For an automotive exhaust system, noise level and back pressure are the most
important parameters for passenger comfort and engine performance respectively.
The sound quality perception of the existing silencer design was unacceptable,
although the back pressure measured was below the target limit. To improve the
existing design, few concepts were prepared by changing the internal elements of
silencer only. The design constraints were the silencer shell dimensions, volume
of silencer, inlet pipe and outlet tailpipe positions, which had to be kept same
as that of the existing base design.
The sound quality signal replaying and synthesizing was performed to define the
desired sound quality. The numerical simulation involves 3D computational fluid
dynamics (CFD) with appropriate boundary condition having less
numerical diffusions to predict the back pressure. The various silencer concepts
developed with this preliminary analysis, was then experimentally verified with
the numerical data. Using this hybrid approach of experiment and simulation, an
optimum design of silencer internals has been developed for achieving acceptable
sound quality, overall noise levels and back pressure without affecting the
engine performance.