Flow Structures and Losses in the Exhaust Port of an Internal Combustion Engine

Författare: Wang, Y. W., Semlitsch, B., Mihaescu, M, Fuchs, L.F.
Dokumenttyp: Konferens
Tillstånd: Publicerad
Tidskrift: ASME 2013 International Mechanical Engineering Congress
Volym: IMECE2013-64610   8
År: 2013


A numerical study of the flow in the exhaust port geometryof a Scania heavy-duty Diesel engine is carried out mainly byusing the Large Eddy Simulation (LES) approach. UnsteadyReynolds Averaged Navier-Stokes (URANS) simulation resultsare included for comparison purposes. The calculations areperformed with fixed valve and stationary boundary conditionsfor which experimental data are available. The simulationsinclude a verification study of the solver using different gridresolutions and different valve lift states. The calculatednumerical data are compared to existent measured pressureloss data. The results show that even global parameters liketotal pressure losses are predicted better by LES than byURANS. The complex three-dimensional flow structuresgenerated in the flow field are qualitatively assessed throughvisualization and analyzed by statistical means.The near valve region is a major source of losses. Due tothe presence of the valve, an annular, jet-like flow structure isformed where the high-velocity flow follows the valve stem intothe port. Flow separation occurs immediately downstream ofthe valve seat on the walls of the port and also on the surface ofthe valve body. Strong longitudinal, non-stationary secondaryflow structures (i.e. in the plane normal to the main flowdirection) are observed in the exhaust manifold. Suchstructures can degrade the efficiency of a possible turbine of aturbocharger located downstream on the exhaust manifold.