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Viewing 1 to 30 of 1929
2015-04-14
Technical Paper
2015-01-0662
Weiguo Zhang, Mac Lynch, Robert Reynolds
A turbocharger is currently widely used to boost performance of an internal combustion engine. Generally, a turbocharger consists of a compressor which normally is driven by an exhaust turbine. Both the compressor and the turbine will have an influence on how the low frequency engine pulsation propagates in the intake and exhaust system. In addition, the turbocharger will produce high frequency flow induced sound. The high frequency sound generation is associated with rotating blade pressures, supersonic tip speeds or rotating shock waves. This paper focuses on the application of computational fluid dynamics (CFD) to the prediction of this high frequency flow induced sound. A turbocharger compressor is generally a centrifugal compressor consisting of wheel, diffuser and housing. As the compressor wheel rotates, ambient air is drawn in axially through an air induction system, accelerated to high speed and then expelled in a radial direction to the outlet.
2015-04-14
Technical Paper
2015-01-1377
Hiroshi Yokoyama, Atsushi Otani, Naoyuki Shirota, Takao Umezawa
Windshield wipers and washers are essential for safety driving of motor vehicles and expected to steadily provide a good field of vision under various weather and environment conditions. However, there is a concern that washers are likely to be affected by several factors such as fast air flow at high speed driving and high washer fluid viscosity at low temperature, which may result in unsatisfactory distribution of washer fluid onto windshields. As another example, particularly-high cleaning performance is required while vehicles are running on a winter road with mud and salt. Conversely, if these concerns are resolved, washers can contribute more to vehicle safety. Thus, we have developed a washer nozzle with a self-oscillating flow passage focusing on distributing appropriate amount of washer fluid.
2015-04-14
Technical Paper
2015-01-1075
Wan Mohd Faizal Wan Mahmood
In-cylinder soot particle size and its distribution are of interest to engine designers and researchers as they influence the soot emitted from exhaust tailpipes as well as the soot in oil.  The focus of this present study is to analyse changes in soot particle size along predicted pathlines as they pass through different in-cylinder combustion histories.  The prediction of a soot particle pathline, size and how it is transported in the cylinder of a direct injection diesel engine was performed using post-processed in-cylinder combustion data from Kiva-3v CFD simulations with a series of Matlab routines.  Soot particles were assumed massless and only soot surface growth and oxidation processes were considered in calculating the sizes.  3500 locations at 8° Crank Angle (CA) ATDC were selected inside the engine cylinder at the beginning of the pathline and size calculation.  
2015-04-14
Technical Paper
2015-01-1336
Meisam Mehravaran, Yi Zhang
Computational Fluid Dynamics (CFD) has been extensively used in predicting the behavior of automotive components. In the current work the fan, shroud and radiator assembly has been simulated using a less expensive CFD methodology. After validating the CAE tool with the test data, the similar simulation was carried on for 13 different shrouds and the effect of geometrical parameters on airflow was investigated. The CFD data show that the smoothly converging shroud will lead to higher flow rates while cavities and steps will perform as a restriction and degrade the efficiency. Besides, it is seen that decreasing the blade-shroud clearance up to 17 mm will improve the air flow as it prevents the leakage of the pumped flow, but if we go further, the airflow does not increase and may even decrease, which may be explained based on the interference of blade and shroud boundary layer.
2015-04-14
Technical Paper
2015-01-1656
Lisa Henriksson, Peter Gullberg, Erik Dahl, Lennart Lofdahl
For some vehicle segments the cooling demand is increasing as a result of increased engine power or introduction of different systems, for example EGR, CAC, WHR. To be able to fulfil the increased cooling demand an increased efficiency of the cooling device or an increased cooling package are required. Due to limitations of space at the front of the vehicle, behind the grill, alternative positions of extra heat exchangers have to be evaluated. Common for most of these positions is that the oncoming airflow is not necessarily perpendicular to the heat exchanger core. Evaluation of inclined airflows relative to the heat exchanger must therefore be performed. This article presents CFD simulations on one period of a louvered fin of compact louvered fin heat exchangers, where the incoming airflow was inclined relative to the heat exchanger core.
2015-04-14
Technical Paper
2015-01-1284
Enrico Mattarelli, Carlo Alberto Rinaldini
Among all the reciprocating internal combustion engines, gasoline two-strokes can reach the highest specific power, making this technology a natural enabler of downsizing. Conventional designs (crankcase scavenging, reed valves) are not suitable for automotive applications, however alternative solutions may be able to address the typical issues, while maintaining the well-known advantages (specific power, compactness , cost above all). In addition, multi-cylinder 2-stroke engines may be an ideal match for electrical assisted turbochargers and/or superchargers, providing very efficient power units. The paper explores through CFD-1d simulations the potential of a 3-cylinder, 1.0 liter, GDI 2-stroke turbocharged engine featuring a patented rotary valve for the optimization of the scavenging process, the latter being of the loop type (piston-controlled ports). The lubrication system is the same of a 4-stroke engine (no crankcase pumps). Two types of supercharging systems are analyzed.
2015-04-14
Technical Paper
2015-01-0939
Daliang Jing, Shi-Jin Shuai, Zhi Wang, Yanfei Li, Hongming Xu
With the increasing demand of energy conservation and environmental protection, further improvement of fuel efficiency and emission reduction in internal combustion engines are urgently required due to the limited energy reserves, rising price of crude oil and climate change. Gasoline direct injection (GDI) engine plays an important part in this area and has experienced a rapid development during the last decade. The design and optimization of a modern spray-guided GDI engine requires a thorough understanding of the fuel sprays characteristics and atomization process. The fuel spray Computational Fluid Dynamics (CFD) modeling technology can be an effective means to study and predict spray characteristics, and as a consequence, to drastically reduce experimental work during the engine development process. For this reason, an accurate numerical simulation of the spray evolution process is imperative.
2015-04-14
Technical Paper
2015-01-0948
Le (Emma) Zhao, Ahmed Abdul Moiz, Jeffrey Naber, Seong-Young Lee, Sam Barros, William Atkinson
Liquid spray breakup and atomization, two multi-phase phenomena, strongly affect the ignition and combustion processes. High-speed jet-to-jet impingement in water sprays could be an effective phenomenon for the spray propagation and droplet vaporization. To achieve higher vaporization efficiency, impingement from two-hole nozzles is analyzed in this paper. This paper focuses on investigating vaporization mechanism as a function of the impingement location and the collision breakup process provided by two-hole impinging jet nozzles. CFD (Computational Fluid Dynamics) is adopted to do simulation. Lagrangian model is used to predict jet-to-jet impingement and droplet breakup conditions while KH-RT breakup and O’Rourke collision models are implemented for the simulation.
2015-04-14
Technical Paper
2015-01-1373
Yulong Lei, Hui Tang, Xingjun Hu, Ge Lin, Bin Song
With the continuous improvement of the road condition, commercial vehicles get to be faster and more overloaded than before, which puts higher pressure on the vehicle braking system. Conventional friction braking has been difficult to meet the needs of high-power commercial vehicle. The auxiliary brake equipment will become the future trend for commercial vehicle. Hydraulic retarder is superior secondary braking equipment. Previously hydraulic retarder research mainly focus on flow field analysis, the braking torque calculation, cascade system optimization and control methods for hydraulic retarder. The gas-liquid two-phase flow in working chamber is less researched. Based on this, this article discusses on the hydraulic retarder from two aspects, including CFD numerical modeling method, transient characteristics of oil-filling , which provides support for hydraulic retarder design and matching in the vehicle. The main contents and conclusions are as follows: 1.
2015-04-14
Technical Paper
2015-01-1329
Katsutomo Kanai, Hideki Katsuyama
We developed a method of predictive simulation of flow-induced noise using computational fluid dynamics. Because the goal was to employ the method in the automotive development process, development sought to balance practical predictive accuracy and computation time. In order to simulate flow-induced noise, detailed eddy flows and changes in the density of the air must be computed. In the development discussed in this paper, we conducted unsteady-state compressible computations using large eddy simulation, a type of turbulence modeling, to predict whether flow-induced noise would occur. The target flow-induced noise was narrow-band noise, also known as whistling noise, a type of noise that increases in a specific frequency range. The target area of generation of flow-induced noise was set as the exhaust pipe, which incorporates the complex shape of the muffler.
2015-04-14
Technical Paper
2015-01-1558
Amir Kharazi, Edward Duell, Austin Kimbrell, Ann Boh
Unsteady flow over automotive side-view mirrors may cause flow-induced vibrations of the mirror assembly which can result in blurred rear-view images, adversely affecting marketability and driver safety, as well as customer comfort and quality perception. Prior research has identified two mechanisms by which aerodynamically induced vibrations are introduced in the mirror. The first mechanism is unsteady aero pressure loading on the mirror face due to the unsteady wake, causing direct vibration of the mirror glass. The second mechanism, and the focus of this study, is a fluctuating loading on the mirror housing caused by an unsteady separation zone on the outer portion of the housing. A time-dependent Computational Fluid Dynamics (CFD) methodology to correctly model mirror wake behavior, and thereby predict flow-induced mirror vibration to improve performance estimations, was developed.
2015-04-14
Technical Paper
2015-01-1342
Christoph Huber, Bernhard Weigand, Heinrich Reister, Thomas Binner
A physically based model to predict the amount of snow which is entering the air intake of an automobile is very helpful for the automotive industry. It allows to improve the air intake system in the development state so that new vehicles can be developed in less time. Using an Eulerian/Lagrangian approach within a commercial CFD-software we set up a model and calculated the snow ingress into an air intake of an automobile. In our numerical investigations we considered different particle shapes, different coefficients of restitution and different particle sizes. Furthermore two-way coupling was considered. To obtain important information for the simulation, we measured the size of snow particles in the Daimler climatic wind tunnel by using a microscope and by using a measuring device from Malvern. Besides we used mechanical snow traps to determine the snow mass flux in the climatic wind tunnel and on a test area in Sweden.
2015-04-14
Technical Paper
2015-01-0391
Yoshihiro Sukegawa, Kazuhiro Oryoji
With the tightening of emission regulations for automobiles, reduction of Particulate Matter (PM) from spark ignition gasoline engines is one of the urgent problems. Inadequate fuel evaporation and/or fuel/air mixing in a cylinder are thought to be a cause of PM formation in gasoline engines. So it is required to find appropriate fuel injection control and spray placement method to lower PM emission. Computational Fluid Dynamics (CFD) is one of useful tool to optimize such parameters. As estimation techniques of PM emitted from internal combustion engines, some methods which solve transportation equations of PM with combustion simulation in an engine are well known. However most PM prediction models have been constructed based on diesel combustion. It is expected that since diffusion flame is dominant in diesel engines, PM generation characteristics will be different from gasoline engines in which premix flame is dominant.
2015-04-14
Technical Paper
2015-01-0890
Barbara Graziano, Florian Kremer, Karl Alexander Heufer, Hans Rohs, Stefan Pischinger
Nowadays restrictions on pollutant emissions produced by Internal Combustion Engines (ICEs) require a holistic investigation on alternative fuels able to optimize the combustion process and ensure a cleaner combustion. The Tailor-made Fuel from Biomass (TMFB) Cluster at RWTH Aachen University aims at designing optimal production processes for biofuels as well as ideal surrogate fuels for ICE applications. The TMFB Cluster’s scientific approach considers the fuel’s molecular structure as further degree of freedom for the optimization of both the biofuels’ production pathways and their combustion process. Thus, model-based specification of target parameters is of primary importance to improve the engine combustion performances and give feedback information to the production area. In particular a 3D CFD tool is used herein to underline the role played by the thermo-physical properties on the soot emissions in ICEs.
2015-04-14
Technical Paper
2015-01-1057
Scott Drennan, Gaurav Kumar, Shaoping Quan, Mingjie Wang
Controlling NOx emissions from vehicles is a key aspect of meeting new regulations for cars and trucks across the world. Selective Catalytic Reduction (SCR) is a NOx reduction option that many engine manufacturers are adopting. The performance of urea injection and mixing upstream of an SCR catalyst is critical in obtaining reliable NOx reduction. Computational Fluid Dynamic (CFD) simulations of urea injection systems have become an important development and diagnostic tool for designers. Designers are interested in applying more accurate spray and kinetic models to their CFD simulations and in reducing mesh generation time. This paper presents the application of an automatically generated Cartesian meshing approach to a urea liquid injection system. Investigations of the impact of injection and operating conditions are presented for a model urea-water injection case.
2015-04-14
Technical Paper
2015-01-1738
Dileep Namdeorao Malkhede, Hemant Khalane
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 pulsations in the intake was developed. For validation, pressure pulsations 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. FFT analysis of intake pressure pulsations during suction stroke and intake valve closed phase was carried out separately.
2015-04-14
Technical Paper
2015-01-0379
Yongli Qi, Xinyu Ge, Lichun Dong
The Hybrid vehicle engines modified for high exhaust gas recirculation (EGR) is a good choice for high efficiency and low NOx emissions. However, high EGR will dilute the engine charge and may cause serious performance problems such as incomplete combustion, torque fluctuation, and engine misfire. An efficient way to overcome these drawbacks is to intensify tumble leading to increased turbulent intensity at the time of ignition. The enhancement of turbulent intensity will increase flame velocity and improve combustion quality, therefore increasing engine tolerance to higher EGR. To achieve the goal of increasing tolerance to EGR, this work reports a CFD investigation of high tumble intake port design using STAR-CD. The validations had been performed through the comparison with PIV experimental tests.
2015-04-14
Technical Paper
2015-01-0395
Federico Piscaglia, Andrea Montorfano, Angelo Onorati
Swirling flows are very dominant in applied technical problems, especially in IC engines, and their prediction requires rather sophisticated modeling. An adaptive low-pass filtering procedure for the modeled turbulent length and time scales is derived and applied to Menter' original number k-omega SST turbulence model. The modeled length and time scales are compared to what can potentially be resolved by the computational grid and time step. If the modeled scales are larger than the resolvable scales, the resolvable scales will replace the modeled scales in the formulation of the eddy viscosity; therefore, the filtering technique helps the turbulence model to adapt in accordance with the mesh resolution and the scales to capture.
2015-04-14
Technical Paper
2015-01-0402
P Brijesh, S Abhishek, S Sreedhara
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 engine performance and in-cylinder emission control strategy. In this work, effect of various combustion chamber geometries and nozzle cone angle (nozzle rotational angle in X-Z plane) on in-cylinder processes and emissions has been studied numerically using Converge CFD–tool. The Converge CFD–tool can be used for the simulations of three–dimensional, compressible or in-compressible, chemically reacting transient fluid flows in complex geometries with stationary or moving surfaces. Ease of gridding, adaptive mesh refinement (AMR) capabilities and ease of parallelization made this tool very attractive to solve practical problems.
2015-04-14
Technical Paper
2015-01-1727
Francesco Balduzzi, Giovanni Vichi, Luca Romani, Giovanni Ferrara, Paolo Trassi, Jacopo Fiaschi, Federico Tozzi
High specific fuel consumption and pollutant emissions are the main drawbacks of the small crankcase-scavenged two-stroke engine. The symmetrical timing of the scavenging ports combined with a carburetor or an indirect injection system leads to a lower scavenging efficiency than a four-stroke engine and to the short-circuit of fresh air-fuel mixture. The use of fuel supply systems as the indirect injection and the carburetor are the standard solutions for a small two-stroke engine equipment, due to necessity of reducing the complexity, weight, overall dimensions and costs. This paper presents the results of a detailed study on the application of an innovative Low Pressure Direct Injection system (LPDI) to an existing 300 cc cylinder formerly equipped with a carburetor. The proposed solution is characterized by two injectors working at 5 bar of injection pressure.
2015-04-14
Technical Paper
2015-01-0376
Tommaso Lucchini, Augusto Della Torre, Gianluca D'Errico, Gianluca Montenegro, Marco Fiocco, Amin Maghbouli
Prediction of in-cylinder flows and fuel-air mixing are two fundamental pre-requisites for a successful simulation of direct-injection engines. Over the years, many efforts were carried out in order to improve available turbulence and spray models. However, enhancements in physical modeling can be drastically affected by mesh structure and quality which can negatively influence the predicted structure of organized charge motions, turbulence generation and interaction between in-cylinder flows and injected sprays. This is even more relevant for modern direct injection engines where multiple injections and control of charge motions are employed in a large portion of the operating map. Currently, two different approaches for mesh generation exist: manual and automatic. The first makes generally possible to generate high-quality meshes but, at the same time, it is very time consuming and not completely free from user errors.
2015-04-14
Technical Paper
2015-01-0382
Johann Spreitzer, Felix Zahradnik, Bernhard Geringer
The aim of this paper is the development of a complete Simulation environment for investigation of gas-dynamic processes and combustion phenomena in rotary engines. This project was done by the Austrian Institute for Powertrains and Automotive Technology of the Vienna University of Technology. Commercially available and in engine process calculation proven Software-Tools have been used as basis. For this, a rotary engine test bench has been established and the real engine has been studied in detail. As analysis tools, in addition to the traditional acquisition of the emitted engine torque, various pressures and temperatures, the recording of the pressure profile in the combustion chamber, as well as in the intake and exhaust ports, were used. The thus obtained data of the test bench were used to develop and validate the methodology for the simulation tools. As basis for the presented 1D-simulation program the commercial program GT-Power of Gamma Technologies, Inc. is used.
2015-04-14
Technical Paper
2015-01-0392
Mohammad Izadi Najafabadi, Bart Somers, Abdul Aziz Nuraini PhD
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
2015-01-0393
Alessandro d'Adamo, Fabio Berni, Sebastiano Breda, Mattia Lugli, Stefano Fontanesi, Giuseppe Cantore
Engine downsizing is gaining popularity in the high performance engine market sector, where a new generation of highly downsized engine with specific power outputs around or above 150 HP/litre is emerging. High-boost and downsizing to increase power density and reduce fuel consumption have to face the increased risks of pre-ignition, knock or mega-knock. To counterbalance auto-ignition of fuel/air mixture, currently made turbocharged SI engines usually operate with high fuel enrichments and delayed (sometimes negative) spark advances. The former is responsible for high fuel consumption levels, while the latter induce an even lower A/F ratio (below 11), to limit the turbine inlet temperature, with huge negative effects on BSFC.
2015-04-14
Technical Paper
2015-01-0398
Lorenzo Bartolucci, Stefano Cordiner, Vincenzo Mulone, Vittorio Rocco, Edward Chan
In this paper the effects of the adoption of a Partially Stratified Charge (PSC) combustion strategy on the performance of a lean natural gas fueled engine are compared with the ones obtainable with a strategy based on the traditional Homogeneous Combustion process. To that final aim, a CFD 3D model, based on Large Eddy Simulation, has been used to represent the combustion process on a dynamic full 3D engine mesh, taking into proper account all the different phases (intake, combustion and exhaust). The combustion model has been validated via comparison of the flame front development in a Constant Volume Combustion Chamber (CVCC), and then applied to study a single cylinder engine research engine to have an idea of the impact of the real cylinder flow onto the combustion processes and its influence on the main engine parameters. The benefits of the PSC combustion have been checked via several indicators, such as pressure history, energy heat release and flame front turbulent speed.
2015-04-14
Technical Paper
2015-01-0399
Alexander Jaust, Bastian Morcinkowski, Stefan Pischinger, Jens Ewald
In this work, a consistent transport and mixing model is derived and validated that calculates the same mixing in thermodynamic multi-zone space as in spacially resolved physical space. The transport and mixing 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
2015-01-0794
Zongyu Yue, Randy Hessel, Rolf Reitz
The application of close-coupled post injection in Diesel engine has been proved to be an effective in-cylinder strategy for soot reduction, without much fuel efficiency penalty. But due to the complex condition of in-cylinder combustion, the soot reduction mechanism of post-injection is difficult to be explained clearly and remains ambiguous. Here, a simulation study, using three dimensional computational fluid dynamics model, coupled with SpeedChem chemistry solver and semi-detailed soot model, is carried out to investigate post-injection in a constant volume combustion chamber model, which is more simple and controllable in respect to boundary conditions. A 2-D axisymmetric grid of radius of 2 cm and height of 5 cm is used to represent the geometric confine for spray from one nozzle in an optical engine. Post-injection duration, initial temperature, initial oxygen concentration is swept respectively to study efficacy of post-injection under different combustion condition.
2015-04-14
Technical Paper
2015-01-1526
Yasuyuki Onishi, Thomas Ramsay, Timothy Juan, James McKillen
A sports car exhibits many challenges from an aerodynamic point of view: drag that limits top speed, lift - or down force - and balance that affects handling, brake cooling and insuring that the heat exchangers have enough air flowing through them under several vehicle speeds and ambient conditions. All of which must be balanced with a sports car styling and esthetic. Since this sports car will apply two electric motors to drive front axle and a high-rev V6 turbo charged engine in series with a 9-speed double-clutch transmission to drive rear axle, additional cooling was required, yielding a total of ten air cooled heat exchangers. It is also a challenge to introduce cooling air into the rear engine room to protect the car under severe thermal conditions.
2015-04-14
Technical Paper
2015-01-1536
Brett C. Peters, Mesbah Uddin, Jeremy Bain, Alex Curley, Maxwell Henry
Currently, most computational fluid dynamic solvers rely heavily on the robustness of unstructured finite volume discretization to solve complex flows. 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 hand made structured meshes. By using overset grids and NASA's overset grid solver, OVERFLOW, structured finite difference solutions are easily achievable for complex geometries such as the DrivAer model. This allows for higher order flow structures to be captured as compared to traditional finite volume schemes. The current paper investigates flow field solutions computed with finite volume and finite difference methods for the DrivAer model.
2015-04-14
Technical Paper
2015-01-1540
Dirk Wieser, Henning Lang, Christian Nayeri, Christian Paschereit
The effect of an active flow control method is investigated on a 1:4 scale realistic vehicle model called “DrivAer” with notchback geometry. The wind tunnel experiments are conducted at a Reynolds number up to Re=3.0∙106and two yaw angles. Several fluidic oscillators are implemented at the c-pillars and at the upper rear window edge. The actuators which emit a high frequency sweeping jet are installed inside the model. The actuator spacing, the mass flow rate, and the position of actuation at the vehicle geometry are varied during the experiments. The effect of the active flow control on the car is measured with an external balance underneath the test section and an array of surface pressure taps distributed on the entire vehicle’s rear end section. Moreover, Particle Image Velocimetry measurements are performed in stream- and cross wise sections behind the car. The surface trace pattern with and without AFC are visualized with tufts and a sophisticated tuft processing program.
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