A New Spiral Muffler: acoustical equivalent model and performances estimation

A new type of exhaust gas muffler is proposed which is characterized by a spiral shape. A theoretical investigation was carried out to determine the spiral muffler acoustical performances. A muffler electrical equivalent model (EEM) was introduced, insertion loss and transfer function could be found for each value of the muffler geometrical and acoustical parameter. By means of a measurement campaign, lead on a laboratory prototype, the equivalent electrical model was validated by proving that model results are very close to measured ones. The investigation shows that a smaller volume spiral muffler introduces the same insertion loss than a traditional one; furthermore the exhaust gas temperature inside the spiral muffler is more uniform and higher than in a traditional one; thus gases condensation is inhibited and corrosion risk is strongly decreased. The investigation will prosecute to estimate the gases velocity and temperature field inside the spiral muffler in order to improve and optimize its acoustical and fluid-dynamic performances.