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The instability of a falling film under high pressure (droplet formation) was characterized by the dimensionless Reynolds, Weber, and fluid-film numbers and could be predicted in a characteristic diagram. Incipient droplet formation was achieved with the given material properties of the system, i.e., at a constant KF number, by increasing the volumetric flowrate of the liquid phase.The investigations were performed with the material systems a-tocopheroVC02 and squalane/C02 in the pressure ranges between 8 and 35 MPa and 6 and 12 MPa, respectively, at four different temperatures between 313 and 353 K. The volumetric flowrate of the liquid phase was varied between 10 and 300 mumin, whereas the speed of the supercritical gas phase irl counter-current flow to the falling film in the falling-film cell was kept constant at 7 m d s . The high-pressure falling-film cell used for this purpose had an external diameter of 104 mm, an internal diameter of 34 mm, and a total length of 710 mm. The diameter and length of the cylindrical falling-film carrier were 10 and 500 mm, respectively.

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-Idling losses constitute a significant amount of the fuel consumption of internal combustion engines. Therefore, shutting down the engine during idling phases can improve its overall efficiency. For driver acceptance a fast restart of the engine must be guaranteed. A fast engine start can be performed using a powerful electric starter and an appropriate battery which are found in hybrid electric vehicles, for example. However, these devices involve additional cost and weight. An alternative method is to use a tank with pressurized air that can be injected directly into the cylinders to start the engine pneumatically. In this paper, pneumatic engine starts using camshaft driven charge valves are discussed. A general methodology for an air-optimal charge valve design is presented which can deal with various requirements. The proposed design methodology is based on a process model representing pneumatic engine operation. A design example for a two-cylinder engine is shown, and the resulting optimized pneumatic start is experimentally verified on a test bench engine. The engine's idling speed of 1200 rpm can be reached within 350 ms for an initial pressure in the air tank of 10 bar. A detailed system analysis highlights the characteristics of the optimal design found.Re´sume´-Me´thodologie pour le design des valves de chargement ope´re´es par arbre a`cames -Les pertes a`vide repre´sentent une partie essentielle de la consommation des moteurs a`combustion interne. La mise a`l'arreˆt du moteur pendant la marche a`vide peut, par conse´quent, en ame´liorer son efficacite´ge´ne´rale. Pour eˆtre accepte´par le conducteur, le rede´marrage du moteur doit eˆtre rapide. On peut re´aliser ce de´marrage rapide du moteur, moyennant un de´marreur e´lectrique puissant conjointement avec un accumulateur approprie´, solution retenue par exemple, pour les ve´hicules a`syste`me hybride e´lectrique. Cependant, ces derniers augmentent le couˆt et le poids. Une alternative consiste dans le de´marrage pneumatique du moteur en utilisant de l'air comprime´stocke´dans un re´servoir sous pression et injecte´directement dans les cylindres. Cette e´tude pre´sente le de´marrage pneumatique du moteur en utilisant des valves de chargement commande´es par arbre a`cames. On pre´sente une me´thodologie visant a`une consommation de l'air optimale en mesure de respecter des exigences diffe´rentes. La de´marche propose´e s'appuie sur le mode`le d'un processus repre´sentant l'ope´ration pneumatique du moteur. La ve´rification expe´rimentale du de´marrage pneumatique est re´alise´e et optimise´e sur un moteur 2 cylindres sur banc d'essai. Avec une pression initiale de 10 bar dans le reservoir d'air, la vitesse de rotation a`vide de 1 200 tr/min peut eˆtre atteinte en 350 ms. Une analyse de´taille´e confirme les caracte´ristiques du syste`me optimise´.

The interfacial tension of the binary system a-tocopherol/carbon dioxide was measured using the pendant drop method in the pressure range between 10 and 37 MPa at nine different temperatures: 313,333,343,353,363,373,383, 393, and 402 K. At every interfacial tension measurement, densities of both the liquid and the supercritical gas phase were also determined as the knowledge of these values is essential for calculating interfacial tension from the shape and size of drops. The interfacial tension decreases with rising pressure at a constant temperature and increases with increasing temperature at a constant pressure. The interfacial tension was found to be mainly a function of the mutual solubility of the two system components and of the density of pure carbon dioxide.