Spatially Resolved Experimental and Numerical Investigation of the Flow through the Intake Port of an Internal Combustion Engine

Modern spark-ignited internal combustion engines have intake ports designed to introduce high levels of so-called “tumble” charge motion. Correspondingly high shear rates can lead to high fluctuations and turbulence within the combustion chamber. A suitable test case to characterize the intake flow is a steady-state flow bench. Although routinely used in the engine development process to determine the global discharge coefficients, only a few detailed numerical and experimental studies use this test case to analyze the flow in the vicinity of the valve with high spatial and temporal resolution. In this paper, we combined highly resolved two-dimensional, two-component Particle Image Velocimetry (PIV) measurements and numerical simulations using a Detached-Eddy Simulation (DES) model to characterize engine-relevant flow features on a flow bench. The spatial resolution of numerical simulations on two different grids is assessed and compared to that of the PIV measurement. The results of simulations and experiment are then compared in terms of their mean and fluctuation velocity fields and the jet orientation. A detailed study of the area around the valve seats investigates the validity of wall functions in this region. Finally, we examine structures induced by vortex-shedding at the valve stem and if they are transported into the combustion chamber

Mechanism of Action and Antiviral Activity of Benzimidazole-Based Allosteric Inhibitors of the Hepatitis C Virus RNA-Dependent RNA Polymerase

The RNA-dependent RNA polymerase of hepatitis C virus (HCV) is the catalytic subunit of the viral RNA amplification machinery and is an appealing target for the development of new therapeutic agents against HCV infection. Nonnucleoside inhibitors based on a benzimidazole scaffold have been recently reported. Compounds of this class are efficient inhibitors of HCV RNA replication in cell culture, thus providing attractive candidates for further development. Here we report the detailed analysis of the mechanism of action of selected benzimidazole inhibitors. Kinetic data and binding experiments indicated that these compounds act as allosteric inhibitors that block the activity of the polymerase prior to the elongation step. Escape mutations that confer resistance to these compounds map to proline 495, a residue located on the surface of the polymerase thumb domain and away from the active site. Substitution of this residue is sufficient to make the HCV enzyme and replicons resistant to the inhibitors. Interestingly, proline 495 lies in a recently identified noncatalytic GTP-binding site, thus validating it as a potential allosteric site that can be targeted by small-molecule inhibitors of HCV polymerase