static instability (negative stiffness) would be encountered. This static instability was not observed in the experimental data but is noted in references as known to occur in practice. Because this numerical method is based on the development of pressure wave portraits, the FH pressure wave could then be “dissected” in the areas of the onset of static instability which gave much insight as to the possible causes of static instability. This initial work, then, was perhaps the first to predict where in design space static instability would occur and yield some insight via examination of the corresponding pressure waves as to the cause. The numeric techniques developed, however are in no way limited to non-rotating bearings but are extensible to rotating bearings. The method is also easily extensible to examination of any configuration of feedholes or orifices. Nor is it limited to parallel deflections but can yield results for unbalanced loads. The method is also not limited to round bearings but can be applied to any cross-section configuration of bearing gap cross section such as a 3 lobed bearing or a slotted 3 lobed bearing. Examination of the resulting pressure wave development patterns for different scenarios can be examined to garner insight as to the causes of differing performance that can be applied to alterations towards optimization. Thus sharing in detail the developed numerical method underlying these studies seems worthwhile.

Simulation Models of the Complex Type Pressure Wave Supercharger

2016 ◽  
Vol 823 ◽  
pp. 341-346
Author(s):  
Sebastian Radu ◽  
Marius Hârceagă ◽  
Gheorghe Alexandru Radu ◽  
Cristian Leahu ◽  
Horia Abăităncei ◽  
...  
Keyword(s):  
Pressure Wave ◽  
Rotation Speed ◽  
Three Dimensional ◽  
Simulation Models ◽  
Pressure Waves ◽  
Complex Type ◽  
One Dimensional ◽  
Fluent Software ◽  
Type Pressure ◽  
Made In

In order to efficiently supercharge Diesel engines with pressure wave superchargers it is necessary to correlate the superchargers rotation speed with certain parameters of the supercharged engine. For this purpose, to reduce the research costs and duration, simulation models can be used which help to determine the parameters which have a major impact on the supercharger's rotational speed and efficiency. In this paper there are presented two simulation models: a one-dimensional (made in AMESim software) and a three dimensional (made in Fluent Software). This simulation models offer the possibility to visualize some dynamic phenomenon within the supercharger, like the evolution of the pressure waves or the turbulent flow inside the rotor channels. These phenomena are difficult and expensive to study with conventional methods.

Expanding of Fire-Ball and Subsequent Shock Wave Propagation by Explosives Detonation in Underwater

2011 ◽  
Author(s):  
Ho-Young Kwak ◽  
Ki-Moon Kang ◽  
Ilgon Ko
Keyword(s):  
Shock Wave ◽  
Pressure Wave ◽  
Similarity Solutions ◽  
Time Dependent ◽  
Uniform Density ◽  
Pressure Waves ◽  
Shock Wave Generation ◽  
Sudden Release ◽  
Energy Equations ◽  
Spherical Shock

A well known problem in hydrodynamics involves the sudden release of explosion energy, concentrated in a finite volume, to surroundings with uniform density. However, only similarity solutions which have no detailed information on the behavior of the fire-ball are available on this problem. In this study, we obtain a set of analytical solutions for the time dependent radius of expanding fire-ball after explosives detonation by solving continuity, Euler and energy equations with a “polytope” assumption for the fire-ball center. Subsequent spherical shock waves developed from the fire-ball in underwater are obtained by Kirkwood-Bethe hypothesis with Tait’s equation of state for water. The pressure waves emanating from the oscillating bubble in underwater, which has a notably different time scale from the shock wave generation, are obtained using the Rayleigh equation. The calculated results of period and the maximum radius of bubble developed from the fire-ball and the pressure wave from the oscillating bubble are similar to those observed.

Growth of Flame Front Turbulence

1986 ◽  
Vol 108 (4) ◽  
pp. 877-881 ◽  
Author(s):  
T. Tsuruda ◽  
M. Harayama ◽  
T. Hirano
Keyword(s):  
Experimental Study ◽  
Combustion Chamber ◽  
Flame Front ◽  
Pressure Wave ◽  
High Speed ◽  
Wall Turbulence ◽  
Pressure Waves ◽  
Fuel Type ◽  
Fuel Concentration ◽  
Schlieren Photography

An experimental study was performed on the growth of flame front turbulence by stimulating a laminar propagating flame with weak pressure waves, which were generated by sudden breaking of the membrane separating a small chamber from the combustion chamber. The flame front behavior was explored by using high-speed schlieren photography. About one millisecond after the first weak pressure wave passed the flame front, a very fine disturbance appeared at the central part of the flame front, where no effect of the wall turbulence could appear. Then, the area and strength of the disturbance were observed to increase rapidly. The effects of the pressure wave intensity, fuel concentration, and fuel type on the growth of this type of flame front turbulence were examined in detail.

An Investigation Into Quantifying Pressure Wave Oscillation in the Lung

2010 ◽  
Author(s):  
J. Mussa ◽  
A. M. Al-Jumaily ◽  
G. Ijpma
Keyword(s):  
Wave Propagation ◽  
Medical Devices ◽  
Pressure Wave ◽  
Pressure Oscillation ◽  
Variable Pressure ◽  
Pressure Waves ◽  
Pressure Oscillations ◽  
Wave Oscillation ◽  
Airway Tree

Understanding pressure wave propagation in the lung is of importance for a number of medical devices including those for diagnostics and treatments. The main objective of this research is to quantify the transmitability of the airway tree with respect to pressure oscillations. Ovine lungs are casted to produce a hollow airway tree. Variable pressure oscillations and airflow are supplied at the trachea of the casted model and pressure oscillations are measured at the bronchioles. The study indicates that pressure waves with different frequencies can be delivered to different locations of the lung by controlling the pressure oscillation source to the lung.

scholarly journals Engine Manifold Wave Action under Variable Stroke Length

2017 ◽  
Vol 11 (8) ◽  
pp. 79
Author(s):  
Jehad Ahmad Yamin
Keyword(s):  
Diesel Engine ◽  
Pressure Wave ◽  
Direct Injection ◽  
Engine Performance ◽  
Wave Action ◽  
Pressure Waves ◽  
Valve Timing ◽  
Stroke Length ◽  
Piston Bowl ◽  
Wide Range

A theoretical investigation on the pressure wave action of the manifolds of a four-stroke, direct injection (hereinafter referred to as DI), water-cooled, 4-stroke, diesel engine with variable stroke length was carried out.  The study was conducted over wide range of speeds (1000 - 3000 RPM at an increment of 500 RPM) and stroke lengths (130 mm to 210 mm at an increment of 20mm). The compression ratio was kept constant by adjusting the piston bowl volume. The study showed that shorter stroke lengths created favorable pressure waves in both inlet and exhaust manifolds at lower speeds, which resulted in improved engine volumetric and thermal efficiencies. At higher speeds, the larger strokes were favorable, however, due to less time available for the suction and exhaust strokes to be executed, the efficiencies were low. Advancing valve timing was one factor that improved the engine performance with larger stroke lengths.

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