Catalyst & DPF Acoustic Transmission Loss Benchmark Study

Paper #:
  • 2017-01-1798

  • 2017-06-05
The ability to predict exhaust system acoustics including transmission loss (TL) and tailpipe noise accurately based on CAD geometry has long been a requirement of most OEM’s and Tier 1 exhaust suppliers. Correlation to measurement data has been problematic under various operating conditions including flow. This study was undertaken to address and identify the critical dimensions and modeling sensitivities. Ford uses Ricardo WAVE as one of their 1-D NVH tools, which was chosen for the purpose of this benchmark study. The vibro-acoustics group at University of Kentucky Department of Mechanical Engineering (UKME) has extensive experience in using 3D and 1D acoustic modeling tools for exhaust components and in correlating the numerical predictions to measurements. The most commonly used metrics for evaluating the acoustical performance of mufflers are insertion loss (IL), transmission loss (TL), and noise reduction (NR). TL is often the first step of analysis since it represents the inherent capability of the muffler to attenuate sound if both the source and termination are assumed to be anechoic. It can also be reliably measured and numerically simulated without having to connect to an engine. For the purpose of software validation, TL benchmarking should be the first step. This study focused around two key exhaust components; Catalysts (CAT’s) and Diesel Particulate Filters (DPF’s), with TL measurements collected for validation purposes. These measurements were compared to simulation data to validate Ricardo WAVE models that directly reflected the test set up. Differences were identified and model sensitivities studies conducted resulting in revised modeling recommendations for CAT’s and DPF’s. This will help create more acoustically accurate CAT and DPF models before any hardware is available for validation.
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