In recent years, the computational fluid dynamics method has developed into very useful tools for investigating the oil flow and the no-load losses in geared transmissions. It has neither restriction on the housing shape nor limitations on the lubrication configuration. For this work, a computational fluid dynamics method model based on the finite volume method of a single-stage, injection-lubricated gearbox was built. The influence of different parameters including the injection volume, oil viscosity, and gear speed on the oil supply and distribution were investigated. The results also include a comparison of the simulated no-load losses with empirical no-load loss equations. This work provides first results on computational fluid dynamics method investigations of injection-lubricated geared transmissions and a starting point for comprehensive validation and more complex modeling.

Air-core–liquid-ring (ACLR) atomization presents a specific type of internal mixing pneumatic atomization. It can be used for disintegration of high viscous feed liquids into small droplets at relatively low gas consumptions. However, the specific principle of ACLR atomization is still under research and no guidelines for process and atomizer design are available. Regarding literature on pre-filming atomizers, it can be hypothesized for ACLR atomization that the liquid film thickness inside the exit orifice of the atomizer, as well as the resulting spray droplet sizes decrease with increasing air-to-liquid ratio (ALR) and decreasing feed viscosity. In this study, the time dependent liquid film thickness inside the exit orifice of the atomizer was predicted by means of computational fluid dynamics (CFD) analysis. Results were compared to high speed video images and correlated to measured spray droplet sizes. In conclusion, the hypothesis could be validated by simulation and experimental data, however, at high viscosity and low ALR, periodic gas core breakups were detected in optical measurements. These breakups could not be predicted in CFD simulations, as the simplification of an incompressible gas phase was applied in order to reduce computational costs and time. Nevertheless, the presented methods show good potential for improvement of atomizer geometry and process design as well as for further investigation of the ACLR atomization principle.

Amino acids have been widely used in protein formulations to increase the protein’s stability. In this study, amino acids have been introduced as soft-templates to control the nucleation of proteins....

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One of the most crucial parameters in protein crystallization is pH, as it governs the protein's electrostatic interactions. However, the fundamental role of pH on crystallization still remains unknown. Here, we systematically investigated the crystallization of human insulin (isoelectric point 5.3) at various pHs between 6.0 and 6.7 at different supersaturation ratios, up to 20.9. Our results demonstrate that the pH has an opposing effect on solubility and nucleation rate as a shift in pH toward a more basic milieu increases the solubility by 5-fold while the onset of nucleation was accelerated by a maximum of 8.6-fold. To shed light on this opposing effect, we evaluated the protein−protein interactions as a function of pH by measuring the second virial coefficient and hydrodynamic radius and showed that a change in pH of less than one unit has no significant impact on the protein− protein interactions. As it is widely understood that the increase in protein solubility as a function of pH is due to the increase in the repulsive electrostatic interactions, we have demonstrated that the increase in insulin solubility and decrease in the onset of nucleation are independent of the protein−protein interactions. We hypothesize that it is the electrostatic interactions between both ions and solvent molecules and the protein residues that are governing the crystallization of human insulin. The findings of this study will be of crucial importance for the design of novel crystallization pathways.

This paper describes the effect of specimen size on slow crack growth and fracture toughness of the titanium alloy Ti-6A1-4V. The load versus crack opening displacement curve rises steeply after reaching the end of the linear part. Stable crack extension starts within the linear part of the P-v-curve. The crack growth resistance curve is independent of thickness B until KQ in the range 2 < B < 20 mm, leading to the conclusion that slow crack growth can occur in plane strain. The secant method, leading to KQ at 2 percent crack extension, yields a specimen geometry dependent fracture toughness. KQ increases with width, W and is only slightly dependent on thickness, B. The consequences of this behavior for fracture toughness determination in connection with the ASTM recommendation are discussed.

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