AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
A Novel Miniature Inverted Burner for the Steady Generation of Soot Particles
MOHSEN KAZEMIMANESH, Kerry Chen, Jordan Titosky, Jason S. Olfert, University of Alberta
Abstract Number: 719 Working Group: Instrumentation and Methods
Abstract A miniature inverted burner was designed and its emitted soot nanoparticles were studied. The burner consisted of two co-annular tubes for fuel and co-flow air with internal diameters of 5.54 and 30 mm, respectively. The fuel of choice was ethylene due to its high sooting tendency. The generated flame was an inverted diffusion flame, enclosed in a quartz tube. Part of the co-flow air near the flame was used for the combustion of the fuel while the rest of the co-flow air in the vicinity of the quartz tube diluted the combustion products downstream of the flame, without the need for a secondary dilution. Three different sizes for the fuel tube (1.75, 3.35, and 5.54 mm in diameter) and the co-flow air tube (16, 24, and 30 mm in diameter) were tested to investigate the effect of geometry on flame stability and emission of soot particles. Different fuel and air flow rates were also tested to study the characteristics of the soot emissions from the burner. A scanning mobility particle sizer (SMPS) was used to determine the soot particle size distribution in each case. The effect of adding nitrogen to the fuel flow on the particle emissions was also studied for various fuel to nitrogen ratios. Moreover, the morphology of the emitted soot particles was studied using a transmission electron microscopy (TEM).
Results showed that only the large co-flow air tube could generate a flame with a dynamic range of soot particle concentration. The flame had a closed tip with low particle concentration for lower fuel flow rates, while it was open tip with high particle concentration beyond a certain threshold for the fuel flow rate. Small and medium sized co-flow tubes resulted in a closed tip flame due to overventilation. Moreover, the results showed that for the large co-flow geometry, the size distribution of soot particles did not change much with variation in co-flow air flow rate and, therefore, the co-flow air flow rate was held constant at 10 SLPM (standard litres per minute at 25°C and 101.325 kPa); however, the particle size distributions were strongly dependent on the fuel flow rate. Concentration and count median mobility diameter of soot particles changed significantly with slight changes in fuel flow rate until it reached a saturation state and the size of particles did not change noticeably. For fuel flow rates of 0.087, 0.096, 0.113, and 0.130 SLPM, the total concentration of soot particles was 2.35×105, 1.37×106, 1.91×107, and 3.66×107 cm-3, respectively. For the same fuel flow conditions, the count median diameter of soot particles was 85, 140, 166, and 168 nm, respectively. The addition of nitrogen to the fuel flow caused a gradual decrease in both particle mobility diameter as well as particle concentration as the nitrogen to fuel ratio increased up to 50%. Repeatability tests suggested that the miniature inverted burner could be used in applications such as a portable source of soot nanoparticles with great reproducibility of particle size and concentration.