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Time- and Space-resolved Heat Transfer Model for Spark-Ignition Engines

Mukherjee, Smarajit
http://orcid.org/0000-0002-0761-0464
http://rave.ohiolink.edu/etdc/view?acc_num=osu1517440404339384

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Mechanical Engineering.
In view of the ever-increasing consumption of non-renewable vehicular fuels, it is imperative to continually improve the efficiency of Spark-Ignition (SI) engines, which power majority of the light duty vehicles in the US. Increasing the compression ratio is a well-established approach for developing fuel-efficient SI engines. However, the potential benefits of this approach are limited by engine knock, which is driven by the temperature-dependent chemical kinetics of combustion. In combination with the energy released from combustion, in-cylinder heat transfer dictates the magnitude of in-cylinder gas temperatures, thus defining the efficiency and performance of an SI engine. One-dimensional (1D) simulation tools are extensively used in the automotive industry to predict engine performance. In-cylinder heat transfer is calculated within such codes using empirical correlations originally formulated to compute the heat transfer coefficient for turbulent flow within pipes. The turbulent flow field within the combustion chamber interacts with the propagating flame front (during combustion). Consequently, the resulting flow physics is significantly more involved compared to turbulent flow within pipes. Applying a pipe-flow based correlation to estimate in-cylinder heat transfer misrepresents the actual physics, resulting in unreliable heat transfer predictions. Hence, the objective of this work is to address this deficiency by developing a fundamental 1D engine heat transfer model, which is well-grounded in the governing flow physics. Instantaneous local heat flux measurements from an earlier study with a 2.0L 4V I4 production SI engine from Fiat Chrysler Automobiles (FCA) at multiple operating conditions were used here to develop a fundamental understanding of the evolution of local heat flux. Heat flux microsensors installed in Cylinder Head #4 provided measurements for heat flux and surface temperature at the sensor locations. Pressure transducers captured the instantaneous pressure within the plenum, combustion chamber and exhaust port of Cylinder #4. To investigate the distribution and evolution of heat flux over all the chamber surfaces, three-dimensional CFD simulations (with the CONVERGE CFD software) of the engine cycle within Cylinder #4 were performed. The in-cylinder pressure and heat flux predictions at the sensor locations were validated against measurements. The insight gained from CFD into the governing physics of in-cylinder heat transfer was utilized to construct a physics-based 1D heat transfer model within an engine simulation code (GT-Power). Instead of relying on pipe-flow physics, the new model calculates instantaneous thermal boundary layer thicknesses by solving the 1D energy equation, and applies Fourier’s law to compute the instantaneous heat fluxes at discrete wall locations. This allows the model to resolve the spatial variation in in-cylinder heat transfer: an important characteristic that cannot be captured by pipe-flow based correlations. The empirical elements of the model which demonstrate substantial impact on the local and mean heat flux predictions were calibrated using the corresponding CFD results. The model did not require any recalibration as the heat flux predicted at the sensor locations was found to be in good agreement with measurements for all operating conditions tested, indicating that empiricism involved in heat transfer calculations was significantly reduced by the realistic representation of the governing physics.
Ahmet Selamet, PhD (Advisor)
Junmin Wang, PhD (Committee Member)
Jen-Ping Chen, PhD (Committee Member)
208 p.
Automotive Engineering; Fluid Dynamics; Mechanical Engineering; Transportation

Recommended Citations

Citations

  • Mukherjee, S. (2018). Time- and Space-resolved Heat Transfer Model for Spark-Ignition Engines [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1517440404339384

    APA Style (7th edition)

  • Mukherjee, Smarajit. Time- and Space-resolved Heat Transfer Model for Spark-Ignition Engines. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1517440404339384.

    MLA Style (8th edition)

  • Mukherjee, Smarajit. "Time- and Space-resolved Heat Transfer Model for Spark-Ignition Engines." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1517440404339384

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.