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2015-09-29
Technical Paper
2015-01-2889
Saravana Venkatesh R, Sunil Pandey, Sathyanandan Mahadevan
In heavy duty diesel engines, Exhaust Gas Recirculation (EGR) is often preferred choice to contain NOx emissions. Critical to such EGR fitted engines is the design of air intake pipe and intake manifold combination in view of proper EGR gas mixing with intake air. The variation in EGR mass fraction at each intake ports should be as minimal as possible and this variation must be contained within +/- 10% band to have a minimal cylinder to cylinder variation of pollutants. EGR homogeneity for various intake configurations were studied using 3D CFD for a 4 cylinder 3.8 L diesel fuel, common rail system, turbocharged and intercooled heavy duty engine. Flow field was studied in the computational domain from the point before EGR mixing till all the four intake ports. EGR mass fraction variation at each intake port was calculated from this analysis after carrying out an experimental validation of the CFD model.
2015-09-29
Technical Paper
2015-01-2794
Meng-Huang Lu, Figen Lacin, Daniel McAninch, Frank Yang
The diesel exhaust aftertreatment using injection, such as urea – SCR and lean NOx trap systems, could effectively reduce the emission NOx level, and has been commonly used in various industrial applications. The performance of the injector is crucial for successfully utilizing this type of technology, and simulation tools are playing an important role in virtual design, which could evaluate performance and optimize the design. The virtual test methodology using CFD that is able to capture the fluid dynamics of injector internal nozzle flow has been developed to sever for this purpose to quantify the water or urea dosing rate of the test injector, and the computational results were validated with the test data measured in the Tenneco Injector Flow Lab. Later, the capability of the virtual test methodology was extended to quantify the spray angle of the test injector with test fluid of water or urea.
2015-09-29
Technical Paper
2015-01-2893
Ashok Patidar, Ankur Bansal, Umashanker Gupta
Market driven competition in global trade and urgency for controlling the atmospheric air pollution are the twin forces, which have urged Indian automobile industries to catch up with the international emission norms. Improvement in the fuel efficiency of the vehicles is one way to bind to these stringent norms. It is experimentally proven that almost 45% of the engine power is being consumed to overcome the drag resistance and around 40% to overcome the tire rolling resistance of the vehicle. This as evidence provides a huge scope to investigate the influence of aerodynamic drag and rolling resistances on the fuel consumption of a commercial vehicle. The present work is a numerical study on the influence of aerodynamic drag resistance on the fuel consumption of a commercial passenger bus. The commercial CFD code FLUENT is used as a solver to estimate the drag coefficient of the bus. Around 35% improvement in the drag coefficient is achieved by CFD driven changes in the bus design.
2015-09-29
Technical Paper
2015-01-2894
Marius-Dorin Surcel, Mithun Shetty
The performance of several aerodynamic technologies and approaches, such as trailer skirts, trailer boat tails, gap deflectors and gap reduction, was evaluated using track testing, model wind tunnel testing, and CFD simulation, in order to assess the influence of the design, position and combination of various aerodynamic devices. Scale model wind tunnel tests were conducted to have the best direct performance comparisons between several possible configurations. The track test procedure followed the SAE J1321 SAE Fuel Consumption Test Procedure - Type II. The wind tunnel tests were conducted on a 1/8 scale model of a tractor in combination with a 53-foot semi-trailer. The tests consisted of two phases: setting the initial baseline, and component testing of various configurations.
2015-09-15
Technical Paper
2015-01-2566
Reuben Chandrasekharan, Nick Iarocci, Sherry Vafa, Iyad Akel
The Learjet 85 is a business jet with an unpowered manual elevator control and is designed for a maximum dive Mach number of 0.89. During the early design, it was found that the stick force required for a 1.5g pull-up from a dive would exceed the limit set by FAA regulations. A design improvement of the tailplane was initiated, using 2D and 3D Navier-Stokes CFD codes. It was discovered that a small amount of positive camber could reduce the elevator hinge moment for the same tail download at high Mach numbers. This was the result of the stabilizer forebody carrying more of the tail download and the elevator carrying less. Consequently, the elevator hinge-moment during recovery from a high-speed dive was lower than for the original tailplane. Horizontal tails are conventionally designed with zero or negative camber since a positive camber can have adverse effects on tail stall and drag.
2015-09-15
Technical Paper
2015-01-2575
Swen Noelting, Ehab Fares
An overview is presented in this paper of the theory and applications of the Lattice-Boltzmann Method, which has gained a reputation over the past decade as a serious alternative to traditional Reynolds-averaged Navier-Stokes (RANS) based methods for the solution of computational fluid dynamics (CFD) applications in the aerospace and automotive industries. The theoretical background of the method is presented and the validity of the method documented through validations against industry-standard canonical test cases. We then look at current and potential future applications of CFD in the aerospace industry and identify a number of areas where the limitations of RANS tools, in particular with regard to unsteady flows and the handling of complex geometries, prevent a deeper penetration of CFD into the aerospace development process.
2015-09-15
Technical Paper
2015-01-2564
Benjamin Riggins, Davide Locatelli, Joseph Schetz, Rakesh Kapania, Thomas Poquet
Most traditional methods and equations for estimating weights and aerodynamics in the aircraft conceptual design phase are empirical relations developed for conventional tube-and-wing aircraft. In a computation-heavy design process such as MDO simplicity of calculation is paramount, and for conventional configurations these approaches work well enough for conceptual design. But, for non-traditional designs such as strut-braced winged aircraft, empirical data is generally not available and the usual methods can no longer apply. One solution to this is a movement toward generalized physics-based methods that can apply equally well to conventional or non-traditional configurations. In this work, physics-based methods for calculating the aerodynamic drag and wing weight of an aircraft were implemented in a commercial aircraft conceptual design and optimization tool, PACELAB APD, which in its default form utilizes traditional empirical methods for estimating these characteristics.
2015-09-15
Technical Paper
2015-01-2466
Alberto Boretti
The Wankel engine delivers for UAV applications advantages vs. piston engines of simplicity, smoothness, compactness and high power-to-weight ratio. The use of computational fluid dynamic (CFD) may permit to address the major downfalls of these engines, namely the slow and incomplete combustion due to the low temperatures and the rotating combustion chambers. The paper proposes a CFD model of a Wankel engine for UAV and the results of simulations performed at very high speeds of rotation.
2015-09-15
Technical Paper
2015-01-2561
Fernando Stancato, Sandro Conceicao, Ramon Papa, Luis Santos
Nowadays CFD analysis including virtual manikins is vastly applied to evaluate thermal comfort inside different working environments, such as buildings cars and aircrafts. Inside aircraft cabins, added to the numerical challenges due to geometrical complexity, the available subjective responses used to judge occupant local thermal comfort are usually based on buildings and cars experiments. In the present paper however, it is applied an aircraft based subjective responses to evaluate thermal comfort which was specifically developed using regional jet mock-up experiments. The evaluation for the two approaches will be compared providing insight of the main differences.
2015-09-15
Technical Paper
2015-01-2565
Nhan Nguyen, Sonia Lebofsky, Eric Ting, Upender Kaul, Daniel Chaparro, James Urnes
Air vehicles are typically designed to maintain sufficient structural rigidity for safe load-carrying capacity. Modern engineered materials such as composites have begun to appear in new airframe designs that can provide less structural rigidity while maintaining the same load-carrying capacity. An example of light-weight airframe design is the Boeing 787 Dreamliner aircraft, which has highly flexible wing structures than older-generation aircraft. As structural flexibility increases, aeroelastic interactions with aerodynamic forces and moments become an increasingly important consideration in aircraft design and aerodynamic performance. Furthermore, aeroelastic interactions with flight dynamics can result in issues with vehicle stability and control. Modern aircraft such as the Boeing 787 have technologies to compensate for adverse aeroelastic interactions with flight performance and dynamics.
2015-09-06
Technical Paper
2015-24-2430
Andrej Poredos, Peter Tibaut, Cristiano Pecollo, Dario Infanti, Giuseppe Falleti, Francesco Pascuzzi
Significant effort is being spent to improve the power performance and fuel economy of spark ignited engines. As the loading capability of IC engines increases, the thermal and mechanical load increase rapidly. Another aspect is that the amount of CO2 emissions per energy unit is relatively high from fossil fuels. Obviously, this is not desirable from the global climate perspective and has to be reduced. One efficient way of reducing these emissions would be to replace fossil fuels with other fuels, such as biofuels. Another way is to find ways to increase the efficiency of the current IC engines, leading to less CO2 emission for each unit volume of fuel. One of the most important fields related to this objective is heat transfer analysis. From the heat transfer perspective it is of interest to reduce the heat losses in the engine in an attempt to achieve higher mechanical work output.
2015-09-06
Technical Paper
2015-24-2406
Gyujin Kim, Kyoungdoug Min
Abstract The flamelet model is a widely used combustion model that demonstrates a good prediction of non-premixed combustion. In this model, the chemical time scales are considered to be smaller compared to those of the turbulence, which allows the heat and mass transfer equation to be decoupled from the flow equation. However, the model's dependency on the mixture fraction limits the combustion analysis to a single injection. To overcome this limitation, a two dimensional flamelet model, which uses two mixture fraction variables, was introduced to represent the non-premixed combustion of multiple injections. However, the model's computational time drastically increased due to the expansion of the solution domain. Thus, a modified 2-D flamelet model was introduced to reduce the computational time of the two dimensional flamelet model.
2015-09-06
Technical Paper
2015-24-2402
Irufan Ahmed, Golnoush Ghiasi, A. Gnana Sagaya Raj, Nedunchezhian Swaminathan, Jann Koch, Karel Steurs, Yuri M. Wright
Abstract Three-dimensional Computational Fluid Dynamics (CFD) has become an integral part in analysing engine in-cylinder processes since it provides detailed information on the flow and combustion, which helps to find design improvements during the development of modern engine concepts. The predictive capability of simulation tools depends largely on the accuracy, fidelity and robustness of the various models used, in particular concerning turbulence and combustion. In this study, a flamelet model with a physics based closure for the progress variable dissipation rate is applied for the first time to a spark ignited IC engine. The predictive capabilities of the proposed approach are studied for one operating condition of a gasoline port fuel injected single-cylinder, four-stroke spark ignited full-metal engine running at 3,500 RPM close to full load (10 bar BMEP) at stoichiometric conditions.
2015-09-06
Technical Paper
2015-24-2411
Carmelina Abagnale, Maria Cristina Cameretti, Umberto Ciaravola, Raffaele Tuccillo, Sabato Iannaccone
The dual-fuel (diesel/natural gas, NG) concept represents a solution to reduce emissions from diesel engines by using natural gas as an alternative fuel. As well known, the dual-fuel technology has the potential to offer significant improvements in the emissions of carbon dioxide from light-duty compression ignition engines. A further important requirement of the DF operation in automotive engines is a satisfactory response in a wide range of load levels. In particular, the part-load levels could present more challenging conditions for an efficient combustion development, due to the poor fuel/air ratio. Basing on the above assumptions, the authors discuss in this article the results of a combined numerical and experimental study on the effect of different injection timings on performance and pollutant fractions of a common rail diesel engine supplied with natural gas and diesel oil.
2015-09-06
Technical Paper
2015-24-2410
Stefania Falfari, Claudio Forte, Gian Bianchi, Giulio Cazzoli, Cristian Catellani, Lucio Postrioti, Fabrizio Ottobre
In the next incoming future the necessity of reducing the raw emissions leads to the challenge of an increment of the thermal engine efficiency. In particular it is necessary to increase the engine efficiency not only at full load but also at partial load conditions. In the open literature very few technical papers are available on the partial load conditions analysis. In the present paper the analysis of the effect of the throttle valve rotational direction on the mixture formation is analyzed. The engine was a PFI 4-valves motorcycle engine. The throttle valve opening angle was 17.2°, which lays between the very partial load and the partial load condition. The CFD code adopted for the analysis was the FIRE AVL code v. 2013.2. The exhaust, intake and compression phases till TDC were simulated: inlet/outlet boundary conditions from 1D simulations were imposed.
2015-09-06
Technical Paper
2015-24-2408
Nicola Giovannoni, Sebastiano Breda, Stefano Paltrinieri, Alessandro D'Adamo, Stefano Fontanesi, Francesco Pulvirenti
Abstract In spark-ignited direct-injected engines, the formation of fuel pools on the piston is one of the major promoters of unburnt hydrocarbons and soot: in order to comply with the increasingly stringent emission regulations (EU6 and forthcoming), it is therefore necessary to limit fuel deposit formation. The combined use of advanced experimental techniques and detailed 3D-CFD simulations can help to understand the mechanisms driving fuel pool formation. In the paper, a combined experimental and numerical characterization of pool formation in a GDI engine is carried out to investigate and understand the complex interplay of all the mentioned factors. In particular, a low-load low-rpm engine operation is investigated for different ignition phasing, and the impact of both fuel formulation and instantaneous piston temperature variations in the CFD analyses are evaluated.
2015-09-06
Technical Paper
2015-24-2413
Michela Costa, Francesco Catapano, Guido Marseglia, Ugo Sorge, Paolo Sementa, Bianca Maria Vaglieco
Abstract Gasoline direct injection (GDI) allows flexible operation of spark ignition engines for reduced fuel consumption and low pollutants emissions. The choice of the best combination of the different parameters that affect the energy conversion process and the environmental impact of a given engine may either resort to experimental characterizations or to computational fluid dynamics (CFD). Under this perspective, present work is aimed at discussing the assessment of a CFD-optimization (CFD-O) procedure for the highest performance of a GDI engine operated lean under both single and double injection strategies realized during compression. An experimental characterization of a 4-stroke 4-cylinder optically accessible engine, working stratified lean under single injection, is first carried out to collect a set of data necessary for the validation of a properly developed 3D engine model.
2015-09-06
Journal Article
2015-24-2401
Alessio Dulbecco, Stephane Richard, Christian Angelberger
Increasingly restrictive emission standards and CO2 targets drive the need for innovative engine architectures that satisfy the design constraints in terms of performance, emissions and drivability. Downsizing is one major trend for Spark-Ignition (SI) engines. For downsized SI engines, the increased boost levels and compression ratios may lead to a higher propensity of abnormal combustions. Thus increased levels of Exhaust Gas Recirculation (EGR) are used in order to limit the appearance of knock and super-knock. The drawback of high EGR rates is the increased tendency for Cycle-to-Cycle Variations (CCV) it engenders. A possible way to reduce CCV could be the generation of an increased in-cylinder turbulence to accelerate the combustion process. To manage all these aspects, 1D simulators are increasingly used. Accordingly, adapted modeling approaches must be developed to deal with all the relevant physics impacting combustion and pollutant emissions formation.
2015-09-06
Technical Paper
2015-24-2515
Christophe Barro, Sushant Pandurangi, Philipp Meyer, Konstantinos Boulouchos, Philipp Elbert, Yuri M. Wright
Abstract Past research has shown that post injections have the potential to reduce Diesel engine exhaust PM concentration without any significant influence in NOx emissions. However, an accurate, widely applicable rule of how to parameterize a post injection such that it provides a maximum reduction of PM emissions does not exist. Moreover, the underlying mechanisms are not thoroughly understood. In past research, the underlying mechanisms have been investigated in engine experiments, in constant volume chambers and also using detailed 3D CFD-CMC simulations. It has been observed that soot reduction due to a post injection is mainly due to two reasons: increased turbulence from the post injection during soot oxidation and lower soot formation due to lower amount of fuel in the main combustion at similar load conditions. Those studies do not show a significant temperature rise caused by the post injection.
2015-09-06
Technical Paper
2015-24-2432
Michela Costa, Paolo Sementa, Ugo Sorge, Francesco Catapano, Guido Marseglia, Bianca Maria Vaglieco
Abstract Present work investigates both experimentally and numerically the benefits deriving from the use of split injections in increasing the engine power output and reducing the tendency to knock of a gasoline direct injection (GDI) engine. The here considered system is characterized by an optical access to the combustion chamber. Imaging in the UV-visible range is carried out by means of a high spatial and temporal resolution camera through an endoscopic system and a transparent window placed in the piston head. This last is modified to allow the view of the whole combustion chamber almost until the cylinder walls, to include the so-called eng-gas zones of the mixture, where undesired self-ignition may occur under some circumstances. Optical data are correlated to in-cylinder pressure oscillations on a cycle resolved basis.
2015-09-06
Journal Article
2015-24-2436
Randy Hessel, Rolf D. Reitz, Zongyu Yue, Mark P. B. Musculus, Jacqueline O'Connor
Abstract This paper is part of a larger body of experimental and computational work devoted to studying the role of close-coupled post injections on soot reduction in a heavy-duty optical engine. It is a continuation of an earlier computational paper. The goals of the current work are to develop new CFD analysis tools and methods and apply them to gain a more in depth understanding of the different in-cylinder environments into which fuel from main- and post-injections are injected and to study how the in-cylinder flow, thermal and chemical fields are transformed between start of injection timings. The engine represented in this computational study is a single-cylinder, direct-injection, heavy-duty, low-swirl engine with optical components. It is based on the Cummins N14, has a cylindrical shaped piston bowl and an eight-hole injector that are both centered on the cylinder axis. The fuel used was n-heptane and the engine operating condition was light load at 1200 RPM.
2015-09-06
Technical Paper
2015-24-2469
Marlene Wentsch, Antonella Perrone, Marco Chiodi, Michael Bargende, Donatus Wichelhaus
Abstract Comparative analyses of a high-performance 4-cylinder DISI-engine and its equivalent single-cylinder research engine were performed by means of fast response 3D-CFD simulations. Both engines have identical geometries of intake and exhaust channels, cylinder head and piston. The used 3D-CFD tool QuickSim was developed at the Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart (FKFS), particularly for the numerical simulation of internal combustion engines (ICE). A calibration of the air consumption enabled a comparison of in-cylinder processes, including charge motion, mixture formation and combustion. All calculated operating points showed a similar trend. Deviations during the gas exchange phase led to a higher turbulence level and hence combustion velocity for the single-cylinder research engine. This resulted in a slightly higher maximum cylinder pressure and indicated mean effective pressure.
2015-06-15
Technical Paper
2015-01-2313
Bryce Gardner, Abderrazak Mejdi, Chadwyck Musser, Sébastien Chaigne, Tiago De Campos Macarios
Abstract Flow strongly affects the propagation of acoustics wave transmission within a duct and this must be addressed by the vibro-acoustic modelling of duct systems subject to non-uniform flow. Flow impacts both the effective sound propagation speed in a duct and refracts the sound towards or away from the duct walls depending on whether the acoustic waves are propagating in the direction of the flow or against the flow. Accurate modeling of the acoustic propagation within a duct is crucial for design and “tuning” of muffler systems that need to strongly attenuate narrowband acoustic sources from the engine. Muffler systems that may avoid matching acoustic resonances to engine narrowband sources when no flow is present may experience shifting of resonances to frequencies that match engine sources and cause problems when the flow during a real operating condition is present.
2015-06-15
Technical Paper
2015-01-2082
Andreas Tramposch, Wolfgang Hassler, Reinhard F.A. Puffing
Abstract Certain operating modes of the Environmental Control System (ECS) of passenger aircraft are accompanied with significant ice particle accretion in a number of pivotal parts of the system. Icing conditions particularly prevail downstream of the air conditioning packs and, as a consequence, ice particle accretion takes place in the Pack Discharge Duct (PDD) and in the mixing manifold. For a better understanding of these icing processes, numerical simulations using a multiphase model based on a coupled Eulerian-Lagrangian transport model in a generic PDD were performed. The obstruction of the PDD due to ice growth and the resulting change of the flow geometry were treated by deforming the computational mesh during the CFD simulations. In addition to the numerical investigations, a generic and transparent PDD was studied experimentally under several operating conditions in FH JOANNEUM's icing wind tunnel.
2015-06-15
Technical Paper
2015-01-2163
Caio Fuzaro Rafael, Diogo Mendes Pio, Guilherme A. Lima da Silva
Abstract The present paper presents a validation of momentum boundary-layer integral solution and finite-volume Reynolds-Averaged Navier Stokes (RANS) Computational Fluid Dynamics (CFD) results for skin friction around airfoils NACA 8H12 and MMB-V2 as well as heat transfer around an isothermal cylinder with rough surface. The objective is to propose a two-equation integral model and compare its predictions to results from a robust CFD tool, to experimental data and to results from a one-equation integral solution. The latter is the mathematical model used by classic 2D icing codes. All proposed model predictions are compared to CFD results for verification and, whenever possible, to experimental data for validation. The code-to-code verification brings reliability to both the proposed code and the CFD tool when there is no test data available.
2015-06-15
Technical Paper
2015-01-2327
Hangsheng Hou, Wei Zhao, Jian Hou
Abstract Wind noise is one of the most influential NVH attributes that impact customer sensation of vehicle interior quietness. Among many factors that influence wind noise performance, the amount of dynamic door deflection under the pressure load due to fast movement of a vehicle plays a key roll. Excessive deflection could potentially lead to loss of sealing contact, causing aspiration leakage, which creates an effectual path through which the exterior aerodynamically induced noise propagates into the vehicle cabin. The dynamic door deflection can be predicted using CFD and CAE approaches which, in addition to modeling the structure correctly, require a correct pressure loading composed of external and internal pressure distributions. The determination of external pressure distributions can be fulfilled fairly straightforward by using commercial CFD codes such as Fluent, Star CCM+, Powerflow and others.
2015-06-15
Journal Article
2015-01-2314
Adrien Mann, Min-Suk Kim, Barbara Neuhierl, Franck Perot, Robert Powell, Thomas Rose, Jan Krueger
Abstract Exhaust and muffler noise is a challenging problem in the transport industry. While the main purpose of the system is to reduce the intensity of the acoustic pulses originating from the engine exhaust valves, the back pressure induced by these systems must be kept to a minimum to guarantee maximum performance of the engine. Emitted noise levels have to ensure comfort of the passengers and must respect community noise regulations. In addition, the exhaust noise plays an important role in the brand image of vehicles, especially with sports car where it must be tuned to be “musical”. However, to achieve such performances, muffler and exhaust designs have become quite complex, often leading to the rise of undesired self-induced noise. Traditional purely acoustic solvers, like Boundary Element Methods (BEM), have been applied quite successfully to achieve the required acoustic tuning.
2015-04-14
Technical Paper
2015-01-1538
Neil Ashton, Alistair Revell
Abstract Computational Fluid Dynamics (CFD) is now one of the most important design tools for the automotive industry. Reliable CFD simulations of the complex separated turbulent flow around vehicles is becoming an ever more crucial goal to increase fuel efficiency and reduce noise emissions. In this study Reynolds Averaged Navier-Stokes (RANS) models (both at eddy-viscosity and second-moment closure levels) are compared to hybrid RANS-LES methods (Detached-Eddy Simulation). The application is the DrivAer model; a new open-source realistic car model which aims to bridge the gap between simple Ahmed body and MIRA/SAE Reference car models and actual car geometries in use by the major car manufacturers. To date, many hybrid RANS-LES studies on complex geometries have been under-resolved compared to more academic cases, due to a limit on computational resources available.
2015-04-14
Technical Paper
2015-01-1536
Brett C. Peters, Mesbah Uddin, Jeremy Bain, Alex Curley, Maxwell Henry
Abstract Currently, most of the Navier-Stokes equation based Computational Fluid Dynamic solvers rely heavily on the robustness of unstructured finite volume discretization to solve complex flows. Widely used finite volume solvers are restricted to second order spatial accuracy while structured finite difference codes can easily resolve up to five orders of spatial discretization and beyond. In order to solve flow around complicated geometries, unstructured finite volume codes are employed to avoid tedious and time consuming handmade structured meshes. By using overset grids and NASA's overset grid solver, Overflow, structured finite difference solutions are achievable for complex geometries such as the DrivAer [1] model. This allows for higher order flow structures to be captured as compared to traditional finite volume schemes. The current paper compares flow field solutions computed with finite volume and finite difference methods to experimental results of the DrivAer model [1].
2015-04-14
Technical Paper
2015-01-1535
Kentaro Machida, Munetsugu Kaneko, Atsushi Ogawa
Abstract This paper discusses the characteristic flow field of the new Honda FIT/Jazz as determined from the aerodynamic development process, and introduces the technique that reduced aerodynamic drag in a full model change. The new FIT was the first model to take full advantage of the Flow Analysis Simulation tool (FAST), our in-house CFD system, in its development. The FAST system performs aerodynamic simulation by automatically linking the exterior surface design with a predefined platform layout. This allows engineers to run calculations efficiently, and the results can be shared among vehicle stylists and aerodynamicists. Optimization of the exterior design gives the new FIT a moderate pressure peak at the front bumper corner as compared to the previous model, resulting in a smaller pressure difference between the side and underbody.
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