本文選題：電流體動(dòng)力　切入點(diǎn)：靜電除塵　出處：《浙江大學(xué)》2015年碩士論文

【摘要】：高溫下除塵過程普遍存在于工業(yè)生產(chǎn)中,例如整體煤氣化聯(lián)合循環(huán)(IGCC)和增壓流化床燃燒聯(lián)合循環(huán)(PFBC)過程。高溫靜電除塵器是滿足上述氣體凈化要求的重要設(shè)備。對(duì)高溫靜電除塵過程的研究有助于揭示除塵機(jī)理,也能為工程實(shí)際中除塵設(shè)備的設(shè)計(jì)和優(yōu)化提供指導(dǎo)。本文應(yīng)用計(jì)算流體力學(xué)(CFD)對(duì)高溫下的線板式靜電除塵器進(jìn)行了數(shù)值模擬研究。建立了綜合考慮溫度場、電場、流場和顆粒動(dòng)力場的多場耦合模型,采用有限體積法對(duì)計(jì)算域進(jìn)行離散進(jìn)而求解電場,采用歐拉一拉格朗日方法求解氣固兩相流動(dòng)。主要研究內(nèi)容包含以下三部分： 第一部分是對(duì)靜電除塵器內(nèi)電場、流場和顆粒動(dòng)力場之間相互作用的研究。結(jié)果表明,電場對(duì)流場的影響表現(xiàn)為離子風(fēng)效應(yīng),離子風(fēng)的主要形態(tài)結(jié)構(gòu)是漩渦,它會(huì)在每個(gè)電暈極兩端形成一對(duì)反向的渦結(jié)構(gòu)。靜電場施加于顆粒的電場力對(duì)實(shí)現(xiàn)顆粒與氣體的分離起著重要作用。荷電顆粒形成的空間電荷使電勢(shì)和離子電荷密度稍有減小,顆粒在電場中形成的較大偏移會(huì)增強(qiáng)氣體的湍流。湍流脈動(dòng)使部分顆粒沉淀的時(shí)間變短,部分顆粒的沉積時(shí)間變長,部分顆粒甚至未能淀積。 第二部分是溫度對(duì)靜電除塵器內(nèi)流場特性、電場特性以及離子風(fēng)效應(yīng)影響的研究。模擬結(jié)果表明,氣體密度隨著溫度的升高而減小,氣體粘度隨著溫度的升高而增大。高溫會(huì)增厚收塵板處的邊界層,增強(qiáng)了全場的平均湍流強(qiáng)度。靜電除塵器的工作電壓范圍隨著溫度的升高而變窄。電暈極表面場強(qiáng)和整個(gè)電除塵器內(nèi)的平均場強(qiáng)均減小,離子電荷密度也減小。隨著溫度的升高,離子風(fēng)的影響強(qiáng)度減弱,范圍拓寬。 第三部分是溫度對(duì)靜電除塵器內(nèi)顆粒荷電、受力和軌跡的影響以及對(duì)整個(gè)除塵效率的影響的研究。首先研究了顆粒在運(yùn)動(dòng)過程中的荷電歷程,接著對(duì)顆粒所受曳力和電場力進(jìn)行了研究,最后總結(jié)高溫對(duì)除塵效率的影響并給出提高除塵效率的建議。模擬結(jié)果表明,對(duì)于10岬的顆粒,隨著溫度的升高,顆粒的荷電量減小,靜電力減小而Saffman升力、布朗力以及曳力均增大。顆粒的受到的力主要是靜電力和曳力。高溫增強(qiáng)了顆粒與流體的相互作用。溫度升高可能會(huì)使顆粒捕集變得困難,其原因可能有以下幾方面：運(yùn)行電壓的降低、煙氣量的增大、顆粒荷電減少導(dǎo)致的電場力減小、氣體粘度增大引起的曳力增加、高溫造成的顆粒與流體間相互作用的增強(qiáng)。
[Abstract]:The process of dust removal at high temperature generally exists in industrial production, such as integrated coal gasification combined cycle (IGCC) and pressurized fluidized bed combustion combined cycle (PFBC) process.High temperature electrostatic precipitator is an important equipment to meet the above gas purification requirements.The study of electrostatic dust removal process at high temperature is helpful to reveal the mechanism of dust collection and to provide guidance for the design and optimization of dust removal equipment in engineering practice.In this paper, computational fluid dynamics (CFD) is used to simulate the linear plate electrostatic precipitator at high temperature.A multi-field coupling model considering the temperature field, electric field, flow field and particle dynamic field is established. The finite volume method is used to discretize the computational domain and the electric field is solved. The Euler-Lagrangian method is used to solve the gas-solid two-phase flow.The main research contents include the following three parts:In the first part, the interaction among electric field, flow field and particle dynamic field in electrostatic precipitator is studied.The results show that the effect of electric field convection field is ionic wind effect, and the main form of ion wind is vortex, which forms a pair of opposite vortex structures at both ends of each corona pole.Electrostatic field applied to particles plays an important role in the separation of particles and gases.The space charge formed by charged particles decreases the potential and ion charge density slightly, and the larger migration of particles in the electric field will enhance the turbulence of the gas.Turbulence pulsation shortens the precipitation time of some particles, prolongs the deposition time of some particles, and even fails to deposit some particles.In the second part, the effect of temperature on flow field, electric field and ion wind effect in electrostatic precipitator is studied.The simulation results show that the gas density decreases with the increase of temperature, and the gas viscosity increases with the increase of temperature.The high temperature will thicken the boundary layer at the dust collecting plate and increase the average turbulence intensity of the whole field.The working voltage range of electrostatic precipitator becomes narrow with the increase of temperature.The electric field intensity on the corona electrode surface and the average field intensity in the whole electrostatic precipitator are both decreased, and the ion charge density is also decreased.With the increase of temperature, the influence of ion wind is weakened and the range is widened.In the third part, the influence of temperature on the charge, load and trajectory of particles in electrostatic precipitator and the effect of temperature on the dust removal efficiency are studied.Firstly, the charge history of particles in motion is studied, then the drag force and electric field force of particles are studied. Finally, the influence of high temperature on the dust removal efficiency is summarized and some suggestions to improve the dust removal efficiency are given.The simulation results show that the charge of particles decreases and the Saffman lift, Brownian force and drag force increase with the increase of temperature.The force of particles is mainly hydrostatic force and drag force.The interaction between particles and fluids is enhanced by high temperature.The increase of temperature may make it difficult to trap particles, which may be caused by the decrease of operating voltage, the increase of flue gas, the decrease of electric field force caused by the decrease of particle charge, and the increase of drag force caused by the increase of gas viscosity.The enhancement of particle-fluid interaction caused by high temperature.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：X701.2

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本文編號(hào)：1703744