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SAE International Journal of Passenger Cars Mechanical Systems
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Effect of Vortex Generator on Flow Field Quality in 3/4 Open Jet Automotive Wind Tunnel

SAE International Journal of Passenger Cars - Mechanical Systems

Tongji University-Di Bao, Qing Jia, Zhigang Yang
  • Journal Article
  • 2017-01-1530
Published 2017-03-28 by SAE International in United States
Based on a 1:15 scaled 3/4 open jet automotive wind tunnel, this paper studies the effect of vortex generator on the buffeting phenomenon. The mean velocity, static pressure gradient, turbulent intensity as well as frequencies of fluctuant velocities have been explored experimentally with and without vortex generator. It shows that the less protruding vortex generator could control the buffeting phenomenon and improve the flow quality. Furthermore, the unsteady coherent structures in the jet shear layer have been visualized and analyzed by Detached-eddy simulation (DES). The vortex-ring pairing process is identified in the shear layer along with obvious frequency characteristics and velocity fluctuations. The vortex generator can postpone and restrain this vortex-ring pairing process, then reducing the velocity fluctuations.
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Ejector Energy-Saving Technology for Mobile Air Conditioning Systems

SAE International Journal of Passenger Cars - Mechanical Systems

DENSO Corporation-Yoichiro Kawamoto, Gota Ogata
DENSO International America, Inc.-Zhiwei Shan
  • Journal Article
  • 2017-01-0120
Published 2017-03-28 by SAE International in United States
This study reports on a new generation ECS (Ejector Cycle System) which includes a highly efficient ejector and a novel system configuration. The ejector is working as a fluid jet pump that recovers expansion energy which is wasted in the conventional refrigeration cycle decompression process, and converts the recovered expansion energy into pressure energy and raises the compressor suction pressure. Consequently, the ejector system can reduce power consumption of the compressor by using the above mentioned pressure-rising effect and improve energy efficiency of the refrigeration cycle. The ejector consists of a nozzle, a suction section, a mixing section and a diffuser. The objective of this study is to improve actual fuel economy of all vehicles by ejector technology. The previous generation ECS was reported in 2012 SAE World Congress1. Now, a new generation ECS has been successfully developed and released in the market for Mobile Air Conditioning systems as of 2013. It achieves higher energy efficiency through the development of ARC (Active flow Ratio Control. It means to control the refrigerant flow ratio of the…
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Aerodynamic Investigation of Cooling Drag of a Production Sedan Part 2: CFD Results

SAE International Journal of Passenger Cars - Mechanical Systems

Ford Motor Company-Levon Larson, Ronald Gin, Robert Lietz
  • Journal Article
  • 2017-01-1528
Published 2017-03-28 by SAE International in United States
Cooling drag is a metric that measures the influence of air flow travelling through the open grille of a ground vehicle on overall vehicle drag, both internally (engine air flow) and externally (interference air flow). With the interference effects considered, a vehicles cooling drag can be influenced by various air flow fields around the vehicle, not just the air flow directly entering or leaving the engine bay. For this reason, computational fluid dynamics (CFD) simulations are particularly difficult. With insights gained from a previously conducted set of experimental studies, a CFD validation effort was undergone to understand which air flow field characteristics contribute to CFD/test discrepancies. A Lattice-Boltzmann Large Eddy Simulation (LES) method was used to validate several test points. Comparison using integral force values, surface pressures, and cooling pack air mass flows was presented. The test points include cooling pack configuration changes, underbody shield changes and vehicle attitude changes. Select test points were compared in both static and moving ground wind tunnel conditions. This paper represents the second of a two-part effort, with experimental…
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Analysis of the Effectiveness of Evaporator’s Hydrophilic Coating of Cores Recovered from Humid and Arid Regions

SAE International Journal of Passenger Cars - Mechanical Systems

CalsonicKansei North America Inc.-Gursaran D. Mathur
  • Journal Article
  • 2017-01-0122
Published 2017-03-28 by SAE International in United States
Water drainage characteristics are dependent on the design of the evaporator: specifically the design of the fins and plates along with hydrophilic coating. A part of the hydrophilic coating washes off with the moisture that condenses over the evaporator core from the air-stream. Hence, water drainage characteristics of an evaporator changes with the vehicle mileage or the age of the vehicle. Since a part of the hydrophilic coating washes away, more water is retained within the evaporator at this condition. Hence, the effectiveness of the evaporator drainage deteriorates with the age of the vehicles. At this condition, the contact angle measured at the plate increases.Author has conducted an experimental study to measure the effectiveness of hydrophilic coating from evaporators taken out from arid (9 cores) and humid areas (16 cores) as a function of vehicle mileage or vehicle age. Contact angles and water retention were measured for a number of evaporators from different OEMs. These cores are from different vehicles, with different manufacturers for the evaporators with different fin and plate design; and with different…
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The Effect of a Sheared Crosswind Flow on Car Aerodynamics

SAE International Journal of Passenger Cars - Mechanical Systems

Loughborough University-Jeff Howell, David Forbes, Martin Passmore, Gary Page
  • Journal Article
  • 2017-01-1536
Published 2017-03-28 by SAE International in United States
In the wind tunnel the effect of a wind input on the aerodynamic characteristics of any road vehicle is simulated by yawing the vehicle. This represents a wind input where the wind velocity is constant with height above the ground. In reality the natural wind is a boundary layer flow and is sheared so that the wind velocity will vary with height. A CFD simulation has been conducted to compare the aerodynamic characteristics of a DrivAer model, in fastback and squareback form, subject to a crosswind flow, with and without shear. The yaw simulation has been carried out at a yaw angle of 10° and with one shear flow exponent. It is shown that the car experiences almost identical forces and moments in the two cases when the mass flow in the crosswind over the height of the car is similar. Load distributions are presented for the two cases. The implications for wind averaged drag are discussed.
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OEM's Approach on Design and Evaluation of Plastic Clamps

SAE International Journal of Passenger Cars - Mechanical Systems

Maruti Suzuki India Limited-Harchetan Singh Aneja, Harmeet Singh, Aashish Parmar, Rohan Sharma
  • Journal Article
  • 2017-01-0484
Published 2017-03-28 by SAE International in United States
The automotive industry, known for its competitiveness & innovations globally, researches for continuous improvement of part performances along with reduction of cost & weight. These are amongst the top priority goals across all OEMs. In the long list of automobile parts, pipe clamps have paved their way of design through generations from being of metal to plastic that has expanded its scope of application & performance.In an automobile, plastic clamps are widely used to hold single or multiple water, fuel or brake pipes of various diameters to vehicle body at various locations such as underbody (prone to stone chipping) or engine room (prone to high temperatures), etc. Plastic clamps are preferred over metallic clamps for their cost, weight, performance & productivity. Primarily, in all application areas, a clamp must be able to hold the pipes with consistent & sufficient performance that is quantified through parameters such as thrust force and pipe removal force. Hence, selection of ideal material becomes an important factor. As an example, clamps at underbody application are highly prone to stone chipping,…
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Influence of Nozzle Divergent Part Length and Throat Diameter on Vortex Control of Initially Subcooled Flashing Flow

SAE International Journal of Passenger Cars - Mechanical Systems

University of Illinois-Jingwei Zhu, Stefan Elbel
  • Journal Article
  • 2017-01-0165
Published 2017-03-28 by SAE International in United States
Expansion work recovery by two-phase ejector is known to be beneficial to vapor compression cycle performance. However, one of the biggest challenges with ejector vapor compression cycle is that the ejector cycle performance is sensitive to working condition changes which are common in many applications, including automotive AC systems. Different working conditions require different ejector geometries to achieve maximum performance. Slightly different geometries may result in substantially different COPs under the same conditions. Ejector motive nozzle throat diameter (motive nozzle restrictiveness) is one of the key parameters that can significantly affect COP. This paper presents the experimental investigation of a new motive nozzle restrictiveness control mechanism for two-phase ejectors used in vapor compression cycles, which has the advantages of being simple, potentially less costly and less vulnerable to clogging. The redesigned ejector utilizes an adjustable vortex at the motive inlet to control the nozzle restrictiveness on the flow expanded in the motive nozzle. Adjustable nozzles based on this new control mechanism were designed and manufactured for experiments with R134a. The influence of nozzle divergent part…
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Optimum Seat Cooling Distribution for Targeted Human Thermal Comfort®

SAE International Journal of Passenger Cars - Mechanical Systems

Gentherm-Aditya Velivelli, Daniel Guerithault, Stefan Stöwe
  • Journal Article
  • 2017-01-0170
Published 2017-03-28 by SAE International in United States
Seat cooling and heating strategies have enhanced human thermal comfort in automotive environments. Cooling/heating strategies also need to focus on the distribution of the seat cooling/heating power across the seat and the effect of such distributions on human thermal comfort. This paper studies the effect of active cooling combined with ventilation only strategy on thermal comfort. As part of the study, heat flux between the occupant and seat is mapped and is correlated to a step increase in the occupant’s local thermal comfort of body segments in contact with seat. A human physiological model and the Berkeley comfort model were combined to determine power and optimum placement of cooling to effectively cool an occupant using a climate control seat in a warm environment. This leads to a new approach using asymmetric seat cooling to distribute cooling power resulting in improved and balanced subjective comfort than traditional climate seat and ventilation technologies. A computational model was developed and validated through chamber test results. The computational model can deliver temperature distribution and thermal sensation/comfort values for varied…
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The Effect of Passive Base Ventilation on the Aerodynamic Drag of a Generic SUV Vehicle

SAE International Journal of Passenger Cars - Mechanical Systems

Jaguar Land Rover-Adrian Gaylard
Loughborough University-Max Varney, Martin Passmore
  • Journal Article
  • 2017-01-1548
Published 2017-03-28 by SAE International in United States
Sports Utility Vehicles (SUVs) typically have a blunt rear end shape (for design and practicality), however this is not beneficial for aerodynamic drag. Drag can be reduced by a number of passive and active methods such as tapering and blowing into the base. In an effort to combine these effects and to reduce the drag of a visually square geometry slots have been introduced in the upper side and roof trailing edges of a squareback geometry, to take air from the freestream and passively injects it into the base of the vehicle to effectively create a tapered body.This investigation has been conducted in the Loughborough University’s Large Wind Tunnel with the ¼ scale generic SUV model. The basic aerodynamic effect of a range of body tapers and straight slots have been assessed for 0° yaw. This includes force and pressure measurements for most configurations. The slots generate useful, but small, drag reductions with the best configurations giving reductions in drag coefficient (Cd) of approximately 0.01, whereas the best taper configurations reduce Cd by close to…
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Coupled Level-Set Volume of Fluid Simulations of Water Flowing Over a Simplified Drainage Channel With and Without Air Coflow

SAE International Journal of Passenger Cars - Mechanical Systems

Loughborough University-Mehriar Dianat, Maciej Skarysz, Graham Hodgson, Andrew Garmory, Martin Passmore
  • Journal Article
  • 2017-01-1552
Published 2017-03-28 by SAE International in United States
The motivation for this paper is to predict the flow of water over exterior surfaces of road vehicles. We present simulations of liquid flows on solid surfaces under the influence of gravity with and without the addition of aerodynamic forces on the liquid. This is done using an implementation of a Coupled Level Set Volume of Fluid method (CLSVOF) multiphase approach implemented in the open source OpenFOAM CFD code. This is a high fidelity interface-resolving method that solves for the velocity field in both phases without restrictions on the flow regime. In the current paper the suitability of the approach to Exterior Water Management (EWM) is demonstrated using the representative test cases of a continuous liquid rivulet flowing along an inclined surface with a channel located downstream perpendicular to the oncoming flow. Experimental work has been carried out to record the motion of the rivulet in this case and also to measure the contact angle of the liquid with the solid surface. The measurements of the liquid/solid characteristics such as equilibrium and dynamic contact angles…
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