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Viewing 1 to 30 of 1883
2014-11-11
Technical Paper
2014-32-0006
Federico Brusiani, Gian Marco Bianchi, Cristian Catellani, Marco Ferrari, Paolo Verziagi, Dario Catanese
Abstract Still today, two-stroke engine layout is characterized by a wide share on the market thanks to its simpler construction that allows to reduce production and maintenance costs respecting the four-stroke engine. Two of the main application areas for the two-stroke engines are on small motorbikes and on handheld machines like chainsaws, brush cutters, and blowers. In both these application areas, two-stroke engines are generally equipped by a carburettor to provide the air/fuel mixture formation while the engine cooling is assured by forcing an air stream all around the engine head and cylinder surfaces. Focusing the attention on the two-stroke air-cooling system, it is not easy to assure its effectiveness all around the cylinder surface because the air flow easily separates from the cylinder walls producing local hot-spots on the cylinder itself. This problem can be bounded only by the optimization of the cylinder fin design placed externally to the cylinder surface. In the present paper the authors present a first analysis of the thermal-flow behaviour of a two stroke engine designed for brush-cutter machine applications.
2014-10-13
Technical Paper
2014-01-2556
Hiroshi Tashima, Daisuke Tsuru
Abstract The discrete multi-component model for residual heavy fuel oil (HFO), developed in the mid-2000s, proved to be a simple but practical approximation in reproduction of the combustion process of HFO sprays on a couple of CFD simulation codes. The model succeeded in providing qualitative explanation about the spray and flame progression of HFO inside constant-volume chambers (CVC), but its practical use is still underway because of its higher calculation costs. Two-component HFO model, which was introduced relatively recently, separates every spray droplet virtually into two smaller droplets of each component to calculate their evaporation process separately. The model showed good agreement with the observation results on the various HFO spray behaviors in some visualized CVCs (VCVCs). However, all the above examinations were done only qualitatively not quantitatively since the heat releases measured in the visualizing-oriented chambers of large internal volume were difficult to detect accurately.
2014-10-13
Technical Paper
2014-01-2578
Konrad Pietrykowski
Abstract The article presents the simulation results of the combustion process made based on a 3D-CFD mathematical model of the aircraft radial engine. The object of research was the 9-cylinder aircraft engine ASZ-62IR. The model comprised of the internal geometry of the cylinder and pipes in the cylinder head together with the inlet pipe. The model has been verified on the base of the pressure characteristics in the inlet pipe obtained from the experiment. In order to reproduce the same process of mixture formation as in the real engine, the model involved the process of induction, compression and combustion. The conducted research was aimed at verifying the influence of switching off one of the spark plugs on the combustion process. The simulation was done for three versions of ignition, for two spark plugs at the same time, only the front spark plug, only the rear spark plug. The research has been conducted in the conditions of maximum constant power of engine that is 686 kW. As a result of the conducted research, the reaction progress variables in the combustion chamber representing the spread of flame and rate of heat release have been obtained.
2014-10-13
Technical Paper
2014-01-2575
Michal Bialy, Miroslaw Wendeker, Pawel Magryta, Zbigniew Czyz, Rafal Sochaczewski
Abstract The article presents results of the 3D-CFD modeling of mixture creation process in the cylinder of diesel engine. The simulation was performed using the AVL Fire software. Based on the geometry of the ADCR engine, produced by Andoria-Mot Company, a 3D-CFD model of combustion chamber, channels in the engine head and CNG injector nozzle were created. This model prevented the simulation of the filling, compression and mixture creation process. Specially prepared CNG injector has been placed in the socket of the glow plug, to minimize interference with the structure of the engine. With this solution full functionality of the original fuel supply system was retained with the ability to work with one or two fuels. During studies the location of the gas injector nozzle was changed. The results of simulation are presented for three variants of CNG injector locations. Simulation studies prevented the determination of the degree of stratification and the distribution of fuel in the cylinder of the engine.
2014-10-13
Technical Paper
2014-01-2569
Fabrizio Bonatesta, Salvatore La Rocca, Edward Hopkins, Daniel Bell
Abstract Gasoline Direct Injection engines are efficient devices which are rivaling diesel engines with thermal efficiency approaching the 40% threshold at part load. Nevertheless, the GDI engine is an important source of dangerous ultra-fine particulate matter. The long-term sustainability of this technology strongly depends on further improvement of engine design and combustion process. This work presents the initial development of a full-cycle CFD model of a modern wall-guided GDI engine operated in homogeneous and stoichiometric mode. The investigation was carried out at part-load operating conditions, with early injections during the intake stroke. It included three engine speeds at fixed engine-equivalent load. The spray model was calibrated using test-bed and imaging data from the 7-point high-pressure fuel injectors used in the test engine. Experimental data on combustion were also used for calibration purposes, whereas measurements of engine-out soot number density from a Differential Mobility Spectrometer formed the basis and motive of the investigation.
2014-10-13
Technical Paper
2014-01-2586
Shui-chang Liu, Zheng-qi Gu, Li-fu Li, Yong Zhang, Wan-dong ZHAO
Abstract To shorten the development cycle and ensure the stability of the products, based on RNG k-e turbulence model and porous model, 3 dimension (3D) flow field Computational Fluid Dynamics (CFD) simulation is adopted to calculate the radiator group performance for a engineering vehicle being developed. Air-side flow field simulations of the radiator unit model are carried out firstly to obtain the radiators' air-side characteristics; then, the air flow and heat transfer in the whole air channel containing the radiator group are simulated simultaneously to get the inlet and outlet water temperatures of radiator group, at last, the real vehicle test is carried out to verify the simulation results. To be emphasized, in calculating the near-wall boundary layer of the radiators' unit model flow field, modified standard wall functions (MSWF) whose calculation grids is same to standard wall function (SWF) and computation accuracy of the near-wall first node velocity is higher than SWF is proposed; and compared to the test values, the radiators' inlet and outlet water temperatures obtained from the flow field simulation process using MSWF has relative error 6.4%, which can meet the accuracy requirement in engineering computation.
2014-10-13
Technical Paper
2014-01-2708
Antonino La Rocca, David MacMillan, Paul Shayler, Michael Murphy, Ian Pegg
Abstract Cold idle operation of a modern design light duty diesel engine and the effect of multiple pilot injections on stability were investigated. The investigation was initially carried out experimentally at 1000rpm and at −20°C. Benefits of mixture preparation were initially explored by a heat release analysis. Kiva 3v was then used to model the effect of multiple pilots on in-cylinder mixture distribution. A 60° sector of mesh was used taking advantage of rotational symmetry. The combustion system and injector arrangements mimic the HPCR diesel engine used in the experimental investigation. The CFD analysis covers evolutions from intake valve closing to start of combustion. The number of injections was varied from 1 to 4, but the total fuel injected was kept constant at 17mm3/stroke. Start of main injection timing was fixed at 7.5°BTDC. The experimental study shows that increasing the number of pilots improves stability and leads to fuel preparation resulting in higher initial peak rate of heat release.
2014-10-13
Technical Paper
2014-01-2737
Daliang Jing, Hongming Xu, Shi-jin Shuai, Zhi Wang, Yanfei Li
Abstract Fuel spray atomization process is known to play a key role in affecting mixture formation, combustion efficiency and soot emissions in direct injection engines. The fuel spray Computational Fluid Dynamics (CFD) modeling technology can be an effective means to study and predict spray characteristics such as penetration, droplet size and droplet velocity, 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. Different approaches and various models based on aerodynamically induced breakup mechanism have been implemented to simulate spray atomization process in earlier studies, and the effects of turbulence and cavitation from the injector nozzle is recently being concerned increasingly by engine researchers. In this study, an enhanced turbulence and cavitation induced primary breakup model combining aerodynamic breakup mechanism is developed.
2014-10-13
Technical Paper
2014-01-2818
Mohammad Reza Hamedi, Athanasios Tsolakis, Jose Martin Herreros
Abstract Recent developments in diesel engines lead to increased fuel efficiency and reduced exhaust gas temperature. Therefore more energy efficient aftertreatment systems are required to comply with tight emission regulations. In this study, a computational fluid dynamics package was used to investigate the thermal behaviour of a diesel aftertreatment system. A parametric study was carried out to identify the most influential pipework material and insulation characteristics in terms of thermal performance. In the case of the aftertreatment pipework and canning material effect, an array of different potential materials was selected and their effects on the emission conversion efficiency of a Diesel Oxidation Catalyst (DOC) were numerically investigated over a driving cycle. Results indicate that although the pipework material's volumetric heat capacity was decreased by a factor of four, the total emission reduction was only considerable during the cold start. Different insulation strategies (e.g. double layer pipe with air gap and vacuum) were simulated using CFD and the improvement in the DOC emission conversion was monitored over the New European Driving Cycle (NEDC).
2014-10-13
Technical Paper
2014-01-2639
Ken Naitoh, Kenya Hasegawa, Tomoaki Kubota, Taiki Hashimoto, Yoshiyuki Nojima, Masato Tanaka, Kentaro Kojima
In our previous reports based on computational experiments and fluid dynamic theory, we proposed a new compressive combustion principle for an inexpensive, lightweight, and relatively quiet engine reactor that has the potential to achieve incredible thermal efficiency over 60% even for small combustion chambers having less than 100 cc. This level of efficiency can be achieved with colliding supermulti-jets that create complete air insulation to encase burned gas around the chamber center, thereby avoiding contact with the chamber walls, including the piston. We originally developed an actual prototype engine system for gasoline. The engine has a strongly-asymmetric double piston and the supermulti-jets colliding with pulse, although there are no poppet valves. The number of jets pulsed for intake and exhaust is eight, while both of bore and stroke are about 40mm. The present prototype engine can widely vary point-compression strength due to the supermulti-jets and mechanical homogeneous compression level, by changing the phase of two gears and size ratio of two gears between the double piston.
2014-10-13
Technical Paper
2014-01-2883
Lukasz Grabowski, Zbigniew Czyz, Krzysztof Kruszczynski
Abstract This paper focuses on the issues concerning gyroplane powertrain cooling. The Rotax 912S engine was selected as a propulsion system following a detailed analysis. A one-dimensional model, simulated with the AVL Boost software, was applied to determine the heat balance of the engine and the heat flux penetrating through each of engine's surfaces. The geometrical quantities defined in the model were obtained by measuring a three-dimensional geometry provided by an authorized Rotax engine supplier company. Calculation results were then verified by comparing the obtained values with data available from the Rotax 912S engine and with the values of individual parameters given in the literature. The CFD simulation studies, performed with Ansys Fluent, enabled to determine the required airflow capable of absorbing up to 6 kW of heat, the properties for sufficient cooling of the cylinders in the gyroplane powertrain system and the manner of directing the air flow in order to achieve the smallest possible temperature gradient.
2014-10-13
Technical Paper
2014-01-2567
Akira Kikusato, Kazuya Kogo, Beini Zhou, Kusaka Jin, Yasuhiro Daisho, Kiyotaka Sato, Hidefumi Fujimoto, Hiroshi Terashima, Youhi Morii
Abstract The objective of the present study is to analyze soot formation in diesel engine combustion by using multi-dimensional combustion simulations with a parallelized explicit ODE solver. Parallelized CHEMEQ2 was used to perform detailed chemical kinetics in KIVA-4 code. CHEMEQ2 is an explicit stiff ODE solver developed by Mott et al. which is known to be faster than traditional implicit ODE solvers, e.g., DVODE. In the present study, about eight times faster computation was achieved with CHEMEQ2 compared to DVODE when using a single thread. Further, by parallelizing CHEMEQ2 using OpenMP, the simulations could be run not only on calculation servers but also on desktop machines. The computation time decreases with the number of threads used. The parallelized CHEMEQ2 enabled combustion and emission characteristics, including detailed soot formation processes, to be predicted using KIVA-4 code with detailed chemical kinetics without the need for reducing the reaction mechanism. After validating the code, diesel engine combustion was simulated to investigate combustion and emission characteristics, focusing on soot formation, growth and oxidation at different EGR ratios.
2014-10-13
Technical Paper
2014-01-2587
Yufeng Li
Swirl ratio in the cylinder of a diesel engine is an important parameter for air/fuel mixing and combustion process. The swirl intensity generated by an intake port is measured on a steady flow rig. The swirl ratio at the end of intake process in the engine is then estimated from the steady flow test results by equations which have already been established by Ricardo and AVL. However, the existing equations are deduced from a series of assumptions. Three of them affect swirl ratio estimation significantly: a) volumetric efficiency of an engine is 100%; b) the pressure drop through the intake ports is constant during the intake process in engine operation; c) no burned gas residual is trapped in the cylinder. An accurate estimation of swirl ratio is essential during the engine combustion system development. In this paper, the authors proposed a new estimation equation of swirl ratio, in which the volumetric efficiency, the compression ratio and the pressure drop through the intake ports are three additional variables.
2014-10-13
Technical Paper
2014-01-2576
Hiew Mun Poon, Hoon Kiat Ng, Suyin Gan, Kar Mun Pang, Jesper Schramm
This work is an extension to a previously reported work on chemical kinetic mechanism reduction scheme for large-scale mechanisms. Here, Perfectly Stirred Reactor (PSR) was added as a criterion of data source for mechanism reduction instead of using only auto-ignition condition. As a result, a reduced n-hexadecane mechanism with 79 species for diesel fuel surrogate was successfully derived from the detailed mechanism. Following that, the reduced n-hexadecane mechanism was validated under auto-ignition and PSR conditions using zero-dimensional (0-D) closed homogeneous batch reactor in CHEMKIN-PRO software. Agreement was achieved between the reduced and detailed mechanisms in ignition timing predictions and the reduced n-hexadecane mechanism was able to reproduce species concentration profiles with a maximum error of 40%. Accordingly, two-dimensional (2-D) Computational Fluid Dynamic (CFD) simulations were performed to study the spray combustion phenomena within a constant volume bomb. Both non-reacting and reacting conditions were applied in this study.
2014-10-13
Technical Paper
2014-01-2570
Karthik Puduppakkam, Chitralkumar Naik, Ellen Meeks, Christian Krenn, Roswitha Kroiss, Johannes Gelbmann, Guenther Pessl
Abstract An important goal for CFD simulation in engine design is to be able to predict the combustion behavior as operating conditions are varied and as hardware is modified. Such predictive capability allows virtual prototyping and optimization of design parameters. For low-temperature combustion conditions, such as with high rates of exhaust-gas recirculation, reliable and accurate predictions have been elusive. Soot has been particularly difficult to predict, due to the dependence of soot formation on the fuel composition and the kinetics detail of the fuel combustion. Soot evolution in diesel engines is impacted by fuel and chemistry effects, as well as by spray dynamics and turbulence. In this work, we present a systematic approach to accurately simulate combustion and emissions in a high-performance BMW diesel engine. This approach has been tested and validated against experimental data for a wide range of operating conditions. Nine operating conditions have been modeled that span engine loads of 3-21 bar MEP, engine speeds of 1000-4400 rpm and external EGR of 0-38%.
2014-10-13
Technical Paper
2014-01-2850
Yingyi Wen, Shunichi Oshima
Agitation torque associated with oil lubricant is one important factor of torque loss in bearings under sufficient lubricating conditions. So far, efforts on reducing agitation torque were taken mostly by means of conventional experimental trials. Aiming for speedy, low-cost development, a calculation program for predicting the amount of agitation torque and oil distribution tendency in rolling bearings has been developed using computational fluid dynamics (CFD) analysis. At first, since rolling bearings are axially symmetric, sector models of bearings were adopted. To verify the method, torque losses and oil quantities in ordinary-sized bearings have been measured. Calculated values based on sector models are qualitatively in good agreement with measured results. The difference between the absolute values of measured and calculated torque may be caused by the difference between the vertical model used in CFD analysis and the horizontal torque-testing rig used in measurement. To improve the accuracy, full models of the bearings have been developed and verified by experiment.
2014-10-13
Technical Paper
2014-01-2588
Sophie Porter, Ahmad Kamal Mat Yamin, Svetlana Aleksandrova, Stephen Benjamin, Carol A. Roberts, Jonathan Saul
Abstract Flow maldistribution across automotive exhaust catalysts significantly affects their conversion efficiency. Flow behaviour can be predicted using computational fluid dynamics (CFD). This study investigates the application of CFD to modelling flow in a 2D system consisting of a catalyst monolith downstream of a wide-angled planar diffuser presented with steady flow. Two distinct approaches, porous medium and individual channels, are used to model monoliths of length 27 mm and 100 mm. Flow predictions are compared to particle image velocimetry (PIV) measurements made in the diffuser and hot wire anemometry (HWA) data taken downstream of the monolith. Both simulations compare favourably with PIV measurements, although the models underestimate the degree of mixing in the shear layer at the periphery of the emerging jet. Tangential velocities are predicted well in the central jet region but are overestimated elsewhere, especially at the closest measured distance, 2.5 mm from the monolith.
2014-10-13
Technical Paper
2014-01-2819
S. F. Benjamin, C. A. Roberts
Abstract In an attempt to reduce particulate and NOx emissions from Diesel exhaust, the combined DPF and SCR filter is now frequently chosen as the preferred catalyst. When this device functions effectively it saves valuable packaging space in a passenger vehicle. As part of its development, modelling of its emissions performance is essential. Single channel modelling would seem to be the obvious choice for an SCRF because of its complex internal geometry. This, however, can be computationally demanding if modelling the full monolith. For a normal flow-through catalyst monolith the porous medium approach is an attractive alternative as it accounts for non-uniform inlet conditions without the need to model every channel. This paper attempts to model an SCRF by applying the porous medium approach. The model is essentially 1D but as with all porous medium models, can very easily be applied to 3D cases once developed and validated. The model is described in full in this paper and values for all the key parameters are presented.
2014-10-13
Technical Paper
2014-01-2864
Daniela Siano, Fabio Bozza, Luigi Teodosio, Vincenzo De Bellis
This paper reports 1D and 3D CFD analyses aiming to improve the gas-dynamic noise emission of a downsized turbocharged VVA engine through the re-design of the intake air-box device, consisting in the introduction of external or internal resonators. Nowadays, modern spark-ignition (SI) engines show more and more complex architectures that, while improving the brake specific fuel consumption (BSFC), may be responsible for the increased noise radiation at the engine intake mouth. In particular VVA systems allow for the actuation of advanced valve strategies that provide a reduction in the BSFC at part load operations thanks to the intake line de-throttling. In these conditions, due to a less effective attenuation of the pressure waves that travel along the intake system, VVA engines produce higher gas-dynamic noise levels. The worsening of the engine gas-dynamic performance can be compensated with a partial re-design of the air-box device, without significantly penalizing the engine power output.
2014-10-13
Technical Paper
2014-01-2884
Konrad Pietrykowski, Tytus Tulwin
The article presents convective heat transfer phenomenon by analytically and empirically taken data and CFD based model analysis. 1000 hp ASz-62IR aircraft radial engine is the object of research. This engine is being continuously operated on M18 Dromader and AN-2 aircraft. To recount heat oriented phenomena a three-dimensional CFD model was developed that accounts circumfluent flow around cylinder and cylinder head engine surfaces. The geometry includes M18 Dromader frontal airframe elements to account their influence on cooling air flow. The simulation has been conducted as a steady-state flow. Geometry and setup specific swirls and backflows were observed that increase cylinder and cylinder head rear side heat transfer coefficients. Flow along cooling fins was analysed, connecting their heat transfer coefficient dependency. Results show that local air velocity has big influence on heat flux passed by fin walls. Additionally fin performance has been calculated in means of effectiveness and efficiency.
2014-10-01
Technical Paper
2014-01-9051
Jun Ma, Hua Zhao, Paul Freeland, Martyn Hawley, Jun Xia
In order to optimize the 2-stroke uniflow engine performance on vehicle applications, numerical analysis has been introduced, 3D CFD model has been built for the optimization of intake charge organization. The scavenging process was investigated and the intake port design details were improved. Then the output data from 3D CFD calculation were applied to a 1D engine model to process the analysis on engine performance. The boost system optimization of the engine has been carried out also. Furthermore, a vehicle model was also set up to investigate the engine in-vehicle performance.
2014-09-30
Technical Paper
2014-01-2444
Shaoyun Sun, Yin-ping Chang, Xinyu Wang, Qiang Fu, Kelong Lu, Zuofeng Pan, Bo Li, Heinz Friz
Abstract A challenge for the aerodynamic optimization of trucks is the limited availability of wind tunnels for testing full scale trucks. FAW wants to introduce a development process which is mainly based on CFD simulation in combination with some limited amount of wind tunnel testing. While maturity of CFD simulation for truck aerodynamics has been demonstrated in recent years, a complete validation is still required before committing to a particular process. A 70% scale model is built for testing in the Shanghai Automotive Wind Tunnel Center (SAWTC). Drag and surface pressures are measured for providing a good basis for comparison to the simulation results. The simulations are performed for the truck in the open road driving condition as well as in an initial digital model of the aerodynamic wind tunnel of SAWTC. A full size truck is also simulated in the open road driving condition to understand the scaling effect. As a 70% scale model of a heavy truck is seen to be close to the limits of the SAWTC wind tunnel, an attempt is made to understand possible wind tunnel effects by including an approximate geometry of the wind tunnel in the simulations of the scale model.
2014-09-30
Technical Paper
2014-01-2442
Michael S. Barton, David Corson, John Quigley, Babak Emami, Tanuj Kush
Abstract In this work, the multi-disciplinary problem arising from fluid sloshing within a partially filled tanker truck undergoing lateral acceleration is investigated through the use of multiphysics coupling between a computational fluid dynamics (CFD) solver and a multi-body dynamics (MBD) solver. This application represents a challenging test case for simulation technology within the design of commercial vehicles and is intended to demonstrate a novel approach in the field of computer aided engineering. Computer aided engineering is playing a more predominant role in the design process for commercial and passenger vehicles. Better understanding of the real time loading and responses on a vehicle during intended or unintended use can result in improved design and reduced cost over traditional designs that relied heavily on assumed loads. Liquid sloshing within the cargo tank of a commercial tanker truck results in increased loading on the vehicle's suspension when undergoing acceleration maneuvers.
2014-09-30
Technical Paper
2014-01-2440
Ashok Patidar, Shivdayal Prasad, Umashanker Gupta, Mohan Subbarao
Abstract In today's competitive world, vehicle with light weighting is the most focused area. Vehicle light weighting can be done either by using light weight materials or by reducing the size of the existing components. In present paper later approach of vehicle light weighting is followed. It will help in design lay outing and reduce weight will add benefit to Fuel Efficiency (FE) too. Scope for light weighting is identified in exhaust system where muffler volume is optimized using Computational Fluid Dynamics (CFD) commercial tool FLUENT™. The back pressure, exhaust gas temperature, sound noise level & sound quality are chosen as design verification parameters. The muffler volume is reduced by 14.1%; resultant system become 14.1% compact with 2% lighter weight. Initially CFD analysis is performed on existing muffler and correlated with available test results. Accordingly parameters like pressure drop and flow induced noise are set as target values for new design. Same CFD analysis process is used to find the optimum solution among the series of options available.
2014-09-30
Technical Paper
2014-01-2437
Haoting Wang, Tieping Lin, Xiayi Yuan, Qi Zhang
Abstract Three dimensional, steady state computational fluid dynamics (CFD) simulations of flow around a generic pickup truck are performed to optimize the aerodynamic performance of a pickup truck model. Detailed comparison between the data of the CFD model and the experiment are made. By using deformation techniques, surrogate models and optimization methods, the drag is reduced. Four design variables are used for deformation: the cabin height, bed height, ground clearance and bed length. The optimization is single objective: minimizing the drag coefficient. A response surface model is built to reduce the sampling points for optimization, and the simulation time is reduced accordingly. Results show that the design variables are not fully independent with each other, and by proper combinations of the variable change, the drag coefficient of the pickup truck model can be reduced effectively. In this study, the drag coefficient reduced about 9.7% through optimization algorithm. The results also show that the single tailgate itself is not always profitable for drag reduction.
2014-09-30
Technical Paper
2014-01-2344
Peter Gullberg, Antoine Tavernier
Abstract Computational Fluid Dynamics (CFD) is today an important tool in the design process of fuel and energy efficient vehicles. Under-hood management is one of the fields where CFD has proven itself to be useful for cost-efficient development of products. Multiple Reference Frame (MRF) method is the most common used tool in the industry for modeling rotating parts. In previous papers, the modeling strategy with MRF has been documented for open fans and showed high capability to predict fan performance. One of the open points of this proposed method has been its applicability to closed fans (ring fans), as industry experience and discussions has indicated previous conclusions of open fans and MRF modeling may not apply across ranges of fan designs. This paper investigates the MRF method for a closed fan with U-shroud and analyzes several aspect of the modeling strategy. The finding of this paper is that the MRF method predicts fan performance for closed fans with equal accuracy as it does for open fans.
2014-09-30
Technical Paper
2014-01-2443
Helena Martini, Peter Gullberg, Lennart Lofdahl
Abstract Nowadays, much focus for vehicle manufacturers is directed towards improving the energy efficiency of their products. The aerodynamic drag constitutes one major part of the total driving resistance for a vehicle travelling at higher speeds. In fact, above approximately 80km/h the aerodynamic drag is the dominating resistance acting on a truck. Hence the importance of reducing this resistance is apparent. Cooling drag is one part of the total aerodynamic drag, which arises from air flowing through the heat exchangers, and the irregular under-hood area. When using Computational Fluid Dynamics (CFD) in the development process it is of great importance to ensure that the methods used are accurately capturing the physics of the flow. This paper deals with comparative studies between CFD and wind-tunnel tests. In this paper, two comparative studies are presented. One is a comparison between cooling performance simulations and chassis dynamometer measurements; the other study is a comparison between external aerodynamics simulations and wind-tunnel measurements.
2014-09-30
Technical Paper
2014-01-2436
Jeff Smith, Rick Mihelic, Brandon Gifford, Matthew Ellis
Abstract On-highway tractor-trailer vehicles operate in a complex aerodynamic environment that includes influences of surrounding vehicles. Typical aerodynamic analyses and testing of single vehicles on test track, in wind tunnel or in computational fluid dynamics (CFD) do not account for these real world effects. However, it is possible with simulation and on-road testing to evaluate these aerodynamic interactions. CFD and physical testing of multiple vehicle interactions show that traffic interactions can impact the overall drag of leading and trailing vehicles. This paper will discuss results found in evaluating the effects of separation distances on tractor-trailer aerodynamics in on-road and CFD evaluations using a time-accurate Lattice Boltzmann Method based approach and the ramifications for improving real world prediction versus controlled single vehicle testing.
2014-09-30
Technical Paper
2014-01-2346
Manoj K. Sampath, Figen Lacin
Abstract The Diesel engine combustion process results in harmful exhaust emissions, mainly composed of Particulate Matter (PM), Hydro Carbon (HC), Carbon monoxide (CO) and Nitrogen Oxides (NOx). Several technologies have been developed in the past decades to control these diesel emissions. One of the promising and well matured technology of reducing NOx is to implement Selective Catalytic Reduction (SCR) using ammonia (NH3) as the reducing agent. For an effective SCR system, the aqueous urea solutions should be fully decomposed into ammonia and it should be well distributed across the SCR. In the catalyst, all the ammonia is utilized for NOx reduction process. In the design stage, it is more viable to implement Computational Fluid Dynamics (CFD) for design iterations to determine an optimized SCR system based on SCR flow distribution. And in later stage, experimental test is required to predict the after-treatment system performance based on NOx reduction. The SCR model predicts the NH3 formation from urea decomposition and it is quantified at the SCR inlet, whereas experimental data involves the NOx reduction process.
2014-09-30
Technical Paper
2014-01-2351
Meng-Huang Lu, Figen Lacin, Daniel McAninch, Frank Yang
Abstract Diesel exhaust aftertreatment solutions using injection, such as urea-based SCR and lean NOx trap systems, effectively reduce the emission NOx level in various light vehicles, commercial vehicles, and industrial applications. The performance of the injector plays an important role in successfully utilizing this type of technology, and the CFD tool provides not only a time and cost-saving, but also a reliable solution for extensively design iterations for optimizing the injector internal nozzle flow design. Inspired by this fact, a virtual test methodology on injector dosing rate utilizing CFD was proposed for the design process of injector internal nozzle flows. For a low-pressure (less than 6 bar) injector application, the characteristic Reynolds number based on the diameter and mass flow rate of the inlet, return flow outlet, and nozzle exit of the injector might range from 2000 to 20000, therefore, employing a flow-physics based viscous model for building up a virtual test methodology is critical to properly capture the fluid dynamics of injector internal nozzle flow.
Viewing 1 to 30 of 1883

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