The Effect of Inlet Turbulence Intensity on Nano-Particulate Soot Formation in Kerosene-Fueled Combustors

In this work, we numerically study the effects of turbulence intensity at the fuel and oxidizer stream inlets on the soot aerosol nano-particles formation in a kerosene fuel-based combustor. In this regard, we study the turbulence intensity effects specifically on the thermal performance and nano-particulate soot aerosol emissions. To construct our computer model, we simulate the soot formation and oxidation using the Polycyclic Aromatic Hydrocarbons PAHs-inception and the hydroxyl concept, respectively. Additionally, the soot nucleation process is described using the phenyl route, in which the soot inception is described based on the formations of two-ringed and three-ringed aromatics from acetylene, benzene, and phenyl radical. We use the two-equation soot model in which the soot mass fraction and the soot number density transport equations are solved considering the evolutionary process of soot nanoparticles, where all the nucleation, coagulation, surface growth, and oxidation phenomena are suitable considered in calculations. For the combustion modeling part, we benefit from the flamelets library, i.e., a lookup table, considering a detailed chemical kinetic mechanism consisting of 121 species and 2613 elementary reactions and solve the transport equations for the mean mixture fraction and its variance. We take into account the turbulence-chemistry interaction using the presumed-shape probability density functions PDFs. We apply the two-equation high-Reynolds-number k-ε turbulence model with round-jet corrections and suitable wall functions in performing our turbulence modeling. Solving the transport equations of turbulence kinetic energy and its dissipation rate, the turbulence closure problem can be resolved suitably. Furthermore, we take into account the radiation heat transfer of soot and gases assuming optically-thin flame, in which the radiation heat transfer of the most important radiating species is determined locally through the emissions. To evaluate our numerical solutions, we first solve an available well-documented experimental test, which provides the details of a kerosene-fueled turbulent nonpremixed flame. Then, we compare the achieved flame structure, i.e., the distributions of mean mixture fraction, temperature, and soot volume fraction, with those measured in the experiment. Next, we change the turbulence intensities of the incoming fuel and oxidizer streams gradually. So, we become able to evaluate the effects of different turbulence intensities on the achieved temperature and soot aerosol concentrations. Our results show that using moderate turbulence intensities at both fuel and oxidizer stream inlets would effectively increase the maximum temperature inside the combustor and this would reduce the exhaust gases temperature. It also reduces the concentrations of soot in the combustor and its emission to the exhaust gases effectively.