Numerical Investigation on the Effect of the Oxymethylene Ether-3 (OME3) Blending Ratio in Premixed Sooting Ethylene Flames

Synthetic fuels, especially oxygenated fuels, which can be used as blending components, make it possible to modify the emission properties of conventional fossil fuels. Among oxygenated fuels, one promising candidate is oxymethylene ether-3 (OME3). In this work, the sooting propensity of ethylene (C2H4) blended with OME3 is numerically investigated on a series of laminar burner-stabilized premixed flames with increasing amounts of OME3, from pure ethylene to pure OME3. The numerical analysis is performed using the Conditional Quadrature Method of Moments combined with a detailed physico-chemical soot model. Two different equivalence ratios corresponding to a lightly and a highly sooting flame condition have been investigated. The study examines how different blending ratios of the two fuels affect soot particle formation and a correlation between OME3 blending ratio and corresponding soot reduction is established. The soot precursor species in the gas-phase are analyzed along with the soot volume fraction of small nanoparticles and large aggregates. Furthermore, the influence of the OME3 blending on the particle size distribution is studied applying the entropy maximization concept. The effect of increasing amounts of OME3 is found to be different for soot nanoparticles and larger aggregates. While OME3 blending significantly reduces the amount of larger aggregates, only large amounts of OME3, close to pure OME3, lead to a considerable suppression of nanoparticles formed throughout the flame. A linear correlation is identified between the OME3 content in the fuel and the reduction in the soot volume fraction of larger aggregates, while smaller blending ratios may lead to an increased number of nanoparticles for some positions in the flame for the richer flame condition.

Comparative study on porous media combustion characteristics using different discrete materials

Occurrence of combustion phenomenon in porous media has always excited researchers to develop various shape and size of burner so that maximum utilization of energy can be taken achieved. Here in this experiential work, dual layer micro burner was exclusively built to carry out porous media combustion characteristic with different type of discrete material in reaction zone. Presently, only alumina and zirconia are compared in discrete form, while preheat layer was made of porcelain ceramic material (foam type). Reaction zone was restricted to thickness of 20mm while preheat zone at 10mm. A concept of equivalence ratio was aided since it involves premixed combustion of air and butane as fuel mixture. Additionally, burner was made to run under lean to ultra-lean modes and finest temperature were recorded. Both surface and submerged flame was generated effectively. Maximum temperatures recorded during surface and submerged flame condition was better by installing alumina rather than zirconia there by reaching a value of 631°C and 470°C respectively. Thus maximum thermal efficiency was calculated and found out to be 84%. Finally, emission parameters like NOx and CO where monitored and found out to be well within acceptable limits.

Photodegradation of Phenol over Flame-Made Sn-Doped ZnO Nanoparticles

Undoped ZnO and 0.5−5.0 at.% Sn-doped ZnO nanoparticles were synthesized by flame spray pyrolysis (FSP) using zinc naphthenate and tin (II) 2-ethylhexanoate dissolved in xylene as the precursors under a 5/5 (precursor/oxygen) flame condition. UV-Vis absorption characteristics of the samples were investigated for understanding and relating with the physiochemical characteristics in photocatalytic applications. Kinetic analyzes indicated that the photodegradation rates of phenol could be approximated as pseudo-first-order and zero-order kinetics in the case of undoped ZnO and Sn-doped ZnO nanoparticles respectively, according to the Langmuir-Hinshelwood model. The effect of Sn doping revealed the deterioration of the phenol photodegradation performance over ZnO-based catalysts, possibly due to the formation of a deep state in the ZnO band gap energy.

A Multi-Section Droplet Combustion Model for Spray Combustion Simulation

Since 1960s, from experimental observation, there are several stages for liquid droplets in multi-phase combustion: pure heating, pure evaporation without individual droplet combustion, and individual droplet combustion (burning) with individual flame around which enhances evaporation. As for individual burning droplets, they have envelope flame or wake flame regimes. From experimental and theoretical research, in liquid fuel combustion chambers, according to the space between the droplets, there are four typical droplet group combustion modes. Generally, the external group combustion mode and the internal group combustion mode are the two main modes, and there are individual burning droplets in multiphase combustion. Up to now, based on the literature information, no matter in Reynolds Averaged Navier Stokes (RANS) method, Large Eddy Simulation (LES) method or Point Direct Numeral Simulation (PDNS) method, droplets in multi-phase combustion are treated as pure evaporation points, corresponding to the bright blue flame condition, i.e., small droplets in hot gas mixture with the pure evaporation stage, so in species equation and energy equation, the droplet points are mass source and heat sink. As for the individual droplets burning mode, in point source simulation method, corresponding to the big droplet in cold gas phase mixture with yellow trail flame condition, the source terms in the species equation and energy equation should be the mass sink and heat source. The individual burning droplets affects the NO formation because the flame around the droplet has higher temperature than the local gas phase mixture mostly for the quasi-stoichiometric ratio reaction in individual droplet flame. In this paper, a new spray combustion model with the consideration of individual droplets combustion mode is brought forward. The existing modeling approach is extended with an ignition criterion and a droplet combustion correlation. The ignition criterion, which judges the droplet stage between pure evaporation and burning, and the droplet combustion correlation, which integrates the micro-scales droplet burning effects into point source term frame, are both selected from pioneer’s experimental work and added to the present existing widely used multi-phase combustion model. Then a jet spray flame is tested by the new model with RANS and LES method. The prediction results are compared with the literature experimental results. New model gives better simulation results in downstream regions. According to the results, this model added the individual droplet combustion mode in multi-phase combustion model, while its combustion correlations are quite rough at present. More verify studies should be carried in the future.