Internal Pressure Distribution Research Articles

Analysis of Flow Field for Automotive Exhaust System Based on Computational Fluid Dynamics

In this study, a double mode muffler that can automatically adjust the exhaust resistance according to the engine speed was designed. Based on computational fluid dynamics theory, the governing equation and turbulent equations for numerical simulation of muffler were established. The pressure loss and the internal flow characteristics of the double mode muffler were analyzed by CFD software. The influence of the distance between the main and submuffler on the flow field of exhaust system was researched. In addition, the internal pressure distribution, the turbulence intensity distribution and the velocity vector diagram of the dual mode muffler were also obtained. The pressure loss of double mode muffler is mainly distributed in the area of air mutations. Main silencer plays a leading role in the entire exhaust system. Therefore, the trend of the pressure loss of the exhaust system with the change in the distance between main and auxiliary muffler was also obtained. When the distance between the main and auxiliary silencer changed from 50 mm to 300 mm, the pressure loss of exhaust system muffler first increased and then decreased, and following this, continued to increase. The results will provide a theoretical basis for designing complex exhaust system.

Analysis and Evaluation of Wind Turbine Flow Field and Noise Simulation Based on CFD Software

CFD is the abbreviation of the computational fluid dynamics, which is widely used in engineering fluid simulation. Based on two-dimensional N-S equation and k-e turbulence model, this paper uses FLUENT software, finite volume method and SIMPLEC algorithm to do numerical simulation and analysis on flow field in centrifugal fan. In order to improve the efficiency and accuracy of calculation, this paper uses AutoCAD to establish the two-dimensional model of fan, and uses the structured triangular mesh to divide grid. Encrypting the blade can improve the precision and also save the computer memory. Through the calculation we get the internal flow field velocity and pressure distribution in the wind turbine, and get the power level cloud of internal noise in fan. It provides the technical reference for the optimization design of wind turbine.

Experimental analysis of the fluid–structure interaction in finite-length straight elastic vessels

Numerous bio-mechanical flow problems are characterized by fluid–structure interaction phenomena. To analyze in detail the impact of fluid–structure interaction on the overall flow structure and the wall motion the oscillating laminar flow in an elastic vessel is experimentally investigated by time-resolved particle image velocimetry and pressure measurements. The vessel deformation amplitude is varied between 0.5% and 6% of the vessel diameter at Reynolds number and Womersley number ranges of 300≤Re≤1000 and 5≤Wo≤10. Motivated by Womersley’s fundamental results for rigid and elastic vessels it is the purpose of this study to extend the discussion to vessels of finite length undergoing high dilatation amplitudes and to provide benchmark data for numerical fluid–structure interaction methods. A detailed discussion of the results of the volume flux distribution, static pressure distribution, rate of change of the diameter, and wall-shear stress distribution is given and evidences a significant effect of vessel deformation on the distribution of the flow quantities. The inlet volume flux distribution excited by the piston pump generates an internal pressure distribution determining the vessel deformation which via the temporal derivative of the diameter change generates a delayed volume flux distribution that is superimposed onto the inlet volume flux. The comparison of the results with comparable rigid pipe flows shows variations in the velocity profile amplitude of up to 10% depending on the phase angle. The vessel elasticity leads to a wall-shear stress reduction during forward flow of up to 20%.

The Establishment of Ninety Degree Gas Elbow Pipes Internal Pressure Distribution Model

According to the principle of harmonious dimensions, the qualitative distribution model of the internal pressure on elbow pipes were determined; Through FLUENT numerical simulation, the internal pressure were given under 96 kinds of gas fluid conditions; By analyzing the variation of the internal pressure with flow and geometrical parameters, the variation of the internal pressure distribution within the elbow pipes has been studied; By means of 1stOpt nonlinear fitting package, the formula of three-dimensional internal pressure distribution was determined; Compared with the numerical results, the maximum relative error is 0.012%. The formula provides theoretical bases for strength check, the transport pipeline and wall thickness design of the high pressure, high velocity elbow.

Injector Nozzle Multiphase Flow Numerical Simulation of High Pressure Common Rail System

The changing of injector nozzle structure will influence the combustion and emission properties in diesel engine. Three-dimensional numerical simulation of multiphase flow of mini-sac nozzles of high pressure common rail were calculated by using the computational fluid dynamics ( CFD ) method in this paper. The results shown that this method can be more accurately obtained a lot of useful information on the flow field inside the nozzle in a relatively short period of time, and it is convenient for analysis and research the influence of geometry parameters on the flow characteristics inside the nozzle. The paper also studied the influence of nozzle inlet pressure, the angle between the axis of the hole and the axis of the injector and nozzle entrance radius to the flow characteristics inside the nozzle. It also studied the distribution of internal pressure, velocity of flow, gas-phase volume fraction and turbulent kinetic energy. These studies provided a favorable basis for the design and improvement of the nozzle structure and optimize combustion system matches.

Numerical Simulation of Impact Effect of Internal Gas Pressure on Chamber Housing in Low-Voltage Circuit Breaker

In this paper, the fluid-solid interaction model of the impact process of internal pressure in arc chamber on housing structure of low-voltage circuit breaker is established, including the computational fluid dynamic (CFD) module that can assess 3-D pressure distribution of internal gas flow in the arcing chamber and finite element module (FEM) to calculate the impact of high-pressure gas flow on the housing. Based on the CFD module, the internal pressure distribution under different breaking currents and venting conditions is simulated, in which the simulation results agree well with the experimental results. Then, based on the 3-D pressure distribution, through the 3-D FEM of housing impact, the dynamic stress and deformation of chamber housing are simulated and analyzed. By this method, the stress concentration region of arc chamber housing can be predicted, which can provide reference for structure optimization design of arc chamber. For the region where stress is concentrated, structural strength needs to be enhanced, which can effectively avoid rupture problems due to local excessive stress on the housing.

Comparison of Suppression Cavitations Schemes within Hydraulic Valve

Four kinds of cavitations suppression schemes on the basis of cavitations theory of control valve were designed in this paper. The fluid dynamic characteristics parameters under the above schemes was obtained by using RNG k-ε turbulence model respectively, which is composed with the velocity vector of internal fluid, pressure and cavitations distribution contours of numerical simulation. The results show that the design of straight-through porous structure has a lot of advantages compared with other structures in terms of its good fluid dynamic characteristics that fluid flow is uniformly in the valve cartridge, the loss of pressure is lower, the impaction in expansion cartridge is smaller and impact noise of it can be reduced. Therefore, the straight-through porous structure could suppress the initiation and development of the cavitations.

Analysis of Performance of Automotive Exhaust Muffler Based on ANSYS Finite Element

At present, the control of the automobile engine exhaust noise is mainly installed exhaust muffler. Muffler design and performance research mainly around the silencing performance and the influence to engine power loss. This article built the 3d modeling of automobile exhaust muffler and through simulation analysis obtained the muffler internal acoustic pressure distribution and changes of insertion loss with frequency. Predict the silencer muffler performance as well as the influence on engine power loss. Provide a reference basis for the design of the silencer and optimization. Compared to the traditional experiment method, the method in this article has the advantages of short cycle, low cost.

MULTIPLE LOADING EFFECTS ON WIND-INDUCED STATIC PERFORMANCE OF SUPER-LARGE COOLING TOWERS

Currently, four grouped 177 m super-large cooling towers, i.e. column-supported hyperboloidal shells, are to be constructed in a typical electric power plant in Southeast China. To this end, simultaneous pressure measurements on 1:200 rigid tower models are carried out in an atmospheric boundary layer (ABL) wind tunnel, aimed at accurately obtaining the external/internal cladding wind loads on these shells. The wind-induced static behavior of the cooling towers is analyzed by applying the wind loads acquired via the pressure model tests, using both linear elastic and nonlinear elastic finite element (FE) analyses. The corresponding responses (structural deformation, internal force and local buckling state) are compared with those obtained by the traditional design approach, focused on the effects of internal suction and external pressure distribution. Besides, the tower group interference effects are studied by comparing the results computed of a freestanding tower, with those of the tower groups during two different construction stages. The main findings about the loading effects on the static performance of the super-large cooling towers are helpful for improving the current Chinese Codes that govern the design of super-large cooling towers.

반도체 생산설비 루츠형 진공펌프 계통에 대한 유동-구조 연성해석

The present study conducts CFD analyses on the internal flow fields of roots type vacuum pumps of semiconductor fabrication facility, and the computed CFD results for internal pressure and temperature distributions are applied to structural analyses of the pumps. The coupled analysis results between flow and structure show that the deformation of pump structure is mainly resulted from the thermal expansion of gas in pump, and the deformed impeller and housing produce their severe contact and impact phenomena causing mechanical damage and fracture.

Part 1: Analytical modeling of symmetric multi-nose tube hydroforming

Part 1 of this series of papers presents an analytical model for a multi-nose tube hydroforming process based on a mechanistic approach. In this process, the tube is surrounded by a number of evenly distributed circular dies. The model was established based on equilibrium conditions, yielding criteria, geometrical relationships, and a volume constancy condition. The system of equations was derived and solved for various process parameters. The model validation was performed using finite element analysis and experiments. The model has the ability to predict process parameters such as stresses, strains, internal pressure, geometry variables, and thinning rate distribution. The model could be applied to regular planar tube hydroforming of polygonal shapes such as square, pentagon, or octagon. Details for establishing governing relationships for polygonal shape hydroforming from the multi-nose analytical model are given in Part 2 of this series of papers.

Centrifugal Compressor Spiral Dry Gas Seal Simulation Working at Reverse Rotation

Unidirectional dry gas seal may experiences reverse rotation when equipped in a centrifugal compressor. This paper describes how the reverse rotation effects on the spiral unidirectional dry gas seal performance and pressure distribution inside the gas film, also an investigation of using a different herringbone shape grooves configurations has been done using ANSYS FLUENT 14.5 CFD simulation. The influence of decreasing rotational speed to the static condition and rotate in the reverse direction on internal flow and gas seal performance is examined from 10800 to -10380rpm. The results indicate that the internal pressure distribution inside the gas seal in reverse rotation is decreased and the open force consequently decreased by 4%. The modification on the same seal is done to enhance its performance at reverse rotation condition. The herringbone spiral grooves is used with different configuration, the new configurations are examined in the forward and reverse rotation direction. The analysis for the pressure distribution is done and its effect on the seal performance is examined. Seal performance is compared with standard one for all geometrical and operating conditions. At high forward rotational speed 10380rpm, the pressure at the end of the spiral groove is about 11.4% higher than the inlet pressure at the seal outer diameter, while at reverse rotation, the pressure is not increased in radial direction. The open force corresponding to reverse rotation increased with a value 1.5kN for both the 100 overlap and 50% forward overlap seal faces, but using seal face with 50% backward overlap failed to enhance the open force at reversal condition.

连续爆轰发动机燃烧室内压力分布的实验研究

近年来，由于爆轰高效的燃烧方式，其已成为各国学者关注的焦点。而连续爆轰发动机只需一次点火，便能在燃烧室内形成连续传播的爆轰波，从而可以提供持续稳定高推力的优越性能使其成为航空推进的一个重要研究方向。本文基于北京大学燃烧推进动力中心的连续爆轰实验设备，利用H2/O2混合燃料，结合实验数据对连续爆轰发动机内部压力分布进行了实验研究，分析了连续爆轰形成、稳定和熄灭的过程，计算了实验中连续爆轰的速度和旋转周期，为进一步研究连续爆轰发动机内部机理奠定了基础。 In recent years, detonation has become a hot topic of scientific research because of its high combustion efficiency. Continuous detonation engine will be able to form continuous propagation of detonation in the combustion chamber needing only once ignition, which can provide stable high thrust, and becomes an important research direction of aviation propulsion. Based on the continuous detonation experimental equipment of the Center of Combustion and Propulsion Power, Peking University, combined with the experimental data, internal pressure distribution of the continuous detonation engine is studied and the formation, stabilization and annihilation of the continuous detonation are analyzed. Also, the velocity and period of continuous detonation are calculated. All the works lay the foundation for further study of the internal mechanism of continuous detonation engine.

Stress analysis of functionally graded discs under mechanical and thermal loads: analytical and numerical solutions

AbstractThis study deals with stress analysis of functionally graded discs subjected to internal pressure and various temperature distributions, such as uniform T, linearly increasing To, and decreasing Ti temperatures in radial directions. For analytical study, the closed-form solutions for stresses and displacements are obtained by using the infinitesimal deformation theory of elasticity. For graded parameters, power law functions are used in analytical and numerical solutions. For numerical study, discs are modeled and analyzed by using a commercial finite element program, ANSYS®. Metal matrix composite, AlSiC, is selected as disc material. Results obtained both analytical and numerical solutions are found very well consistent with each other. The tangential stresses are found higher than the radial stresses at the inner surface for all thermal loads, and they vary from compressive to tensile and from tensile to compressive depending on the functionally graded material (FGM) properties and temperature loads. The radial stresses are found zero at the inner and outer surface and higher at one third of the disc section near the inner surface. They are also found as compressive and tensile stresses depending on the material properties and temperature loads.

Internal Flow and Axial Thrust Balancing of a Rocket Pump

Large axial thrust is produced on the rotor assembly of high-pressure rocket pumps. Thus, to ensure the reliability of bearings supporting the high rotational speed rotor, precise axial thrust balancing is essential. To realize complete axial thrust balancing, the back shroud of the main impeller is employed as the balance piston of a self-balancing type axial thrust balancing system in which the rotor assembly moves axially to compensate unbalance axial force. In this balancing system, which is often applied, complicated internal flow characteristics and pressure distributions are very important for predicting the precise characteristics of the axial thrust produced by the system. In the present study, a calculation method for analyzing the internal flow system taking into account effects of boundary layer conditions and angular momentum change in the impeller side-chambers is applied to the system combining the balance piston and grooves on the casing wall of the balance piston chamber. The analysis program is able to detect phenomena which could not be captured in past calculations and is effective for calculating internal flow characteristics much faster than possible with CFD analysis. A combination of balance piston and grooves on the casing wall of the balance piston chamber was confirmed to be suitable for extending the dynamic range of axial thrust balancing although installation of the grooves increased the leakage flow rate and friction torque at the same time.

Distribution of Internal Pressure around Bony Prominences: Implications to Deep Tissue Injury and Effectiveness of Intermittent Electrical Stimulation

The overall goal of this project is to develop interventions for the prevention of deep tissue injury (DTI), a form of pressure ulcers that originates in deep tissue around bony prominences. The present study focused on: (1) obtaining detailed measures of the distribution of pressure experienced by tissue around the ischial tuberosities, and (2) investigating the effectiveness of intermittent electrical stimulation (IES), a novel strategy for the prevention of DTI, in alleviating pressure in regions at risk of breakdown due to sustained loading. The experiments were conducted in adult pigs. Five animals had intact spinal cords and healthy muscles and one had a spinal cord injury that led to substantial muscle atrophy at the time of the experiment. A force-controlled servomotor was used to load the region of the buttocks to levels corresponding to 25%, 50% or 75% of each animal's body weight. A pressure transducer embedded in a catheter was advanced into the tissue to measure pressure along a three dimensional grid around the ischial tuberosity of one hind leg. For all levels of external loading in intact animals, average peak internal pressure was 2.01 ± 0.08 times larger than the maximal interfacial pressure measured at the level of the skin. In the animal with spinal cord injury, similar absolute values of internal pressure as that in intact animals were recorded, but the substantial muscle atrophy produced larger maximal interfacial pressures. Average peak internal pressure in this animal was 1.43 ± 0.055 times larger than the maximal interfacial pressure. Peak internal pressure was localized within a ±2 cm region medio-laterally and dorso-ventrally from the bone in intact animals and ±1 cm in the animal with spinal cord injury. IES significantly redistributed internal pressure, shifting the peak values away from the bone in spinally intact and injured animals. These findings provide critical information regarding the relationship between internal and interfacial pressure around the ischial tuberosities during loading levels equivalent to those experienced while sitting. The information could guide future computer models investigating the etiology of DTI, as well as inform the design and prescription of seating cushions for people with reduced mobility. The findings also suggest that IES may be an effective strategy for the prevention of DTI.

A Theoretical Study of the Internal Forces in a Hydraulic Vane Pump with Hypertrochoid Curve in the Inner Surface of its Stator

In the latest our works, Performance of a fixed displacement- hydraulic balance vane pump, theoretically and practically was studied by application of the basic hypertrochoid curve in the inner surface of its stator. Also the effect of the inertia force of the vanes on the performance of the pump with this curve was studied. This study presents a theoretical analysis of the internal pressure distribution in the pump, and of the resulting forces and torques applied to its components. This analysis is essential to the study of the pump dynamics and control, the pump design, and selection of the pump bearings. These forces are shown to be a function of the line pressure, the shaft rotational speed, the fluid bulk modulus, the fluid viscosity, and the design geometry. These forces are composed of two components: a continuous component due to the exposure of chambers to the line port, and an intermittent component due to a hydraulic lock phenomenon.

Numerical Study of the Effect of Wall Opening on Wind Pressures on Low-Rise Gable-Roofed Buildings

The external and internal wind pressure distribution characteristics on the roof surface of a low-rise gable-roofed building with wall openings are studied by means of the numerical simulation technique. The validity and accuracy of the numerical simulation is first demonstrated by comparison with the existing full-scale experimental results. In order to investigate the effect of wall opening locations on the pressure distribution, a parametric analysis is carried out to a typical gable-roofed building with different wall opening conditions. The analysis results indicate that wall opening locations have no significant effect on the external wind pressure but have considerable influence on the internal wind pressure. The cases of two opposite wall openings appear to be more favorable than those of single front wall openging for wind resistance of the building roof, if the angle of approaching wind flow from the inner normal line of the front wall is smaller than 90°.

Stabilizing Transpelvic Prosthetic Socket for a Patient with Spinal Cord Injury Sustaining Right Partial Hemipelvectomy and Left Hip Disarticulation

A bucket-type transpelvic socket was fabricated for a man with paraplegia from spinal cord injury, who underwent right partial pelvic amputation and left hip disarticulation. His main problem was inability to sit due to asymmetrical pelvic shape. We prescribed a transpelvic prosthetic socket to enable him to sit again. The socket consisted of a dual structure: a hard frame and soft liner. The main features of the socket were redistribution of pressure to prevent recurrence of pressure ulcer, and a slightly backward tilt to maintain a comfortable sitting position. In addition, the socket had small air holes for ventilation; a big window in the abdominal area for management of stoma and cystostomy; and two straps for donning it independently. In addition, we confirmed the internal pressure distribution in the socket by a pressure mapping system to prevent reoccurrence of skin trouble. Finally, the patient regained independence in activities of daily living, including driving a car, after two months of rehabilitative training.

The ELBA force field for coarse-grain modeling of lipid membranes.

A new coarse-grain model for molecular dynamics simulation of lipid membranes is presented. Following a simple and conventional approach, lipid molecules are modeled by spherical sites, each representing a group of several atoms. In contrast to common coarse-grain methods, two original (interdependent) features are here adopted. First, the main electrostatics are modeled explicitly by charges and dipoles, which interact realistically through a relative dielectric constant of unity (). Second, water molecules are represented individually through a new parametrization of the simple Stockmayer potential for polar fluids; each water molecule is therefore described by a single spherical site embedded with a point dipole. The force field is shown to accurately reproduce the main physical properties of single-species phospholipid bilayers comprising dioleoylphosphatidylcholine (DOPC) and dioleoylphosphatidylethanolamine (DOPE) in the liquid crystal phase, as well as distearoylphosphatidylcholine (DSPC) in the liquid crystal and gel phases. Insights are presented into fundamental properties and phenomena that can be difficult or impossible to study with alternative computational or experimental methods. For example, we investigate the internal pressure distribution, dipole potential, lipid diffusion, and spontaneous self-assembly. Simulations lasting up to 1.5 microseconds were conducted for systems of different sizes (128, 512 and 1058 lipids); this also allowed us to identify size-dependent artifacts that are expected to affect membrane simulations in general. Future extensions and applications are discussed, particularly in relation to the methodology's inherent multiscale capabilities.