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Technical Paper

Force-Stroke-Curve of Gas Springs

The use of gas springs with a surge tank to generate blank holding forces in drawing tools is increasing. These gas spring systems are characterized by an almost constant behaviour of the spring force over the spring displacement. To prevent an increase of the normal pressure with increasing stroke in a drawing process, it is advantageous to obtain a degressive force-displacement behaviour of the gas springs. For this reason, a gas spring system was developed to realize a decrease of the blank holding forces over the stroke without large additional expenditure. The technical realization takes place in an exact controlling of the upper and lower pressure chamber of the nitrogen cylinder.
Technical Paper

Process Modeling in the Life Cycle Design - Environmental Modeling of Joining Technologies within the Automotive Industry -

For integrating Life Cycle Assessment into the design process it is more and more necessary to generate models of single life cycle steps respectively manufacturing processes. For that reason it is indispensable to develop parametric processes. With such disposed processes the aim could only be to provide a tool where parametric environmental process models are available for a designer. With such a tool and the included models a designer will have the possibility to make an estimation of the probable energy consumption and needed additive materials for the applied manufacturing technology. Likewise if he has from the technical point of view the opportunity, he can shift the applied joining technology in the design phase by changing for instance the design.
Technical Paper

Fundamental Research and Draw Die Concepts for Deep Drawing of Tailored Blanks

According to the present state of knowledge, the use of “Tailored Blanks” with different sheet thicknesses and/or grades represents an interesting manufacturing alternative in the design and development of sheet metal parts in the automotive industry. In order to assess the forming behavior, fundamental research was conducted on laser and mash seam welded blanks. Based on this experimental findings, a segmented draw die was designed and built to determine the limits of the metal forming process by deep drawing of car body parts. The results with this draw die showed that a uniform blankholder pressure must be guaranteed during the forming process in the flange region of the part. This necessitated definite slots in the region of the weld line for the mash seam welded blanks. Furthermore, a die concept was presented to enable an equalization of both sheet thickness steps and sheet thickness fluctuations, without requiring replacement of the respective draw die components.
Technical Paper

The Quantification of Laser-Induced Incandescence (LII) for Planar Time Resolved Measurements of the Soot Volume Fraction in a Combusting Diesel Jet

Quantitative Laser-Induced Incandescence (LII) has been applied to investigate the soot formation in a combusting Diesel jet for various conditions. For the quantification of the LII signal the local soot volume fraction of a diffusion flame burner was measured using laser beam extinction. These data were used for the calibration of the LII signal. The investigation of the soot formation in a combusting Diesel jet was performed in a high pressure, high temperature combustion chamber with optical access. A wide range of pressure (up to 10 MPa) and temperature (up to 1,500 K) conditions could be covered using a hydrogen precombustion, which is initiated inside the chamber before fuel injection. The influence of different gas atmospheres have been investigated by varying the gas composition (H2, O2 and N2) inside the chamber.
Technical Paper

Combination of Hydraulic Multipoint Cushion System and Segment-Elastic Blankholders

The costs for development and production of draw dies for car outer panels are extremely high and should be reduced. Furthermore it is necessary to reduce the time for developing, designing and producing the dies for the production of parts. This paper discusses new press techniques, die designs and an adjustment program for press operators. The trend goes to single action presses with CNC-controlled multipoint cushion systems in the press table and to special designed dies. These systems lead to a more robust and reproducible forming process with improved product quality. This paper deals with: Cushion Systems, New Binder Designs for Draw Dies for Sheet Metal Automotive Parts, New Computer Program to Adjust the Blankholder Forces of Modern Hydraulic Cushion Systems of Single Action Presses and Pressure Measurement for Detecting the Pressure between the Blank and the Binders of Draw Dies for Sheet Metal Automotive Parts.
Technical Paper

Measurement of Reference Dynamic Pressure in Open-Jet Automotive Wind Tunnels

In automotive open-jet wind tunnels reference velocity is usually measured in terms of a static pressure difference between two different cross-sectional areas of the tunnel. Most commonly used are two sections within the nozzle (Method 1: ΔP-Nozzle). Sometimes, the reference velocity is deduced from the static pressure difference between settling chamber and plenum (Method 2: ΔP-Plenum). Investigations in three full-scale open-jet automotive wind tunnels have clearly shown that determination of reference dynamic pressure according to ΔP-Plenum is physically incorrect. Basically, all aerodynamic coefficients, including drag coefficient, obtained by this method are too low. For test objects like cars and vans it was found that the error ΔcD depends on the test object's drag blockage in an open-jet wind tunnel.
Technical Paper

Quantitative 2D LIF Measurements of Air/Fuel Ratios During the Intake Stroke in a Transparent SI Engine

The fluorescence characteristics of different carbonyl compounds were investigated in a pressurized bomb using an excimer laser (308 nm) for excitation. The partial pressure of the carbonyl compounds and air was varied between 0 - saturation pressure and 0 - 5 bar, respectively. The fluorescence signal of different ketones increased almost linearly with vapour pressure. It was found to be almost independent of air pressure indicating only a weak quenching influence of oxygen. Ethylmethylketone (EMK) has a boiling temperature and vapour pressure similar to gasoline. Therefore, the applicability of EMK for measuring 2-D fuel distributions in a combustion chamber was tested in a transparent SI square piston engine. EMK was injected into the intake manifold by a conventional injector for studying the fuel/air mixing during the intake and compression stroke at 1.000 rpm. From the 2-D fluorescence signals 2-D air/fuel ratios were calculated using calibration data from bomb experiments.
Technical Paper

Development of an Enhanced Mean-Value-Model for Optimization of Measures of Thermal-Management

In this paper, a simulation approach is introduced which takes into account all relevant heat sources and sinks in the combustion engine and in the engine compartment. With this approach, it is possible to calculate the appearing power flow and enthalpy flow as well as the component temperatures. Therefore, the complex thermodynamic and friction processes in the engine are described as simple as possible; the complete system can still be described reliably within certain limits, and the effects of different thermal optimization measures can be shown. It is an essential point for the modeling that only two integral quantities are necessary (the high pressure efficiency and the high pressure wall heat loss) for the complete combustion model.
Technical Paper

Presenting a Fourier-Based Air Path Model for Real-Time Capable Engine Simulation Enhanced by a Semi-Physical NO-Emission Model with a High Degree of Predictability

Longitudinal models are used to evaluate different vehicle-engine concepts with respect to driving behavior and emissions. The engine is generally map-based. An explicit calculation of both fluid dynamics inside the engine air path and cylinder combustion is not considered due to long computing times. Particularly for dynamic certification cycles (WLTC, US06 etc.), dynamic engine effects severely influence the quality of results. Hence, an evaluation of transient engine behavior with map-based engine models is restricted to a certain extent. The coupling of detailed 1D-engine models is an alternative, which rapidly increases the model computation time to approximately 300 times higher than that of real time. In many technical areas, the Fourier transformation (FT) method is applied, which makes it possible to represent superimposed oscillations by their sinusoidal harmonic oscillations of different orders.
Technical Paper

Valve Flow Coefficients under Engine Operation Conditions: Pressure Ratios, Pressure and Temperature Levels

Engine valve flow coefficients are not only used to characterize the performance of valve/port designs, but also for modelling gas exchange in 0D/1D engine simulation. Flow coefficients are usually estimated with small pressure ratios and at ambient air conditions. In contrast, the ranges for pressure ratio, pressure and temperature level during engine operation are much more extensive. In this work the influences of these three parameters on SI engine poppet valve flow coefficients are investigated using 3D CFD and measurements for validation. While former investigations already showed some pressure ratio dependencies by measurement, here the use of 3D CFD allows a more comprehensive analysis and a deeper understanding of the relevant effects. At first, typical ranges for the three mentioned parameters during engine operation are presented.