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Technical Paper

A Can Communications Concept With Guaranteed Message Latencies

A new in-vehicle communication concept for CAN networks has been developed, taking into account recent findings from real-time research. The concept is characterized by three impo features: (i) Ability to guarantee the real-time performance of the network already at the design stage, thus significantly reducing the need for testing; (ii) Built-in flexibility enabling the vehicle manufacturer to upgrade the network in the pre-production phase of a project as well as in the aftermarket; (iii) Low use of available resources, thus saving cost compared to other solutions. The concept is successfully used in all larger Volvo cars from model year 1999.
Journal Article

A Compact Silencer for the Control of Compressor Noise

Current trends for IC-engines are driving the development of more efficient engines with higher specific power. This is true for both light and heavy duty vehicles and has led to an increased use of super-charging. The super-charging can be both in the form of a single or multi-stage turbo-charger driven by exhaust gases, or via a directly driven compressor. In both cases a possible noise problem can be a strong Blade Passing Frequency (BPF) typically in the kHz range and above the plane wave range. In this paper a novel type of compact dissipative silencer developed especially to handle this type of problem is described and optimized. The silencer is based on a combination of a micro-perforated (MPP) tube backed by a locally reacting cavity. The combined impedance of micro-perforate and cavity is chosen to match the theoretical optimum known as the Cremer impedance at the mid-frequency in the frequency range of interest.
Technical Paper

A High Resolution 3D Complete Engine Heat Balance Model

The focus on engine thermal management is rapidly increasing due to the significant effect of heat losses on fuel consumption, engine performance and emissions. This work presents a time resolved, high resolution 3D engine heat balance model, including all relevant components. Notably, the model calculates the conjugated heat transfer between the solid engine components, the coolant and the oil. Both coolant and oil circuits are simultaneously resolved with a CFD solver in the same finite volume model as the entire engine solid parts. The model includes external convection and radiation. The necessary boundary conditions of the thermodynamic cycle (gas side) are mapped from a calibrated 1D gas exchange model of the same engine. The boundary conditions for the coolant and at the oil circuits are estimated with 1D models of the systems. The model is calibrated and verified with measurement data from the same engine as modeled.
Technical Paper

A Method for Estimating the Benefit of Autonomous Braking Systems Using Traffic Accident Data

One way of avoiding crashes or mitigating the consequences of a crash is to apply an autonomous braking system. Quantifying the benefit of such a system in terms of injury reduction is a challenge. At the same time it is a fundamental input into the vehicle development process. This paper describes a method to estimate the effectiveness of reducing speed prior to impact. A holistic view of quantifying the benefit is presented, based on existing real life crash data and basic dynamic theories. It involves a systematic and new way of examining accident data in order to extract information concerning pre-crash situations. One problem area when implementing collision mitigation systems is being able to achieve sufficient target discrimination. The results from the case study highlight frontal impact situations from real world accident data that have the greatest potential in terms of improving accident outcome.
Technical Paper

A Mild Hybrid SIDI Turbo Passenger Car Engine with Rankine Waste Heat Recovery

In the strive for more fuel-efficient vehicles all possible measures are considered to increase the efficiency of the combustion engine. 48V mild hybrid technology is one such measure; SIDI (Spark Ignited Direct Injection) engines with Miller technology another, while recovering energy from the engine waste heat (WHR) is yet an option to increase fuel conversion efficiency. Here, for the first time, we will publish the results from an advanced engineering project at Volvo Cars including all these components. We have successfully built an ethanol based Rankine system around a 4-cylinder, 2.0 litre SIDI-engine, including 48V mild hybrid technology. The Rankine system uses the engine exhaust as heat source, while the expansion of the ethanol steam occurs in an axial piston expander coupled both electrically to the hybrid system and mechanically to the engine crankshaft.
Technical Paper

A Reference Architecture for Infotainment Systems

Volvo Car Corporation has developed a Reference Architecture for PAG1 Infotainment Systems. A Reference Architecture is an architecture scoping over more than a single system, i.e. an architecture aimed for a family of systems. The Infotainment Reference Architecture has since 2001 been successfully applied for the PAG family which so far covers the infotainment systems of Volvo XC90, Volvo S40/V50, Jaguar XK, Aston Martin DB9 and the brand new Volvo S80. In 1999, the system design departments started up with the clear objective to develop a system solution aiming for the PAG infotainment system family. The work was carried out according to the established development process at Volvo Cars. A year later a discouraging design review was performed. The number of involved functions, the level of function interaction and the distribution of functionalities between ECUs resulted in a non-manageable system solution.
Technical Paper

A Semiconductor Gas Sensor Array for the Detection of Gas Emissions from Interior Trim Materials in Automobiles

The principles of an electronic nose are described briefly. It is shown how a sensor array in combination with pattern recognition software can be used for quality control and classification of car interior trim materials. Anomalies such as bad smelling leather and carpet are shown as outliers. The results are consistent with GC-MS TVOC measurements as well as with data from a human sensory panel. More needs to be done, however, regarding the sensor stability in particular before the sensor array can be used for routine classification of the trim materials.
Technical Paper

A Structure and Calibration Method for Data-Driven Modeling of NOX and Soot Emissions from a Diesel Engine

The development and implementation of a new structure for data-driven models for NOX and soot emissions is described. The model structure is a linear regression model, where physically relevant input signals are used as regressors, and all the regression parameters are defined as grid-maps in the engine speed/injected fuel domain. The method of using grid-maps in the engine speed/injected fuel domain for all the regression parameters enables the models to be valid for changes in physical parameters that affect the emissions, without having to include these parameters as input signals to the models. This is possible for parameters that are dependent only on the engine speed and the amount of injected fuel. This means that models can handle changes for different parameters in the complete working range of the engine, without having to include all signals that actually effect the emissions into the models.
Technical Paper

A Study of Ground Simulation-Correlation between Wind-Tunnel and Water-Basin Tests of a Full-Scale Car

The aerodynamic properties of a full-scale car have been investigated in a wind-tunnel with upstream boundary layer suction, and in a water-basin where the car was rolling on the bottom. Measurements were carried out of the drag and lift forces, the static pressure distribution on the car body and the total head distribution between the car and the ground. By comparing data from the tunnel and the basin the ground simulation technique could be evaluated. The measured drag coefficients were found to be very similar in both facilities, while the absolute values of the lift coefficients were considerably higher in the tunnel. Lift differences due to configuration changes of the upperbody were essentially the same in the two facilities, while changes of the underbody caused smaller lift differences in the tunnel. In the project the water-basin technique was thoroughly investigated and proven.
Journal Article

A Study on Acoustical Time-Domain Two-Ports Based on Digital Filters with Application to Automotive Air Intake Systems

Analysis of pressure pulsations in ducts is an active research field within the automotive industry. The fluid dynamics and the wave transmission properties of internal combustion (IC) engine intake and exhaust systems contribute to the energy efficiency of the engines and are hence important for the final amount of CO₂ that is emitted from the vehicles. Sound waves, originating from the pressure pulses caused by the in- and outflow at the engine valves, are transmitted through the intake and exhaust system and are an important cause of noise pollution from road traffic at low speeds. Reliable prediction methods are of major importance to enable effective optimization of gas exchange systems. The use of nonlinear one-dimensional (1D) gas dynamics simulation software packages is widespread within the automotive industry. These time-domain codes are mainly used to predict engine performance parameters such as output torque and power but can also give estimates of radiated orifice noise.
Technical Paper

Accuracy and Speed for Scale-Resolving Simulations of the DrivAer Reference Model

In aerodynamic development of ground vehicles, the use of Computational Fluid Dynamics (CFD) is crucial for improving the aerodynamic performance, stability and comfort of the vehicle. Simulation time and accuracy are two key factors of a well working CFD procedure. Using scale-resolving simulations, accurate predictions of the flow field and aerodynamic forces are possible, but often leads to long simulation time. For a given solver, one of the most significant aspects of the simulation time/cost is the temporal resolution. In this study, this aspect is investigated using the realistic vehicle model DrivAer with the notchback geometry as the test case. To ensure a direct and accurate comparison with wind tunnel measurements, performed at TU Berlin, a large section of the wind tunnel is included in the simulation domain. All simulations are performed at a Reynolds number of 3.12 million, based on the vehicle length.
Technical Paper

Accuracy in Flow Simulations of Climate Control - Part 2: The Passenger Compartment

Computational fluid dynamics has been used to study the flow pattern in a Volvo S80 passenger compartment. The main purpose of this work is to secure a method for future use of CFD in developing climate control systems in cars. The effects of mesh resolution and mesh size were studied by varying the number of cells from 1 million to approximately 5 million. It was found that at least 2 million cells are needed to approach a mesh size independent solution. The other focus of this study was the outlet boundary conditions. Since a passenger compartment is not air tight, outlets were assumed to be around doors, through the floor, through the backseat, as well as the evacuation at the rear of the passenger compartment. It can be seen that the solution is only sensitive to drastic changes in the leakage.
Technical Paper

Accuracy in Flow Simulations of Climate Control-Part 1: The Air Distribution System

Flow simulations of an air distribution system have been carried out using the CFD code FLUENT/UNS [1]. The purpose of this study is to validate this complex flow problem versus experimental data. Two modes of the climate system are investigated; the Ventilation mode and the Floor/Defroster mode. The complete geometrical model contains all ducts, central unit, heat exchangers, defroster and nozzles of the air distribution system. A high level of geometrical detailing in the mesh, consisting of 2.1 - 3.3 million cells, is used. The study shows that CFD has a potential to give reliable results, even for complex systems, like air distribution systems, if used in a controlled manner.
Technical Paper

Acoustic One-Dimensional Compressor Model for Integration in a Gas-Dynamic Code

An acoustic one-dimensional compressor model has been developed. This model is based on compressor map information and it is able to predict how the pressure waves are transmitted and reflected by the compressor. This is later on necessary to predict radiated noise at the intake orifice. The fluid-dynamic behavior of the compressor has been reproduced by simplifying the real geometry in zero-dimensional and one-dimensional elements with acoustic purposes. These elements are responsible for attenuating or reflecting the pressure pulses generated by the engine. In order to compensate the effect of these elements in the mean flow variables, the model uses a corrected compressor map. Despite of the fact that the compressor model was developed originally as a part of the OpenWAM™ software, it can be exported to other commercial wave action models. An example is provided of exporting the described model to GT-Power™.
Journal Article

Aerodynamic Effects of Different Tire Models on a Sedan Type Passenger Car

Targets for reducing emissions and improving energy efficiency present the automotive industry with many challenges. Passenger cars are by far the most common means of personal transport in the developed part of the world, and energy consumption related to personal transportation is predicted to increase significantly in the coming decades. Improved aerodynamic performance of passenger cars 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 still not 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 tires.
Journal Article

An Evaluation of Different Combustion Strategies for SI Engines in a Multi-Mode Combustion Engine

Future pressures to reduce the fuel consumption of passenger cars may require the exploitation of alternative combustion strategies for gasoline engines to replace, or use in combination with the conventional stoichiometric spark ignition (SSI) strategy. Possible options include homogeneous lean charge spark ignition (HLCSI), stratified charge spark ignition (SCSI) and homogeneous charge compression ignition (HCCI), all of which are intended to reduce pumping and thermal losses. In the work presented here four different combustion strategies were evaluated using the same engine: SSI, HLCSI, SCSI and HCCI. HLCSI was achieved by early injection and operating the engine lean, close to its stability limits. SCSI was achieved using the spray-guided technique with a centrally placed multi-hole injector and spark-plug. HCCI was achieved using a negative valve overlap to trap hot residuals and thus generate auto-ignition temperatures at the end of the compression stroke.
Technical Paper

An Investigation of the Coupling Between the Passenger Compartment and the Trunk in a Sedan

The low frequency acoustic response of the passenger compartment (cavity) in sedans is considered with respect to the coupling between the cavity and the trunk. Both acoustic (via holes in the parcel shelf or behind the backrest of the rear seat), and structural (via the parcel shelf itself, or the panel of the backrest) mechanisms are investigated by both test and CAE. It is found that the peaks in acoustic response of the cavity at low frequencies are due to both acoustic and structural phenomena. However, the acoustic ones can be effectively blocked by proper design of the trim. Recommendations concerning modeling of acoustic effects in sedans are formulated.
Technical Paper

Analytical Methods for Durability in the Automotive Industry - The Engineering Process, Past, Present and Future

In the early days of the automotive industry, durability and reliability were hit or miss affairs, with end-users often being the first to know about any durability problems - and in many cases forming an essential part of the development process. More recently, automotive companies have developed proving ground and laboratory test procedures that aim to simulate typical or severe customer usage. These test procedures have been used to develop the products through a series of prototypes and to prove the durability of the product prior to release in the marketplace. Now, commercial pressures and legal requirements have led to increasing reliance on CAE methods, with fatigue life prediction having a central role in the durability engineering process.
Technical Paper

Applying Design for Six Sigma to the Concept Development of an Automotive HMI

Six Sigma is a development methodology which emphasizes objective evaluations based on facts and measurements. However, for some problems the information is inherently subjective, with large individual variations. Also, in the early development phases, it may be difficult to define measurable metrics that correctly capture the important qualities. The vehicle HMI is a good example of such an application. In this paper, we present experiences of applying Design for Six Sigma methods to the early development phases of an automotive HMI. The focus of the paper is on how to handle uncertainties and vague subjective information.
Technical Paper

Balancing Thermodynamic and Aerodynamic Attributes Through the Use of a Common CFD Model

This paper describes how simultaneous numerical simulation of cooling performance and aerodynamic drag can be used to achieve attribute-balanced solutions. Traditionally at Volvo, evaluation of cooling performance and aerodynamics are done by separate teams using separate models and software. However, using this approach, any project changes can be evaluated in terms of their effect on cooling performance and drag from one single model. This enables the project to make decisions that are optimal in a more global perspective. If several proposals have similar levels of cooling performance, the proposal that yields the lowest overall drag can be chosen, thus reducing the fuel consumption of the vehicle. The first part of the paper discusses the prerequisites for the method in terms of boundary conditions, mesh and solution strategy. For the cooling performance part, the importance of high quality boundary conditions is reviewed.