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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 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.

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.

Experiments were performed using a Light-Duty, single-cylinder, research engine in which the emissions, fuel consumption and combustion characteristics of two Fischer-Tropsch (F-T) Diesel fuels derived from natural gas and two conventional Diesel fuels (Swedish low sulfur Diesel and European EN 590 Diesel) were compared. Due to their low aromatic contents combustion with the F-T Diesel fuels resulted in lower soot emissions than combustion with the conventional Diesel fuels. The hydrocarbon emissions were also significantly lower with F-T fuel combustion. Moreover the F-T fuels tended to yield lower CO emissions than the conventional Diesel fuels. The low emissions from the F-T Diesel fuels, and the potential for producing such fuels from biomass, are powerful reason for future interest and research in this field.

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.

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.

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.

A single-cylinder engine was operated in HCCI combustion mode with different kinds of commercial fuels. The HCCI combustion was generated by creating a negative valve overlap (early exhaust valve closing combined with late intake valve opening) thus trapping a large amount of residuals (∼ 55%). Fifteen different fuels with high octane numbers were tested six of which were primary reference fuels (PRF's) and nine were commercial fuels or reference fuels. The engine was operated at constant operational parameters (speed/load, valve timing and equivalence ratio, intake air temperature, compression ratio, etc.) changing only the fuel type while the engine was running. Changing the fuel affected the auto-ignition timing, represented by the 50% mass fraction burned location (CA50). However these changes were not consistent with the classical RON and MON numbers, which are measures of the knock resistance of the fuel. Indeed, no correlation was found between CA50 and the RON or MON numbers.

A single cylinder, naturally aspirated, four-stroke and camless (Otto) engine was operated in homogeneous charge compression ignition (HCCI) mode with commercial gasoline. The valve timing could be adjusted during engine operation, which made it possible to optimize the HCCI engine operation for different speed and load points in the part-load regime of a 5-cylinder 2.4 liter engine. Several tests were made with differing combinations of speed and load conditions, while varying the valve timing and the inlet manifold air pressure. Starting with conventional SI combustion, the negative valve overlap was increased until HCCI combustion was obtained. Then the influences of the equivalence ratio and the exhaust valve opening were investigated. With the engine operating on HCCI combustion, unthrottled and without preheating, the exhaust valve opening, the exhaust valve closing and the intake valve closing were optimized next.

A diesel engine model, designed for studying events during automated gear shifting in a heavy duty truck is presented. It will be used for developing and evaluating powertrain control strategies. The deceleration in engine speed to the new synchronous speed, during an upshift, is of special intereset. The straightforward approach is to cut fuel and wait for the engine to slow down due to friction and pumping losses. In many cases, this approach is too slow, and the engine compression brake needs to be activated. The engine model, assuming quasi-steady, bidirectional thermodynamic flow with constant specific heat capacities, is implemented using Modelica. A simple model of the hydraulic circuit that governs the activation of the compression brake mode is incorporated in the model. Problems related to the simulation of the engine brake systems are discussed. They are handled by empirical correction factors. Measurements from rapid engine speed decelerations are used for verification.

A complex chemistry model of reduced size (65 species and 268 reaction steps) derived on the basis of n-heptane auto-ignition kinetics, low hydrocarbon oxidation chemistry, poly-aromatic hydrocarbon (PAH) and NOx formation kinetics together with a phenomenological soot model have been integrated with the KIVA code for multidimensional diesel simulations. A partially stirred reactor model is used to handle the turbulence-chemistry interaction. The results obtained from numerical simulations for a direct-injection (DI) diesel spray, which is injected into a constant-volume combustion vessel at engine-like conditions, show that the approach is able to reproduce the transient diesel auto-ignition and combustion processes as observed in many optical imaging studies. The simulated results indicate that the auto-ignition of DI diesel spray occurs at a lean site close to the mean stoichiometric line for the cases tested.

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.

This work presents a numerical method for predictions of HC oxidation in the cold turbulent wall jet emerging from the piston top land crevice in an S.I. engine, using a complex chemical reaction model. The method has been applied to an engine model geometry with the aim to predict the HC oxidation rate under engine - relevant conditions. According to the simulation a large amount of HC survives oxidation due to the long ignition delay of the wall jet emitted from the crevice. This ignition delay, in turn depends mainly on chemical composition and temperature of the gas mixture in the crevice and also on the temperature distribution in the cylinder boundary layer.

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.

The objective of the study presented here was to examine the possibility of simultaneously reducing soot and nitrogen oxide (NOx) emissions from a heavy duty diesel engine, using very high levels of EGR (exhaust gas recirculation). The investigation was carried out using a 2 litre DI single cylinder diesel engine. Two different EGR strategies were examined. One entailed maintaining a constant charge air pressure with a varied exhaust back pressure in order to change the amount of EGR. In the other strategy a constant pressure difference was maintained over the engine, resulting in different equivalence ratios at similar EGR levels. EGR levels of 60 % or more significantly reduced both soot and NOx emissions at 25 % engine load with constant charge air pressure and increasing exhaust back pressure. However, combustion under these conditions was incomplete, resulting in high emissions of carbon monoxide (CO), unburned hydrocarbons (HC) and high fuel consumption.

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.

Until recently, the application of the detailed chemistry approach as a predictive tool for engine modeling has been sort of a “taboo” for different reasons, mainly because of an exaggerated rigor to the chemistry/turbulence interaction modeling. In terms of this ideology, if the interaction cannot be simulated properly, the detailed chemistry approach makes no sense. The novelty of the proposed methodology is the coupling of a generalized partially stirred reactor, PaSR, model with the high efficiency numerics to treat detailed oxidation kinetics of hydrocarbon fuels. In terms of this approach, chemical processes are assumed to proceed in two successive steps: the reaction follows after the micro-mixing is completed on a sub-grid scale.

The purpose of this paper is to assess the influence of fuel properties on cycle-resolved exhaust hydrocarbons and investigate the sources of hydrocarbon (HC) emissions in a direct injection stratified charge (DISC) SI engine. The tested engine is a single cylinder version of a commercial DISC engine that uses a wall guided combustion system. The HC emissions were analyzed using both a fast flame ionization detector (Fast FID) and conventional emission measurement equipment. Three fuels were compared in the study: iso-Pentane, iso-Octane and a gasoline of Japanese specification. The measurements were conducted at part-load, where the combustion is in stratified mode. The start of injection (SOI) was altered in relation to the series calibration to vary the mixture preparation time, the time from SOI to ignition. The ignition timing was set at maximum brake torque (MBT) for each test.

An advanced catalytic exhaust after-treatment system addresses the problem of NOX emissions from heavy-duty diesel trucks, relying on real-time catalyst modelling. The system consists of de-NOX catalysts, a device for injection of a reducing agent (diesel fuel) upstream the catalysts, and computer programmes to control the injection of the reducing agent and to model the engine and catalysts in real time. Experiments with 5 different air-assisted injectors were performed to determine the effect of injector design on the distribution of the injected diesel in the exhaust gas stream. A two-injector set-up was investigated to determine whether system efficiency could be increased without increasing the amount of catalyst or the amount of reducing agent necessary for the desired outcome. The results were verified by performing European standard transient cycle tests as well as stationary tests.

Brake judder is a forced vibration occurring in different types of vehicles. The frequency of the vibration can be as high as 500 Hz, but usually remains below 100 Hz and often as low as 10-20 Hz. The driver experiences judder as vibrations in the steering wheel, brake pedal and floor. For high frequency brake judder, the structural vibrations are accompanied by a sound. In the present paper the vibration amplitude (in terms of angular deflection, velocity or acceleration) of the caliper has been used as a quantitative measure of the vibration level. Brake Torque Variation (BTV) is the primary excitation for the vibrations. The mechanical effects generating BTV are linked not only to manufacturing tolerances but also to tribological issues. Uneven disc wear as well as Thermo-Elastic Instabilities (TEI) can lead to judder. Especially the effect of the wheel suspension on the transfer of the vibrations to the driver has to be considered.