Simplification and applicability studies of a hydrogen-air detailed reaction mechanism

The research of hydrogen fuel internal combustion engine (HICE) had great significance facing the challenges of energy and environmental problems. Based on the detailed hydrogen-air reaction mechanism, the pre-mix model of CHEMKIN-Pro software was selected to simplify the detailed mechanism GRI-3.0. The most important elements and reactions was chose to construct framework mechanism firstly based on the sensitivity coefficient for H₂O and NO formation, and additional elements and reactions were added to framework mechanism for complementing the oxidation path of N2 and H₂. A simplified mechanism including 24-step elementary reaction was obtained and the laminar burning velocity calculated by this simplified mechanism matches well with the detailed mechanism in a wide range. This simplified mechanism was also applied in a CFD model which predicted the cylinder instantaneous pressure and NOx emission accurately within a large range of fuel air equivalent ratio. Showing that this mechanism has good applicability.     

两台竹浆碱回收锅炉NOx、SO2排放的探讨

根据两台竹浆碱回收锅炉的实际运行情况,对其结构与运行对污染物排放的影响进行了比较、分析。     

Effect of excess hydrogen on hydrogen fueled internal combustion engine under full load

Detailed hydrogen-air chemical reaction mechanisms were coupled with three dimension grids of an experimental hydrogen fueled internal combustion engine (HICE) to establish a combustion model based on CONVERGE software. The influence of excess hydrogen coefficient on the combustion and emission characteristics of HICE under full load was studied based on the CFD model. Simulation results showed that excess hydrogen leaded to higher concentration of OH species in flame front, and quicker hydrogen-oxygen reaction and flame propagation speed, which in turn leaded to higher pressure and temperature in cylinder. The rise of pressure and temperature in turn contributed to the increase of indicate power but un-burned hydrogen leaded to decrease of efficiency. NOx, especially NO emissions decreased significantly with excess hydrogen under full load not only because increased of H concentration, and decreased of O and OH concentration, which leaded to reverse reaction of NO formation through thermal NO routes. Low excess hydrogen coefficient can achieve a good trade-off between power and emissions under full load.     

助燃空气对乙烯裂解炉NOx排放的影响

乙烯裂解炉内复杂物理化学过程耦合模拟与优化能够满足乙烯装置对高效率、低污染和低成本的设计和操作要求，对提高乙烯工业的竞争力具有重要意义。针对简单燃烧机理难以准确预测炉膛燃烧生成NO_x浓度分布的弊端，提出了在裂解炉使用更准确的简化GRI-Mesh 3.0机理结合涡耗散概念(EDC)模型的方法，并对Sandia Flame D的燃烧过程进行计算流体力学(CFD)模拟，验证了此耦合模型的可靠性。在已建立的燃烧模型的基础上，研究了助燃空气对降低裂解炉NO排放的影响，结果表明：在满足裂解炉热效率的情况下，空气预热温度为300~600 K、过量空气系数为1.1时降低NO的效果最佳。     

Impact of hydrogen fueled hypersonic airliners on the O3 layer depletion

The promising opportunity to reach intercontinental long distances in a few hours is a remarkable issue for both private companies and public organizations: teams of scientists, technicians and researchers in Europe, USA, China, Russia and India are working at national and international programs on long range high speed civil transport. The Space X's CEO also announced, at the IAC 2017 conference, the growing interest in developing a 30-min transatlantic passenger flight by means of a 2-stage rocket-based vehicle. Meeting the dwell requirement of antipodal ranges and high speeds is realistic through a new era of hydrogen-fuelled hypersonic airbreathing vehicles. The interest in hydrogen as aviation fuel has recently increased not only due to the growth of worldwide air travel and time reduction requirements, also for the dramatic rise of common aviation fuel prices, and the continuously increasing restrictive environmental issues.In the light of these changes that have occurred in fuel prices, emissions reduction imperatives and the currently higher demand for supersonic airline travels, hydrogen-fuelled hypersonic airbreathing airliners are a valuable chance with respect to other means of transport (i.e., a rocked based passenger transport). In fact, hydrogen is one of the most environmental friendly fuels, since no particulate and carbon oxide emissions are produced. Past objections on hydrogen as fuel for civil transport, such as safety, liquefying and storing hydrogen are now overcame and its technological maturity opens a large worldwide market for hydrogen as “green” fuel. However, since the opportunity for hydrogen as fuel for future fleets of airline transport resides in its “green” peculiarity, the investigation of the impact of the H₂/air hot exhausts on the ozone layer depletion is mandatory. In fact, a lot of hypersonic cruise vehicles fly at an altitude of 25000–30000 m that corresponds to the ozonosphere. In this region, the concentration of ozone is maximum and NOx emissions may catalyse the ozone destruction.In this context, the goal of this paper is to estimate the effect of the H₂/air emissions (i.e., nitrogen oxides, hydroxide and water vapor) of a fleet of 200 hydrogen fuelled hypersonic airliners flying once a day for 360 days from Brussels to Sydney, on the ozone layer and on the global temperature increase.     

浮法玻璃熔窑火焰空间石油焦部分替代重油燃烧的数值模拟

针对浮法玻璃熔窑火焰空间建立模型并进行了数值模拟，在保证热值相同的前提下，对比研究了重油燃烧及将石油焦部分替代重油燃烧时的流场分布特征。结果表明，石油焦部分代替重油燃烧后，两种燃料可很好地混合燃烧，窑炉内温度制度基本不受影响；石油焦着火时间比重油长，两种燃料混合燃烧时平均着火点滞后于仅使用重油时，且燃烧路径更长，燃烧时产生了大量CO，整个火焰空间及烟气出口处NOx的平均排放量与仅使用重油相比降低了30.02%，NOx减排效果明显。     

F级燃机联合循环NOx排放控制措施经济性分析

以某F级燃机联合循环机组为例,考虑电价气价和年利用小时数等因素,研究燃机控制直接降NOx和使用SCR脱硝对于经济性的影响。     

Simulation and experimental study of the NOx reduction by unburned H2 in TWC for a hydrogen engine

The unburned H₂ can be used to reduce NO emission in conventional TWC (three-way catalyst) for a hydrogen internal combustion engine when it works at equivalence ratio marginally higher than the stoichiometric ratio. To explore the effects and feasibility of this reaction, a Perfectly Stirred Reactor simulation model of TWC has been built with simplified mechanisms. Experiments on a 2.3 L turbocharged hydrogen engine are used to verify the conclusion. It shows that rising initial temperature accelerates the reduction of NO and the maximum reaction rate occurs at 400 °C temperature. The conversion efficiency of NO remains approximately 0 when temperatures below 300 °C. The efficiency reaches a peak value of approximately 98% with 400 °C and declines gradually. The unburned H₂ to NO mixing ratio greater than 1.5 in TWC guarantees 100% NO conversion efficiency. The experiments indicate that the NOx concentration decreases from 2056 ppm to 41 ppm at the stoichiometric ratio after the treatment of TWC and NOx reaches 0 ppm with a rich ratio. Results also demonstrate that the suitable reaction temperatures for TWC locate in the range of 400 °C–500 °C. Therefore, if the temperature and the mixing ratio are appropriate, it can achieve zero emissions with NOx reduction by unburned H₂ in conventional TWC for a hydrogen engine.     

Numerical simulation of ammonia/methane/air combustion using reduced chemical kinetics models

Ammonia appears to be a potential alternative fuel that can be used as a hydrogen vector and fuel for gas turbines and internal combustion engines. Chemical mechanisms of ammonia combustion are important for the development of ammonia combustion systems, but also as a mean of investigation of harmful NOx emissions, so they can be minimized. Despite of large body of experimental and modelling work on the topic of ammonia combustion, there is still need for additional investigation of combustion kinetics.The object of this work is further numerical study of ammonia combustion chemistry under conditions resembling industrial ones. After literature review, three mechanisms of ammonia combustion that also include carbon chemistry are used for simulation of experimental premixed swirl burner with the aim of evaluating their performance. San Diego mechanism, that was also the most detailed one, proved to be the best in terms of emissions, but neither one of the models was able to accurately reproduce CO emission after equivalence ratio went beyond 0.81. It was also observed that oxygen is excessively consumed. This study contributes to the current knowledge by providing new insights in ammonia burning conditions closely resembling those in industrial applications, and consequently is expected that insights obtained will help in the design of real industrial burning systems.     

采暖期燃煤排放对四平市空气质量的影响分析

文章于2014年4月1日~4月30日在吉林师范大学对大气污染物PM10、NOX和SO2进行监测。采暖期,PM10、NOx和SO2的浓度分别为150.9μg/m3、46.4μg/m3和27.3μg/m3,虽没有超过空气质量标准,但是其数值都比非采暖期高。采暖期PM10浓度为非采暖期的1.6倍,NOx和SO2的浓度分别为非采暖期的1.3倍和1.8倍。无论是采暖期还是非采暖期,AQI指数与PM10浓度呈强相关性,说明PM10为四平市首要大气污染物。