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Journal Article

Novel Nondestructive Imaging Analysis for Catalyst Washcoat Loading and DPF Soot Distribution Using Terahertz Wave Computed Tomography

2011-08-30
2011-01-2064
This paper describes a three-dimensional (3D) visualization framework using terahertz (THz) waves for quantitative analysis of the distribution of catalyst washcoat loading and diesel particulate filter (DPF) soot deposits. THz waves, which are electromagnetic waves located between infrared and microwave in the electromagnetic spectrum, have good directivity and moderate resolution. Accordingly, a computed tomography (CT) technique has been developed to image the interior of an object using the spectral information of THz waves. This THz wave CT technique can be used to analyze the interior of various target objects, and has good penetrability of ceramic substances used as catalysts in automobiles. Against this background, a method using THz CT for nondestructive analysis of catalyst washcoat loading and the density distribution of soot was developed, and this framework was evaluated.
Journal Article

Flexible Real-Time Simulation of Truck and Trailer Configurations

2011-09-13
2011-01-2264
Real-time simulation of truck and trailer combinations can be applied to hardware-in-the-loop (HIL) systems for developing and testing electronic control units (ECUs). The large number of configuration variations in vehicle and axle types requires the simulation model to be adjustable in a wide range. This paper presents a modular multibody approach for the vehicle dynamics simulation of single track configurations and truck-and-trailer combinations. The equations of motion are expressed by a new formula which is a combination of Jourdain's principle and the articulated body algorithm. With the proposed algorithm, a robust model is achieved that is numerically stable even at handling limits. Moreover, the presented approach is suitable for modular modeling and has been successfully implemented as a basis for various system definitions. As a result, only one simulation model is needed for a large variety of track and trailer types.
Technical Paper

PCCI Control Authority of a Modern Diesel Engine Outfitted with Flexible Intake Valve Actuation

2009-06-15
2009-01-1882
Premixed charge compression ignition (PCCI), an advanced mode combustion strategy, promises to simultaneously deliver the fuel efficiency of diesel combustion and the ultra-low NOx emissions that usually require advanced exhaust aftertreatment. A flexible, computationally efficient, whole engine simulation model for a 2007 6.7-liter diesel engine with exhaust gas recirculation (EGR), variable-geometry turbo-charging (VGT), and common rail fuel injection was validated after extensive experimentation. This model was used to develop strategies for highly fuel-efficient, ultra-low NOx emission PCCI. The primary aim of this modeling investigation is to determine the PCCI control authority present on a modern diesel engine outfitted with both conventional actuators (multi-pulse fuel injectors, an EGR valve, and VGT) and flexible intake valve closure modulation (IVCM) which dictates the effective compression ratio (ECR).
Journal Article

Effect of Mesh Structure in the KIVA-4 Code with a Less Mesh Dependent Spray Model for DI Diesel Engine Simulations

2009-06-15
2009-01-1937
Two different types of mesh used for diesel combustion with the KIVA-4 code are compared. One is a well established conventional KIVA-3 type polar mesh. The other is a non-polar mesh with uniform size throughout the piston bowl so as to reduce the number of cells and to improve the quality of the cell shapes around the cylinder axis which can contain many fuel droplets that affect prediction accuracy and the computational time. This mesh is specialized for the KIVA-4 code which employs an unstructured mesh. To prevent dramatic changes in spray penetration caused by the difference in cell size between the two types of mesh, a recently developed spray model which reduces mesh dependency of the droplet behavior has been implemented. For the ignition and combustion models, the Shell model and characteristic time combustion (CTC) model are employed.
Journal Article

Model Based E85 Cold Start Optimization for DISI Engines

2009-06-15
2009-01-1909
The startability of SI engines, especially of DISI engines, is the greatest challenge when using ethanol blended fuels. The development of a suitable injection strategy is therefore the main engineering target when developing an ethanol engine with direct injection. In order to limit the test efforts of such a program, a vaporization model has been created that provides the quantity of vaporized fuel depending on pressure and on start and end, respectively number and split relation of injections. This model takes account of the most relevant fuel properties such as density, surface tension and viscosity. It also considers the interaction of the spray with cylinder liner, cylinder head and piston. A comparison with test results shows the current status and the need for action of this simulation model.
Technical Paper

Assessment of a Numerical Model for Multi-Hole Gasoline Sprays to be Employed in the Simulation of Spark Ignition GDI Engines with a Jet-Guided Combustion Mode

2009-06-15
2009-01-1915
Results of an experimental campaign conducted on a multi-hole gasoline injector are used to assess a numerical model for the spray dynamics suitable to be employed for the prediction of a GDI engine pressure cycle. The considered injector generates a spray with a hollow-ellipsoid footprint structure on a plane perpendicular to the spray axis. Spray penetration lengths and cone angles are measured at different injection pressures and total injected masses in an optically accessible vessel containing nitrogen at controlled conditions of temperature and pressure. Injected mass flow rate is measured on a Bosch tube. The numerical simulation is performed within the AVL Fire™ code environment. As a first step, the gasoline is considered as entering a constant volume environment containing nitrogen, in order to reproduce the effected experiments. Measured injection flow rates and cone angles are used as input variables for the model.
Technical Paper

Advances in Variable Density Wall Functions for Turbulent Flow CFD-Simulations, Emphasis on Heat Transfer

2009-06-15
2009-01-1975
A new variable density / physical property wall function formalism has been developed. The new formalism is designed to extend the validity range of wall functions to cover both the low- and high-Reynolds-number domains so that the restrictions on the non-dimensional near-wall mesh resolution can be avoided. The new formalism also accounts for the temperature gradient induced variations of density, viscosity, heat conductivity and specific heat capacity. The new wall function formalism is constructed in conjunction with a modified low-Reynolds-number turbulence model in order to avoid the conflicting requirements of low- and high-Reynolds-number models on the near wall mesh resolution. The new formulation is validated with test simulations of strongly heated air flows in circular tube against measurements and Direct Numerical Simulation (DNS) results.
Technical Paper

Development of a Multi-Dimensional Parallel Solver for Full-Scale DPF Modeling in OpenFOAM®

2009-06-15
2009-01-1965
A new fast and efficient parallel numerical solver for reacting and compressible flows through porous media has been developed in the OpenFOAM® (Open Field Operation and Manipulation) CFD Toolbox. With respect to the macroscopic model for porous media originally available in OpenFOAM®, a different mathematical approach has been followed: the new implemented solver makes use of the physical normal components resulting from the velocity expansion in the unit orthogonal vector basis to compute the Darcy pressure drop across the porous medium. Also, an additional sink term to account for the increased flow friction over the porous wall has been included into the momentum equation. In the new solver, the pressure correction equation is still able to achieve a faster convergency at very low permeability of the medium, also when it is associated with grid non-orthogonality.
Journal Article

Applying an Interactively Coupled CFD-Multi-Zone Approach to Study the Effects of Piston Bowl Geometry Variations on PCCI Combustion

2009-06-15
2009-01-1955
Recently, a consistent mixing model for the two-way coupling of a CFD code and a zero-dimensional multi-zone code was developed. This work allowed for building an interactively coupled CFD-multi-zone approach that can be used to model HCCI combustion. In this study, the interactively coupled CFD-multi-zone approach is applied to PCCI combustion in a 1.9l FIAT GM Diesel engine. The physical domain in the CFD code is subdivided into multiple zones based on one phase variable (fuel mixture fraction). The fuel mixture fraction is the dominant quantity for the description of nonpremixed combustion. Each zone in the CFD code is represented by a corresponding zone in the zero-dimensional multi-zone code. The zero-dimensional multi-zone code solves the chemistry for each zone, and the heat release is fed back into the CFD code. The thermodynamic state of each zone, and thereby the phase variable, changes in time due to mixing and source terms (e.g., vaporization of fuel, wall heat transfer).
Technical Paper

Shearplate – A New Innovative Approach to Reduce Powertrain Noise

2009-05-19
2009-01-2065
This Paper is evaluating the development and effectiveness of using a Shearplate, a new and innovative approach to reduce powertrain noise and vibrations. The results show that the approach is offering monumental improvements in terms of reduced noise and vibrations. Sound quality evaluations also show very clearly that the approach is an effective countermeasure to the targeted problems. With the knowledge gathered during the development and with what is partly presented in this paper we now have an additional tool that car manufacturers can deploy in their efforts to design more fuel efficient and cleaner burning engines without sacrificing NVH performance.
Technical Paper

Transmission Loss Measurement with and without an Anechoic Termination

2009-05-19
2009-01-2035
The definition method and the two load/source method of a transmission loss test of an automotive tuning device are discussed in this paper. For the definition method, the accuracy penalty due to the imperfect anechoic termination quality is studied based on an empirical acoustic model of glass-wool and the best practice of constructing an anechoic termination is attempted. The conclusion is verified with numerical simulations. For the two load/source method, the difference in the two source/load impedances compounded with the error of measured acoustic pressures, as related to transmission loss accuracy, is discussed and demonstrated.
Technical Paper

Boundary Conditions Affecting Gear Whine of a Gearbox Housing Acting as a Structural Member

2009-05-19
2009-01-2031
Vehicle cabin gear whine levels have long been known to contribute to driver annoyance and perceptions of poor quality in passenger cars and trucks, as well as contributing to operator fatigue in helicopters and heavy machinery. For material handling vehicles, radiated gear whine not only influences annoyance and fatigue of operators, but also creates unwanted noise in the operational environment such as warehouses and plants. Upfront management of gear whine levels using predictive software tools is therefore critical for satisfactory design of gearboxes used in such applications. One challenge, however, is selecting the proper boundary conditions for modeling a gearbox acting as a load-bearing structural member used in the material handling vehicles.
Technical Paper

Optimizing R&H and NVH Performances Early in the Design Process via Multi Body Simulation

2009-05-19
2009-01-2087
This paper presents a CAE based approach to accurately simulate and optimize Ride and Handling metrics. Because of the wide range of vehicle phenomena involved, across the variety of frequency ranges, it is essential that the vehicle model includes proper representation of the dynamic properties of the various subsystems (e.g. tires, steering, PT, etc.) Precise correlation between test and simulation for standalone vehicle components and systems is achieved by replicating in the MBS (Multi-body Simulation) the same tests and boundary conditions. This allows the analyst to correctly define those crucial elements and parameters which have the greatest effect on the R&H attribute to be investigated. Setting up the simulation to correctly represent only one single maneuver simulation at a time would not allow the analyst to consider how the dynamic properties of the chassis design variables should be tuned to achieve to best balance and trade-offs.
Technical Paper

Steering Grunt Noise Robustness Improvement

2009-05-19
2009-01-2095
Grunt is a structure-born noise caused by resonance of the steering gear torsion bar (T-bar) in an HPAS (Hydraulic Power Assist Steering) system. The goal of this work was to develop techniques to quantify and predict grunt in a RV (rotary valve) steering gear system. First, vehicle testing was used to identify an objective metric for grunt: y = dynamic pressure in the return line. Then, a computer simulation was developed to predict y as a function of two known control factors. The simulation results were correlated to measurements on a test vehicle. Finally, the simulation was expanded to include two additional control factors, and grunt predictions were demonstrated on a different test vehicle.
Technical Paper

Complex Mode Analysis on Disc Brake Squeal and Design Improvement

2009-05-19
2009-01-2101
Squeal noise in vehicle disc brakes is perceived by comsumers as both annoying and warranty cost. The mechanism is considered a mode coupling phenomenon also referred to as coalescence. In this paper, the system eigenvalues have been computed using a technique based on the • nite element method in order to obtain the dynamical properties of the disc brake assembly. The simulated squeal results were compared with the brake noise test that was in accordance with SAE J2521 standard and showed good correlation for some squeal frequencies which indicated that the research on disc brake squeal using complex mode could predict squeal propensity of the disc brake. Among the methods that have been used to control squeal noise, increasing the system damping has been shown to be very effective. The most commonly used method to increase system damping consists of attaching multi-layer laminates on the back of the brake pads.
Journal Article

A Study of Effects of Brake Contact Interfaces on Brake Squeal

2009-05-19
2009-01-2100
Brake squeal is caused by the friction-induced vibration at the rotor/pad interfaces (primary contact interfaces) in a disc brake system. While there have been numerous research work evaluating the influence of primary contact interfaces on brake squeal, few studies can be found on the effect of the secondary contact interfaces, i.e., outer pad/caliper fingers, inner pad/pistons and pad/abutment, which can also significantly affect brake squeal based on our various dynamometer and vehicle tests. It is therefore the objective of this paper to investigate both the primary and the secondary contact interfaces and their influence on brake squeal. Simplified analytical models are created to gain insight into the stability of the brake system under low and high brake pressure; non-linear FEA analysis is employed for parametric study and countermeasure development; dynamometer and vehicle tests are used for verification.
Technical Paper

A Three-Dimensional Ring-Based Structural Tyre Model: Development and Validation

2009-05-19
2009-01-2105
This paper presents the development of a structural model for passenger car tyres, based on a three-dimensional flexible ring on an elastic foundation. The ring represents the belt and the elastic foundation represents the tyre sidewall. The tyre model, which is implemented as a finite element model, is valid below the first treadband axial bending mode and includes a definition of the wheel flexibility and air cavity. The eigenfrequencies predicted by the model are within 5% of the measured eigenfrequencies. The model is validated by comparing predicted with measured responses for both an unloaded and loaded tyre.
Technical Paper

Power Train Model Characteristics for Vibration Analyses – Conflicting Demands in Off Line and HiL Environments

2009-05-19
2009-01-2072
High quality predicting of power train vibration behaviour is desired in the early design stage for efficient vehicle development. Conflicting demands arise, since precise, fast simulation models are required. High precision of the models will allow for the elimination of resonance phenomena for future products, thereby ensuring their comfort for the customers. Fast simulations are becoming increasingly important for linking test environments with virtual prototypes under development. This paper deals with different aspects in these conflicting demands for power train vibration models. First, the paper investigates real-time capable mechanical models and decided in favor of the object-oriented modeling approach “for requirements of Hardware in the Loop” (HiL). This paper takes a closer look at the advantages of the object-oriented approach, the model setup, its validation and the test results.
Technical Paper

Design and Conduct of Precision Planetary Gear Vibration Experiments

2009-05-19
2009-01-2071
Abstract Despite a large body of analytical work characterizing the dynamic motion of planetary gears, supporting experimental data is limited. Experimental results are needed to support computer modeling and offer practical optimization guidelines to gear designers. This paper presents the design and implementation of a test facility and precision test fixtures for accurate measurement of planetary gear vibration at operating conditions. Acceleration measurements are made on all planetary bodies under controlled torque/speed conditions. Custom, high-precision test fixtures accommodate instrumentation, ensure accurate alignment, help isolate gear dynamics, and allow for variability in future testing. Results are compared with finite element and lumped parameter models.
Technical Paper

Application of Hydraulic Body Mounts to Reduce the Freeway Hop Shake of Pickup Trucks

2009-05-19
2009-01-2126
When pickup trucks are driven on concrete paved freeways, freeway hop shake is a major complaint. Freeway hop shake occurs when the vehicle passes over the concrete joints of the freeway which impose in-phase harmonic road inputs. These road inputs excite vehicle modes that degrade ride comfort. The worst shake level occurs when the vehicle speed is such that the road input excites the vehicle 1st bending mode and/or the rear wheel hop mode. The hop and bending mode are very close in frequency. This phenomenon is called freeway hop shake. Automotive manufacturers are searching for ways to mitigate freeway hop shake. There are several ways to reduce the shake amplitude. This paper documents a new approach using hydraulic body mounts to reduce the shake. A full vehicle analytical model was used to determine the root cause of the freeway hop shake.
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