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    Double Compression Expansion Engine: Evaluation of Thermodynamic Cycle and Combustion Concepts

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    PhD_Thesis_-_Vijai_Shankar_Bhavani_Shankar.docx (1).pdf
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    11.27Mb
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    Description:
    Thesis - Vijai Shankar
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    Type
    Dissertation
    Authors
    Shankar, Vijai cc
    Advisors
    Johansson, Bengt cc
    Committee members
    Sarathy, Mani cc
    Mishra, Himanshu cc
    Turner, Jamie
    Program
    Mechanical Engineering
    KAUST Department
    Physical Science and Engineering (PSE) Division
    Date
    2019-11
    Permanent link to this record
    http://hdl.handle.net/10754/660294
    
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    Abstract
    The efficiency of an internal combustion (IC) engine is governed by the thermodynamic cycle underpinning its operation. The thermodynamic efficiency of these devices is primarily determined by the temperature gradient created during the compression process. The final conversion efficiency also known as brake thermal efficiency (BTE) of IC engines, however, also depend on other processes associated with its operation. BTE is a product of the combustion, thermodynamic, gas-exchange, and mechanical efficiencies. The improvement of BTE through maximation of any one of the four efficiencies is reduced by its implication of the other three. Split-cycle engine provides an alternative method of improving the engine efficiency through over-expansion of combustion gases by transferring it to a cylinder of greater volume. The operation of split-cycle engines is based on either the Brayton or the Atkinson Cycles. Atkinson Cycle has been demonstrated in IC engines without the split-cycle architecture but is limited by the reduced energy density. Double Compression Expansion Engine (DCEE) provides a method of accomplishing the Atkinson Cycle without the constraints faced in conventional engine architectures. DCEE splits the compression and expansion processes in a vertical manner that enables the use of larger cylinder volumes for over-expansion as well as first-stage compression without much friction penalties. The present thesis explores the thermodynamic cycle of this novel engine architecture using well-validated 1-dimensional engine models solving for gas-exchange, real gas properties, and heat transfer provided in the GT-Power software tool. The effect of compression ratio, rate of heat addition, sensitivity to design and modeling parameters was assessed and contrasted against conventional engine architecture. The synergies of combining low-temperature combustion (LTC) concepts with DCEE was investigated using simulation and experimental data. DCEE relaxes many constraints placed the operation of an engine in Homogenous Charge Compression Ignition (HCCI) mode. The limitations of adopting Partially Premixed Combustion (PPC) concept is also alleviated by the DCEE concept. BTE improvement of above 10% points is achievable through the DCEE concept along with possibility to achieve very low emissions through use of LTC concepts and new after-treatment methods uniquely available to the DCEE.
    Citation
    Shankar, V. (2019). Double Compression Expansion Engine: Evaluation of Thermodynamic Cycle and Combustion Concepts. KAUST Research Repository. https://doi.org/10.25781/KAUST-5L3Q1
    DOI
    10.25781/KAUST-5L3Q1
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-5L3Q1
    Scopus Count
    Collections
    Dissertations; Physical Science and Engineering (PSE) Division; Mechanical Engineering Program

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