The burner may be divided into five main sections: (i) variable swirl generator, (ii) fuel nozzle, (iii) pilot flame system, (iv) diffuser section, (v) viewport and extended exhaust gas section. Detailed drawings and dimensions for all the components of the burner, including the fuel nozzle and the swirl generator, may be found in here.
The total length of the assembly shown in Figure above is about 1.2 m and the largest cylindrical inner diameter is only 221 mm. The small physical scale of the burner is governed by the total energy throughput of the system. The nozzle is placed within the vertical set-up so that the fuel spray points downward and the bulk flow is from top to bottom. A horizontal burner configuration has been previously employed in a similar study [34], but was not chosen in this case because of the effects that buoyancy could have on flame symmetry. A vertical burner with the spray pointing upwards is also a common geometry for small scale systems , but was discarded because of the potential for large PM to fall back toward the air intake system, especially during poor burning conditions. The air box and swirl generator are constructed from aluminum and mild carbon steel since they are only exposed to air. All other burner sections downstream of the nozzle are constructed from 316 stainless steel to avoid any potential corrosion problems due to the acidic nature of the fuel. The combustion chamber walls are 3.2 mm thick and have no refractory lining. The various sections have flanged connections in order to make the assembly completely modular. Sealing between flanges in the swirl generator is provided with silicone rubber gaskets (rated to 260C). Other sections near or downstream of the flame and exposed to higher temperatures are sealed with compressible graphite gaskets (rated to 450C). Important design aspects regarding the burner assembly and its various sections are discussed below.