Application of a Central Composite Design for the Study of NOx Emission Performance of a Low NOx Burner
Application of a Central Composite Design for the Study of NOx Emission Performance of a Low NOx Burner
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DOI：
10.3390/en8053606
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发表时间：
2015-05-01
期刊：
影响因子：
3.2
通讯作者：
Lovas, Terese
中科院分区：
文献类型：
--
作者：
Dutka, Marcin;Ditaranto, Mario;Lovas, Terese
在这项研究中，各种因素对低NOx燃烧器的氮氧化物（NOx）排放的影响进行了研究，使用中心组合设计（CCD）的方法，以显示实验设计方法的燃烧领域的适用性的实验矩阵。分析了四个因素对NOx生成的影响：燃料中的氢含量（富氢甲烷中的质量分数为0%~ 15%）、过量空气量（5%~ 30%）、燃烧器头部位置（距燃烧器喉部20-25 mm）和提供给燃烧器的二次燃料含量（0%~ 6%）。测量在等于25 kW的恒定热负荷下进行（基于较低的热值计算）。采用响应面法和CCD建立了燃烧器NOx排放的二次多项式回归模型。使用方差分析和考虑模型方程的系数，评价了测试因子在其各自范围内的显著性。结果表明，氢气除了甲烷导致增加的NOx排放量相比，从纯甲烷燃烧的排放。在所有测试的因素中，燃料中的氢含量是影响NOx排放的最强因素。当燃烧器由纯甲烷作为燃料时，观察到由于过量空气的增加而形成的较低的NOx，但是对于富氢燃料混合物，这种效果减小。NOx排放量略有减少时，燃烧器头被转移到更接近燃烧器外管，而提供给燃烧器的二次燃料流被发现在调查的因素范围内对NOx排放量没有影响。
In this study, the influence of various factors on nitrogen oxides (NOx) emissions of a low NOx burner is investigated using a central composite design (CCD) approach to an experimental matrix in order to show the applicability of design of experiments methodology to the combustion field. Four factors have been analyzed in terms of their impact on NOx formation: hydrogen fraction in the fuel (0%-15% mass fraction in hydrogen-enriched methane), amount of excess air (5%-30%), burner head position (20-25 mm from the burner throat) and secondary fuel fraction provided to the burner (0%-6%). The measurements were performed at a constant thermal load equal to 25 kW (calculated based on lower heating value). Response surface methodology and CCD were used to develop a second-degree polynomial regression model of the burner NOx emissions. The significance of the tested factors over their respective ranges has been evaluated using the analysis of variance and by the consideration of the coefficients of the model equation. Results show that hydrogen addition to methane leads to increased NOx emissions in comparison to emissions from pure methane combustion. Hydrogen content in a fuel is the strongest factor affecting NOx emissions among all the factors tested. Lower NOx formation because of increased excess air was observed when the burner was fuelled by pure methane, but this effect diminished for hydrogen-rich fuel mixtures. NOx emissions were slightly reduced when the burner head was shifted closer to the burner outer tube, whereas a secondary fuel stream provided to the burner was found to have no impact on NOx emissions over the investigated range of factors.