Abstract
Adiabatic laminar burning velocities for methane, n-heptane, and iso-octane blended with ammonia were experimentally determined using the heat flux method. The flames were stabilized at atmospheric pressure and at an initial temperature of 338 K, over equivalence ratios ranging from 0.7 to 1.4 and ammonia blending fractions in the binary fuel mixtures from 0 to 90%. These experiments are essential for the development, validation, and optimization of chemical kinetic models, e.g., for the combustion of gasoline-ammonia fuel mixtures. It was observed that the addition of ammonia to methane, n-heptane, and iso-octane leads to a decrease in the laminar burning velocity that is not proportional to the ammonia mole fraction. In addition, ammonia has the same impact on the burning velocities of n-heptane and iso-octane but a slightly higher effect on those of methane. Such a burning velocity reduction is due to synergistic thermal, kinetic, and indirect transport effects. New experimental results were compared to predictions of the POLIMI detailed chemical kinetic mechanism. An overall good agreement between the measurements and simulated results was observed for the laminar burning velocities over the equivalence ratio and ammonia fraction ranges investigated. (Less)
Highlights
Renewable energy is playing an increasingly important role in addressing the key challenges that the contemporary energy society is facing, such as continuously fluctuating oil prices, energy insecurity associated with finite fossil fuel reserves, and climate change as a result of carbon dioxide emissions from fossil fuel combustion
An extensive experimental database of laminar burning velocities has been obtained at atmospheric pressure, over equivalence ratios ranging from 0.7 to 1.4, NH3 blending fractions in the binary mixtures from 0 to 90%, and unburned gas temperatures of 298 and 338 K, using the heat flux method
More than 110 new data points are presented that significantly enrich the literature database, especially considering that no data are available for n-heptane and iso-octane/NH3 blends. These results are believed to be valuable for validation of semiempirical mixing rules and detailed kinetic models and to identify optimal strategies for the enhancement of NH3 combustion in practical combustion devices
Summary
Renewable energy is playing an increasingly important role in addressing the key challenges that the contemporary energy society is facing, such as continuously fluctuating oil prices, energy insecurity associated with finite fossil fuel reserves, and climate change as a result of carbon dioxide emissions from fossil fuel combustion. Chemical energy storage (power-to-fuel) has been proposed as the most flexible and effective strategy for storing large quantities of excess electrical energy over the long term.[1] Power-to-fuel storage can be exerted at any location via carbon-neutral production of energy-dense gaseous or liquid hydrogen carriers (so-called e-fuels). Among the many kinds of options, ammonia (NH3) has been identified as a promising carbon-free e-fuel because it can be potentially synthesized on-site from surplus renewable electricity, water, and air, similar to hydrogen. It can be ideally burned, forming only water and nitrogen as combustion products. Because NH3 is an important chemical used in industrial and agricultural applications, well-established infrastructures and documented procedures for its safe storage, handling, and transportation are already available worldwide.[2−4]
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