Mario Felice

Engine Cylinder Blocks and Heads NVH Improvements: Bolt Accelerations Computation Methodology

The need for engine system CAE radiated noise analysis to confirm results obtained from component - only analysis are expensive and time consuming. This is because engine system analysis requires finite element modeling of most engine components (large modeling time) and extensive CPU time and cost to run the full FE system model. The objective of this paper is to introduce a new CAE methodology that makes use of component - only analysis to predict the NVH systems effect of the engine block and head, without the need of analyzing the full engine system model. This new CAE methodology evaluates the bolted joint accelerations at the engine block and head flange connections to the: front cover; cam covers; oil pan; intake; exhausts; and transmission. This new method is called BAG (Bolt Accelerations Computation). BAG, in conjunction with SVL (Surface Velocity Level) acoustic response, has been used to optimize the Ford 5.4L cylinder block and cylinder heads for NVH. BAG results have shown excellent correlation to data from CAE engine system analysis and experimental engine testing. Any NVH improvements obtained from the engine block or cylinder head should not only focus on its acoustic response, but also and more importantly on the excitation transmitted to its attached components. Bolt Accelerations Computation improves the capability to analytically evaluate engine components (blocks and heads) as a system with respect to radiated noise without performing a full engine system analysis. Recommendations for the best design should be based on SVL and BAC analyses.