Intake and Exhaust System Orifice Noise Optimization of a Single Cylinder Engine Using 1D Simulation Approach

Reducing vehicular noise has become a crucial step in product development to meet stringent legislation and improve passenger experience. Smaller vehicles like three-wheelers and quadricycle are often powered by a single cylinder engine due to product cost, packaging and weight constraints. Unlike a multi-cylinder engine where cylinders fire one after another which helps to reduce noise levels by destructive interference of pressure waves, a single cylinder engine produces higher noise levels due to firing of only a single cylinder. Intake and exhaust flow noise is one of the dominant sources of vehicular noise. Testing performed on an actual vehicle demonstrates reduction in cabin noise levels by reducing intake and exhaust flow noise. This study focuses on using CAE tools to reduce intake and exhaust flow noise levels to meet target noise requirements. One dimensional (1-D) gas dynamics simulation provides a good balance between simulation fidelity and run-time, allowing for evaluation of multiple design iterations with acceptable accuracy in a relatively small time frame. In this study, a system level optimization is performed on the intake and exhaust flow path requiring a larger number of design of experiments (DoE) to be performed, thus making 1D simulation the preferred approach for this study. For this study a compact car engine which was unable to meet the target noise levels was selected. A 1-D gas dynamics model was built and calibrated using existing test data. The calibrated model was further used for intake system optimization by running DoEs to evaluate the optimal air-filter and resonator parameters. Further optimization was performed on the exhaust system to determine the optimal muffler configuration. Multiple muffler designs were evaluated to optimize parameters such as pre and post muffler duct layout, muffler volume, baffle location, perforations and noise absorptive material placement. With the optimized intake and exhaust noise reduction recommendations about 2dB noise reduction was achieved on the exhaust side and about 3dB noise reduction was achieved on the intake side while meeting other performance targets.