PREDICTIVE TOOLS INTEGRATION TOWARDS MEETING EXHAUST SYSTEM DESIGN CHALLENGES IN COMPACT HIGH POWER DENSITY VEHICLES

摘要

The increasing demand for high performance recreational vehicles combined with more stringent noise regulations and customer expectations lead to intake and exhaust systems design challenges, namely increased mass flow rate, reduced pressure losses and reduced space available for silencing devices along with shortened development cycles. Design choices must be made carefully to reach the performance targets while having the desired attenuation on harmonic noise related to combustion cycles without inducing excessive pressure losses and flow noise levels. Usage of predictive tools in conjunction with validation testing is becoming paramount to guide the design of such high-performance exhaust silencing devices. A discussion regarding the available simulation methodologies is presented with the associated pros and cons. All these approaches are widespread and well documented on four-stroke automotive engines, but additional challenges arise with high performance two-stroke engines, such as non-linear behavior of perforations due to grazing flow and high acoustic amplitude in addition to extended frequency range of noise predictions. Despite these new challenges, usage of simulation tools in product development allowed to identify the root cause of a problematic resonance in an exhaust silencer and to define 2 different strategies to mitigate it. One of the two design alternatives was finally selected and successfully implemented in a mass production consumer product.