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Technical Paper

A Stiffness Optimization Procedure for Automobile Rubber Mounts

2001-04-30
2001-01-1445
Generally, it is well known that road noise generated by vibration from automobile tires and suspensions can be reduced by changing the stiffness of the rubber mounts installed in the suspension systems. Such stiffness, however, is rarely changed to avoid riding discomfort and so on. In this paper, a stiffness optimization method for suspension system rubber mounts that reduces road noise, and improves riding comfort as well, is presented. In the process, Road Noise Contribution Analysis (RNCA) is applied to the target vehicle to specify the major factors of road noise. Furthermore, the suspension system of the vehicle is investigated by Sensitivity Analysis using Measured FRF data (SAMF) to identify the optimal stiffness combination of rubber mounts. As a result, an effective stiffness combination of two mounts is specified to reduce road noise and to improve riding comfort.
Technical Paper

Sound Design in the Passenger Compartment with Active Noise Control in the Air Intake System

2001-04-30
2001-01-1432
In the future, the requirements of acoustic behavior in air intake systems will continue to increase. Active systems will be necessary to reach the higher legislative standards and customer expectations regarding noise levels. The optimization of the Active Noise Control System regarding the sound design in the interior is based on the transfer function between the engine and the passenger compartment as well as the design of the air intake system. This paper shows the development process, with a focus on the investigation of transfer functions in passenger cars and the computational calculation for the system configuration.
Technical Paper

Optimization of Vehicle Warm-up Using Simulation Tools

2001-05-14
2001-01-1705
A comprehensive simulation method is presented for the optimization of vehicle warm-up. Sophisticated one dimensional simulation methods based on network theory are used for flow simulation to limit computation time and guarantee high simulation quality. Partial integration of three dimensional flow simulation methods help to improve accuracy. Simulation sub-models for the engine, the HVAC system, and the passenger cabin are combined to simulate the warm-up process of the vehicle. This functionality is implemented in a modern software tool named KULI to support the development engineer as good as possible. Steady state and transient simulation are used to optimize the warm-up behavior.
Technical Paper

Transient Air Conditioning Simulation Using Network Theory Algorithms

2001-05-14
2001-01-1690
An efficient air-conditioning system is an important factor for the commercial success of an automotive product, because of the thermal comfort for the passengers being an important incentive for the purchaser. A simulation tool is presented that makes it possible to design and optimize A/C refrigerant circuits together with the engine cooling system in a very early stage of the design process. This tool is based on networks including the enhanced heat exchange theory which also takes into consideration refrigerant phase changes. A graphical user interface and predefined simulation models which are based on the respective geometry of the system components make it easy to create a virtual vehicle for mathematical analysis of the various heat and mass flows. High flexibility and short calculation time together with high accuracy enable the engineer to make efficient investigations.
Technical Paper

Sound Package Design for a Convertible by Statistical Energy Analysis

2001-04-30
2001-01-1623
The application of SEA (Statistical Energy Analysis) to the sound package design for a convertible is presented. SEA modeling was used optimize the soft-top construction and the acoustic insulation in the top-stack area (where the soft-top is stored) which were shown to be important transmission paths for tire noise. Correlation between measurement data and predictions from the SEA model is presented and good agreement shown. It is concluded that SEA can be applied to determine the special sound package requirements for convertible vehicles.
Technical Paper

Progress in the Optimized Application of Simulation Tools in Vehicle Air Conditioning

2001-05-14
2001-01-1699
The paper focuses on the usage of simulation tools during the development of vehicle air-conditioning systems. The integration of simulation is explained at every stage of the process. It differentiates at which step the 3-D simulation properties are needed and where the advantages of 1-D tools decide its use. For each demand the most targeting way of calculation has to be chosen, facing properties like precision, hardware needs and especially modeling as well as calculation time along to the tightened development schedule. Examples are given from system layout to detailed optimization.
Technical Paper

Optimizing Vehicle Response in a Combined Ride and Handling Full Car Model by Optimal Control Strategies

2001-04-30
2001-01-1581
This paper focuses on the control of combined ride and handling full car model of a Four-Wheel Steering (4WS) Vehicle and determines how can ride and handling influence together by the road irregularities and front and rear steering inputs and disturbances like side wind. A 9 DOF linear full car model is discussed as the controller model, which controls a 9 DOF nonlinear full car model. Control inputs are 4 actuators for each wheel that control vertical displacement of sprung mass and 2 actuators for rear wheels that control the rear steering angle. The model describes vertical and lateral displacements and rotations and it is considered to have quasi-static conditions in longitudinal displacement. Control strategies that are used in this paper are Linear Quadratic Regulator (LQR) and Dynamic Programming that regulates vertical displacements and tracks the yaw rate reference.
Technical Paper

Advances in Complex Eigenvalue Analysis for Brake Noise

2001-04-30
2001-01-1603
Brake squeal has been analyzed by finite elements for some time. Among several methods, complex eigenvalue analysis is proving useful in the design process. It requires hardware verification and it falls into a simulation process. However, it is fast and it can provide guidance for resolving engineering problems. There are successes as well as frustrations in implementing this analysis tool. Its capability, robustness and reliability are closely examined in many companies. Generally, the low frequency squealing mechanism is a rotor axial direction mode that couples the pads, rotor, and other components; while higher frequency squeal mainly exhibits a rotor tangential mode. Design modifications such as selection of rotor design, insulator, chamfer, and lining materials are aimed specifically to cure these noise-generating mechanisms. In GM, complex eigenvalue analysis is used for brake noise analysis and noise reduction. Finite element models are validated with component modal testing.
Technical Paper

Engine Internal Dynamic Force Identification and the Combination with Engine Structural and Vibro-Acoustic Transfer Information

2001-04-30
2001-01-1596
The vibration-generating mechanisms inside an engine are highly non-linear (combustion, valve operation, hydraulic bearing behavior, etc.). However, the engine structure, under the influence of these vibration-generating mechanisms, responds in a highly linear way. For the development and optimization of the engine structure for noise and vibration it is beneficial to use fast and ‘simple’ linear models, like linear FE-models, measured modal models or measured FRF-models. All these models allow a qualitative assessment of variants without excitation information. But, for true optimization, internal excitation spectra are needed in order to avoid that effort is spent to optimize non-critical system properties. Unfortunately, these internal excitation spectra are difficult to measure. Direct measurement of combustion pressure is still feasible, but crank-bearing forces, piston guidance forces etc. can only be identified indirectly.
Technical Paper

Noise Control for Heavy Duty Trucks, a Systems Approach

2001-04-30
2001-01-1531
This paper describes a general noise control system design process. The methodology is applied to heavy duty trucks. The paper describes the benefits, for optimization purposes, of a systems approach versus a component approach. The role of both experimental and predictive approaches on the design process is outlined. Available noise control materials are briefly described, and lastly, an example of the results of the development of a noise control system by the experimental systems approach is provided.
Technical Paper

Powertrain Mounting Development Based on Computational Simulation and Experimental Verification Method

2001-04-30
2001-01-1509
This paper presents a method applied in the development of an optimized transmission rubber mount of a midsize Diesel pickup. The focus of this optimization were to improve the vibration insulation and consequently improve the NVH (Noise and Vibration Harshness) quality of the vehicle. The paper describes the basic mounting design and manufacturing constrains, the simulation modeling basis, inputs required to perform the computational simulation, the experimental method used to extract the center of gravity and rotational inertia of the powertrain and a general mounting tuning strategy. The mounting dynamic simulation results for the optimized version is also presented compared to the original one. In order to quantify the noise and vibration improvements, the internal noise and vibration transmissibility levels were measured and compared in percentile reduction basis to current vehicle levels
Technical Paper

Optimization of Vehicle Driveline Vibrations Using Genetic Algorithm (GA)

2001-04-30
2001-01-1511
Low frequency longitudinal vibrations resulting from driver throttle inputs are a common problem in modern passenger cars. This phenomenon, which is commonly referred to as shuffle or shunt, is due to sudden changes in the engine torque exciting torsional oscillations in the driveline. This paper presents a dynamic model of a vehicle driveline for the optimization of low frequency torsional vibration. The model used is first validated against experimental tests. Parameter sensitivity studies have been carried out using the model to identify the important components affecting shuffle. Three key parameters have been chosen from the parameter study. To optimize these key factors, Genetic Algorithms (GAs) have been used in this multi-parameter optimization problem. The results obtained from GAs have been compared with the calculus based optimization techniques.
Technical Paper

Frame Resonance of High Air Flow Resistivity Plastic Foams: Properties to Improve Acoustical Absorption of Composite Multi-Layered Systems

2001-04-30
2001-01-1558
The optimization of acoustical properties of multi-layered materials used in the automotive industry requires a good understanding and characterization of the various component layers. This is a particular concern in the case of headliners where performance must be balanced with packing space demands. These composite structures when used with flexible urethane foams provide good stiffness and light weight, but their acoustic performance can be sub-optimal. Measurements undertaken with poro-elastic high airflow resistivity foams highlighted frame resonances which, if exploited, might significantly improve the acoustical performance of this system. A new modeling technique based on a pseudo-macroscopic description of the poro-elastic material in the framework of a four-pole network will be used to explain these frame resonances. This formulation exploits the electro-acoustical analogy in transmission line theory.
Technical Paper

Laminate Dash Ford Taurus Noise and Vibration Performance

2001-04-30
2001-01-1535
Mastic material, constrained or non-constrained with doublers, is the traditional method in adding vibrational damping to a steel structure with the goal of reducing panel vibration and radiated sound. With the use of laminated vibration damped steel (LVDS), Ford has been able to reduce the dash panel vibration and optimize sound package design for powertrain noise attenuation. These NVH benefits are presented as the result of a study completed with a laminated dash on a Ford Taurus.
Technical Paper

Polyurethane Foam Systems For NVH and Improved Crashworthiness

2001-04-30
2001-01-1467
Recently, automotive engineers have been looking at rigid polyurethane foam systems for the advantages their application brings to vehicle design and performance. The benefits range from NVH management achieved through effective body cavity sealing and improved structural dynamics, to enhanced vehicle crashworthiness. These benefits can be realized through application of polyurethane foam systems designed for energy management. These systems offer multifunctional, low cost solutions to traditional approaches and can be modeled early in the vehicle design stage. In many cases, the overall vehicle mass is reduced as reinforcements are eliminated and/or sheet metal thickness is decreased. Dow Automotive has developed a family of water blown polyurethane foams specifically for these applications. Development has focused on foam systems designed for impact optimization, allowing OEM's to optimize the body structure content.
Technical Paper

Optimization of Vehicle Air Conditioning Systems Using Transient Air Conditioning Performance Analysis

2001-05-14
2001-01-1734
The National Renewable Energy Laboratory (NREL) has developed a transient air conditioning (A/C) system model using SINDA/FLUINT analysis software. It captures all the relevant physics of transient A/C system performance, including two-phase flow effects in the evaporator and condenser, system mass effects, air side heat transfer on the condenser/evaporator, vehicle speed effects, temperature-dependent properties, and integration with a simplified cabin thermal model. It has demonstrated robust and powerful system design optimization capabilities. Single-variable and multiple variable design optimizations have been performed and are presented. Various system performance parameters can be optimized, including system COP, cabin cool-down time, and system heat load capacity. This work presents this new transient A/C system analysis and optimization tool and shows some high-level system design conclusions reached to date.
Technical Paper

Method for Predicting and Optimizing the Strength of Extruded Multi-Void Aluminum Heat Exchanger Tube

2001-05-14
2001-01-1737
The mechanical response to internal pressure in extruded multi-void tube is investigated for three profiles using AA1050 alloy. Hydrostatic pressure data and changes in internal tube geometry are used to determine the effective stress in internal tube walls to instability (failure). True stress and strain data for internal walls in the tube are established and a model is proposed to predict the material response and pressure at failure. These data are compared to bulk material data from tensile testing. Differences in material response are attributed to stress state and size effects, and these mechanisms are reviewed. Process-structure-property relationships of extruded aluminum heat exchanger tube are also reviewed for brazed assemblies in light of the influence on size effects.
Technical Paper

Experimental Study of Automotive Heat Shield Geometry with Natural Convection and Radiation Boundary Conditions

2001-05-14
2001-01-1746
Shielding a vehicle underbody is becoming a daunting task with increased exhaust temperatures due to emissions regulations and ever-increasing packaging constraints, which place components ever closer to exhaust systems. This experimental study was initiated to evaluate the two dimensional thermal effects of heat shield flange height and shield width in vehicle underbody idle conditions. The ultimate goal of this study is to develop a function to optimize the shape of heat shielding to achieve a specified floorpan temperature during vehicle idle conditions.
Technical Paper

Thermal Performance Prediction of Front-End Heat-Exchange Modules

2001-05-14
2001-01-1765
The application of high performance engines and climate control systems, coupled with constraints relating to vehicle styling, aerodynamics and underbonnet packaging, continues to present demanding thermal management challenges in the design and layout of the front-end cooling module. Several computational fluid dynamics techniques are now available to assist in this design and packaging process, but many of these require a high level of specialization from the user. The work reported here outlines a relatively simple 1-dimensional technique to aid in the analysis and optimization of the cooling pack configuration. The tool can be used interactively by a multi-skilled vehicle engineer throughout the entire design and development of a new vehicle.
Technical Paper

2D Mapping and Quantification of the In-Cylinder Air/Fuel-Ratio in a GDI Engine by Means of LIF and Comparison to Simultaneous Results from 1D Raman Measurements

2001-05-07
2001-01-1977
The optimization of the vaporization and mixture formation process is of great importance for the development of modern gasoline direct injection (GDI) engines, because it influences the subsequent processes of the ignition, combustion and pollutant formation significantly. In consequence, the subject of this work was the development of a measurement technique based on the laser induced exciplex fluorescence (LIF), which allows the two dimensional visualization and quantification of the in-cylinder air/fuel ratio. A tracer concept consisting of benzene and triethylamine dissolved in a non-fluorescent base fuel has been used. The calibration of the equivalence ratio proportional LIF-signal was performed directly inside the engine, at a well known mixture composition, immediately before the direct injection measurements were started.
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