浓淡燃烧器两相流的分离特性和阻力特性的试验研究

针对浓淡燃烧器两相流的分离特性和阻力特性，采用冷态模化试验进行研究，全面了解它们的特性，以便改进燃烧器的性能。研究表明：浓淡分离装置的撞击挡块高度、挡块与隔板的距离都可以作为煤粉浓度调节的手段；挡块高度和气流速度对阻力损失的影响较大。     

煤粉浓淡分离装置的数值试验(CAT)研究

阐述了采用计算机辅助优化试验（ＣＡＴ）的方法，对撞击式煤粉浓淡分离装置进行的数值试验研究，计算结果和实验吻合较好。文章利用多相流理论进行分析，揭示了分离过程中若干问题的机理，得到了具有工程应用价值的结论。图７表１参５     

具有偏流块的弯管文丘里管组合浓淡燃烧器数值分析

研究了一种新型煤粉燃烧器,该燃烧器是由偏流块、弯管和文丘里管组合而成.通过数值计算的方法研究了这种特殊燃烧器的浓度分布特性,分析内部的气固两相流动特性,并通过改变偏流块角度和对比有无文丘流管的情况,研究偏流块角度和文丘里管对燃烧器出口浓淡分离效果的影响.采用RNG k-ε模型和Euler多相流模型研究气固两相流动.结果...     

煤粉浓淡旋流燃烧器喷口气固两相流动的数值模拟

在实验基础上，运用PNG－ASM和FCFSRT模型对煤粉旋流浓淡燃烧器的气固两相流进行数值模拟，并与实验结果进行对比，得出了合理的颗粒速度场和浓度场；比较和计算了浓缩和未浓缩的颗粒场特性，说明了浓淡分离燃烧器的浓淡燃烧的机理；最后对浓淡分离燃烧器煤粉混合特性作了数值模拟，指出了煤粉浓淡混合的区域。     

煤汾浓淡分离装置的数值试验（CAT）研究

阐述了采用计算机辅助优化试验的方法，对撞击式煤粉浓度分离装置进行的数值试验研究，计算结果和实验吻合较好。文章利用多相流理论进行分析，揭示了分离过程中若干问题的机理，得到了具有工程应用价值的结论。     

低NOx煤粉燃烧器的试验研究

对低NOx燃烧器从试验和数值模拟两个方面进行了研究,结果表明低NOx燃烧器浓淡两侧的速度比与管道气体速度和分隔板开缝与否均无关,大小为1.14～1.30,速度差为2.37 m/s(管道气体速度U=18 m/s时)～7.90 m/s(管道气体速度U=28 m/s时);低NOx燃烧器分隔板开缝时,相对不开缝结构阻力增加1.3%(180°扭曲分隔板)～10%(平直分隔板);低NOx燃烧器分隔板前布置阻挡锥时,阻力再增加10.1%(180°扭曲分隔板)～12.1%(平直分隔板);低NOx燃烧器浓淡两侧的固气比与分隔板有无开缝无关,浓侧煤粉射流的固气比随气流速度增大而增大,淡侧射流的固气比随气流速度的增大而减小,浓淡两侧的固气比随管道煤粉固气比的增大而增大.常规直流煤粉燃烧器加装不开缝的平直分隔板时,阻力增加17.7%,加装不开缝的180°扭曲分隔板时,阻力增加71.6%.低NOx燃烧器的分隔板开缝时,浓淡两侧的静压平衡,浓淡两侧的湍动能都增加,浓侧湍动能增加大约20%.     

锅炉一次风煤粉气流流过弯管时的数值模拟研究

对气固多相流动的数值模拟的方法和描述气固多相流动特性的数学模型进行了分析。通过分析和对煤粉气流流过弯管时的流动情况进行数值计算发现：采用Ｋ－ε双方程模型描述气相湍流模型,应用ＳＩＭ－ＰＬＥ算法计算气相速度场,然后采用ＦＳＲＴＳａｇｒａｎｇｅ法计算颗粒场特性,这是比较行之有铲的数值模拟管内气固多相流动的方法。     

排粉风机出口两相流动特性

通过利用9-26型高压离心风机,对排粉风机在风机叶轮不同转速、不同出口速度场条件下的风机出口两相流浓度进行了测量,测量发现除内侧附近区域外,沿着风机出口朝向外侧的方向固相浓度逐渐增高.测量结果给利用排粉风机出口的固相浓度分布特性来进行含粉气流的浓淡分离提供了参考.     

撞击式煤粉可调浓度浓缩燃烧器内气固两相流动的数值模拟

对一种可调浓度低负荷自动稳燃及防结渣装置中撞击式分离器内的气固两相流动进行数值模拟。气相采用ＲＮＧｋ－ε模型,固相采用ＦＳＲＴ模型,数值模拟结果能较好地预报分离器后浓度分布和速度分布,对该装置的可靠性提供理论依据,同时对现场调试有一定的指导作用。     

旋流雾化水膜除尘器内尘粒运动特性及分离效率

基于气固多相流复杂的运动特征，结合旋流雾化水膜除尘器的特点，同时考虑尘粒碰壁面黏附与反弹条件，颗粒间的碰撞与并聚、喷水加湿对颗粒间并聚及碰撞、颗粒运动特性的影响，并考虑颗粒对气相的作用，构建了描述旋流雾化水膜除尘器内湍流气固多相流的三维时均方程组，模型封闭采用k-ε／RNG模型，数值模拟了旋流雾化水膜除尘器内尘粒运动特性及分离效率。结果表明：在设置水膜除尘器尘粒遇壁面条件时，应设置尘粒碰壁为黏附；除尘器内干段、湿段比例、尘粒粒径、尘粒入口位置等对除尘效率高低均存在影响；壁面水雾膜的黏附及喷水对尘粒并聚影响较大，尘粒在除尘器内运动位移小于尘粒碰壁面反弹及不考虑尘粒并聚的情况，越有利于尘粒分离；除尘器入口速度越大及喉部喷水速度越大，越有利于尘粒的除去。     

Experimental investigation of stabilization and emission characteristics of ammonia/air premixed flames in a swirl combustor

Ammonia is a possible candidate for use as a hydrogen energy carrier as well as a carbon-free fuel. In this study, flame stability and emission characteristics of swirl stabilized ammonia/air premixed flames were experimentally investigated. Results showed that ammonia/air premixed flame could be stabilized for various equivalence ratios and inlet flow velocity conditions in a swirl burner without any additives to enhance the reaction of ammonia even though the laminar burning velocity of ammonia is very slow. The lean and rich blowoff limits were found to be close to the flammability limits of the ammonia flame. In addition, emission characteristics were investigated using an FTIR gas analyzer. The NO concentration decreased and ammonia concentration increased under rich conditions. Moreover, it was found that there is an equivalence ratio in rich condition in which NO and ammonia emission are in the same order.     

The effect of plasma jet ignition on flame propagation and sooting at the rich limit of flammability

It is shown that, as in the case of lean limits of flammability, rich limits are also considerably extended by plasma jet ignition. Soot formation is greatly reduced and flame propagation velocity increased when plasmas in certain media are used for the initiation of flames. The most effective media involve participation of both oxygen and fuel and the effect does not appear to be due to H alone. The fluid mechanical effects of energy release by combustion or volume generation by evaporating liquid within the plasma plug cavity are also considered. This leads to experiments on liquid-fed plugs which proved so effective near the lean limit. It is shown that these are also capable of increasing propagation rates and reducing soot formation at the rich limit and, while they are somewhat less effective than fuel and oxygen containing gaseous plasma feeds there, they are more likely to be interesting from the practical point of view.     

A theoretical study on Bunsen spray flames

The structure of Bunsen flame tip under the influence of dilute, monodisperse inert (water) or fuel (methanol) sprays is theoretically studied using large activation energy asymptotics. A completely prevaporized mode is identified, in which no liquid droplets exist downstream of the flame. Parameters for open and closed flame tips in the analysis consist of the amount of liquid loading indicating the internal heat loss for the water spray or the internal heat loss and heat gain for the rich and lean methanol-sprays, respectively, and the (negative) stretch coupled with Lewis number (Le) which strengthens the burning intensity of the Le>1 flame but weakens that of the Le<1 flame, respectively. For rich methane-air flames (Le>1) with water sprays (or lean methanol-spray flames with Le>1), closed-tip solutions are obtained. The burning intensity of the flame tip is enhanced with either decreasing liquid-water loading (or increasing liquid-fuel loading) or increasing stretch. Conversely, the negative stretch weakens the burning intensity of a lean methane-air flame (Le<1) with water sprays (or a rich methanol-spray flame with Le<1) and eventually leads to tip opening, i.e., flame extinction. The burning intensity is further reduced with either increasing liquid-water (or liquid-fuel) loading or increasing stretch. Moreover, the open flame tip is further widened when either the liquid-water loading (or liquid-fuel loading) or the upstream flow velocity is increased. It is noteworthy that the gradual increase of liquid-fuel loading strengthens the burning intensity of the lean methanol-spray flame (Le>1) and thus leads to the transition of flame configurations from conventional Bunsen cone through planar flame to inverted flame cone (a convex flame shape with respect to the upstream reactants). The critical value of liquid-fuel loading, at which there exists a planar flame rather than a Bunsen cone flame, is increased with either increasing upstream flow velocity or decreasing equivalence ratio.     

新型旋流煤粉燃烧器出口区域气固两相流场的PDPA实验研究

针对电站锅炉燃用煤种多变和负荷多变的问题,提出了一种新型的旋流燃烧技术,即利用在一次风管中加装浓缩煤粉构件实行煤粉浓淡分离的旋流浓淡煤粉燃烧器。使用三维相位多普勒颗粒分析仪对旋流浓淡煤粉燃烧器和双调风旋流煤粉燃烧器出口区域气固两相流场进行了实验研究,得出了两种不同燃烧器几何结构下的气固两相流场和颗粒浓度场,并进行了理论分析。     

Assessment of Mixture and Eulerian Multiphase Models in Predicting the Thermo-Fluidic Transport Characteristics for Fly Ash-Water Slurry Flow in Straight Horizontal Pipeline

The thermo-fluidic transport characteristics of the fly ash–water slurry flow in a straight horizontal pipe are predicted by deploying two different multiphase modeling strategies, viz. the mixture and the Eulerian multiphase models. Comparisons between the two model predictions in terms of the pressure drop and heat transfer coefficient are done along with the comparisons between the single (water) and the two phase system (slurry). Spherical fly ash particles, with diameter of 13 µm for an average inflow velocity ranging from 1 to 5 m/s and particle concentrations within 0–40% by volume for each velocity are considered as the dispersed phase carried by the carrier phase water. Significant differences between the two model predictions can be observed both from the qualitative and quantitative perspectives. This finally leads to the appropriate choice of the multiphase model for predicting the thermo-fluidic transport characteristics in slurry flow.     

Burning velocities of chlorinated hydrocarbonmethaneair mixtures

Results are presented for the variation in burning velocities with equivalence ratio and reactant gases preheat temperature for a number of chlorinated hydrocarbon compounds in methane-air mixtures of different concentrations at atmospheric pressure. Flame velocity of the mixture is determined with a Bunsen burner by measuring the unignited mixture approach flow rates and the area of the flame front. The method provides acceptable results and compares favorably with widely published methane flame data. Activation energy for a particular chlorinated compound was calculated by relating the flame velocity to the overall combustion reaction rate. Results are compared with nonchlorinated compounds and the available data in the literature. The reasons for discrepancies are discussed. The results show that increasing chlorine content decreases flame velocity and shifts the maximum flame velocity from fuel rich toward fuel lean. The flame velocity increases with increasing gas preheat temperature.     

Interactions for flames in a coaxial flow with a stagnation point

The possible burning structures existing in two co-flowing combustible mixtures with different compositions, and their implications to the field of turbulent combustion are examined in this study. A coaxial burner with a quartz plate was used to experimentally investigate the flames of methane/air and propane/air mixtures propagating in a coaxial flow impinging onto a stagnation surface. The possible burning structures were observed to be: (1) a single-flame (a lean or rich premixed flame); (2) a double-flame (two lean or rich premixed flames, or a rich premixed flame and a diffusion flame); and (3) a triple-flame (a rich premixed flame, a diffusion flame and a lean premixed flame). An inner (or outer) mixture, far beyond the flammability limit, can still burn if a stronger outer (or inner) flame supports it. The extinction limit of the top part of the inner hat-shaped premixed flame is nearly independent of the burning intensity of the outer flame. It was found that the inner flame has a wider flammable region than the outer flame, and that the latter has a narrower flashback region than the former. Both propane and methane flames may exhibit flame-front instability, although the former displays much more clearly than the latter. Cellular and polyhedral instabilities can exist individually or appear simultaneously in the inner flame. However, only polyhedral (stripped-pattern) instability was observed in the outer flame. Finally, the experiments were analyzed theoretically using a simple geometrical model incorporated with the numerical simulations. The predicted shapes and locations of the flames are in good agreement with the experimental observations qualitatively.     

基于FGM模型的同轴射流非预混火焰大涡模拟

采用直接数值模拟方法对二甲醚(Dimethyl Ether,DME)射流推举燃烧进行了研究（DNS）,分析了DME射流推举火焰结构、燃烧模式和推举稳定机理。数值模拟工况条件为：燃料由狭缝射出,初始温度500 K,射流速度138 m/s;伴流空气的初始温度1 000 K,流速3 m/s,压力为0506 6 MPa。研究表明：DME射流推举火焰与传统的边火焰有很大不同,在射流核心区内存在1条低温放热分支以及紧随其后的中温着火分支,并且推举稳定点位于贫燃侧;DME湍流射流推举火焰包含冷焰反应区(Cool Flame Zone,CFZ)、中温反应区(Intermediate Temperature Zone,ITZ)、富燃高温区(High Temperature Rich Burn Zone,HTR)以及贫燃高温区(High Temperature Lean Burn Zone,HTL)4种模式;在CFZ与ITZ区内湍流混合占主导,并且湍流混合会抑制低温放热;在HTR与HTL区内放热速率占主导地位,但是湍流会显著增强超贫燃区间内的高温放热速率;大部分热量在HTL和HTR区产生,而CFZ和ITZ区对总体产热的贡献微乎其微,但是所产生的中低温组分加快了高温着火过程;射流推举稳定性由贫燃侧的高温自着火反应机制所控制。     

二甲醚湍流射流推举火焰的燃烧机理研究

对长、宽、高为650 mm×400 mm×12 mm的半闭口狭窄矩形通道（海伦-肖装置）内的甲烷/空气层流预混火焰传播过程进行了实验研究,探究当量比φ在0.6~1.2范围内、火焰传播角度ω在垂直向下-90°至垂直向上90°区间对火焰前锋轮廓发展及非标准层流火焰速度的影响。结果表明：火焰在通道内的传播分为热膨胀、准稳态传播和端壁效应3个阶段,每个阶段具有各自不同的前锋轮廓特征。由于瑞利-泰勒不稳定性机制的作用,所有当量比工况下向上传播的火焰均在准稳态传播阶段中呈现出明显的锋面褶皱与胞状结构;对向下传播的火焰而言,其在贫燃工况（φ为0.6,0.8）下的胞状不稳定性得到了有效抑制,而在当量比φ=1.0及富燃工况（φ=1.2）下,该稳定性效应并不显著。火焰瞬时速度与标准层流速度的比值Ui/UL,在φ=0.6的极贫燃工况与其他当量比工况下展现出明显不同的发展特性,极贫燃工况火焰向上传播时（ω=90°）,Ui/UL随着传播过程的进行一直增大,直到火焰触碰壁面末端熄灭,整个过程Ui/UL与火焰传播方向呈正相关关系;而对于其他当量比工况,Ui/UL在传播过程中均先升高后下降,火焰触碰壁面末端熄灭前其值趋于稳定,其平均速度与标准层流速度的比值Ua/UL在水平传播（ω=0°）时达到最大值。