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SAE International Journal of Passenger Cars Mechanical Systems
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In-Vehicle Characterization of Wet Clutch Engagement Behaviors in Automatic Transmission Systems

SAE International Journal of Passenger Cars - Mechanical Systems

Ford Motor Company-Hiral Haria, Gregory M. Pietron, Jason Meyer, Yuji Fujii
University of Michigan-Pengchuan Wang, Nikolaos Katopodes
  • Journal Article
  • 2018-01-0395
Published 2018-04-03 by SAE International in United States
A new generation of a planetary-gear-based automatic transmission system is designed with an increasing number of ratio steps. It requires synchronous operation of one or more wet clutches, to achieve a complex shift event. A missed synchronization results in drive torque disturbance which may be perceived by vehicle occupants as an undesirable shift shock. Accurate knowledge of clutch behaviors in an actual vehicle environment is indispensable for achieving precise clutch controls and reducing shift calibration effort. Wet clutches are routinely evaluated on an industry-standard SAE#2 tester during the clutch design process. While it is a valuable tool for screening relative frictional behaviors, clutch engagement data from a SAE#2 tester do not correlate well with vehicle shift behaviors due to the limited reproducibility of realistic slip, actuator force profiles, and lubrication conditions. Advanced clutch testers with programmable slip and force controller are available for replicating torque phase and inertia phase of shifting. However, it remains a challenge to substantiate bench test data in the absence of actual clutch behaviors observed in a vehicle. This article describes…
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Flow Visualization and Experimental Measurement of Compressor Oil Separator

SAE International Journal of Passenger Cars - Mechanical Systems

University of Illinois at Urbana-Champaign-Jiu Xu, Pega Hrnjak
  • Journal Article
  • 2018-01-0067
Published 2018-04-03 by SAE International in United States
This article presents basic separation mechanisms with coalescing/impinging separators studied as the add-on to current popular centrifugal designs. The coalescence and impingement of oil on wire mesh and wave-plates are visualized and tested to investigate the impact of geometry and flow conditions on oil separation efficiency. Re-entrainment phenomenon is explained based on the mass balance. Oil mist flow at the swashplate reciprocating compressor discharge is quantified by video processing method to provide detailed information of the oil droplets. The physics behind oil separator is illustrated by visualization and measurement in this study, which gives useful guidelines for oil separator design and operation. The flow visualization shows the details of oil passing through different oil separation structures. Videos are quantified to provide information like droplet size distribution and liquid volume fraction. Experimental measurement shows that effective separation efficiency decreases when vapor velocity goes up. This is because higher vapor velocity brings higher liquid volume fraction and smaller droplets and higher vapor velocity will makes more trapped oil re-entrained.
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An Objective Measure for Automotive Surface Contamination

SAE International Journal of Passenger Cars - Mechanical Systems

Jaguar Land Rover Ltd.-Adrian Gaylard
Loughborough University-Graham Hodgson, Martin Passmore, Andrew Garmory
  • Journal Article
  • 2018-01-0727
Published 2018-04-03 by SAE International in United States
Surface contamination, or soiling, of the exterior of road vehicles can be unsightly, can reduce visibility and customer satisfaction, and, with the increasing application of surface-mounted sensors, can degrade the performance of advanced driver-assistance systems. Experimental methods of evaluating surface contamination are increasingly used in the product development process, but the results are generally subjective. The use of computational methods for predicting contamination makes objective measures possible, but comparable data from experiment is an important validation requirement.This article describes the development of an objective measure of surface contamination arising during experiments. A series of controlled experiments using ultraviolet (UV) dye-doped water are conducted to develop a robust methodology. This process is then applied to a simplified contamination test. An image of a surface, illuminated by an UV lamp, is captured after every test along with a calibration vessel with known fluid depth. The image is processed to remove the influence of variation in incident illumination. The total mass of contamination deposited is then calculated using the calibration vessel to provide the required local fluid depths.…
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Lockheed Martin Low-Speed Wind Tunnel Acoustic Upgrade

SAE International Journal of Passenger Cars - Mechanical Systems

General Motors LLC-James Zunich
Jacobs-Scott Best
  • Journal Article
  • 2018-01-0749
Published 2018-04-03 by SAE International in United States
The Lockheed Martin Low-Speed Wind Tunnel (LSWT) is a closed-return wind tunnel with two solid-wall test sections. This facility originally entered into service in 1967 for aerodynamic research of aircraft in low-speed and vertical/short take-off and landing (V/STOL) flight. Since this time, the client base has evolved to include a significant level of automotive aerodynamic testing, and the needs of the automotive clientele have progressed to include acoustic testing capability. The LSWT was therefore acoustically upgraded in 2016 to reduce background noise levels and to minimize acoustic reflections within the low-speed test section (LSTS). The acoustic upgrade involved detailed analysis, design, specification, and installation of acoustically treated wall surfaces and turning vanes in the circuit as well as low self-noise acoustic wall and ceiling treatment in the solid-wall LSTS. The preservation of the aerodynamic flow quality and the reduction in background noise levels in the LSTS were demonstrated by a series of measurements that were performed both prior to and after the acoustic upgrade.
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Active Crosswind Generation and Its Effect on the Unsteady Aerodynamic Vehicle Properties Determined in an Open Jet Wind Tunnel

SAE International Journal of Passenger Cars - Mechanical Systems

FKFS-Daniel Stoll, Jochen Wiedemann
  • Journal Article
  • 2018-01-0722
Published 2018-04-03 by SAE International in United States
In this article the unsteady aerodynamic properties of a 25% scale DrivAer notchback model as well as the influence of the wind tunnel environment on the resulting unsteady aerodynamic forces and moments under crosswind excitation are investigated using experimental and corresponding numerical methods. Research Institute of Automotive Engineering and Vehicle Engines Stuttgart (FKFS) swing® (side wind generator) is used to reproduce the essential properties of natural stochastic crosswind in the open jet test section of the Institute for Internal Combustion Engines and Automotive Engineering (IVK) model scale wind tunnel (MWK). The results show that the test environment of an open jet wind tunnel alters the amplitudes of side force and yaw moment under crosswind excitation when compared to an ideal environment neglecting wind tunnel interference effects. The presented approach for the quantification of the unsteady behavior of the flow field provides a basic understanding of the phenomena occurring under the dynamic deflection of a wind tunnel jet. It is shown that the wind tunnel jet has a dynamic behavior that is superimposed on the aerodynamic…
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Effects of Moving Ground and Rotating Wheels on Aerodynamic Drag of a Two-Box Vehicle

SAE International Journal of Passenger Cars - Mechanical Systems

Mizuho Information & Research Institute-Ryo Takayama, Tsutomu Takayama, Yoshinobu Yamade
Toyota Motor Corp.-Taro Yamashita, Takafumi Makihara, Yuta Saito
  • Journal Article
  • 2018-01-0730
Published 2018-04-03 by SAE International in United States
Previous studies and recent practical aerodynamic evaluations have shown that aerodynamic drag of passenger vehicles with “ground simulation” with moving ground and rotating wheels may increase in some cases and decrease in other cases relative to the fixed ground and stationary wheel conditions. Accordingly, the effects of the ground simulation on the aerodynamic drag should be deeply understood for further drag reduction. Although the previous studies demonstrated what is changed by the ground simulation, the reason for the change has not been fully understood. In this article, the effects of wheels and wheel houses attachment and those by the ground simulation with ground movement and wheel rotation on the aerodynamic drag were investigated by quantification of the underfloor flow that plays a crucially important role on the formation of vortical structure around vehicles. Wall-resolved large eddy simulations (WR-LES), which used approximately 5 billion grid elements, were conducted for two hatchback vehicle models with a backlight slant angle of 30 degrees measured from the horizontal line: one with flattened rear underfloor (non-swept case) and the other…
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A Drag Coefficient for Test Cycle Application

SAE International Journal of Passenger Cars - Mechanical Systems

Jaguar Land Rover Ltd.-Steve Windsor
Loughborough University-Jeff Howell, Martin Passmore
  • Journal Article
  • 2018-01-0742
Published 2018-04-03 by SAE International in United States
The drag coefficient at zero yaw angle is the single parameter usually used to define the aerodynamic drag characteristics of a passenger car. However, this is usually the minimum drag condition and will, for example, lead to an underestimate of the effect of aerodynamic drag on fuel consumption because the important influence of the natural wind has been excluded. An alternative measure of aerodynamic drag should take into account the effect of nonzero yaw angles and a variant of wind-averaged drag is suggested as the best option. A wind-averaged drag coefficient (CDW) is usually derived for a particular vehicle speed using a representative wind speed distribution. In the particular case where the road speed distribution is specified, as for a drive cycle to determine fuel economy, a relevant drag coefficient can be derived by using a weighted road speed. This approach has been used to determine an effective drag coefficient for a range of cars using the proposed test cycle for the Worldwide harmonized Light vehicle Test Procedure (WLTP). A terrain-related wind profile, to give…
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Modelling the Effect of Spray Breakup, Coalescence, and Evaporation on Vehicle Surface Contamination Dynamics

SAE International Journal of Passenger Cars - Mechanical Systems

Jaguar Land Rover Ltd.-Adrian Gaylard
Loughborough University-Anton Kabanovs, Andrew Garmory, Martin Passmore
  • Journal Article
  • 2018-01-0705
Published 2018-04-03 by SAE International in United States
Vehicle surface contamination is an important design consideration as it affects drivers’ vision and the performance of onboard camera and sensor systems. Previous work has shown that eddy-resolving methods are able to accurately capture the flow field and particle transport, leading to good agreement for vehicle soiling with experiments. What is less clear is whether the secondary breakup, coalescence, and evaporation of liquid particles play an important role in spray dynamics. The work reported here attempts to answer this and also give an idea of the computational cost associated with these extra physics models. A quarter-scale generic Sports Utility Vehicle (SUV) model is used as a test case in which the continuous phase is solved using the Spalart-Allmaras Improved Delayed Detached Eddy Simulation (IDDES) model. The dispersed phase is computed concurrently with the continuous phase using the Lagrangian approach. The Taylor Analogy Breakup (TAB) secondary breakup and the stochastic O’Rourke coalescence models are used. The spray’s rate of evaporation is calculated based on the relative humidity encountered on a typical October day in Britain. The…
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Aerodynamic Investigation of Cooling Drag of a Production Pickup Truck Part 1: Test Results

SAE International Journal of Passenger Cars - Mechanical Systems

Ford Motor Company-Levon Larson, Sudesh Woodiga
  • Journal Article
  • 2018-01-0740
Published 2018-04-03 by SAE International in United States
The airflow that enters the front grille of a ground vehicle for the purpose of component cooling has a significant effect on aerodynamic drag. This drag component is commonly referred to as cooling drag, which denotes the difference in drag measured between open grille and closed grille conditions. When the front grille is closed, the airflow that would have entered the front grille is redirected around the body. This airflow is commonly referred to as cooling interference airflow. Consequently, cooling interference airflow can lead to differences in vehicle component drag; this component of cooling drag is known as cooling interference drag. One mechanism that has been commonly utilized to directly influence the cooling drag, by reducing the engine airflow, is active grille shutters (AGS). For certain driving conditions, the AGS system can restrict airflow from passing through the heat exchangers, which significantly reduces cooling drag. The difference in drag between the AGS vanes being open and closed is referred to as AGS drag. Another vehicle component that influences the cooling drag is chin spoilers. Chin…
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Development and Initial Testing of a Full-Scale DrivAer Generic Realistic Wind Tunnel Correlation and Calibration Model

SAE International Journal of Passenger Cars - Mechanical Systems

Ford Motor Company-Taryn James, Lothar Krueger, Manfred Lentzen, Sudesh Woodiga, Karel Chalupa, Burkhard Hupertz, Neil Lewington
  • Journal Article
  • 2018-01-0731
Published 2018-04-03 by SAE International in United States
Wind tunnel testing is conducted to determine the aerodynamic characteristics of a vehicle under controlled and well-defined boundary conditions. Differences in wind tunnel facility layout, design, and subsequent onset flow conditions may result in differing aerodynamic conditions being attained for the same test property in different test facilities. Several OEMs develop vehicles in different regions and utilize local test facilities during the vehicle design process. Understanding the flow characteristics and correlations between test facilities is therefore essential to ensure that global processes can utilize data obtained in any region.Typically, automotive facility correlations are derived by evaluating a fleet of production level test properties in each facility. Adopting a test fleet approach for facility correlation yields three key issues; firstly, there are significant logistics and timing constraints. Secondly, over time the test fleet will deteriorate and potentially introduce random errors in the test data. Thirdly, test facility modifications may require repeat fleet assessments.This article aims to detail the development of a full-scale generic test property with the ability to better represent complex flow phenomena associated with…
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