Search Results

This paper presents the CFD activities performed for the analysis of the aerodynamic phenomena related to the nose shape of the French High-Speed train and the results obtained on a reference shape. The methodology focuses on nose shape optimization associated to the reduction of drag and to the damping of the pressure waves generated during tunnel entry. Two main approaches are detailed. On one side, Finite Element Navier-Stokes simulations are used to analyze the main free field features, the results being compared to those obtained on a scale mock-up. On the other side, a specific technique, involving adaptive remeshing with Finite Elements, solving the Euler equations, is developed and used in order to simulate the generation of pressure waves due to tunnel entry.

A CAD/CAE procedure has been used for the analysis of the flow in an intake port-valve-cylinder assembly of a DI Diesel engine. The flow was simulated for both, steady state conditions and transient motored situation during intake and compression strokes. The characteristics of the helical port are analyzed, for the steady state case, in terms flow rate, generation of angular momentum flux and induced in-cylinder flow motion. The results of the simulation were correlated with experimental results, consisting of oil film visualizations on valve and intake port surfaces, and of local velocity measurements in the cylinder. The transient flow simulation shows the different characteristics of the flow motion in cylinder and piston bowl during intake and compression strokes. It was observed that the swirl generating capacity of the valve is different between the valve opening and closing phases.

This paper describes a CAD/CAE approach for the numerical simulation of port-valve-cylinder flow in reciprocating engines. This approach complements the classical experimental approach, using steady state and transient measurements, and it can replaces experiments at the design stage. Computer software and hardware environment are discussed, including aspects concerning solid body modeling, mesh generation, CFD calculation, CPU requirements and results analysis. The simulation approach is assessed and validated through comparison with axisymmetric laboratory test results and actual engine configuration test results from MAZDA. The paper focuses on steady state analysis with open valve, and discusses the reproduction, by simulation, of flow features in the port- valve region, and their interaction with the flow on the entire port-valve-cylinder path.