利用電漿放電點燃噴流擴散火焰

Abstract

本研究利用非熱平衡電漿引燃噴流火焰，主要在於探討非熱平衡電漿位置對火焰引燃的難易、機率和所需引燃時間長短。同時，本文也會針對電極的結構配置與電漿之電場特性，對火焰引燃時間、引燃難易度和引燃機率，做深入的探討與比較。 本研究主要藉由兩種電極配置產生非熱平衡電漿，用以引燃火焰，電極配置分別為雙尖端電極 (Rod-Type) 和雙鎢絲電極 (Wire-Type)。研究結果發現，雙鎢絲電極能產生流光放電 (Streamer Discharge) ，成功引燃雷諾數2000 ~ 8000範圍內之非預混火焰;然而，雙尖端電極配置則無法引燃火焰。此外，本研究發現，火焰引燃的機率會隨著電漿能量密度的增加而提高，但隨著引燃位置徑向距離逐漸增加，引燃機率會逐漸降低。電漿引燃所需時間結果與引燃機率結果一致，即引燃機率高，所需之引燃時間則較短。另一方面，隨著燃料噴流雷諾數增加，火焰需要引燃的時間也增加。本研究也發現，當電漿放電足夠靠近石英燃料管，電漿電位可能極化石英管，影響火焰引燃機率與難易度。

The present study investigated the application of non-thermal plasma discharges to the ignition of a jet diffusion flame. The flame was fueled with methane and had a nominal Reynolds number of Re = 2000. The volume flow rate of co-flow air was fixed at 100 LPM. Two different configurations of electrode arrangement were tested: opposed rod electrodes with pin tips and opposed wire electrodes. Results showed that opposed wire electrodes (made of tungsten) successfully ignited flames, but not opposed rod electrodes. It was shown that the ignition probability was increased with the energy density deposited in plasma. The ignition probability was seen to decrease, as the plasma was further away from the fuel nozzle. On the other hand, the ignition probability was increased when the discharge was close to the stoichiometric mixture fraction. However, the probability could be affected by the polarization of the fuel nozzle if the discharge was close enough to the nozzle. Results of the most probable ignition time were consistent with those of the ignition probability, i.e. the larger the ignition probability was, the shorter the ignition was.