On the Formation of Nitrogen Oxides During the Combustion of ...

1 Introduction
Combustion is a fundamental physico-chemical process and the basis of
modern human civilization [253]. Its overarching importance to elementary
human needs becomes apparent even when looking at mythology, in which
Prometheus stole fire from Zeus, chief of the Greek gods, and gave it to the
mortals in their dark caves. In today’s world, a substantial part of harnessed
fire comes from burning petroleum, 1 which was first extracted in Pennsylvania
for commercial purposes in 1859 [253, 274, 323].
1.1 Technological Background
Gas turbine, diesel, and rocket engines burn liquid fuels in spray flames, as do
oil-fired boilers, furnaces, and process heaters. After the liquid fuel is injected
into the combustion chamber using single or twin-fluid atomizers, the fuel
is atomized due to instabilities of the liquid and momentum exchange with
the gas phase. Droplets are created and partially vaporized before the radical
pool can be formed that finally leads to the chemical breakdown of the fuel
[241, 244, 418, 443, 457, 461].
Most modern, low emission combustion concepts are based on partial or full
premixing of fuel and oxidant, and pre-vaporization in the case of liquid fuels.
Premixed combustion takes place if the droplets are completely vaporized and
fuel and air molecules are mixed by molecular or turbulent diffusion before
ignition. With respect to exhaust gas formation, experimental and numerical
studies of this case are more easily carried out than in partially premixed combustion,
where complicated interactions of the diffusion of fuel vapor, air, and
combustion products prevail in the flame zone.
1 In the United States of America, 80 to 85% of primary energy consumption were covered by fossil fuels throughout
the last two decades (1990 to 2010) [450]. The Arbeitsgemeinschaft Energiebilanzen and the Statistisches
Bundesamt recorded an almost identical value for Germany. Here, petroleum was by far the most relevant
energy source with a portion of 33 to 40% of primary energy consumption [24, 421].
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