Optimizing the shape of space-constrained silencers composed of multiple straight/reverse chambers using the simulated annealing method

Abstract

To address the issue of hearing health problems caused by the broadband noise emitted from space-constrained marine diesel engines on a ship, an efficient silencer equipped at the engine's venting outlet is necessary. In consideration of the space-constrained situation that often occurs in ships, a reverse silencer with multiple chambers is introduced. A mathematical model of eigenfunction is adopted to consider the acoustic effect in high frequencies. An optimization of the silencer will be performed using the acoustic model of an eigenfunction together with the Simulated Annealing (SA) method under space-constrained conditions to achieve the best design. To pursue an efficient silencer design, two types of reverse silencers (Silencers A and B) are adopted to reduce the engine's venting noise. Acoustical models for straight chamber and reverse chamber silencers are checked before optimization. To assure the reliability of the SA scheme, a pure tone optimization at 250 Hz is exemplified. Results in silencers A and B show that the Sound Transmission Loss is approximately maximized at the desired frequency. Thereafter, a broadband noise elimination of engine noise using silencers A and B is performed. Simulated results show that overall noise abatement can be improved when the number of inverse chambers increases. The optimization of space-constrained reverse silencers with multiple chambers using eigenfunction in cooperation with Simulated Annealing (SA) has been accomplished. The overall silencer system's four-pole matrix is used to predict the silencer's acoustical performance of STL, which is achieved by multiplying individual four-pole matrices. With the introduction of the reverse silencer, the hearing health of workers can be protected, and noise pollution can be reduced in industrial settings.