A parametric study for high-efficiency gas-liquid separator design

A gas liquid centrifugal separator is widely used in industry on account of its simple geometry and little maintenance. These separators have considerable advantages over filters, scrubbers or precipitators in term of compact design, lower pressure drop and higher capacity. A gas liquid centrifugal separator is a device that utilizes centrifugal forces and low pressure caused by rotational motion to separate liquid from gas by density differences. Efficient and reliable separation is required for the optimum operation. These separators are often operated at less than peak efficiency due to the entrainment of separated liquid through an outlet pipe which is closely associated with the very complicated flow phenomena involved. Design parameters such as length of the separation space, vane exit angle, inlet to outlet diameter ratio, models for separation efficiency and pressure drop as a function of physical dimensions are not available in literature. This leaves the designer with very little to go on except known designs and experimentation. The aim of present study is to perform a parametric study to get higher efficiency for gas-liquid separator. A parametric study has been carded out with the help of CFD tools to analyze a separation performance of a centrifugal separator by varying the length of separator space. The best design parameters are analyzed based upon obtained results, tangential velocities, vortices, total pressure losses. From the present study several attempts are made to improve the performance of conventional centrifugal separators.     

Theoretical investigation of pressure losses in cyclone separators

Theoretical analysis of pressure losses in cyclone separators under the consideration of geometrical and flow parameters including inlet geometry, surface roughness, velocity and particles concentration, has been performed and a new equation has been developed. The results obtained in this study are compared with experimental values for different type of cyclones. It was found that the proposed equation could be used to predict the pressure losses easily and it is worthy especially industrial applications.     

Particulate matter and gaseous emission rate from combustion of Thai lignite and agricultural residues in a fixed-bed combustor

This research has been conducted in order to obtain a database of emission rate of particulate matter and gases (CO, NO, and SO₂) from combustion of lignite and agricultural residues, such as rice husk. The experimental investigation was performed in a fixed-bed combustor. Thirteen stages–electrical low-pressure impactor was used to collect particles ranging in sizes from 40 nm to 10 μm. The results show that emission rate of total mass of particulate matter from combustion of rice husk is lower than that of lignite combustion but the total number of particles emitted is higher. This implies lower particle density from agricultural residue combustion. For co-firing lignite and rice husk, particulate matter emission is found to be higher than combustion of either lignite or rice husk and an increase in rice husk mass fraction in fuel mixture leads to an increase in particulate matter emission. From these quantitative data, it could be mentioned that the fuel characteristics influenced directly on particulate emission. For gaseous emission factors, CO and NO_x concentration decrease as SA/TA ratio increases. Meanwhile, SO₂ emission tends to increase. Both NO_x and SO₂ emissions are reduced as increased rice husk mass fraction in fuel mixture.     

温度对旋风分离器分离性能影响的数值研究

对不同温度条件下旋风分离器的压力损失和分离效率进行了数值研究.在数值预测时,气相场采用雷诺应力输运模型,应用随机轨道模型来模拟湍流流场中颗粒的运动轨迹.给出了不同温度条件下旋风分离器的压力损失和分离效率,并与实验数据以及经验模型的数据进行了比较.结果表明：压力损失和分离效率都随着温度的升高而降低,相对于经验模型而言,数值计算和实验数据吻合得更好.图10表1参12     

汽油/压缩天然气两用燃料发动机颗粒物排放特性研究

在某款1.4 L自然吸气两用燃料发动机上进行台架试验,用DM S500快速颗粒分析仪在发动机转速为4000 r/min不同进气压力工况下,对汽油和压缩天然气(compressed natural gas,CNG)的颗粒物排放特性进行采样分析.试验结果表明,两种燃料的总体颗粒物数量(particle number,PN)...     

A Theory Describing Sedimentation Particulate Fouling Thresholds Inside Heat Exchanger Tubes

This paper expounds a simple, fundamental theory for predicting sedimentation particulate fouling thresholds for horizontal flows inside heat exchanger tubes. The velocities and shear stresses at the tube wall predicted by this theory for keeping particulate matter suspended compare favorably with industrial experience and proprietary Chevron data. This theory is also not inconsistent with the literature in that the shear stress required for sedimentation fouling mitigation is roughly 4–6 Pa. However, the situation where small particles become encapsulated in the viscous sublayer cannot be resolved with a simple sedimentation particulate fouling threshold theory at this time, necessitating future research.     

喷油策略对汽油压燃颗粒物排放特性的影响

在一台单缸柴油机上研究了喷油参数(预主喷间隔角、预喷比例、主喷时刻和喷油压力等)对汽油压燃(gasoline compression ignition,GCI)颗粒物排放特性的影响。研究结果表明:喷油策略对缸内油气混合及进一步对燃烧过程的影响是其影响颗粒物排放特性的主要因素。在设定的研究工况下,随预主喷间隔角增大,积聚态颗粒数量浓度下降,但核态颗粒数量浓度基本不变,颗粒物中的核态和超细颗粒比例明显升高;增大预喷比例,核态颗粒和积聚态颗粒数量浓度均大幅降低,颗粒物中的核态和超细颗粒比例变化较小;主喷时刻提前,颗粒物数量浓度下降,平均粒径减小,数量浓度峰值向小粒径方向偏移;提高喷油压力可有效降低积聚态颗粒数量浓度,缩小缸内生成颗粒物的粒径范围,但对核态颗粒的数量浓度影响较小。     

Numerical Study of U—beam Inertial Separator

IntwctionChoulating fluldized bed (CFB) combustion is themost proInising clean coal teCboques that has receivedworld wide attention. A main feawt of CFB boilers isthe unedayed reCycle Of solid, coal and sorbantprtculate, in an extemal loop. SeParator which isreqH tO seParae the solid prtculate from the fluegasleaving the reactOr of CFB, play an twrtant role in theextemal solids reCycle loOP. It effects the combustionand desulPhurization Of CFB system peatiy.Presendy cyclone is most …     

Flue gas conditioning for reducing suspended particulate matter from thermal power stations

Increased population and industrial development demands sustainable electricity, the majority of which is produced by thermal power stations, which utilize coal as a fuel all over the world. Coal burning results in generation of large quantities of coal residues, which contains very fine particles that tend to become air-borne and which contribute to the formation of suspended particulate matter (SPM). Hence, in order to safeguard the environment against the emission of SPM, pollution control devices, such as cyclone separators, bag filters and electrostatic precipitators (ESPs) have been employed. In addition, flue gas conditioning (FGC) is practiced to increase the efficiency of ESPs, with the addition of chemical additives, or sprinkling water to the flue gas. This process increases the collection efficiency of the electrostatic precipitators, and thereby results in reduction of the SPM level. However, the effects of the process, which play an important role in efficient FGC, need to be investigated thoroughly before utilizing this method. With this in view, a critical review of various flue gas conditioning techniques employed for controlling the SPM level in thermal power stations is presented in this paper. The present study also reports analyses of data obtained from different thermal power stations in India as well as the rest of the world.     

Particulate matter mass measurements for low emitting diesel powered vehicles: what''s next?

Legislation word-wide imposes stringent emission standards for particulate matter emitted by diesel engines, as an outcome of evidence associating emitted particulate with a series of adverse health effects. Such emission standards call for significant reductions in the particulate matter emission levels for small and large on-road diesel vehicles. In fact, emission levels adopted for the near future are so low that the existing, regulated procedures might not be sensitive enough to accurately determine the absolute level of emissions. In this regard, extensive research is conducted in the direction of both improving existing procedures and developing alternative methods for more sensitive particulate matter measurements. This review paper summarizes the developments in the area and provides an outlook to the future. At first, the character of diesel particulate matter (DPM) is shortly discussed, mainly to show that the complex nature of emitted particulate is responsible for a series of implications when its quantitative determination is considered. Secondly, the regulated procedure for sampling and measurement of DPM is reviewed and its main qualities and shortcomings are presented. The recent technical advances aimed at improving the characteristics of the reference procedure in the measurement of ultra-low emission levels are then presented. Next the presentation of alternative methods follows which are gradually incorporated in regulations for particulate matter sampling. The strength of these techniques is that only a small fraction of exhaust is sampled and conditioned before measurement, hence significantly reducing the cost compared to the reference procedure. In addition to sampling, the determination of the actual particulate mass emitted is an area which has attracted significant developments. The most relevant instrumentation for DPM determination is also described and their potential for application in emissions certification is examined based on published evidence. Finally, the cost of the different sampling and instrumentation techniques is compared to demonstrate the cost-effectiveness of each option.     

不同煤粉燃烧对一次颗粒物排放特性的影响

在实验室条件下,以沉降炉作为燃烧设备,用8级Andersen粒子撞击器分离并收集燃烧后的颗粒物,研究了3种煤粉燃烧后生成的一次颗粒物中可吸入颗粒物排放的特性.结果表明,煤粉燃烧后,PM10、PM2.5、PM1的排放量并不是煤中灰分、固定碳或挥发分的单一函数.用Rosin-Ramm ler函数对一次颗粒物的质量-粒径分布进行曲线拟合,并计算了其中PM2.5/PM10、PM1/PM2.5的值.结果显示,灰分较高的煤粉生成的PM2.5/PM10、PM1/PM2.5值较高,灰分含量低的煤粉生成的PM2.5/PM10、PM1/PM2.5值较低.但PM2.5/PM10、PM1/PM2.5的值与灰分含量并不成正相关性.分析认为,不同煤粉中组分形式和含量的不同,影响了煤粉燃烧后一次颗粒物形成的过程,造成一次颗粒物排放特性的不同.     

循环流化床锅炉的现状及发展

循环流化床燃烧技术是一种清洁煤燃烧技术，以这种燃烧技术设计的锅炉具有较好的可靠性、经济性和环保性。分析了循环流化床锅炉旋风分离器的形式和整体布置的发展与改进，指出第三代采用方形分离器、冷却型紧凑布置的循环床燃烧技术将成为将来的发展方向。     

330MW CFB锅炉中心筒改造研究与应用

某循环流化床(CFB)锅炉的问题主要表现在:中心筒变形严重;旋风分离器效率低,飞灰含碳量大;炉内温度场分布不合理。电厂2016年对中心筒实施了改造,主要措施有:提升中心筒材质等级;用自由悬挂安装方式替代挂钩式安装;末节中心筒采用渐缩型结构,并设置偏心;采用迷宫式密封结构。改造后结果表明:床温降低30℃,稀相区差压提高500 Pa,氮氧化物减排50%。研究成果可在同类型CFB锅炉上推广。     

封闭空间内细水雾去除微细粉尘的影响因素实验研究

为研究细水雾去除悬浮在空气中的微细粉尘的影响因素,自行设计了小型封闭腔体并进行了不同工况条件下的细水雾降尘实验。首先采用阴影法对5种工作压力下的细水雾特性进行了测量表征,在此基础上开展了不同雾化特性细水雾对不同质量浓度PM5粉尘的降尘实验,实验中考虑了喷雾时长为5和10s两种情况,所测试粉尘为面粉;此外,还测试研究了不同粉尘粒径分布对细水雾降尘效果的影响研究。研究结果表明:细水雾对PM5粉尘的降尘效率随粉尘初始质量浓度的增加而提高,但当初始质量浓度增加到一定值后,降尘效率的提高不再明显;细水雾雾滴越细越密,其对PM5粉尘的降尘效率越高;延长细水雾喷雾时长,在一定程度上能够提高细水雾对PM5的降尘效率,且低质量浓度PM5比高质量浓度PM5受喷雾时长影响更大;针对平均粒径相差无几的粉尘,细水雾对粒径分布范围小的粉尘的降尘效率比对粒径分布范围大的粉尘的降尘效率高,预测细水雾降尘效率使用粉尘粒径分布范围比使用平均粒径更准确。     

基于动态模式分解的离心压缩机动态流场分析

动静流道相互作用引起的非定常流动是离心式压缩机内流的主要特征,借助模态分解方法可以有效提取出该流场中相干结构,进而可以说明该动静干涉流场的主要特征。本文将动态模式分解(Dynamic Mode Decomposition,DMD)方法应用于带无叶扩压器通道的离心式压缩机流场分析中,通过对动静干涉速度场和压力场的模态提取和分析,直观揭示出动静流道中的流体运动特征。在设计流量工况下,叶轮出口叶顶间隙的流体流动和动静流道干涉效应影响了叶轮出口的速度参数和压力参数的分布。在叶轮和扩压器流道中分别出现了频率1 715和725Hz的湍流相干结构,两频率和叶轮通过频率有关。动静干涉流道中压力沿叶高方向动态规律相似,而速度场沿叶高方向波动规律存在一定的差异。该特征可以为压缩机流场测试提供参考。     

喷油策略耦合EGR对柴油机燃烧过程与CDPF再生性能的影响

以匹配了可变截面几何增压系统(VGT)的D19高压共轨柴油机为研究机型,采用GT-Power和AVL FIRE构建了一维热力学整机模型和催化型微粒捕集器(CDPF)三维仿真模型,针对3 000r/min、50%负荷工况,研究了喷油策略耦合废气再循环(EGR)对燃烧过程和CDPF再生性能的影响。研究表明:随主喷定时提前,有效燃油消耗率(BSFC)先降后升,排气温度降低,排气流量与氧浓度变化则较小,排气中一氧化氮(NO)增加,CDPF再生速率逐渐降低,颗粒物残余量、压降与CDPF出口端二氧化氮(NO_2)同时增加;随EGR率增大,BSFC和排气温度升高,排气流量、排气氧浓度、排气中NO浓度则同时降低。在主喷定时较晚时,随EGR率增大,CDPF再生速率先升后降,颗粒物残余量先降低后略升高;而在主喷定时较早时,随EGR率的增大,CDPF再生速率降低,颗粒物残余量增多。在主喷定时较晚时,提高喷油压力使BSFC和排气温度明显降低;而在主喷定时较早时,提高喷油压力导致BSFC反而快速增加。此外,随喷油压力提高,排气流量与氧浓度变化较小,排气中NO浓度增加,CDPF再生速率逐渐减小,颗粒物残余量、压降和CDPF出口端NO_2排放同时升高。总体上,相比喷油压力,主喷定时对CDPF再生过程影响更大。     

Preparation of a trilayer separator and its application to lithium-ion batteries

Inorganic particulate film/poly(methyl methacrylate) (PMMA)/inorganic particulate film trilayer separators are prepared by means of simple dip-coating of inorganic particle layers on to both sides of PMMA thin films. The mechanical, thermal and electrochemical characteristics of the trilayer are investigated using scanning electron microscopy, a universal tensile machine, a thermal shrinkage test and a charge-discharge test. As a polymer matrix, PMMA has exceptional compatibility with the carbonate-based liquid electrolyte, which can result in improved battery/cell performance. When inorganic Al₂O₃ particles are used to coat the PMMA film, drawbacks associated with gel-type membranes, namely, poor dimensional stability and thermal stability are greatly improved. This inorganic trilayer membrane is believed to be an inexpensive, novel separator for application in lithium-ion batteries.     

A simple fuel bed model for predicting particulate emissions from a wood-waste boiler

Two simple physical and chemical models of a burning wood-waste fuel bed have been developed in order to predict the influence of fuel and operating parameters on particulate emissions from this source. First, a quiescent overfeed fuel bed is considered. Mass and energy balances along with assumptions for off-gas compositions are used to establish the bed off-gas temperature, composition, and bulk flow velocity. These have been used to predict entrainment of fuel particles. Second, the potential for fluidization of the fuel bed under typical operating conditions is considered. A simple comparison of bulk flow velocity with the minimum fluidization velocity for the bed is used as a criterion for fixed bed/fluidized bed operation. The ejected char and ash particles from the fluidized bed are included as part of the entrained particle stream in order to predict particulate emissions with a fluidized fuel bed. These two models are then used to predict the influence of undergrate airflow rate, fuel feed rate, and fuel size distribution on particulate emission from a wood-waste boiler.     

LP-EGR对增程器GDI汽油机燃烧和排放的影响

为进一步降低燃油消耗率和有害排放,开发增程器专用发动机,在一台缸内直喷(GDI)汽油机上选取增程器的3个运行工况点,开展了当量比燃烧模式下的低压废气再循环(LP-EGR)试验研究.结果表明:随着废气再循环(EGR)率的增加、点火时刻的推迟,缸内压力和放热率峰值降低且推迟,燃烧持续期延长,缸内燃烧由爆震逐渐过渡到失火,NOx排放降低.随着EGR率的增加,HC排放升高,CO和PM排放降低.点火时刻对HC、CO和颗粒物(PM)排放的影响规律随EGR率的变化而不同.引入EGR前、后的颗粒物总数量(PN)浓度值均在较低的数量级(105/cm^3).3个工况点综合优化后的最低有效燃油消耗率为219.1 g/(kW·h),较原机降低了7.75%.     

用于柴油机颗粒排放测量的定容取样系统研制

介绍了一种用于柴油机颗粒排放测量的定容取样系统,该系统可用于车用柴油机颗粒排放测量。