电除尘器的脉冲电源研究北大核心CSCD

为解决电除尘器脉冲电源存在的负载上脉冲拖尾、电容剩余电压积累、负载上电压振荡问题,在充电二极管两端反向并联了一个辅助开关。详细分析了电路的工作原理,给出了选取影响负载上脉冲波形的关键元器件参数的理论依据,仿真分析和低压试验验证了解决方案的正确性。脉冲电源的改进,有利于进一步提高除尘效率和能量利用率。     

电除尘器的脉冲电源研究

为解决电除尘器脉冲电源存在的负载上脉冲拖尾、电容剩余电压积累、负载上电压振荡问题, 在充电二极管两端反向并联了一个辅助开关。详细分析了电路的工作原理, 给出了选取影响负载上脉冲波形的关键元器件参数的理论依据, 仿真分析和低压试验验证了解决方案的正确性。脉冲电源的改进, 有利于进一步提高除尘效率和能量利用率。     

Finite volume method for calculation of electrostatic fields in electrostatic precipitators

This paper presents a numerical method for calculation of coupled electric and space-charge density fields in electrostatic precipitators. It is based on the finite volume discretization of the solution domain by arbitrary polyhedral control volumes and employs an iterative segregated solution procedure of the resulting set of algebraic equations, amounting to a simple, accurate and efficient numerical technique. The method is tested on a number of cases for which analytical solution, numerical and/or experimental results exist. Also, shown are the results of calculation of a 3D model of electrostatic precipitator with spike discharge electrodes.     

A method for the location of sparks in electrostatic precipitators

A system for the location of sparks within an electrostatic precipitator can be used diagnostically to enable rapid identification of electrically weak spots due to wire or plate misalignments, design features or local defects in construction (e.g. sharp edges in regions of high electric stress). It can help to improve plant availability by the rapid location of faults due to broken wires while the unit is on-load, and so shorten the time for repair.Spark location is determined by measuring the transit time of an acoustic wave from a spark to microphones placed around each electrical zone. The bending of the sound paths around the plate edges is included in the analysis technique.The technique has been tested on a precipitator zone at a power station for both off-load and on-load operations. During on-load use the system can locate sparks to an accuracy of ±3 lanes and ±3 wires.     

Characterization of brush type discharge electrodes and impact of enhanced corona discharge on operation of electrostatic precipitators

This project presents the results of investigation of current/voltage characteristics of brush type discharge electrodes (BTDE) in tube type electrostatic precipitators and the effect on operation. Experimental investigations were conducted with discharge electrodes of different wire diameter and different brush diameter. The effect of electrode geometry on current/voltage behavior was recorded. Corona current with brush type discharge electrodes was modeled and compared with experimental data. Brush type discharge electrodes produce an enhanced corona current compared with wire type discharge electrodes. Limited enhanced corona has improving effect on collection efficiency. An adjusted correlation was therefore deduced from experimentally obtained current/voltage data with BTDE.     

Simulation of the electric field in wire-plate type electrostatic precipitators

The paper presents a general Control Volume model for electric field simulation in wire-plate type electrostatic precipitators, along with a new injection law for charge density. The model is validated against empirical equations and experimental data in the literature when applied to the wire-plate and point-plate configurations. The voltage current characteristics and detailed distribution of field and charge density are characterized, particularly for the case of barbed wire electrode. The effects of geometric variations, such as the sharpness of the tip and the direction of the needles with respect to the plate, are investigated.     

Monitoring of electrostatic fire and explosion hazards at the inlet to electrostatic precipitators

The paper deals with the continuous monitoring of electrostatic fire and explosion hazards that can occur at the inlet to electrostatic precipitators (ESPs) when highly charged dust particles are transported by a gas carrier that can be the mixtures of both incombustible and combustible flue gases. The risk of ignition and even explosion is especially high in the presence of an explosive mixture of oxygen and, e.g., hydrocarbons, carbon monoxide, etc. To avoid the danger of electrostatic discharges and their consequences for a whole installation including an electrostatic precipitator a method and a specially designed and built system should effectively enable the continuous monitoring of the hazards and should immediately manage any automatic control system or some other control elements. Some theoretical considerations concerning the method proposed, the physical quantities that must be measured, and the derivation of a novel dynamic safety criterion for assessing the risk of hazardous electrostatic discharges are presented. Finally, the author presents and discusses the possible practical application of the microprocessor-based measuring system verified experimentally in the past to the continuous monitoring of the hazards and to the management of an automatic control system to be put into operation. The paper presents a certain idea and proposal of the problem's solution based on the author's many years' experience in the field of pneumatic transport of dusts, powders and granular materials, of the electrostatic measurements of electric and mechanical quantities characteristic of the particulate transport, and of the risk and prevention of discharges of static electricity in transporting pipes and silos, vessels, etc.     

Modeling of the electrostatic corona discharge reactor

A model is presented for the electrostatic corona discharge reactor (ECDR) in a pin-plate configuration. The main objective is to describe the fundamental chemistry and physics governing the discharge behavior and to predict the ECDR performance under various operating conditions. The electric field strength is estimated assuming a space-charge-free field. A two-term spherical harmonic expansion is used to solve the Boltzmann equation for the electron energy distribution function (EEDF) and calculate the electron-molecule reaction rates using collision cross-section data. Species continuity equations are solved for the dry and wet air systems to predict ozone and NO_x at various feed flow rates (1630, 4890, 14, 670 cm/s) and an applied voltage of 10 kV. Among the various results reported, it is noted that the calculations indicate the Maxwell EEDF cannot be used because it overpredicts the electron-molecule rate coefficients by several orders of magnitude     

CFD modeling of particle charging and collection in electrostatic precipitators

A CFD model was developed to describe the particle laden gas flow through an ESP, particle charging and collection. The corona discharge was modeled using the open source software OpenFOAM to solve the Poison and charge conservation equations, and results were entered using user-defined field functions in the commercial CFD software STAR-CCM+. The gas flow, EHD flow, particle charging and dynamics were modeled using STAR-CCM+. The developed CFD model allows for direct solution of the drift and diffusional flux of gas ions. The influence of the various ESP dimensions, operating parameters and ash properties on the collection efficiency are reported.     

Numerical models in simulating wire-plate electrostatic precipitators: A review

This paper attempts to review the most important works on numerical simulation of processes in electrostatic precipitators published so far. Only the wire-plate configuration is considered, although the discharge electrode may have different geometries: smooth cylinder, barbed wire of different shape or helical electrode. Different mathematical models and numerical algorithms for gas flow, electric field, corona discharge and particle transport have been compared. The discussion is focused on coupling between different phenomena. A continuous progress has been shown from early works published about 30 years ago, which dealt with much idealized models of the problem, to recent publications, where the numerical predictions show close agreement with the experimental data.     

Theoretical analysis of removal of oxides of sulphur and nitrogenin pulsed operation of electrostatic precipitators

An investigation has been made of the various plasma chemistry reactions that occur in the corona discharge of an electrostatic precipitator operating in a typical flue gas. Calculations have been made of the rate coefficients for electron dissociation of the principal gaseous components, namely, nitrogen, oxygen and water vapor as functions of electric field. In addition, calculations have been made of the rates of ionisation and attachment and also the rates of excitation of the principal excited states. The calculations indicate that sulphur dioxide is removed principally by reactions with OH radicals to produce sulphuric acid, while nitrogen oxides are removed principally by reduction via the N radical to molecular nitrogen. However, for these reactions to occur, values of E/N of 70 Td or more are necessary, which is higher than the E/N of 30 Td at which electrical breakdown normally occurs; E is electric field strength and N is the gas number density. Approximate calculations indicate that, for an E/N of 100 Td, voltage pulses of width less than 1 μs need to be applied to avoid breakdown. It is also shown that small quantities of nitrous oxide are produced and that the presence of water vapor has a significant effect on the plasma chemistry and increases the breakdown voltage     

A new IGBT control and drive circuit for high-power full-bridge inverter for electrostatic precipitators

In this paper, aiming at the characteristics of high-power full-bridge inverter, a new IGBT control and drive circuit is designed, in which UCC3895, a phase shift and dead-time control chip, MC33152, a high-speed dual-phase driver, and PT6 isolation transformers consist the core part. The circuit can regulate its frequency, phase angle and dead-time, while possessing following features: short turn-on/off time, low-voltage peak, simplified circuit structure, high reliability and universality, etc. Now, it has been successfully applied on the power supply for 72 kV/1 A high-frequency high-voltage electrostatic precipitator.     

Measurement of the electrostatic powder coating properties for corona and triboelectric coating guns

Measurements have been made of the deposited powder layer for conventional electrostatic corona powder guns and triboelectric guns. By selectively removing the powder layer under computer control conditions, measurements of the powder thickness, and the adhesive properties of the powder layer have been obtained for variation in the coating process and detailed comparisons have been obtained for both coating systems.     

Vibration of collecting electrodes in electrostatic precipitators – Modelling,measurements and simulation tests

The paper presents a numerical model for simulating the vibration of collecting electrodes in an electrostatic precipitator. The method of finite elements (FEM) was used to describe the shell elements of the collecting electrodes. The remaining elements of the system were modelled with the application of the rigid finite elements method (RFEM). The results of measuring validation and testing calculations are discussed.     

Effect of air flow on corona discharge in wire-to-plate electrostatic precipitator

This paper analyses corona discharge in ambient air with laboratory-scaled wire-to-plate electrostatic precipitator (WPESP). The electric field is behind the electro hydrodynamic (EHD) flow in air. Its measurements provide complementary results for the corona discharge study because the classical theory based on the current and voltage data is unsatisfactory. Taking into account the dynamic air flow velocity is perpendicular to the active wires, measurement method of the positive and negative DC corona current density and electric field, has been introduced. It has been shown also that the dynamic air flow velocity modifies the current density and the electric field distributions on the planes surfaces of the WPESP.     

Double-mode electrostatic dispersing prism for electron pulse time-domain compression

The generalized theory of double-mode electrostatic dispersing prism for time-domain compressing electron pulse is presented. The fundamental difference between the two modes of o mode and e mode lies in the dispersive dependence of electron's time of flight on its initial kinetic energy at prism entrance: the electrons with higher initial axial energy definitely have longer time of flight for o mode, while not the case for e mode, which results from the electron pulse's U-shaped motion in the prism. The dispersive dependence of time of flight constitutes the mechanism of electron pulse compression for each mode. An example is given to demonstrate the issue of parameter choosing for the prism and to verify its tunable performance of compression.     

Numerical simulation of the electrostatic powder coating process with a corona spray gun

In this paper results of investigations are described aiming to numerically simulate the electrostatic powder coating process using an extended commercial computational fluid dynamics (CFD) code. The fully three-dimensional turbulent flow was calculated. Based on the Lagrangian approach the trajectories of the powder particles were modelled considering electric and aerodynamic forces. In the calculations of the particle propagation both the particle size distribution and the particle charge distribution obtained through experiments have been applied. The model accounts for the space charge effect of the charged particles and the turbulence dispersion on the particle trajectories. It was found that the space charge plays an important role for the final spray pattern shape, also increasing the transfer efficiency. The numerical results, such as velocity profiles, static and dynamic film thickness on the target were in good agreement with experiment.     

Nanoflare heating model for collisionless solar corona

The problem of coronal heating remains one of the greatest unresolved problems in space science. Magnetic reconnection plays a significant role in heating the solar corona. When two oppositely directed magnetic fields come closer to form a current sheet, the current density of the plasma increases due to which magnetic reconnection and conversion of magnetic energy into thermal energy takes place. The present paper deals with a model for reconnection occurring in the solar corona under steady state in collisionless regime. The model predicts that reconnection time in the solar corona varies inversely with the cube of magnetic field and varies directly with the Lindquist number. Our analysis shows that reconnections are occurring within a time interval of 600 s in the solar corona, producing nanoflares in the energy range 10 ²¹–10 ²³ erg /s which matches with Yohkoh X-ray observations.     

Three-dimensional EHD simulation for point corona electrostatic precipitator based on laminar and turbulent models

The three-dimensional flow interaction for tuft or point corona for industrial electrostatic precipitators was investigated using both laminar and turbulent flow models. The secondary flow distribution based on laminar flow model forms a pair of organized donut-shaped rings generated from every corona or tuft points, while a pair of rings is less organized for turbulent flow model. When the primary flow exists, the organized spiral motion for turbulent model is further diffused in the direction of gas flow and increased N_EHD, which leads to turbulent flow. Turbulent model appears to be more appropriate for predicting the wire-plate ESP based on experimental investigation.     

静电放电电磁脉冲模拟装置

介绍了静电放电电磁脉冲（ESD EMP）的特性。研究了用ESD 模拟器产生ESD EMP的方法,并给出了ESD EMP的时域波形和频谱。在研究ESD模拟器的基础上,首次通过ESD模拟器和GTEM室的结合,在GTEM室内产生了均匀的、重复性和线性好的ESD EMP。实验表明,用这种装置能够实现对静电放电电磁脉冲的实验室模拟。实现了人们用GTEM室产生ESD EMP的梦想。