All in an engineer’s life

As a step toward resolving current discrepancies among ultrahigh-pressure melting curves obtained with the laser-heated diamond cell, we critically evaluate two aspects of the experiments that require further examination: (i) the criteria used to detect that melting has taken place, and (ii) the methods employed for measuring spatially variable temperatures. A review of recent efforts illustrates how defining reliable melting criteria remains problematical in many experiments, whereas current and prospective advances in imaging spectroradiometry can yield robust methods for determining the temperature distribution within the laser-heated diamond cell.

This thesis presents the numerical simulation of fluid dynamics, as well as heat and mass transfer for drop impingement on a hot solid surface for low and high ambient pressures. The technical application ranges from effective thermal management strategies using spray cooling, safety aspects in high pressure nuclear reactors to process technology in chemical or food industry. It is reported in literature that wetting characteristics depend on the ambient pressure. Drop splash is suppressed at low ambient pressure. High ambient pressure encourages compressibility effects. The compressibility of both the liquid and vapour phase increases with increasing pressure. Thereby, the effects of compressibility on drop impingement is of interest. Up to now, no attempt has been made to investigate a full pressure range for the evaporative drop impingement process. In order to provide insights into evaporative drop impingement processes under various ambient pressures, numerical simulations are performed. CFD simulations are conducted using a finite volume discretisation method solving the Navier-Stokes equations. The volume of fluid method is utilised to resolve two-phase flow. The solver accounts for compressible fluid flow, heat and mass transfer due to evaporation across the free liquid-vapour interface, evaporation in the vicinity of the three-phase contact line, as well as for heat conduction within the solid substrate. The dynamic contact angle is implemented using a subscale model. Effects of low and high ambient pressure on the three-phase contact line are investigated in the well established so-called micro region model. The focus is the non-splashing drop-wall collision in a non-boiling, single-component evaporation regime. Ambient pressure ratios ranging between p/pcr = [8*10^{-3} ... 0.5], Reynolds and Weber numbers ranging between Re = [600 ... 1300] and We = [10 ... 50] are investigated. The wall temperature is above saturation but below Leidenfrost temperature. The wall superheat is in the order of 10 K. Different parameter studies are dedicated to investigate the influence of low and high ambient pressures on the evaporative drop impact processes. Within one parameter study, dimensional drop impact parameters are kept constant, such as drop diameter, impact velocity and wall superheat. Caused by the variation in ambient pressure, material properties of the fluid change. Consequently, non-dimensional groups are changing, indicating a shift in dominant forces. Another parameter study keeps non-dimensional groups constant. Further parameter studies focus on the influence of the vapour phase on the drop impact outcome, especially for high ambient pressure. Within this work, results are presented for different length scales. The modelling of the vicinity of an evaporating three-phase contact line indicates a strong influence of the ambient pressure on the apparent contact angle and the heat being transferred in the micro region. For increasing pressure, the contact angle increases whereas the transferred heat has a local maximum within the investigated pressure range. For the macro-scale drop impingement process, strong influence on the fluid dynamics and heat transfer is identified. In summary, numerical simulations of the evaporative drop impact and the modelling of micro-scale thermodynamic effects for low and high ambient pressure are investigated in the present thesis. The results increase the understanding of the influence of pressure on the fluid dynamics, as well as the heat and mass transfer. Correlations for the maximum spreading ratio, spreading duration, as well as transferred energy and mass are reported. The findings are expected to improve design concepts for technical applications within the investigated parameter range.

Thick-walled cylinders such as gun barrels, high pressure containers, and rocket shells are designed to withstand high pressure. The cylinder material may crack if the induced pressure exceeds the material yield strength. Therefore, the thick-walled cylinders are autofrettaged in order to withstand very high pressure in service condition. The most commonly practiced autofrettage processes are hydraulic autofrettage and swage autofrettage. Hydraulic autofrettage involves very high internal pressure at the bore of the cylinder, and in swage autofrettage an oversized mandrel is pushed through the cylinder bore to cause the plastic deformation of the inner wall of the cylinder leaving the outer wall at the elastic state. This results in compressive residual stresses at and around the inner wall of the cylinder, which reduces the maximum stress in the cylinder during next stage of loading by pressurization. Both the processes are well established, but still there are certain disadvantages associated with the processes. The present work proposes a novel method of autofrettage for increasing the pressure carrying capacity of thick-walled cylinders. The method involves only radial temperature gradient in the cylinder for achieving autofrettage. The proposed process is analyzed theoretically for thick-walled cylinders with free ends. The numerical simulations of the process for typical cases and preliminary experiments show encouraging results for the feasibility of the proposed autofrettage process.

The American Heart Association (AHA) High Blood Pressure Research Conference is considered to be among the most important and prestigious medical meetings on hypertension in the world, designed as a scientific program that focuses on disseminating information about recent advances in hypertension research. This program provides an opportunity and platform for learning, interacting, and networking among scientists, clinicians, and allied health care workers. The 2009 meeting was an enormous success, with a record number of 749 registrants from more than 20 countries. The program committee and council chairs, Clinton Webb (high blood pressure research) and Jeff Sands (kidney in cardiovascular disease), are to be applauded. The council meeting was preceded by a 1-day workshop titled, “Systems Medicine Strategies in Hypertension: From Molecules to Patients,” and focused on state-of-the-art technologies and approaches to better understand molecular and physiological mechanisms of hypertension in experimental and clinical settings. The workshop, organized by Ernesto L. Schiffrin (McGill University), Thomas M. Coffman (Duke University), and Anna F. Dominiczak (University of Glasgow), attracted more than 250 registrants and was the largest ever at a Council for High Blood Pressure Research (CHBPR) meeting. World-renowned investigators led the workshop with presentations and discussions. The workshop concluded with a presentation given by Daniel Levy (Framingham, MA), who linked all of the topics of the workshop through his talk titled, “Genes, Molecules, Systems Biology, and Epidemiology: Bringing It Together Through Framingham.” This was a perfect foundation to start the official council meeting. The scientific program of the conference was abstract based and included more than 400 reviewed abstracts presented in oral and poster sessions. In addition, numerous named award lectures were given by the most outstanding investigators in the hypertension community. The objectives of the meeting were certainly met, and by the end of the 1.0-day workshop and 2.5-day conference, …

Influence of high atmospheric pressure on rabbit's eye were investigated with a specially devised pressure box. Rabbit was fixed in a cylindrical metal case in a natural position, put in the pressure box, and the eye was observed through glass windows of the box. (1) The width of pupil dilated under high atmospheric pressure (10-60 pounds) with the course of time but not quite in parallel with the degree of pressure. The dilation was not influenced by extirpation of cervical sympathetic ganglion. Atropinizing of the eye did not result in further dilation of the pupil under high pressure. (2) Threshold of the cervical sympathetic stimulation on pupil dilation rose under high pressure (5-60 pounds) with the course of time, but not quite in parallel with the degree of pressure. (3) The smallest luminosity difference required to produce pupil reaction became greater under high pressure (20-60 pounds) with the course of time under the pressure, but not quite in parallel with the degree of pressure. (4) The eye received structural damages under high pressure (20-60 pounds)-hemorrhage and hyperaemia in ciliary body, in retinal and choroid vessels, vacuoles in lens, in inner and outer nuclear layer and ganglion cell layer of retina, irregularities of inner and outer nuclear layer of retina, and exudation between retina and choroid. These damages were not proportional to the degree of pressure or to length of time during which the animal was kept under the high pressure, but rather depended on the rate of pressure change, the more rapid the pressure change, the more marked the damages.

Turbojet engine can be divided into three major sections including the compressor, combustion chamber and the gas turbine section. The relatively high temperature gas that passes through the high pressure turbine stages of a turbojet engine from the combustion chamber has a direct effect on the performance and efficiency of the gas turbine, which may hamper its longevity in the long run, particularly the turbine blades. The turbine blades extract energy from the high temperature gas and transfer the kinetic energy of the flowing gas to the compressor stages where it provides forward thrust and rotates the turbine shaft which drives the high pressure and low Pressure compressor fan blades. However, the ability of materials to withstand this high temperature is based on properties of such materials which can be attributed to advances in material selection, improvement techniques in terms of surface protection and cooling as well as manufacturing processes which this paper is based on. Material indices were derived for High Pressure (HP) turbine blades to determine materials that can resist yielding and creep condition when exposed to high temperature above 700°C in a turbojet engine gas turbine. Based on the material indices derived, CES software 2014 was used to generate graphs showing materials with adequate fracture toughness, fatigue strength, stiffness and yield strength property that can withstand the in-service condition of HP turbine blade. Considering all these properties in terms of relatively high temperature, Nickel based super alloys dominated the graphs but in terms of density, titanium alloys dominated as CES software gave the minimum density of nickel alloy (8150 kg/m3) as twice that of titanium alloy (4410 kg/m3). Although both alloys are very expensive, nickel based alloy particularly Nickel-Cr-Co-Mo Super alloy also known as Rene 41 was chosen because of its excellent corrosion property and high strength at elevated temperature (About 1000°C) which makes it suitable for conventional HP turbine blade application.

A Dynamic Simulation of a Subsea Separation and Boosting System for Offshore Petroleum Production. Summary The objective of this work is to develop a numerical model to simulate the operation of a Subsea Separation and Boosting System. In short, the system is composed of two separation vessels, two gas pipelines, one oil pipeline and a set of remotely controlled hydraulic valves. The numerical model simulates the transient behavior of the fluids in the whole system for typical initial and boundary conditions. The modeling of the flow of fluids in the pipelines was based on the simultaneous solution of the mass and momentum conservation equations that forms a pair of quasi-linear hyperbolic equations in terms of two dependent variables (velocity and hydraulic head) and two independent variables (distance along the pipe and time). The method of characteristics was applied to solve the system of two partial differential equations transforming it into four ordinary differential equations.. This method leads to an exact solution of the systems. Newton's method was used to solve the nonlinear system of equations resulting from the coupling of the pipelines conditions with the vessels conditions. Introduction Subsea separation processes applied to offshore petroleum production have been studied as one of the most promising ways to produce deep water hydrocarbon reserves. The main objectives of these devices are to increase the reservoir recovery factor and the wells' flowrates, by reducing the back pressure on the well head. This is achieved by splitting the incoming multiphase stream in two single phase streams and piping them to the platform. The objective of this work is to develop a numerical model describing the separation system as presented in fig. 1. Shortly it can be described as a system composed by two vessels, two gas pipelines one operating at high pressure (HP) and the other at low pressure (LP), one oil pipeline and a set of hydraulic control valves. The incoming multiphase stream, from a single well or a cluster of wells, feeds one of the vessels which is connected to the low pressure gas pipeline. In this low pressure vessel, during the feeding step, separation occurs between the two phases. The gas phase exits the system through the low pressure gas pipeline and the oil accumulates in the vessel. Simultaneously, the high pressure vessel, is transferring oil by action of high pressure gas injected from one platform which provides sufficient pressure difference that promotes liquid flow. Once the feeding and transferring steps occurring in the low and high pressure vessels, respectively, are completed, the set of valves changes the alignment of the pipelines between the vessels and another cycle starts. The numerical model simulates the transient behavior of the fluids during the cycles. It consists of simultaneous solution of the mass and momentum balance equations by the method of characteristics applied to the high and low pressure gas pipelines as well as to the oil pipeline. In the transferring step the system, comprising high pressure gas pipeline, oil pipeline and high pressure vessel is coupled and solved together. Simultaneously the feeding step is solved to low pressure gas pipeline, low pressure vessel and petroleum source. The whole system boundary conditions are given by the outlet compressor pressure for the upstream high pressure gas pipeline, by the gas scrubber pressure for downstream low pressure gas pipeline and by the surge tank pressure for the downstream oil pipeline. Gas Pipeline Modeling The one dimensional mass and momentum Eqs. for the gas flow in a pipeline are, respectively, written as [Wylie and Streeter, 1982]. P. 471

Effects of ethanol on body temperature of rats at high ambient pressure

Stress intensity factors for radial cracks in thick walled cylinders—III. Asymmetrical cracks

Thick-walled cylinders are widely used as compressor cylinders, pump cylinders, high pressure tubing, process reactors and vessels, nuclear reactors, isostatic vessels and gun barrels. In practice, cylinders are generally subjected to sudden and frequently drastic pressure fluctuations, such as the pressure generated in a gun barrel upon the firing of the weapon, pressure reversals in pump cylinders or in process reactors employing high-pressure piping, necessitating enhanced strength of such cylinders. A process for enhancing the strength of thick-walled cylinders has been in service, and is referred to as "autofrettage". It extends the service life of the cylinder. The autofrettage is achieved by increasing elastic strength of a cylinder with various methods such as hydraulic pressurization, mechanical swaging, or by utilizing the pressure of a powder gas. This research work deals with the hydraulic and mechanical autofrettage of metal tubes with the objective to attain enhanced strength. Five metal tubes are taken randomly for analysis purpose. The experimental data for five metal tubes is obtained to analyze the behavior of different parameters used during, before, and after autofrettage process. For this research, two-stage autofrettage is taken into consideration. The modeling of the metal tube is carried out in WildFire-ProEngineering, and for analysis purpose, finite element software ANSYS7 & COSMOS are used. The graphical analysis of swage autofrettage is carried out using MATLAB7. The results are validated using available experimental and numerical data.

Wentorf, R. H., Jr. (Ed.), Modern Very High Pressure Techniques, Butterworths, Washington, D. C, 247 pp., 1962, $11.25.This collection of papers on apparatus for very high pressure (>20 kb) research was brought together to acquaint the ‘newcomer’ with the major lines of development of equipment, some experimental results, and key references to the literature on high pressure. The book appears, after some delay, on the heels of Progress in Very High Pressure Research (see review in Trans. Am. Geophys. Union, 42, 436, 1961) which deals not only with high pressure apparatus but mainly with the kinds of data which can be collected in such apparatus.

Polyacetylene is an insoluble conjugated polymer that can be obtained by using conventional ZieglerNatta catalysts [1-3]. Substituted acetylenes, having bulky phenyl groups such as phenylacetylene, produce oligomers not exceeding the number-average molecular weight of 7500 and insoluble polymers by the use of the Ziegler-Natta catalyst [4, 5]. Masuda et al. found in 1974 that group 5 and 6 transition metal catalysts (W and Mo based catalysts) are effective for phenylacetylene polymerization [4, 6]. These polyacetylenes with substituents have attracted much attention as electrical and non-linear optical materials [7-9]. The application of pressure is well known to influence the structure, properties and reactions of substances [10-15]. Acetylene was polymerized at room temperature by a reaction-induced high pressure [11]. A previous paper reported the synthesis of a phenylacetylene oligomer under high pressure (0.11-0.92 GPa) and high temperature (100-200 °C) [16]. In the study reported here, the polymerization of phenylacetylene was carried out at room temperature under high pressure (1.5 GPa). Visible absorption spectroscopy and gel permeation chromatography (GPC) were utilized to characterize the structure of the product. Phenylacetylene (molecular weight 102.14, liquid) in the form H--C=--C--CoH 5 (Wako Pure Chemical Industries Ltd, Japan) was used for the reaction without further purification [purity >99% (gas chromatography)]. The reaction of phenylacetylene under high pressure was performed with a specially designed super high hydrostatic pressure reactor (Hikari High Pressure Machinery Co., Japan). The block diagram of the reactor is schematically illustrated in Fig. 1. Paraffin was used as a pressure transmitting medium. The pressure in the super high pressure vessel was increased ten times compared with that in the high pressure vessel through the hydraulic intensifier. Pressure was measured using a Bourdon gauge (Heise gauge) and a manganin coil gauge. The pressure was displayed on a digital manometer and was recorded on a recorder. The specimen (about 2 g) was packed into a polytetrafluoroethylene cell (inside diameter 8 mm, length 40 mm). After closing the cell, it was introduced into the super high pressure vessel. The specimen was compressed at 1.5 GPa by a motor driven oil pump and substantially reacted at room temperature (2225 °C) for constant times of 1-300 h. After reaction under high pressure, the product was decompressed and removed from the cell. Visible absorption spectra of the products in a quartz cell (specimen path length 10mm) were recorded on an Ultraviolet (UV)-visible recording spectrophotometer (Shimadzu UV-2100). The spectrum was measured in the 400-800 nm region. The molecular weight of the product was determined using a liquid chromatograph (Japan Analytical Industry Co., Ltd, LC-08) consisting of a UV absorption detector (wavelength 254nm) and a column. Chloroform was used as a mobile phase at

This paper tries to explain the interesting field data that indicate a surface axisymmetric circumferential crack inside a hollow cylinder (circumferential crack) shows tendency toward crack arrest, when the temperature of the fluid inside the cylinder experiences sinusoidal fluctuation (thermal striping). For this purpose, transient stress intensity factor (SIF) range of a circumferential crack in a finite-length thick-walled cylinder with rotation-restrained edges, under thermal striping, was analyzed. It was assumed that the fluid temperature changes sinusoidally and that heat transfer coefficient is constant. First an analytical temperature solution for the problem was obtained and it was combined with our SIF evaluation method derived based on superposition principle and Duhamel’s analogy. Then we defined the maximum SIF range as the maximum value of the SIF range during thermal striping and studied the characteristic change of this maximum SIF range with the variation of crack depth to explain the crack arrest tendency. Results showed that the maximum SIF range under thermal striping decreases monotonously when crack depth is varied to become deeper than a specific value, which corresponds to the crack arrest tendency.

Abrasive waterjet (AWJ) cutting is a machining process to cut wide range of materials from soft materials such as rubber, leather to hard materials such as metals by means of a high-velocity slurry jet, formed as a result of injecting abrasive particles into a waterjet. The machining action is the result of these particles impacting against a workpiece with a high velocity. Conventional AWJ equipments generate water pressures up to 400 MPa (=4000 bar = 58000 psi) and use orifices whose diameters are in the range of 0.08 mm to 1 mm to generate plain waterjet. The abrasive particles of sizes 0.07 mm to 0.36 mm in diameter entrain to the jet former with air and mix with the waterjet in the mixing chamber to form the three phase slurry jet. The abrasive particles are accelerated and focused in the focusing tube. The width of the focusing tube determines the cutting width which is in the range of 0.5 mm to 1.5 mm in diameter. This study investigates the applicability and the performance of waterjet (WJ) and AWJcutting process beyond 400 MPa water pressure, which is called ultra-high pressures during the study. One of the objectives is to expand the application domain of the process. With higher water pressure, plain WJ is capable of cutting harder materials and it is possible to cut intricate details with AWJ due to the availability of high energy density with small orifices. Moreover, reduction in cutting costs is expected as a result of higher feed speeds or reduced abrasive consumption. The initial focus of the research is to provide guidelines to develop a reliable AWJ cutting system above 400 MPa. It was shown that the plastic deformation takes place at the thick walled cylinders subjected to internal pressure of more than 700 MPa with the current types of materials that are generally used in high pressure components. Therefore, imposing compressive residual stress to the bore of the cylinder is necessary for the parts such as high pressure intensifier cylinder where plastic deformation is unacceptable. Autofrettage and multi layer construction are the two techniques to create residual stresses in the cylinder. An optimum autofrettage pressure exists due to the Bauschinger effect. Therefore, a multi layer cylinder construction provides cylinders with higher pressure capacity. A simplified model for predicting the pressure output for double acting pressure intensifiers is presented after the design considerations for thick walled cylinders in order to estimate the required attenuator volume and the high pressure cylinder dimensions to limit the pressure fluctuations. The model is in good agreement with the pressure measurements. The energy conversions and the related efficiencies during the AWJ formation process provide a perspective to the performance of the process. Energy density of the plain and abrasive waterjet is defined to correlate with the cutting performance. Reducing the focusing tube diameter and increasing the water pressure are the most beneficial methods to increase the energy density. Other methods such as increasing the orifice diameter or reducing the feed speed are in conflict with cutting intricate details and economical considerations. With the insight gained at the previous step, the performances of plain and abrasive waterjet are evaluated. The increase in pressure results in a more scattered jet. A diverted jet generates wider cuts with wider damaged zones and rounded edges in WJ cutting. In AWJ cutting, it accelerates the wear of the entry region of the focusing nozzle. The experiments show that the length and diameter of upstream tube play an important role in jet quality. The turbulences in the flow are reduced in the upstream tube. It should be sufficiently large to make the flow laminar. Moreover, when the streamlines are guided towards the orifice with a conical seal, the resultant jet disintegrates later. After the quality of the jet is ensured, the cutting performance tests are conducted. The maximum feed rate increases more than the hydraulic power of the waterjet which shows that increasing the pressure leads to a more power efficient process. Moreover, at the same hydraulic power, the smaller jets perform better. On the other hand, the increase in depth of cut with pressure is directly proportional with the hydraulic power. It is proposed that the depth of cut is directly proportional with the energy density of the jet. However, at the low feed rates the relation is no longer linear. Therefore, the feed rate term of the energy density equation is modified to predict the depth of cut. Due to the cutting mechanism of the plain waterjet, the surface quality is poor with burrs in the case of metals and fiber damages in the case of composite materials. Therefore, plain waterjet cutting is suitable for separating instead of precision cutting of metal sheets and composites. The mixing and acceleration of the particles with a waterjet determine the cutting ability of AWJ. It becomes less efficient at high abrasive loads. The momentum from the plain waterjet to the abrasives transfers more efficient with the increase in pressure at the same abrasive load ratio. The efficiency of power transferred from the water to the abrasives decreases when the abrasive load ratio exceeds 0.3 for low focusing tube to orifice diameter (df / do) ratios and 0.4 for high df /do ratio. The optimum abrasive flow rate does not depend on pressure. As it was in the plain waterjet, the energy density of the jet correlates well with the cutting ability of the jet. The linear relation between these parameters becomes non-linear at high energy densities due to the increased energy losses at longer traveling lengths through the material at higher depths of cut. The final consideration of this study is the economical aspects of ultra-high pressure AWJ cutting. The cost advantage depends on the increase of the cost of the pump, the maintenance and the life of the consumables with the pressure increase. The pressure increase is cost effective if the investment costs and maintenance costs are below certain values. If several engineering issues such as the lifetimes of the critical components and the availability of wear resistant sufficiently long focusing tubes are solved, the ultra-high abrasive waterjet cutting can be implemented successfully to industrial applications.

Predictions of the mixture formation process inside gasoline DI engines are strongly required to improve both the fuel consumption rate and the exhaust emissions. Swirl-type injectors are commonly used for gasoline DI engines, as its spray characteristics are favorable for gasoline DI engines. The spray formation of a swirl-type injector consists of a liquid sheet and droplets that arise from the breakup of the liquid sheet. Numerical simulations of free sprays formed by a swirl-type injector are carried out on the basis of a method of DDM (Discrete Droplet Model) with employing different models for the breakup of the liquid sheet and that of droplets downstream. The breakup of the liquid sheet is modeled by Reitz's wave breakup model while that of droplets downstream adopts TAB (Taylor Analogy Breakup) model. Schematic diagram is illustrated in Figure 1. In this study, the boundary condition of the ambient pressure is set at two values ; a negative pressure and a high pressure. The droplet deformation calculated by the breakup model is incorporated into the drag force term to take the influence of the drag variations into account. The results of calculated parcels on centered vertical cross-section are shown in Figure 2. Figure 2(a) is the result assuming that the drag force is of a rigid sphere (without droplet deformation), while Figure 2(b) is the result assuming that the drag force is of an ellipsoid (with droplet deformation). As a result, by taking the drag force variation due to deformation of droplets into account, calculations under high ambient pressure can reproduce the change of spray shape. The drag force of droplets and the pressure difference of spray inside and outside cone contribute to the change of the spray shape. This pressure difference is small when the ambient pressure is low.