Autoigntion and flame speed of premixed liquefied petroleum gas in a rapid compression machine: experimental results and reduced chemical kinetic mechanism
Date
2023
Authors
Slunecka, Colin, author
Olsen, Daniel, advisor
Marchese, Anthony, advisor
Windom, Bret, committee member
von Fischer, Joe, committee member
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Abstract
Liquefied petroleum gas (LPG) has many properties that make it an attractive alternative fuel such as lower cost than conventional fuels and an established distribution infrastructure. The development of high efficiency, spark ignited LPG engines is currently limited by engine knock and misfire. The knock and misfire limits are further complicated by the wide range of chemical reactivity in LPG, particularly in international markets. In this study, a rapid compression machine (RCM) was used to characterize the effects of variation in LPG fuel reactivity, equivalence ratio, and exhaust gas recirculation (EGR) on the autoignition and flame speeds of LPG/oxidizer/inert/EGR blends. Experiments were conducted with 100% propane and blends of propane with propene, ethane, isobutane, or n-butane. EGR was simulated with mixtures of Ar, CO2, CO, and NO at substitution percentages from 0 to 30 mass percent. Equivalence ratio was varied from 0.75 to 1.5. Ignition delay period under homogeneous autoignition conditions was measured at compressed pressures and temperatures of 23 to 25 bar and 701 to 921 K, respectively. Laminar flame speeds and apparent heat release rates (AHRR) at 24 bar with mixture temperatures of 700 K or 867 K were obtained by firing a laser ignition system into the reaction chamber shortly after compression and analyzing the propagating flame with high speed schlieren imaging. Zero-dimensional simulations of published autoignition experiments were performed using Chemkin-Pro with several detailed chemical kinetic mechanisms to determine their suitability at predicting ignition delay periods. Multiple reduced chemical kinetic mechanisms were created from the NUIGMech1.1 mechanism to determine the optimal balance between accuracy and computational efficiency for future three-dimensional, time-dependent spark-ignited engine simulations. The chosen reduction, ALPINE 153, was used to model ignition delay periods and flame speeds measured in the RCM during this study.
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Subject
ignition delay
mechanism reduction
combustion
rapid compression machine
LPG