Search Results (5)

Ammonia as a non-carbon fuel is expected to play an important role in the future, but it is difficult to be effectively utilized at this stage due to its flame retardancy and other characteristics. Therefore, we propose to use gliding arc plasma combined with a swirl burner to enhance the combustion performance of ammonia. The electrical characteristics, electron density, gas rotational temperature and the distribution of key active species in the burner were studied via optical emission spectroscopy (OES). With the increase of equivalence ratio (EQR), the width of the H_α line decreases significantly, indicating that the electron density shows a downward trend, even as the gas rotational temperature shows an upward trend. When the equivalence ratio was 0.5, the gas rotational temperature increases by about 320 K compared with the pure air condition. During pure air discharge, there will still be obvious NO emission due to the plasma reaction, but with the addition of NH₃, the NO content in the emission is significantly reduced. The light intensity of O atoms in the burner gradually decreases with the increase of the equivalence ratio, the light intensity of H atoms increases first and then decreases, and the light intensity of NH shows an upward trend. The reason may be that the plasma discharge effectively strengthens NH₃(E)->NH₂+H, NH₂+H->NH+H₂ and other reactions promote the initial reaction step of NH₃ which thus effectively strengthens the NH₃ combustion. Full article

To examine the plasma-assisted combustion of a scramjet, a microwave-enhanced gliding arc plasma method was proposed in this study, and the flame structure and combustion instability were observed. The mechanism of plasma-assisted combustion was obtained via a Bunsen experiment, and then the influence on supersonic combustion was obtained on a direct-connected scramjet. The active species of the flame was determined via optical emission spectroscopy, and the flame temperature was measured with a thermocouple. The luminous intensity of the OH radicals in the flame increased ninefold when the flame temperature was increased to 1573 K, but the luminous intensity of CH* and C₂ was not obviously changed with the excitation of arc plasma. Moreover, the DC arc plasma had no effect on the rotation and the vibration temperature of OH radicals under these experimental conditions. In the range of microwave energy less than 800 W, there was no typical change in the intensity of the radicals; however, when the microwave power was up to 1000 W, the effect became obvious. When plasma was applied to the scramjet, the plasma caused the pre-combustion shock train to move forward, and the initial and stable position of the flame was transferred from the cavity shear layer to the front of the fuel jet. These results clearly show that plasma free radical mechanisms cause changes to combustion modes. Full article

We studied the epoxy polymer surface modification using air plasma treatment in a Gliding Arc (GA) plasma reactor and a pulsed Dielectric Barrier Discharge (DBD). We employed optical emission spectroscopy (OES) measurements to approximate the vibrational and rotational temperatures for both plasma sources, as well as surface temperature measurements with fiber optics and IR thermography to corelate with the corresponding hydrophilization of the epoxy material. Water contact angle measurements revealed a rapid hydrophilization for both plasma sources, with a slightly more pronounced effect for the air DBD treatment. Ageing studies revealed stable hydrophilicity, with water contact angle saturating at values lower than 50°, corresponding to a >50% decrease compared to the untreated epoxy polymer. ATR-FTIR spectroscopy studies showed an additional absorption band assigned to carbonyl group, with its peak intensity being higher for the DBD treated surfaces. The spectra were also correlated with the surface functionalization via the relative peak area ratio of carbonyl to oxirane and benzene related bands. According to SEM imaging, GA plasma treatment led to no apparent morphological change, contrary to DBD treatment, which resulted in nano-roughness formation. The enhanced surface oxidation as well as the nano-roughness formation on epoxy surface with the air DBD treatment were found to be responsible for the stable hydrophilization. Full article

Tar removal is one of the greatest technical challenges of commercial gasification technologies. To find an efficient way to destroy tar with plasma, a rotating gliding arc (RGA) discharge reactor equipped with a fan-shaped swirling generator was used for model tar destruction in this study. The solution of toluene, naphthalene and phenanthrene is used as a tar surrogate and is destroyed in humid nitrogen. The influence of tar, CO₂ and moisture concentrations, and the discharge current on the destruction efficiency is emphasized. In addition, the combination of Ni/γ-Al₂O₃ catalyst with plasma was tested for plasma catalytic tar destruction. The toluene, naphthalene and phenanthrene destruction efficiency reached up to 95.2%, 88.9%, and 83.9% respectively, with a content of 12 g/Nm³ tar, 12% moisture, 15% CO_2, and a flow rate of 6 NL/min, whereas 9.3 g/kW·h energy efficiency was achieved. The increase of discharge current is advantageous in terms of decreasing black carbon production. The participation of Ni/γ-Al₂O₃ catalyst shows considerable improvement in destruction efficiency, especially at a relatively high flow rate (over 9 NL/min). The major liquid by-products are phenylethyne, indene, acenaphthylene and fluoranthene. The first two are majorly converted from toluene, acenaphthylene is produced by the co-reaction of toluene and naphthalene in the plasma, and fluoranthene is converted by phenanthrene. Full article

One of the most important methods of methane utilization is the conversion to synthesis gas (syngas). However, conventional ways of reforming methane usually require very high temperature, therefore non-thermal (non-equilibrium) plasma methane reforming is an attractive alternative. In this study, a novel plasma based reformer named 3D Gliding Arc Vortex Reformer (3D-GAVR) was investigated for partial oxidation of methane to produce syngas. The tangential input creates a vortex in the plasma zone and an expanded plasma presides within the entire area between the two electrodes. Using this method, the experimental results show that hydrogen can be produced for as low as $\$4.45$ per kg with flow rates of around 1 L per minute. The maximum methane conversion percentage which is achieved by this technology is up to 62.38%. In addition, a computational fluid dynamics (CFD) modeling is conducted for a cold plasma reformer chamber named reverse vortex flow gliding arc reactor (RVF-GA) to investigate the effects of geometry and configuration on the reformer performance. In this modified reformer, an axial air input port is added to the top of the reaction vessel while the premixed reactants can enter the cylindrical reaction zone through tangential jets. The CFD results show that a reverse vortex flow (RVF) scheme can be created which has an outer swirling rotation along with a low pressure area at its center with some component of axial flow. The reversed vortex flow utilizes the uniform temperature and heat flux distribution inside the cylinder, and enhances the gas mixtures leading to expedition of the chemical reaction and the rate of hydrogen production. Full article