Powertrain Radiated Noise Segregation for Internal Combustion Engines

Powertrain is the most prominent source of Noise and Vibration in the vehicle. Improvement in Powertrain Noise & Vibration is a multifaceted topic due to complex architecture of the powertrain and the critical role of calibration in defining combustion inputs. Hence, a method to clearly distinguish these aspects is required in order to address the exact problem and decide on course of actions to improve NVH performance of powertrains. This paper discusses a post-processing technique through which experimentally acquired ICE Powertrain Noise can be further segregated in order to identify and address the root source. The segregation methodology requires as input - noise, vibration and cylinder pressure values at various torque conditions across multiple operating points. A MATLAB based code developed by the authors is used to generate correlation between the Cylinder Pressure, Torque and Noise Parameters. The transfer coefficient at every frequency point is calculated using regression technique with all the sample data sets acquired. This helps in splitting the Powertrain Noise into Load Dependent Mechanical Noise, Load Independent Mechanical Nosie and Combustion Noise. This provides a structured way of approaching the root source of the Powertrain Noise. The transfer co-efficient curve of the Combustion Noise also known as the structural Attenuation Curve (SAC) gives an insight on the improvement required in the structure of the engine and its constituents. The paper also discusses the application of this methodology to a 1.5L, 4 Cylinder in-line diesel and a 1.5L, 4-Cylinder in-line petrol powertrain. The improvements through calibration and structural modifications are done in order to reduce respective contributions identified through application of aforementioned process. The derived results have helped to focus development efforts on direct source and hence optimize our development workflow.