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。     

旋流预混燃烧室燃烧特性及排放特性的数值模拟研究

为了综合考察燃气轮机燃烧室在高稳定性、低排放以及燃料适应性等方面的新要求,基于旋流预混燃烧技术,通过三维数值模拟方法开展了甲烷/空气、丙烷/空气预混燃烧特性及排放特性研究。结果表明：在一定的预混气进气质量流量条件下,当量比增大易引发回火,燃烧温度更高,同时NO_x排放指数增大,增加预混气质量流量,可在一定程度上提高回/熄火极限;当量比固定,增加预混气进气质量流量可避免潜在的回火现象,且NO_x排放指数线性降低;旋流器的旋流数增大能形成强旋流,稳定火焰,降低NO_x排放指数,但过大的旋流强度会引发回火现象;相比于甲烷/空气预混燃烧,丙烷/空气预混燃烧温度偏高,NO_x排放指数较大,但回熄火边界更宽,对应更广阔的稳定燃烧区间。     

当量比对微型燃气轮机H2/Air燃烧特性的影响

为了探究氢气微型燃气轮机的燃烧特性,用数值模拟方法分析了6种不同当量比工况下的燃烧室内流场特性、压力损失、燃烧效率、NO_x排放和速度分布等参数。结果表明：当量比对回流区的范围影响不大,压力损失和出口速度随当量比增加逐渐增大,出口温度分布系数（OTDF）、排气温度和NO_x排放随当量比的增加先增大后减小;径向速度的分布关于燃烧室中心轴线对称;当量比小于1时,燃烧效率在99.9%以上;当量比大于1时,燃烧效率随当量比增加而降低;当量比为1时,排气温度达到2 500 K,NO_x排放达到最大值,偏离化学当量比燃烧有利于抑制NO_x的生成。     

微通道内甲烷/氢气/氧气预混合火焰传播特性

在石英玻璃微圆管内,进行甲烷/氢气/氧气预混合火焰传播的实验研究,分析了管径、掺氢比、当量比及入口流速对火焰传播状态和稳定火焰位置的影响规律.结果表明:实验观测到的微火焰主要有管外射流火焰、脉动火焰、稳定火焰与反复熄燃火焰;随着管径增加,稳定火焰出现在更高当量比情况下,火焰位置更靠近燃烧室入口;掺氢比越高,形成稳定火焰对应的当量比越高,火焰位置更接近出口;高当量比时,稳定火焰仅在低入口流速下能够获得,随着当量比降低,火焰能在较高入口流速下稳定;低流速下,稳定火焰在当量比为1.85～1.925时更接近燃烧室入口,随着流速增加,火焰位置更接近出口;反复熄燃火焰在管径增加时对应的当量比维持在1.79～1.93,在掺氢比增加时对应的当量比为1.79～2.12.     

天然气-氢气-空气混合气火焰传播特性研究

在定容燃烧弹内研究了初始条件为常温常压的灭然气-氢气-空气混合气火焰传播规律，得到了不同掺氢比例和燃空当量比下混合气的层流燃烧速率、质量燃烧流量和马克斯坦长度，结合火焰传播照片，分析了火焰的稳定性并预测了大尺寸火焰稳定性的演变趋势。研究结果表明，随着天然气中掺氢比例的增加，混合气的燃烧速率增加，且增长速率逐渐加快，马克斯坦长度值减小，火焰的稳定性下降。各种掺氢比例下，随当量比的增加，马克斯坦长度值增加，火焰的稳定性增加。掺氢比例高于80％时，随着火焰的传播，其不稳定性将明显增加。     

两级浓淡燃烧室内氨-氢-空气预混旋流燃烧过程的NOx排放特性

为了掌握燃气轮机两级浓淡燃烧室内氨-氢-空气预混旋流火焰的NO_x排放特性和影响NO_x生成的动力学机制,对氨-氢-空气预混旋流燃烧过程进行了三维反应流数值模拟并开展了燃烧反应动力学特性研究．结果表明：在掺氢比为35%、压力为0.5 MPa且当量比为1.20的绝热燃烧工况下,NO_x排放可降至54×10^-6(15%O₂).H+O₂(+M)=HO₂(+M)是燃烧压力影响氨-氢燃料燃烧过程中NO_x排放的关键反应．燃烧压力的升高会促进NO与HO₂反应并转化为NO₂．对于氨-氢混合燃料而言,过高的掺氢比(60%～80%)会导致NO_x排放显著升高,而根据壁面热损失程度的不同,适当的掺氢比(35%～55%)则有利于实现较低的NO_x排放(54×10^-6～86×10^-6 (15%O₂...     

天然气-氢气-空气混合气的层流燃烧速度测定

在定容燃烧弹内研究了常温常压下天然气-氢气-空气混合气的火焰传播规律，得到了不同掺氢比例（氢气在天然气中的体积掺混比例为0％～100％）和燃空当量比（0．6～1．4）下混合气的层流燃烧速率和马克斯坦长度，通过对马克斯坦长度的测量，分析了拉伸对火焰传播的影响。结果表明，随着天然气中掺氢比例的增加，混合气的燃烧速率呈指数规律增加，马克斯坦长度值减小，火焰的稳定性下降。各掺氢比例下，随当量比的增加，马克斯坦长度值增加，火焰的稳定性增强。通过对试验结果的数据拟合，得到了计算天然气-氢气-空气混合气层流燃烧速率的关系式。     

高温高压下掺氢天然气的燃烧特性

在定容燃烧弹内研究了高温(450,K)、高压(0.75,MPa)条件下天然气-氢气-空气混合气的火焰传播过程,获得了不同掺氢比和不同当量比下掺氢天然气的无拉伸层流燃烧速率,并分析了火焰的稳定性。结果表明,高温高压下随着掺氢比的增加,掺氢天然气的燃烧速率增加,且增长速率逐渐加快;马克斯坦长度则随着掺氢比的增加而减小,即火焰的稳定性下降。随着当量比的增加,无拉伸层流燃烧速率呈现先增大后减小的趋势,且最大无拉伸层流燃烧速率所对应当量比的位置随着掺氢比的提高而向浓混合气移动;马克斯坦长度随当量比的增加而增大,即火焰稳定性随当量比的增加而提高。     

不同初始压力下掺氢天然气的燃烧特性

在定容燃烧弹内研究了不同初始压力下天然气-氢气-空气混合气的火焰传播规律,得到了不同掺氢比例和初始压力下,不同燃空当量比时混合气的层流燃烧速率,并分析了火焰的稳定性及其影响因素.研究结果表明,随着天然气中掺氢比例的增加,混合气的燃烧速率增加,且增长速率逐渐加快,而马克斯坦长度值则随着掺氢比例的增加而减小,即火焰的稳定性下降.不同初始压力下,随着燃空当量比的增加,马克斯坦长度值在不同掺氢比例下均增加,显示火焰的稳定性增加.无拉伸层流燃烧速率随着初始压力的增加略有减小,且在化学当量比附近,变化的初始压力和掺氢比对无拉伸层流燃烧速率的影响最为明显.     

不同进气氛围耦合废气再循环对双燃料发动机工作过程的影响

基于正庚烷、甲烷、乙烷、丙烷多组分混合物简化动力学机理耦合三维计算流体力学（computational fluid dynamics,CFD）数值模型,模拟研究高替代率时不同进气氛围（H₂、O₂组分）耦合废气再循环（exhaust gas recirculation,EGR）对天然气/柴油双燃料发动机低负荷工作过程的影响机理。研究表明：在不同EGR率下,进气掺氢会使缸内燃烧速率显著加快,OH活性基浓度明显升高,CH₄排放显著降低,但CO排放升高;进气掺氧后,缸压及瞬时放热率峰值、最大压力升高率、最高燃烧温度及OH活性基浓度均升高,碳烟、CO和CH₄后期氧化作用增强使其最终排放降低,但NO_x排放升高。在EGR率小于29%,掺氢比小于2.5%时,在实现较低CO、碳烟排放的同时能显著降低CH₄排放和NO₂/NO_x比例;高EGR率时,进气掺氧能降低CO、碳烟排放,并改善CH₄与NO_x     

旋流对天然气高温空气燃烧特性影响的数值模拟

以工业炉的高温空气燃烧技术应用为背景,对一个新型轴向旋流式单烧嘴燃烧室内天然气的高温空气燃烧特性进行了数值研究。采用数值模拟的方法研究了同心式轴向旋流燃烧器（HCASbumer）中螺旋肋片的旋转角度对燃烧特性的影响,其中湍流采用Reynolds应力模型,气相燃烧模拟采用β函数形式的PDF燃烧模型,采用离散坐标法模拟辐射换热过程,NOx模型为热力型与快速型。计算结果表明,对预热空气采用旋转射流时,能明显降低NOx生成量。对于HCAS型燃烧器,随着空气射流旋转角度的增大,燃烧室内的回流区域增大增强,降低了局部的氧体积分数分布,燃烧室中平均温度和最高温度都有所增加,且燃烬程度大幅度提高,而局部高温区缩小,只在靠近入口处出现。总的NOx排放量随着空气射流旋转角度的增大先减小,后增大。因此,适当调整肋片的旋转角度可以降低NOx生成量。     

Effect of initial pressure,temperature and equivalence ratios on laminar combustion characteristics of hydrogen enriched natural gas

In this study, the flame propagation characteristics of premixed natural gas–hydrogen–air mixtures were studied in constant volume combustion bomb by using the high-speed schlieren photography system. The flame radius, laminar flame propagation speed and the flame stretch rate were obtained under different initial pressure, temperature, equivalence ratios and hydrogen fractions. Meanwhile, the flame stability and their influencing factors were obtained by analyzing the Markstein length and the flame propagation schlieren photos under various combustion conditions. The results show that the stretched laminar propagation speed increases with the increase of the initial temperature and hydrogen fraction of the mixture, and will decreases with the increase of the initial pressure. Meanwhile, according to the Markstein length and the flame propagation pictures, the flame stability decreases with the increase of the temperature and hydrogen fraction, and the slight flaws occurred at the early stage; at larger flame radius, the flame stability is more sensitive to the variation of the initial temperature and hydrogen fraction than to that of initial pressure and equivalence ratio.     

天然气燃料轴向分级预混燃烧特性研究

低NOx排放是燃气轮机燃烧室的重要性能指标,面对燃烧室出口温度不断增加的趋势,新型燃烧技术探索应用成为必然。燃料轴向分级(Axial Fuel Staging,AFS)燃烧作为一项可行技术方案已在各燃机厂商的最先进燃气轮机燃烧室上获得应用,其主要通过降低高温烟气有效停留时间和低氧浓度燃烧来实现低NOx排放。基于Chemkin平台建立轴向分级预混燃烧室化学网络模型,针对1 973 K燃烧室,研究二级负荷比例、当量比和停留时间对NOx/CO排放的影响规律,对比分析主燃区高温烟气与二级未燃预混气掺混特征的影响,获得AFS燃烧的污染物排放特性和关键影响因素。同时,在贫预混燃烧器上,设计二级喷射段,实验研究二级火焰结构、污染物排放等燃烧特性。结果表明,相比于常规贫预混燃烧,AFS燃烧在高温区体现出很好的低NOx优势,且能拓宽低NOx工况范围,其中主燃区温度、二级当量比和停留时间匹配特征、主燃区高温烟气与二级预混气掺混性能等是关键。     

Study of laminar combustion characteristics of gasoline surrogate fuel-hydrogen-air premixed flames

This paper investigated the effects of hydrogen addition to gasoline surrogates fuel-air mixture on the premixed spherical flame laminar combustion characteristics. The experiments were carried out by high speed Schlieren photography on a constant-volume combustion vessel. Combining with nonlinear fitting technique, the variation of flame propagation speed, laminar burning velocity, Markstein length, flame thickness, thermal expansion coefficient and mass burning flux were studied at various equivalence ratios (0.8–1.4) and hydrogen mixing ratios (0%–50%). The results suggested that the nonlinear fitting method had a better agreement with the experimental data in this paper and the flame propagation was strongly effected by stretch at low equivalence ratios. The stretched propagation speed increased with the increase of hydrogen fraction at the same equivalence ratio. For a given hydrogen fraction, Markstein length decreased with the increase of equivalence ratio; flame propagation speed and laminar burning velocity first increased and then decreased with the increase of equivalence ratio while the peaks of the burning velocity shifted toward the richer side with the increase of hydrogen fraction.     

柴油机部分均质预混燃烧模式下混合与化学控制参数对指示热效率的影响

基于部分均质预混燃烧(PPC)的柴油机研究开发和优化了一种混合燃烧控制策略,在平均指示压力(IMEP)高达1.1,MPa的负荷范围内实现了高的指示热效率以及超低排放.燃烧过程中的混合与化学控制参数包括了喷油定时、喷油模式(如多脉冲喷射)、增压压力、EGR率以及进气气门关闭定时等,通过优化耦合以上控制参数可以优化控制当量比与温度的变化路径,从而避开NOx与碳烟(Soot)生成区.基于热力学第一定律,通过能量平衡的分析方法研究了混合与化学控制参数对热效率的影响.研究表明,相对于排放而言,热效率受控制参数的影响更加敏感.     

The synergistic effect of equivalence ratio and initial temperature on laminar flame speed of syngas

The laminar flame speed of syngas (CO:H₂ = 1:1)/air premixed gas in a wide equivalence ratio range (0.6–5) and initial temperature (298–423 K) was studied by Bunsen burner. The results show that the laminar flame speed first increases and then decreases as the equivalence ratio increasing, which is a maximum laminar flame speed at n = 2. The laminar flame speed increases exponentially with the increase of initial temperature. For different equivalent ratios, the initial temperature effects on the laminar flame speed is different. The initial temperature effects for n = 2 (the most violent point of the reaction) is lower than others. It is found that H, O and OH are affected more and more when the equivalence ratio increase. When the equivalence ratio is far from 2, the reaction path changes, and the influence of initial temperature on syngas combustion also changes. The laminar flame speed of syngas is more severely affected by H + O₂ = O + OH and CO + OH = CO₂ + H than others, which sensitivity coefficient is larger and change more greatly than others when the initial temperature and equivalence ratio change. Therefore, the laminar flame speed of syngas/air premixed gas is affected by the initial temperature and equivalence ratio. A new correlation is proposed to predict the laminar flame speed of syngas (CO:H₂ = 1:1)/air premixed gas under the synergistic effect of equivalence ratio and initial temperature (for equivalence ratios of 0.6–5, the initial temperature is 298–423 K).     

Experimental analysis of the effects of hydrogen addition on methane combustion

This paper presents gas emissions from turbulent chemical flow inside a model combustor, for different blending ratios of hydrogen–methane composite fuels. Gas emissions such as CO and O₂ from the combustion reaction were obtained using a gas analyzer. NOx emissions were measured with a NOx analyzer. The previously obtained flame temperature distributions were also presented. As the amount of hydrogen in the mixture increases, more hydrogen is involved in the combustion reaction, and more heat is released, and the higher temperature levels are resulted. The results have shown that the combustion efficiency increases and CO emission decreases when the hydrogen content is increased in blending fuel. It is also shown that the hydrogen–methane blending fuels are efficiently used without any important modification in the natural gas burner. Copyright © 2011 John Wiley & Sons, Ltd.     

Experimental study of propane/air premixed flame dynamics with hydrogen addition in a meso-scale quartz tube

The combustion process of propane/air premixed flame in meso-scale quartz tubes with different hydrogen additions was investigated experimentally to explain the flame-wall interaction mechanism. The ranges of different flame regimes were obtained by changing the flow rates of propane and hydrogen. The effects of hydrogen addition, inlet velocity and equivalence ratio were analyzed. The results show that the hydrogen addition broadens the operation ranges of fast flame regime and slow flame regime significantly. The flame propagation speed is in the same order of the thermal wave speed in solid wall for the slow flames. In fast flame regime, the flame propagation speed has an inverse correlation with the inlet flow velocity irrespective of the equivalence ratio. With the increase of the equivalence ratio, the maximum flame speed in fast flame regime decreases gradually, while the maximum flame speed in slow flame regime increases continually. It indicates that rich fuel condition suppresses the fast flame and promotes the slow flame. In slow flame regime, the output thermal efficiency is dominated by the inlet velocity and equivalence ratio.