F2008-12-109
Designing a V6 Diesel Engine to be NVH Best in Class: Contribution of Computational Analysis
There is higher and higher demand by customers for vehicles with the maximum level of comfort, leading to take the engine NVH behaviour into high consideration since the initial phases of a new engine development. It is a key factor to use both computational and experimental analysis in combination with a clear definition of all key steps in the NVH development: target setting and deployment, concept and design, combustion and mechanical development and the experimental tests. Even though the engine radiated noise level that can be achieved is largely dependent on the selected design concept, to run computational analysis in parallel with design studies during the engine program gives substantial advantages. Indeed, this allows sensitivity studies to be performed, leading to design changes aimed at low noise radiation, with the final aim that when the engine will be installed in the semi-anechoic chamber, the main components are already optimized from the NVH point of view. As a consequence, spending for costly NVH-driven casting modifications is avoided. Aim of this paper is to focus on the contribution of computational analysis to the achievement of stringent NVH targets. On one side several simulations have been performed to verify that the minimum powertrain bending natural frequency is met, as well as that accessories fundamental natural frequency is above the specific target. On the other side, forced response analysis have been run in order to optimize the main components, so that a lot of attention has been paid to the design of the engine block, the bedplate, the upper part of the oil pan, the engine timing cover and cylinder heads. Numerical results in terms of surface vibration levels due to forced excitation have been compared to scatter-band data available for similar diesel engines: this allowed to identify critical areas where additional stiffening was recommended to reduce radiated noise as well as those areas where a potential mass saving is applicable.
Session: NVH