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Viewing 1 to 30 of 1966
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 engine geometry was formed by the intake duct and the cylinder. The throttle valve opening angle was 17.2 deg, 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 intake and the compression phases till TDC were simulated: inlet boundary conditions from 1D simulations were imposed.
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
Three-dimensional Computational Fluid Dynamics (CFD) has become an integral part in analyzing engine in-cylinder processes since it provides detailed information on flow and combustion inside internal combustion engines, hence allowing for 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 model used, in particular concerning turbulence and combustion, and, in some cases, two-phase flow. Almost all combustion models currently used in engine design require some level of parameter tuning to obtain a reasonable match between measured and computed in-cylinder pressure evolution. However, if the model parameters are closely tied to the physics of the problem then one might be able to eliminate this model tuning, specifically for the combustion sub-modeling part.
2015-09-06
Technical Paper
2015-24-2406
Gyujin Kim, Kyoungdoug Min
Development of injection technologies such as common-rail direct injection allows multiple injection strategy in Diesel Engine, which can reduce emissions, noises and vibrations. Meanwhile, three dimensional combustion model using CFD can be a good apparatus to visualize the in-cylinder phenomena. RIF (Representative Interactive Flamelet) model shows a good prediction of non-premixed combustion. In RIF model, chemical time scales are considered to be smaller than those of turbulence, which can decouple the equations of heat and mass transfer from flow equations. Furthermore, theses governing equations can be described by one conserved scalar which is called mixture fraction by using the assumption that the flame is sufficient to thin in the direction orthogonal to the flame surface. However, its dependency on the mixture fraction set a limit on the combustion analysis for the single injection.
2015-09-06
Technical Paper
2015-24-2515
Christophe Barro, Sushant Pandurangi, Philipp Meyer, Konstantinos Boulouchos, Philipp Elbert, Yuri M. Wright
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
2015-24-2411
Carmelina Abagnale, Maria Cristina Cameretti, Umberto Ciaravola, Raffaele Tuccillo, Sabato Iannaccone
The dual-fuel (diesel/natural gas, NG) concept represents a viable solution to reduce emissions from diesel engines by using natural gas as an alternative fuel. The dual fuel operation is characterized by a diesel pilot injection to activate the combustion of NG that has been premixed with air in the intake port. 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. In these small-displacement high-speed engines, where the combustion event can be temporally shorter, the injection timing can exert an important effect on the performance and emissions of the engine. 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.
2015-09-06
Technical Paper
2015-24-2432
Michela Costa, Paolo Sementa, Ugo Sorge, Francesco Catapano, Guido Marseglia, Bianca Maria Vaglieco
Knocking combustion in spark ignition engines is an abnormal combustion phenomenon strongly affecting performance and thermal efficiency. The possibility to have abnormal combustions in a GDI (gasoline direct injection) engine is linked to the outcome of the mixture formation process. Present work explores possible advantages deriving from the use of split injections in increasing the engine power output and reducing the tendency to knock. Due to the recent development of gasoline injection systems, multiple injections are today regarded as a valuable tool to improve the in-chamber evaporation process and simultaneously reduce undesired effects deriving from an excessive spray impact over walls. Combustion stability is enhanced, unburned hydrocarbons and soot emissions are limited.
2015-09-06
Technical Paper
2015-24-2436
Randy Hessel, Rolf D. Reitz, Zongyu Yue, Mark P. B. Musculus, Jacqueline O'Connor
The major topics of this paper are: to validate CFD estimates of in-cylinder soot distribution to soot natural luminosity measurements in a single-cylinder, optically-accessible research engine utilizing close-coupled post-injections; to visualize and quantify how post-injections disrupt and alter the progression of main-injection initiated soot; and to use full-3D CFD results to help interpret line-of-sight integrated soot-natural-luminosity measurements. The first stage effort at modeling these post-injection experiments is summarized in SAE Technical Paper 2014-01-1256. A major contribution of that work is the ability to visualize and quantify soot formation, oxidation and net-soot as distinct quantities. These capabilities are important, because they allow detailed analysis of CFD results so that the root causes of engine-out soot can be evaluated on a fundamental level. The current work augments the previous in at least three important ways, as is described next.
2015-09-06
Technical Paper
2015-24-2401
Alessio Dulbecco, Stephane Richard, Christian Angelberger
The respect of engine emissions standards and CO2 targets defined by the public authorities impose to car manufacturers to increase their investments into R&D activities. Accordingly, a multitude of innovative engine architectures are proposed and evaluated to identify the best solution satisfying all the constraints, expressed in terms of engine performance, emissions and drivability; recent trends for SI engine architectures identify the downsizing technology as a promising way to success. Nevertheless, the required increased boost levels and compression ratio amplify the appearance of abnormal combustions; accordingly, to avoid knock and super-knock, dilution of the in-cylinder fresh charge with Exhaust Gas Recirculation (EGR) is more and more used. The drawback of the use of high EGR rates is the destabilization of the combustion process which appears as an increase of the in-cylinder pressure Cycle-to-Cycle Variations (CCV).
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.
2015-06-15
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
2015-01-1738
Dileep Namdeorao Malkhede, Hemant Khalane
Abstract Due to reciprocating nature of IC engine, flow physics in intake manifold is complex and has significant effect on volumetric efficiency. Variable length intake manifold technology offers potential for improving engine performance. This paper therefore investigated effect of intake length on volumetric efficiency for wider range of engine speeds. For this purpose 1-D thermodynamic engine model of a single cylinder 611cc standard CFR engine capable of predicting pressure waves in the intake was developed. For validation, pressure waves were predicted at two different locations on intake manifold and compared against test data. This model was used to predict volumetric efficiency for different intake lengths and engine speeds. Volumetric efficiency was found to be a function of both engine speed and intake length, more so at higher engine speeds. Frequency analysis of intake pressure waves during suction stroke and intake valve closed phase was carried out separately.
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.
2015-04-14
Technical Paper
2015-01-1534
Daisuke Nakamura, Yasuyuki Onishi, Yoshiyasu Takehara
Abstract There is a need to reduce vehicle's running resistance through aerodynamic performance in terms of having less negative impact on the global environment. In the Accord full model change, the package design is changed, so it is an opportunity to propose methods for improving aerodynamic performance. During the preliminary study, phenomenon analyses were conducted to identify areas that have a significant effect on aerodynamics by using a 25% scale model of the previous model. Based on more than 500 variation measurements as parameter study, the analysis was conducted using computational fluid dynamics (CFD). A proposal was made to the package design. For development that began with the fundamental frame proposed in preliminary studies, wind tunnel testing using 25% scale model was conducted jointly with the Styling Design Office to achieve enhancement styling while also increasing aerodynamic performance.
2015-04-14
Technical Paper
2015-01-1533
Massimiliana Carello, Serra Andrea, Andrea Giancarlo Airale, Alessandro Ferraris
XAM is a two-seat city vehicle prototype developed at the Politecnico di Torino, equipped with a hybrid propulsion system to obtain low consumptions and reduced environmental impact. The design of this vehicle was guided by the requirements of weight reduction and aerodynamic optimization of the body, aimed at obtaining a reduction of resistance while guarantying roominess. The basic shape of the vehicle corresponding to the requirements of style, ergonomics and structure were deeply studied through CFD simulation in order to assess its aerodynamic performance (considering the vehicle as a whole or the influence of the various details and of their changes separately). The most critical areas of the body (underfloor, tail, spoiler, mirrors, A-pillar) were analyzed creating dedicated refinement volumes.
2015-04-14
Technical Paper
2015-01-1541
Kuo-Huey Chen, Bahram Khalighi
Abstract Various drag reduction strategies have been applied to a full size production pickup truck to evaluate their effectiveness by using Computational Fluid Dynamics (CFD). The drag reduction devices evaluated in this study were placed at the rear end of the truck bed and the tailgate. Three types of devices were evaluated: (1) boat tail-like extended plates attached to the tailgate; (2) mid-plate attached to the mid-section of the tailgate and; (3) flat plates partially covering the truck bed. The effect of drag reduction by various combinations of these three devices are presented in this paper. Twenty-four configurations were evaluated in the study with the best achievable drag reduction of around 21 counts (ΔCd = 0.021). A detailed breakdown of the pressure differentials at the base of the truck is provided in order to understand the flow mechanism for the drag reductions.
2015-04-14
Technical Paper
2015-01-1549
Jonathan Jilesen, Iwo Spruss, Timo Kuthada, Jochen Wiedemann, Adrian Gaylard
Abstract Driving when it is raining can be a stressful experience. Having a clear unobstructed view of the vehicles and road around you under these conditions is especially important. Heavy rain conditions can however overwhelm water management devices resulting in water rivulets flowing over the vehicle's side glass. These rivulets can significantly impair the driver's ability to see the door mirror, and laterally onto junctions. Designing water management features for vehicles is a challenging venture as testing is not normally possible until late in the design phase. Additionally traditional water management features such as grooves and channels have both undesirable design and wind noise implications. Having the ability to detect water management issues such as A-pillar overflow earlier in the design cycle is desirable to minimize the negative impact of water management features. Numerical simulation of windscreen water management is desirable for this reason.
2015-04-14
Technical Paper
2015-01-1693
Mark Allen, Graham Hargrave, Petros Efthymiou, Viv Page, Jean-Yves Tillier, Chris Holt
Abstract It is an engineering requirement that gases entrained in the coolant flow of an engine must be removed to retain cooling performance, while retaining a volume of gas in the header tank for thermal expansion and pressure control. The main gases present are air from filling the system, exhaust emissions from leakage across the head gasket, and also coolant vapour. These gases reduce the performance of the coolant pump and lower the heat transfer coefficient of the fluid. This is due to the reduction in the mass fraction of liquid coolant and the change in fluid turbulence. The aim of the research work contained within this paper was to analyse an existing phase separator using CFD and physical testing to assist in the design of an efficient phase separator.
2015-04-14
Technical Paper
2015-01-0382
Johann Spreitzer, Felix Zahradnik, Bernhard Geringer
Abstract This paper describes the development of a comprehensive simulation environment for investigations of gas-dynamic processes and combustion phenomena in rotary engines, conducted by the Austrian Institute for Powertrains and Automotive Technology of the Vienna University of Technology. In this connection, proven, commercially available engine cycle calculation Software-Tools have been used. For this, a rotary engine test bench has been established. As analysis tools, in addition to the traditional acquisition of the emitted engine torque, various pressures and temperatures, the recording of the pressure profile (combustion analysis measurement system) in the combustion chamber, as well as in the intake and exhaust ports, were used. The data of the test bench were used to develop and validate the methodology for the simulation tools. The focus in this paper is the development of a CFD (computational fluid dynamics) model with the software Converge from Convergent Science, Inc.
2015-04-14
Technical Paper
2015-01-0360
Maryline Leriche, Wolfgang Roessner, Heinrich Reister, Bernhard Weigand
Abstract An accurate model to predict the formation of fogging and defogging which occurs for low windshield temperatures is helpful for designing the air-conditioning system in a car. Using a multiphase flow approach and additional user-defined functions within the commercial CFD-software STAR-CCM+, a model which is able to calculate the amount of water droplets on the windshield from condensation and which causes the fogging is set up. Different parameters like relative humidity, air temperature, mass flow rate and droplet distributions are considered. Because of the condition of the windshield's surface, the condensation occurs as tiny droplets with different sizes. The distribution of these very small droplets must be obtained to estimate numerically the heat transfer coefficient during the condensation process to predict the defogging time.
2015-04-14
Technical Paper
2015-01-0392
Mohammad Izadi Najafabadi, Bart Somers, Abdul Aziz Nuraini
Homogeneous Charge Compression Ignition (HCCI) combustion technology has demonstrated a profound potential to decrease both emissions and fuel consumption. In this way, the significance of the 2-stroke HCCI engine has been underestimated as it can provide more power stroke in comparison to a 4-stroke engine. Moreover, the mass of trapped residual gases is much larger in a 2-stroke engine, causing higher initial charge temperatures, which leads to easier auto-ignition. For controlling 2-stroke HCCI engines, it is vital to find optimized simulation approaches of HCCI combustion with a focus on ignition timing. In this study, a Computational Fluid Dynamic (CFD) model for a 2-stroke gasoline engine was developed coupled to a semi-detailed chemical mechanism of iso-octane to investigate the simulation capability of the considered chemical mechanism and the effects of different simulation parameters such as the turbulence model, grid density and time step size.
2015-04-14
Technical Paper
2015-01-0396
Bryce Charles Thelen, Gerald Gentz, Elisa Toulson
Abstract Fully three-dimensional computational fluid dynamic simulations with detailed chemistry of a single-orifice turbulent jet ignition device installed in a rapid compression machine are presented. The simulations were performed using the computational fluid dynamics software CONVERGE and its RANS turbulence models. Simulations of propane fueled combustion are compared to data collected in the optically accessible rapid compression machine that the model's geometry is based on to establish the validity and limitations of the simulations and to compare the behavior of the different air-fuel ratios that are used in the simulations.
2015-04-14
Technical Paper
2015-01-0398
Lorenzo Bartolucci, Stefano Cordiner, Vincenzo Mulone, Vittorio Rocco, Edward Chan
Abstract The aim of this work is to assess the accuracy of results obtained from Large Eddy Simulations (LES) of a partially-premixed natural gas spark-ignition combustion process in a Constant Volume Combustion Chamber (CVCC). To this aim, the results are compared with the experimental data gathered at the University of British Columbia. The computed results show good agreement with both flame front visualization and pressure rise curves, allowing for drawing important statements about the peculiarities of the Partially Stratified Combustion ignition concept and its benefits in ultra-lean combustion processes.
2015-04-14
Technical Paper
2015-01-0399
Alexander Jaust, Bastian Morcinkowski, Stefan Pischinger, Jens Ewald
Abstract In this work, a transport and mixing model that calculates mixing in thermodynamic phase space was derived and validated. The mixing in thermodynamic multizone space is consistent to the one in the spatially resolved physical space. The model is developed using a turbulent channel flow as simplified domain. This physical domain of a direct numerical simulation (DNS) is divided into zones based on the quantitative value of transported scalars. Fluxes between the zones are introduced to describe mixing from the transport equation of the probability density function based on the mixing process in physical space. The mixing process of further scalars can then be carried out with these fluxes instead of solving additional transport equations. The relationship between the exchange flux in phase space and the concept of scalar dissipation are shown and validated by comparison to DNS results.
2015-04-14
Technical Paper
2015-01-0402
P Brijesh, S Abhishek, S Sreedhara
Abstract The mixture generation in Diesel engines is mainly driven by the combustion chamber geometry and the fuel spray characteristics. Thus, combustion chamber geometry is considered as an important parameter for Diesel engine in-cylinder emission control strategy. In this work, effect of nozzle tilt angle and various combustion chamber geometries such as mexican-hat combustion chamber (MHCC), double-lip combustion chamber (DLCC), bow combustion chamber (BCC) and toroidal combustion chamber (TCC) on in-cylinder processes and emissions has been studied numerically using a CFD-tool called Converge. Converge code has been validated against the experimental results of a Diesel engine. Results showed that a significant reduction in soot, HC and CO has been achieved with the optimum (156°) nozzle tilt angle; but NOx was increased.
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