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Technical Paper

Grid Independence Validation and Numerical Simulation of an Opposed-Piston Free-Piston Engine

To evaluate the grid independence of the in-cylinder numerical simulation, the combustion chamber model of an opposed-piston free-piston engine was divided into three styles: structured, unstructured, and hybrid meshes. Furthermore, the grid independence of the hybrid mesh was analyzed using different grid resolutions. In order to avoid the influence of subjective judgments, the grid resolution is introduced to characterize the degree of grid refinement, combined with the grid convergence index (GCI) to assess the convergence of simulation. The results show that there are differences in the flow fields for the different grid styles. In addition, the hybrid mesh captured more small-scale swirls around the intake and exhaust ports. When the resolution reached 12, the GCI was less than 6%, indicating that the numerical simulation was impervious to the grid resolution. Moreover, the mixing distribution hardly changed when the resolution reached 12.

Heavy Duty Vehicle Cooling Test Code

The purpose of this SAE Recommended Practice is to establish a testing procedure to determine the performance capability of heavy duty vehicle cooling systems to meet Original Equipment Manufacturer or end user thermal specifications to ensure long term reliable vehilcle operations. The recommendations from the present document are intended for heavy-duty vehicles including, but is not limited to, on- and off-highway trucks, buses, cranes, drill rigs, construction, forestry and agricultural machines.
Technical Paper

The Behavior of Fuel Droplets on a Heated Substrate

The processes of surface wetting and film evaporation play a major role in any application using liquid fuels. Since the behavior of entire multi-liquid films is influenced by many simultaneously occurring physical processes, exact modeling is not yet possible. In order to reduce the complexity and to determine the basic effects in the spreading and evaporation of multi-component films, this study was carried out by placing single 5 μl droplets on a heated metal surface. Various alkanes, ethanol, and mixtures, as well as real gasoline, were studied at surface temperatures between 69°C and 140°C. To describe the processes qualitatively and determine the time-dependent wetted surface area, the droplets were visualized using cameras. With the results, it was possible to determine the course of the wetted surface over time and to compare different liquids under varying surface temperatures.