Ozone-Assisted Combustion—Part I: Literature Review and Kinetic Study Using Detailed n-Heptane Kinetic Mechanism

Abstract

In this first paper, the authors undertake a review of the literature in the field of ozone-assisted combustion in order to summarize literature findings. The use of a detailed n-heptane combustion model including ozone kinetics helps analyze these earlier results and leads into experimentation within the authors' laboratory using a single-cylinder, direct-injection compression ignition engine, briefly discussed here and in more depth in a following paper. The literature and kinetic modeling outcomes indicate that the addition of ozone leads to a decrease in ignition delay, both in comparison to no added ozone and with a decreasing equivalence ratio. This ignition delay decrease as the mixture leans is counter to the traditional increase in ignition delay with decreasing equivalence ratio. Moreover, the inclusion of ozone results in slightly higher temperatures in the cylinder due to ozone decomposition, augmented production of nitrogen oxides, and reduction in particulate matter through radial atomic oxygen chemistry. Of additional importance, acetylene levels decrease but carbon monoxide emissions are found to both increase and decrease as a function of equivalence ratio. This work illustrates that, beyond a certain level of assistance (approximately 20 ppm for the compression ratio of the authors' engine), adding more ozone has a negligible influence on combustion and emissions. This occurs because the introduction of O3 into the intake causes a temperature-limited equilibrium set of reactions via the atomic oxygen radical produced.

Experimental and Numerical Evaluation of an HCCI Engine Fueled with Biogas for Power Generation under Sub-Atmospheric Conditions

“…This strategy requires less maintenance compared to charge heating, and demands less energy to operate. Ozone addition tends to reduce the ignition delay as the mixture becomes leaner, as it promotes O radical formation, leading to a greater concentration of OH and H radicals [10]. Nishida and Tachibana [11] experimentally and numerically evaluated the effect of adding ozone to the charge of an HCCI engine fueled with natural gas, finding that an ozone concentration of 700 ppm could potentially lead to the same thermal efficiency with respect to diesel engine operation.…”

Numerical assessment of ozone addition potential in direct injection compression ignition engines

“…15 In general, all the studies showed that relatively low O 3 seeding in the intake flow (;100 ppm) can reduce significantly the ignition delay and the engine cyclic variations. 16 While experimental evidences of the potential of O 3 can be found in the literature, its applications are empirical and no proper optimization recommendation can be found. 3D computational models, in general employed for engine optimization, are still not capable to predict properly O 3 effect due to the lack of validation data as well as the complexity of the chemistry related to O 3 .…”