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General Motors Full Scale Wind Tunnel Upgrade

General Motors LLC-Nina Tortosa
Jacobs Technology-Paul Nagle, Tyler Brooker
  • Technical Paper
  • 2020-01-0687
To be published on 2020-04-14 by SAE International in United States
The General Motors Aero Lab’s Full Scale Wind Tunnel Facility, which came into operation in August of 1980, has undergone the significant upgrade of installing a state-of-the-art moving ground plane system. After almost four decades of continued use the full-scale wind tunnel also received some significant maintenance to other areas, including a new heat exchanger, main fan overhaul, and replacement of the test section acoustic treatment. A 5-belt system was installed along with an integrated vehicle lift system. The center belt measures 8m long, and can accommodate two belt widths of 1100mm and 900mm. Flow quality and other wind tunnel performance parameters were maintained to prior standards which are on par with the latest industry standards. The new 5-belt rolling road system maintains GM’s industry leading vehicle aerodynamic development and the improved acoustic panels ensure GM continues to develop vehicles with leading class acoustics.
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Stability of Flowing Combustion in Adaptive Cycle Engines

Illinois Institute of Technology-Prashanth Tamilselvam, Francisco Ruiz
  • Technical Paper
  • 2020-01-0296
To be published on 2020-04-14 by SAE International in United States
In an Adaptive Cycle Engine (ACE), thermodynamics favors combustion starting while the compressed, premixed air and fuel are still flowing into the cylinder through the transfer valve. Since the flow velocity is typically high, and is predicted to reach sonic conditions by the time the transfer valve closes, the flame might be subjected to extensive stretch, thus leading to aerodynamic quenching. It is also unclear whether a single spark, or even a succession of sparks, will be sufficient to achieve complete combustion. Given that the first ACE prototype is still being built, this issue is addressed by numerical simulation using the G-equation model, which accounts for the effect of flame stretching, over a 3D domain representing a flat-piston ACE cylinder, both with inward- and outward-opening valves. RNG K-Epsilon turbulence model was used to approximate the highly turbulent flow field. It was found that the flame would suffer local blow-off under most operating conditions, but the blow-off is never complete so that the regions affected are later re-ignited by the remaining parts of the flame, and…
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Investigation of the Effect of Tire Deformation on Open-Wheel Aerodynamics

Graz University of Technology-Philipp Eder, Cornelia Lex
U.A.S. Graz-Thomas Gerstorfer, Thomas Amhofer
  • Technical Paper
  • 2020-01-0546
To be published on 2020-04-14 by SAE International in United States
This paper introduces a finite element (FE) approach to determine tire deformation and its effect on open-wheeled racecar aerodynamics. In recent literature the tire deformation was measured optically using cameras during wind tunnel testing. Combined loads like accelerat-ing at corner exit are difficult to reproduce in wind tunnels and would require several camer-as to measure the tire deformation. In contrast, an FE approach is capable of determining the tire deformation in combined load states accurately and additionally provides the possibility to vary further parameters, for example, the coefficient of friction. The FE tire model was validated using stiffness measurements, contact patch measurements and steady-state cornering measurements on a flat belt tire test rig. The deformed shape of the FE model was used in a computational fluid dynamics (CFD) simulation. A sensitivity study was created to determine the effect of the tire deformation on aerodynamics for un-loaded, purely vertically loaded and combined vertical, lateral and longitudinal forces. In addition, the influence of these three tire deformations was investigated in a CFD study using a full vehicle…
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A Study on the Effect of Debris Location on a Double Element Wing in Ground Effect

Loughborough University-Tom Marsh, Graham Hodgson, Andrew Garmory, Dipesh Patel
  • Technical Paper
  • 2020-01-0693
To be published on 2020-04-14 by SAE International in United States
Multi-element front wings are essential in numerous motorsport series, such as Formula 1, for the generation of downforce and control of the onset flows to other surfaces and cooling systems. Rubber tyre debris from the soft compounds used in such series can become attached to the wing, reducing downforce, increasing drag and altering the wake characteristics of the wing. This work studies, through force balance and Particle Image Velocimetry measurements, the effect a piece of debris has on an inverted double element wing in ground effect. The wing was mounted at a ride height determined to minimise separation from a fixed false-floor in the Loughborough University Large Wind Tunnel. The debris is modelled using a hard-setting putty and is located at different span and chord-wise positions around the wing. The sensitivity to location is studied and the effect on the wake analysed using PIV measurements. The largest effect on downforce was observed when the debris was located on the underside of the wing towards the endplates. The wake was most effected when the debris was…
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Investigation of the Effectiveness of a Passive Device for Soiling Mitigation for Vehicle Side-Cameras

Ontario Tech University-William Collings, Wing Yi Pao, Martin Agelin-chaab
  • Technical Paper
  • 2020-01-0699
To be published on 2020-04-14 by SAE International in United States
The development of modern autonomous automotive technology depends heavily on the reliable performance of external sensors that are vulnerable to soiling. Existing active cleaning devices, such as washers and wipers, are relatively complex, expensive or unsuitable. Furthermore, little research has been done on alternative soiling mitigation strategies and devices for sensors. With the emerging trend to replace side-mirrors with camera monitor systems, it is important for such systems to stay clean even in adverse weather in order to provide critical navigation information. To meet this need, a passive aerodynamics-based cleaning device was investigated. A converging vent device was integrated into the side-camera housing and the subsequent degree of soiling was estimated at wind speeds of 15, 20, and 25 m/s (representing city and country driving speeds). The vent outlet width, outlet jet angle, and outlet jet velocity of the vent device were varied and the variants were compared to the non-vented reference model. The degree of soiling was evaluated computationally and experimentally. A single phase simulation was performed using ANSYS® Fluent where the degree of…
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Investigation of Transient Aerodynamic Effects on Public Highways in Comparison to Individual Driving Situations on a Test Site

FKFS-Felix Wittmeier, Andreas Wagner, Jochen Wiedemann
German Aerospace Center (DLR)-Henning Wilhelmi, Andreas Dillmann
  • Technical Paper
  • 2020-01-0670
To be published on 2020-04-14 by SAE International in United States
Natural wind, roadside obstacles, terrain roughness, and traffic can influence the incident flow of a vehicle driven on public roads. These on-road conditions differ from the idealized statistical steady-state flow environment utilized in CFD simulations and wind tunnel experiments. To understand these transient on-road conditions better, measurements were taken on a test site and on German Autobahn, resulting in the characterization of the transient aerodynamic effects around a vehicle. A compact car was equipped with a measurement system that is capable of determining the transient airflow around the vehicle and the vehicle’s actual driving state. This vehicle was driven several times on a fixed route to investigate different traffic densities on public highways in southern Germany. The tests were conducted under consistent weather conditions and average wind velocities of 2-5 m/s. During the tests the transient incident flow and pressure distribution on the vehicle surface were measured. With the same vehicle, individual driving situations were recreated on a test site. This paper presents a comparison of the aerodynamic characteristics measured by the vehicle during a…
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Optimization of the Aerodynamic Lift and Drag of LYNK&CO 03+ with Simulation and Wind Tunnel Test

Dassault Systemes(Shanghai) Information Technology Co.-Weiliang Xie, Bo Li, Xiaowei Zhao
Geely Automobile Research Institute-Qian Feng, Biaoneng Luo, Huixiang Zhang, Hong Peng, Zhenying Zhu, Zhi Ding, Ling Zhu
  • Technical Paper
  • 2020-01-0672
To be published on 2020-04-14 by SAE International in United States
Based on the first sedan of the LYNK&CO brand from Geely, a high performance configuration with the additional aerodynamic package was developed. The aerodynamic package including the front wheel deflector, the front lip, the side skirt, the rear spoiler and the rear diffuser, were upgraded to generate enough aerodynamic downforce for better handing stability, without too much compromising of the aerodynamic drag of the vehicle to keep a low fuel consumption. Simulation approach with PowerFLOW, combined with the design space exploration method were used to optimize both of the aerodynamic lift and drag. Wind tunnel test was also used to firstly calibrate the simulation results and finally to validate the optimized design. The results turn out to be appropriate trade-off between the lift and the drag to meet the aerodynamics requirement, and a consistently good matching between the simulation and test.
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Parametric Study of Reduced Span Side Tapering on a Simplified Model with Wheels

Jaguar Land Rover-Adrian Gaylard
Loughborough University-Max Varney, Martin Passmore, Ryan Swakeen
  • Technical Paper
  • 2020-01-0680
To be published on 2020-04-14 by SAE International in United States
Sports Utility Vehicles (SUVs) often have blunt rear end geometries for design aesthetics and practicality, however, such vehicles are potentially high drag. The application of tapering; typically applied to an entire edge of the base of the geometry is widely reported as a means of reducing drag, but in many cases this is not practical on real vehicles. In this study side tapers are applied to only part of the side edge of a simplified automotive geometry, to show the effects of practical implementations of tapers. The paper reports on a parametric study undertaken in Loughborough University’s Large Wind Tunnel with the ¼ scale Windsor model equipped with wheels. The aerodynamic effect of implementing partial side edge tapers is assessed from a full height taper to a 25% taper in both an upper and lower body configuration. These were investigated using force and moment coefficients, pressure measurements and planar particle image velocimetry (PIV). These geometries showed that the drag reductions are maximised with a 50% span, generating a vertically symmetric wake and less taper drag…
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Active grille shutters control and benefits in medium to large SUV: A system engineering approach

Jaguar Land Rover-Nilabza Dutta, Mark Spenley, Paul Cromback-Dugeny, Benjamin Stegmann, Wilko Jansen, Megan Parfitt
  • Technical Paper
  • 2020-01-0945
To be published on 2020-04-14 by SAE International in United States
Whilst the primary function of the active grille shutters is to reduce the aerodynamic drag of the car, there are some secondary benefits like improving the warm up time of engine and also retaining engine heat when parked. In turbocharged IC engines the air is compressed (heated) in the turbo and then cooled by a low temperature cooling system before going into the engine. When the air intake temperature exceeds a threshold value, the engine efficiency falls - this drives the need for the cooling airflow across the radiator in normal operation. Airflow is also required to manage the convective heat transfer across various components in engine bay for its lifetime thermal durability. Grill shutters can also influence the aerodynamic lift balance thus impacting the vehicle dynamics in high speed. The vehicle HeVAC system also relies on the condenser in the front heat exchanger pack disposing the waste heat off in the most efficient way. These requirements of maintaining optimal engine intake charge air temperature, managing condenser heat load, engine bay heat and aerodynamic lift…
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On Road Fuel Economy Impact by the Aerodynamic Specifications under the Natural Wind

Honda R&D Co., Ltd.-Yasuyuki Onishi, Kenta Ogawa, Jun Sawada, Youji Suwa, Fortunato Nucera
  • Technical Paper
  • 2020-01-0678
To be published on 2020-04-14 by SAE International in United States
According to some papers, the label fuel economy and the actual fuel economy experienced by the customers may exhibit a gap. One of the reasons may stem from the aerodynamic drag variations due to the natural wind. The fuel consumptions are measured on the bench test under the several driving modes by using the road load as input conditions. The road load is measured through the coast down test under less wind ambient conditions as determined by each regulation. The present paper aims to analyze the natural wind specifications encountered by the vehicle on the public road and to operate a comparison between the fuel consumptions and the driving energy. In this paper, the driving energy is calculated by the aerodynamic drag from the natural wind specifications and driving conditions. This driving energy and the fuel consumptions show good correlation. The fuel consumption is obtained from the vehicle ECU data. The driving energy is calculated by the aerodynamic drag and the vehicle driving conditions through the time history data on the road. Aerodynamic drag is…