Acoustic optimization of a Muffler through the Sherpa algorithm 2019-01-0844
Regulations on noise and gas emissions are more and more stringent and as such, noise abatement devices need further engineering and optimization. In this sense, mufflers are installed at the end of powertrains to reduce the acoustic impact of the sound pressure from the engine. Such acoustic abatement is achieved through internal structures that promote destructive interferences within the muffler. In addition, the muffler increase the backpressure downstream the aftertreatment line, thus decreasing the engine efficiency.
In the following work, an optimization workflow is presented to find the best design for a muffler geometry. The optimization is performed with the Sherpa algorithm  that uses simultaneously several optimization algorithms to increase robustness and efficiency.
Sherpa is implemented in the optimization tool HEEDS that coordinates two other software. Siemens Simcenter 3D  calculates the acoustic transmission loss of the muffler, which is function of the geometrical characteristics of the muffler. Siemens Simcenter STAR-CCM+  models the 3D turbulent velocity and pressure fields to obtain an accurate prediction of the backpressure. The parametrized muffler CAD is changed at each optimization iteration. For each CAD, Simcenter 3D and STAR-CCM+ calculate the transmission loss and the backpressure respectively. HEEDS will intelligently look for the geometrical parameters that maximize the transmission loss and minimize the backpressure, converging towards the best design.
Carlo Locci, Edgar Matas, Karl Oberhumer
Siemens Software Industry GmbH, Siemens PLM Software