bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigations to Study the Comparative Effect of LPG and Gasoline on Performance and Emissions of SI Engine
Authors: Bhale P. V. , Ardhapurkar P. M. , Deshpande N. V.
Published: November 2008

The growing environmental concern and increasing petroleum crisis have led many to look for more cleaner, efficient and cost effective alternative transportation fuels. This paper deals with an experimental investigation on performance and emission characteristics of a S I engine using petrol and LPG. Several tests have been conducted with different loading and speed with gasoline and LPG as fuels and engine performance parameters like brake thermal efficiency, volumetric efficiency, brake specific fuel consumption along with cost analysis were studied. The relative variation of these parameters has been focused in the present paper. The objective of the present study was to test the suitability of LPG as a fuel for low compression ratio S I engines used in light duty vehicles with the minimum possible modifications to be introduced in the engine. The engine running with LPG exhibits significantly lower level of exhaust emissions and cost effectiveness however there is reduction in the thermal efficiency relative to the engine run on gasoline. The significant reduction in the HC and CO emissions (65% and 50% respectively) is observed in the test programme.
Development of Co-Relation Between Vehicle and Stationary Dynamometer-Engine Emissions
Authors: Kalam Md. Abul , Hassan Masjuki Hj. , Hamlaoui Abdesselam , Muhammad Afifi Amalina Bte , Mahlia T. M. Indra , Uddin Md. Aslam
Published: November 2008

This paper presents experimental results carried out to develop co-relation and comparison between vehicle and stationary dynamometer-engine emissions with same engines specifications and brands. The dynamometer-engine has been setup with same load and speed as the vehicle’s engine which is carried on the road. The vehicle’s road load power carried by engine has been calculated and used in this investigation. The stationary engine’s rotational speed has been converted to linear distance to compare specific fuel consumptions (SFC) with real specific fuel consumption (SFC) of the vehicle on the road. The vehicle has been run on road test at 70km/h, 90 km/h and 100 km/h for 100 km each time to measure fuel consumption. Beside this, both the engine and vehicle have been operated in idling condition to measure fuel consumption, CO and HC emissions. Proton vehicle with magma engine (4 cylinders) has been used in this investigation. Both the engine and vehicle have been retrofitted for two fuels namely gasoline fuel and compressed natural gas (CNG). An eddy current dynamometer model Froude Consine (model AG150) is used to test the engine. All the electronic equipment, together with its manipulative controls and indicators such as thermocouples are mounted on ‘CP Cadet10 (UK)’ engine control unit. The engine control unit can control any speed and load applied to the dynamometer-engine. An autocheck model (974/5) and Bacharach model CA300NSX analyzers (standard version, k-type probe) have been used to measure the concentration CO and HC emissions. The results of this investigation will be used to predict the emissions and fuel consumption for road vehicles from stationary dynamometer–engine test.
Regeneration Characteristics of Diesel Particulate Filters Under Transient Exhaust Conditions
Authors: Khan M. Rizwan , Shamim Tariq
Published: November 2008

Particulate emissions from diesel engines, which have hazardous effects on living beings and environment, can be controlled by employing diesel particulate filters (DPFs). The DPF cleans the exhaust by physical trapping of the particulates. A major challenge in developing a DPF with wider applications is its lower durability. The filter durability may be increased by careful design of regeneration (soot oxidation) strategies. The regeneration characteristics of a DPF under steady state conditions are well known. However, during a typical driving cycle, a DPF is subjected to highly transient conditions due to changes in driving modes. These transients result in fluctuations of exhaust flow rate, gas composition and temperature. Such modulating exhaust conditions make the DPF performance and regeneration characteristics differ significantly from that under steady state conditions. The objective of this paper is to investigate the thermal and catalytic regeneration characteristics of DPF under transient exhaust conditions. In this work, a computational investigation is conducted to determine the effect of temperature and exhaust flow modulations on a DPF. The paper contributes to a better fundamental understanding of the filter’s performance under transient driving conditions.
Use of Ethanol Based Oxygenates for Smoke Reduction in C.I. Engines
Authors: Zodpe Dhananjay B. , Deshpande Nishikant V.
Published: November 2008

Diesel Engines have better fuel economy compared to gasoline engines. Society is now aware of various harmful effects of pollution and various researchers are trying to use fuel reformulation method to meet the forthcoming stringent air pollution norms for the diesel engines. This paper presents an experimental investigation on use of three different low price ethanol based oxygenate-diesel blends (oxygenate 4, 8 and 12% in blend) as an oxygen enriched fuel in diesel engine and its effect on brake thermal efficiency, smoke density and emissions of CO, HC, NOx etc is studied. It was observed that there is substantial reduction in the smoke density of exhaust gases and the observed reduction was found proportional to the mass of oxygen present in the blend. Marginal increase in NOx and brake thermal efficiency was observed and there was no significant change in the brake power of the engine.
The Technology and Benefits of Skip-Firing for Large Reciprocating Engines
Authors: Klimstra Jacob , Hattar Christer , Nylund Ingemar , Sillanpa¨a¨ Hannu
Published: November 2008

Reciprocating engines equipped with electromagnetic gas admission valves per cylinder have the advantages of an excellent response to load steps, opportunities for per-cylinder process optimization and the absence of ignitable mixture in the intake receiver. The absence of a throttle valve reduces the pumping losses and simplifies the control strategy. If such engines have to be operated at loads below 30% of their rated power, the fuel supply to part of the cylinders can be cut off to improve the fuel consumption and decrease the hydrocarbon emissions. In this paper, the benefits of this so-called skipfiring methodology have been predicted and the results could be confirmed with tests on a 5.5 MW four-stroke gas engine.
The Characterization and Simulation of Cylinder Liner Surface Finishes
Authors: Jocsak Jeffrey , Tomanik Eduardo , Wong Victor W. , Tian Tian
Published: November 2008

This paper presents an investigation into the characterization and performance prediction of different cylinder liner surfaces commonly used in modern internal combustion engines. The topography of liner specimens was measured, and the friction and wear between a piston ring and each liner surface was measured using a horizontal reciprocating bench tester. The load, speed, and lubricant supply during testing were chosen to ensure that the piston ring and liner operated primarily in a mixed lubrication regime. A computer program was developed to model the performance of the piston ring and liner specimens under the conditions observed during the reciprocating bench test. The Greenwood and Tripp statistical asperity contact model was employed to describe the rough surface contact behavior between the liner specimen and piston ring. Two different methods of characterizing the liner specimen surface roughness and determining the inputs required for the Greenwood and Tripp model from the surface measurements were considered. The friction observed experimentally was compared to the friction predicted by the model, and the ability of the model to predict the absolute friction for a given surface and the relative difference in friction between two different surfaces was investigated.
Assessing the HCCI Characteristics of Natural Gas Using a Free Piston Rapid Compression Expansion Machine
Authors: Goldsborough S. Scott
Published: November 2008

A free piston, rapid compression expansion machine (RCEM) has been used previously to investigate the autoignition, or homogeneous charge compression ignition (HCCI) behavior of a wide range of gaseous and liquid hydrocarbon fuels [1]. Reported data were the efficiency and emissions characteristics of these fuels, where the compression ratios required to achieve autoignition ranged from 16:1 to 50:1. The purpose was to assess the potential of HCCI as a driver for a high efficiency, low emissions futuristic powerplant. In [1] no attempt was made to study the ignition temperatures of the fuel-air mixtures, or the rates and extent of combustion seen under the experimental conditions. These however are important metrics by which kinetic and other combustion models can be validated, and would also provide a means by which the RCEM data can be compared to rapid compression machine (RCM) data. The purpose of this work was to develop a method to calculate these parameters. A new crevice-ring model was employed for the RCEM ringpack. Calculations are presented for both uncombusted and combusted data where the ring model is demonstrated, and the autoignition characteristics of natural gas in this device are quantified.
Numerical and Experimental Investigation of Piston Ring Friction
Authors: Xu H. , Kim M. , Dardal D. , Bryant M. D. , Matthews R. D. , Kiehne T. M.
Published: November 2008

The influence of piston ring lubrication on internal combustion engine performance has received considerable attention for over half-century. Studies show that hydrodynamic lubrication prevails through most of engine cycles, and asperity contact only occurs near the vicinity of dead centers [1][2]. In order to solve the governing equation of lubricant, appropriate velocity and pressure boundary conditions should be incorporated into the lubrication equation - Reynolds equation. While lubricant obeys the no-slip velocity boundary condition, the pressure boundaries at the leading and trail edge of piston ring are related to the chamber and the inter-ring crevice gas pressures. A complete lubrication analysis of piston ring requires an inter-ring gas flow model. In most of existing lubrication models, an isentropic orifice flow model is adopted and the gas flow is assumed to an ideal gas passing through the piston ring end gaps with a constant discharge coefficient [2][3][4][5]. In additional to the flow path of piston ring end gaps, gas also flows through the side-clearance between piston ring and flank groove [6][7][8][9][10]. In this paper, a quasi-Rayleigh narrow-channel gas flow model is proposed by consideration of temperature gradient along radial direction of piston assembly. Piston ring friction force is estimated by a test-rig verified mixed lubrication model [11]. Numerical simulation shows that piston ring friction force and ring axial motion are sensitive to inter-ring gas flow model. The instantaneous indicated mean effective pressure (IMEP) method was adopted here to measure the piston friction during motoring condition. Experimental and numerical results indicate that top ring could contribute about 10% of total power cylinder friction loss.
Micro-Pilot and Spark Ignition Tests on the Same 5 L/Cylinder Displacement Engine
Authors: Ludu Andrei , Baufeld Torsten , Beran Robert , Dexter Stephen , Engelmayer Michael
Published: November 2008

The paper compares engine performance and economics for two combustion systems which were designed, optimized and tested on the same gas engine featuring approximately 5 liter per cylinder displacement and 1500 rpm engine speed. The traditional open-chamber spark-ignited combustion system (SIOC) was in competition with the pre-chamber micro pilot (PCMP) combustion system which involved gas combustion ignited by a very low diesel fuel quantity injected into the prechamber. The paper gives an insight into the two different combustion systems by showing and comparatively analyzing measurement results. The impact of both systems on combustion specifics, turbocharging and ignition systems are discussed. Combustion and thermodynamics benefits of the PCMP system are correlated to the additional development effort and systems required as well as to engine cost. Finally a strategic conclusion is drawn on the combustion system to be chosen in view of future engine performance and emission requirements and with respect to the economics of a gas engine of this size.
Multi-Variable Optimization on Variable Intake Valve Closing Timing System for Engine Overall Performance
Authors: Ye Zhengmao , Li Liguang , Mohamadian Habib P.
Published: November 2008

Variable valve timing (VVT) technology has a remarkable impact on engine power output, fuel economy and emission levels. To achieve a tradeoff among its potential benefits on various aspects, a novel multi-objective optimization method is proposed to complement among engine performances over entire speed-load regions. Intake valve closing (IVC) timing has been widely accepted to be the most effective means of VVT technologies. IVC timing is therefore investigated to accomplish engine overall performance optimization. The bench tests have been conducted using an introduced variable working position belt extender system. A 5-valve, double overhead cam (DOHC) spark ignition engine is selected. The sample testing data of engine power and torque outputs, fuel economy and emission levels are collected from engine bench tests, which are then interpolated with regular engine speed operating ranges via smoothing cubic spline fitting. For multi-objective control problem, principal component analysis can be conducted for the multiple-objective analysis by alternating different engine parameters, such as valve timing, sparking timing, A/F ratio, and so on. On account of the extra expense of engine experiments, a simplified optimization approach is then formulated in order to analyze the potential of IVC technology in terms of engine power output and fuel economy under constraints of emission levels at individual high speed, medium speed and low speed regions, etc. Variable IVC timing control has been shown in this research to improve engine performance throughout speed-load regions. Multi-variable optimization is also demonstrated to be feasible and effective for the optimal performance achievement on speed-load regions.
Matching and Optimisation of Turbochargers for Upgradation of High Horse Power Diesel Electric Locomotives for Indian Railways
Authors: Gautam Anirudh , Agarwal Avinash Kumar
Published: November 2008

As a part of the upgradation program of its fleet of 1940 kW diesel electric locomotives, Indian Railways undertook evaluation, matching and optimization of different turbochargers. The objective was to increase engine output, improve fuel efficiency and limit thermal loading. Trials with different makes of turbochargers using different combinations of diffuser, nozzle rings and compressors were carried out for identifying the optimum configuration for an uprated engine rating of 2310 kW. Test bed evaluations have been carried out on Research Design & Standards Organization (RDSO) test beds for four different designs of turbochargers with different configurations. Two types of surge tests were carried out at each operating point i.e. constant brake mean effective pressure (BMEP) and constant power. In the first case, BMEP was kept constant and engine speed varied and in the second case, power was kept constant and engine speed was varied. The tests consisted of recording the parameters at various combinations of engine speed and power. With different combinations, the highest operating point for a test was governed by peak firing pressures. Some of the parameters, which were monitored, were the compressor air inlet temperature, representative peak firing pressures, turbine inlet temperature, average cylinder head temperature, brake specific fuel consumption (BSFC) and air manifold temperature. This paper discusses the methods adopted in carrying out these evaluations and optimizations and the results obtained thereof along with the decision criteria for making final selections.
Experimental Investigation of Dynamics Effects on Multiple-Injection Common Rail System Performance
Authors: Catania A. E. , Ferrari A. , Manno M. , Spessa E.
Published: November 2008

Fundamental aspects of Common Rail (C.R.) fuel-injection system dynamics were investigated, paying specific attention to the wave propagation induced pressure oscillations and to their relationships with the system control parameters and multiple-injection performance. A detailed experimental analysis of the pressure wave propagation phenomena in a last-generation C.R Multijet equipment of the solenoid type was carried out on a high performance new test bench Moehwald-Bosch MEP2000-CA4000 under real engine simulated conditions. The experimental results include pressure time-histories in the rail and at the injector inlet, as well as flow-rate patterns, for both single and multiple injection events. The measured volume of fuel injected on each injection pulse is also reported. The analysis of the system oscillating behavior was carried out with the support of a simple lumped parameter model. Such a model was shown to be capable of predicting the main frequencies of the hydraulic circuit and their dependence on the geometrical parameters. The good agreement between the outcome of this simple model and the experimental data also substantiated the reliable authors’ interpretation of the cause and effect main relations underlying the complex flow phenomena occurring in the system. A refined computational model was developed and validated in a parallel work ([9]), providing a hydrodynamic analysis tool complementary to experimentation and a means of hydraulic system layout design and optimization. Finally, the mutual fluid-dynamic interactions taking place between consecutive injection events by distinct injectors of the same system are investigated in addition to the difference in dynamics of VCO- and Minisac-nozzle injectors.
HTI’s Novel Deposit Removal Technology: Impulse Deposit Removal System (Abstract)
Authors: Plavnik Gene
Published: November 2008

Heat Technologies, Inc. develops thermal systems based on the most advanced thermal techniques: pulsating heating and combustion, infrared heating, staged combustion, combined combustion, etc.. HTI is involved in the design and manufacturing of a new generation of equipment that deploy these techniques for various commercial and industrial processes. The utilization of aforementioned methods allows us to create compact, cost efficient, low in maintenance, and simple in operation equipment.
Thermo-Gravimetric Analysis (TGA) of Combustion and Gasification of Styrene-Butadiene Copolymer (SBR)
Authors: Castaldi Marco J. , Kwon Eilhann
Published: November 2008

An investigation has been initiated to determine the effects of various atmospheres (6.9% O2/N2, 21% O2/N2 (air), 30% O2/N2, 3% H2/N2 and pure N2) on the efficiency of gasifying or combusting rubber waste to produce synthesis gas or generate steam or power. This paper reports on the findings from a series of TGA experiments at various heating rates on styrene-butadiene copolymer (SBR), which is the main starting component for tire manufacturing. The results indicate that oxygen enhanced atmospheres have a significant effect on increasing combustion efficiency at the tested heating rates. A hydrogen-spiked atmosphere, surprisingly, did not have a significant effect on the gasification rates of SBR at any heating rate; in addition, this atmosphere resulted in a carbon residual that remained in the sample carrier, something that was not observed in the other atmospheres, including pure nitrogen. An unexpected result of the N2-O2 tests was the development of a plateau in the mass-loss versus temperature curves, at temperatures near 500°C.
A Study on the Chemistry of Ash Fractions From MSW Incineration
Authors: Arvelakis S. , Frandsen F. J. , Pomeroy M. , Dam-Johansen K.
Published: November 2008

In this work, a methodology for analysis and characterization of different ash fractions (bottom ash, 2–3rd pass ash, super-heater ash, economizer ash and filter ash) generated from the incineration of MSW in a grate firing plant is presented. The methodology is shown to provide detailed information regarding the chemical composition and the main characteristics of the generated fly and bottom ash that could provide valuable information concerning the handling of ash-related problems, (slagging, fouling, corrosion), and also ash disposal problems. Comparison of the results obtained with results from corrosion studies with MSW ash showed that the sampling point and the sampling procedure significantly affect the results obtained.
A Toxicity Reduction Exercise for Municipal Solid Waste to Energy Fly-Ash Utilising a Separation, Isolation and Treatment Process
Authors: Robertson Daniel , Barratt Rod
Published: November 2008

The current situation for fly ash management and policy regulation in the United Kingdom / European Union, has developed the need for new toxicity reduction exercises. New EU wide policies are changing the type of treatment methods that can be legally used for the residues from waste-to-energy plants. In particular the disposal of flue gas treatment residues, which are classified as a hazardous waste, will not be acceptable to landfill according to the Waste Acceptance Criteria without a pre-treatment by 2007. This has raised a number of interesting engineering questions that need to be addressed. The novel TRE of metal matrix encapsulation has been designed based upon the principles of separation, isolation and treatment to meet these new criteria. Metal matrix encapsulation is a treatment program that employs existing industrial infrastructure to improve its usability and legal compliance.
Reprocurement Considerations for an Existing Municipally Owned Refuse-to-Energy Plant: Pinellas County, Florida
Authors: Smith Warren N.
Published: November 2008

On May 7, 2007, the operating agreement for the Pinellas County mass-burn resource recovery facility will expire. This contract, originally negotiated in the late 1970’s is one of the first in the United States for the design, construction, operation and maintenance of a municipally owned refuse-to-energy facility, and thus is one of the first to expire. In late 2003, Pinellas County began the process to reprocure an operator for its resource recovery facility under the terms of a new long-term agreement. This paper discusses planning processes and reprocurement activities to date, including hiring a reprocurement consulting engineer; formation of the project team (Project Working Group and Project Oversight Committee); development of the project schedule; and, identification of the reprocurement approach (informal meetings with vendors, Request for Qualifications and Request for Proposals). The paper also addresses certain technical and contractual issues associated with contracting a 24-year old refuse-to-energy facility. Technical items considered are a modified approach to ash processing and metals recovery; whether or not to continue the WESPhix® ash treatment process; and the need for various capital improvements. Contractual matters include such items as ownership of spare parts; availability of operating documents and record drawings; transfer of proprietary licenses; and consideration of a transition agreement. Pinellas County’s reprocurement is being designed with the primary goal of developing a process that is fair, open and competitive; and one that provides a level playing field for all interested proposers. The paper draws comparisons between the reprocurement methods and processes considered, with conclusions about why the final reprocurement approach was selected.
Optimizing Steam Turbine Generator Output: Identifying Opportunities
Authors: Marra Dominic
Published: November 2008

In an effort to maximize steam turbine generator output, Montenay Power Corp. (MPC), operator of the Miami Dade County Resources Recovery Facility (DCRRF) undertook a systematic approach to analyze various turbine and steam cycle issues affecting performance. Several low cost methods were used to identify opportunities for increased megawatt generation. Shortfalls within the actual steam path through the turbine blading and internals were quantified with a steam path audit and computerized modeling of the blade path. This audit identified a shortfall of 2.5 megawatts (MW) from the original design and almost a full 1 MW gain through work done during the regular maintenance overhaul. The audit proved to be a valuable tool for making good economic decisions on what seal packing to replace/repair during the TG overhaul. The plant had previously explored re-blading options with the Original Equipment Manufacturer (OEM). This brief study showed turbine internal changes would be capital intensive and carry megawatt improvement claims that were questionable due to various steam cycle issues. Four major operational parameters that affect turbine performance were examined and quantified. Deviations from design steam flow, throttle temperature, back pressure, and throttle pressure accounted for a loss of 24 megawatts (MW) in generation. The three low cost methods used to quantify these losses/opportunities were: 1) Acoustic valve leak detection surveys which identified not only low cost MW gain improvement opportunities but also safety and reliability issues; 2) Helium tracer gas leak detection, used to identify vacuum leaks and confirm the leaks were sealed properly; and 3) A complimentary steam trap survey, which also helped identify lost steam and potential risk to equipment. Preliminary measures were taken to improve steam throttle flow, throttle temperature, back pressure and throttle pressure with a net gain of 7 MW so far. This paper details the methods used and results of the optimization program thus far.
Strain History Effects on Fracture Mechanics Parameters: Application to Reeling
Authors: Ernst Hugo A. , Bravo Richard E. , Daguerre Federico , Izquierdo Alfonso
Published: November 2008

It is now well accepted that welded structures may contain flaws, and that these do not necessarily affect structural integrity or service performance. This is implicitly recognized by most welding fabrication codes that specify weld flaw tolerance, or acceptance, levels based on experience and workmanship practice. However, these levels are somewhat arbitrary and do not provide a quantitative measure of structural integrity, i.e. how “close” a particular structure containing a flaw is to the failure condition. This concept is of special interest in cases in which the pipe is subjected to loads that produce important deformations. In particular the reeling process, used to install offshore lines, produce large cyclic plastic deformation on the pipes. In this work the method to perform a structural reliability analysis (SRA) for a tube subject to reeling is considered in detail. A fracture mechanics based methodology is reviewed and the points that need to be resolved before extending the methods to include reeling are clearly identified. The effect of the strain history on the applied and material fracture mechanics parameters were studied. A theoretical model was developed to describe the crack driving force evolution through strain cycles. A criterion was proposed and corroborated to represent material fracture resistance behavior. An experimental program was carried out. The material analyzed was a X65 - tube 355.4 × 22.2 mm. Monotonic and cyclic fracture mechanic tests were performed on single edge notch in tension (SENT) specimens. The material fracture resistance curve was determined based on the monotonic tests. The cyclic tests were used to determine experimentally the applied fracture mechanic parameters evolution. A very good agreement between predicted and measured CTOD values was obtained for the cases analyzed. A methodology to perform a SRA for tube subjected to reeling is proposed.
Probabilistic Distribution of Indirect Loss for the Risk Analysis of an Offshore Complex
Authors: De Leo´n David , Ortega Cesar
Published: November 2008

The risk analysis of an oil complex require a careful estimation of failure consequences and, as an important component, the indirect loss may play a relevant role, especially for high production facilities. In this work, the interaction between the industrials sectors is considered uncertain by modeling it through random variables. The contribution of the five most important sectors is considered to be normally distributed and the value of its loss, as reported by INEGI (1986), is considered to be the mean value and a coefficient of variation of 0.1 is assumed for each sector loss. By using Monte Carlo techniques, the loss for each of the five sectors is simulated and the total indirect loss is calculated. The production loss is obtained by assuming that time to restore the production rate in the five platforms is 33 months. For each trial, the I/O matrix is obtained, the vector of predisaster products is calculated and the production loss is estimated. Then, the demand and the production level post-disaster are assessed. Finally, the second round and total losses are estimated. With the sample of indirect losses obtained, its probability distribution is estimated. The probabilistic description of the indirect loss includes, among other epistemic uncertainties, the one related to the sector interactions, which are considered as linear in a simplified way.
Reducing Cycle Time to First Oil for Deepwater Field Developments
Authors: Ronalds Beverley F.
Published: November 2008

The cycle time to first production is a primary determinant of the net present value (NPV) of an oil and gas asset. The cost, complexity and risk inherent in deepwater field developments, combined with the relative lack of experience in their execution, often encourages engineers to proceed cautiously in field development. However, a successful fast-track development schedule from discovery to first oil may bring significantly better economic returns. This paper investigates the key parameters influencing cycle time for different facility types, and outlines a wide range of measures that may be adopted to accelerate the time to first production.
Costing for ALARP
Authors: Yasseri Sirous F. , Menhennett Peter
Published: November 2008

A key principle for achieving Tolerable Risk under the UK Health and Safety Executive’s (HSE) approach is the reduction of risks to “As Low As Reasonably Practicable” or ALARP. This principle is founded on the ideal of reducing risks to a point of diminishing returns where additional risk reduction would cost “disproportionally” more than the risk reduction benefit achieved. The HSE approach of estimating the degree of disproportionality between the cost and benefits associated with a potential risk reduction measure is a variation of the Cost Effectiveness approach to ALARP Evaluation. A probabilistic cost-benefit analysis method is outlined for evaluating design options and establishing whether the conditions of ALARP are met. This paper demonstrates the value of probabilistic cost-benefit analysis for the selection of a target safety level and also presents an example of its practical application by way of a case history.
Protection of Pipelines in Shipping Lanes
Authors: Yasseri Sirous F. , Prager Jake
Published: November 2008

Design implies choice from among alternatives — for each alternative solution the designer should assess the total associated risk. The total risk is a composite of both the likelihood of various levels of hazards, and the uncertainty in the response behaviour of the system. The selection or decision process demands a weighing of the costs, risks, and benefits of the alternatives. Using an example, a probabilistic method is outlined for deciding upon the depth of burial of pipelines in shipping lanes. Producing a well-engineered solution to this problem involves the synthesis of many kinds of information. There is a requirement to analyse statistical information on the types of hazards, their frequencies and their possible growth. There is also generally a choice of measures that can be used to protect the pipeline. The choice of protective measure demands a weighing of costs, risks, and benefits and must also include any characteristic which leads to economic or other losses. In this paper each hazard is classified into five levels based on the amount of damage a hazard could impart on the system (this is termed the “demand levels”). These demand levels, when subjected to the system, result in various damage states. The damage states, which are assumed to be the cost of repair or replacement, are also represented in five discrete forms. These five general states of damage are defined in terms of such loss-related factors as level of repair cost, degree of the structural and non-structural damage and the fraction of people injured or killed.
Experimental and Numerical Study of Heave-Induced Lateral Motion (HILM)
Authors: Le Cunff C. , Biolley F. , Damy G.
Published: November 2008

Experiments were carried out at IFREMER Brest to obtain data on the displacement of Steel Catenary Risers (SCR) in the Touch-Down Zone (TDZ) induced by top motion. Measurements were conducted both in the section on the ground (2D motion) and in the section above the touch-down point (3D motion) with an optical tracking system. In the model test, the bottom 1/10 of the riser was represented at a scale of about 1/10. The present paper is focusing on Heave-Induced Lateral Motion (HILM) in the bottom part of the riser. The model riser is based on a full scale case which is first described. Based on Froude’s similitude, the geometrical characteristics of the model are derived. The tracking system and the various instrumentation are then detailed. In the last section, experimental results on one specific case are presented. Numerical calculations with a coupled fluid/structure solver are performed. A comparison for the amplitude and frequencies of HILM is presented. Comments are made on the analogy between the present experiments and some simpler experiments on a one-degree-of-freedom cylinder/spring system sinusoidally excited. Such an analogy should prove itself very fruitful in understanding and quantifying HILM.
Fracture Toughness of X-60/Alloy 625 Welded Joints
Authors: Pope Alexandre M. , Paes Marcelo P. , Teixeira Jose´ Claudio G.
Published: November 2008

Line pipes internally clad by nickel alloy are being considered as steel catenary risers when exploitation of corrosive oils is envisaged and corrosion-fatigue failures are possible. The presence of the Ni alloy as internal clad requires a matching filler metal and, consequently, the girth welds are dissimilar joints. Although these types of welds are widely used in the petroleum industry their fracture toughness are not well documented. Of particular concern is the formation of hard zones in HAZ which are usually associated with low fracture toughness. Joints of API X-60 pipes welded using NiCrMo-3 consumables were CTOD tested at 0°C. Results consistently revealed high fracture toughness values for the weld metal. The HAZ-FL, on the other hand, presented lower values and they were significantly dispersed. Microstructural and fractographic analyses revealed that low values of toughness are associated with local brittle zones (LBZ) mainly IRCGHAZ. The fracture of the specimen that presented the lowest toughness initiated in a partially mixed zone containing hard martensite.
Using Online Distance Learning to Raise Metocean Awareness Amongst Engineering Users
Authors: Graham C. , Graeb-Konneker S. , Shaw C. J.
Published: November 2008

This paper describes why and how the authors have developed an online distance learning package specifically designed with the objective of raising awareness of Metocean amongst Shell’s discipline engineers around the world. Metocean technology is applied across the oil and gas business in design, operational planning and in everyday operations. It has a significant high value impact. Changes in the working and business environment have highlighted a clear need to raise awareness amongst users of Metocean technology — both for the business and for individual competence development. The disciplines identified are project management, structures, floaters, pipelines, subsea, drilling, operations, civil, geomatics and seismic. The paper explores ways to raise this awareness, leading to the choice of a tailored online distance learning course. It describes its design and development, and the incorporation of a number of learning innovations. It also presents the feedback both from line managers and participants on the course, and identifies lessons learnt and areas for improvement. The paper concludes with suggestions for the future and how others can develop bespoke awareness programmes most effectively to add value to their businesses. The significance of this paper is that it focuses on how best to communicate Metocean technology to a broad range of users, and it describes how various online distance learning techniques and innovations were tailored to achieve this. Not only do participants learn about Metocean principles and conditions around the world, but also they select their own business related course assignment. The course design encourages interaction and sharing amongst participants, and includes a variety of case studies and peer reviews. Amongst participants, the course has received high completion, satisfaction and business value scores.
A Frequency Domain Approach for the Random Fatigue Analysis of SCR Considering Bimodal/Bidirectional Characteristic of Campos Basin Sea States
Authors: Silva Dantas Claudio Marcio , de Siqueira Marcos Queija , Fernandes Lima Torres Ana Lu´cia , Ellwanger Gilberto Bruno , Martins Mourelle Marcio
Published: November 2008

Fatigue verification is an important issue in steel risers design, demanding a good representation of the loading conditions that will occur during the riser entire lifetime. PETROBRAS has carried out a series of measurement and acquisition programs over the past decade, including the Campos Basin simultaneous acquisition of waves, current and wind data. The campaigns are called the PROCAP1 in Marlim Field and PROCAP2 in Barracuda Field. Those programs provided simultaneous environmental data (wave, wind and current) containing multimodal / multidirectional sea-states that occur in Campos Basin, with two main peaks dominating the total energy content [20,21]. As fatigue damage calculation depends on the stresses variations during the lifetime of the structure, the set of loads used in the analysis should be complete enough to represent all possible situations. The high number of loading conditions used in riser fatigue verification associated with the random time-domain analysis that demands a high computer time for processing the analysis, impact the design schedule. The frequency domain approach, based on linearization techniques, is an alternative tool for riser analysis and has been studied mainly for structural fatigue verification applications. For this particular application, due to the low intensity of loadings, the geometric nonlinearity is considered by means of a previous nonlinear static analysis, followed by a dynamic frequency domain analysis on the deformed model. The nonlinearity of the drag part of Morison’s formula has to be conveniently treated by linearization techniques. This work presents a comparative study where the results using a frequency domain analysis are compared to the results of a time domain analysis. Both approaches were used in the analysis of a steel lazy-wave riser (SLWR) model connected to a spread-moored FPSO, submitted to fatigue environmental loadings considering the bimodal/bidirectional characteristic of Campos Basin sea-states. The analyses were performed using the PETROBRAS’s in-house computer codes ANFLEX, ALFREQ and POSFAL developed and implemented as part of projects from CENPES/PETROBRAS with “COPPE/UFRJ - The Engineering Post-Graduating Coordination of the Federal University of Rio de Janeiro”.
Steel Lazy Wave Riser Design: API-RP-2RD and DNV-OS-F201 Criteria
Authors: Sudati Sagrilo Luis Volnei , Castro Prates de Lima Edison , Mendes de Sousa Fernando Jorge , Silva Dantas Claudio Marcio , de Siqueira Marcos Queija , Fernandes Lima Torres Ana Lu´cia
Published: November 2008

Several feasibility studies on the use of large diameters steel catenary’s risers for higher water depths have been made by PETROBRAS. It should be mentioned that the structural design criteria, traditionally employed for such risers under extreme and operational conditions, were based on the API-RP-2RD. This design criterion makes use of single safety factor on von Mises stress. Recently, a new design standard DnV-OS-F201 for metallic risers has been proposed. This standard, based on limit state design principles, are presented on the LRFD (Load and Resistance Factor Design) format, allowing different riser design alternatives to take into account the environmental conditions. This paper presents the main feasibility study outlines of an 18” Steel Lazy Wave Riser (SLWR), attached to the border of a spread-moored FPSO at 1800 water depth, for an extreme design condition, considering both the API and DnV criteria. All numerical analysis were accomplished by the PETROBRAS’s in-house computer code ANFLEX.
Prediction of Unsteady Loading on a Circular Cylinder in High Reynolds Number Flows Using Large Eddy Simulation
Authors: Kim Sung-Eun , Mohan L. Srinivasa
Published: November 2008

Large eddy simulations were carried out for the flow around a hydrodynamically smooth, fixed circular cylinder at two Reynolds numbers, one at a subcritical Reynolds number (Re = 1.4 × 105) and the other at a supercritical Reynolds number (Re = 1.0 × 106). The computations were made using a parallelized finite-volume Navier-Stokes solver based on a multidimensional linear reconstruction scheme that allows use of unstructured meshes. Central differencing was used for discretization of both convection and diffusion terms. Time-advancement scheme, based on an implicit, non-iterative fractional-step method, was adopted in conjunction with a three-level, backward second-order temporal discretization. Subgrid-scale turbulent viscosity was modeled by a dynamic Smagorinsky model adapted to arbitrary unstructured meshes with the aid of a test-filter applicable to arbitrary unstructured meshes. The present LES results closely reproduced the flow features observed in experiments at both Reynolds numbers. The time-averaged mean drag coefficient, root-mean-square force coefficients and the frequency content of fluctuating forces (vortex-shedding frequency) are predicted with a commendable accuracy.
Stability Enhancement of Supercavitating Projectiles by Unsteady Air Injection
Authors: Khakpour Yasmin , Yazdani Miad
Published: November 2008

In this work, numerical simulation is used to study the stability enhancement of high speed supercavitating hydrofoils. Although supercavitation is known as one of the most effective methods for drag reduction, producing the cavity, either by ventilation or by cavitator at front of the body, may cause some instabilities on cavity surface and thus on the projectile’s motion. Therefore removing these instabilities comes as an important point of discussion. First of all, we calculate the sources of instabilities and measure respective forces and then present some approaches that significantly reduce these instabilities. One of these methods that could produce more stable supercavities is injecting of the air into the cavity unsteadily which varies through the projectile’s surface. This approach is provided by arrays of slots distributed on the projectile’s surface and unsteady injection is modeled over the surface. Furthermore, the position of ventilation, dramatically affects the stability like those in aerodynamics. In all approaches it is assumed that the supercavity covers the whole of the body, however the forces caused by the wakes, formed behind the body are taken into account. The calculation is performed at three cavitation numbers with respective velocities of 40 m/s, 50 m/s, 60 m/s.
Numerical Wave Tank: Simulation of Extreme Waves for the Investigation of Structural Responses
Authors: Clauss Gu¨nther F. , Schmittner Christian E. , Stu¨ck Robert
Published: November 2008

For the deterministic analysis of extreme structure behavior, the hydrodynamics of the exciting wave field, i. e. pressure and velocity fields, must be known. Whereas responses of structures, e. g. motions, can easily be obtained by model tests, the detailed characteristics of the exciting waves are often difficult to determine by measurements. Therefore, numerical wave tanks (NWT) promise to be a handy tool for providing detailed insight into wave hydrodynamics. In this paper different approaches for numerical wave tanks are introduced and used for the simulation of rogue wave sequences. The numerical wave tanks presented are characterized by the following key features: a) Potential theory with Finite Element discretization (Pot/FE); b) Reynolds-Averaged Navier-Stokes Equations (RANSE) using the Volume of Fluid (VOF) method for describing the free surface. For the NWT using the VOF method three different commercial RANSE codes (CFX, FLUENT, COMET) are applied to calculate wave propagation, whereas simulations based on potential theory are carried out with a wave simulation code developed at Technical University Berlin (WAVETUB). It is shown that the potential theory method allows a fast and accurate simulation of the propagation of nonbreaking waves. In contrast, the RANSE/VOF method allows the calculation of breaking waves but is much more time-consuming, and effects of numerical diffusion can not be neglected. To benefit from the advantages of both solvers, i. e. the calculation speed (Pot/FE-solver WAVETUB) and the capability of simulating breaking waves (RANSE/VOF-solver), the coupling of both simulation methods is introduced. Two different methods of coupling are presented: a) at a given position in the wave tank; b) at a given time step. WAVETUB is used to simulate the propagation of the wave train from the start towards the coupling position (case A) or until wave breaking is encountered (case B). Subsequently, the velocity field and the contour of the free surface is handed over as boundary (case A) or initial values (case B) to the RANSE/VOF-solver and the simulation process is continued. To validate these approaches, different types of model seas for investigating wave/structure interactions are generated in a physical wave tank and compared to the numerical simulations.