Analysis of the Piston Ring/Liner Oil Film Development During Warm-Up for an SI Engine

A one-dimensional ring-pack lubrication model developed at MIT is applied to simulate the oil film behavior during the warm-up period of a Kohler spark ignition engine [1]. This is done by making assumptions for the evolution of the oil temperatures during warm-up and that the oil control ring during downstrokes is fully flooded. The ring-pack lubrication model includes features such as three different lubrication regimes, i.e. pure hydrodynamic lubrication, boundary lubrication and pure asperity contact, non-steady wetting of both inlet and outlet of the piston ring, capability to use all ring face profiles that can be approximated by piece-wise polynomials and, finally, the ability to model the rheology of multi-grade oils. Not surprisingly, the simulations show that by far the most important parameter is the temperature dependence of the oil viscosity. This dependence is subsequently examined further by choosing different oils. The baseline oil is SAE 10W30 and results are compared to those using the SAE 30 and the SAE 10W50 oils

In Situ Analysis of Bacterial Extracellular Polymeric Substances from a Pseudomonas fluorescens Biofilm by Combined Vibrational and Single Molecule Force Spectroscopies

International audienceExtracellular polymeric substances (EPS) play an important role in biofilm cohesion and adhesion to surfaces. EPS of a P. fluorescens biofilm were characterized through their vibrational spectra (infrared and Raman) and their conformational properties using single molecule force spectroscopy with specific probes for glucose, galactose, and N-acetyl glucosamine-rich EPS. Vibrational spectra evidenced the overproduction of glycogen and other carbohydrates in the biofilm. The conformational analysis was performed from both the freely jointed chain (FJC) and worm like chain (WLC) models. The results of the FJC fittings showed highly ramified and/or folded structures for all the detected EPS with molecular elongations up to 1000-2500 nm, and typical Kuhn lengths of glycogen macromolecules. The characteristics of galactose-rich EPS have been found to be significantly different from those of glucose- and N-acetyl glucosamine-rich EPS. On the basis of the theoretical fittings with the WLC model, our results suggested that carbohydrates may be associated with peptide domains