多孔介质燃烧火焰面特性数值模拟

为研究低热值气体在多孔介质燃烧器中的火焰面特性,采用计算流体力学方法对二维氧化铝(Al2O3)小球堆积床多孔介质燃烧器内气体燃烧进行模拟。考虑气体的对流扩散和气固间的对流换热及固固间的辐射换热,研究多孔介质燃烧器中混合气体燃烧特性规律,对火焰面形态和火焰面移动规律进行分析。模拟结果表明,堆积小球多孔介质燃烧器内火焰面的移动速度较小,其数量级在10-4 m/s;多孔介质燃烧器中火焰面移动速度随着预混稀薄气体当量比的降低而增大,随入口速度的增大而增大;当预混气体的入口速度较大时,火焰面呈较厚抛物线状,入口速度较小时,火焰面呈较薄平整状。     

微细直管燃烧器的散热损失研究

为了解微细直管燃烧器散热损失的大小，采用内径为0.6mm的微细陶瓷管进行氧气和甲烷气体的燃烧实验，测量了微细直管外壁面的温度，研究了氧气和甲烷的总流量和质量比对壁面散热的影响，以及不同总流量下直管壁面温度的动态变化过程。研究结果表明，混合比小于当量混合比时，随着混合比的增加，燃烧放热功率增加，壁面温度升高，管壁的散热功率增加；管壁的散热量占了很大一部分燃烧放热量，文中测量的管壁散热量最大为燃烧放热量的42%；在管壁散热量中，辐射散热量占很大一部分，最大达到总散热量的65%；随着总流量的增加，燃烧反应区的长度增加，轴向的壁面温差减小，壁面升温速率增大。     

外置瑞士卷多孔介质燃烧器贫燃试验

对一种新型外置瑞士卷多孔介质燃烧器的贫燃特性进行了试验研究,对其点火预热启动过程及其不同预混气体浓度、流量等工况参数条件下的温度分布、排放特性进行了测量;分析燃烧器的启动方法以及流量、预混气体浓度等有关工况参数对其燃烧特性的影响规律。结果表明,燃烧器冷启动时甲烷氧化率较低,有大量的CO生成;由于多孔介质的存在,燃烧器整体升温较慢,无局部高温,NOx生成量较小;在相同预混气甲烷浓度条件下稳定燃烧时,此类型燃烧器相对无瑞士卷结构的多孔介质燃烧器,在同一预混气甲烷浓度条件下对流量具有较好的适应性,火焰稳定性好;预混气甲烷浓度越大、驻留时间越长、燃烧温度越高,甲烷氧化率也越大。     

多孔陶瓷燃烧器火焰温度的测定

实验采用红外辐射测温法测出多孔陶瓷燃烧器中预混火焰沿气流方向的温度分布曲线。结果表明，燃烧器中的燃烧火焰与自由火焰相比，燃烧温度显著提高，验证了理论预测的这一特征；也说明利用红外测温能克服热电偶等直接测温的特点，得到了温度变化的直实特性。     

多孔陶瓷燃烧器火焰温度的测定

实验采用红外辐射测温法测出了多孔陶瓷燃烧器中预混火焰沿气流方向的温度分布曲线。结果表明，燃烧器中的燃烧火焰与自由火焰相比，燃烧温度显著提高，验证了理论预测的这一特性；也说明利用红外测温能克服热电偶等直接测温的缺点，得到了温度变化的真实特性。图５参８     

空气槽对微型双通道螺旋型过量焓燃烧器工作特性的影响

为了解空气槽对平板微型双通道螺旋型过量焓燃烧器(Swiss-roll燃烧器)工作特性的影响,采用甲烷/空气预混气,在带有空气槽和没有空气槽的平板Swiss-roll燃烧器中进行燃烧实验。实验结果表明:空气槽有助于扩展微燃烧器的可燃极限,使燃烧器在更大的空气过量系数和更小的甲烷流量下工作,同时增加了燃烧器外壁的温度梯度。另外,对带有空气槽的微燃烧器进行了数值模拟。数值结果表明,高温燃气对未燃混合物有很强的加热作用,一方面使预混火焰面发生倾斜,另一方面使预混火焰在微燃烧器内部的位置随着流速、空气过量系数、外界散热的变化而变化。     

复杂曲面花瓣燃烧器煤粉燃烧数值分析

应用贴体坐标结构化网格对复杂曲面的花瓣燃烧器进行三维(360°)煤粉燃烧的数值模拟。给出花瓣燃烧器的流场、颗粒场、温度场和浓度场,分析花瓣燃烧器的稳燃及低NOx燃烧原理和特性。计算结果表明,在花瓣稳燃器的作用下,煤粉气流进入炉内能立即在瓣后着火燃烧,并在径向回流区中形成稳定的"值班火焰",为整个风粉气流的着火燃烧提供稳定的热量来源。花瓣燃烧器的火焰在炉内呈花瓣状,造成局部缺氧区,有利于降低NOx的排放和低挥发分煤在广泛负荷范围内的稳定着火和完全燃烧。     

黎开预混燃烧器热声不稳定的试验研究

为探索燃烧过程中热声不稳定的产生机理，搭建了黎开(Rijke)预混燃烧器热声不稳定研究试验台架，并进行了试验研究。Rijke预混燃烧器为直径40 mm，管长1066 mm的不锈钢圆管，下端封闭，上端开口；致密堇青石材质的多孔介质稳燃体位于燃烧器四分之一管长处，甲烷与空气的预混气体在稳燃体上方燃烧形成平面火焰作为加热热源。试验发现，化学当量比f 对Rijke预混燃烧器内热声不稳定的强度有重要的影响，维持Rijke预混燃烧器持续燃烧的下限极限化学当量比和上限极限化学当量比分别为0.63和1.75。另外，试验发现了预混燃烧器内热声不稳定的最大强度并非发生在f=1.0时，而是在f=1.30左右；并且当1.0￡f ￡1.5时，预混燃烧器内的热声不稳定均维持较高的强度。     

新型煤粉燃烧器的燃烧机理分析

分析了国内超临界和超超临界锅炉采用的几种新型煤粉燃烧器的燃烧机理。主要特点是采用多级配风技术灵活控制燃烧器出口的煤粉火焰燃烧过程;实现着火初期低氧燃烧和火焰内NOx还原技术;在旋流式燃烧器内采用煤粉浓缩技术和环形齿状稳燃器或直流过渡风,在喷口附近煤粉气流着火初期,加强热烟气回流和维持高温及低氧燃烧,促进挥发分析出过程中的NOx还原,并实现快速着火和低负荷稳定燃烧;在A-PM型直流式燃烧器上采用带扩压管的缩放型小喷口结构,增强稳燃能力和维持高温和低氧燃烧,促进NOx还原,并均衡火焰温度,降低水冷壁的热负荷;设置可调节燃尽风进一步提高炉内脱氮效果和提高燃烧效率等。     

煤质下降对炉内燃烧稳定性的影响及解决措施

分析了燃煤质量下降对电站燃煤锅炉炉内火焰温度水平、燃烧器出口区域火焰温度水平及入炉煤量、风量、燃烧器出口煤粉气流速度的影响,进而对煤粉气流着火过程和炉内燃烧稳定性的影响。对此,提出了采用切圆燃烧锅炉卫燃带背火侧分块布置和PCSB煤粉燃烧器等措施,这些措施对于燃用低挥发分难燃煤种锅炉效果极为显著。     

Simulation of heat and mass transfer processes in the experimental section of the air-condensing unit of Scientific Production Company “Turbocon”

A mathematical model was developed to be used for numerical analysis of heat and mass transfer processes in the experimental section of the air condenser (ESAC) created in the Scientific Production Company (SPC) “Turbocon” and mounted on the territory of the All-Russia Thermal Engineering Institute. The simulations were performed using the author’s CFD code ANES. The verification of the models was carried out involving the experimental data obtained in the tests of ESAC. The operational capability of the proposed models to calculate the processes in steam–air mixture and cooling air and algorithms to take into account the maldistribution in the various rows of tube bundle was shown. Data on the influence of temperature and flow rate of the cooling air on the pressure in the upper header of ESAC, effective heat transfer coefficient, steam flow distribution by tube rows, and the dimensions of the ineffectively operating zones of tube bundle for two schemes of steam–air mixture flow (one-pass and two-pass ones) were presented. It was shown that the pressure behind the turbine (in the upper header) increases significantly at increase of the steam flow rate and reduction of the flow rate of cooling air and its temperature rise, and the maximum value of heat transfer coefficient is fully determined by the flow rate of cooling air. Furthermore, the steam flow rate corresponding to the maximum value of heat transfer coefficient substantially depends on the ambient temperature. The analysis of the effectiveness of the considered schemes of internal coolant flow was carried out, which showed that the two-pass scheme is more effective because it provides lower pressure in the upper header, despite the fact that its hydraulic resistance at fixed flow rate of steam–air mixture is considerably higher than at using the one-pass schema. This result is a consequence of the fact that, in the two-pass scheme, the condensation process involves the larger internal surface of tubes, results in lower values of Δt (the temperature difference between internal and external coolant) for a given heat load.     

氯对CO氧化抑制作用的实验研究

利用常压管式流动反应装置研究CO/H2/O2/Cl2的氧化过程以了解氯对CO氧化的抑制作用。实验中反应温度的范围是973~1 273 K,入口反应气体中氯原子和氢原子的物质的量之比[Cl]/[H]的范围是0到1。反应产物通过红外光谱仪在线检测。结果表明,CO的转化率随反应温度的升高而增大,随[Cl]/[H]的升高而减小。HCl的生成反应及HCl与OH的反应HCl+OH=Cl+H2O降低了反应体系中OH的浓度,导致CO转化率的下降。提高反应温度可减轻氯对CO氧化的抑制作用。     

Analysis of experimental characteristics of multistage steam-jet electors of steam turbines

A series of questions for specification of physical gas dynamics model in flow range of steam-jet unit and ejector computation methodology, as well as functioning peculiarities of intercoolers, was formulated based on analysis of experimental characteristics of multistage team-jet steam turbines. It was established that coefficient defining position of critical cross-section of injected flow depends on characteristics of the “sound tube” zone. Speed of injected flow within this tube may exceed that of sound, and pressure jumps in work-steam decrease at the same time. Characteristics of the “sound tube” define optimal axial sizes of the ejector. According to measurement results, the part of steam condensing in the first-stage coolant constitutes 70–80% of steam amount supplied into coolant and is almost independent of air content in steam. Coolant efficiency depends on steam pressure defined by operation of steam-jet unit of ejector of the next stage after coolant of steam-jet stage, temperature, and condensing water flow. As a rule, steam entering content of steam-air mixture supplied to coolant is overheated with respect to saturation temperature of steam in the mixture. This should be taken into account during coolant computation. Long-term operation causes changes in roughness of walls of the ejector’s mixing chamber. The influence of change of wall roughness on ejector characteristic is similar to the influence of reverse pressure of the steam-jet stage. Until some roughness value, injection coefficient of the ejector stage operating in superlimiting regime hardly changed. After reaching critical roughness, the ejector switches to prelimiting operating regime.     

热扩散式风量传感器在中速磨煤机一次风自动调节中的应用

鉴于节流式风量测量装置对直管段长度要求较高,信号的稳定性较差的局限性,提出采用准确性、稳定性较高的热扩散式风量测量装置,给出了其基本原理,并针对其存在的自动控制系统不稳或发散振荡问题,分析了流量温度特性动态过程曲线,提出将风量测量装置由原来装在混合风管道上改为分别安装在热风管道和冷风管道上,利用风门开度信号对风量信号进行修正的解决措施,最后分别指出了新建机组和已运行机组现场安装使用中应注意的问题。     

国产空冷单排管流动和传热性能研究

波状翅片扁平管,即单排管是直接空冷凝汽器的一种基本换热元件。单排管外空气侧的流动和传热性能研究,对于直接空冷凝汽器的优化设计和安全运行具有重要的意义。在不同迎面风速下,对国产空冷单排管空气侧进行三维数值模拟,并对速度场、温度场进行分析和研究,拟合出单排管阻力和传热系数随迎面风速变化的计算公式,为直接空冷系统的优化设计提供帮助。     

氢-空气质子交换膜燃料电池系统建模与分析

根据氢-空气燃料电池系统组成,建立了燃料电池系统数学模型。通过模型计算得出环境条件、电堆温度、空气流量参数对系统效率的影响关系。计算结果表明,除了在高温或高湿条件下,环境条件的改变对系统效率的影响较小;高温或高湿条件有降低系统效率的趋势。电堆温度对燃料电池系统的效率有显著影响。温度从30℃升高到80℃时,系统效率逐渐增加。低负载时,空气流量对系统效率的影响比较显著。流量增大时,系统效率下降,流量超过30SLPS时,效率下降接近于零。     

Steam Condensation from a Moving Steam-Gas Mixture

To date, heat exchange has been studied to the greatest extent for the case of the condensation of pure still and moving steam as well as for the case of condensation from a still steam-gas mixture. There are hardly any papers available wherein a moving steam-gas mixture with a substantial content of noncondensable gases is considered. To investigate this process, an experimental workbench of the working section has been developed, which makes it possible to determine the local values of the heat transfer coefficient from the steam-gas mixture to the walls of cooled heat-exchange tubes at different parameters and velocities of the gas-steam mixture. In the first four rows of tubes of the working section, there is no cooling, and their function consists in a hydraulic stabilization of the flow. In the fifth and the sixth row of tubes, the wall temperature of the cooled heat-exchange tubes is measured for determining the heat transfer coefficients from the moving steam to the tube walls. The seventh row of tubes is also not under cooling. Measuring tubes with temperature sensors have been manufactured that make it possible to obtain the wall temperature for determining the heat transfer coefficient. The adopted scheme of steam motion and the measurement system make it possible to obtain correct results of the heat and mass transfer investigation in the course of steam condensation from a gas-steam mixture with a significant content of noncondensing gases. The studies on steam condensation from a moving steam-gas mixture have been carried out in the range of parameter ρw² = 9.5 ? 66 Pa and at a volume concentration of air in the steam amounting up to ν_air = 0.18. Convective heat transfer coefficient α values for the heat transfer from a moving steam-gas mixture to the wall of a cooling tube were obtained. At small values of parameter ρw² = 9.5 Pa and the volume fraction of the air content ν_air = 0.06 in the steam, the average heat transfer coefficient exhibits a decrease by a factor of two as compared with that inherent in the condensation of almost pure steam. At the values of parameter ρw² = 66 Pa and at ν_air = 0.06, the average heat transfer coefficient decreases by 1.3 times. The studies on almost pure steam are in good agreement with Berman’s dependence.     

竖直细管内高速空气-过冷水环状两相流的蒸发-对流耦合传热特性

通过数值计算研究了竖直细小传热管内高速空气-过冷水非沸腾环状两相流的传热传质特性。计算结果表明：在细小管内壁上过冷水形成非常薄的液膜，壁面热流密度可以分为液膜吸热，液膜蒸发和气相(湿空气)吸热3部分。在管内下部的环状流区域内，液膜蒸发换热是支配性的传热方式，并具有十分强的换热能力。数值计算指出即使在高热流密度条件下管壁温也能保持在较低范围。计算结果较好地预示了过去的实验结果。