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QUEUE

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Turbulent flow in an intake-manifold

Three-dimensional, turbulent fluid flow analysis with computational methods has emerged as a viable tool in the design process of engine components for passenger cars. If applied in the early stages of the component development such analysis can help reduce the product development time drastically, and may support the design engineer to evaluate several competing design aspects before product completion. However the grid generation for complex geometries still poses a difficult and time consuming taks which strongly influences the accuracy of the numerical solution. The present paper studies the numerical solution of the flow in an inlet-manifold of a five-cylinder engine with two intake-ports for each cylinder. A fast and reliable grid generation technique is discussed in detail. The finite volume based Navier-Stokes solver with schemes of first and second order accuracy for the convective terms is used. Numerical results at several mass flow rates and different boundary conditions at the intake ports are compared with measurements. Finally, the computational results are discussed with respect to their applicability to support the design process of an inlet-manifold.     

Thermisch induzierter Abbau von Disaccharid-Amadori-Verbindungen in quasi wasserfreiem Reaktionsmilieu

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Improved accuracy and convergence of discretized population balance for aggregation: The cell average technique

A new discretization method for aggregation equations is developed. It is compared to the fixed pivot technique proposed by Kumar and Ramkrishna (1996a. On the solution of population balance equations by discretization—I. A fixed pivot technique. Chemical Engineering Science 51, 1311-1332). The numerical results for aggregation problems by discretized population balances are consistently overpredicting and diverge before the gelling point in the case of a gelling kernel. The present work establishes a new technique which assigns the particles within the cells more precisely. This is achieved by taking first the average of the newborn particles within the cell and then assigning them to the neighboring nodes such that pre-chosen properties are exactly preserved. The new technique preserves all the advantages of the conventional discretized methods and provides a significant improvement in predicting the particle size distribution (PSD). In addition, it is found that the technique is a powerful tool for the computation of gelling problems. The effectiveness of the technique is illustrated by application to several aggregation problems for suitably selected aggregation kernels including physically relevant kernels.     

Direct Laser Sintering of Al2O3–SiO2 Dental Ceramic Components by Layer-Wise Slurry Deposition

This publication presents a solid freeform fabrication technique for ceramics in the alumina–silica system by layering binder-free, high-loaded ceramic slurries, followed by selective laser sintering. The low melting silica phase and the reaction sintering between silica and alumina favor the rapid prototyping of pure ceramic parts. On the basis of electroacoustic and viscosity measurements, stable slurries from Al₂O₃/SiO₂ powder mixtures and water with a high fluidity have been prepared for the layer deposition with a doctor blade like in tape casting. Layers with a thickness of about 100 μm were processed. It was found in laser parameter studies that ceramic parts can only be obtained using special alumina contents and laser parameters. But the biphasic approach may allow greater flexibility in the processing regime than is afforded by the use of just one material. The microstructure of these parts depends mainly on the temperature gradient induced by the laser absorption and thermal conduction. The wet shaping facilitates laser-sintered parts with a relatively high density, which could be increased by a thermal post-treatment.     

B. Erteilte ausl?ndische Patente

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Zur Bestimmung des Unverseifbaren

Zusammenfassung Zur mengenmäßigen Bestimmung des Unverseifbaren (Kohlenwasserstoffe neben Cholesterin) wird eine Methode beschrieben, durch die insbesondere der Cholesterinanteil quantitativ erfaßt weden soll. Nach der Verseifung des Fettes mit alkoholischer Kalilauge wird in Petroläther gelöst und die Seife mit Wasser ausgeschüttelt. Ein aliquoter Teil der verbleibenden Petrolätherlösung wird im gewogenen Kolben verdampft und der Rückstand nach dem Trocknen gewogen. Bei der Berechnung wurde der Übergang eines gewissen Anteils Petroläther in die wässerige Seifenlösung in Rechnung gestellt. Die Ausbeute beträgt dann 78% des zugesetzten Cholesterins. Bei weiteren Versuchen zeigte es sich, daß die Cholesterinausbeute nach dem früheren Verfahren 27% beträgt. Da Paraffine nach beiden Methoden zu 100% wieder gefunden werden, läßt sich ein Gemisch von Paraffinen und Cholesterin anteilmäßig durch Kombination beider Verfahren bestimmen.