Abstract
This paper presents the numerical modeling of noise radiated by an engine based on the so-called Acoustic Transfer Vectors and Modal Acoustic Transfer Vectors concept. Special attention is given to the calculation of Acoustic Radiated Power using the ISO3744-1994 Norm and the setup of a vibro-acoustic optimization sequence for the engine design.
Acoustic Transfer Vectors are input-output relations between the normal structural velocity of the radiating surface and the sound pressure level at a specific field point and can thus be interpreted as an ensemble of Acoustic Transfer Functions from the surface nodes to a single field point or microphone position. The modal counterpart establishes the same acoustic transfer expressed in modal coordinates of the radiating structure.
The method is used to evaluate the noise radiated during an engine run-up in the frequency domain. The dynamics of the engine is described using a finite element model loaded with a rpm-dependent excitation.
Given the effectiveness of the vibro-acoustic method in terms of calculation speed, compared with classical boundary element methods, a fast optimization sequence is made possible and practical. The evaluation of the results, in function of rpm and frequency, shows the potential of the approach during the engine development process.