Method and system for a boosted engine

Abstract

The invention relates to a method and a system for a boosted engine. Methods and systems are provided for coordinated control of a compound boosting system, including a first compressor staged upstream of a second compressor in an engine intake. In one example, a method may include operating the second, downstream compressor in steady-state to achieve an overall pressure ratio across the compoundboosting system while operating the first, upstream compressor transiently, based on an airflow shortfall at the downstream compressor. A timing and amount of electric assistance provided to transiently operate the first, upstream compressor may be adjusted dynamically as the pressure ratio across the second compressor changes.

Description

technical field [0001] The present description generally relates to methods and systems for boosted engine systems having staged boosting devices. Background technique [0002] Engines may be equipped with boosting devices, such as turbochargers or superchargers, to increase airflow into the combustion chambers. Turbochargers and superchargers use an intake compressor to compress the intake air entering the engine. A turbocharger includes a compressor mechanically driven by an exhaust turbine, while an electric supercharger includes a compressor electrically driven by a motor. In certain engine systems, one or more intake boost devices may be staged in series or parallel in what may be referred to as a compound boost configuration. For example, a fast auxiliary boost device (eg, an electric supercharger) may be utilized to increase the transient performance of a slower main boost device (eg, a turbocharger). In such configurations, the size of the turbocharger may be incr...

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Problems solved by technology

However, this can result in a slower boost response

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