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Previous research on both small-scale and full-scale vehicles shows that base extensions are an effective method to increase the base pressure, enhancing pressure recovery and reducing the wake size. These extensions decrease drag at zero yaw, but show an even larger improvement at small yaw angles. In this paper, rear extensions are investigated on an SUV in the Volvo Cars Aerodynamic Wind Tunnel with focus on the wake flow and on the unsteady behavior of the surface pressures near the base perimeter. To increase the effect of the extensions on the wake flow, the investigated configurations have a closed upper- and lower grille (closed-cooling) and the underbody has been smoothed with additional panels. This paper aims to analyze differences in flow characteristics on the wake of an SUV at 0° and 2.5° yaw, caused by different sets of extensions attached to the base perimeter. Extensions with several lengths are investigated with and without a kick.

Small children cannot use adult restraint systems in passenger cars. Their size, anatomy, tolerance to trauma and their social behaviour are factors that must be considered when designing child restraint systems (CRS). Surprisingly, and differently from adult restraint systems, CRS are not designed in the same way indicating that in different parts of the world, the analysis of the best protective systems is not the same. In the Nordic countries the tradition has been long in protecting children up to the age of 3 years by rearward facing systems. As they have proven to be very effective, it is important to share the experience with countries where less effective restraint systems for small children are used. In this paper, several aspects of rearward facing systems are presented.

Bushing elasticity is one of the most important compliance factors that significantly influence driving behavior. The deformations of the bushings change the wheel orientations under external forces. Another important factor of bushing compliance is to provide a comfortable driving experience by isolating the vibrations from road irregularities. However, the driving comfort and driving dynamics are often in conflict and need to be balanced in terms of bushing compliance design. Specifically, lateral force steer and brake force steer are closely related to safety and stability and comprises must be minimized. The sensitivity analysis helps engineers to understand the critical bushing for certain compliance attributes, but optimal balancing is complicated to understand. The combination of individual bushing stiffness must be carefully set to achieve an acceptable level of all the attributes.

The work investigates the integration between tools for analysis and simulation of cooling systems at Volvo Group Trucks Technology. At the same time it is a consequent step in evaluating GT-SUITE for the purposes of analysis and simulation of such systems. The focus is on 1D simulation tools, which are generally preferred in the context of transient simulations of engine and power train installation systems. The Cooling Analysis and Simulations group at Volvo Group Trucks Technology use a variety of 1D simulation tools for analysis of cooling performance. Volvo Power Train, on the other hand, use among others GT-SUITE for engine simulations. It is expected to improve the quality of the simulation, (i.e the accuracy of the results) and improve system integration by using one tool for both areas of simulation. This work delivers two transient models of FH 13L cooling system integrated with a predictive model of the engine and a detailed model of the main coolant circuit.

This paper presented a part of results from an ongoing project for pedestrian protection, which is carried out at Chalmers University of Technology in Sweden. A validated pedestrian mathematical model was used in this study to simulate vehicle-pedestrian impacts. A large number of simulations have been carried out with various parameters. The injury-related parameters concerning head, chest, pelvis and lower extremities were calculated to evaluate the effect of impact speed and vehicle front structure on the risk of pedestrian injuries. The effect of following vehicle parameters was studied: stiffness of bumper, hood edge, hood top, windscreen frame, and shape of vehicle front structures. A parameter study was conducted by modelling vehicle-pedestrian impacts with various sizes of cars, mini vans, and light trucks. This choice represents the trends of new vehicle fleet and their frequency of involvement in real world accidents.

The free piston internal combustion engine used in conjunction with a linear alternator offers an interesting choice for use in hybrid vehicles. The linear motion of the pistons is directly converted to electricity by the alternator, and the result is a compact and efficient energy converter that has only one moving part. The movement of the pistons is not prescribed by a crank mechanism, but is the result of the equilibrium of forces acting on the pistons, and the engine will act like a mass-spring system. This feature is one of the most prominent advantages of the FPE (Free Piston Engine), as the lack of mechanical linkage gives means of varying the compression ratio in simple manners, without changing the hardware of the engine. By varying the compression ratio, it is also it possible to run on a multitude of different fuels and to use HCCI (Homogeneous Charge Compression Ignition) combustion.

In this paper, the turbulent flow induced by a production side-view mirror assembled on a full-scale production truck is simulated using a compressible k-ω SST detached eddy simulation (DES) approach -- the improved delayed DES (IDDES). The truck configuration consists of a compartment and a trailer. Due to the large size and geometric complexity of the configuration, some simplifications are applied to the simulation. A purpose of this work is to investigate whether the simplifications are suitable to obtain the reasonable properties of the flow near the side-view mirror. Another objective is to study the aerodynamic performances of the mirror. The configuration is simplified regarding two treatments. The first treatment is to retain the key exterior components of the truck body while removing the small gaps and structures. Furthermore, the trailer is shaped in an apex-truncated square pyramid.

Diffuse brain injuries are very common in side impacts, accounting for more than half of the injuries to the head. These injuries are often sustained in less severe side impacts. An English investigation has shown that diffuse brain injuries often originate from interior contacts, most frequently with the side window. They are believed to be mainly caused by quick head rotational motions. This paper describes a test method using a Hybrid III dummy head in a wire pendulum. The head impacts a simulated side window or an inflatable device, called the Inflatable Curtain (IC), in front of the window, at different speeds, and at different impact angles. The inflated IC has a thickness of around 70 mm and an internal (over) pressure of 1.5 bar. The head was instrumented with a three axis accelerometer as well as an angular velocity sensor measuring about the vertical (z) axis. The angular acceleration was calculated.

Neck injuries in rear-end collisions are usually caused by a swift extension-flexion motion of the neck and mostly occur at low impact velocities (typically less than 20 km/h). Although the injuries are classified as AIS 1, they often lead to permanent disability. The injury risk varies a great deal between different car models. Epidemiological studies show that the effectiveness of passenger-car head-restraints in rear-end collisions generally remains poor. Rear-end collisions were simulated on a crash-sled by means of a Hybrid III dummy with a new neck (Rear Impact Dummy-neck). Seats were chosen from production car models. Differences in head-neck kinematics and kinetics between the different seats were observed at velocity changes of 5 and 12.5 km/h. Comparisons were made with an unmodified Hybrid III. The results show that the head-neck motion is influenced by the stiffness and elasticity of the backrest as well as by the properties of the head-restraint.

The automotive trends of vehicles with lower aerodynamic drag and more powerful drivetrains have caused increasing concern regarding stability issues at high speeds, since more streamlined bodies show greater sensitivity to crosswinds. This is especially pronounced for high vehicles, such as sports utility vehicles. Besides, the competitiveness in the automotive industry requires faster development times and, thus, a need to evaluate the high speed stability performance in an early design phase, preferable using simulation tools. The usefulness of these simulation tools partly relies on realistic boundary conditions for the wind and quantitative measures for assessing stability without the subjective evaluation of experienced drivers. This study employs an on-road experimental measurements setup to define relevant wind conditions and to find an objective methodology to evaluate high speed stability.

In this case study, a human factors analysis was carried out in the preliminary design phase of the Cupola, a European Space Agency (ESA) module for manned space flights for the International Space Station (ISS). The manikin software Jack® was used early in the design process before any flight hardware production. All Cupola astronaut tasks were evaluated in a virtual environment of the Cupola. Methodological aspects concerning the analysis are described, e.g. file processing, use of coordinate systems and the use of a prior task analysis. Results show that the thorough manikin analysis supported with the hierarchical task analysis results, was an important help in the design process.

In this case study, a human factors engineering (HFE) analysis was carried out in the preliminary design phase of the Cupola. Cupola is a European Space Agency (ESA) module for manned space flights for the International Space Station (ISS) as part of a Barter Arrangement between ESA and the United States National Aeronautics and Space Administration (NASA). Manikin software was used early in the design process before the production of any flight hardware. The manikin analysis was supported by the use of hierarchical task analysis, a file exchange protocol and a relational database. This paper describes methodological aspects of the use of the supporting methods. Results show that hierarchical task analysis, a file exchange protocol and a relational database are prerequisites for successful extensive manikin analysis.

Partially-Averaged Navier-Stokes Simulations (PANS) were made of flow around a generic vehicle influenced by side wind at four different yaw angles to investigate the prediction capabilities of PANS. Comparisons with results of LES show clear advantages of PANS in predicting pressure-induced separation resulting in the trailing vortices aligned with the direction of the flow. Poorer agreement was obtained in the near wake when the boundary layer separates at the end of the surface at the rear end. A possible explanation for the lack of accuracy at the rear end of the body was found in the formulation of the switching coefficient fk which produces too low values resulting in too low eddy viscosity in this region.

Axial cooling fans are commonly used in electric vehicles to cool batteries with high heating load. One drawback of the cooling fans is the high aeroacoustic noise level resulting from the fan blades and the obstacles facing the airflow. To create a comfortable cabin environment in the vehicle, and to reduce exterior noise emission, a low-noise installation design of the axial fan is required. The purpose of the study is to investigate efficient computational aeroacoustics (CAA) simulation processes to assist the cooling-fan installation design. In this paper we report the current progress of the investigation, where the narrow-band components of the fan noise is focused on. Two methods are used to compute the noise source. In the first method the source is computed from the flow field obtained using the unsteady Reynolds-averaged Navier-Stokes equations (unsteady RANS, or URANS) model.

Modelling is widely used for the development of hybrid electric vehicle (HEV) powertrain technologies, since it can provide accurate prediction of fuel consumption and CO₂ emissions, for a fraction of the resources required in experiments. For comparison of different technologies or powertrain parameters, the results should be accurate relative to each other, since powertrains are simulated under identical model details and simulation parameters. However, when CO₂ emissions of a vehicle model are simulated under a driving cycle, significant deviances may occur between actual tests and simulation results, compromising the integrity of simulations. Therefore, this paper investigates the effects of certain modelling and simulation parameters on CO₂ emission results, for a parallel HEV under three driving cycles (NEDC, WLTC and RTS95 to simulate real driving emissions (RDE)).

The shift toward electrification and limitations in battery electric vehicle technology have led to high demand for hybrid vehicles (HEVs) that utilize a battery and an internal combustion engine (ICE) for propulsion. Although HEVs enable lower fuel consumption and emissions compared to conventional vehicles, they still require combustion of fuels for ICE operation. Thus, emissions from hybrid vehicles are still a major concern. Engine starts are a major source of emissions during any driving event, especially before the three-way catalyst (TWC) reaches its light-off temperature. Since the engine is subjected to multiple starts during most driving events, it is important to mitigate and better understand the impact of these emissions. In this study, experiments were conducted to analyze engine starts in a hybrid powertrain on different experimental setup.

When designing an electric vehicle (EV) traction system, overcoming the issues arising from the variations in the battery voltage due to the state of charge (SoC) is critical, which otherwise can lead to a deterioration of the powertrain energy efficiency and overall drive performance. However, systems are typically documented under fixed voltage and temperature conditions, potentially lacking comprehensive specifications that account for these variations across the entire range of the vehicle operating regions. To tackle this challenge, this paper seeks to adjust an optimal DC-link voltage across the complete range of drive operating conditions by integrating a DC-DC converter into the powertrain, thereby enhancing powertrain efficiency. This involves conducting a comprehensive analysis of power losses in the power electronics of a connected converter-inverter system considering the temperature variations, along with machine losses, accounting for variable DC-link voltages.

Lean gas engines have a potential for a significant reduction in both fuel consumption and emission levels. The use of a small pre-chamber with controlled stoichiometric or rich mixture composition is an effective way to deal with ignition problems in such engines. A constant volume vessel equipped with a device for generation of turbulence of known quantities is used to study the operation of a cylindrical pre-chamber of 1% of the main chamber volume. Pressure was measured in the main chamber and Schlieren images of the flame initiation and propagation in the main chamber were recorded for all set-ups. The investigation of the pre-chamber is focused on the position of the spark within the pre-chamber. Spark locations close to the orifice and close to the opposite wall as well as in the middle of the pre-chamber were tested and flame evolution and pressure history were studied.

Bus drivers are a group at risk of often suffering from musculoskeletal problems, such as low-back pain, while bus passengers on the last-row seats experience accelerations of high values. In this paper, the contribution of K-seat in decreasing the above concern is investigated with a detailed simulation study. The K-seat model, a seat with a suspension that functions according to the KDamper concept, which combines a negative stiffness element with a passive one, is benchmarked against the conventional passive seat (PS) in terms of comfort when applied to different bus users’ seats. More specifically, it is tested in the driver’s and two different passengers’ seats, one from the rear overhang and one from the middle part. For the benchmark shake, both are optimized by applying excitations that correspond to real intercity bus floor responses when it drives over a real road profile.

The INCOLL or INertia COLLection system described in this paper, should meet the requirements for a short transient test, without using any chassis dynamometer. To prove this point not only the background of its principles are described, but also results from its application both to S I engines with and without catalytic converters and to truck diesel engines. Special interest has been devoted to the oxygen sensor and converter efficiency and their response both during warm up and under transient conditions. The simplification of the analyzing equipment and the direct interpretation of the results, have been dealt with, as well as the repeativity of the results achieved. The INCOLL test may also have a potential use as quality test at the end of the production line and as a tool for reliability development as well as research and development within the field. The cost for an INCOLL test is estimated to be around one (1) percent of a normal FTP certification procedure.