燃烧室结构对微燃烧器内甲烷燃烧的影响

为了合理设计微燃烧室,建立了微燃烧室内的湍流燃烧模型,采用Fluent软件对不同结构微燃烧器中甲烷/氧气的燃烧特性进行了数值模拟.甲烷/氧气的当量比为1,混合气流量为200mL/min,入口温度为300K,并比较了不同结构微燃烧室内燃烧情况的差异.计算结果表明,随着燃烧器的长度和宽度增加,燃烧室内的温度升高,甲烷的浓度下降.     

甲烷和氢气在亚毫米微燃烧室内燃烧的试验对比

在碳化硅材料的亚毫米尺度微燃烧室内,针对甲烷和氢气两种不同燃料进行了燃料与氧气预混合燃烧的试验。利用热电偶测出燃烧室壁面温度并进行了分析。结果表明:在燃料和氧气的总体积流量相同时,燃用甲烷时燃烧室的壁面平均温度更高,但氢气的燃烧室壁面温度更加均匀,梯度更小;氢气比甲烷有更宽的可燃范围,试验时甲烷/氧气在总体积流量为700mL/min、混合比为化学当量比时燃烧不能进行,而氢气和氧气在相同条件下能够燃烧。     

Swiss-roll型微燃烧器的燃烧数值模拟

建立了Swiss-roll型微燃烧器的燃烧模型,采用FLUENT软件对微燃烧器中甲烷/空气的燃烧特性进行了数值模拟,研究了甲烷/氧气的当量比为1时流速不同对微燃烧器内燃烧的影响。计算结果表明,Swiss-roll型微燃烧器有利于甲烷在微燃烧室内的充分燃烧。     

微通道壁面加热对甲烷空气预混火焰传播特性的影响

对于甲烷和空气预混合气在矩形微燃烧室内的燃烧过程,采用加热片加热,对比分析了在外部加热时,有无隔板对燃烧稳定性的影响,并分析了不同加热温度下隔板式燃烧室内火焰传播特性。实验结果表示,随着加热温度的提升,隔板型燃烧室稳定燃烧区域不断增大；加热温度高于600K,隔板型燃烧室的火焰吹熄极限有明显改善；高温加热利于提高隔板型燃烧室在较大流量情况下燃烧的稳定性。相较于单通道燃烧室,外部加热对隔板型燃烧室燃烧稳定性的改善更加明显。     

微型动力装置燃烧过程及做功能力评价

为研究微型动力装置燃烧室内燃烧特性及动力性能,对微燃烧室内燃烧过程进行可视化试验,分析了微燃烧过程中混合气的燃烧特性及不同自由活塞初速度对微燃烧室内压力及做功能力的影响.结果表明:二甲醚/氧气混合气体在微均质充量压缩着火(HCCI)燃烧过程中存在两阶段着火特性,随着自由活塞初速度的增加,微燃烧室内峰值压力增加,压力升高率峰值增大,平均指示压力增大,指示热效率提高.当微燃烧室直径为3,mm、体积为0.26,cm3、自由活塞初速度为22.5,m/s和平均指示压力为3.4,MPa时,微型动力装置可产生70,W的功率,功率密度为269,MW/m3,具有较大功率密度优势.     

微尺度条件下反复熄燃火焰特性的实验研究

在可视化微尺度燃烧实验台上进行甲烷和氧气的燃烧试验,利用高速数码照相机捕捉到了火焰面在微通道内的传播过程,测试分析了不同进气流量下反复熄燃火焰的可燃极限、火焰传播速度和火焰间隔时间,获得了反复熄燃火焰(Flames with repetitive extinction and ignition, FREI)的燃烧特性。结果表明,随着甲烷进气流速的增加,可以形成FREI火焰的氧气进气流速范围也在扩大;在甲烷进气流速一定的情况下,随着氧气进气流速的增加,火焰的传播速度也逐渐增加,并且火焰重复点燃的间隔时间呈现先变大后逐渐变小的规律,即火焰重复点燃的频率先变慢后又逐渐变快直至火焰熄灭。     

CO_2掺混比对甲烷HCCI燃烧特性的影响

基于微型均质充量压燃(HCCI)自由活塞动力装置内自由活塞单次冲击过程,通过试验与数值模拟的方法,对比分析了甲烷掺混不同比例的CO_2时,混合气着火时刻、微燃烧室内的温度、压力以及装置做功能力的变化.结果表明:在初始当量比为0.5时,甲烷中CO_2的掺混使混合气着火时刻延迟、燃烧速率变慢,微燃烧室内的压力与温度峰值后移且降低,混合气体的爆燃现象得到改善.随着甲烷中CO_2掺混比的增加,混合气的着火与燃烧不断恶化,装置的做功能力不断减弱,同时装置所需的启动能量不断增加;当CO_2掺混比达到40%时,自由活塞的速度增量减少2.67 m/s,平均有效指示压力减少0.584 MPa,同时装置所需的启动能量增加至0.182 4 J.当CO_2掺混比达到58%时,混合气无法被压燃,微动力装置不对外做功.在保证装置做功能力的基础上,甲烷掺混一定比例的CO_2,微燃烧室内平均温度能够降低30～100 K,微动力装置可以降低对微燃烧室材料的依赖,实现低温燃烧.     

材料和喷口直径对多孔介质微燃烧的影响

为了进一步优化微燃烧室的设计,以最大化提高微燃烧室的能量转换效率及微热光电系统的整体工作效率,在前期工作的基础上设计了不同多孔介质材料及喷嘴/燃烧室内径比的多孔介质微燃烧室.通过实验验证,针对多孔介质微燃烧室内的氢氧预混燃烧进行了数值模拟计算,研究结果表明,多孔介质材料,喷嘴/燃烧室内径比对微燃烧室内的微尺度燃烧有重要影响,微燃烧室在多孔介质材料为SiC, 喷嘴/燃烧室内径比为0.27时燃烧效率最高,有利于提高微热光电系统的整体效率.     

喷嘴与安装孔之间的缝隙对微型燃气轮机燃烧室影响的数值分析

为了探究喷嘴与燃烧室壁面安装孔间的缝隙对微型燃气轮机燃烧室流动及燃烧特性的影响,运用三维数值计算软件,对30 kW微型燃气轮机燃烧室在不同面积缝隙下的燃烧过程进行了数值计算,得到了燃烧室内的流场及温度场,并对比分析了燃烧室各处的气体流量分配、燃烧室内部温度分布以及污染物排放量。计算结果表明:缝隙面积的变化对燃烧室内气量分配的影响是全局性的,随着缝隙面积的增大,缝隙内的气体流量增加,燃烧室其它各处的流量则相应减小。在贫燃的条件下,这一过程使得燃烧室内部的整体温度逐渐减低,随之C0的排放量小幅增大。此外,一定范围内的缝隙能够在降低燃烧室整体温度的同时维持火焰形态,有效降低NOx的排放量。     

甲烷_空气在微小型Swiss_roll燃烧器内燃烧的实验研究

为了解微小型Swiss-roll燃烧室的工作特点,进行了甲烷/空气预混气的燃烧实验,获得了燃烧器的可燃极限,研究了回热对燃烧器可燃极限的影响.结果表明,当甲烷流量在O.8～2.7mg/s之间时,所设计的微燃烧器能够实现cH4/空气的稳定燃烧,并确保火焰位于燃烧器的中心.存在回热时,燃烧器的富氧极限减小,从没有回热时的0.7减小到O.5.但是可燃极限并不关于ER=1对称,富燃极限大,而富氧极限小.同时,对微燃烧器进行了数值模拟,结果表明,燃烧器中心的回流区使燃烧器能够在较大的可燃极限范围内稳定工作.     

Numerical investigation of combustion characteristics for hydrogen mixed fuel in a can-type model of the gas turbine combustor

Numerical simulations are performed to analyze the combustion characteristics of propane fuel mixed with different amounts of hydrogen in a can-type combustor. The volume fraction of the hydrogen fuel varies from 0% to 100% in the fuel mixture. The results indicate that the hydrogen enrichment of the fuel significantly affects the flow structure, mixture fraction, and combustion characteristics. An increase in the volume fraction of hydrogen significantly affects the mean mixture fraction distribution, promotes combustion, and increases the flame temperature and the width of the flammable range within the combustor. Therefore, the degree of temperature uniformity at the outlet of the combustor increases with hydrogen enrichment, corresponding to an increase of 49.64% in the uniformity factor. The hydrogen enriched fuel can also reduce the emissions of CO and CO₂, owing to the reduced amount of carbonaceous fuel.     

微型燃气轮机改烧氨气/氢气混合燃料的数值模拟研究

通过数值模拟对某80 kW微型燃气轮机环形低氮燃烧室进行适当的改造并对其燃烧及NO_x生成特性进行研究。研究结果表明：将烧天然气燃料的燃烧室改烧氨/氢混合燃料,在输出功率相同时燃料体积流量增大,通过增加燃料进气喷嘴的直径来降低燃料的进气速度;当掺氢比为0.3时,该结构的燃烧室燃烧不充分,燃烧效率达不到要求;当掺氢比在0.35～0.5、燃料华白数在19.9～21.7范围内变化时,该燃烧室可以实现高效稳定的燃烧,性能接近燃烧天然气燃料;氨/氢混合燃料中掺氢比增大,则NO_x排放量也快速增大;由于燃料型NO_x排放量占主导地位,该微型燃气轮机燃烧室不能实现低NO_x燃烧,NO_x排放远超国家标准,需要加装脱硝装置才能实际应用。     

Numerical analysis of the combustion characteristics of graphitic hydrogen-chlorine synthesis combustor with different intake strategies

This study investigates the effect of intake strategies on the combustion and flows characteristics of hydrogen-chlorine synthesis combustors via numerical methods. A crucial issue of hydrogen-chlorine synthesis combustor is to have a sufficiently low flame height and high conversion efficiency. In this study, the combustion performance of combustors equipped with the annular tube, plum nozzle, and porous-bullet nozzle has been thoroughly analyzed. The temperature distribution and gas flow are analyzed using the method of fluid-solid coupling, which indicates that the combustor with porous-bullet nozzle had the best gas distribution, the maximum HCl mole fraction at outlet is 97.24%, and the lowest flame height is 3.4 m, which is 27.15% lower than the combustor with the annular tube. Furthermore, the nozzle structure has a great influence on the fluid velocity in the recirculation zone of the combustor. Finally, the effect of hydrogen/chlorine equivalence ratio (?) and inlet volume flow rate were analyzed, and it can be concluded that with the increase of inlet volume flow, the high-temperature area inside the combustor gradually increases. As the equivalent ratio increases, the combustor outlet's mole fraction changes with a normal distribution trend. It is the most appropriate when the chlorine gas flow rate is 1,100 m³/h and ? = 1.05. The research can be applied to the field of high-purity hydrogen chlorine production, providing researchers with some solutions.     

生物质链条炉床层燃烧建模及一次风影响分析

基于多孔介质非热平衡的方法,考虑了床层高度的变化及颗粒内部温度梯度的影响,建立了一维非稳态燃烧模型来模拟炉排上移动床层的生物质燃烧。模拟计算结果与实验值对比分析表明,总体上数值计算结果与实验数据吻合较好。通过对不同一次风参数下床层燃烧的模拟结果分析得到,随着一次风风量的增加,床层剩余质量先减小后增大;在燃烧前期,床层出口气体温度上升速度减慢,挥发分析出速率降低,焦炭燃烧速率增大;在燃烧中期,床层出口气体温度先上升后下降,焦炭燃烧速率下降。一次风风温相比于一次风风量对床层燃烧影响较小,增大一次风风温可以提高挥发分析出速率,降低床层出口气体温度和床层剩余质量。     

增压富氧燃煤锅炉省煤器的设计与优化

以300MW机组煤粉炉省煤器为例,对锅炉常压空气燃烧、常压富氧燃烧和5种不同增压(6MPa)富氧燃烧方案下的锅炉对流受热面尺寸、烟气流量、烟气侧传热系数和压降等参数进行了计算和分析,根据基于经济性分析的单位换热量换热器总费用最小的原则确定省煤器的最佳设计结构.结果表明:与常压空气燃烧相比,常压富氧燃烧下烟气体积流量减小了28.5%,对流传热系数减小了11.5%;增压富氧燃烧下的烟气体积流量减小了98.82%,随着烟气流速的增大,受热面面积减小,烟气侧传热系数和压降增大;最佳方案中的烟气流速为1.54m/s时,单位换热量换热器总费用约为常压空气燃烧下的60%,烟气侧压降为582.65Pa,烟道截面积仅为常压空气燃烧下的7.8%.     

An experiment on the effect of oxygen content and air velocity on soot formation in acetylene laminar diffusion flame produced in a burner with a parallel annular coaxial oxidizer flow

The effect of oxygen content and of the combustion air velocity on soot formation was studied in acetylene diffusion flames. These flames were produced in a burner with a parallel annular coaxial flow of oxidizer. The effect on the flame axial temperature profile was also evaluated. The soot volume fraction was calculated by the laser light extinction methodology. The oxygen content in the combustion air was smaller than 30%, which does not require significant retrofit of existent equipment when the combustion conditions are varied. The results suggest that the parallel manipulation of the oxygen content and of the oxidizer velocity can provide means for managing soot formation and distribution. The formation of soot in industrial combustion systems is of interest in engineering, because the presence of soot in the flame enhances the heat transfer from the combustion gases by thermal radiation, increases the need for burner maintenance, and constitutes an environmental problem when emitted in the atmosphere.     

Effect of different volume fractions of ammonia on the combustion and emission characteristics of the hydrogen-fueled engine

Hydrogen internal combustion engines (ICE) will play an important role in reducing carbon emissions, but low power density and abnormal combustion problems are the main obstacles restricting the promotion of hydrogen ICE. Ammonia is a low-reactivity renewable fuel. The purpose of this study is to study the effect of different ammonia-added volume fractions on hydrogen ICE. In this experimental study, the combustion and emission characteristics of an engine fueled by a hydrogen/ammonia mixture were evaluated at part-load operating conditions. The experiment was carried out on a modified engine, the engine speed was 1300 rpm, the absolute pressure of the manifold was 61 kPa, and the volume fraction of ammonia added was 5.2%, 7.96%, and 10.68%, respectively. The test results show that the addition of ammonia changes the combustion characteristics of hydrogen. As the volume fraction of ammonia added increases, the flame development period and flame propagation period are both prolonged, and the peak heat release rate decreases. The addition of ammonia increases the power of the engine and reduces the indicated thermal efficiency. At the ignition timing of the maximum braking torque, as the volume fraction of ammonia added increases, the indicated mean effective pressure and indicated thermal efficiency increase. Adding ammonia volume fraction has little effect on Nitrogen oxides (NOx) emissions, and NOx emissions gradually increase with the delay of ignition timing.     

切向叶片角度对中心给粉旋流燃烧器气固流动特性影响

利用三维激光多普勒测速仪,在气固两相实验台上,对不同切向叶片角度下中心给粉旋流燃烧器出口区域的气固流动特性进行了研究,获得了三种切向叶片角度下的三维平均速度和颗粒体积浓度的分布。结果显示,随着切向叶片角度的减小,轴向、径向和切向平均速度峰值都增加,回流区尺寸和旋流数也增大。同时,在x/d=0.1～0.7截面,随着切向叶片角度的减小,在燃烧器中心区域的颗粒体积流量峰值增加。     

Pre-chamber turbulent jet ignition of methane/air mixtures with multiple orifices in a large bore constant volume chamber: effect of air-fuel equivalence ratio and pre-mixed pressure

Liquefied natural gas (LNG), mainly composed of methane, is in progress to substitute diesel fuel in heavy-duty marine engine for practical, economic, and environmental considerations. However, natural gas is relatively difficult to be ignited in a large bore combustion chamber. A combustion enhancement technique called pre-chamber turbulent jet ignition (TJI) can permit combustion and flame propagation in a large-bore volume. To investigate the effect of air-fuel equivalence ratio and pre-mixed pressure on pre-chamber TJI of methane/air mixtures with multiple orifices in a large bore volume, experimental tests and computational simulations were implemented to study the discharge of hot turbulent jets from six orifices of the pre-chamber. Different initial pressures and air-fuel equivalence ratios were considered to analyze the characteristics of TJI. The asymmetry of the turbulent jet actuated from six different orifices were found due to the asymmetric orientation of the spark plug, resulting in the inhomogeneous distribution of combustion in the constant volume chamber, which should be considered seriously in the marine engine design. Besides, as the premixed pressure increases, it has more effect on the flame propagation and plays a more important role, as it further increases.     

柴油温度对燃烧火焰温度和碳烟生成的影响

通过定容燃烧弹,采用双色法研究不同柴油温度对冷起动过程中燃烧火焰温度和碳烟生成特性的影响,获取缸内燃烧火焰温度分布和表征碳烟分布的KL因子.结果表明:在喷油后3.5 ～ 6.0 ms的燃烧稳定时期,柴油温度为40℃的火焰中大于2 200 K的区域约占60％,柴油温度为20℃的火焰中大于2 200 K的区域约占55％,柴...