Numerische Untersuchung unterschiedlicher Mischeinrichtungen zur Minimierung der Stickoxidemission

During the development of burners, the main aim is to reduce the harmful emission. In this work, the numerical investigations of different kind of mixing apparatus were made to reduce the NOx-emission during the combustion of oil. The air-stages, fuel-distributions and the fuel-vaporization are described as the primarily measures to reduce the NOx-emission. According to the numerical results with CFX, the further measures can be used in different kind of concepts to reduce the NOX-emission. With the concept of air-stages, fuel-distributions and fuel-vaporization, the NOx-emission can be reduced. Each concept is based on different chemical mechanism. The aim of the concept of air-stages is to reduce the fuel-NOx-emission. So, it is very important, an under stochiometrical zone to produce. The aim of the concept of fuel-distributions is to produce a better distribution of fuel, so that one needs at least two fuel-supports from technical view in this concept. At the same time, one must take the stabilization of flame into consideration. These two kind of burners need a very expensive construction of mixing apparatus. The concept of air-stages is very suitable for the combustion of fuel, in which there is a high proportion of fuel-N. With the concept of fuel-vaporization, the fluid fuel can be at first vaporized and mixed with air. The recirculation of exhaust gas, because of the air impulse, can reduce the thermal-NOx-Emission. But it is necessary, one vaporization-tube to build, in order to let the fuel to be vaporized. That lets one big geometry of this burner. So, the burner according to the concept of fuel-vaporization is not very suitable for larger combustion power. In order to investigate the effects of geometry in air-stage-burners, the numerical simulations are made under different kind of angels of secondary air and tertiary air. The recirculation's rate is determined and compared each other. The calculated results are qualitative identical with the experimental results. The numerical simulations of the burner according to the fuel-distribution provide the behaviour of this burner under different power, which can be used to analyse and to understand the fluid-field of this burner. The calculated recirculation's rates in the burner of fuel-vaporization provide a lot of important information for the reduction of NOx-emission. Some results are identical with experimental results