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Kavuri, Chaitanya
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Methodology to Perform Conjugate Heat Transfer Modeling for a Piston on a Sector Geometry for Direct-Injection Internal Combustion Engine Applications

Caterpillar Inc.-Chaitanya Kavuri, Jonathan Anders
Published 2019-04-02 by SAE International in United States
The increase in computational power in recent times has led to multidimensional computational fluid dynamics (CFD) modeling tools being used extensively for optimizing the diesel engine piston design. However, it is still common practice in engine CFD modeling to use constant uniform boundary temperatures. This is either due to the difficulty in experimentally measuring the component temperatures or the lack of measurements when simulation is being used predictively. This assumption introduces uncertainty in heat flux predictions. Conjugate heat transfer (CHT) modeling is an approach used to predict the component temperatures by simultaneously modeling the heat transfer in the fluid and the solid phase. However, CHT simulations are computationally expensive as they require more than one engine cycle to be simulated to converge to a steady cycle-averaged component temperature. Furthermore, a piston design optimization study would involve large numbers of simulations and including CHT modeling would be impractical considering the computational expense. Accordingly, in the current publication, an approach to perform piston CHT simulations on sector geometries is proposed to reduce the computational time significantly with…
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Investigating Air Handling Requirements of High Load Low Speed Reactivity Controlled Compression Ignition (RCCI) Combustion

University of Wisconsin-Madison-Chaitanya Kavuri, Sage Kokjohn
Published 2016-04-05 by SAE International in United States
Past research has shown that reactivity controlled compression ignition (RCCI) combustion offers efficiency and NOx and soot advantages over conventional diesel combustion at mid load conditions. However, at high load and low speed conditions, the chemistry timescale of the fuel shortens and the engine timescale lengthens. This mismatch in timescales makes operation at high load and low speed conditions difficult. High levels of exhaust gas recirculation (EGR) can be used to extend the chemistry timescales; however, this comes at the penalty of increased pumping losses. In the present study, targeting the high load - low speed regime, computational optimizations of RCCI combustion were performed at 20 bar gross indicated mean effective pressure (IMEP) and 1300 rev/min. The two fuels used for the study were gasoline (low reactivity) and diesel (high reactivity). The effects of intake pressure and EGR on combustion and emissions were studied using a full factorial design of experiments of genetic algorithm optimizations. The optimizations were setup for three values of EGR (30%, 45% and 55%) and equivalence ratios (0.8, 0.9 and 1.0).…
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