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Viewing 1 to 30 of 2233
2010-09-28
Technical Paper
2010-32-0078
Taib Iskandar Mohamad, Ali Yusoff, Shahrir Abdullah, Mark Jermy, Matthew Harrison, How Heoy Geok
Compressed natural gas (CNG) has been widely used as alternatives to gasoline and diesel in automotive engines. It is a very promising alternative fuel due to many reasons including adaptability to those engines, low in cost, and low emission levels. Unfortunately, when converting to CNG, engines usually suffer from reduced power and limited engine speed. These are due to volumetric loss and slower flame speed. Direct injection (DI) can mitigate these problems by injecting CNG after the intake valve closes, thus increasing volumetric efficiency. In addition, the high pressure gas jet can enhance the turbulence in the cylinder which is beneficial to the mixing and burning. However, conversion to direct fuel injection (DFI) requires a costly modification to the cylinder head to accommodate the direct injector and also can involve piston crown adjustment. This paper discusses a new alternative to converting to DFI using a device called Spark Plug Fuel Injector (SPFI).
2010-09-28
Technical Paper
2010-32-0069
Gustavo Fontana, Fabio Bozza, Enzo Galloni, Daniela Siano
In this paper, an experimental and numerical analysis of combustion process and knock occurrence in a small displacement spark-ignition engine is presented. A wide experimental campaign is preliminarily carried out in order to fully characterize the engine behavior in different operating conditions. In particular, the acquisition of a large number of consecutive pressure cycle is realized to analyze the Cyclic Variability (CV) effects in terms of Indicated Mean Effective Pressure (IMEP) Coefficient of Variation (CoV). The spark advance is also changed up to incipient knocking conditions, basing on a proper definition of a knock index. The latter is estimated through the decomposition and the FFT analysis of the instantaneous pressure cycles. Contemporary, a quasi-dimensional combustion and knock model, included within a whole engine one-dimensional (1D) modeling framework, are developed. Combustion and knock models are extended to include the CV effects, too.
2010-10-05
Technical Paper
2010-01-2041
Bernard J. Simon
The transition towards a ‘Green Economy’ puts pressure on automakers to improve the fuel economy of their vehicles. Fuel economy is complicated vehicle attribute impacted by a large number of factors, not limited to vehicle weight, rolling resistance, aerodynamic drag, engine efficiency, drive train losses, accessory loading, and performance targets embodied in the controls strategy. Due to the number and complexity of contributing factors, fuel economy benchmarking, target setting and technology evaluation can be difficult. This paper introduces two new vehicle attributes: miles per kilowatt-hour (mpk) and kilowatt-hours per gallon (kpg) which, when multiplied together, calculate mpg. These parameters are derived from emissions and fuel economy certification data posted by the EPA on their website. This paper then shows how these parameters can be used to characterize and benchmark vehicles, set targets for new vehicles, and project future technology trends.
2010-10-25
Technical Paper
2010-01-2151
Atsushi Matsumoto, Yi Zheng, Xing-Bin Xie, Ming-Chia Lai, Wayne Moore
Because of their robustness and cost performance, multi-hole gasoline injectors are being adopted as the direct injection (DI) fuel injector of choice as vehicle manufacturers look for ways to reduce fuel consumption without sacrificing power and emission performance. To realize the full benefits of direct injection, the resulting spray needs to be well targeted, atomized, and appropriately mixed with charge air for the desirable fuel vapor concentration distributions in the combustion chamber. Ethanol and ethanol-gasoline blends synergistically improve the turbo-charged DI gasoline performance, especially in down-sized, down-sped and variable-valve-train engine architecture. This paper presents the spray imaging results from two multi-hole DI gasoline injectors with different design, fueled with pure ethanol (E100) or gasoline (E0), under homogeneous and stratified-charge conditions that represent typical engine operating points.
2010-10-25
Technical Paper
2010-01-2238
Yongli Qi, Hao Liu, Kenneth Midkiff, Paulius Puzinauskas
Today's engine and combustion process development is closely related to the intake port layout. Combustion, performance and emissions are coupled to the intensity of turbulence, the quality of mixture formation and the distribution of residual gas, all of which depend on the in-cylinder charge motion, which is mainly determined by the intake port and cylinder head design. Additionally, an increasing level of volumetric efficiency is demanded for a high power output. Most optimization efforts on typical homogeneous charge spark ignition (HCSI) engines have been at low loads because that is all that is required for a vehicle to make it through the FTP cycle. However, due to pumping losses, this is where such engines are least efficient, so it would be good to find strategies to allow the engine to operate at higher loads.
2010-10-25
Technical Paper
2010-01-2239
Yongli Qi, Hao Liu, Kenneth Midkiff, Paulius Puzinauskas
Hybrid vehicle engines modified for high exhaust gas recirculation (EGR) are a good choice for high efficiency and low NOx emissions. Such operation can result in an HEV when a downsized engine is used at high load for a large fraction of its run time to recharge the battery or provide acceleration assist. 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. It is accepted that the detailed experimental characterization of flow field near top dead center (TDC) in an engine environment is no longer practical and cost effective.
2010-04-12
Technical Paper
2010-01-0540
Pouria Mehrani, Harry C. Watson
Cyclic variability in spark ignition engine combustion, especially at high dilution through lean burn or high EGR rates, places limits on in-cylinder NOx reduction and thermal efficiency. Flame wrinkling, resulting from interactions with turbulence, is a potential source of cyclic variations in turbulence. Previous studies have shown that flame kernels are subject to significant distortions when they are smaller than the integral length scale of turbulence. With the assumption that flame development is not subject to noticeable variations, after it reaches the integral length scale, the authors have shown that turbulent-burning-caused combustion variability can be successfully modeled as a function of laminar flame speed and turbulence intensity. This paper explores the contributions of flame wrinkling to flame kernel growth variation. As the kernel growth problem is complex, this study only explores one of the many aspects of the problem.
2010-04-12
Technical Paper
2010-01-0544
Kentaro Watanabe, Shingo Ito, Tadashi Tsurushima
Gasoline engines employ various mechanisms for improvement of fuel consumption and reduction of exhaust emissions to deal with environmental problems. Direct fuel injection is one such technology. This paper presents a new quasi-dimensional combustion model applicable to direct injection gasoline engine. The Model consists of author's original in-cylinder turbulence and mixture homogeneity sub model suitable for direct fuel injection conditions. Model validation results exhibit good agreement with experimental and 3D CFD data at steady state and transient operating conditions.
2011-04-12
Technical Paper
2011-01-0390
Naoki Kurimoto, Masayuki Suzuki, Mutsumi Yoshino, Yoshiaki Nishijima
A response surface model of a diesel spray, parameterized by the internal geometries of a nozzle, is established in order to design the nozzle geometries optimally for spray mixing. The explanatory variables are the number of holes, the hole diameter, the inclined angle, the hole length, the hole inlet radius, K-factor and the sac diameter. The model is defined as a full second-order polynomial model including all the first-order interactions of the variables, and a total of 40 sets of numerical simulations based on D-optimal design are carried out to calculate the partial regression coefficients. Partial regression coefficients that deteriorate the estimate accuracy are eliminated by a validation process, so that the estimate accuracy is improved to be ±3% and ±15% for the spray penetration and the spread, respectively. Then, the model is applied to an optimization of the internal geometries for the spray penetration and the spray spread through a multi-objective genetic algorism.
2011-04-12
Technical Paper
2011-01-0675
Riccardo Scarcelli, Thomas Wallner, Nicholas Matthias, Victor Salazar, Sebastian Kaiser
This paper performs a parametric analysis of the influence of numerical grid resolution and turbulence model on jet penetration and mixture formation in a DI-H2 ICE. The cylinder geometry is typical of passenger-car sized spark-ignited engines, with a centrally located single-hole injector nozzle. The simulation includes the intake and exhaust port geometry, in order to account for the actual flow field within the cylinder when injection of hydrogen starts. A reduced geometry is then used to focus on the mixture formation process. The numerically predicted hydrogen mole-fraction fields are compared to experimental data from quantitative laser-based imaging in a corresponding optically accessible engine. In general, the results show that with proper mesh and turbulence settings, remarkable agreement between numerical and experimental data in terms of fuel jet evolution and mixture formation can be achieved.
2011-04-12
Technical Paper
2011-01-0676
Fuming Xiao, Ghazi A. Karim
The dual-fuel engine represents in principle a simple flexible approach to employing gaseous fuels in conventional diesel engines. Compared to the use of hydrogen in spark ignition engines, there is relatively limited information about its effect when present as a supplementary fuel in suitably modified conventional compression ignition engines. This is especially for engines of the IDI type and when employing only low concentrations of hydrogen in the intake air while retaining the injection of large diesel fuel quantities. In the present contribution, a 3D-CFD model based on KIVA 3, developed with a “reduced” detailed chemical kinetics of 294 elementary reaction steps with 79 chemical species for diesel fuel combustion which includes 20 steps for the oxidation of hydrogen, is outlined.
2011-04-12
Journal Article
2011-01-0681
Ming-Chia Lai, Yi Zheng, Xing-Bin Xie, Seoksu Moon, Zunping Liu, Jian Gao, Xusheng Zhang, Kamel Fezzaa, Jin Wang, Junmei Shi
It is well know that the internal flow field and nozzle geometry affected the spray behavior, but without high-speed microscopic visualization, it is difficult to characterize the spray structure in details. Single-hole diesel injectors have been used in fundamental spray research, while most direct-injection engines use multi-hole nozzle to tailor to the combustion chamber geometry. Recent engine trends also use smaller orifice and higher injection pressure. This paper discussed the quasi-steady near-nozzle diesel spray structures of an axisymmetric single-hole nozzle and a symmetric two-hole nozzle configuration, with a nominal nozzle size of 130 μm, and an attempt to correlate the observed structure to the internal flow structure using computational fluid dynamic (CFD) simulation. The test conditions include variation of injection pressure from 30 to 100 MPa, using both diesel and biodiesel fuels, under atmospheric condition.
2010-10-10
Technical Paper
2010-01-1690
Alan Backstrom
This study continues work from SAE Technical Papers 2008-01-2543 and 2009-01-3044 that demonstrated a laboratory technique for evaluating brakes-off wear and DTV generation. The present study includes 60 brakes-off dynamometer tests and compares the performance of three caliper designs that are Standard (current production), Standard + Increased piston retraction and Standard + Pad abutment shim spreader springs. In addition, the effect of applying double sided adhesive strips to the pad back plates on brake drag is reported.
2010-10-10
Technical Paper
2010-01-1706
Cengiz R. Shevket, Luca Ciulla, Paolo Re
This paper outlines the technical challenges experienced and engineering methods used to overcome them during the endeavor to reduce wheel hub units mass and friction. Results achieved by the project team are significant and have meaningful contributions both to the unsprung mass, inertia and rolling resistance reduction. These features directly enable fuel consumption reduction and related CO2 emissions as well as positively influencing vehicle dynamics. The two part paper handles the subjects of weight reduction and drag related power loss improvement and their combined effect at vehicle level. It provides both simulated and test measured data as well as the validation of various features. This first part will focus on the friction reduction with only an introductory mention on the weight reduction effort. In the very near future every milligram of CO2 reduction will count.
2010-04-12
Journal Article
2010-01-0513
Kenichi Ando, Akio Takamura, Isao Saito
Optimization methodology employing CFD for the aerodynamic design of automotive car styling is presented. The optimization process consists of three stages: Design of Experiments (DOE), Response Surface Modeling (RSM), and optimization algorithm execution. RSM requires a number of CFD calculations in order to ensure its accuracy, making it difficult to apply the RSM to aerodynamic design optimization. In order to resolve this issue, Adaptive Multi Stage RSM (AMS-RSM) was conceived. This method provided the response surface its required accuracy and robustness. The optimization process was realized by constructing an automatic optimization system consisting of software.
2010-04-12
Technical Paper
2010-01-0512
Y.A. Irving Brown, S. Windsor, A.P. Gaylard
Two methods of passive flow control were investigated to determine their effectiveness in reducing aerodynamic drag on large Sports Utility Vehicles (SUVs). Passive means of flow control were selected since all active methods require the input of additional energy (e.g., pressurized fluids or electrical energy). The selected methods were base bleed and the use of a rear cavity, and various combinations of these were experimentally tested in full-scale wind tunnels with and without a moving belt/rotating wheel assembly. Aerodynamic drag reduction was accomplished by restructuring the low-pressure wake directly behind the vehicle. External cavity depths ranging from d/h=0.17 to 0.83 were used, while body cavity depths ranged from d/h=0 to 0.83, where the depth of the cavity d is non-dimensionalized by the height h of the base area.
2010-04-12
Technical Paper
2010-01-0511
Taeyoung Han, Youngtae Kim
Aerodynamic forces are the result of various complex viscous flow phenomena such as three-dimensional turbulent boundary layer on the body surfaces, longitudinal vortices induced by three-dimensional boundary layer separation, and high turbulence caused by flow separations. Understanding the flow characteristics and, especially, how the aerodynamic forces are influenced by the changes in the vehicle body shape, are very important in order to improve vehicle aerodynamics (particularly for low drag shapes). The present study was an attempt to provide insights for better understanding of the complex three-dimensional flow field around a vehicle by observing the limiting surface streamlines and the surface pressure gradients in the stream-wise and the transverse directions. The main objective of this work is to provide a comprehensive diagnostic analysis of the basic flow features in order to learn more about the flow separations in three-dimensions.
2010-04-12
Technical Paper
2010-01-0510
Rob Littlewood, Martin Passmore
A large contribution to the aerodynamic drag of a vehicle is the loss of pressure in the wake region, especially on square-back configurations. Wake pressure recovery can be achieved by a variety of physical shape changes, but with vehicle shapes becoming ever more aerodynamically efficient research into active technologies for flow manipulation is becoming more prominent. The aim of the current paper is to generate an understanding of how an optimized roof trailing edge, in the form of a chamfer, can reduce wake size, increase base pressures and reduce drag. A comprehensive study using PIV (Particle Image Velocimetry), balance measurements and static pressure measurements was performed in order to investigate the flow and wake structure behind a simplified car model. Significant reductions in C d are demonstrated and directly related to the measured base and slant pressures.
2010-04-12
Technical Paper
2010-01-0625
Yuxin Zhang, Jaal Ghandhi, Benjamin Petersen, Christopher Rutland
A novel algebraic similarity model for subgrid scalar dissipation rate has been developed as part of the Large Eddy Simulation (LES) package KIVA3V-LES for diesel engine study. The model is proposed from an a priori study using Direct Numerical Simulation (DNS) of forced isotropic turbulence. In the a posteriori test, fully resolved turbulent passive scalar field measurements are used to validate the model in actual engine flows. For reason of the length limit by SAE and the specific interest in engine applications, only a prior test and a posteriori test in engine flows are included in this paper. A posteriori tests in isotropic cube flow, turbulent round jet and flame cases will be presented in separate papers. An engine LES simulation of multi consecutive cycles was performed in this study.
2010-04-12
Technical Paper
2010-01-0624
Eero Antila, Matteo Imperato, Ossi Kaario, Martti Larmi
Two different medium-speed diesel engine cylinder head designs have been studied. The focus of the study has been the effect of intake channel design in the in-cylinder flow. The study has been carried out by CFD. The first cylinder head is a standard Wärtsilä 20 cylinder head and the second one is a specially designed head for a single cylinder research engine, called Extreme Value Engine (EVE). The CFD boundary conditions have been simulated by the help of a 1-d simulation code. In the full load cases the maximum cylinder pressure was 300 bar. Simulations have been done at lower load level too. One simulation with the new cylinder head was carried out with one intake valve closed in order to get an idea of the swirl to be generated by this approach. In the study the in-cylinder flow field, the cylinder charge and turbulence kinetic energy have been examined.
2010-04-12
Technical Paper
2010-01-0739
Y. Gong, O. Kaario, A. Tilli, M. Larmi, F.X. Tanner
Hydrotreated vegetable oil (HVO) is a high-cetane number alternative fuel with the potential of drastic emissions reductions in high-pressure diesel engines. In this study the behavior of HVO sprays is investigated computationally and compared with conventional diesel fuel sprays. The simulations are performed with a modified version of the C++ open source code OpenFOAM using Reynolds-averaged conservation equations for mass, species, momentum and energy. The turbulence has been modeled with a modified version of the RNG k-ε model. In particular, the turbulence interaction between the droplets and the gas has been accounted for by introducing appropriate source terms in the turbulence model equations. The spray simulations reflect the setup of the constant-volume combustion cell from which the experimental data were obtained.
2011-04-12
Journal Article
2011-01-0178
Jeff Howell
Vehicles on the road operate in the turbulent flow field resulting from the combined effects of the natural wind and the wakes of other vehicles. While substantial data exists on the properties of the natural wind, much less information is available for the wake properties of road vehicles. The wake information available for road vehicle shapes is mainly restricted to the near wake region, but to understand the vehicle operating environment it is the wake downstream of this region which is of interest. To determine the range of this area of interest requires some knowledge of the decay of the wake properties. From wind tunnel studies using small simple bluff bodies in free stream and in ground proximity the principle wake properties, velocity deficit and peak turbulence intensity have been measured. The maximum velocity deficit is shown to approximately decay with x-2/3, where x is the distance downstream, while turbulence intensity decays at a slightly slower rate.
2011-04-12
Technical Paper
2011-01-0177
Pascal Theissen, Johannes Wojciak, Kirstin Heuler, Rainer Demuth, Thomas Indinger, Nikolaus Adams
Unsteady aerodynamic flow phenomena are investigated in the wind tunnel by oscillating a realistic 50% scale model around its vertical axis. Thus the model is exposed to time-dependent flow conditions at realistic Reynolds and Strouhal numbers. Using this setup unsteady aerodynamic loads are observed to differ significantly from quasi-steady loads. In particular, the unsteady yaw moment exceeds the quasi-steady approximation by 80%. On the other hand, side force and roll moment are over predicted by quasi-steady approximation but exhibit a significant time delay. Using hotwire anemometry, a delayed reaction of the wake flow of Δt/T = 0.15 is observed, which is thought to be the principal cause for the differences between unsteady and quasi-steady aerodynamic loads. A schematic mechanism explaining these differences due to the delayed reaction of the wake flow is proposed.
2011-04-12
Technical Paper
2011-01-0176
Sinisa Krajnovic
The paper discusses an appropriate usage of large eddy simulation (LES) in external vehicle aerodynamics. Three different applications, wheelhouse flow, gusty flow and active flow control, are used to demonstrate how LES can be used to obtain new knowledge about vehicle flows. The three examples illustrate the information that can be extracted using LES in vehicle aerodynamics and show the potential of LES in explorations of this complex flow.
2011-04-12
Technical Paper
2011-01-0174
Lisa Larsson, Torbjörn Wiklund, Lennart Löfdahl
The aim of the study was to investigate the cooling performance of two cooling package positions for distribution vehicles by using Computational Fluid Dynamics. The first cooling package was positioned in the front of the vehicle, behind the grill and the second position was at the rear of the vehicle. Each case was evaluated by its cooling performance for a critical driving situation and its aerodynamic drag at 90 km/h, where the largest challenge of an alternative position is the cooling air availability. The geometry used was a semi-generic commercial vehicle, based on a medium size distribution truck with a heat rejection value set to a fixed typical level at maximum power for a 13 litre Euro 6 diesel engine. The heat exchangers included in the study were the air conditioning condenser, the charge air cooler and the radiator. It was found that the main problem with the rear mounted cooling installation was the combination of the fan and the geometry after the fan.
2011-04-12
Journal Article
2011-01-0172
David Sims-Williams
This paper provides a published counterpart to the address of the same title at the 2010 SAE World Congress. A vehicle on the road encounters an unsteady flow due to turbulence in the natural wind, due to the unsteady wakes of other vehicles and as a result of traversing through the stationary wakes of road side obstacles. This last term is of greatest significance. Various works related to the characterization, simulation and effects of on-road turbulence are compared together on the turbulence spectrum to highlight differences and similarities. The different works involve different geometries and different approaches to simulating cross wind transients but together these works provide guidance on the most important aspects of the unsteadiness. On-road transients include a range of length scales spanning several orders of magnitude but the most important scales are in the in the 2-20 vehicle length range.
2011-04-12
Technical Paper
2011-01-0171
Dirk Baeder, Thomas Indinger, Nikolaus Adams, Friedhelm Decker
Computational Fluid Dynamics (CFD) is state of the art in the aerodynamic development process of vehicles nowadays. With increasing computer power the numerical simulations including meshing and turbulence modeling are capturing the complex geometry of vehicles and the flow field behavior around and behind a bluff body in more detail. The ultimate goal for realistic automotive simulations is to model the under-hood as well. In this study vehicle simulations using the finite volume open source CFD program OpenFOAM® are validated with own experiments on a modified generic quarter-scale SAE body with under-hood flow. A model radiator was included to take account of the pressure drop in the under-hood compartment. Force and pressure measurements around the car, total-pressure and hot-wire measurements in the car flow field and surface flow patterns were simulated and compared with the experiment.
2011-04-12
Technical Paper
2011-01-0170
Ashok D. Khondge, Sandeep Sovani, Gunjan Verma
Thorough design exploration is essential for improving vehicle performance in various aspects such as aerodynamic drag. Shape optimization algorithms in combination with computational tools such as Computational Fluid Dynamics (CFD) play an important role in design exploration. The present work describes a Free-Form Deformation (FFD) approach implemented within a general purpose CFD code for parameterization and modification of the aerodynamic shape of real-life vehicle models. Various vehicle shape parameters are constructed and utilized to change the shape of a vehicle using a mesh morphing technique based on the FFD algorithm. Based on input and output parameters, a design of experiments (DOE) matrix is created. CFD simulations are run and a response surface is constructed to study the sensitivity of the output parameter (aerodynamic drag) to variations in each input parameter.
2011-04-12
Technical Paper
2011-01-0169
Robert Louis Lietz
Recent advances in morphing, simulation, and optimization technologies have enabled analytically driven aerodynamic shape optimization to become a reality. This paper will discuss the integration of these technologies into a single process which enables the aerodynamicist to optimize vehicle shape as well as gain a much deeper understanding of the design space around a given exterior theme.
2011-04-12
Technical Paper
2011-01-0153
Makoto Tsubokura, See Yuan Cheng, Takuji Nakashima, Yoshihiro Okada, Takahide Nouzawa
We investigate the pitching stability characteristics of sedan-type vehicles using large-eddy simulation (LES) technique. Pitching oscillation is a commonly encountered phenomenon when a vehicle is running on a road. Attributed to the change in a vehicle's position during pitching, the flow field around it is altered accordingly. This causes a change in aerodynamic forces and moments exerted on the vehicle. The resulting vehicle's response is complex and assumed to be unsteady, which is too complicated to be interpreted in a conventional wind tunnel or using a numerical method that relies on the steady state solution. Hence, we developed an LES method for solving unsteady aerodynamic forces and moments acting on a vehicle during pitching. The pitching motion of a vehicle during LES was produced by using the arbitrary Lagrangian-Eulerian technique. We compared two simplified vehicle models representing actual sedan-type vehicles with different pitching stability characteristics.
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