Showing papers by "Ulrich Maas published in 1989"
01 Jan 1989
TL;DR: In this paper, the carbon monoxide-hydrogen-oxygen system is simulated by solving the corresponding conservation equations (i.e., conservation of mass, energy, momentum and species mass) for one-dimensional geometries using a detailed reaction mechanism and a multi-species transport model.
Abstract: Ignition processes in the carbon monoxide-hydrogen-oxygen system are simulated by solving the corresponding conservation equations (i.e. conservation of mass, energy, momentum and species mass) for one-dimensional geometries using a detailed reaction mechanism and a multi-species transport model. An additional source term in the energy conservation equation allows the treatment of induced ignition, and a realistic model for the destruction of reactive species at the vessel surface is used to treat auto-ignitions in static reactors. Spatial discretization using finite differences and an adaptive grid point system leads to a differential/algebraic equation system which is solved numerically by extrapolation or backward differencing codes. Minimum ignition energies are calculated for various mixture compositions and radii of the external energy source. Ignition limits are computed, and a sensitivity analysis shows the rate-limiting reactions.
68 citations
TL;DR: In this article, an implicit solution of the Navier-stokes equations including detailed chemistry in two space dimensions is performed by a method of lines, where spatial discretization on a two-dimensional grid that is adapted statically in two spatial directions leads to a differential/ algebraic equation system which is solved numerically by an implicit extrapolation method to overcome stiffness problems caused by the multiscale character of the system considered.
Abstract: Globally implicit solutions of the compressible Navier-Stokes equations including detailed chemistry in two space dimensions are performed by a method of lines. This has become possible by the recent development of numerical methods for the solution of stiff differential /algebraic equation systems together with the availability of fast computers with high storage capacity. Computations of ignition processes are performed by solving the corresponding conservation equations (i.e., conservation of total mass, momentum, energy, and species mass) using a detailed reaction mechanism for the ozone-oxygen system (consisting of six elementary reactions) and a multispecies transport model. Thermal ignition is simulated by an additional source term in the energy conservation equation. Spatial discretization on a two-dimensional grid that is adapted statically in two spatial directions leads to a differential/ algebraic equation system which is solved numerically by an implicit extrapolation method to overcome stiffness problems caused by the multiscale character of the system considered. Results are presented for the simulation of a laser-induced thermal ignition in an ozone-oxygen mixture in a cylindrical reaction vessel. However, the method can be generally applied to two-dimensional reactive flows in relatively simple geometries.
44 citations
TL;DR: In this paper, an implicit extrapolation method is used to overcome stiffness problems caused by the multiscale character of the system considered, which can be applied to two-dimensional reactive flows in relatively simple geometries.
Abstract: New numerical methods for the solution of stiff partial differential equation systems together with the availability of fast computers with high storage capacities now allow the globally implicit simulation of instationary combustion processes in two space dimensions. Computations of ignition processes are performed by solving the corresponding conservation equations (i.e. conservation of total mass, energy, momentum, and species mass) using a detailed reaction mechanism for the ozone —oxygen system (consisting of six elementary reactions) and a multispecies transport model. Thermal ignition is simulated by an additional source term in the energy conservation equation. Spatial discretization on a two-dimensional grid that is adapted statically in one spatial direction leads to a differential-algebraic differential equation system which is solved numerically by an implicit extrapolation method to overcome stiffness problems caused by the multiscale character of the system considered. Results are presented for the simulation of a laser-induced thermal ignition of an ozone —oxygen mixture in a cylindrical reaction vessel. However, the method can be generally applied to twodimensional reactive flows in relatively simple geometries.
16 citations
TL;DR: Verbrennungsprozesse beruhen auf einem komplizierten Wechselspiel von Stromung, Transportprozessen und chemischen Reaktionen as mentioned in this paper.
Abstract: Verbrennungsprozesse beruhen auf einem komplizierten Wechselspiel von Stromung, Transportprozessen und chemischen Reaktionen. Die rechnerische Simulation - und damit ein quantitatives Verstandnis und die Moglichkeit der Extrapolation zu experimentell nicht oder schwer zuganglichen Bedingungen - ist erst in den letzten zehn Jahren moglich geworden.