In order to improve the thermal efficiency of engines, it is essential to increase their geometric compression ratio or the expansion ratio. This research explores the technology options to enable a higher expansion ratio in future boosted spark-ignition direct-injection engines, with the aim of significantly reducing the fuel consumption while achieving the same torque and combustion performances as those of baseline turbocharged engines. Variable-valve-actuation technologies such as the late-intake-valve-closing cam strategy and the early-intake-valve-closing cam strategy were considered, and their effectiveness in reducing the effective compression and preventing knock in high-compression-ratio engines was assessed. To compensate for the torque loss due to late intake valve closing or early intake valve closing, multi-stage boosting systems including the turbocharger–supercharger combination and the two-stage turbocharger were implemented and compared. In this study, a Miller cycle engine concept with a high expansion ratio of 12.0:1 was developed with variable valve actuation and multi-stage boosting. On the basis of this new concept, an engine was built and extensively tested on an engine dynamometer to assess its part-load fuel consumption and full-load performance. The experimental results indicated that this engine concept can improve the fuel economy of the vehicle by 3–4% at typical city and highway driving conditions while maintaining the same performance.


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    Title :

    Research on and development of a Miller cycle engine with multi-stage boosting


    Contributors:
    He, Yongsheng (author) / Liu, Jim (author) / Zhu, Bin (author) / Sun, David (author)


    Publication date :

    2016-09-01


    Size :

    12 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English