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Technical Paper

A 1D Method for Transient Simulations of Cooling Systems with Non-Uniform Temperature and Flow Boundaries Extracted from a 3D CFD Solution

The current work investigates a method in 1D modeling of cooling systems including discretized cooling package with non-uniform boundary conditions. In a stacked cooling package the heat transfer through each heat exchanger depends on the mass flows and temperature fields. These are a result of complex three-dimensional phenomena, which take place in the under-hood and are highly non-uniform. A typical approach in 1D simulations is to assume these to be uniform, which reduces the authenticity of the simulation and calls for additional calibrations, normally done with input from test measurements. The presented work employs 3D CFD simulations of complete vehicle in STAR-CCM+ to perform a comprehensive study of mass-flow and thermal distribution over the inlet of the cooling package of a Volvo FM commercial vehicle in several steady-state operating points.
Technical Paper

A Model of Turbocharged Engines as Dynamic Drivetrain Members

An engine model for use in computer simulation of transient behavior in drivetrain and vehicle systems is presented. Two elements, important for deviation (e.g. turbo-lag) from steady state characteristics, are the inertia of the supercharging unit (turbo shaft) and the fuel injection control system. No extensive combustion calculations are carried out within the model. Instead it uses condensed results from existing combustion models and measurements. The model is semi-empirical. Some of the engine specific properties needed for simulation are (e.g. for a turbocharged diesel): engine data in steady state operation, mappings of compressor and turbine performance, inertia of the engine components condensed to the crankshaft, turbo shaft inertia, displacement, compression ratio and the essentials of the fuel injection control strategy. Input parameters to the computer program based on the model are accelerator pedal position and external torque acting on the flywheel.
Technical Paper

Achieving a Cost Efficient and Dependability Scalable System for Automotive Applications, Using the QRcontrol Communication Protocol

This paper presents methods to easily increase the dependability and fault tolerance of a scalable bit-oriented cyclic protocol, QRcontrol, utilizing TDMA technique. Minor changes to the protocol software and built-in techniques in the controller can give increased dependability for changing requirements on the system. These techniques include for example enabling of double buses, checksums for a node or a whole TDMA cycle, bus guardians and different fault detection mechanisms for some or all nodes in the cluster. The concept can be assigned to a very broad range of applications, from body electronics in cars to “By-Wire” applications with the highest dependability requirements.
Technical Paper

Analysis of Transient Compressible Gas Jets Using High Speed Schlieren Imaging

Transient compressible gas jets, as encountered in direct injection gas fuel engines, have been examined using Schlieren visualization. Helium has been injected into air in a pressure chamber to create the jets examined. The structure of the jets is studied from the mean and coefficient of variation of the penetration length, jet width and jet angle. The quantities are calculated by digital image processing of Schlieren images captured with a high-speed camera. Injection pressure and chamber pressure have been varied to determine whether they have an effect on the response variables. Design of experiments methods have been used to develop the scheme employed in performing the experiments. The mean normalized penetration length of the jets is found to scale with injection to chamber pressure ratio and is in agreement with a momentum conserving relation given in the literature. The dispersion of the penetration length has been found to be in agreement with a normal distribution.
Technical Paper

Automated Flexible Tooling for Wing Box Assembly: Hexapod Development Study

The ability to adapt to rapidly evolving market demands continues to be the one of the key challenges in the automation of assembly processes in the aerospace industry. To meet this challenge, industry and academia have made efforts to automate flexible fixturing. LOCOMACHS (Low Cost Manufacturing and Assembly of Composite and Hybrid Structures) - a European Union funded project with 31 partners - aims to address various aspects of aero-structure assembly with a special attention directed to the development of a new build philosophy along with relevant enabling technologies. This paper aims to present the results on the developed wing box build philosophy and the integration of automated flexible tooling solutions into the assembly process. The developed solution constitutes the use of synchronized hexapods for the assembly of front spar to upper cover whereas another hexapod was developed to install a rib by using of a force feedback sensor.
Technical Paper

Battery Parameter Estimation from Recorded Fleet Data

Existing battery parameter model structures are evaluated by estimating model parameters on real driving data applying standard system identification methods. Models are then evaluated on the test data in terms of goodness of fit and RMSE in voltage predictions. This is different from previous battery model evaluations where a common approach is to train parameters using standardized tests, e.g. hybrid pulse-power capability (HPPC), with predetermined charge and discharge sequences. Equivalent linear circuit models of different complexity were tested and evaluated in order to identify parameter dependencies at different state of charge levels and temperatures. Models are then used to create voltage output given a current, state of charge and temperature. The average accuracy of modelling the DC bus voltage provides a model goodness of fit average higher than 90% for a single RC circuit model.
Technical Paper

CFD Modelling of Gasoline Sprays

A comprehensive model for sprays emerging from high pressure swirl injectors for GDI engine application has been developed. The primary and secondary atomization mechanism as well as the evaporation process both in standard and superheated conditions are taken into account. The spray modelling after the injection is based on the Liquid Instability Sheet Atomization (LISA) approach, modified to correctly predict the liquid sheet thickness at the breakup length. The effect of different values of the superheat degree on evaporation and impact on the spray distribution and fuel-air mixing is analyzed. Comparisons with experimental data show good agreements under atmospheric conditions and with different superheated degrees, while some discrepancies occur under higher ambient pressures.
Technical Paper

Conceptual Design of Distributed by-Wire Systems

A design method for ultra-dependable control-by-wire systems is presented here. With a top-down approach, exploiting the system's intrinsic redundancy combined with a scalable software redundancy, it is possible to meet dependability requirements cost-effectively. The method starts with the system's functions, which are broken down to the basic elements; task, sensor or actuator. A task graph shows the basic elements interrelationships. Sensor and actuator nodes form a non-redundant hardware architecture. The functional task-graph gives input when allocating software on the node architecture. Tasks are allocated to achieve low inter-node communication and transient fault tolerance using scalable software redundancy. Hardware is added to meet the dependability requirements. Finally, the method describes fault handling and bus scheduling. The proposed method has been used in two cases; a fly-by-wire aircraft and a drive-by-wire car.
Technical Paper

Early Risk Identification and Cost-Benefit Analyses through Ergonomics Simulation

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.
Technical Paper

Effect of Injection Parameters on Auto-Ignition and Soot Formation in Diesel Sprays

A validation study of the numerical model of n-heptane spray combustion based on experimental constant-volume data [1] was done, by comparing auto-ignition delays for different pre - turbulence levels and initial temperatures, flame contours, and soot distributions under Diesel-like conditions. The basic novelty of the methodology developed in [2] - [3] is the implementation of the partially stirred reactor (PaSR) model accounting for detailed chemistry / turbulence interactions. It is based on the assumption that the chemical processes proceed in two successive steps: micro mixing, simulated on a sub - grid scale, is followed by the reaction act. When the all Re number RNG k-ε or LES models are employed, the micro mixing time can be consistently defined giving the combustion model a “well-closed” form incorporated into the KIVA-3V code.
Technical Paper

Effect of Rear-End Extensions on the Aerodynamic Forces of an SUV

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.
Technical Paper

Experimental and Numerical Investigations of the Base Wake on an SUV

With the increase in fuel prices and the increasingly strict environmental legislations regarding CO₂ emissions, reduction of the total energy consumption of our society becomes more important. Passenger vehicles are partly responsible for this consumption due to their strong presence in the daily life of most people. Therefore reducing the impact of cars on the environment can assist in decreasing the overall energy consumption. Even though several fields have an impact on a passenger car's performance, this paper will focus on the aerodynamic part and more specifically, the wake behind a vehicle. By definition a car is a bluff body on which the air resistance is for the most part driven by pressure drag. This is caused by the wake these bodies create. Therefore analyzing the wake characteristics behind a vehicle is crucial if one would like to reduce drag.
Technical Paper

Heat Release in the End-Gas Prior to Knock in Lean, Rich and Stoichiometric Mixtures With and Without EGR

SI Engine knock is caused by autoignition in the unburnt part of the mixture (end-gas) ahead of the propagating flame. Autoignition of the end-gas occurs when the temperature and pressure exceeds a critical limit when comparatively slow reactions-releasing moderate amounts of heat-transform into ignition and rapid heat release. In this paper the difference in the heat released in the end-gas-by low temperature chemistry-between lean, rich, stochiometric, and stoichiometric mixtures diluted with cooled EGR was examined by measuring the temperature in the end-gas with Dual Broadband Rotational CARS. The measured temperature history was compared with an isentropic temperature calculated from the cylinder pressure trace. The experimentally obtained values for knock onset were compared with results from a two-zone thermodynamic model including detailed chemistry modeling of the end-gas reactions.
Technical Paper

Holistic Approach for Improved Safety Including a Proposal of New Virtual Test Conditions of Small Electric Vehicles

In the next 20 years the share of small electric vehicles (SEVs) will increase especially in urban areas. SEVs show distinctive design differences compared to traditional vehicles. Thus the consequences of impacts of SEVs with vulnerable road users (VRUs) and other vehicles will be different from traditional collisions. No assessment concerning vehicle safety is defined for vehicles within European L7e category currently. Focus of the elaborated methodology is to define appropriate test scenarios for this vehicle category to be used within a virtual tool chain. A virtual tool chain has to be defined for the realization of a guideline of virtual certification. The derivation and development of new test conditions for SEVs are described and are the main focus of this work. As key methodology a prospective methodical analysis under consideration of future aspects like pre-crash safety systems is applied.
Technical Paper

Identifying Time-Consuming Human Modelling Tool Activities

The aim of this study was to identify and measure time-consuming human modelling tool activities. Five human modelling tool users at Volvo were observed for five days each. The results showed a wide distribution of both indirect and direct working tasks, as well as non-value added tasks such as waiting time. Most of the activities identified appear to be necessary to perform human modelling simulations of high quality. However, the time distribution could be questioned to some extent. There are many activities associated with communication, including a variety of contacts and meetings, where there appears to be potential to increase efficiency.
Technical Paper

Inertia Collection Applied to Vehicle Emissions

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.
Technical Paper

Intrinsic Design of Experiments for Modeling of Internal Combustion Engines

In engine research and development there are often different engine parameters that produce similar effects on the end-point results. When calibrating modern engines, a huge number of parameters needs to be set, which also includes compensation parameters for model imperfections. In this context, simpler, more robust, and physically based models should be beneficial both for calibration work load and powertrain performance. In this study, we present an experimental methodology that uses intermediate (“intrinsic”) variables instead of engine parameters. By using simple thermodynamic models, the engine parameters EGR, IVC, and PBoost could be translated into oxygen concentration, temperature and gas density at the start of injection. The reason for this transformation of data is to “move” the Design of Experiment (DoE) closer to the situation of interest (i.e. the combustion) and to be able to construct simpler and more physically based models.
Technical Paper

Investigation of Spark Position Effects in a Small Pre-chamber on Ignition and Early Flame Propagation

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.
Journal Article

Investigation of the Influence of Tyre Geometry on the Aerodynamics of Passenger Cars

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.
Technical Paper

It's in the Eye of the Beholder: Who Should be the User of Computer Manikin Tools?

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.