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Technical Paper

Validation Studies for an Advanced Aerodynamic Development Process of Cab-Over Type Heavy Trucks

2017-10-25
2017-01-7009
The implementation of an advanced process for the aerodynamic development of cab-over type heavy trucks at China FAW Group Corporation (FAW) requires a rigorous validation of the tools employed in this process. The final objective of the aerodynamic optimization of a heavy truck is the reduction of the fuel consumption. The aerodynamic drag of a heavy truck contributes up to 50% of the overall resistance and thus fuel consumption. An accurate prediction of the aerodynamic drag under real world driving conditions is therefore very important. Tools used for the aerodynamic development of heavy trucks include Computational Fluid Dynamics (CFD), wind tunnels and track and road testing methods. CFD and wind tunnels are of particular importance in the early phase development.
Journal Article

Validation of Aerodynamic Simulation and Wind Tunnel Test of the New Buick Excelle GT

2017-03-28
2017-01-1512
The validation of vehicle aerodynamic simulation results to wind tunnel test results and simulation accuracy improvement attract considerable attention of many automotive manufacturers. In order to improve the simulation accuracy, a simulation model of the ground effects simulation system of the aerodynamic wind tunnel of the Shanghai Automotive Wind Tunnel Center was built. The model includes the scoop, the distributed suction, the tangential blowing, the moving belt and the wheel belts. The simulated boundary layer profile and the pressure distribution agree well with test results. The baseline model and multiple design changes of the new Buick Excelle GT are simulated. The simulation results agree very well with test results.
Technical Paper

The Aerodynamic Development of a New Dongfeng Heavy Truck

2015-09-29
2015-01-2886
The development of a new Dongfeng Heavy truck had very strict targets for fuel consumption. As the aerodynamic drag plays a crucial role for the fuel consumption, a low drag value had to be achieved. It was therefore essential to include evaluation and optimization of the aerodynamics in the development process. Because wind tunnel facilities were not available, the complete aerodynamics development was based on digital simulation. The major portion of the aerodynamic optimization was carried out during the styling phase where mirrors, sun visor, front bumper and aero devices were optimized for drag reduction. For optimizing corner vanes and mud guards, self-soiling from the wheel spray was included in the analysis. The aero results did also show that cooling air flow rates are sufficiently high to ensure proper cooling. During the detailed engineering phase an increase of the drag above the target required further optimization work to finally reach the target.
Technical Paper

A Coupled Approach to Truck Drum Brake Cooling

2015-09-29
2015-01-2901
Trucks can carry heavy load and when applying the brakes during for example a mountain downhill or for an abrupt stop, the brake temperatures can rise significantly. Elevated temperatures in the drum brake region can reduce the braking efficiency or can even cause the brake system to fail, catch fire or even break. It therefore needs to be designed such to be able to transfer the heat out of its system by convection, conduction and/or radiation. All three heat transfer modes play an important role since the drum brakes of trucks are not much exposed to external airflow, a significant difference from disk brakes of passenger cars analyzed in previous studies. This makes it a complex heat transfer problem which is not easy to understand. Numerical methods provide insight by visualization of the different heat transfer modes. Presented is a numerical method that simulates the transient heat transfer of a truck drum brake system cooldown at constant driving speed.
Journal Article

Aerodynamic Shape Optimization of an SUV in early Development Stage using a Response Surface Method

2014-09-30
2014-01-2445
In the development of an FAW SUV, one of the goals is to achieve a state of the art drag level. In order to achieve such an aggressive target, feedback from aerodynamics has to be included in the early stage of the design decision process. The aerodynamic performance evaluation and improvement is mostly based on CFD simulation in combination with some wind tunnel testing for verification of the simulation results. As a first step in this process, a fully detailed simulation model is built. The styling surface is combined with engine room and underbody detailed geometry from a similar size existing vehicle. From a detailed analysis of the flow field potential areas for improvement are identified and five design parameters for modifying overall shape features of the upper body are derived. In a second step, a response surface method involving design of experiments and adaptive sampling techniques are applied for characterizing the effects of the design changes.
Technical Paper

Validation Study for the Introduction of an Aerodynamic Development Process of Heavy Trucks

2014-09-30
2014-01-2444
A challenge for the aerodynamic optimization of trucks is the limited availability of wind tunnels for testing full scale trucks. FAW wants to introduce a development process which is mainly based on CFD simulation in combination with some limited amount of wind tunnel testing. While maturity of CFD simulation for truck aerodynamics has been demonstrated in recent years, a complete validation is still required before committing to a particular process. A 70% scale model is built for testing in the Shanghai Automotive Wind Tunnel Center (SAWTC). Drag and surface pressures are measured for providing a good basis for comparison to the simulation results. The simulations are performed for the truck in the open road driving condition as well as in an initial digital model of the aerodynamic wind tunnel of SAWTC. A full size truck is also simulated in the open road driving condition to understand the scaling effect.
Technical Paper

Aerodynamic Characterization of the Design Changes for the Facelift of the VW Bora

2014-04-01
2014-01-0601
The recent facelift of the Chinese version of the VW Bora incorporated several changes of the styling of the upper body. In particular, front facia, A-Pillar and rear end were subject to design changes. As major effects on the aerodynamics performance were not expected, extensive wind tunnel testing for the upper body design changes was not included in the development plan except for final performance evaluation. Nevertheless, an aerodynamic study of the effects of the design changes was undertaken using a CFD based process. At the same time, the facelift offered the opportunity for reducing the aerodynamic drag by improving the underbody flow. The design of the engine undercover and the wheel spoilers were considered in this effort. For this purpose the CFD based aerodynamic study was extended to include respective design features.
Technical Paper

Optimization of the Underbody Layout of a Small Van for Better Aerodynamics Using Digital Simulation

2014-04-01
2014-01-0574
The Wuling Rongguang is a small van which uses a mid-engine layout where the engine is located underneath the floor panel in-between front and rear wheels. A particular challenge for this kind of layout is the protection of the engine against soiling. Typical protective measures consist of large mudguards in combination with an engine cover. While needed for soiling protection, these parts can have a strongly adverse effect on aerodynamic drag. This paper describes process and the results of the aerodynamic optimization of the underbody of the Wuling Rongguang. Because design changes had to be evaluated for aerodynamics performance as well as for their effect on the soiling, a digital approach was used which allowed to do the soiling analysis as a post processing to the flow simulation. As a first step, a baseline model was built and analyzed. This included the development of a soiling model taking into account wheel spray and splashing effects.
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