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SiC porous ceramics (SPCs) are key functional medium materials, which are widely applied as porous burners. However, SPCs produced via the polyurethane sponge replica technique usually exhibit a randomly distributed cellular structure, leading to vulnerability and a low combustion efficiency for the porous burners. In this study, SPCs were structurally designed via novel 3D printed resin template technique; this endowed the SPCs with synergistically optimized strength and combustion characteristics. SPCs containing tetrakaidecahedron, octahedron and cubic cells were successfully prepared via SiC slurry coating and sintering in air. The cell parameters determined the strength and combustion properties of the SPCs. The SPCs containing cubic cells exhibited the largest strength and strain, because more struts were present parallel to the loading direction; this is more advantageous for stress bearing compared to those vertical to the loading direction. The tetrakaidecahedron cell facilitated the formation of a disturbance effect within the SPCs to a higher extent than the cubic and octahedron cells, thereby enhancing the heat exchange performance between the fluid and porous framework. Hence, the SPC with tetrakaidecahedron cells exhibited the best combustion properties, which resulted in the highest surface temperature and lowest pollution emission. [ABSTRACT FROM AUTHOR]

The effect of fuel components and combustion parameters on the emission characteristics of aldehydes from biodiesel combustion is investigated, and the formation mechanism of aldehydes is revealed. The results show that CH 2 O and CH 3 CHO are the main aldehydes produced during biodiesel combustion. The rise in initial temperature and pressure reduces the formation of aldehydes, which accelerates the generation of reactive radicals to promote the oxidation of aldehydes. As the equivalence ratio decreases from 2.0 to 0.5, the concentrations of formaldehyde and acetaldehyde decrease from 444.58 to 438.19 μg/m3 to 164.72 and 6.71 μg/m3, respectively, due to the oxidation and dilution effect of air on aldehydes. In addition, when the number of C C bonds in biodiesel is increased from 0 to 1, the concentrations of formaldehyde and acetaldehyde are enhanced by 117.89 % and 12.74 %, respectively, because of the reduction in the content of reactive radical H. The main formation pathway of aldehydes is as follows: Biodiesel is initially consumed via H-abstraction reactions by reactive radicals (OH, H, etc.) to produce primary fuel radicals, which mainly undergo β-decomposition to form key oxidation intermediates (C 4 H 6 , C 2 H 4 , C 2 H 3 , etc.). Consequently, these small molecular intermediates will be converted to aldehydes by oxidation and dehydrogenation reactions. [ABSTRACT FROM AUTHOR]