Research Fellow, The University of Western Australia
Enthusiastic and self-motivated early career researcher with a proven track record in renewable energy, biofuels, combustion science and technology, fuel processing and conversion and reaction engineering
Abstract: The ignition and combustion characteristics of Zhundong lignite (ZDL), with and without washing to remove different forms of inherent sodium, were investigated. Water washed (ZDL-WW) and acid washed (ZDL-AW) samples were prepared by soaking the raw lignite (ZDL-Raw) in ultrapure water and 0.5 M hydrochloric acid (HCl), respectively, at 60 °C for 24 h. A single particle of a ZDL sample, ca 2.5 mm in diameter, was suspended on a silicon carbide fibre (142 µm) tip and burned in air at 1123 K in a furnace. The time-resolved ignition and combustion behaviours of the single particles were observed with the aid of combined use of a shortwave infrared camera, a CCD camera, which enabled the determination of the ignition mechanism, ignition time, burnout time and burning rate. A flame emission spectrometer was used to identify the presence of sodium in the flame. The ignition of all ZDL samples followed the joint hetero-homogeneous mechanism in the present work. Upon the homogeneous ignition, ZDL-Raw exhibited a soot free yellowish translucent flame while ZDL-WW and ZDL-AW showed sooty flames. The ignition time followed the order of ZDL-Raw>ZDL-WW>ZDL-AW while the burning rate followed the opposite order. These observations were attributed to the catalytic effect of sodium in the lignite whose amount was varied due to the water and acid washing. Sodium ions were detected in the flame of ZDL with and without washing and the intensity of sodium signal also followed the order of ZDL-Raw>ZDL-WW>ZDL-AW. It is believed that sodium ions released in the flame promoted catalytic cracking of large tar fragments and oxidation of soot precursors.
Pub.: 30 Sep '16, Pinned: 27 Jul '17
Abstract: A kinetic modeling study of the effect of iron on the ignition and combustion characteristics of diesel, modeled as n-heptane, in compression ignition engines was carried out using CHEMKIN PRO. The ignition was simulated using the SENKIN code, and combustion was modeled using the OPPDIF code. The kinetic models incorporated n-heptane mechanisms involving 159 species and 1540 reactions and iron reaction mechanisms of 7 iron species and 46 reactions. It was found that small amounts of iron in the fuel significantly reduced the ignition delay time. The ignition delay time decreased with an increasing iron concentration. A reaction pathway analysis showed that the ignition was promoted as a result of an early injection of the OH radicals. It was also showed that the addition of iron increased the peak flame temperature of n-heptane in the counter-flow diffusion flame and reduced the maximum mole fractions of H and O in the peak flame region as a result of the catalytic recombination cycles involving FeO, Fe(OH)2, and FeOH. The reaction rates of H + O2 ⇔ O + OH and CO + OH ⇔ CO2 + H in the peak flame region were found to increase, which is considered to be responsible for the increased peak flame temperature.
Pub.: 02 Dec '16, Pinned: 27 Jul '17
Abstract: The ignition and combustion behaviour of single droplets of biochar-glycerol-water slurry fuels was experimentally investigated. A pine sawdust biochar with a median particle size (D50) of approximately 12 µm was used. The slurry fuels with a constant biochar loading of 42wt% and glycerol/water ratios varying from 0 to 0.5 by weight were prepared. A single droplet of a slurry fuel with diameter ranging from 0.5 mm to 2.0 mm was suspended on a silicon carbide fibre and burned in air at 1023 K in an electrically heated tube furnace. The ignition and combustion processes of the droplets were recorded using a colour CCD camera. The ignition delay time, burnout time and burning rate based on the d2 law were determined. It was found that all the slurry fuels exhibited heterogeneous ignition of biochar residue (agglomerate) following water and glycerol evaporation. The addition of glycerol significantly reduced ignition delay time, shortened burnout time and increased burning rate of the droplets. This effect was enhanced with increasing glycerol/water ratio in the slurry fuels. It was also found that the glycerol was not completely evaporated before ignition and the remaining glycerol burned concurrently with the biochar on or near the agglomerate surface. The combustion of agglomerate after ignition was controlled by external oxygen diffusion to the outer layer of the agglomerate under the conditions tested.
Pub.: 25 Jul '16, Pinned: 27 Jul '17