Browsing by Author "Taylan, Onur"
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Item Electrode degradation in micro-hollow cathode discharge reactors(2015-05) Pinero, Daniel III; Berberoglu, Halil; Taylan, OnurThis thesis presents an experimental study to understand the effects of different working fluids, flow rate, reactor hole diameter and dielectric thickness on the electrode degradation rate and total reactor lifetime of micro-hollow cathode discharge reactors. Oxidizing mediums such as air and carbon dioxide tend to degrade the reactors at a higher rate than non-oxidative mediums. Furthermore, larger dielectric thicknesses and smaller working fluid rates serve to decrease degradation. The overall longest reactor lifetime was accomplished at maximum diameter, thickness and minimum flowrate, resulting in a total lifetime of 14 hours 42 minutes. Additionally, creation of favorable magnetic fields through the use of nickel mesh electrodes was investigated in an attempt to increase the reactor lifetime. The results showed that the use of mesh electrodes decreased the total lifetime due to the higher energy plasma regime of the experimental reactors when compared to reactors found in the literature. Finally, the feasibility of utilizing MHCD reactors for oxygen production on a sample return mission to Mars was conducted. The study indicated that production quotas can be met but reactor lifetimes and power efficiency needed to be improved.Item Synthesis gas production using non-thermal plasma reactors(2014-08) Taylan, Onur; Berberoglu, HalilToday we face the formidable challenge of meeting the fuel needs of a growing population while minimizing the adverse impacts on our environment. Thus, we search for technologies that can provide us with renewable fuels while mitigating the emission of global pollutants. To this end, use of non-thermal plasma processes can offer novel methods for efficiently and effectively converting carbon dioxide and water vapor into synthesis gas for the production of renewable fuels. Particularly, non-thermal plasma technologies offer distinct advantages over conventional methods including lower operating temperatures, reduced need for catalysts and potentially lower manufacturing and operation costs. The non-thermal plasma reactors have been studied for ozone generation, material synthesis, decontamination, thruster for microsatellites, and biomedical applications. This dissertation focuses on producing synthesis gas using a non-thermal, microhollow cathode discharge (MHCD) plasma reactor. The prototype MHCD reactor consisted of a mica plate as a dielectric layer that was in between two aluminum electrodes with a through hole. First, electrical characterization of the reactor was performed in the self-pulsing regime, and the reactor was modeled with an equivalent circuit which consisted of a constant capacitance and a variable, negative differential resistance. The values of the resistor and capacitors were recovered from experimental data, and the introduced circuit model was validated with independent experiments. Experimental data showed that increasing the applied voltage increased the current, self-pulsing frequency and average power consumption of the reactor, while it decreased the peak voltage. Subsequently, carbon dioxide and water vapor balanced with argon as the carrier gas were fed through the hole, and parametric experiments were conducted to investigate the effects of applied voltage (from 2.5 to 4.5 kV), flow rate (from 10 to 800 mL/min), CO₂ mole fraction in influent (from 9.95% to 99.5%), dielectric thickness (from 150 to 450 [mu]m) and discharge hole diameter (from 200 to 515 [mu]m) on the composition of the products, electrical-to-chemical energy conversion efficiency, and CO₂-to-CO conversion yield. Within the investigated parameter ranges, the maximum H2/CO ratio was about 0.14 when H2O and CO₂ were dissociated in different reactors. Additionally, at an applied voltage of 4.5 kV, the maximum yields were about 28.4% for H2 at a residence time of 128 [mu]s and 17.3% for CO at a residence time of 354 [mu]s. Increasing residence time increased the conversion yield, but decreased the energy conversion efficiency. The maximum energy conversion efficiency of about 18.5% was achieved for 99.5% pure CO₂ at a residence time of 6 [mu]s and an applied voltage of 4.5 kV. At the same applied voltage, the maximum efficiency was about 14.8% for saturated CO₂ at a residence time of 12.8 [mu]s. The future work should focus on optimizing the conversion yield and efficiency as well as analyzing the temporal and spatial changes in the gas composition in the plasma reactor.