bluuebunny/crossref_metadata_2025 huggingface dataset:
An Improved Rate of Heat Release Model for Modern High Speed Diesel Engines
Authors: Dowell Peter G. , Akehurst Sam , Burke Richard D.
Published: December 2016

To meet the increasingly stringent emissions standards, Diesel engines need to include more active technologies with their associated control systems. Hardware-in-the-Loop (HiL) approaches are becoming popular when the engine system is represented as a real-time capable model to allow development of the controller hardware and software without the need for the real engine system. This paper focusses on the engine model required in such approaches. A number of semi-physical, zero-dimensional combustion modelling techniques are enhanced and combined into a complete model, these include — ignition delay, pre-mixed and diffusion combustion and wall impingement. In addition, a fuel injection model was used to provide fuel injection rate from solenoid energizing signals.

The model was parameterized using a small set of experimental data from an engine dynamometer test facility and validated against a complete data set covering the full engine speed and torque range. The model was shown to characterize Rate of Heat Release (RoHR) well over the engine speed and load range. Critically the wall impingement model improved R2 value for maximum RoHR from 0.89 to 0.96. This reflected in the model’s ability to match both pilot and main combustion phasing, and peak heat release rates derived from measured data. The model predicted indicated mean effective pressure and maximum pressure with R2 values of 0.99 across the engine map. The worst prediction was for the angle of maximum pressure which had an R2 of 0.74. The results demonstrate the predictive ability of the model, with only a small set of empirical data for training — this is a key advantage over conventional methods. The fuel injection model yielded good results for predicted injection quantity (R2 = 0.99), and enables the use of the RoHR model without the need for measured rate of injection.
Investigation of Cycle-to-Cycle Variation of In-Cylinder Engine Swirl Flow Fields Using Quadruple Proper Orthogonal Decomposition
Authors: Ge Penghui , Hung David L. S.
Published: December 2016

It has been observed that the swirl characteristics of in-cylinder air flow in a spark ignition direct-injection (SIDI) affect the fuel spray dispersion and flame propagation speed, impacting the fuel mixture formation and combustion process under higher conditions. In addition, the cycle-to-cycle variations of swirl flow often degrade the fuel spray mixing and combustion quality in the cylinder. In this study, the 2D flow structure along a swirl plane at 30 mm below the injector tip was recorded using high-speed particle image velocimetry in a four-valve optical SIDI engine under high swirl condition. Quadruple proper orthogonal decomposition (POD) was used to investigate the cycle-to-cycle variations of 200 consecutive cycles during the intake and compression strokes. The flow fields were analyzed by dividing the swirl plane into four zones along the measured swirl plane according to the positions of intake and exhaust valves in the cylinder head. Experimental results revealed that the coefficient of variation (COV) of the time coefficients of the quadruple POD mode coefficients could be used to estimate the cycle-to-cycle variations at a specific crank angle. The dominant structure was represented by the first POD mode in which its kinetic energy could be correlated with the motions of the intake valve. Moreover, the higher order flow variations were closely related to the flow stability at different zones. In summary, quadruple POD provides another meaningful way to understand the intake swirl impact on the cycle-to-cycle variations of the in-cylinder flow characteristics in SIDI engine.
Performance, Efficiency and Emissions Evaluation of Gasoline Port-Fuel Injection, Natural Gas Direct Injection and Blended Operation
Authors: Pamminger Michael , Wallner Thomas , Sevik James , Scarcelli Riccardo , Hall Carrie , Wooldridge Steven , Boyer Brad
Published: December 2016

The need to further reduce fuel consumption and decrease the output of emissions — in order to be within future emissions legislation — is still an ongoing effort for the development of internal combustion engines. Natural gas is a fossil fuel which is comprised mostly of methane and makes it very attractive for use in internal combustion engines because of its higher knock resistance and higher molar hydrogen-to-carbon ratio compared to gasoline. The current paper compares the combustion and emissions behavior of the test engine being operated on either a representative U.S. market gasoline or natural gas. Moreover, specific in-cylinder blend ratios with gasoline and natural gas were also investigated at part-load and wide open throttle conditions. The dilution tolerance for part-load operation was investigated by adding cooled exhaust gas recirculation. The engine used for these investigations was a single cylinder research engine for light duty application which is equipped with two separate fuel systems. Gasoline was injected into the intake port; natural gas was injected directly into the cylinder to overcome the power density loss usually connected with port fuel injection of natural gas. Injecting natural gas directly into the cylinder reduced both ignition delay and combustion duration of the combustion process compared to the injection of gasoline into the intake port. Injecting natural gas and gasoline simultaneously resulted in a higher dilution tolerance compared to operation on one of the fuels alone. Significantly higher net indicated mean effective pressure and indicated thermal efficiency were achieved when natural gas was directly injected after intake valve closing at wide open throttle, compared to an injection while the intake valves were still open. In general it was shown that the blend ratio and the start of injection need to be varied depending on load and dilution level in order to operate the engine with the highest efficiency or highest load.
Numerical Simulation of Dual-Fuel Compression-Ignition Engine in Part-Load Operating Condition With Double Injection
Authors: Jamali Arash , Nalim M. Razi
Published: December 2016

Natural gas substitution for diesel can result in significant reductions in pollutant emissions. In addition, with a high ignition temperature and relatively low reactivity, natural gas can enable promising approaches to combustion engine design. In particular, the combination of low-reactivity natural gas and high-reactivity diesel may allow for optimal operation as a reactivity-controlled compression ignition (RCCI) engine, which has potential for high efficiency and low emissions. In this computational study, a lean mixture of natural gas is ignited by direct injection of diesel fuel in part-load operating condition in a model of the heavy-duty CAT3401 diesel engine. A multi-dimensional simulation was performed using a finite-volume computational code for fuel spray and combustion processes in the Reynolds-averaged Navier-Stokes (RANS) framework. Adaptive mesh refinement (AMR) and multi-zone reaction modeling enables simulation in a reasonable time. The latter approach avoids expensive kinetic calculations in every computational cell, with considerable speedup. The model produces encouraging agreement between the simulation and experimental data. For reasonable accuracy and computation cost, a minimum cell size of 0.2 millimeters is suggested for the natural gas-diesel (NGD) dual-fuel engine. The results reveal that in part-load operating condition, much of the CH4, which is used as surrogate fuel for natural gas, cannot burn. The main goal of this research work is to assess the possibility to improve the performance of Caterpillar-3401 engine in NGD dual-fuel operation by in-cylinder modification strategies. The results reveal that among different strategies, double injection of diesel fuel with an early main injection can reduce the unburned hydrocarbon (UHC) emission significantly.
Scavenged Pre-Chamber on a Gas Engine for Light Duty Truck
Authors: Vávra Jiří , Syrovátka Zbyněk , Takáts Michal , Barrientos Eduardo
Published: December 2016

This work presents an experimental investigation of advanced combustion of extremely lean natural gas / air mixture in a gas fueled automotive engine with a scavenged pre-chamber. The pre-chamber, which was designed and manufactured in-house, is scavenged with natural gas and is installed into a modified cylinder head of a gas fueled engine for a light duty truck.

For initial pre-chamber ignition tests and optimizations, the engine is modified into a single cylinder one. The pre-chamber is equipped with a spark plug, fuel supply and a miniature pressure transducer. This arrangement allows a simultaneous crank angle resolved pressure measurement in the pre-chamber and in the main combustion chamber and provides important validation data for computational fluid dynamics (CFD) simulations.

The results of the tests and initial optimizations show that the pre-chamber engine is able to operate within a significantly wider range of mixture composition than the conventional spark ignition engine.

Full load operation of the pre-chamber engine is feasible with stoichiometric mixture (compatible with a three-way catalyst), without excessive thermal loading of components. At low load operation, the results show low NOx emissions with a high potential to fulfil current and future NOx limits without lean NOx exhaust gas after-treatment. The scavenged pre-chamber helps to increase the combustion rate mainly in the initial phase of combustion. However, significant unburned hydrocarbons emissions due to incomplete combustion need further optimizations. Thermal efficiency of lean operation of the engine with the pre-chamber compared to the conventional spark ignition system operated in stoichiometric conditions shows approximately 13% improvement.
A Study on the Mechanism of Pressure Generating Under the Oil Control Ring of a Piston in an Internal Combustion Engine
Authors: Ito Akemi , Kikuhara Koji , Nishijima Shunsuke , Hasegawa Hiroki , Akamatsu Hirotaka
Published: December 2016

Engine oil consumption must be reduced for lowering particulate matter, deterioration of engine after treatment devices and users running cost. A lot of factors affect engine oil consumption, and it is usually estimated experimentally on very latter stage of engine development. Therefore calculation method for oil consumption which can be used for engine design is required. Supply oil volume is necessary to calculate oil consumption. In this study, oil pressure distribution under the oil ring which affects supply oil volume was measured, and a hypothesis for generating oil pressure was discussed. Oil pressure was deviated from crank case pressure and a pressure rise under the oil ring was found in the latter half of the piston down strokes. The maximum pressure was measured at the center of the piston skirt under the oil ring. It was showed that oil pressure rise could be simulated considering distribution of oil film thickness on the cylinder wall.
TWC-SCR Aftertreatment System Evaluation for a Lean Burn Gasoline Engine Operating in HCCI, SACI, and SI Combustion Modes
Authors: Easter Jordan , Bohac Stanislav V.
Published: December 2016

Low temperature and dilute Homogenous Charge Compression Ignition (HCCI) and Spark Assisted Compression Ignition (SACI) can improve fuel economy and reduce engine-out NOx emissions to very low values, often less than 30 ppm. However, these combustion modes are unable to achieve stringent future regulations such as SULEV 30 without the use of lean aftertreatment. Though active selective catalytic reduction (SCR) with urea injection and lean NOx traps (LNT) have been investigated as options for lean gasoline engines, a passive TWC-SCR system is investigated in this work because it avoids the urea storage and dosing hardware of a urea SCR system, and the high precious metal cost of an LNT. The TWC-SCR concept uses periodic rich operation to produce NH3 over a TWC to be stored on an SCR catalyst for subsequent NOx conversion during lean operation.

In this work a laboratory study was performed with a modified 2.0 L gasoline engine that was cycled between lean HCCI and rich SACI operation, or between lean and rich SI (spark ignited) combustion, to evaluate NOx conversion and reduced fuel consumption. Different lambda values during rich operation and different times held in rich operation were investigated. Results are compared to a baseline case in which the engine is always operated at stoichiometric conditions. SCR system simulations are also presented that compare system performance for different levels of stored NH3.

With the configuration used in this study, lean/rich HCCI/SACI operation showed a maximum NOx conversion efficiency of 10%, while lean/rich SI operation showed a maximum NOx conversion efficiency of 60%. However, if the low conversion efficiency of lean/rich HCCI/SACI operation could be improved through higher brick temperatures or additional SCR bricks, simulation results indicate TWC-SCR aftertreatment has the potential to provide near-zero SCR-out NOx concentration and increased system fuel efficiency. In these simulations, fuel efficiency improvement relative to stoichiometric SI were 7 to15% for lean/rich HCCI/SACI with zero tailpipe NOx and −1 to 5% for lean/rich SI with zero tailpipe NOx emissions. Although previous work indicated increased time for NH3 to start forming over the TWC during rich operation, less NH3 production over the TWC per fuel amount, and increased NH3 slip over the SCR catalyst for advanced combustion systems, if NOx conversion efficiency could be enhanced, improvements in fuel economy and low engine-out NOx from advanced combustion modes would more than make up for these disadvantages.
Evaluation of Polyvinyl Chloride Bags During Plutonium Storage
Authors: Hensel Steve J. , Kyriazidis Lucas L. , Skidmore Eric J. , Askew Neal M.
Published: December 2016

This evaluation considers the storage of plutonium materials in 9975 shipping packages at the Savannah River Site (SRS) K-Area Complex (KAC). The materials are packaged in a can – bag – can configuration where the outer can is a screw lid filtered can and the inner can is a slip lid filtered can (filters for both cans are located in the can lid). The inner slip lid can is secured using polyvinyl chloride tape. A filtered plasticized polyvinyl chloride (pPVC) bag is used to bag out the slip lid can from the glove box where the plutonium oxide is packaged. The filtered bag and slip lid can are placed into the outer screw lid can outside the glove box. This can – bag – can configuration is packaged into a 9975 shipping package for storage. An empty “dummy” tin plated carbon steel can (with a hole in the lid) is packaged on top of the screw lid can inside the 9975 Primary Containment Vessel (PCV). The threshold heat generation such that the thermal decomposition of the pPVC bag is precluded is 7 Watts. In addition, the maximum 9975 PCV pressure is computed for normal conditions of storage of the 9975 shipping package in K-Area Complex (KAC).
Modeling the Creep Deformation, Damage, and Rupture of Hastelloy X Using MPC Omega, Theta, and Sin-Hyperbolic Models
Authors: Haque Mohammad Shafinul , Stewart Calvin M.
Published: December 2016

Combined cycle power plants components such as steam pipe work, pressure vessels, boilers, heat exchangers, and gas turbine disks, etc. are exposed to elevated temperature and pressure operation conditions for longer durations. Components may fail within the elastic limit due to a time dependent deformation and damage mechanism called creep. Creep prediction models are used to determine the state of these components and to schedule optimum inspection, maintenance, and replacement intervals. In this study, the deformation, damage, and life of Hastelloy X is characterized using three recently developed models; the Omega, Theta projection, and Sin-hyperbolic models. An analysis is performed to compare the models in terms of accuracy, assumptions, constant identification techniques, flexibility in use, and limitations. The influence that final creep strain has on Theta and Omega model is discussed. Sixteen tests were performed at four different configurations of stress (2.1–36.5 ksi) and temperature (1200–1800°F). In the experimental data, Hastelloy X does not exhibit the primary stage. In this study, the secondary and tertiary creep stages are modeled. Creep deformation and rupture life data is used to optimize the constants for the three models. Predictions using these models are compared with experimental data. It is found that the novel Sin-hyperbolic model better fits the experimental data, and is easier to apply. The Omega model predicts longer life than the Sinh and the Theta Projection model. The rupture life prediction of the Theta projection model is the worst due to dependence on the critical creep strain rate. It is observed that the Hastelloy X final creep strain depends on stress and temperature; this leads to a less accurate critical creep strain rate prediction resulting in inaccurate rupture life predictions for the Theta projection model. The analytical damage of the Omega model exhibits a linear evolution with time while the Sinh model show a more realistic elliptical creep damage evolution with time. A process to determine the constants of all the models is clearly described. The dependence of the trajectory of the creep curves with respect to the constants is discussed in detail. An analytical derivation of each model is provided. Predictions of these three models show that the Sinh model produces a better creep deformation curve by normalizing the experimental creep strain rate data. It is found that overall the Sinh model offers more flexibility, prediction accuracy, and is easier to apply.
Analytical Expression of Elastic Follow-Up Factors in Fully-Plastic Situation for Creep-Fatigue Damage Assessment of High Temperature Components
Authors: Fujioka Terutaka
Published: December 2016

To assess creep-fatigue life consumption in a high temperature component, strain ranges and stress relaxation histories are needed to be estimated. Inelastic finite element analysis may provide these structural responses. Performing inelastic FEA is, however, usually costly, and thus simple elastic FEA-route methods to estimate these are preferred to in some practical cases. A simple method employed in a design code for the Japanese proto-type fast breeder reactor uses an elastic follow-up factor, and is applicable for components subjected to cyclic secondary stresses. A cantilever model was employed to illustrate theoretical background for this method, and lead to a default value of three for gross elastic follow-up factor for the simplicity and conservatism. Validity of this method, however, has never been confirmed theoretically for general conditions of geometry, loading, and material properties. This paper describes characteristics of the factor based on theoretical investigations of a generally-shaped component subjected to a displacement-controlled loading. Some supporting numerical examples are shown by performing elastic-plastic FEA of a notched cylinder.
A Comparison of Different Design Codes on Fatigue Life Assessment Methods
Authors: Shi Jinhua , Wei Liwu , Faidy Claude , Wasylyk Andrew , Prinja Nawal
Published: December 2016

Different pressure vessel and piping design codes and standards have adopted different fatigue analysis methods. In order to make some contribution to current efforts to harmonize international design codes and standards, a review of fatigue analysis methods for a number of selected nuclear and non-nuclear design codes and standards has been carried out. The selected design codes and standards are ASME Boiler and Pressure Vessel Code Section III Subsection NB and Section VIII Division 2, EN 12952, EN 13445, EN 13480, PD 5500, RCC-M, RCC-MRx, JSME, PNAEG and R5. This paper presents the initial review results.

The results of the study could be used as part of the on-going work of the Codes and Standards Task Force of the World Nuclear Association (WNA) Cooperation in Reactor Design Evaluation and Licensing (CORDEL) Working Group.
Fatigue Threshold Behavior of Stainless Steel in High Temperature Air and Water
Authors: West Elaine , Mohr Heather , Lord Erik
Published: December 2016

The fatigue threshold behavior of stainless steel was assessed in high temperature air and hydrogenated deaerated water environments as a function of stress ratio (R). Fatigue threshold experiments were conducted on four different heats of type 304, 304/304L, and 308L austenitic stainless steels in 250°C air and water environments at stress ratios ranging from 0.1 to 0.8. Air and water experiments showed that operational threshold ΔK (ΔKTH) values ranged from 4.3–6.0 and 3.9–5.3 MPa√m, respectively. ΔKTH values were observed to generally decrease with increasing R which is attributable to crack closure effects. The water ΔKTH measurements were either consistent with or lower than air threshold measurements, and the potential roles of the competing effects of crack closure and hydrogen enhanced planar slip will be discussed in the context of these results. Load history effects in the form of overloads and underloads were shown to significantly impact ΔKTH measurements and these results motivated testing aimed at characterizing material property based intrinsic ΔK threshold (ΔKTH*) values. The ΔKTH* values for stainless steel fatigue crack growth in 250–288°C air and water environments are estimated to be 3 and 2 MPa√m, respectively.
Design Verification Analysis for a Subsea External Tieback Connector Bending Capacity Using API 17TR8 Criteria
Authors: Han Young-Hoon , Bunch Paul
Published: December 2016

The objectives of this paper are to determine the structural and functional bending capacity, for an 18-3/4 inch 10 ksi Dry Completion Unit (DCU) external tieback connector (ETBC), utilizing more advanced analysis design verification procedures of API 17TR8 [1]. This requires the evaluation using a 3D nonlinear elastic-plastic finite element analysis (FEA). Although the design verification procedures of API 17TR8 [1] are written for high pressure high temperature (HPHT) equipment, this paper demonstrates the feasibility of applying it to lower pressure equipment which have more critical requirements for bending capacity vs. pressure capacity. The capacity results are compared between the existing linear elastic criteria of API 17G [2] and the requirements of API 17TR8 [1]. The application of this evaluation demonstrates that the analysis methodology for HPHT equipment can be applied to subsea tieback connectors to obtain maximum bending capacity of the connection.
Impact Analysis of High-Pressure Test Pit Concrete Wall
Authors: Karpanan Kumarswamy , Monson Jereme , Suryanarayanan Arun
Published: December 2016

High-pressure assemblies used in the oil and gas industry are usually pressure tested in hydro and gas pits. Pressure testing is critical in qualifying new components. Test pressures can be as high as 30 ksi or more. The high pressure water or gas used in testing can store large amounts of energy. Any component or part subjected to this pressure will experience high stresses. If any part of the assembly fails during the testing process, the stored energy of the high-pressure test media in the system can cause the failed part to be ejected at a very high velocity, leading to potential safety issues. Therefore it is crucial to design the reinforced concrete wall of the test pit appropriately to contain the ejected part and prevent or minimize associated damage.

This report presents methods to determine the concrete perforation thickness and subsequently, calculate the required test pit wall thickness for stopping a projectile. Since the projectile velocity is a function of test pressure, volume of the pressurized vessel (tested equipment), projectile plug geometry, vessel material, and the pressurized fluid, analyses will include all of these parameters. The test assembly and the ejected part will be simplified into a vessel and a plug in order to make quantitative assessments of the concrete pit wall penetration. Results from the analyses are expected to provide guidance on the concrete wall thickness for designing a safe, high-pressure test pit. The projectile velocities predicted analytically will be compared with those predicted by CFD analyses. Additionally, the analytical prediction of concrete perforation will be verified by running an explicit FE analysis of the concrete impact using LS-DYNA.
The Influence of AGR Gas Carburisation on the Creep and Fracture Properties of Type 316H Stainless Steel
Authors: Nasser Mustafa , Davies Catrin M. , Nikbin Kamran
Published: December 2016

Defects in the UK’s AGR nuclear reactors have been historically found in superheater regions of the boilers. These components are fabricated from type 316H austenitic stainless steel and operate in carbon dioxide gas coolant environments under creep conditions, at temperatures up to 550°C. As a result, some components maybe carburised throughout their life resulting in the formation of a hardened outer surface layer. This layer results from interstitial carbon diffusion and is thought to impact on the creep, creep-fatigue and fracture properties of 316H. Carburisation is currently unaccounted for within high temperature structural integrity assessment procedures. It is essential that carburisation and resulting damage mechanisms are well understood in order to accurately predict the failure of components.

This paper aims to investigate the effect of AGR gas carburisation on the creep and fracture properties of type 316H stainless steel. Specimens have been preconditioned within a simulated AGR gas environment. The presence of carburisation has been confirmed through metallographic examination, hardness testing and surface analysis techniques. A series of constant load high-temperature creep tests have been conducted on preconditioned specimens. Compared to as-received material, carburised specimens displayed a significant reduction in creep rupture time with cracking of the outer carburised layer initiating creep crack growth. This phenomenon is seen to occur at very low strains and has been confirmed through interrupted creep testing. The substantial reduction in creep rupture time is postulated to result from embrittlement of the carburised material owing to strong precipitation of carbides along grain boundaries. It is concluded that carburisation can lead to a severe reduction in creep rupture life in test conditions; the possible implications of this with regards to plant conditions are discussed.
An Investigation of Adaptive Rubber Bearings
Authors: Tsai C. S. , Su Hui-Chen , Huang Wen-Chun
Published: December 2016

Proposed in this study are several innovative seismic isolators composed of rubber materials that are called adaptive rubber bearings based on their adaptive characteristics. The materials used in the proposed isolators are free of lead commonly found in lead rubber bearings. The lead material results in a heavy environmental burden as well as lower yield strength and damping due to rising temperature during earthquakes, and thus causes larger displacements than we would expect. The designed mechanisms in the proposed isolators enable these devices to be manufactured relatively easily. They also provide extremely high damping to bearings, which is strongly desired by engineers in practice. The proposed rubber bearings are completely passive devices yet possess adaptive stiffness and adaptive high damping. The change in stiffness and damping is predictable and can be calculated at specifiable and controllable displacement amplitudes. The major benefit of the adaptive characteristics of seismic isolators is that a given system can be optimized separately for multiple performance objects at multiple levels of earthquakes. In this study, mathematical formulations are derived to explain the mechanisms of the proposed devices. Experimental results of high velocity cyclical loadings are also provided to verify the advanced concepts of the proposed devices.
Leakage of 316Ti SS Pipeline Transporting 98% H2SO4 due to CUI and Changed Microstructure From Welding
Authors: Jian-qun Tang , Gong Jianming
Published: December 2016

With the properties of good mechanical strength, excellent resistance to uniform corrosion and superior weldability, austenitic stainless steels are widely used in petrochemical industries. Among them, 316Ti austenitic stainless steel is a titanium stabilized version of 316 molybdenum-bearing steel. The addition of titanium can greatly increase the resistance to sensitization and significantly reduces the susceptibility to the formation of chromium carbides. So, 316Ti stainless steel is more resistant to general corrosion and pitting/crevice corrosion as well as intergranular corrosion, it is even more resistant to sensitization as compared to low carbon 316L stainless steel. Based on these advantages, 316Ti stainless steel pipelines are chosen to transport 98% H2SO4 in one factory. The pipelines for transporting concentrated H2SO4 were manufactured by welding segments of 316Ti stainless steel pipes. The external surface of the pipelines was insulated to maintain heat and prevent crystallization as well as for safety and health reasons. After being in use for about two years, leakage occurred on one pipe and concentrated H2SO4 was seeping from the pits on the pipeline. The investigation about leakage was carried out. The results show that leakage was caused by corrosion under insulation (CUI) and the pits formed by CUI are just located on the welding arc contact zone (WACZ) of the base metal caused by the welder’s faulty operation during welding the joints. The external surface metal of the pipe contacted by the welding arc was partially re-melted by arc heat, which solidified in air and finally formed into another new microstructure that is completely different from that of 316Ti stainless steel. The microstructure in re-melting and solidification zone of the pipe is similar to that of cast metal and didn’t experience any heat treatments. This has less resistance than austenite in 316Ti stainless steel. As a result of the continuous rainy days in the summer, the insulation on the external surface of the pipe was dampened or wetted, which made moisture penetrate and accumulate between the insulation and the pipe, finally resulting in CUI. At the same time, the accumulation and concentration of chloride from the insulation as well as the relatively high temperature in summer, greatly increased the corrosion rate of metal under insulation. Therefore, the presence of the less resistant microstructure in the re-melting and solidification zone, together with the dampened or the wetted insulation, as well as existence of chloride, made the external surface metal of the pipe under the insulation suffer from corrosion, finally resulting in the occurrence of the leakage. The concentrated H2SO4 which was seeping from the pipeline was easily diluted by the moisture or water trapped in insulation. The diluted H2SO4 is a strong corrosive medium, which in turn made the metal around the pits heavily corroded.
3D Solution of the Flow Field in a Boiling Water Reactor Annulus due to a Recirculation Outlet Line Break Using Heat Transfer Analogy
Authors: Ananth Raju , Fong Minji
Published: December 2016

During a Loss of Coolant Accident (LOCA) in a Boiling Water Reactor (BWR), subcooled water flows past jet pump assemblies located in the annular region between the Reactor Pressure Vessel (RPV) and the shroud as it moves toward the break location and is subsequently discharged from the RPV. Flow loads caused by such an event are required design basis loads that must be considered for BWR internal components.

In previous works [1, 2], the three dimensional (3-D) flow field problem was simplified to be a 2-D problem by assuming the radial velocity variations to be negligible. The 2-D problem was solved using complex function techniques by assuming a potential flow. Further, the velocity field had to be suitably scaled up to account for the presence of components such as the jet pumps in the annulus. In order to solve the problem in the realistic environment of a populated annulus, this paper illustrates a methodology where Finite Element Analysis (FEA) is used to perform a 3-D potential fluid flow calculation utilizing the analogy that exists between steady state heat transfer and potential flow problems.

For an ideal fluid, the potential flow and irrotational flow assumptions will result in the Laplace equation as the governing equation for the velocity field. This is the same equation that governs the steady state heat transfer in any domain of interest where the temperature field is determined by solving the Laplace equation and applying the appropriate boundary conditions.

Once the analogy between steady state heat transfer problems and potential flow problems governed by Laplace equation can be established, any commercially available finite-element code may be employed to solve such fluid flow problems involving complicated regions of interest by employing elements meant to solve heat transfer problems. For illustration purposes, a LOCA flow problem will be solved using Finite Element Model (FEM) thermal elements and compared against 2-D flow field results.
Risk Management of Peening Application to Nuclear Power Plant Components
Authors: Kobayashi Hiroyuki , Nakama Shohei , Fujino Takushi
Published: December 2016

The improvement of residual stress in component surface by shot peening was applied mainly to the core shroud for the purpose of preventing stress corrosion cracking (SCC) in BWR Nuclear Power Plants (NPP’s) in the late 1990’s. Subsequently, advanced peening techniques using pressure shock wave impact, such as Water Jet Peening (WJP) and Laser Peening (LP), were developed. Subsequently, PWR NPP’s also adopted these techniques to prevent Primary Water Stress Corrosion Cracking (PWSCC) in Japan.

These peening techniques were implemented with performance demonstration tests conducted in advance by JAPEIC (Japan Power Engineering and Inspection Corporation). Operators also planned on-site applications, including risk management. This risk refers to the risk that components integrity or outage schedule may be affected by peening. In fact, Tsuruga-2 faced a difficult situation, despite the preparation for the risk that cracks might be detected during pre-peening inspection. It was beyond anything that could have been expected.

This paper presents the experiences of peening technique applications at Tokai-2 (2 loop, 1,100 MWe BWR) and Tsuruga-2 (4 loop, 1,160 MWe PWR), analyzing common risk factors present in general application cases based on specific experiences. As a result, high-risk possibilities are indicated depending on risk management, and the necessity is shown for controls that take into consideration materials, design, operation time and other factors. Additionally, the relationship between the risk management and Codes & Standards is also referenced.
Probabilistic PTS Analysis
Authors: Bhimanadam V. R. , Blom F. J.
Published: December 2016

This paper describes the effect of variability of fracture toughness of nuclear pressure vessels during a PTS event. The model used in this paper is based on the NESC-1 experiment. To determine the behavior of the surface breaking defect NRG performed three dimensional finite element calculations and subsequently extended these calculations to the probabilistic calculations. Three-dimensional finite-element model of the cladded cylinder was generated using ANSYS with semi-elliptical surface crack having a crack depth of 75 mm and a crack length of 205 mm. The cylinder specimen was subjected to thermal-shock and centrifugal loading conditions and analyzed with a themo-elastic-plastic material model and subsequently determined the fracture mechanics parameters (J and K) along the elliptical crack front as a function of time and temperature. The determined stress intensity factor K has been compared with the available cleavage fracture toughness (KJC) data with 50% fracture probability which has been obtained from the Master Curve according to BS7910. The comparison has been performed for the locations in the base metal as well as the locations in the heat affected zone.

Deterministic analysis has been extended to probabilistic analysis to calculate the failure probability for the crack initiation at the locations in the base metal as well as the locations in the heat affected zone along the crack front by considering probabilistic distributions from Master Curve and FAVOR. Master Curve analysis through the ASME code case N-629 has been applied to the material. Results obtained from these two methods have been compared and also the results are used to compare the inherent safety factors in the deterministic analysis using RTNDT and Master Curve.
Development of Probabilistic Fracture Mechanics Analysis Codes for Reactor Pressure Vessels Considering Recent Embrittlement Model and Calculation Method of SIF: Progress of the Work
Authors: Kim Jongmin , Lee Bongsang , Kim Taehyun , Chang Yoonsuk
Published: December 2016

It is widely recognized that the state of knowledge and data for the probabilistic calculations which had been proposed in the early 1980s made a conservative treatment of several key factors and models. Recently, applications of some new radiation embrittlement model, material database, calculation method of stress intensity factors and others which can improve fracture mechanics assessment of reactor pressure vessel (RPV) are introduced. This improvement on the accuracy and reliability of the probabilistic fracture mechanics (PFM) analysis necessitated changes in PFM analysis procedures and calculations. Modification and application of newly developed models and calculation methods are the main target of developing a probabilistic fracture mechanics analysis code based on the structure of existing R-PIE and VISA computer code to reflect the latest technical basis. Failure probabilities of reactor pressure vessel under pressurized thermal shock (PTS) conditions were calculated through finite difference method (FDM) and Monte Carlo simulation techniques with user friendly graphic interface. Moreover, various radiation embrittlement models and calculation methods of stress intensity factor at crack tip based on AFCEN code are applied and verified in the present work.
R&D of Structural Alloy for Molten Salt Reactor in China
Authors: Li Zhijun , Leng Bin , Yuan GuangZhou , Wu Guanyuan
Published: December 2016

Structural materials (Alloy N) of molten salt reactor are used to fabricate the reactor vessel, loops, heat exchangers, control rod sleeves, which should have long-term stable properties and enough strength and ductility in multiple extreme environments e.g. high temperature, high pressure, corrosion and neutron irradiation.

The choice and evaluation of materials for different reactor components depend on the specific working conditions of the components. For thorium molten salts reactor-solid fueled one (TMSR-SF1), the reactor vessel is filled with argon gas and the outside parts are exposed to the air. It contains a primary loop of FLiBe coolant and a secondary loop of FLiNaK coolant. The outlet temperature is 700 °C, and the core operating pressure is less than 0.5MPa.The calculated total neutron fluence after 20 years’ service is 2.01×1017n/cm2 for the reactor vessel. Based on these working conditions, the different properties of structural materials are considered and evaluated.

The most important issues of TMSR-SF1 materials include the supply of materials (their preparation, processing, welding, for example) and their qualification in ASME Code. We review alloy N for TMSR-SF1 including alloy physical properties, creep and rupture life time, thermal stability, corrosion, irradiation performance, as well as reliability evaluation of the weldments and so on.
Applicability of a Deterministic Approach to Predict the Minimum Fracture Toughness in the DBTT Region From Tensile Test Results: Example for 0.5T SE(B) and 1TCT Specimens
Authors: Meshii Toshiyuki , Fujita Yusuke , Yamaguchi Teruhiro
Published: December 2016

Fracture toughness Jc of the material in ductile to brittle transition temperature region is known to have two specimen size effects; the planar size effect and the test specimen thickness effect. It was presented that these size effects can be solved by applying modified Richie-Knott-Rice failure criterion in previous research. As a next step, in this study, engineering method to predict the minimum Jc for a specimen type and thickness from only tensile test results is proposed. The method focused on our finding the crack-opening stress σ22, measured at a distance from the crack tip equal to four times the crack-tip opening displacement (CTOD) δt, denoted as σ22d, saturated with increasing load, and the J corresponding to the load first reaching this saturated σ22d, denoted as Js, seemed to predict the minimum toughness for a given specimen and material at a specific temperature. The method was validated for 0.5T SE(B) and 1TCT specimen. The material was 0.55% carbon steel JIS 0.55C, which was tested at master curve reference temperature.
Sealing Properties of Joints Between Metal Surfaces Holding Wavy Defects
Authors: Bourniquel Julien , Lasseux Didier , Rit Jean-François
Published: December 2016

Internal sealing of many power plant valves is performed by a metal to metal contact, compatible with severe pressure and temperature conditions of liquid water flow. Contact surfaces are treated by hard alloy coating and lapping in order to enhance sealing properties. However, wavy deformation may occur on the surface because of stress induced during manufacturing and all through the device life, for example as a consequence of thermal shocks.

We aim to quantitatively correlate the leakage which results from wavy defects through experimental measurements and predictions obtained from modeling. In order to leave as few uncontrolled parameters as possible, the sealing joint is isolated from the valve device as a separate system consisting of a flat and rigid plug and an annular seat holding a wavy defect. The leak sealing properties of the metal to metal contact are expressed by a transmissivity value. This physical quantity has a length cube dimension and relates flow rate to pressure difference by a linear relation. It is intrinsic to the interstitial geometry.

The experimental section of this paper relies on two key steps. First, a sample seat, holding a controlled wavy defect, is manufactured. This is achieved by elastically deforming a cylindrical metal part having a tube shape in a lathe’s mandrel. The end-face is machined, lapped and finally the part is released, leaving a wavy defect on the end-face as a consequence of elastic relaxation. Secondly, the transmissivity of the sample seat, pressed against a flat, rigid plug, is determined from leak rate and fluid pressure measurements carried out on specific experimental devices. The procedure is repeated for several clamping loads yielding the transmissivity to apparent contact pressure dependence.

In the modeling section, leakage is calculated following three successive main stages. In the whole procedure, the flow action on the structure is neglected. First a geometrical model of the seat holding the manufactured wavy defect is built using a linear modal decomposition on a basis of vibrational eigen modes allowing to represent any kind of defect. Secondly, the remaining open space -i.e. the opening between the plug and seat surfaces-resulting from the clamping force normal to the mean plane of the contact, is computed. A finite element model is used to solve the contact problem on the non-trivial form of the wavy defect on the whole 3D geometry. Finally, the transmissivity is computed by solving the Reynolds equation for incompressible flow within the percolating opening between the plug and the seat. The final result of the modeling section is a transmissivity function of the apparent contact pressure, characterizing the leakage of the given wavy defect on the seat.

Predictions of the transmissivity reveal to be in good agreement with that obtained experimentally at low clamping forces and overestimate the leakage for larger ones.
Hydrogen Diffusion in FeCrAl Alloys for Light Water Reactors Cladding Applications
Authors: Rebak Raul B. , Kim Young-Jin
Published: December 2016

There is a worldwide effort to develop nuclear fuels that are resistant to accidents such as loss of coolant in the reactor and the storage pools. In the United States, the Department of Energy is teaming with fuel vendors to develop accident tolerant fuels (ATF), which will resist the lack of cooling for longer periods of times than the current zirconium alloy - uranium dioxide system. General Electric (GE) and its partners is proposing to replace zirconium alloys cladding with an Iron-Chromium-Aluminum (FeCrAl) alloy such as APMT, since they are highly resistant to attack by steam up to the melting point of the alloy. FeCrAl alloys do not react with hydrogen to form stable hydrides as zirconium alloys do. Therefore, it is possible that more tritium may be released to the coolant with the use of FeCrAl cladding. This work discusses the formation of an alumina layer on the surface of APMT cladding as an effective barrier for tritium permeation from the fuel to the coolant across the cladding wall.
Comparison of Welder Performance Qualification Rules Between Chinese Regulation and ASME BPVS Sec.IX-2015
Authors: Wang Zhenbang , Yang Yuqing
Published: December 2016

The Chinese Safety Technical Regulation of Special Equipment TSG Z6002-2010 Examination Rules for Welding Operators of Special Equipment is introduced in the paper. Administrative requirements, technical requirements, testing requirements of TSG Z6002-2010 and ASME BPVC Sec.IX-2015 are compared. Requirements and responsibilities of organization who conducts the welder or welding operator performance qualification test are discussed. The rules for expiration and renewal of welder or welding operator performance qualification are also discussed. The essential variables for the welder or welding operator performance qualification and the ranges qualified under TSG Z6002-2010 and ASME BPVC Sec.IX are compared. The requirements of type of test and test coupons are compared.
Recommended Configuration of Boiler Drum Water Level Control and Protection System
Authors: Liu Zhelin , Harris John Michael , Liu Jichuan , Yu Shengli , Zhou Mingxin
Published: December 2016

For a high pressure boiler above 1,400 psi (9.7 MPa), the boiler drum level Control and Protection systems serve two distinct, but complementary functions. The Control system needs to control drum level. Protection is done for safety. If the drum level reaches a critical level, the Protection system shuts down the boiler to avoid damage.

One must meet ASME Boiler Code requirements, get the job done correctly, and minimize the number of instruments required. By ASME Boiler Code, one must have at least one Boiler Water Gauge Glass. How many Control instruments are needed? If a single boiler drum water level instrument is used and this instrument suffers a failure, there is a problem. Even if two instruments are used and one fails, one does not know which to trust. Logic dictates that one requires a minimum of three Control instruments. Before discussing Protection, it is good to discuss the characteristics of the instruments available: