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Journal Article

xD+1D Catalyst Simulation-A Numerical Study on the Impact of Pore Diffusion

This paper presents a numerical study on the impact of washcoat diffusion on the overall conversion performance of catalytic converters. A comprehensive transient 1D pore diffusion reaction model is embedded in state-of-the-art 1D and 3D catalytic converter models. The pore diffusion model is discussed with its model equations and the applied diffusive transport approaches are summarized. The diffusion reaction model is validated with the help of two available analytical solutions. The impact of basic washcoat characteristics such as pore diameters or thickness on overall conversion performance is investigated by selected 1D+1D calculations. This model is also used to highlight the impact of boundary layer transfer, pore diffusion and reaction on the overall converter conversion performance. The interaction of pore diffusion and flow non-uniformities is demonstrated by 3D+1D CFD simulations.
Technical Paper

Vehicle Thermal Management Simulation Method Integrated in the Development Process from Scratch to Prototype

Abstract In order to meet current and future emission and CO2 targets, an efficient vehicle thermal management system is one of the key factors in conventional as well as in electrified powertrains. Furthermore the increasing number of vehicle configurations leads to a high variability and degrees of freedom in possible system designs and the control thereof, which can only be handled by a comprehensive tool chain of vehicle system simulation and a generic control system architecture. The required model must comprise all relevant systems of the vehicle (control functionality, cooling system, lubrication system, engine, drive train, HV components etc.). For proper prediction with respect to energy consumption all interactions and interdependencies of those systems have to be taken into consideration, i.e. all energy fluxes (mechanical, hydraulically, electrical, thermal) have to be exchanged among the system boundaries accordingly.
Technical Paper

Vehicle Sound Engineering by Modifying Intake / Exhaust Orifice Noise Using Simulation Software

Apart of other aspects, the interior sound of a passenger car brand has to meet customer expectations. For optimizing the sound of a passenger car, target sounds have first to be established via the operating range of the vehicle. For an effective sound engineering approach an objective description and evaluation of vehicle interior sound is beneficial. Such an objective description guarantees the effective and reproducible implementation of the required brand sound in the vehicle development process. In such a process it is necessary to reduce on the one hand annoying undesired noise aspects and to create on the other hand the relevant and necessary noise parameters to meet the target sounds head on.
Journal Article

Use of a Catalytic Stripper as an Alternative to the Original PMP Measurement Protocol

The Particle Measurement Programme (PMP) developed an exhaust particle number measurement protocol that has been adopted by current light duty vehicle emission regulations in Europe. This includes thermal treatment of the exhaust aerosol to isolate solid particles only and a number counting device with a lower cutpoint of 23 nm to avoid measurement of smaller particles that may affect the repeatability of the measurement. In this paper, we examine a potential alternative to the PMP system, where the thermal treatment is replaced by a catalytic stripper (CS). This offers oxidation and not just evaporation of the volatile components. Alternative sampling systems, either fulfilling the PMP recommendations or utilizing a CS, have been explored in terms of their volatile particle removal efficiency. Tests have been conducted on diesel exhaust, diesel equipped with DPF and gasoline direct injection emissions.
Journal Article

Turbocharger Noise Quality Parameters for Efficient TC Noise Assessment and Refinement

Abstract Due to more challenging future emission legislations and the trend towards downsizing, the number of turbocharged (TC) engines, especially petrol engines, is steadily increasing. The usage of TC has high risk to cause different noise phenomena apparent in the vehicle interior which are often perceived as annoying for the passengers. In order to further improve consideration of TC topics in the development, objective judgment and monitoring of TC noise issues is of high importance. Therefore, objective parameters and corresponding tools that are especially focusing on TC noise phenomena have to be developed. One main target of these tools is to deliver an objective TC assessment in an efficient way and with minimum additional effort. Application of the criteria presented in this publication therefore allows acoustic engineers to judge the NVH behavior and annoyance of the TC with respect to its vehicle interior noise contribution.
Technical Paper

Tool Based Calibration with the OBDmanager

At the moment the documentation of failure inhibition matrices and the fault path management for different controller types and different vehicle projects are mainly maintained manually in individual Excel tables. This is not only time consuming but also gives a high potential for fault liability. In addition there is also no guarantee that the calibration of these failure inhibition matrices and its fault path really works. Conflicting aims between costs, time and fault liability require a new approach for the calibration, documentation and testing of failure inhibition matrices and the complete Diagnostic System Management (DSM) calibration. The standardization and harmonization of the Diagnostic System Management calibration for different calibration projects and derivates is the first step to reduce time and costs. Creating a master calibration for the conjoint fault paths and labels provides a significant reduction of efforts.
Technical Paper

The Turbocharged GDI Engine: Boosted Synergies for High Fuel Economy Plus Ultra-low Emission

Recent turbocharged Gasoline engines based on MPFI offer excellent power output and high nominal torque, however, also some disadvantages. The most significant restrictions of TC-engines - like poor fuel economy, limited emission capability and delayed transient response (turbo lag) - can be improved dramatically by a refined GDI application. The synergy effects of GDI, which are also partly used at naturally aspirated engines, are even more significant with turbocharging. The low emission capability of GDI enables turbocharged SULEV concepts within moderate cost of the emission / aftertreatment system. The outstanding low-end-torque, the high specific power and torque output of refined GDI-Turbo concepts enable high fuel efficiency combined with excellent fun to drive. Thus such GDI-Turbo concepts will become the most attractive technology to fulfill highest fuel economy-, emission- and performance requirements simultaneously.
Technical Paper

The OBD System Development Database - a Solution for Knowledge Management and Tool Supported Control System Design and Calibration

The correct information about legal demands of the On-Board-Diagnostic (OBD) system in a vehicle project is required throughout the entire development process. Usually, the main obstacle in succeeding is to provide the company's expertise of some few experts for all employees who work in OBD related projects. The paper describes the AVL solution for knowledge management and tool supported control system design and calibration: OBD System Development Database. The software enables the user to access the regulatory requirements for a specific application and legislation from past, present and future (proposed rule-making) point of view. Information concerning already available and stored monitoring concepts is linked to the requirements in order to re-use potentially suitable concepts and to enable an efficient knowledge exchange within the company.
Technical Paper

The Influences on Real Driving Emissions in India Outlook RDE Legislation BHARAT VI

Abstract With the official publication of the “RDE package 1” on 31st March 2016 the long awaited start of RDE testing is now fixed. This event marks a milestone in the emission legislation for passenger cars and is the first of a series of four RDE packages to fade-in real world testing of passenger cars in Europe. During the same time India announced in the Gazette of India on 19th February, 2016 - G.S.R. 187(E). - the draft of introduction of Bharat VI by April 1st 2020 [5] which also should include the Real Driving Emissions (RDE) on-road certification as per procedure laid down in AIS137 and as amended from time to time. As European RDE legislation will be the baseline for Indian RDE legislation rules this paper will highlight the differences and challenges expected between the requirements in Europe compared to India during the first tests done by AVL Technical Center Private Limited located in Gurgaon.
Technical Paper

The Impact of Emissions and Fuel Economy Requirements on Fuel Injection System and Noise of HD Diesel Engines

Despite the increasingly stringent emissions legislation, users and owners of commercial diesel vehicles are continually demanding that each new engine generation is more economical than the previous one. This is especially important for commercial vehicles where the majority of engines are in the 1-2ltr./cyl. class. The demands are being reflected in new engine designs with lower friction and improved structural stiffness, together with fuel systems having increased pressure capability, higher spill rates, injection rate shaping and advanced control features. These fuel system requirements have led to a variety of new fuel injection systems and in the search for increased injection pressure these fuel systems have placed greater demands on the engine, especially in areas such as the cylinder head and fuel system drive, sometimes with adverse effects on the combustion and fuel injection system induced mechanical noise.
Technical Paper

The Creation of a Car Interior Noise Quality Index for the Evaluation of Rattle Phenomena

Rattle noise produced in the vehicle interior due to broadband excitation by road irregularities is a major concern with respect to driving comfort, and therefore has become one of the most important topics of acoustic development in recent years. A quantification i.e. measurement of this rattle noise is of fundamental importance for systematic development work and production control. Common noise level measurements (dB, dBA, etc. ) do not represent the rattle character in the vehicle interior as revealed during initial investigations. To overcome this problem and to substitute the subjective assessment with a combination of measurable parameters, the psychoacoustic software AVL-EAR was applied to create an Interior Rattle Quality Index. Based on more than 40 different vehicles that have been subjectively assessed by approximately 70 test persons, the index was generated by means of multiple pair comparisons and statistics on measurement data.
Technical Paper

The 2-Step VCR Conrod System – Functional Development and Oil Investigations

Variable compression technology for internal combustion engines will become increasingly more important in the future to meet stringent global fuel economy and CO2 standards. A 2-step VCS system is in development at AVL and the basic functionality and potential were described in a technical paper and presentation at the SAE WCX 2017. The system is based on a hydraulically switched and locked telescopic conrod. VCS system hardware was designed, virtually optimized with CAE simulation methods and procured for the boundary conditions of a typical 2.0L I4 turbocharged direct injected gasoline engine representing state-of-the-art for the next few years to come. This paper will describe the latest status of the development efforts and the results gained during motored and fired engine testing and the completion of the functional validation and proof of concept.
Technical Paper

The 2-Step VCR Conrod System - Modular System for High Efficiency and Reduced CO2

Abstract In order to achieve future CO2 targets - in particular under real driving conditions - different powertrain technologies will have to be introduced. Beside the increasing electrification of the powertrain, it will be essential to utilize the full potential of the internal combustion engine. In addition to further optimization of the combustion processes and the reduction of mechanical losses in the thermal- and energetic systems, the introduction of Variable Compression Ratio (VCR) is probably the measure with the highest potential for fuel economy improvement. VCR systems are expected to be introduced to a considerable number of next generation turbocharged Spark Ignited (SI) engines in certain vehicle classes. The basic principle of the AVL VCR system described in this paper is a 2-stage variation of the conrod length and thus the Compression Ratio (CR).
Technical Paper

System Design Model for Parallel Hybrid Powertrains using Design for Experiments

The submitted presentation focuses on an optimization methodology which uses DoE methods to define component parameters of parallel hybrid powertrains such as number of gears, transmission spread, gear ratios, progression factor, e-motor power, e-motor nominal speed, battery voltage and cell capacity. Target is to find the optimal configuration based on customer targets (fuel consumption, performance targets etc.). In the treated drivetrain configuration, the combustion engine is considered as a fixed component. The introduced methodology reduces development time and increases output quality of the early system definition phase. The output parameters are used as a first hint for subsequently performed detailed component development. The methodology integrates existing software tools like AVL CRUISE and AVL CAMEO []. The new approach in the presented methodology includes specific integrated transmission and e-motor models in the vehicle simulation loop.
Technical Paper

Sound Optimization for Downsized Engines

Abstract Today, the number of downsized engines with two or three cylinders is increasing due to an increase in fuel efficiency. However, downsized engines exhibit unbalanced interior sound in the range of their optimal engine speed, largely because of their dominant engine orders. In particular, the sound of two-cylinder engines yields half the perceived engine speed of an equivalent four-cylinder engine at the same engine speed. As a result when driving, the two-cylinder engine would be shifted to higher gears much later, diminishing the expected fuel savings. This contribution presents an active in-car sound generation system that makes a two-cylinder engine sound like the more familiar four-cylinder engine. This is done by active, load-dependent playback of signals extracted from the engine vibration through a shaker mounted on the firewall. A blind test with audio experts indicates a significant reduction of the engine speed when shifting to a higher gear.
Technical Paper

Single Cylinder 25kW Range Extender: Development for Lowest Vibrations and Compact Design Based on Existing Production Parts

The automotive trend towards increased levels of electrification is showing a clear direction for hybrid technologies. Nowadays Mild- and plug-in-hybrids open a very wide area of future developments whereas battery electric vehicles (BEV) are still evident but still perceived as niche products with limited production volumes. Nevertheless, major OEMs are working on these kinds of vehicles and have also brought such EV concepts into series production. All of these designs show a clear trend that, beside the topic of electric traction motor and energy storage systems, the internal combustion engine (ICE) is also coming into focus again. In many of these vehicles the range extender (RE) unit is foreseen as an emergency unit to recharge the batteries if the state of charge (SOC) is too low. One of the major advantages of a BEV over other designs is the very good acoustic behavior, so the NVH performance becomes the most challenging topic for RE development.
Technical Paper

Simulation of Piston Ring Dynamics and Their Effect on Oil Consumption

The sealing effect of piston rings in reciprocating engines have a major impact on blow-by and lube oil consumption (LOC). The sealing is achieved by the gas forces acting on the top and back side of the rings. In addition, the load in the radial direction is increased by the initial ring tension. Inertia forces arising from the oscillating vertical stroke and shear forces due to the secondary piston movement influence this sealing effect by a reduction in contact pressure. Numerical simulation of the piston and ring dynamics solves this non-linear problem and predicts the interaction between piston secondary motion, axial ring motion, and 2nd land pressure. This paper describes the modeling of the cylinder kit dynamics of a six-cylinder truck diesel engine for several operating conditions and ring modifications. The influence of boundary conditions and adjustment parameters on piston ring motion and gas penetration was investigated.
Journal Article

Simulation Methodology for Consideration of Injection System on Engine Noise Contribution

The target of the investigation is the particular influence of a fuel injection system and its components as a noise source in automotive engines. The applied methodology is demonstrated on an automotive Inline 4-cylinder Diesel engine using a common rail system. This methodology is targeted as an extension of a typical standard acoustic simulation approach for combustion engines. Such approaches basically use multi-body dynamic simulation with interacting FEM based flexible structures, where the main excitation crank train, timing drive, valve train system and piston secondary motion are considered. Within the extended approach the noise excitation of the hydraulic and mechanical parts of the entire fuel system is calculated and subsequently considered within the multi-body dynamic simulation for acoustic evaluation of structural vibrations.
Technical Paper

Shape Optimization by an Adjoint Solver based on a near-wall Turbulence Model

Abstract The aim of this paper is to present the adjoint equations for shape optimization derived from steady incompressible Navier-Stokes (N-S) equations and an objective functional. These adjoint Navier-Stokes equations have a similar form as the N-S equations, while the source terms and the boundary conditions depend on the chosen objective. Additionally, the gradient of the targeted objective with respect to the design variables is calculated. Based on this, a modification of the geometry is computed to arrive at an improved objective value. In order to find out, whether a more sophisticated approach is needed, the adjoint equations are derived by using two different approaches. The first approach is based on the frozen turbulence assumption and the second approach, which is advanced in this paper, is derived from the near wall k − ζ − f turbulence model.
Technical Paper

Scale-resolving simulation of an "on-road" overtaking maneuver involving model vehicles

Aerodynamic properties of a BMW car model taking over a truck model are studied computationally by applying the scale-resolving PANS (Partially-averaged Navier-Stokes) approach. Both vehicles represent down-scaled (1:2.5), geometrically-similar models of realistic vehicle configurations for which on-road measurements have been performed by Schrefl (2008, PhD Thesis, TU Darmstadt, Germany, ISBN 978-3-8322-7010-0). A relevant introductory study dealing with the wind tunnel flow past a single BMW car model has been performed by Jakirlic et al. (SAE Int. J. Passeng. Cars - Mech. Syst. 7(2):2014). Reynolds number relevant to the realistic BMW car, based on the car height and “relative velocity” (the velocity difference between car and track is (160-80) km/h) corresponds to 1.28 million. The operating conditions of the modelled “on-road” overtaking maneuver are determined by applying the dynamic similarity concept in terms of Reynolds number consistency.