| 1. |
- Landström, Christoffer, 1982, et al.
(författare)
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Aerodynamic Effects of Different Tire Models on a Sedan Type Passenger Car
- 2012
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Ingår i: SAE International Journal of Commercial Vehicles. - : SAE International. - 1946-3928 .- 1946-391X. ; 2012
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Tidskriftsartikel (refereegranskat)abstract
- Targets for reducing emissions and improving energy efficiency present the automotive industry with many challenges. Passenger carsare by far the most common means of personal transport in the developed part of the world, and energy consumption related topersonal transportation is predicted to increase significantly in the coming decades. Improved aerodynamic performance of passengercars will be one of many important areas which will occupy engineers and researchers for the foreseeable future.The significance of wheels and wheel housings is well known today, but the relative importance of the different components has stillnot been fully investigated. A number of investigations highlighting the importance of proper ground simulation have been published,and recently a number of studies on improved aerodynamic design of the wheel have been presented as well.This study is an investigation of aerodynamic influences of different tyres. Two different tyre models were investigated incombination with three different wheel designs using the Volvo Aerodynamic Wind Tunnel; including moving ground and rotatingwheels. In addition to force measurements, flow field investigations were also performed using both surface pressure probes and 12-hole pressure probes. The tyre sizes investigated in this study were 215/50R17 and 215/55R16. An investigation of changes to the tyregeometry for 215/55/R16 tyres was also performed using two high speed cameras in the wind tunnel.Results show that different tyre types have a significant effect on not only aerodynamic drag, but also on lift to some extent. Dragdifferences between 5 – 10 drag counts were measured depending on wheel and vehicle configuration. It was also concluded that thedrag difference between tyre types was dependent on wheel design. The flow field investigations showed noticeable changes to thefront wheel wake structures as well as significant changes in the rear wheel and base wake structures. Investigations of the tyredeformations showed changes in wheel lift, as well as radial expansion and axial compression correlating with the observed dragchanges.
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| 2. |
- Carbonne, Louis, et al.
(författare)
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Use of Full Coupling of Aerodynamics and Vehicle Dynamics for Numerical Simulation of the Crosswind Stability of Ground Vehicles
- 2016
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Ingår i: SAE International Journal of Commercial Vehicles. - : SAE International.. - 1946-391X .- 1946-3928. ; 9:2, s. 359-370
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Tidskriftsartikel (refereegranskat)abstract
- The prediction in the design phase of the stability of ground vehicles subject to transient crosswinds become of increased concern with drag reduced shapes, lighter vehicles as well as platooning. The objective of this work is to assess the order of model complexity needed in numerical simulations to capture the behavior of a ground vehicle passing through a transient crosswind. The performance of a full-dynamic coupling between aerodynamic and vehicle dynamic simulations, including a driver model, is evaluated. In the simulations a feedback from the vehicle dynamics into the aerodynamic simulation is performed in every time step. In the work, both the vehicle dynamic response and the aerodynamic forces and moments are studied. The results are compared to a static coupling approach on a set of different vehicle geometries. Five car-type geometries and one simplified bus geometry are evaluated. The aerodynamic loads and moments are obtained using Detached Eddy Simulation (DES) where the motion of the vehicle is enabled using an overset mesh technique. This motion is calculated with a single-track model, including a driver model and handling two degrees of freedom, namely lateral translation and yaw motion.The results show that for vehicles undertaking large yaw moments and therefore large yaw motions, like the bus-type geometry, the full dynamic coupling is beneficial. In this case, a static coupling overestimates the aerodynamic loads and in turn the vehicle motion. On less crosswind sensitive vehicles, like the car-type geometries, the full-coupling approach does not modify the results in a significant way compared to a static coupling.
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| 3. |
- Ekman, Petter, et al.
(författare)
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Aerodynamics of an Unloaded Timber Truck - A CFD Investigation
- 2016
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Ingår i: SAE International Journal of Commercial Vehicles. - : SAE INT. - 1946-391X .- 1946-3928. ; 9:2, s. 217-223
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Tidskriftsartikel (refereegranskat)abstract
- Reducing energy consumption and emissions are ongoing challenges for the transport sector. The increased number of goods transports emphasize these challenges even more, as greenhouse gas emissions from these vehicles increased by 20 % between 1990 and 2013, in Sweden. One special case of goods transports is the transport of timber. Today in Sweden, around 2000 timber trucks transport around six billion ton kilometers every year. For every ton kilometer these vehicles use around 0.025 liter diesel, and there should exist large possibilities to reduce the fuel consumption and the emissions for these vehicles. Timber trucks spend most of their operation time travelling in speeds of around 80 km/h. At this speed aerodynamic drag contributes to around 30 % of the total vehicle resistance, which makes the aerodynamic drag a significant part of the energy consumption. One of the big challenges with timber trucks is that they travel unloaded half of the time. This put higher demands on possible drag reduction modifications, as they need to function and be practical for both when the timber truck is loaded and unloaded. In this study an unloaded timber truck has been investigated by use of computational fluid dynamics. The recently released Stress Blended Eddy Simulation model has been used for simulating the flow over a timber truck at a Reynolds number of 1.1 million, based on the square root of its frontal area. From the results it could be seen that 52.8 % of the drag is generated by the cab. By investigating a drag reduction device that covered the gap between the bulkhead and the first stake pair, a drag reduction up to 6.7 % was possible, which shows potential for simple modifications that not influence the daily usage.
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| 4. |
- Gaylard, Adrian Philip, et al.
(författare)
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A Computational Investigation of Ground Simulation for a Saloon Car
- 2014
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Ingår i: SAE International Journal of Passenger Cars - Mechanical Systems. - : SAE International. - 1946-3995 .- 1946-4002. ; 7:1, s. 111-123
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Tidskriftsartikel (refereegranskat)abstract
- Automotive aerodynamics measurements and simulations now routinely use a moving ground and rotating wheels (MVG&RW), which is more representative of on-road conditions than the fixed ground-fixed wheel (FG&FW) alternative. This can be understood as a combination of three elements: (a) moving ground (MVG), (b) rotating front wheels (RWF) and (c) rotating rear wheels (RWR). The interaction of these elements with the flow field has been explored to date by mainly experimental means.This paper presents a mainly computational (CFD) investigation of the effect of RWF and RWR, in combination with MVG, on the flow field around a saloon vehicle. The influence of MVG&RW is presented both in terms of a combined change from a FG&FW baseline and the incremental effects seen by the addition of each element separately.For this vehicle, noticeable decrease in both drag and rear lift is shown when adding MVG&RW, whereas front lift shows little change. The same trends are seen in both CFD and experimental data.The addition of MVG alone increases both drag and front lift, whereas rear lift decreases significantly. The addition of RWF alone has little effect on the global results (aside from lift), whereas the addition of RWR alone decreases both drag and rear lift significantly. Combining the incremental changes produces values that align well to the MVG&RW case, with the exception of front lift.This shows similar trends to previously published work, both the noticeable drag decrease due to the addition of MVG&RW, and the contributions of the individual components.
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| 5. |
- Grubinger, Thomas, et al.
(författare)
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Knowledge Extraction from Real-World Logged Truck Data
- 2009
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Ingår i: SAE International Journal of Commercial Vehicles. - Warrendale, PA : Society of Automotive Engineers. - 1946-391X .- 1946-3928. ; 2:1, s. 64-74
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Tidskriftsartikel (refereegranskat)abstract
- In recent years more data is logged from the electronic control units on-board in commercial vehicles. Typically, the data is transferred from the vehicle at the workshop to a centralized storage for future analysis. This vast amount of data is used for debugging, as a knowledgebase for the design engineer and as a tool for service planning.Manual analysis of this data is often time consuming, due to the rich amount of information contained. However, there is an opportunity to automatically assist in the process based on knowledge discovery techniques, even directly when the trucks data is first offloaded at the workshop. One typical example of how this technique could be helpful is when two groups of trucks behave differently, e.g. one well-functioning group and one faulty group, when the two groups have the same specification. The desired information is the specific difference in the logged data, e.g. what particular sensors or signals are different.An evaluation cycle is proposed and applied to extract knowledge from three different large real-world data-sets measured on Volvo long haulage trucks. Information in the logged data that describes the vehicle’s operating environment, allows the detection of trucks that are operated differently from their intended use. Experiments to find such vehicles were conducted and recommendations for an automated application are given.
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| 6. |
- Henriksson, Lisa, 1984, et al.
(författare)
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Experimental Investigation of Heat Transfer Rate and Pressure Drop through Angled Compact Heat Exchangers Relative to the Incoming Airflow
- 2014
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Ingår i: SAE International Journal of Commercial Vehicles. - : SAE International. - 1946-3928 .- 1946-391X. ; 7:2, s. 448-457
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Tidskriftsartikel (refereegranskat)abstract
- The investigation showed that a more inclined heat exchanger resulted in lower static pressure drop and at the same time achieved a higher heat transfer rate, for a specific mass airflow rate. This result was obtained for all three heat exchangers. When analysing the parameters at the same core speed it was seen that the static pressure drop was increased for the 10° and the 30° angled heat exchangers, compared to the 90° configuration. For the 60° cases the pressure drop was both increased and decreased compared to the 90° cases, depending on the heat exchanger design. It was also seen that the pressure drop and the heat transfer rate variation were negligible between the downflow and crossflow orientation of the heat exchanger. When defining the static pressure drop to 200Pa either a 19mm thick heat exchanger at 60° or a 52mm heat exchanger at 90° can be used to obtain the same heat transfer rate.This paper presents pressure drops and heat transfer rates for compact heat exchangers, where the heat exchangers are angled 90°, 60°, 30° and 10° relative to the incoming airflow. The investigation is based on three heat exchangers with thicknesses of 19mm and 52mm. Each heat exchanger was mounted in a duct, where it was tested for thermal and isothermal conditions. The inlet temperature of the coolant was defined to two temperatures; ambient temperature and 90°C. For the ambient cases the coolant had the same temperature as the surrounding air, these tests were performed for five airflow rates. When the coolant had a temperature of 90°C a combination of five coolant flow rates and five airflow rates were tested. The test set-up was defined as having a constant cross-section area for 90°, 60° and 30° angles, resulting in a larger core area and a lower airspeed through the core, for a more inclined heat exchanger.
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| 7. |
- Lee, Chih Feng, et al.
(författare)
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Active Brake Judder Compensation Using an Electro-Hydraulic Brake System
- 2015
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Ingår i: SAE International Journal of Commercial Vehicles. - Warrendale : S A E Inc.. - 1946-391X .- 1946-3928. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Geometric imperfections on brake rotor surface are well-known for causing periodic variations in brake torque during braking. This leads to brake judder, where vibrations are felt in the brake pedal, vehicle floor and/or steering wheel. Existing solutions to address judder often involve multiple phases of component design, extensive testing and improvement of manufacturing procedures, leading to the increase in development cost. To address this issue, active brake torque variation (BTV) compensation has been proposed for an electromechanical brake (EMB). The proposed compensator takes advantage of the EMB’s powerful actuator, reasonably rigid transmission unit and high bandwidth tracking performance in achieving judder reduction. In a similar vein, recent advancements in hydraulic system design and control have improved the performance of hydraulic brakes on a par with the EMB, therefore invoking the possibility of incorporating the BTV compensation feature of the EMB within hydraulic brake hardware. In this paper, the typical characteristics of electromechanical and electro-hydraulic brake systems are presented. Based on the experimental results, the feasibility of active BTV compensation on the electro-hydraulic brake (EHB) systems is discussed. Furthermore, a BTV compensation algorithm designed for the EMB is presented and is shown to be applicable to the EHB. Using an experimentally validated model of BTV, the compensation was performed on a hardware in-the-loop EHB test rig. The preliminary results demonstrate the potential of using an EHB to compensate for brake judder.
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| 8. |
- Lindgärde, O., et al.
(författare)
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Optimal Vehicle Control for Fuel Efficiency
- 2015
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Ingår i: SAE International Journal of Commercial Vehicles. - : SAE International. - 1946-391X .- 1946-3928. ; 8:2, s. 682-694
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Tidskriftsartikel (refereegranskat)abstract
- CONVENIENT is a project where prediction and integrated control are applied on several subsystems with electrified actuators. The technologies developed in this project are applied to a long-haul tractor and semi-trailer combination. A Volvo truck meeting the Eu6 emission standard is rebuilt with a number of controllable electrified actuators. An e-Horizon system collects information about future road topography and speed limits. Controllable aerodynamic wind deflectors reduce the wind drag. The tractor is also equipped with a full digital cluster for human machine interface development. A primary project goal is to develop a model-based optimal controller that uses predictive information from the e-Horizon system in order to minimize fuel consumption. Several energy buffers are controlled in an integrated and optimal way using model predictive control. Several buffers are considered, such as the cooling system, the battery, and the vehicle kinetic energy. This paper presents details on the model predictive controller of the battery system and of the cooling system. Another project goal is to reduce fuel consumption by using adaptive aerodynamics. Controllers are developed that automatically sets an optimal roof deflector angle and the optimal side deflector angle. The results presented in this paper are encouraging. A third focus is the human machine interface and especially the communication between the driver and the control system during driving. This project develops a driver interface that encourages the driver to use the adaptive cruise controller when appropriate. The CONVENIENT project will be finalized this year. This paper presents the main project findings.
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| 9. |
- Lundahl, Kristoffer, 1984-, et al.
(författare)
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Analyzing Rollover Indices for Critical Truck Maneuvers
- 2015
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Ingår i: SAE International Journal of Commercial Vehicles. - : SAE International. - 1946-391X .- 1946-3928. ; 8:1, s. 189-196
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Tidskriftsartikel (refereegranskat)abstract
- Rollover has for long been a major safety concern for trucks, and will be even more so as automated driving is envisaged to becoming a key element of future mobility. A natural way to address rollover is to extend the capabilities of current active-safety systems with a system that intervenes by steering or braking actuation when there is a risk of rollover. Assessing and predicting the rollover is usually performed using rollover indices calculated either from lateral acceleration or lateral load transfer. Since these indices are evaluated based on different physical observations it is not obvious how they can be compared or how well they reflect rollover events in different situations.In this paper we investigate the implication of the above mentioned rollover indices in different critical maneuvers for a heavy 8×4 twin-steer truck. The analysis is based on optimal control applied to a five degrees of freedom chassis model with individual wheel dynamics and high-fidelity tire-force modeling. Driving scenarios prone to rollover accidents are considered, with a circular-shaped turn and a slalom maneuver being studied in-depth. The optimization objective for the considered maneuvers are formulated as minimum-time and maximum entry-speed problems, both triggering critical maneuvers and forcing the vehicle to operate on the limit of its physical capabilities. The implication of the rollover indices on the optimal trajectories is investigated by constraining the optimal maneuvers with different rollover indices, thus limiting the vehicle's maneuvering envelope with respect to each rollover index. The resulting optimal trajectories constrained by different rollover indices are compared and analyzed in detail. Additionally, the conservativeness of the indices for assessing the risk of rollovers are discussed.
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| 10. |
- Löfstrand, Sofia, et al.
(författare)
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Feasibility of Electrifying Urban Goods Distribution Trucks
- 2013
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Ingår i: SAE International Journal of Commercial Vehicles. - : SAE International. - 1946-391X .- 1946-3928. ; 6:1, s. 24-33
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the feasibility of electrifying medium to heavy urban goods distribution trucks. As a case study, an existing transport system in the Swedish city of Gothenburg is used. The project is a joint research effort between a vehicle OEM, an electric utility, a fleet operator, the Swedish Transport Administration and two research organizations. One main objective is to determine if and when different electrified powertrains are cost efficient to the end user. The results indicate that by 2015 conventional powertrains are still probably the most cost effective alternative in all applications studied. But in 2025, electrified powertrains are most cost efficient for most transport scenarios. These results indicate a transition in preferred powertrain technology for urban trucks within the coming ten years. It is important to point out that this result may not be general. Driving patterns, energy price developments and technology maturity of components such as batteries and motors greatly influence the total cost of ownership and large regional differences in when such a transition may occur are expected. In addition to the total cost of ownership, important issues for a successful deployment are policies (e.g. restricting access to urban areas for noisy and polluting vehicles), information and communication solutions (e.g. adapted route planning), access to a cost effective charging infrastructure (and low-carbon electricity production) and new business models. These must all be developed in parallel to the vehicle and powertrain technology. The large number of different stakeholders involved in this transition is also a challenge in itself.
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