bluuebunny/crossref_metadata_2025 huggingface dataset:
A Computational Investigation of Modified Intake Ports to Improve Scavenging in a Heavy-Duty Two-Cycle Diesel Engine
Authors: Dolak Jonathan , Bandyopadhyay Deep
Published: July 2013

The objective of this research was to improve the scavenging process on a heavy-duty, two-cycle, medium speed, diesel engine (710 cubic inches of displacement per cylinder) under high load. It was desired to expel as much of the residual gases in the combustion chamber during the scavenging process, without having the fresh intake air escaping through the exhaust valves. This allowed a cooler intake charge with a higher oxygen concentration to be used. Having a cooler air intake charge was beneficial for emissions and performance. The power assembly configuration for the investigation was a two-cycle engine with intake ports around the bottom portion of the cylinder liner and four exhaust valves in the cylinder head. The main variable in this study was the axial location of every other intake port on the cylinder liner. When the axial location increased, this created pseudo longer intake timing. To keep the amount of trapped mass constant, the exhaust valves remained opened longer. The effectiveness of the scavenging process was estimated by the concentration of trapped oxygen (O2), carbon dioxide (CO2), and water vapor (H2O) along with the average temperature of the intake charge at the end of scavenging. The final part of the research explored each modified cylinder liner under full load, combustion operating conditions, while varying the injection timings. Soot, nitrogen oxides (NOx) and fuel consumption were also examined. A proprietary, multi-dimensional, computational fluid dynamic (CFD) code was used for the modeling work. Sculptor™, a commercial software package, was used to morph the cylinder liner.

The results showed that by increasing the axial location of the intake ports, a cooler intake charge with higher oxygen and lower carbon dioxide and water vapor concentrations resulted. This suggested more exhaust gases were expelled from the combustion chamber and replaced with fresh air. The rate of improvement slowed down after increasing the intake port axial location by 15.0 mm. In the next step, the compression and combustion process of the different port locations was studied. The cases with higher intake port axial locations were found to have lower pressure throughout the compression and power cycles. The temperature was lower for cases with elevated intake ports, until combustion started. The final part of the research studied the modified intake port cases under combustion simulation, while varying the injection timing. Next, the results showed an improvement in soot and fuel consumption with an increase in NOx for a given injection timing. However, while injection timing was varied, it was possible to improve NOx, soot, and fuel consumption simultaneously when compared to the baseline.
Managing the Transition Between Low Temperature Combustion and Conventional Diesel Combustion During a Load Change
Authors: Sarangi Asish K. , Garner Colin P. , McTaggart-Cowan Gordon P. , Davy Martin H. , Wahab Emad A. , Peckham Mark S.
Published: July 2013

High-EGR diesel low temperature combustion breaks the traditional diesel NOx-PM trade-off, thereby facilitating ultra-low NOx emissions with simultaneously low smoke emissions. High-EGR LTC is currently limited to low and medium load and speed conditions. Therefore, in order to implement a high-EGR diesel LTC strategy in a passenger vehicle, a transition to conventional diesel operation is required when either a high load or high speed is demanded. This transition must be carefully managed to ensure smooth operation and to avoid excessive pollutant emissions—a task that is complicated by the markedly different response time-scales of the engine’s turbocharger, EGR, and fuelling systems.

This paper presents the results of a combination of numerical simulation and steady-state engine experiments that describe the performance and emissions of an automotive-sized 2 litre turbocharged diesel engine during a rapid transition from high-EGR LTC to conventional diesel operation. The effects of load change at constant engine speed during the Extra-Urban Drive Cycle (EUDC) part of the New European Drive Cycle (NEDC) are first evaluated using a one-dimensional engine simulation (Ricardo WAVE). The inputs to the model are; the initial and final fuelling quantities, the duration of the transient events, and the response of the engine’s control systems. The WAVE model outputs the intake manifold pressure and EGR level for each cycle during the transition.

The predicted intake pressure, EGR rate and the corresponding known injected fuel mass for each individual cycle are used to define a set of ‘pseudo-transient’ test conditions—matching the conditions encountered at discrete points within the modelled transient—for subsequent steady-state engine testing on a 0.51 litre AVL single cylinder diesel engine. These test conditions are established on the engine using independently controllable EGR and boost systems and the corresponding emissions (NOx, smoke, CO, and THC) and performance data (GISFC) were recorded. The experimental emissions and performance data are subsequently presented on a cycle-by-cycle basis. The results of this study provide significant insight into the combustion conditions that might be encountered during mode switching and their deleterious effect on emissions and performance. Strategies to mitigate these effects are examined.
Low Temperature Combustion (LTC) Optimization and Cycle-by-Cycle Variability Through Injection Optimization and Gas-to-Liquid (GTL) Fuel-Blend Ratio
Authors: Michailidis A. D. , Stobart R. K. , McTaggart-Cowan G. P.
Published: July 2013

The advent of common rail technology alongside powerful control systems capable of delivering multiple accurate fuel charges during a single engine cycle has revolutionized the level of control possible in diesel combustion. This technology has opened a new path enabling low-temperature combustion (LTC) to become a viable combustion strategy. The aim of the research work presented within this paper is the understanding of how various engine parameters of LTC optimize the combustion both in terms of emissions and in terms of fuel efficiency. The work continues with an investigation of in-cylinder pressure and IMEP cycle-by-cycle variation. Attention will be given to how repeatability changes throughout the combustion cycle, identifying which parts within the cycle are least likely to follow the mean trend and why. Experiments were formulated to include rail pressure, injection settings of single injection and split-injection of varying dwell times. All injection conditions were phased across several crank-angles to demonstrate the interaction between emissions and efficiency. These tests are then repeated with blends of 30% and 50% gas-to-liquid (GTL)-Diesel blends in order to determine whether there is any change in the trends of repeatability and variance with increasing GTL blend ratio. Compression-ignition has been traditionally regarded as sufficiently stable that such investigation is irrelevant. Major improvements have been made, however, both to the understanding of compression-ignition and its control. Re-assessing and investigating how pressure repeatability fluctuates over the combustion cycle, especially in atypical engine conditions will help our understanding of combustion and facilitate a more accurate optimization of the combustion process.
Simultanous Transient Surface Temperature and Heat Flux Measurements in a Large Bore Two-Stroke Diesel Engine
Authors: Christiansen Caspar Ask , Mayer Stefan , Schramm Jesper
Published: July 2013

Surface temperature measurements were performed in a large bore two-stroke diesel engine used for ship propulsion. A specially designed fast-response surface thermocouple was used together with an embedded standard K-type thermocouple to measure surface temperature and heat flux with high temporal resolution.

Heat flux calculations were carried out both analytically and numerically showing good agreement between the results. Measurements were carried out at three different engine load conditions (25%, 30% and 50% load) in one of the fuel atomizers in the cylinder head. Cyclic surface temperature variations of up to approximately 80 K with a peak temperature of 860 K were observed.

The magnitude of the perturbation of the temperature field due to the presence of the thermocouples was investigated by three dimensional CFD simulations.
Simultaneous High-Speed Two-Color Thermometry and Laser-Induced Incandescence Soot Measurement in a Small-Bore Optical Engine Fueled With JP-8
Authors: Zha Kan , Yu Xin , Jansons Marcis
Published: July 2013

In-cylinder soot measurements obtained with a high-speed two-color method are compared to those simultaneously determined by the laser-induced incandescence (LII) technique in a single-cylinder, optically-accessible diesel engine fueled with JP-8. A double injection strategy was chosen to reduce pressure rise rates during operation at light load (2 bar IMEP) conditions. Injection timing was optimized for peak efficiency, at which point sufficient soot was produced to provide ample signal for both optical diagnostic techniques. Application of the two-color method to a high-speed CMOS camera allows the crank-angle-resolved observation of soot temperature and soot optical depth (KL) evolution, while LII provides soot volume fraction distribution at a known axial location in the cylinder independent of combustion gas temperature. Comparison of soot KL and LII signal at various stages of combustion shows high spatially-averaged correlation of the two signals near TDC. The degree of correlation decreases as the piston bowl descends and the line-of-sight soot KL value increasingly includes soot volumes not in the path of the laser sheet, the location of which is fixed 6.5 mm below the fire deck. The correlation between the two parameters again increases during the late cycle, indicating that in the later phases of combustion soot occurs in the squish zone above the piston bowl. Spatial cross-correlation of the two signals is weak, but increases in the highly luminous period immediately following heat release and illustrating a high degree of soot stratification. Soot KL and temperature evolution over a cycle are presented, which show no indication of being affected by the LII laser fluence.
Optimization of Skewed Injection for High Swirl, Two-Cycle, Diesel Engine
Authors: Bandyopadhyay Deep
Published: July 2013

Generally, two-stroke engines have inherent advantage of higher swirl, as compared to four-stroke engines. Higher swirl helps with better mixing and atomization for mechanical and low pressure, electronic, unit injectors. With the introduction of higher injection pressure, the advantage of swirl reduced to a point in which it started to have a negative impact. In this work, the goal was to optimize a high pressure, common rail injection system for heavy-duty, two-cycle, medium speed, diesel engine (710 cubic inches of displacement per cylinder) under high load. A proprietary multi-dimensional computational fluid dynamic (CFD) code was used for the modeling work. Here, we optimized the new, skewed injection system, which takes advantage of swirl and further helps in atomization of spray. The spray in this study is introduced at a radial angle, which is aligned either along or against the swirl direction. The results showed significant improvement in combustion efficiency. Combustion efficiency is estimated as a decrease in fuel consumption and CO values. Emission parameters, such as nitrogen oxide and soot were also studied and showed significant reductions.
HCCI Operability Limits: The Impact of Refinery Stream Gasoline Property Variation
Authors: Lacey Joshua S. , Sathasivam Sakthish R. , Filipi Zoran S. , Cannella William J. , Fuentes-Afflick Peter A.
Published: July 2013

HCCI combustion is highly dependent on in-cylinder thermal conditions favorable to auto-ignition, for a given fuel. Fuels available at the pump can differ considerably in composition and auto-ignition chemistry, hence strategies intended to bring HCCI to market must account for the fuel variability.

To this end, a test matrix consisting of eight gasoline fuels composed of blends made solely from refinery streams was investigated in an experimental, single cylinder HCCI engine. The base compositions were largely representative of gasoline one would expect to find across the United States, although some of the fuels had slightly lower average octane values than the ASTM minimum specification of 87. All fuels had 10% ethanol by volume included in the blend. The properties of the fuels were varied according to research octane number (RON), sensitivity (S=RON−MON) and the volumetric fractions of aromatics and olefins.

For each fuel, a sweep of the fuelling was carried out at each speed from the level of instability to excessive ringing to determine the limits of HCCI operation. This was repeated for a range of speeds to determine the overall operability zone. The fuels were kept at a constant intake air temperature during these tests.

The variation of fuel properties brought about changes in the overall operating range of each fuel, as some fuels had more favorable low load limits, whereas others enabled more benefit at the high load limit. The extent to which the combustion event changed from the low load limit to the high load limit was examined as well, to provide a relative criterion indicating the sensitivity of HCCI range to particular fuel properties.
Effects of a Low Octane Gasoline Blended Fuel on NVO Enabled HCCI Load Limit, Combustion Phasing and Burn Duration
Authors: Hagen Luke M. , Manofsky Olesky Laura , Bohac Stanislav V. , Lavoie George , Assanis Dennis
Published: July 2013

Homogeneous Charge Compression Ignition (HCCI) combustion allows for the use of fuels with octane requirements below that of spark-ignited engines. A reference gasoline was compared with iso-octane and a low octane blend of gasoline and 40% n-heptane, NH40. Experiments were conducted on a single cylinder engine operating with negative valve overlap (NVO). The fuel flow rate per cycle was compensated based on the lower heating value to maintain a constant energy addition across fuels.

Iso-octane and gasoline demonstrated similar maximum load, achieving a gross IMEPg of ∼430 kPa, whereas the NH40 demonstrated an increased IMEPg of ∼ 460kPa. The NH40 could be operated at a later phasing compared with the higher octane fuels, and exhibited a shorter burn duration at a given fueling rate and phasing. These results could be due to compositional differences, as NH40 required less NVO compared to iso-octane and gasoline, leading to less thermal and compositional stratification, as well as a higher O2 concentration and less residual gas. Additionally, the NH40 fuel demonstrated a higher intermediate temperature heat release than the higher octane fuels, potentially contributing to the shorter burn duration. Overall, these results demonstrate clear benefits to NVO enabled HCCI combustion with low octane fuels.
Fundamental Study of Spray and Partially Premixed Combustion of Methane/Air Mixture
Authors: Askari Omid , Metghalchi Hameed , Moghaddas Ali , Hannani Siamak Kazemzadeh , Ebrahimi Reza
Published: July 2013

This study presents fundamentals of spray and partially premixed combustion characteristics of directly injected methane inside a constant volume combustion chamber (CVCC). The constant volume vessel is a cylinder with inside diameter of 135 mm and inside height of 135 mm. Two end of the vessel are equipped with optical windows. A high speed complementary metal oxide semiconductor (CMOS) camera capable of capturing pictures up to 40,000 frames per second is used to observe flow conditions inside the chamber. The injected fuel jet generates turbulence in the vessel and forms a turbulent heterogeneous fuel–air mixture in the vessel, similar to that in a compressed natural gas (CNG) direct injection engine. The fuel–air mixture is ignited by centrally located electrodes at a given spark delay timing of 1, 40, 75 and 110 milliseconds after fuel injection has been completed to reflect different turbulence intensities. For comparative study, by increasing the spark delay timing to five minutes, a homogeneous premixed mixture is also prepared in the vessel which provides information on laminar homogeneous mixture combustion.

Spray development and characterization including spray tip penetration, spray cone angle and overall equivalence ratio were investigated under 30–90 bar fuel pressures and 1–5 bar chamber pressure. Flame propagation images and combustion characteristics were determined via pressure-derived parameters and analyzed at a fuel pressure of 90 bar and a chamber pressure of 1 bar at different stratification ratios (from 0% to 100%) at overall equivalence ratios of 0.6, 0.8 and 1.0. Shorter combustion duration and higher combustion pressure were observed in direct injection-type combustion at all fuel air equivalence ratios compared to those of homogenous combustion.
Experimental Investigation in a Hydrodynamic Taper Land Thrust Bearing
Authors: Henry Y. , Bouyer J. , Fillon M.
Published: July 2013

An experimental study is presented with the main objective of understanding the hydrodynamic behavior of a taper land thrust bearing with fixed geometry. The experimental results were obtained on an original test rig designed at the Pprime Institute. An extensive instrumentation of the thrust bearing allows a precise evaluation of various elements such as the temperature, the film thickness or the friction torque. The results are in good agreement with other literature surveys. However, an important difference of the measured parameters was found between the pads. The authors consider that this is most probably caused by the imperfections of the active surface produced during machining.
Piston Ring Load Carrying Capacity: Influence of Cross-Hatching Parameters
Authors: Bouassida H. , Biboulet N. , Sainsot P. , Lubrecht A. A.
Published: July 2013

Energy and environment are of major concern in internal combustion engine component design. The piston ring-cylinder liner (PRCL) contact plays an essential part in design and is highlighted in this study. In fact, the rings ensure the sealing property, reducing the environmental impact by avoiding lubricant contamination (blow-by) and lubricant consumption. Unfortunately, when sealing, the rings generate between 11 to 24% of the friction losses in an internal combustion engine [1], thus reducing the energy efficiency of the engine.

The cylinder liner surface features a special micro-geometry, a classical one is the cross-hatching pattern, obtained by honing. This texturing acts as a micro-bearing, oil reservoir and debris trap. Understanding the influence of texture parameters as groove depth and width or angle, will allow tribological improvements of the PRCL contact.

The 2D transient Reynolds equation has to be solved for this kind of surface. The statistical method using the Patir and Cheng [2] flow factors is widely used. This approach lumps the different components of the surface (grooves and plateaux) and does not consider the roughness directionality. Methods decoupling both components, like the homogenization method [3] are also used. Another alternative is to use a deterministic model on measured surfaces, but this is a “hugely” expensive approach. Multigrid methods [4] are used to drastically reduce the calculational cost.

The aim of the current study is to facilitate the understanding of measured surface calculations. Hence, analytical surfaces are used. They allow a flexible handling of the cross-hatching parameters. The plateaux are perfectly smooth and the grooves are sinusoidally shaped. The top ring is modelled using a parabolic profile. Periodic boundary conditions are used in the orthoradial direction and zero pressure conditions (Dirichlet) in the axial direction.

To investigate the effect of different parameters, various imposed film thicknesses are applied and the mean load carrying capacity (LCC) over time is calculated. When representing the LCC corresponding to each parameter compared to the smooth LCC, as a function of the logarithm of the minimum film thickness, the curves are quite linear for small values of the film thickness and then for larger values they converge to 1.
Polycrystalline Diamond Thrust Bearing Testing and Qualification for Application in Marine Hydrokinetic Machines
Authors: Lingwall B. A. , Cooley C. H. , Sexton T. N.
Published: July 2013

Polycrystalline diamond (PCD) bearings are designed for use in extreme environments; this includes process-fluid-lubricated applications such as those in oil and gas drilling turbines and marine hydrokinetic (MHK) energy machines. Past uses of PCD bearings in oil and gas down-hole tool applications have proven them to be robust, long lived, and rugged [1]. To be effective in MHK machines, PCD bearings must demonstrate adequate bearing efficiency and life in a submerged marine environment not nearly as severe as an oil well bore or a gas well bore. This paper discusses the advantages PCD bearings could provide when used in underwater MHK energy machines. Laboratory test results are presented that can help predict the performance of PCD in these MHK applications. Results from three types of tests are presented including tests that measure bearing capacity, those that observe and qualify hydrodynamic properties during testing, and those that evaluate diamond wear rates through a test representing the life time of a bearing in a MHK energy application. Failure tests conducted to measure bearing capacity revealed the PCD bearing could well endure conditions found in MHK machines, and coefficient of friction (COF) tests demonstrated the PCD ability to move from a boundary lubrication regime, to mixed mode lubrication, and then become hydrodynamic. The PCD wear test was designed to simulate years in the life of a tidal stream power generator, an MHK energy machine, and showed the PCD life is more than adequate for the MHK application. Bearing capacity, COF, and wear observed during laboratory testing illustrate that PCD thrust bearings can provide a robust, long lasting, and low maintenance bearing in MHK applications.
A Thermo-Mechanical Finite Element Analysis of Light Sliding Contact at the Head-Disk Interface
Authors: Liu Yuliang , Lou Jia , Bogy David B. , Zhang Guangyu
Published: July 2013

A three dimensional finite element model of a rigid sphere lightly sliding over an elastic-perfectly plastic multilayered medium under thermo-mechanical surface loading is developed in order to investigate the mechanical and thermal responses during the light sliding contact of a spherical corner or thermal protrusion of a slider with a rotating disk. In this simulation, the effects of the magnetic recording layer thickness t and sliding contact parameters such as normal load F and friction coefficient μ on maximum temperature Tmax of head-disk interface (HDI) and maximum scratch depth h on the multilayered disk media are analyzed for both glass and aluminum disks. The results show that the magnetic recording layer thickness t has a negligible effect on the maximum temperature Tmax of the HDI and scratch depth h on the disk for both types of substrates, but the sliding contact parameters strongly affect the temperature variation and mechanical deformation of the HDI. In addition, the effect of the disk material is also very pronounced.
Perfect Mechanical Sealing in Rough Elastic Contacts: Is it Possible?
Authors: Kudish Ilya I. , Cohen Donald K. , Vyletel Brenda
Published: July 2013

Generally, it is assumed that under any applied force there will always be some gap between the surfaces in a contact of rough elastic surfaces resulting in a discontinuous (i.e. multiply connected) contact. The presence of gaps along the line contact relates to the ability to form an adequate mechanical seal across an interface. This paper will demonstrate that for a twice continuously differentiable rough surface with sufficiently small asperity amplitude and/or sufficiently large applied load and/or sufficiently low material elastic modulus singly connected contacts exist. Solution of a contact problem for a rough elastic half-plane and a perfectly smooth rigid indenter with sharp edges is considered. First, considered a problem with artificially created surface irregularity and it is shown that for such a surface the contact region is always multiply connected. An exact solution of the problem for an indenter with sharp edges resulting in a singly connected contact region is considered and it is conveniently expressed in the form of a series in Chebyshev polynomials. A sufficient (not necessary) condition for a contact of an indenter with sharp edges and a rough elastic surface to be singly connected is derived. The singly connected contact condition depends on the surface micro-topography, material effective elastic modulus, and applied load. It is determined that in most cases a normal contact of a twice continuously differentiable rough surface with sufficiently small asperity amplitude and/or sufficiently large applied load is singly connected.
Stiffness and Damping Analysis of a Single EHL Contact Between the Rolling Element and Raceways Under Wider Load and Speed Ranges
Authors: Zhang Yuyan , Wang Xiaoli
Published: July 2013

The numerical analysis for the equivalent stiffness and damping of a single EHL contact between the rolling element and raceways under wider load and speed ranges is presented. The unsteady EHL model and free vibration model are applied to describe the motion characteristics of the rolling element. The inlet length and dimensionless natural frequency are determined according to the corresponding working load and speed. The DC-FFT method is implemented in order to increase the computational efficiency associated with elastic deformations and the semi-system approach is applied to ensure solution convergence under severe conditions which makes the analysis of stiffness and damping in the larger ranges of load and speed possible. The numerical results demonstrate that the stiffness increases with the increasing load and decreases with speed. However, the changes of the damping are complex, which are different in various load and speed ranges, especially under heavier load and higher speed. It is also indicated that the stiffness and damping increases with the increase in ambient viscosity and the decrease in pressure-viscosity coefficient.
Numerical Modeling of Partial Slip Contact Involving Inhomogeneous Materials
Authors: Wang Zhanjiang , Jin Xiaoqing , Keer Leon M. , Wang Qian
Published: July 2013

When solving the problems involving inhomogeneous materials, the influence of the inhomogeneity upon contact behavior should be properly considered. This research proposes a fast and novel method, based on the equivalent inclusion method where inhomogeneity is replaced by an inclusion with properly chosen eigenstrains, to simulate contact partial slip of the interface involving inhomogeneous materials. The total stress and displacement fields represent the superposition of homogeneous solutions and perturbed solutions due to the chosen eigenstrains. In the present numerical simulation, the half space is meshed into a number of cuboids of the same size, where each cuboid is has a uniform eigenstrain. The stress and displacement fields due to eigenstrains are formulated by employing the recent half-space inclusion solutions derived by the authors and solved using a three-dimensional fast Fourier transform algorithm. The partial slip contact between an elastic ball and an elastic half space containing a cuboidal inhomogeneity was investigated.
Chemical Understanding of Friction Polymer Based Tribo-Chemical Films Derived From Nanolubricant
Authors: Zhang Wenyang , Jahan Muhammad P. , Malshe Ajay P.
Published: July 2013

MoS2 multi-component nanolubrication system showed significant friction and wear reduction (more than 30% in friction reduction and 50% in wear reduction) in sliding steel surfaces, especially under mixed and boundary lubrication conditions [1–3]. It is believed that the formation of tribofilms in MoS2 multi-component nanolubrication system under different lubrication regimes is the primary reason for reduced friction and wear. To investigate the in-depth science of the tribo-chemical interface formed by MoS2 multicomponent nanolubrication system, it is necessary to study the chemical states of tribofilm during its evolution (generation ↔ regeneration) process at tribo-interfaces. Tribofilms from various lubrication regimes were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), Raman microscope, and X-ray photoelectron spectroscopy (XPS) techniques to study the morphology, chemical composition, elemental distribution, and chemical bonding of tribo-chemical surface, respectively. Besides the evolution process, the characterization of tribofilms also reveals the possibility of forming new meta-stable phases (chemical compounds) after tribological testing. Patchy tribofilms and progressive tribofilms have been observed from the SEM analysis and the EDX results showed existence of Mo-S-P as the composition of tribo-chemical films. The Raman spectroscopy analysis of tribofilms showed significant difference (such as formation of poly-molybdates) in chemical information of nanolubricants and tribofilms, which is an indication of the formation of friction polymer [4–5]. Additionally, phosphates and oxides, acting as components of surface protecting layer of tribofilms, have been found on surface by XPS technique. Moreover, MoS2 nanoparticles are found to navigate into surface asperities to protect the contacting surfaces. The results (information about the chemical states of the tribofilm) obtained from different characterization techniques can be used to explain the mechanism of friction and wear reduction associated with MoS2 multi-component nanolubrication system that has been reported in the literature.
The Wear Characteristics of Graphene as an Atomically-Thin Protective Coating
Authors: Sandoz-Rosado Emil , Terrell Elon J.
Published: July 2013

Lamellar atomically-thin sheets such as graphene (and its bulk equivalent graphite) and molybdenum disulfide have emerged as excellent solid lubricants at the macro scale and show great promise as protective coatings for nanoscopic applications. In this study, the failure mechanisms of graphene under sliding are examined using atomistic simulations. An atomic tip is slid over a graphene membrane that is adhered to a semi-infinite substrate. The impact of sliding velocity and substrate rigidity on the wear and frictional behavior of graphene is studied. In addition, the interplay of adhesive and abrasive wear on the graphene coating is also examined. The preliminary results indicate that graphene has excellent potential as a nanoscale due to its atomically-thin configuration and high load carrying capacity.
Experimental Study on Analytical Methods for Roughness Deformation Description in EHL Contacts
Authors: Sperka Petr , Krupka Ivan , Hartl Martin
Published: July 2013

The trend of decreasing of lubricant film thickness in tribological systems is one of the important features of current tribology stirred up by the quest for higher efficiency and energy saving. As a result, the influence of the surface micro geometry on the contact performance and machine component life increases steadily. This has led to a systematic effort to develop a theory that describes unifying mechanism governing the amplitude reduction of harmonic patterns in EHL contact known as amplitude attenuation principle [1–2]. This theory provides formulas that can serve as a simple tool to predict the deformed geometry inside the contact for arbitrary micro geometry when used in combination with a Fourier analysis. Therefore, it is possible to give a reasonable explanation of the basic phenomena involved in real rough surface EHL and mixed lubricated contacts.
Influence of Coating Thickness and Substrate Elasticity on the Tribological Performance of PEEK Coatings
Authors: Wang Yuanyuan , Terrell Elon J.
Published: July 2013

When a material is subjected to repeated sliding contact, a surface fatigue and crack nucleation may occur on its surface. This damage weakens the material and can lead to debris formation. In many practical engineering assemblies, a thin PEEK (poly-ether-ether-ketone) coating is applied to reduce the damage, since PEEK exhibits wear resistance, corrosion resistance self-lubricating capacity and is lightweight. However, little is known about the effect of coating thickness on the plastic deformation, residual stresses and energy dissipation of PEEK when placed under sliding load. Moreover, the effect of substrate rigidity on coating stresses and deformation under sliding load are also under-researched. Having such knowledge is of significant importance in order to reduce damage of engineering parts and extend their lifetime.

In this study, the effects of PEEK coating thickness and substrate elasticity were analyzed using a 3D ball-on-flat finite element model as well as experimental analysis using a linear reciprocating tribometer. The experimental tests were performed with samples that incorporated PEEK coatings of various thicknesses on alumina and steel substrates. It was found that under a constant normal load, stresses, strain and energy dissipation were sensitive to both substrate material and coating thickness. It is shown from both simulation and experiment, the optimum combination, within the range the experiments were conducted, for minimizing residual stress and possible fatigue damage was an alumina substrate with 35μm PEEK coating thickness.
Mechanisms of Entrapment and Release of Fluid Droplets From Nano-Scale Surface Features
Authors: Chong William , Teodorescu Mircea , Martini Ashlie , Rahnejat Homer
Published: July 2013

Engineering surfaces are never perfectly flat. They contain micro and nano-scale features on multiple length scales. Predicting the amount of fluid trapped in these minute surface crevices and its controlled release could benefit a variety of practical applications. In a sliding contact, the released fluid could create an ultra-thin film, reducing the direct contact and consequently the boundary friction. Transdermal patches are the least invasive of available subcutaneous drug delivery techniques. The drug is stored in a micro-reservoir and it is released to the skin either through a permeable membrane or through a series of micro needles.

The aim of the current paper represents the first attempt to investigate whether a modeling approach encompassing two complementary simulation techniques in an integrated framework can be used to predict the volume of fluid stored in a nano-scale surface feature. Molecular dynamics (MD) simulation could provide accurate modeling of fluid behavior at nano-scale, and statistical mechanics (SM) could provide a fast prediction.
Heavy Gauge UOE Pipe With Improved Compressive Strength for Offshore Pipeline
Authors: Ishikawa Nobuyuki , Sueyoshi Hitoshi , Nishimura Kimihiro , Yamamoto Osamu , Tanizawa Akihiko , Kiyoto Yasumitsu , Naganuma Daisuke
Published: July 2013

Offshore gas pipeline development has been expanding toward deeper water region that requires pipes to have strong resistance against collapse by external pressure. Collapse pressure is mainly dominated by pipe roundness and compressive strength. In order to improve compressive strength, it is quite important to understand the Bauschinger effect caused by cyclic deformation during pipe forming. Compressive strength is reduced by the Bauschinger effect since compression in the circumferential direction is applied after the pipe expansion. Therefore, prevention of Bauschinger effect is an important issue for improving compressive strength of pipes.

In this paper, the effect of microstructure on the Bauschinger effect was investigated. It was proved that microstructure that consists of a hard second phase shows a large strength reduction in reverse loading, since a mixed microstructure with soft phase and hard phase enhances the Bauschinger effect. In order to obtain homogeneous bainitic microstructure, advanced plate production technology, where heat treatment on-line process (HOP) is applied after accelerated cooling, was developed. The steel produced by HOP process exhibits a fine bainitic microstructure with very low amount of hard second phase such as MA constituent. It was demonstrated that the trial produced pipe with HOP process has a higher compressive strength than conventional pipes.

In addition to the fundamental study on compressive strength, further investigations were conducted to optimize other material properties for offshore linepipe, such as DWTT property, resistance to hydrogen induced cracking and HAZ toughness to comply with DNV requirements. Production tests of Grade X65 linepipe with the 38mm WT and 876mm OD was carried out. Material and mechanical properties of these heavy gauge linepipes were introduced.
A Comparison of Double Block and Bleed Technologies
Authors: Bowie Angus
Published: July 2013

Double Block and Bleed is a term often used in the oil and gas industry to define a level of isolation sufficient to perform maintenance activities. The true definition relates to incumbent valves providing two proven levels of isolation against the outboard pressure to permit breaching of containment in the isolated pipe. This paper assesses how temporary isolation devices can provide equivalent isolation where incumbent valves do not exist at appropriate locations in the system. It reviews the different interpretations of Double Block and Bleed used within the industry and compares how different isolation devices are assessed in relation to the level of isolation they provide.

It will reference several examples from around the world of where temporary isolation devices have been used to replace valves and perform repairs in trunk pipelines without depressurising the whole pipeline. It will also cover examples of isolating live process pipe to perform maintenance activities outside plant shutdown.
Benchmarking Pipeline Risk Assessment Processes
Authors: Tuft Peter , Yoosef-Ghodsi Nader , Bertram John
Published: July 2013

The Australian pipeline design code AS 2885 is largely a risk-based standard, and its safety management study process is admirably suited to the needs of the Australian industry. However it is a unique process that has been developed in Australia and is not used anywhere else in the world. Successfully benchmarking it against other risk assessment methodologies would put the basis of the Australian approach on a footing that would be more difficult to challenge should a major pipeline disaster result in a public enquiry. And if the comparison reveals shortcomings in the AS 2885 process then there will be a sound basis for addressing those shortcomings to improve the process.

The APIA Research and Standards Committee and the Energy Pipelines CRC commissioned studies to compare the AS 2885 SMS process against two alternative methods:

• Reliability-based analysis.

• Quantitative risk assessment based on historical failure rates.

Each study looked at the same four pipeline segments spanning a variety of urban locations in which the consequences of a major pipeline failure would be very serious. Each of the four segments had previously been through the AS 2885 safety management study process and found to present a level of risk that was borderline tolerable. The objective of the studies was to determine whether the alternative risk assessment methods also found a level of risk that was similarly borderline tolerable.

This paper will present the results of the comparison studies, showing that all three methods produce broadly similar outcomes for risks that are close to the borderline between tolerable and intolerable. This is a welcome endorsement of the AS 2885 SMS process and reinforces its validity as a method for assessing and managing pipeline safety.
A Uniform Risk Methodology for Transmission Pipelines Transporting Chemicals
Authors: Spoelstra Margreet B. , Laheij Gerald M. H.
Published: July 2013

In 2011 the Dutch Ministry of Infrastructure and the Environment (I&M) introduced new legislation for pipelines transporting dangerous substances. This legislation applies to pipelines transporting natural gas and to pipelines transporting oil products and deals amongst other things with the consequences of (new) pipelines on spatial planning. Risk methodologies have been revised in order to reflect new understandings in risk scenarios, failure frequencies and consequences. In the Netherlands operators and responsible authorities are now required to use these methodologies in risk calculations.

A risk methodology for pipelines transporting chemicals (substances other than natural gas or oil products) has currently been developed. These pipelines have a total length of about 3,000 kilometer and 18 different chemicals such as ethylene, hydrogen, chlorine and carbon dioxide are involved. This paper describes the risk methodology for underground pipelines transporting chemicals, including modeling aspects and failure frequencies. The application of measures to reduce the risk and some case analysis results are presented as well.
Risk Assessment of Modern Pipelines
Authors: Mihell James N. , Rout Cameron
Published: July 2013

Proponents of new pipeline projects are often asked by regulators to provide estimates of risk and reliability for their proposed pipeline. On existing pipelines, the availability of operating and assessment data is generally considered to be essential to the task of performing an accurate and defendable risk or reliability assessment. For proposed or new pipelines, the absence of these data presents a significant challenge to those performing the analysis. The reliance on industry incident data presents problems, since the vast majority of loss-of-containment incidents relate to older pipelines in which the design, routing criteria, material properties, material manufacturing processes, and early operating practices differ significantly from those that are characteristic of modern pipelines. As a consequence, much of the available failure incident data does not accurately reflect the threats or the magnitudes of the threats that are associated with modern pipelines. In order to address this problem, ‘adjustment factors’ are often applied against incident data to try to account for threat differences between the source data and the intended application. The selection of these adjustment factors can often be quite subjective, however, and open to judgment; therefore, they can be difficult to justify.

With the rapidly growing practice of regular in-line inspection (ILI) on transmission pipelines, an extensive repository of ILI data has been accumulated — much of it relating to modern pipelines. Through the judicious selection of source data, ILI data sets can be mined so that an analogue data set can be created that constitutes a reasonable representation of the attributes of reliability of a specific new pipeline of interest. Key reliability properties, such as tool error distribution, feature incidence rate, feature size distribution, and apparent feature growth rate distribution can be derived from such analogue data. By applying these reliability properties in an analysis along with known pipeline design and material properties and their associated distributions, and by taking consideration of planned inspection intervals, a reliability basis can be derived for estimating pipeline risk and reliability. Estimates of risk and reliability that are derived in this manner employ methodologies that are repeatable, defendable, transparent, and free of subjectivity.

This paper outlines an approach for completing risk and reliability estimates on new pipelines, and presents the results of some sample calculations. The reliability estimates illustrated are based on an approach whereby corrosion feature size and growth rates are obtained from analogue ILI datasets, and treated as random variables. In that regard, they constitute the probability of exceeding a limit state that represents an approximation of the condition for failure.
Research on Pricing Formulation Method for Long Distance Natural Gas Pipeline Network Transporting
Authors: Li Xiaoyu , Xu Qiang , Zhao Minghua , Qian Chengwen , Jin Jing , Xi Jingjun
Published: July 2013

With the completion of the second line project of West-East Gas Transmission in 2011, the third line of West-East Gas Transmission will be started soon and the fourth line and the fifth line will be started in recent five years. China will form one of the largest natural gas pipeline network in the world. The gas supply mode will be changed from single gas source and single-pipeline supply to multi-source and multi-pipeline supply through regulation and coordination, which will impact on existing pricing mechanism and operation mode of Chinese natural gas industry violently. Depending on the development trend of natural gas pipeline network, the regionalization management mode of natural gas pipeline will be implemented gradually. Chinese natural gas industry also needs to develop a new-type market-oriented operation mode with clear interfaces between production, transportation, distribution and customers so as to facilitate the optimal allocation of resources.

By the customized scientific research of CNPC (China National Petroleum Corporation), combining with existing pricing mechanism of natural gas pipeline and economic characteristics of long-distance natural gas pipeline transportation in China, the paper studied the pricing mechanism problem of combined transportation of multi-source and mutli-pipeline gas supply in the regionalization management mechanism, presented the idea of pricing formulation method of two kinds of pipeline network transportation based on standard rates of pipeline transportation and service cost rules, formed pricing formulation system of natural gas pipeline transportation, introduced the design idea, structural construction, distribution method and key points of natural gas pipeline transportation in details, and demonstrated the methods by example calculation. The methods presented in the paper can meet the pricing requirements of natural gas pipeline network transportation, remedy the defect in existing price accounting mechanism, solve the problem that the income and expenses among different interest bodies are not balanced, and facilitate the rapid development of natural gas pipeline business.