Swirling coal flames are encountered in swirl burners of boiler furnaces and cyclone coal combustors, and were studied using large-eddy simulation (LES) in reported references. However, the structures of swirling coal flames remain to be further studied. In the present paper LES of swirling coal flames is conducted for two combustors using two gas combustion models. The statistical simulation results are accessed by experiments and the instantaneous simulation results are used to analyze the specific features of flame structures of four cases. It is seen that different inlet flow conditions and different secondary-air flow rate lead to different flame structures

Influence of core flow inlet swirl angle on aerodynamic performances of an exhaust nozzle with scarfed lobed mixer was studied by the validated computational approach. The computational simulation was conducted by resolving the steady form of discretized three-dimensional Reynolds Averaged Navier-Stokes equations with the shear stress transport k-Ω turbulence model. Simulation results depict that swirling motions have ignorable influence on the flow field of the top part in the cross sections slightly downstream of the lobed trailing edge. Besides, for the flow field downstream of the L/D=0.1 cross section, the swirling motions are suggested to cause the clockwise stream-wise vortex to stretch into several smaller-scale vortexes. When the case with a bigger swirling angle is investigated, the induced smaller-scale vortexes are more strengthened by the swirling motions. Concerning the 15° swirling case, the loss caused by the destroyed vortex pattern and the benefit induced by the improved smaller-scale vortexes almost counteract with each other with respect to the thermal mixing efficiency. In the last studied cross section as compared with the baseline case, the case with a maximum swirling angle of 30° has increased 6.94% for the thermal mixing efficiency and decreased 0.42% for the total pressure recovery coefficient.

The search for higher energy efficiency of industrial-scale burners to attain low emission especially Nitrogen Oxide (NOx) has demanded experimental studies that are complemented with Computational Fluid Dynamics (CFD) simulations. While there exist numerous emission control techniques, the passive control technique was the main focus of the present review study. Biodiesel fuel crude palm oil (CPO) was found to reduce emission components, particularly carbon components and particulate matter (PM). Biodiesel CPO has the capability to mitigate cavitation inside the injector’s orifice which contributes to damage reduction on the orifice. Moreover, although cavitation can improve spray atomization and produce finer spray droplets, it also causes damage to the orifice of injectors. Orifice characteristics such as orifice’s diameter and pattern can also reduce cavitation inside the orifice. Orifice’s pattern is divided into cylindrical shape orifice and conical shape orifice. The conical orifice is found to reduce the cavitation inside the orifice while cylindrical orifice was indicated as a highly cavitating orifice. Alternatively, as rapid swirling motion is capable to enhance the fuel and air mixing, a new concept of swirling fuel-air premix inside the injector is invented and it is proven to reduce emissions. It was, however, learned that spray characteristics are still playing an important role in the prediction of combustion performance, particularly droplets Sauter Mean Diameter (SMD) which is a worldwide parameter that needs further investigations in order to predict the fineness of spray production and combustion.