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Vehicle Aerodynamics, 2018

2018-04-03
Vehicle aerodynamic development, drag reduction and fuel economy, handling and stability, cooling flows, surface soiling and water management, vehicle internal environment, tyre aerodynamics and modelling, aeroacoustics, structural response to aerodynamic loading, simulating the on-road environment, onset flow turbulence, unsteady aerodynamics, fundamental flow structures, new test methods and facilities, new applications of computational fluid dynamics simulation, competition vehicle aerodynamics.
Technical Paper

Application of Computational Fluid Dynamics for Flow Force Optimization of a High Pressure Fuel Injector Spill Valve

1999-05-03
1999-01-1537
Development of Caterpillar Fuel Systems' MEUI-B injector has involved application of Computational Fluid Dynamics (CFD) in order to improve performance of the high pressure spill valve. Initial performance bench testing with concept stage experimental injectors indicated that the chamber pressure was decaying at an unacceptably slow rate, and the valve demonstrated erratic behavior at some operating conditions. The slow pressure decay and inconsistent spill valve motion were believed to be caused by flow forces generated during the low lift portion of the spill valve opening event. This theory was pursued by utilizing CFD to design two valves for testing in the next phase of the injector development cycle: A baseline geometry, similar to the original concept injector valve, and a new design incorporating localized seat geometry changes for inducing flow force assisted valve opening.
Technical Paper

Shoebox Converter Design for Thinwall Ceramic Substrates

1999-05-03
1999-01-1542
Shoebox catalytic converter design to securely mount thinwall substrates with uniform mounting mat Gap Bulk Density (GBD) around the substrate is developed and validated. Computational Fluid Dynamic (CFD) analysis, using heat transfer predictions with and without chemical reaction, allows to carefully select the mounting mat material for the targeted shell skin temperature. CFD analysis enables to design the converter inlet and outlet cones to obtain uniform exhaust gas flow to achieve maximum converter performance and reduce mat erosion. Finite Element Analysis (FEA) is used to design and optimize manufacturing tool geometry and control process. FEA gives insight to simulate the canning process using displacement control to identify and optimize the closing speed and load to achieve uniform mat Gap Bulk Density between the shell and the substrate.
Technical Paper

An Integrated Study of the Ford PRODIGY Aerodynamics using Computational Fluid Dynamics with Experimental Support

2000-04-02
2000-01-1578
The Ford P2000 prototype vehicle represents Ford Motor Company's commitment towards environmental stewardship through high fuel efficiency and low tailpipe emission. Low aerodynamic drag coefficient (Cd), weight reduction, and power train efficiency improvements are required in order to accomplish the overall fuel economy target. The objective of this study is to establish an aerodynamic efficient body shape (Cd = .20) that meets the cost, weight, styling, package and fuel economy targets. Furthermore, this vehicle must be able to be operated and manufactured. A new computational fluid dynamics (CFD) method based on a lattice gas approach was piloted for developing and evaluating body shape design alternatives in support of the P2000 PRODIGY aerodynamic objective. Wind tunnel tests were performed to further explore the aerodynamic opportunities that are beyond the capability of the computational method as well as validate the CFD prediction.
Technical Paper

Aerodynamics of the Bell P-39 Airacobra and P-63 Kingcobra

2000-05-09
2000-01-1678
This paper provides a retrospective of the aerodynamics of the Bell P-39 Airacobra and the Bell P-63 Kingcobra. Design details and information obtained from several drag reduction investigations conducted on these aircraft are presented. Additionally, results from a modern Computational Fluid Dynamics analysis of these aircraft are shown.
Technical Paper

Using CFD For Humidity Clearing Simulation of a Composite Headlamp

2000-04-02
2000-01-1598
The headlamp designs of today and the future will be increasingly complex to match the increasingly dramatic vehicle designs. These complex shapes require lamps that are vented to relieve pressure and thermal stresses. Specifying headlamp vent locations to optimize humidity clearing while minimizing dust intrusion is often a trial and error process requiring several iterations using prototypes. Computational Fluid Dynamics external flow simulations can provide an accurate view of the lamp external air flow and pressure gradients which allows the designer to specify vent locations for maximum air exchange. CFD can thus reduce the need for prototyping and testing while reducing cost.
Technical Paper

CFD Approach for Optimum Design of DI Combustion System in Small Versatile Diesel Engine

1999-09-28
1999-01-3261
The simulation techniques play important role on contemporary engine design. In this study, computer fluid dynamics approach (CFD) was focused to design the intake and combustion system of the direct injection diesel engine for versatile use. A practicality was stressed as much as an accuracy to correspond to designer and researcher's requirements, such as close relationship to the engine performance and short period of computation. The correlation of the trapping efficiency and the swirl ratio was mainly focused. A steady flow rig tests and engine operation data were combined to improve their quality mutually.
Technical Paper

An Assessment of a Stratified Scavenging Process Applied to a Loop Scavenged Two-Stroke Engine

1999-09-28
1999-01-3272
Stratified scavenging has been applied to two-stroke engines to improve fuel consumption and reduce exhaust emissions. To evaluation how this is achieved a stratified scavenging process was simulated using a three-gas single-cycle scavenging apparatus. The experiment simulated the fuel stream entering the rear transfer port of a five port cylinder and air streams entering the remaining ports. The scavenging efficiency and fuel trapping are calculated after the cycle by examining the cylinder contents. The design of the apparatus is particularly suited to investigating cylinder design changes during the prototype stage of engine development. A simulation of the stratified scavenging experiment using the Computational Fluid dynamics (CFD) code VECTIS, showed good correlation with measured results. The simulation provides a real insight into the cylinder flow behaviour of the separate fuel and air streams entering the cylinder.
Technical Paper

AVL SDIS Mk.II - Low Cost Automotive FI Applied to 2-Stroke Engines for Future CARB - Regulations

1999-09-28
1999-01-3285
The basic Semi-Direct-Injection System (SDIS) which is already in production for PWC and applied to small 2-wheeler engines features a low-pressure fuel injection system injecting through the rear scavenge port window in the cylinder symmetry plane onto the piston crown. The patented new SDIS Mk.II System [1] injects through an (additional) scavenge port window that is positioned above the scavenge ports and is controlled by a window in the piston skirt. This new arrangement allows longer injection duration and also other injector positions and directions. A CFD simulation by AVL's FIRE-CFD-code with moving piston and exhaust gas dynamics compares the different injector positions and directions for WOT and rated speed and for a part throttle low speed case. The SDIS Mk.II injection system consists of mass-produced automotive parts thus giving a low cost approach for present 2-stroke engines requiring only moderate engine modifications.
Technical Paper

Numerical Study of Fuel/Air Mixture Preparation in a GDI Engine

1999-10-25
1999-01-3657
Numerical simulations are performed to investigate the fuel/air mixing preparation in a gasoline direct injection (GDI) engine. A two-valve OHV engine with wedge combustion chamber is investigated since automobiles equipped with this type of engine are readily available in the U.S. market. Modifying and retrofitting these engines for GDI operation could become a viable scenario for some engine manufactures. A pressure-swirl injector and wide spacing injection layout are adapted to enhance mixture preparation. The primary interest is on preparing the mixture with adequate equivalence ratio at the spark plug under a wide range of engine operating conditions. Two different engine operating conditions are investigated with respect to engine speed and load. A modified version of the KIVA-3V multi-dimensional CFD code is used. The modified code includes the Linearized Instability Sheet Atomization (LISA) model to simulate the development of the hollow cone spray.
Technical Paper

Performance of Prototype High Pressure Swirl Injector Nozzles for Gasoline Direct Injection

1999-10-25
1999-01-3654
Prototype intermittent swirl-generating nozzles for gasoline direct injection application were fabricated by modifying MPI injector nozzles. Design parameters include geometric configuration of nozzle internal flow passage such as orifice diameter and length, needle geometry and swirler passage designs. Operating parameters are considered such as injection pressure, ambient pressure, injected fuel mass and duration of injector opening. Performances of the nozzles have been characterized in terms of static and transient flow rate, initial and overall spray angle, penetration, mean droplet diameter and drop size distribution. Computational fluid dynamic modeling of internal flow for the nozzles provided additional insight in addition to the experimental measurements. Sprays from the prototype nozzle used for measurement in this study exhibited the general features of swirl injection sprays.
Technical Paper

Light Truck Aerodynamic Simulations Using a Lattice Gas Based Simulation Technique

1999-11-15
1999-01-3756
Several studies have been conducted in an effort to bring Computational Fluid Dynamics (CFD) out of the research arena (5) and into the product design environment as a useful aerodynamic design tool. The focus of these studies has ranged from extremely simple shapes to more complex geometries representative of real vehicles. This paper presents the results of real vehicle applications in which CFD was used to predict the aerodynamic effect of proposed surface modifications. The simulation data was generated using a numerical method derived from lattice gas theory to evaluate the aerodynamic effect of surface modifications. The commercial software Powerflow was used to prepare the model, perform the simulation and post-process the results. These case studies were performed in parallel with real vehicle development programs. The depth of experimental comparison data was limited by traditional vehicle program timing and budget constraints.
Technical Paper

Correlating the Diesel Spray Behavior to Nozzle Design

1999-10-25
1999-01-3555
This paper studies the effect of nozzle geometry on the flow characteristics inside a diesel fuel injection nozzle and correlates to the subsequent atomization process under different operating conditions, using simple turbulent breakup model. Two kinds of nozzles, valve covered orifice (VCO) and mini-SAC nozzle, with various nozzle design parameters were studied. The internal flow inside the nozzle was simulated using 3-D computational fluid dynamics software with k-ε turbulence model. The flow field at the nozzle exit was characterized by two parameters: the fuel discharge coefficient Cd and the initial amplitude parameter amp0. The latter parameter represents the turbulence characteristics of the exit flow. The effects of nozzle geometry on the mean velocity and turbulent energy distribution of the exit flow were also studied. The characteristics of the exit flow were then incorporated into the spray model in KIVA-II to study the effect of nozzle design on diesel spray behavior.
Technical Paper

Torque Converter Analytical Program for Blade Design Process

2000-03-06
2000-01-1145
In this paper, an integrated torque converter design process is described which improves converter performance while reduces the design cycle time and number of hardware iterations. The process utilizes a suite of tools to achieve the objectives. For quick and flexible geometry layout, the TORUS DESIGN TOOL is employed to create the underlying 2D-torus geometry with given packaging constraints. The BLADE DESIGN TOOL is subsequently used to generate 3D sheet-metal type profiles for the impeller, turbine, and reactor blades. The tool is equipped with a parametric capability for blade curvature and blade angle control to meet the performance requirements. The AIRFOIL DESIGN TOOL utilizes a sophisticated, parameterized algorithm to generate the desired airfoil shape around the reactor camber-line for improved performance.
Technical Paper

Development of a Closed Loop, Full Scale Automotive Climatic Wind Tunnel

2000-03-06
2000-01-1375
A closed loop full-scale automotive climatic wind tunnel is described. The tunnel simulates wind and rain as well as several road conditions. It generates under controlled heat loading, wind speeds of up to 50kmh with different approach boundary conditions, rains from drizzle to cloudburst and road inclines up to 15° in any direction. The design and optimization process of the tunnel functions is outlined and examples of its use in vehicle development are given. The size constraint and the need for a compact design are important features of the tunnel. The tunnel provides an important test bed for close scrutiny of the relationship between rain ingress, vehicle speed, road condition, heat loading and vehicle geometry. The tunnel can also be used to study vehicle thermal management, vehicle thermal comfort, engine cold starting, and wipers efficiency in sever cold weather.
Technical Paper

Three-Dimensional Heat Transfer & Thermoelastic Deformation Predictions in Forward Lighting

2000-03-06
2000-01-1396
The thermal performance of an automotive forward-lighting assembly is predicted with a computational fluid-dynamics (CFD) program. A three-dimensional, steady-state heat-transfer model seeks to account for convection and radiation within the enclosure, conduction through the thermoplastic walls and lens, and external convection and radiation losses. The predicted temperatures agree well with experimental thermocouple and infrared data on the housing. Driven by the thermal expansion of the air near the bulb surface, counter-rotating recirculation zones are predicted within the enclosure. The highest temperatures in the plastic components are predicted on the inner surface of the shelf above the bulb where airflow rising from the hot bulb surface impinges.
Technical Paper

Catalytic Converter Design, Development and Manufacturing

2000-01-15
2000-01-1417
Computer aided engineering is used to design, develop, optimize and manufacture catalytic converter. Heatcad, a transient heat transfer analysis is used to simulate the temperature response in the exhaust system to locate the catalytic converter to achieve maximum performance. Heatcad analysis provides the easy way to identify thermal management issues and to design and optimize the runner lengths and material thicknesses of the manifold, and downpipes. P-Cat is used to estimate back pressure due to substrates, end cones, and inlet/outlet pipes. Catheat, a one dimentional heat transfer tool is used to identify the converter insulation to maintain the required external skin temperature. Computational Fluid Dynamics (CFD) analysis, a powerful means of simulating complex fluid flow situations in the exhaust system, is used to optimize the converter inlet and outlet cones and the downpipes to obtain uniform exhaust gas flow to achieve maximum converter performance and reduce mat erosion.
Technical Paper

Simulation of Combustion in a DI-Diesel Engine with Application of a Moving Grid

2000-06-19
2000-01-1888
This paper focuses on the initial stage of internal combustion, auto-ignition. The fuel used for simulation of a DI-diesel engine in this study is n-heptane. The condensed model based on formulations for n-heptane [1], iso-octane and a mixture of fuels [2]. The engine simulated is a 1.9 liter VW research engine. CFD simulations have to be done fast, if the user wants to experiment with the simulation. For a rapid simulation of the kinetic in a reacting turbulent flow, only a couple of active species can be calculated. An additional way to decrease the solution time is to keep the number of elements small. In this paper a model describes the reactive processes in the gas phase of a diesel engine, using the RIF-model (RIF: Representative Interactive Flamelets) [3] with a flexible discretisation by the method of lines and a dynamic adaptive grid technique [4]. The other possibility is just to focus on the ignition process by using a condensed model.
Technical Paper

CFD Studies of Combustion and In-Cylinder Soot Trends in a DI Diesel Engine - Comparison to Direct Photography Studies

2000-06-19
2000-01-1889
The main objective of this work is to develop a CFD model for studies of combustion and in-cylinder soot trends in a single cylinder DI diesel engine based on the Scania 14 liter V8 engine. The evaluation of the model is made with respect to ignition, cylinder pressure, heat release, onset of diffusion controlled combustion, liquid fuel spray penetration, in-cylinder soot distribution and exhaust soot level. The simulation results are compared to direct photography images and two-color calculations of temperature and soot distribution in a corresponding optical access test engine. This comparison shows good agreement concerning diffusion flame onset, liquid penetration, rate of heat release and local temperature distribution. Moreover, the prediction of in-cylinder soot distribution after end of injection also agrees well with the two-color calculation. To validate the model, the simulation is repeated for three different sets of operating conditions.
Technical Paper

Extension of Lagrangian-Eulerian Spray Modeling: Application to High Pressure Evaporating Diesel Sprays

2000-06-19
2000-01-1893
The Lagrangian-Eulerian approach is commonly used to simulate engine sprays. However typical spray computations are strongly mesh dependent. This is explained by an inadequate space resolution of the strong velocity and vapor concentration gradients. In Diesel sprays for instance, the Eulerian field is not properly computed close to the nozzle exit in the vicinity of the liquid phase. This causes an overestimated diffusion that leads to inaccuracies in the modeling of fuel-air mixing. By now it is not possible to enhance grid resolution since it would violate requested assumptions for the Lagrangian liquid phase description. Besides, a full Eulerian approach with an adapted mesh is not practical at the moment mainly because of prohibitive computer requirements. Keeping the Lagrangian-Eulerian approach, a new methodology is introduced: the full Lagrangian-Eulerian Coupling (CLE).
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