Refine Your Search

Topic

Author

Affiliation

Search Results

Technical Paper

Actuation and Fastening With Shape Memory Alloys in the Automotive Industry

1996-04-01
91A103
As a result of a phase transformation, shape memory alloys can change their shape when the temperature changes. This unusual effect can be utilized in actuation and fastening components for automotive applications. Springs made from Ni-Ti shape memory alloys change their rate in a predetermined temperature range due to a significant change in the elastic modules of the material. They can be used as sensor-actuators in pressures control valves or oil cooler by-pass valves in automatic transmissions or to compensate for oil viscosity changes in shock absorbers or thermal expansion of dissimilar materials in gear boxes. If the recovery is constrained, i.e., shape memory element is physically prevented from returning into its original shape, a potentially high stress is generated. This effect is used in fastener rings. Fasteners made from Ni-Ti alloys provide high reliability and easy installation for braid terminations, locating of shaft mounted components, connectors and hose clamps.
Technical Paper

Aerodynamic Effects of Oversized Tires and Tall Landing Gear on a Small General Aviation Aircraft

1999-04-20
1999-01-1592
An experimental investigation was conducted to identify the aerodynamic effects of oversized low-pressure (Tundra) tires and tall landing gear on a Piper Super Cub airplane. Water tunnel and wind tunnel tests were performed using, respectively, a 1/20 scale model and full-scale landing gear and tire components. Force and moment data suggest that larger tires and taller gear most affect the drag and side force. Small trim changes are apparent, but the basic static stability behavior appears unchanged.
Technical Paper

Quantification of Intake System Noise Using an Experimental Source-Transfer-Receiver Model

1999-05-17
1999-01-1659
Design optimisation with respect to interior noise is currently a topic of great concern for the automotive industry. An essential element in this process is to obtain a correct understanding of the various noise sources which are present, and the ways in which these sources propagate to the critical receiver. An experimental source-transfer-receiver methodology is presented, that allows quantifying the structure borne and airborne source strength of the intake system components and its contribution to the interior noise. The method allows interior noise optimisation after identification of the dominant contributors. The methodology is applied to identify the noise contribution of the air intake system to the interior noise of an 8-cylinder upper class vehicle. Correlation of the Structure Borne Transfer Path Analysis and Airborne Source Quantification models with physical decoupling experiments demonstrates a high correspondence.
Technical Paper

Gas Flows Through the Inter-Ring Crevice and Their Influence on UHC Emissions

1999-05-03
1999-01-1533
Influence of the inter-ring crevice, the volume between the top and second piston rings, on unburned hydrocarbon (UHC) emission was experimentally and numerically investigated. The ultimate goal of this study was to estimate the level of UHC emission induced by the blow-up of inter-ring mixture, i.e., unburned gases trapped in the inter-ring crevice. In the experiments, the inter-ring mixture was extracted to the crankcase during the late period of expansion and the early period of exhaust stroke through the engraved grooves on the lower part of cylinder wall. Extraction of the mixture resulted in the significant reductions of UHC emission in proportion to the increments of blowby flow rate, without any losses in efficiency and power. This experimental study has confirmed the importance of inter-ring crevice on UHC emission in an SI engine and established a relationship between the inter-ring mixture and UHC emission.
Technical Paper

Mathematical Models of Fastened Structural Connections

1999-04-20
1999-01-1576
The development of efficient and reliable methods for the design and analysis of fastened structural connections is among the most important problems in aerospace applications because fastened structural connections are common sites of failure initiation. Numerical simulation of fastened structural connections is difficult because there are complicated interactions between the fasteners and the structural components being joined and one of the most important attributes of a fastened connection, the clearance, is a stochastic variable. This paper presents a mathematical model for frictionless shear connections and its implementation within the framework of the p-version of the finite element method.
Technical Paper

Artificial Neural Network Based Energy Storage System Modeling for Hybrid Electric Vehicles

2000-04-02
2000-01-1564
The modeling of the energy storage system (ESS) of a Hybrid Electric Vehicle (HEV) poses a considerable challenge. The problem is not amenable to physical modeling without simplifying assumptions that compromise the accuracy of such models. An alternative is to build conventional empirical models. Such models, however, are time-consuming to build and are data-intensive. In this paper, we demonstrate the application of an artificial neural network (ANN) to modeling the ESS. The model maps the system's state-of-charge (SOC) and the vehicle's power requirement to the bus voltage and current. We show that ANN models can accurately capture the complex, non-linear correlations accurately. Further, we propose and deploy our new technique, Smart Select, for designing ANN training data.
Technical Paper

Improving the Aerodynamic Stability of a Practical, Low Drag, Aero-Stable Vehicle

2000-04-02
2000-01-1577
The aerodynamic drag of future low emission vehicles will need to be low. Unfortunately, vehicle shapes that result in low drag coefficients - of the order of 0.15 - are often aerodynamically unstable in crosswinds. The addition of wheels, transmission, radiators, suspension, steering, brakes, air ducts and wing mirrors can easily increase this drag coefficient to 0.24 and above and produce an undesirable lift distribution. The Aero-Stable Carbon Car (ASCC) is a research project, in conjunction with industrial partners, to design and build a practical 3 to 4 seat low drag car (CD less than 0.20) with an acceptable lift distribution (front to rear) which is also stable in crosswinds and in yaw through a series of low speed wind tunnel tests performed in the Cranfield College of Aeronautics 8′ × 6′ wind tunnel facility.
Technical Paper

An Integrated Study of the Ford PRODIGY Aerodynamics using Computational Fluid Dynamics with Experimental Support

2000-04-02
2000-01-1578
The Ford P2000 prototype vehicle represents Ford Motor Company's commitment towards environmental stewardship through high fuel efficiency and low tailpipe emission. Low aerodynamic drag coefficient (Cd), weight reduction, and power train efficiency improvements are required in order to accomplish the overall fuel economy target. The objective of this study is to establish an aerodynamic efficient body shape (Cd = .20) that meets the cost, weight, styling, package and fuel economy targets. Furthermore, this vehicle must be able to be operated and manufactured. A new computational fluid dynamics (CFD) method based on a lattice gas approach was piloted for developing and evaluating body shape design alternatives in support of the P2000 PRODIGY aerodynamic objective. Wind tunnel tests were performed to further explore the aerodynamic opportunities that are beyond the capability of the computational method as well as validate the CFD prediction.
Technical Paper

Collection Efficiency and Ice Accretion Characteristics of Two Full Scale And One 1/4 Scale Business Jet Horizontal Tails

2000-05-09
2000-01-1683
Collection efficiency and ice accretion calculations have been made for a series of business jet horizontal tail configurations using a three-dimensional panel code, an adaptive grid code, and the NASA Glenn LEWICE3D grid based ice accretion code. The horizontal tail models included two full scale wing tips and a 25% scale model. Flow solutions for the horizontal tails were generated using the PMARC panel code. Grids used in the ice accretion calculations were generated using the adaptive grid code ICEGRID. The LEWICE3D grid based ice accretion program was used to calculate impingement efficiency and ice shapes. Ice shapes typifying rime and mixed icing conditions were generated for a 30 minute hold condition. All calculations were performed on an SGI Octane computer. The results have been compared to experimental flow and impingement data.
Technical Paper

Nox Trap Control by Physically Based Model

1999-10-25
1999-01-3503
For a NOx trap catalyst to work properly, it is important that the times for the lean period and the rich spikes are correctly calculated in the engine management system (EMS). This paper deals with the development of a physically based NOx trap model for implementation in the EMS. The catalyst was divided into different segments (complete mixed cells) to correctly mimic the axial distribution of stored NOx and the axial temperature profile. Furthermore, the model included physical steps as adsorption, desorption, storage and release of NOx. The model also includes the storage and reduction of O2 and a simplified model of the heat release from the oxidation of the reductants. The model could successfully describe the process of storage and release in a short time interval. However, problems to describe the function of the NOx trap occurred after longer time in the vehicle because of inaccurate estimation of the input variables.
Technical Paper

AVL SDIS Mk.II - Low Cost Automotive FI Applied to 2-Stroke Engines for Future CARB - Regulations

1999-09-28
1999-01-3285
The basic Semi-Direct-Injection System (SDIS) which is already in production for PWC and applied to small 2-wheeler engines features a low-pressure fuel injection system injecting through the rear scavenge port window in the cylinder symmetry plane onto the piston crown. The patented new SDIS Mk.II System [1] injects through an (additional) scavenge port window that is positioned above the scavenge ports and is controlled by a window in the piston skirt. This new arrangement allows longer injection duration and also other injector positions and directions. A CFD simulation by AVL's FIRE-CFD-code with moving piston and exhaust gas dynamics compares the different injector positions and directions for WOT and rated speed and for a part throttle low speed case. The SDIS Mk.II injection system consists of mass-produced automotive parts thus giving a low cost approach for present 2-stroke engines requiring only moderate engine modifications.
Technical Paper

The Influence of Physical Input Parameter Uncertainties on Multidimensional Model Predictions of Diesel Engine Performance and Emissions

2000-03-06
2000-01-1178
Multidimensional models require physical inputs about the engine operating conditions. This paper explores the effects of unavoidable experimental uncertainties in the specification of important parameters such as the start of injection, duration of injection, amount of fuel injected per cycle, gas temperature at IVC, and the spray nozzle hole diameter. The study was conducted for a Caterpillar 3401 heavy-duty diesel engine for which extensive experimental data is available. The engine operating conditions include operation at high and low loads, with single and double injections. The computations were performed using a modified version of the KIVA3V code. Initially the model was calibrated to give very good agreement with experimental data in terms of trends and also to a lesser degree in absolute values, over a range of operating conditions and injection timings.
Technical Paper

Finite Element Modeling of Bolt Load Retention of Die-Cast Magnesium

2000-03-06
2000-01-1121
The use of die cast magnesium for automobile transmission cases offers promise for reducing weight and improving fuel economy. However, the inferior creep resistance of magnesium alloys at high temperature is of concern since transmission cases are typically assembled and joined by pre-loaded bolts. The stress relaxation of the material could thus adversely impact the sealing of the joint. One means of assessing the structural integrity of magnesium transmission cases is modeling the bolted joint, the topic of this paper. The commercial finite element code, ABAQUS, was used to simulate a well characterized bolt joint sample. The geometry was simulated with axi-symmetric elements with the exact geometry of a M10 screw. Frictional contact between the male and female parts is modeled by using interface elements. Material creep is described by a time hardening power law whose parameters are fit to experimental creep test data.
Technical Paper

Fastening of Light Weight Components with Elements Made of Aluminum

2000-03-06
2000-01-1118
Weigth saving is more and more recommended due to future demands for low energy consumption. Especially the automotive industry continues to search as diligently as ever for ways to build lighter vehicles. Therefore, the use of light weight metals, preferably aluminum and magnesium is on the rise. This contribution shows effective possibilities to fasten magnesium components, which require special fastening elements, if high stressed and reliable mechanical connections are necessary. Topics are fundamental mechanics of magnesium fastening as well as examples for applications with screws, rivet nut and self piercing rivet.
Technical Paper

Three-Dimensional Heat Transfer & Thermoelastic Deformation Predictions in Forward Lighting

2000-03-06
2000-01-1396
The thermal performance of an automotive forward-lighting assembly is predicted with a computational fluid-dynamics (CFD) program. A three-dimensional, steady-state heat-transfer model seeks to account for convection and radiation within the enclosure, conduction through the thermoplastic walls and lens, and external convection and radiation losses. The predicted temperatures agree well with experimental thermocouple and infrared data on the housing. Driven by the thermal expansion of the air near the bulb surface, counter-rotating recirculation zones are predicted within the enclosure. The highest temperatures in the plastic components are predicted on the inner surface of the shelf above the bulb where airflow rising from the hot bulb surface impinges.
Technical Paper

Process Design Tool for Rapid Estimation of Titanium Turning Cost

2000-05-16
2000-01-1733
The design tool developed addresses the need for timely and interactive manufacturing cost estimation early in product and process design. The particular context treated is finish turning of titanium. A collection of simple physical models of the most relevant phenomena are combined in a computer program. Model simplicity enables rapid delivery of results in the form of cutter temperature, force, and wear predictions. Knowledge of the specific nature of titanium machining is included. Cutter wear predictions agree well with experimental data. Process conditions and cutter geometry that result in minimum direct cost can be provided on time scales that are a fraction of the time to actually machine the part. This design tool is most appropriate for cost estimation of jobs in which cutters and/or machining time are a significant part of manufacturing cost.
Technical Paper

Optimum SI Engine Based Powertrain Systems for Lightweight Passenger Cars

2000-03-06
2000-01-0827
This paper compares the fuel consumption of a lightweight passenger car for three different SI engine concepts, all with rated power of about 40 kW: a classical SI engine with moderate maximum speed, a low-displacement but high-speed engine that exploits the maximum allowed mean-piston speed and a low-displacement but highly supercharged engine with moderate maximum speed. All engines are simulated with a thermodynamic process simulator, the results of the supercharged version are validated with experiments. For each engine, a CVT and an automated gearbox is considered. Fuel consumption is estimated with a quasi-static driving cycle simulator which is based on engine fuel consumption maps and physical models of the vehicle with all its relevant subsystems. The simulations are performed for constant vehicle speed as well as for US and European driving cycles.
Technical Paper

A Neuro-Fuzzy Based Method for the Design of Combustion Engine Dynamometer Experiments

2000-03-06
2000-01-1262
Because of increasing requirements for low emissions and fuel consumption, combustion engines are getting more and more control inputs, like multiple injection, exhaust gas recirculation (EGR), turbocharger valve position (TVP), variable valve timing (VVT), etc. With the addition of manipulated variables, the required measurement time for obtaining the steady-state characteristics and control look-up tables rises exponentially. A comprehensive design of the measurement experiment is becoming more and more essential. The objective is to measure the engine characteristics and properties with a minimum number of measurement points (with firstly concentrating on the stationary behavior). A new methodology is presented to automatically determine characteristic mappings by incorporating prior knowledge. Since physical modeling of the engine behavior is mostly not appropriate, prior knowledge for experimental design is derived by evaluating measurement data.
Technical Paper

Cavitation in Real-Size Multi-Hole Diesel Injector Nozzles

2000-03-06
2000-01-1249
A production six-hole conical sac-type nozzle incorporating a quartz window in one of the injection holes has been used in order to visualize the flow under cavitating flow conditions. Simultaneous variation of both the injection and the back chamber pressures allowed images to be obtained at various cavitation and Reynolds numbers for two different fixed needle lifts corresponding to the first- and the second-stage lift of two-stage injectors. The flow visualization system was based on a fast and high resolution CCD camera equipped with high magnification lenses which allowed details of the various flow regimes formed inside the injection hole to be identified. From the obtained images both hole cavitation initiated at the top inlet corner of the hole as well as string cavitation formed inside the sac volume and entering into the hole from the bottom corner, were identified to occur at different cavitation and Reynolds numbers.
Technical Paper

Optimal Operation of a Combined NOx/Oxygen Zirconia Sensor Under Lean Burn Conditions

2000-03-06
2000-01-1204
This article describes the development and tests of a combined NOx/oxygen Zirconia sensor. To achieve accurate NOx and oxygen measurements under lean-burn conditions, preliminary model scale experiments with a premixed methane-air burner are carried out with current production oxygen sensors as well as with our own oxygen probe. It is found from these tests that accurate oxygen sensing requires sensor operating temperatures much lower than usually set, about 600°C. Moreover, this temperature is a good compromise for NOx sensitivity and time response of the sensor. Accordingly, a new NOx/O2 sensor has been designed and prototyped. Held in a spark plug type housing, it simultaneously monitors the NOx and oxygen content of the exhaust gas. Over the wide 02 range of interest, model scale tests of the sensor with burnt gases have shown promising agreement with laboratory analysers.
X