NVH Integration of Twin Charger Direct Injected Gasoline Engine

Abstract

The refinement of powertrain induced noise and vibration is one of the most important tasks during the vehicle development process. It strongly influences the driving perception of the vehicle together with attributes like drivability and vehicle dynamics. The expectation on NVH refinement from the customer point of view is also continuously increasing, especially in the premium and luxury segments. The task of NVH refinement gets even more challenging when new powertrain technologies like downsizing and down-speeding are introduced to meet both market expectations and legal regulation on CO 2 emission reduction. In combination with shorter product development time, due to that the automotive OEMs have to put products faster to the market and which is driven by competition, the reduction of both hardware stages and number of builds in a given hardware stage leads to that NVH refinement becomes even more complex. To minimize the risk of failure, advanced or research projects need to be executed up front of the ordinary product development projects in order to address all new concepts and technologies. The created new knowledge due to these "front-loading" activities may result in new specifications and requirements with associated assessment methods. All of this needs to be used in the later product development projects in terms of benchmarking, specification of technical requirements including system and component requirement down-cascading, concept evaluation, selection and optimization using virtual and hardware methods and finally validation. To be able to close the loop, the feedback from the learnings during the development projects is transferred back into the specifications, standards and methods.In the newly developed VEA engine family at Volvo Car Group a twin charger boosting system, i.e. a combination of a belt driven roots type supercharger and a turbo charger, is used for the top performance petrol engine to meet requirements on power and torque as well as fuel efficiency [1,2]. The supercharger provides boosting in the low engine speed range while a single large turbocharger, which is needed to meet peak power and torque requirements, operates from mid to top end engine speeds. The concept of a belt driven supercharger has significant advantages in response time at lower engine speeds compared to a single large turbocharger as the transient response time, or turbo lag, depends on the exhaust gas projection into the turbine geometry and polar inertia of the turbocharger [3]. The supercharger is controlled by an electromagnetic clutch, which enables disengagement and hence improves the fuel economy at steady state driving conditions as well as at the mid to top speed ranges where the NVH Integration of Twin Charger Direct Injected Gasoline EngineAshish Shah, David Lennström, Per-Olof Sturesson, and William Easterling Volvo Car Group ABSTRACTThe increased focus and demands on the reduction of fuel consumption and CO 2 requires the automotive industry to develop and introduce new and more energy effici...

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“…Compared to a mechanically driven supercharger, turbochargers tend to be more efficient, but less responsive. A twin-charger refers to an engine with a supercharger and a turbocharger [21].…”