Performance Attributes for Root Cause Detection of Piston Induced Noise

Modern powertrain noise investigation in the development process and during trouble shooting is a combination of experiment and simulation. In simulation in recent years main focus was set on model completeness, consideration of all excitation mechanisms and efficient and stabile numerical algorithms. By that the total response of the virtual powertrain is already comparable to the overall noise level of the real powertrain. Actual challenge is to trace back the overall response to its main excitation and noise generating mechanism as well as to their main driving parameters to support the engineer not only in reaching absolute values, but also to derive the root cause of a response or potential problem and to get hints on how to improve the specific behavior. Approaches by parameter sensitivity studies are time consuming and not unambiguous. Target is to develop (performance) attributes, characterizing a specific NV phenomenon, which are extracted from a specific NV response result for a powerunit under operating conditions. The methodology should be applicable for simulation and measurement to allow direct comparison. By understanding the link between the attribute, its driving parameters and the response, the specific NV effect can be analyzed and optimized within its contribution to the overall response. This paper presents such an approach for the piston induced noise of a combustion engine. Methodology is presented for an I4 gasoline engine with different running clearances between piston and liner and two load conditions. Results from simulation are compared to those from experiment.