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Correct simulations of rotating wheels are essential for accurate aerodynamic investigations of passenger vehicles. Therefore, modern automotive wind tunnels are equipped with five-belt moving ground systems with wheel drive units (WDUs) connected to the underfloor balance. The pressure distribution on the exposed areas of the WDU belts results in undesired lift forces being measured which must be considered to obtain accurate lift values for the vehicle. This work investigates the parasitic WDU lift for various configurations of a crossover SUV using numerical simulations that have been correlated to wind tunnel data. Several parameters were considered in the investigation, such as WDU size, WDU placement, tyre variants and vehicle configurations. The results show that the parasitic lift is more sensitive to the width than the length of the WDU. However, the belt length is also important to consider, especially if the wheel cannot be placed centred.

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.

Wind tunnels are an essential tool in vehicle development. To simulate the relative velocity between the vehicle and the ground, wind tunnels are typically equipped with moving ground and boundary layer control systems. For passenger vehicles, wind tunnels with five-belt systems are commonly used as a trade-off between accurate replication of the road conditions and uncertainty of the force measurements. To allow different tyre sizes, the wheel drive units (WDUs) can often be fitted with belts of various widths. Using wider belts, the moving ground simulation area increases at the negative cost of larger parasitic lift forces, caused by the connection between the WDUs and the balance. In this work, a crossover SUV was tested with 280 and 360mm wide belts, capturing forces, surface pressures and flow fields. For further insights, numerical simulations were also used.

The high-pressure isobaric combustion has been proposed as the most suitable combustion mode for the double compre4ssion expansion engine (DCEE) concept. Previous experimental and simulation studies have demonstrated an improved efficiency compared to the conventional diesel combustion (CDC) engine. In the current study, isobaric combustion was achieved using a single injector with multiple injections. Since this concept involves complex phenomena such as spray to spray interactions, the computational models were extensively validated against the optical engine experiment data, to ensure high-fidelity simulations. The considered optical diagnostic techniques are Mie-scattering, fuel tracer planar laser-induced fluorescence (PLIF), and natural flame luminosity imaging. Overall, a good agreement between the numerical and experimental results was obtained.

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 potential of 48V Mild Hybrid is promising in meeting the present and future CO2 legislations. There are various system layouts for 48V hybrid system including P0, P1, P2. In this paper, P2 architecture is used to investigate the effects of water injection benefits in a mild hybrid system. Electrification of the conventional powertrain uses the benefits of an electric drive in the low load-low speed region where the conventional SI engine is least efficient and as the load demand increases the IC Engine is used in its more efficient operating region. Engine downsizing and forced induction trend is popular in the hybrid system architecture. However, the engine efficiency is limited by combustion knocking at higher loads thus ignition retard is used to avoid knocking and fuel enrichment becomes must to operate the engine at MBT (Maximum Brake Torque) timing; in turn neutralizing the benefits of fuel savings by electrification.

Approximately 25 % of a passenger vehicle’s aerodynamic drag comes directly or indirectly from its wheels, indicating that the rim geometry is highly relevant for increasing the vehicle’s overall energy efficiency. An extensive experimental study is presented where a parametric model of the rim design was developed, and statistical methods were employed to isolate the aerodynamic effects of certain geometric rim parameters. In addition to wind tunnel force measurements, this study employed the flowfield measurement techniques of wake surveys, wheelhouse pressure measurements, and base pressure measurements to investigate and explain the most important parameters’ effects on the flowfield. In addition, a numerical model of the vehicle with various rim geometries was developed and used to further elucidate the effects of certain geometric parameters on the flow field.

Due to stricter emission regulations and more environmental awareness, the powertrain systems are moving toward higher fuel efficiency and lower emissions. In response to these pressing needs, new technologies have been designed and implemented by manufacturers. As a result of increasing complexity of the powertrain systems, their control and optimization become more and more challenging. Virtual powertrain calibration, also known as model-based calibration, has been introduced to transfer a part of test bench testing into a virtual environment, and hence considerably reduce time and cost of product development process while increasing the product quality. Nevertheless, virtual calibration has not yet reached its full potential in industrial applications. Volvo Penta has recently developed a virtual test cell named VIRTEC, which is used in an ongoing pilot project to meet the Stage V emission standards.

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.

Under a global impulse for less man-made emissions, the automotive manufacturers search for innovative methods to reduce the fuel consumption and hence the CO2-emissions. Aerodynamics has great potential to aid the emission reduction since aerodynamic drag is an important parameter in the overall driving resistance force. As vehicles are considered bluff bodies, the main drag source is pressure drag, caused by the difference between front and rear pressure. Therefore increasing the base pressure is a key parameter to reduce the aerodynamic drag. From previous research on small-scale and full-scale vehicles, rear-end extensions are known to have a positive effect on the base pressure, enhancing pressure recovery and reducing the wake area. This paper investigates the effect of several parameters of these extensions on the forces, on the surface pressures of an SUV in the Volvo Cars Aerodynamic Wind Tunnel and compares them with numerical results.

It is well known that wheels are responsible for a significant amount of the total aerodynamic drag of passenger vehicles. Tyres, and mostly rims, have been the subject of research in the automotive industry for the past years, but their effect and interaction with each other and with the car exterior is still not completely understood. This paper focuses on the use of CFD to study the effects of tyre geometry (tyre profile and tyre tread) on road vehicle aerodynamics. Whenever possible, results of the numerical computations are compared with experiments. More than sixty configurations were simulated. These simulations combined different tyre profiles, treads, rim designs and spoke orientation on two car types: a sedan and a sports wagon. Two tyre geometries were obtained directly from the tyre manufacturer, while a third geometry was obtained from our database and represents a generic tyre which covers different profiles of a given tyre size.

Semi-active suspension systems for ground vehicles have been the focus of research for several years as they offer improvements in vehicle comfort and handling. This kind of suspension has attracted more interest compared to active suspension systems especially due to lower cost and energy consumption. In this paper the capabilities of a semi-active front axle suspension are investigated for a commercial vehicle. A half-truck model of a 4x2 tractor and semitrailer combination is developed in Matlab/Simulink for this purpose. Also, a 2 DOF roll plane model is considered to capture the roll motion of the vehicle body mass. Employing the above-mentioned models, results from on-off and continuous variable semi-active damping systems are compared to the ones from the passive suspension system according to ride comfort and handling safety characteristics.

Efforts towards ever more energy efficient passenger cars have become one of the largest challenges of the automotive industry. This involves numerous different fields of engineering, and every finished model is always a compromise between different requirements. Passenger car aerodynamics is no exception; the shape of the exterior is often dictated by styling, engine bay region by packaging issues etcetera. Wheel design is also a compromise between different requirements such as aerodynamic drag and brake cooling, but as the wheels and wheel housings are responsible for up to a quarter of the overall aerodynamic drag on a modern passenger car, it is not surprising that efforts are put towards improving the wheel aerodynamics.

For cost-beneficial reasons simulations with computer manikins have been increasingly used in the automotive industry for prediction of ergonomics problems before the product and work place exist in physical form. The main purpose of ergonomics simulations is to apply biomechanical models and data to assess the acceptability of the physical work load, e.g. working postures, visibility, clearance etc., which could result in requirements to change the design of the product. The aim is to improve ergonomics conditions in manual assembly and to promote a better product quality through improved assemblability (ease of assembly). Many studies have shown a clear correlation between assembly ergonomics and product quality and that poor assembly ergonomics result in impaired product quality and in decreased productivity. Nevertheless, there are remaining difficulties in achieving acceptance for changes of product and production solutions because of poor assembly ergonomics.

The drag from the underbody, including wheels and wheel housing, constitutes a significant amount of the total aerodynamic drag of heavy vehicles. A correct simulation of the underbody boundary conditions, including rotating wheels and moving ground, has turned out to be of great importance in the minimising of the aerodynamic drag. In the current study several front wheel housing design parameters have been evaluated using Computational Fluid Dynamics (CFD). Design concepts, like enclosed inner wheel housings, underbody panel and wheel housing ventilation, were evaluated by flow analysis and comparison of the drag force contribution. It was shown that changes to the wheel housing geometry had an important impact on the local flow field and force distribution. The total drag of the vehicle decreased with reduced wheel housing volume and wheel housing ventilation can reduce the aerodynamic drag significantly provided it is designed properly.

Moving ground systems with rotating wheels have been used in wind tunnel tests during the last decades. Several studies on the effects of rotating wheels and the importance of wheel aerodynamics have been published. It is well known that both the local flow field and the global aerodynamic forces are affected by rotation of the wheels. Different studies indicate that the most significant effect from rotating the wheels is interference effects between the rear wheels and the underbody and vehicle base [1], [2]. A detailed flow field investigation around the wheels in close proximity to the vehicle has been performed on a passenger car in the Volvo Aerodynamic Wind Tunnel. Two omnidirectional 12-hole pressure probes were traversed in a number of planes close to the wheels. Effects of changing different parameters such as ground simulation and rim geometry were investigated. The local flow field has been scrutinised and related to the global aerodynamic properties of the vehicle.

In the 1955 Le Mans race the worst crash in motor racing history occurred and this accident would change the face of motor racing for decades. After the crash numerous investigations on the disaster were performed, and fifty years after some interesting books were launched on the subject. However, a number of key questions remain unsolved; and one open area is the influence of aerodynamics on the scenario, since the Mercedes-Benz 300 SLR involved in the crash was equipped with an air-brake and its influence on the accident is basically unknown. This work may be considered as a first attempt to establish CFD as a tool to aid in resolving aerodynamic aspects in motor sport accidents and in the present paper, CFD has been used to investigate the aerodynamics and estimate the drag and lift coefficients of the Mercedes-Benz 300 SLR used in the Le Mans race of 1955.

This paper describes a process membership protocol for distributed real-time systems that use both time-triggered and event-triggered message passing for communication between its processing nodes (ECUs). TTCAN and FlexRay are examples of communication networks that support such systems. The membership protocol supports redundancy management in architectures where distributed applications such as braking, stability control, and collision mitigation share a common set of processing nodes. We assume that each such application consists of several processes executing on different nodes and that each node executes processes belonging to different applications. The protocol allows a group of co-operating processes to establish a consistent view of each other's operational status, i.e. whether they function correctly or not.

Computational simulations of the spray combustion and emissions formation processes in a heavy-duty DI diesel engine and in a small-bore DI diesel engine with a complicated injection schedule were performed by using the modified KIVA3V, rel. 2 code. Some initial parameter sets varying engine operating conditions, such as injection pressure, injector nozzle diameter, EGR load, were examined in order to evaluate their effects on the engine performance. Full-scale combustion chamber representations on 360-deg, Cartesian and polar, multiblock meshes with a different number of sprays have been used in the modelling unlike the conventional approach based on polar sector meshes covering the region around one fuel spray. The spray combustion phenomena were simulated using the detailed chemical mechanism for diesel fuel surrogate (69 species and 306 reactions).

The aim of this study was to examine the influence of computer manikin users' background and knowledge for the results of a computer manikin simulation. Subjects taking part in the study were either production engineers or ergonomists. A manual task that presented production and ergonomics problems was used. The task was simulated prior to the subjects' sessions, using the computer manikin software Jack. During the sessions, the animated simulation was shown to the test subject. Results show that there are differences in how production engineers and ergonomists interpret results from a manikin simulation. Depending on the user's background, certain aspects that are difficult to visualise with the computer manikin were interpreted differently, regarding e.g. detected problems and holistic perspectives.