Today's car designers ask for compact and light-weighted headlamps with several new functional features and special stylistic elements. This yields in new lighting technology such as modern free form and ellipsoid module reflectors with small dimensions and the need to use highly sophisticated Materials. Both of this is sensitive to the amount of temperature and at a critical level may cause irreversible damage. Therefore, it is necessary to predict temperature loads at an early development stage in order to ensure new headlamp concepts and to shorten development time. An approach to calculate and analyze temperatures in headlamps by continuum fluid dynamic methods (CFD) is presented which can be compared and correlated to measurements carried out with infrared thermography and demonstrates the benefit of this method. In this paper a temperature simulation of the AUDI A2 ECE headlamp is shown. First, temperature measurements are described to generate temperature values which can be used to compare the simulation results with reality. Temperature measurement is performed by touching method or contact method with 4 thermo-elements (NiCr/Ni) or with resistance thermo elements (Pt 100). Thermographic devices make it possible to get the temperature distribution of a whole surface, especially the position of the highest temperature points (,hot spots'). To perform a sophisticated simulation of the temperature loads in headlamps it is necessary to find a physical representation of the system. This is done by a set of partial differential equations. In this case, the partial differential equations governing fluid flow, heat transfer and radiation exchange (surface-to-surface, surface-to-fluid and fluid-to-fluid) are the continuity equation, the Navier-Stokes equations and the energy balance. An approximate method (continuum fluid dynamics, CFID) has to be used in practical cases to determine the solution for these equations. The general solution method CFD is described briefly. First, the physical principles and equations are presented for a better understanding. Then, boundary conditions and model assumptions as well as used material parameters are shown. Finally, the discretization method and numerical algorithm for the finite element method (FEM) is described shortly.
Temperature loads in headlamps
Temperaturbelastung in Scheinwerfern
2002
10 Seiten, 12 Bilder, 3 Tabellen, 11 Quellen
Aufsatz (Konferenz)
Deutsch
Navier-Stokes-Gleichung , Scheinwerfer , Temperaturberechnung , Temperaturverteilung , rechnerunterstützte Simulation , Kontinuumsmechanik , Strömungslehre , Fluidmechanik , Temperaturmessung , Thermographie , Infrarotdetektor , Thermoelement , Finite-Elemente-Methode , Kraftfahrzeug , Fernlicht , Abblendlicht
Temperature loads in headlamps
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