NVH Integration of Twin Charger Direct Injected Gasoline Engine

The increased focus and demands on the reduction of fuel consumption and CO₂ requires the automotive industry to develop and introduce new and more energy efficient powertrain concepts. The extensive utilisation of downsizing concepts, such as boosting, leads to significant challenges in noise, vibration and harshness (NVH) integration. This is in conflict with the market expectation on the vehicle's acoustic refinement, which plays an increasingly important role in terms of product perception, especially in the premium or luxury segment. The introduction of the twin charger boosting system, i.e. combining super and turbo charging devices, enables downsizing/speeding in order to achieve improved fuel economy as well as short time-to-torque, while maintaining high driving dynamics. This concept requires also extensive consideration to NVH integration. The NVH challenges when integrating a roots type supercharger are very extensive. The high frequency source characteristics of the supercharger result in complex wave propagation inside the intake duct system since exciting pulsation orders are well above duct cut-on frequencies. The source strength in relation to audible interior tonal noise threshold is also very high. In addition the background masking levels in terms of mainly combustion related powertrain and road noise are low with the consequence that the orders (tonal noise components) can be prominent and annoying even with a high degree of acoustic source treatment (remedies). The scope of this paper is to describe quantification of the charging system noise radiation and propagation including subsystem target cascading synthesis.