燃用超低热值燃气的旋转回热型催化燃烧器数值分析

针对超低热值燃气难以点火燃烧而直接排入大气,导致环境污染和能源浪费的问题,提出了一种以超低热值燃气为燃料的反应器,即旋转回热型催化燃烧器.根据其周期性旋转、蓄热、放热和催化燃烧等特点,采用计算流体力学(CFD)软件进行模拟分析.结果表明:该反应器能有效氧化超低热值燃气(甲烷体积分数2%、入口速度20m/s),持续生成1 035~1 200K的高温燃气,从理论上证明了该反应器的可行性;在旋转周期的状态I(或II)内,燃气和烟气出口温度均近似线性升高,该规律可用于评估反应器的热力性能;反应器周期性旋转,使壁面温度峰值在1 200~1 600K变化,有利于催化燃烧发生,同时也避免了反应器中热量聚集和催化剂高温失活.     

氢气对超低体积分数甲烷催化燃烧的影响

搭建了催化燃烧实验台,在保证催化燃烧室入口气体温度、流速相同的情况下,通过改变气体中甲烷和氢气的体积分数,得到不同体积分数甲烷气体在加入不同体积分数氢气情况下的催化燃烧特性.结果表明:在保证催化燃烧时入口气体温度为520℃条件下,加入低体积分数的氢气可有效加快甲烷催化燃烧的反应速度,降低甲烷的起燃温度,提高甲烷转化率;加入的氢气体积分数越高,对甲烷的催化燃烧助燃效果越好;而甲烷体积分数越高,氢气对甲烷的催化燃烧效果也越显著.     

超低热值燃气微型燃气轮机试验研究

介绍了一种新型的超低热值燃气轮机系统,并对其成功地进行了磨合、自循环不带负荷、自循环带负荷、启动试验和新型催化燃烧试验.结果表明:燃机系统能够满足发出功率的要求;在整个运行范围内轴系振动情况满足设计值的要求;控制催化燃烧室的入口燃气成分、温度和压力能够显著地提高燃料的利用效率.     

生物质熔融碳酸盐燃料电池排气催化燃烧实验研究

在自行研制的催化燃烧实验平台上,研究使用4种不同催化剂的生物质熔融碳酸盐燃料电池排气的催化燃烧反应特性,结果表明:总体趋势上,催化燃烧的反应效率随着催化燃烧室入口温度的提升而提高;生物质气高温燃料电池排气中氢气的体积浓度对催化反应特性有很大影响,在氢气浓度低于3%的时候,催化燃烧反应效率随着氮气浓度的提高而明显增加;不...     

微型燃气轮机低热值燃料燃烧室喷嘴流动实验研究

为适应生物质气低热值、组分变化大的特点,达到燃烧室燃烧稳定、低排放要求,在某60 kW级微型燃气轮机环形燃烧室结构的基础上,新设计了一种具有不同预混孔结构的新喷嘴,并在上海交通大学微型燃气轮机单喷嘴燃烧室实验台上对原喷嘴及新设计喷嘴进行冷态流动实验,对比分析不同稀释孔直径及工质参数条件下原喷嘴及新喷嘴对燃烧室空气流量分配比及过量空气系数的影响。研究表明:燃料流量、空气流量变化会影响燃烧室空气流量分配,空气温度变化对燃烧室空气流量分配无影响;燃料热值降低会导致燃烧室过量空气系数增大,需要匹配直径更大的燃烧室稀释孔;相比于原喷嘴新喷嘴的流量分配比较大,为使其适应低热值燃料,需要匹配的燃烧室稀释孔直径为11.0 mm,该条件下新喷嘴可适应CH_4摩尔分数为50%~90%的燃料。     

超低热值燃气燃烧及CO排放控制研究

针对超低热值燃气燃烧CO排放高的问题,设计开发了同心套筒多孔介质燃烧系统,分别研究了过量空气系数、水蒸气和氧气对以CO为单一可燃气体的超低热值燃气的燃烧特性及污染物排放的影响。结果表明:在预热阶段,内部点火相比较于外部点火能够减少1/3的预热时间;热值为3.0 MJ/m~3的超低热值气体在增大过量空气系数时,能够有效降低CO排放,而2.5和2.0 MJ/m~3的超低热值燃气没有效果;空气系数为1.00的条件下,通过添加质量分数为2%～4%的水蒸气未能降低CO排放;在超低热值燃气中通入氧气可以有效降低CO排放,空气系数为1.00时,在3.0 MJ/m~3的超低热值燃气中添加质量分数为12%的氧气,CO排放最低能降到体积分数53×10~(-6)。     

预混燃烧下环境温度对某型燃气轮机燃烧稳定性和NOx排放影响的 数值研究

环境温度通过改变燃烧室入口空气温度进而影响燃气轮机燃烧稳定性和NO_x排放。为了掌握预混燃烧模式下环境温度对燃气轮机燃烧稳定性和NO_x排放的影响规律,本文以某重型燃气轮机燃烧室为研究对象,采用SAS湍流模型和涡耗散概念燃烧模型,通过改变环境温度,对多旋流喷嘴燃烧室预混燃烧模式下燃烧稳定性和NO_x排放进行了数值计算。研究结果表明:在燃气轮机预混燃烧模式下,提升燃气轮机环境温度,有利于提高燃烧室燃烧稳定性;环境温度从0℃上升到30℃,在不调整燃料和空气流量的情况下,燃烧室出口NO_x排放质量分数增加97.8%。     

9E燃气轮机LEC-Ⅲ燃烧室预混模式的数值计算

采用数值模拟方法对LEC-III燃烧室的燃烧流场进行数值模拟,分析了预混模式下火焰筒内速度分布、温度分布和组分分布.结果表明:在预混模式下,火焰筒通过二级燃料喷嘴旋流器和中心体旋流器形成回流来稳定火焰;中心体旋流器控制了火焰范围,这对组织二级燃烧区的火焰燃烧非常重要;随着吹扫空气质量流量的增加,NO体积分数逐渐减小;模拟计算得出的NO体积分数与试验值接近,且两者的变化趋势一致.     

燃气-蒸汽联合循环的低热值燃料热经济性分析

由于低热值气体燃料中含有大量惰性气体,可燃成分少,发热量低,燃料的体积流量大,因而在燃用低热值气体燃料时,燃气-蒸汽联合循环的特性也发生了变化.分析了压缩比、燃气初温、不同燃料成分对联合循环发电装置热效率的影响;阐述了不同燃料成分时压缩燃料耗功的变化,以及对燃气-蒸汽联合循环装置热效率的影响.对比分析了燃气-蒸汽联合循环与蒸汽循环装置的经济性.     

中低热值燃料对燃气轮机运行特性的影响分析

中低热值燃料燃气轮机对经济发展和节能减排具有重要的意义,对其燃烧特性和运行工况的研究是本项技术的关键问题。本文根据燃气轮机压气机特性曲线、涡轮特性曲线和热力循环过程,分析计算中低热值燃料燃气的热力性质,提出了适用于不同组分的中低热值燃料的膨胀做功计算方法。通过对燃用天然气和合成气进行模拟计算,得到燃料热值对燃料系数、涡轮出口温度、燃料流量及膨胀功的影响规律,为燃气轮机的设计和工况调整提供理论依据。     

Experimental investigation of dynamic and emission characteristics of a DLE gas turbine combustor

The DLE (dry low emission) technology has already been used on industrial gas turbine combustor and the NO X emission can be limited to 25 ppmv (@15% O 2 ), but one of the destructive effects is combustion instability. In this paper, the dynamic and emission characteristics of a DLE gas turbine combustor have been researched in the authors’ laboratory, and the results show that the key source of combustion instability is the non-uniformity of fuel in the flame zone. Two main fuel supply methods have been used to form different fuel distribution types; it is shown that in the perfectly premixed case the emission level is low and combustion process is stable. The PPF also has an obvious effect on the combustor’s emission and dynamic characteristics.     

Combustion characteristics of a lean premixed LPG–air combustor

Fuel/air mixing effects in a premixer have been examined to investigate the combustion characteristics, such as the emission of NO_x and CO, under simulated lean premixed gas turbine combustor conditions at normal and elevated pressures of up to 3.5 bar with air preheat temperature of 450 K. The results obtained have been compared with a diffusion flame type gas turbine combustor for emission characteristics. The results show that the NO_x emission is profoundly affected by the mixing between fuel and air in the combustor. NO_x emission is lowered by supplying uniform fuel/air gas mixture to the combustor and the NO_x emission reduces with decrease in residence time of the hot gases in the combustor. The NO_x emission level of the lean premixed combustor is a strong function of equivalence ratio and the dependency is smaller for a traditional diffusion flame combustor under the examined experimental conditions. Furthermore, the recirculation flow, affected by dome angle of combustor, reduces the high temperature reaction zone or hot spot in the combustor, thus reducing the NO_x emission levels.     

Study of flow and combustion characteristics of optimized low swirl premixed nozzle for micro gas turbine

With the micro gas turbine is used more and more widely, the operating conditions become complex and fluctuating which impacts the environmental friendliness of combustor. In this work, a low swirl premixed nozzle (LSPN) is designed based on the original premixed nozzle (OPN) of a 60 kW micro gas turbine, in order to adapt the flexibility of load and operating environment by improving the mixing performance of fuel and air. The flow and combustion characteristics of LSPN and OPN fed by natural gas is numerically studied using the standard k-ε model and the combined Finite Rate Chemistry/Eddy Dissipation Model (FRC/EDM) under various operating conditions. The results show that the mixing performance of air and fuel in LSPN has been improved. The flow unmixedness in LSPN is always smaller than OPN, and it is 41.74% lower at the outlet of the nozzle. While the equivalence ratio decreases, the mean temperature in the combustor decline. Furthermore, under the majority of operating conditions, the emission performance of LSPN is better than OPN.     

Investigation of reverse flow distributed combustion for gas turbine application

In this paper reverse flow modes of colorless distributed combustion (CDC) have been investigated for application to gas turbine combustors. Rapid mixing between the injected fuel and hot oxidizer has been carefully explored for spontaneous ignition of the mixture to achieve distributed combustion reactions. Distributed reactions can be achieved in premixed, partially premixed or non-premixed modes of combustor operation with sufficient entrainment of burned gases and faster turbulent mixing between the reactants. In the present investigation reverse flow modes consisting of three configurations at thermal intensity of 28 MW/m³-atm and five configurations at thermal intensity of 57 MW/m³-atm have been investigated and these high thermal loadings represent characteristic gas turbine combustion conditions. In all the configurations the air injection port is positioned at the combustor exit end, whereas the location of fuel injection ports is changed to give different configurations. The results are presented on the exhaust emissions and radical emissions using experiments, and evaluation of flowfield using numerical simulations. Ultra-low NO_x emissions were found for both the premixed and non-premixed combustion modes investigated here. Cross-flow configuration, wherein the fuel is injected at high velocity cross stream to the air jet resulted in characteristics closest to premixed combustion mode. Change in fuel injection location resulted in changing the combustion characteristics from closer to diffusion mode to distributed regime. This feature is beneficial for part load operation where higher stability limit is desirable.     

Swirling distributed combustion for clean energy conversion in gas turbine applications

Distributed combustion provides significant performance improvement of gas turbine combustors. Key features of distributed combustion includes uniform thermal field in the entire combustion chamber, thus avoiding hot-spot regions that promote NO_x emissions (from thermal NO_x) and significantly improved pattern factor. Rapid mixing between the injected fuel and hot oxidizer has been carefully explored for spontaneous ignition of the mixture to achieve distributed combustion reactions. Distributed reactions can be achieved in premixed, partially premixed or non-premixed modes of combustor operation with sufficient entrainment of hot and active species present in the flame and their rapid turbulent mixing with the reactants. Distributed combustion with swirl is investigated here for our quest to explore the beneficial aspects of such flows on clean combustion in simulated gas turbine combustion conditions. The goal is to develop high intensity combustor with ultra low emissions of NO and CO, and much improved pattern factor. Experimental results are reported from a cylindrical geometry combustor with different modes of fuel injection and gas exit stream location in the combustor. In all the configurations, air was injected tangentially to impart swirl to the flow inside the combustor. Ultra-low NO_x emissions were found for both the premixed and non-premixed combustion modes for the geometries investigated here. Swirling flow configuration, wherein the product gas exits axially resulted in characteristics closest to premixed combustion mode. Change in fuel injection location resulted in changing the combustion characteristics from traditional diffusion mode to distributed combustion regime. Results showed very low levels of NO (∼3 PPM) and CO (∼70 PPM) emissions even at rather high equivalence ratio of 0.7 at a high heat release intensity of 36 MW/m³-atm with non-premixed mode of combustion. Results are also reported on lean stability limit and OH^* chemiluminescence under both premixed and non-premixed conditions for determining the extent of distribution combustion conditions.     

Experimental and numerical analysis of effect of fuel line length on combustion instability for H2/CH4 gas turbine combustor

This study primarily aims to investigate the effects of fuel line length on the combustion instability characteristics of a partially premixed system. The key characteristics of combustion instabilities are analyzed in a H₂/CH₄ fueled laboratory scaled model gas turbine combustor with a different fuel line length via dynamic pressure measurement, continuous wavelet transform, proper orthogonal decomposition, Rayleigh criterion analysis, and a numerical approach using a three-dimensional Helmholtz solver. It is discovered that the instability characteristics change with the fuel line length. In particular, when the resonance in the fuel line appears at frequencies similar to those of the various resonance modes in the combustion chamber, the corresponding resonance modes amplify each other, causing intense instability as those frequencies. Therefore, the acoustics of the fuel line or the geometry of the pre-chamber can be an important design parameter that affects the main characteristics of combustion instability in partially premixed combustion.     

多流体模型在燃气轮机燃烧室三维反应流中的应用

对一种模型燃气轮机燃烧室中的三维反应流进行了数值模拟，模型燃烧室的燃料是CH4，燃烧类型是预混燃烧，在数值模拟过程中，采用了Spalding于1995年提出来的多流体模型来对燃烧室中的湍流预混燃烧进行了数值模拟，在数值模拟过程中考虑了辐射问题，采用了六通量辐射模型。通过数值模拟给出了速度，压力，湍流脉动动能，湍流动能耗散率，焓值，湍流粘度，温度，密度，燃烧产物质量分数，氧的质量分数，燃料/空气混合比，燃料质量分数，空间三个方向的辐射热通量以及各种流体的质量分数等变量的分布情况，此外，还采用传统的旋涡破碎模型对此燃烧室进行了数值模拟，并对两种方法的结果进行了分析比较，由分析可以看出多流体模型的结果接近于实际情况，对模型燃烧室进行三维反应流数值模拟的工作为今后对实际燃烧室反应流的数值模拟打下了一定的基础。     

氢混天然气燃气轮机加湿低氮燃烧性能研究

为了解贫预混燃烧室天然气掺氢加湿燃烧时的性能变化和容许加湿范围,解决氢混燃气轮机NO_x排放超标问题,以某燃气轮机燃烧室为研究对象,数值研究了掺氢比和加湿比对燃烧性能及污染物排放特性的影响。结果表明：燃料无加湿条件下,燃烧室出口CO和CO₂排放值随着掺氢比的增加而减小,较高燃烧温度将导致热力型NO_x排放值增加,掺氢比达到0.2以上时,NO_x排放已超出环保限值;燃料加湿条件下,随着加湿程度增加,燃气出口平均流速及水蒸气组分含量均增加,燃烧筒内全局温度、CO₂和NO_x排放值均降低,CO排放值先降低后增加;掺氢天然气加湿可实现低氮燃烧,考虑到低掺氢工况燃气轮机功率输出效能和高掺氢工况燃烧性能恶化问题,水蒸气加湿量不宜过多,当掺氢比为0.3时,推荐燃料加湿比为0.463。     

The effect of premixed stratification on the wave dynamics of a rotating detonation combustor

Typical injection schemes of rotating detonation combustors inject fuel locally into the combustion channel, creating stratified fuel-rich and fuel-lean mixing regions. In this study, premixed hydrogen and air rotating detonations are explored in a rotating detonation combustor through premixing part of the fuel into the oxidizer flow. The objective is to investigate the effect of premixing on the operation of the combustor. Three premixing schemes are examined where the detonation wave speeds are analyzed. The results show that in premixing, the fuel-lean regions became more favorable for continuous detonation propagation when premixed with the bypass fuel, resulting in higher detonation wave speeds. This phenomenon is shown to be independent of the global fuel-air equivalence ratio and the amount of fuel premixed into the oxidizer. As such, combustor performance and the operational regime could be improved with lean hydrogen premixing amounts in the main flow oxidizer.