Boundary element analysis of packed silencers with protective cloth and embedded thin surfaces

Enhancing micro-perforated panel attenuation by partitioning the adjoining cavity

“…Maa [15] found that a MSA is virtually identical to an MPP except that an MSA has slightly smaller resistance and larger reactance. Rather than predicting the impedance using Maa's theory, the transfer impedance was measured in an impedance tube using a similar technique to the two-cavity method proposed by Wu et al [16]. The measured transfer impedance is shown in Fig.…”

“…The MPP itself was modeled via a transfer impedance relationship. The transfer impedance (z tr ) [16] can be written as…”

Boundary Element Analysis of Reactive Mufflers and Packed Silencers with Catalyst Converters

“…On an IPC interface, * ξ is the sum of ξ and the dimensionless transfer impedance of the protective cloth [16].…”

“…It is impractical to define so many subdomains and try to match the boundary conditions at all interfaces. To overcome the modeling difficulty, Wu and his coworkers [15,16] have recently extended the direct mixed-body BEM to packed silencers. The idea is similar to the technique used for reactive mufflers.…”

“…The IP surfaces are the perforated interfaces between the bulkreacting material and air. The IPC interfaces are the same as the IP interfaces except that a layer of protective cloth is inserted between the perforated plate and the bulkreacting material to protect the bulk-reacting material from being blown out [16]. The ATB surfaces represent any rigid thin plates between the bulk-reacting material and air.…”