SC²S Colloquium - November, 6, 2008
|Time:||3 pm, s.t.|
15:00 Uhr - Piyush Gupta: Frequency Response of Tubes due to Pressure Pulsations (MA, BMW)
Tubes used for transporting high velocity compressible exhaust gases in exhaust manifold often operate in time varying conditions due to engine operations. A lot of different frequencies of flows lead to vibration problems in tubes. These frequencies in flows are due to Nature of flow, turbulence and outlet boundary conditions (e.g. turbocharger at outlet). Pressure acting in wall of tube transferred to structure in frequency domain for frequency response analysis to calculate displacement and stress. Amplitude and phase angle of these frequencies varies with engine speed. A 3d CFD analysis done at different engine speed provides this data, but is too expensive to be used during engine development process. Another possibility is 1d CFD analysis, at different engine speeds to generate this data. 1d CFD is relatively cheap, but don’t consider 3d effects e.g 3d tube geometry, turbulence models etc.
In the present work Amplitude and phase angle function which varies with engine speed are compared for 1d CFD and 3d CFD. Frequency response of the tubes is also compared. On the basis of analysis, a new method of addressing vibration problems of tubes of exhaust manifold is also suggested. This method is simple to be used in engine development process in BMW, with limited numbers of data.