大氣壓共面介質阻擋放電等離子體射流的形成機理
發(fā)布時間：2018-09-12 13:58
【摘要】：大氣壓等離子體射流(APPJ)具有操作簡單、無需真空腔體、電子溫度高、氣體溫度低等優(yōu)點,被廣泛用于材料表面處理、環(huán)境治理和生物醫(yī)學領域。對APPJ的產(chǎn)生機理的理解是應用開拓、工藝優(yōu)化和控制的基礎。本文從實驗和數(shù)值模擬兩個方面對大氣壓共面介質阻擋放電(DBD)等離子體射流的形成和發(fā)展機理進行了研究。研究分為三部分:首先,實驗研究了氦氣大氣壓共面DBD等離子體射流的基本特性,得到放電電壓、氣流量、電極寬度、介質管徑和長度、異型介質管和外部氣體環(huán)境等放電條件對射流特性的影響。結果表明,電極之間DBD的特性影響APPJ的形成和發(fā)展;形成射流需要適當?shù)腍e氣流通道;但射流本身與氣流方向無關。其次,利用可控的外加電場、磁場和金屬管對氦氣大氣壓共面DBD等離子體射流的發(fā)展進行干預,研究了射流在外加電、磁場中的行為。發(fā)現(xiàn)射流路徑在電場、磁場中發(fā)生明顯的偏轉,射流長度減小,并出現(xiàn)徑向展寬或分離現(xiàn)象。外加浮置金屬管可以阻擋射流的傳播,但較高電壓下射流也能夠穿過金屬管;在金屬管施加正電壓有利于射流發(fā)展,而負電壓則阻擋射流傳播;維持射流傳播的電場從管內(nèi)指向管外,大致為~10kV/cm量級,使電子崩由管外朝向管內(nèi)發(fā)展。最后,利用二維流體模型模擬研究了氦氣DBD等離子體射流的發(fā)展過程。結果表明,DBD電極外的射流產(chǎn)生源于DBD形成后瞬時陰極附近空間正離子電荷及其產(chǎn)生的向外的軸向電場,它同時也是射流初始頭部。電子在強電場作用下被加速,導致氣體的電離和激發(fā),形成向外的射流;電子遷移后,在空間集聚的正離子電荷形成新的射流頭部并產(chǎn)生軸向電場,使射流繼續(xù)向外發(fā)展,直至電場減弱至擊穿電場以下。在陰極外,介質壁對射流的影響很小。DBD射流類似于單電極正電暈的“正流注”放電,它從介質管內(nèi)向外發(fā)展。
[Abstract]:Atmospheric pressure plasma jet (APPJ) has many advantages such as simple operation, no vacuum chamber, high electron temperature and low gas temperature. It is widely used in material surface treatment, environmental treatment and biomedicine. Understanding the production mechanism of APPJ is the basis of application development, process optimization and control. In this paper, the formation and development mechanism of coplanar dielectric barrier discharge (DBD) plasma jet at atmospheric pressure is studied in terms of both experimental and numerical simulation. The research is divided into three parts: firstly, the basic characteristics of helium coplanar DBD plasma jet at atmospheric pressure are studied experimentally. The discharge voltage, gas flow rate, electrode width, diameter and length of dielectric tube are obtained. The influence of discharge conditions such as the abnormal dielectric tube and the external gas environment on the jet characteristics. The results show that the characteristics of DBD between electrodes affect the formation and development of APPJ, and the formation of jet requires a proper He airflow channel, but the jet itself is independent of the direction of the flow. Secondly, the development of helium coplanar DBD plasma jet is interfered with by using controllable applied electric field, magnetic field and metal tube, and the behavior of the jet in external charging and magnetic field is studied. It is found that the jet path deflects obviously in the electric field and the magnetic field, and the jet length decreases, and the radial broadening or separation occurs. The external floating metal tube can prevent the jet from propagating, but the jet can also pass through the metal tube at higher voltage, the positive voltage applied in the metal tube is conducive to the development of the jet, while the negative voltage prevents the jet from propagating. The electric field which keeps the jet propagating from the inside of the tube to the outside of the tube is about 10 kV / cm, which makes the electron avalanche develop from the outside of the tube to the inside of the tube. Finally, the development process of helium DBD plasma jet is simulated with a two-dimensional fluid model. The results show that the jet generation outside the DBD electrode originates from the spatial positive ion charge near the instantaneous cathode and its outward axial electric field after the formation of the DBD, which is also the initial head of the jet. Electrons are accelerated under the action of a strong electric field, resulting in the ionization and excitation of the gas and the formation of an outward jet. After the electron migrates, the positive ion charge gathered in the space forms a new jet head and produces an axial electric field, so that the jet continues to develop outwards. Until the electric field weakens below the breakdown field. Outside the cathode, the influence of the dielectric wall on the jet is very small. DBD jet is similar to the "positive current" discharge of the single electrode positive corona, and it develops from the inside to the outside of the dielectric tube.
【學位授予單位】：北京理工大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：O358;O53
本文編號：2239218
[Abstract]:Atmospheric pressure plasma jet (APPJ) has many advantages such as simple operation, no vacuum chamber, high electron temperature and low gas temperature. It is widely used in material surface treatment, environmental treatment and biomedicine. Understanding the production mechanism of APPJ is the basis of application development, process optimization and control. In this paper, the formation and development mechanism of coplanar dielectric barrier discharge (DBD) plasma jet at atmospheric pressure is studied in terms of both experimental and numerical simulation. The research is divided into three parts: firstly, the basic characteristics of helium coplanar DBD plasma jet at atmospheric pressure are studied experimentally. The discharge voltage, gas flow rate, electrode width, diameter and length of dielectric tube are obtained. The influence of discharge conditions such as the abnormal dielectric tube and the external gas environment on the jet characteristics. The results show that the characteristics of DBD between electrodes affect the formation and development of APPJ, and the formation of jet requires a proper He airflow channel, but the jet itself is independent of the direction of the flow. Secondly, the development of helium coplanar DBD plasma jet is interfered with by using controllable applied electric field, magnetic field and metal tube, and the behavior of the jet in external charging and magnetic field is studied. It is found that the jet path deflects obviously in the electric field and the magnetic field, and the jet length decreases, and the radial broadening or separation occurs. The external floating metal tube can prevent the jet from propagating, but the jet can also pass through the metal tube at higher voltage, the positive voltage applied in the metal tube is conducive to the development of the jet, while the negative voltage prevents the jet from propagating. The electric field which keeps the jet propagating from the inside of the tube to the outside of the tube is about 10 kV / cm, which makes the electron avalanche develop from the outside of the tube to the inside of the tube. Finally, the development process of helium DBD plasma jet is simulated with a two-dimensional fluid model. The results show that the jet generation outside the DBD electrode originates from the spatial positive ion charge near the instantaneous cathode and its outward axial electric field after the formation of the DBD, which is also the initial head of the jet. Electrons are accelerated under the action of a strong electric field, resulting in the ionization and excitation of the gas and the formation of an outward jet. After the electron migrates, the positive ion charge gathered in the space forms a new jet head and produces an axial electric field, so that the jet continues to develop outwards. Until the electric field weakens below the breakdown field. Outside the cathode, the influence of the dielectric wall on the jet is very small. DBD jet is similar to the "positive current" discharge of the single electrode positive corona, and it develops from the inside to the outside of the dielectric tube.
【學位授予單位】：北京理工大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：O358;O53
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