柴油/甲醇组合燃烧尾气中甲醛排放特性研究

在一台经过改装的压燃式组合燃烧发动机上,采用柴油/甲醇组合燃烧(DMCC)模式进行了台架试验,利用气相色谱分析技术检测了发动机在1 800 r/min时尾气中甲醛的排放特性,研究了不同负荷、不同喷醇量对尾气中甲醛排放量的影响,同时研究了催化转化器对甲醛的转化效果.试验结果表明:在压燃式发动机上采用DMCC模式,低负荷运行时,尾气中甲醛含量随喷醇量的增大而增加,在甲醇对柴油的替代率为45%时,甲醛排放量达到170×10-6(体积分数);在中、高负荷运行时,甲醛排放量随喷醇量的变化趋势不是特别明显,在90×10-6以内.催化转化器对甲醛的转化效率与排气温度关系密切,当排气温度在290℃以下时,催化转化器可以有效降低甲醛排放量;当温度高于300℃时,催化后尾气中的甲醛排放量反而增加.     

贫燃催化燃烧燃气轮机的研究进展

超低热值燃气(ULHVF)种类繁多,总量非常巨大。ULHVF甲烷浓度1%～5%,很难点火燃烧,直接排放到大气中,造成环境污染。催化燃烧是处理ULHVF最有效的燃烧方法。对催化燃烧机理及其燃气轮机催化燃烧的研究现状进行了综述,总结了燃气轮机催化燃烧和燃气轮机贫燃催化燃烧的技术关键点,介绍了燃气轮机贫燃催化燃烧系统、部件工作特性等方面的研究成果,指出了燃气轮机催化燃烧、燃气轮机贫燃催化燃烧的不足以及解决方案,提出了后续工作的发展方向。燃气轮机贫燃催化燃烧的研究进展包括:贫燃催化燃烧特性的数值模拟与试验验证;系统中叶轮机械部件的设计及性能分析;催化燃烧对系统特性影响的分析。     

四气门发动机可变滚流结构稀薄燃烧特性的研究

研究了可变滚流结构的稀薄燃烧特性。主要讨论了可变滚流结构对发动机稀薄燃烧时燃油经济性和排放特性的影响。结果表明 :在稀薄燃烧情况下 ,发动机负荷大小对 CO排放的影响不大 ,CO排放始终保持在 0 .5 %以下 ;HC排放则具有相似的变化趋势 ,但排放量随负荷增加而略有增加 ;负荷对 NOx 排放的影响主要表现在空燃比为 13～ 18的范围内 ,负荷越大 ,NOx 排放越大 ;对空燃比小于 13或大于 18的 NOx 排放影响较小。阀片位置 (或滚流比 )对发动机稀燃状态 CO排放的影响很小 ,而对 HC和 NOx排放则存在一定影响。在稀薄燃烧条件下 ,滚流运动更有利于改善低速高负荷时的燃油经济性。     

空燃比对柴油/丙烷混合燃料发动机燃烧和排放的影响

在单缸直喷式柴油机上,研究了燃用柴油和柴油/丙烷混合燃料时,空燃比对发动机燃烧和排放特性的影响。结果表明:发动机转速一定时,燃烧持续期随空燃比和丙烷比例的增加而缩短;缸内最高燃烧压力随空燃比的增大而减小,随丙烷比例的增加而增大;NOx和碳烟排放随空燃比的增大而降低,HC排放在小空燃比时随空燃比的减小而大幅度增加,而在大空燃比时随空燃比的增大而稍有增加;在小空燃比时CO排放随空燃比的减小而增加,在大空燃比时变化不大;燃用柴油/丙烷混合燃料可同时降低CO、HC和碳烟排放,但NOx排放增加。     

空燃比对稀土三元催化剂净化效率的影响

在不同空燃比下，利用几种含有不同助催化剂的稀土催化净化器在汽机台架上进行了一系列试验，试验发现：空燃比对稀土三元催化剂在尾气中的CO，HC，NO和NOx净化效率有着明显的影响，尤其在稀混合气时，稀土三元催化剂具有较高的催化交，说明稀土元催化剂可以用于稀薄燃烧系统，此外，试验中发现转速和负荷对其净化效率有一定的影响。     

催化剂组合控制稀燃汽油机排放策略的试验研究

采用不同分子筛催化剂的组合和机内净化的综合控制策略,对汽油机稀燃排放的控制进行了试验研究.试验的催化剂种类包括Cu-In-ZSM5、Ir-ZSM5、Cu-Co-ZSM5、Pd-In-ZSM5、Ni-Cu-ZSM5等.试验考察了空速比对NOx转化效率的影响.综合应用以HC为主要还原气体并可产生CO排放的分子筛催化剂如Ni-Cu-ZSM5、Cu-Co-ZSM5等,和CO、HC协同还原NOx催化效果较好的分子筛催化剂如Ir-ZSM5、Pd-In-ZSM5等,在合适的条件下可以实现70%以上的NOx转化率.催化后NOx浓度降至150×10-6以下.同时与当量空燃比燃烧时相比仍可节油8%～10%.多种催化剂的综合使用,使得催化活性随温度变化的规律变得复杂.     

进气压力对发动机性能的影响研究

在一台3.8L涡轮增压中冷4缸柴油机上通过试验和仿真研究了进气压力对柴油机燃烧和性能的影响。试验中拆除了原机增压器及中冷器,通过自制压力调节装置直接控制柴油机进、排气压力。试验及仿真结果表明:在排气压力维持不变的条件下,最高燃烧压力与进气压力具有明显的线性关系,进气压力每增加100kPa,最高燃烧压力增加约4.8MPa~7.0MPa;进气压力对最高燃烧压力相位的影响不明显;空气质量流量与进气压力具有明显的线性关系,进气压力每增加10kPa,空气质量流量增加约13~37kg/h;柴油机排气温度与空燃比具有明显的线性关系,空燃比每增加1,柴油机排气温度降低约4.2℃;随进气压力增加,柴油机缸内燃烧滞燃期缩短,燃烧始点提前,但进气压力对燃烧持续期没有明显影响;进气压力每增加10kPa,发动机转矩增加约0.8~2.5N·m。     

汽油发动机稀薄燃烧NO_x后处理系统试验研究

在一台1.5L涡轮增压缸内直喷汽油发动机上,使用不同的三效催化反应器(three-way catalytic,TWC)、稀燃NO_x捕集器(lean NO_x trap,LNT)、被动选择性催化还原器(passive selective catalytic reduction,PSCR)等排气后处理组合,研究了汽油发动机稀薄燃烧下不同NO_x后处理催化器性能。试验工况为基于该发动机在某车型的世界统一轻型车测试循环工况的14个聚类点。结果表明,稀薄燃烧能有效降低有效燃油消耗率,部分负荷下可减少3.1%～10.1%。稀燃模式下,过量空气系数每增加0.1,NO在NO_x总量中占比降低6.9%;浓燃模式下,总体趋势上,TWC前的NO体积分数每增加100×10~(-6),NH_3增加48×10~(-6);过量空气系数0.95时,TWC的NO—NH_3转化率在51%～74%之间;TWC+LNT+PSCR能有效提高浓稀工况切换时稀燃模式运行时间;稀燃工况,LNT能促进NO氧化成NO_2,提高NO_2比例,提高PSCR的催化效率。     

催化燃烧对均质压燃发动机燃烧特性影响的数值模拟

通过运用DETCHEM软件包,对甲烷在催化剂Rh表面的详细反应机理进行了分析,结果表明数值模拟结果与实验数据相当吻合;通过耦合DETCHEM软件包及CHEMKIN软件包中的SENKIN模块,对活塞顶涂有催化剂铑的均质压燃(HCCI)发动机的燃烧过程进行了数值计算,建立了单区和多区模型．利用单区模型分析了催化燃烧对HCCI发动机着火时刻的影响,同时讨论了催化燃烧对燃烧过程中主要化学组分浓度变化的影响,结果表明催化燃烧会使HCCI发动机着火时刻提前;利用多区模型分析了催化燃烧对HCCI发动机的未燃碳氢化合物(UHC)、氮氧化合物(NOx)排放的影响,结果表明催化燃烧能降低UHC的排放,但会提高NOx的排放．     

缸内直喷灵活燃料发动机性能和燃烧特性的研究

根据所测的示功图和排放结果,分析了一台采用火花点火、缸内直喷周向分层燃烧系统,能够灵活燃用甲醇、乙醇和汽油的发动机的性能和燃烧特性.研究表明,由于采用分层燃烧,灵活燃料发动机具有与直喷柴油机相当的热效率,在负荷特性上,燃用醇类燃料和汽油时的NOx排放分别仅为柴油机的10%～40%和21%～78%,CO排放低于1%,HC排放略高于柴油机,燃用醇类燃料时能实现无烟燃烧,燃用汽油时仅在高负荷时存在少许碳烟.灵活燃料发动机的燃烧由预混燃烧与扩散燃烧组成,具有非常快的燃烧速率,上止点后3～5°CA就燃烧完50%燃料,燃烧持续期在28～37°CA范围内,甲醇的燃烧速率最快,汽油的燃烧速率在低负荷时比乙醇稍快,在高负荷时比乙醇慢.     

A review on plasma combustion of fuel in internal combustion engines

In recent years, new ways of improving the combustion efficiency of fuel during gas turbine operations have been developed. The most significant has been the application of plasma technology for the combustion of fuel in gas turbine operations. Plasma is formed when gas is exposed to either high temperature or high‐voltage electricity. This technology is very promising and has proven to enhance the performance of gas turbines and reduce toxic emissions. Recent studies have shown the use of different types of plasma applications in gas turbine operations such as plasma torch, filamentary discharge, and nanosecond pulse discharge, whose results show that plasma technology has great potential in improving flame stabilization, the fuel/air mixing ratio, and flash point values of these fuels. These findings and advances have further provided new opportunities in the development of efficient plasma discharges for practical uses in plasma combustion of fuel for gas turbine operations. This article is a comprehensive overview of the advances and blind spots in the knowledge of plasma combustion of fuel during internal combustion engine operations. This review also focuses on applications, methods, and experimental results in plasma combustion of fuel in gas turbines.     

Investigation of forward flow distributed combustion for gas turbine application

New innovative advanced combustion design methodology for gas turbine applications is presented that is focused on the quest towards zero emissions. The new design methodology is called colorless distributed combustion (CDC) and is significantly different from the currently used methodology. In this paper forward flow modes of CDC have been investigated for application to gas turbine combustors. The CDC provides significant improvement in pattern factor, reduced NO_x emission and uniform thermal field in the entire combustion zone for it to be called as an isothermal reactor. Basic requirement for CDC is carefully tailored mixture preparation through good mixing between the combustion air and product gases prior to rapid mixing with fuel so that the reactants are at much higher temperature to result in hot and diluted oxidant stream at temperatures that are high enough to autoignite the fuel and oxidant mixture. With desirable conditions one can achieve spontaneous ignition of the fuel with distributed combustion reactions. Distributed reactions can also be achieved in premixed mode of operation with sufficient entrainment of burned gases and faster turbulent mixing between the reactants. In the present investigation forward flow modes consisting of two non-premixed combustion modes and one premixed combustion mode have been examined that provide potential for CDC. In all the configurations the air injection port is positioned at the opposite side of the combustor exit, whereas the location of fuel injection ports is changed to give different configurations. Two combustion geometries resulting in thermal intensity of 5 MW/m³-atm and 28 MW/m³-atm are investigated. Increase in thermal intensity (lower combustion volume) presents many challenges, such as, lower residence time, lower recirculation of gases and effect of confinement on jet characteristics. The results are presented on the global flame signatures, exhaust emissions, and radical emissions using experiments and flowfield using numerical simulations. Ultra-low NO_x emissions are found for both the premixed and non-premixed combustion modes at the two thermal intensities investigated here. Almost colorless flames (no visible flame signatures) have been observed for the premixed combustion mode. The reaction zone is observed to be significantly different in the two non-premixed modes. Higher thermal intensity case resulted in lower recirculation of gases within the combustion chamber and higher CO levels, possibly due to lower associated residence time. The characteristics at the two thermal intensity combustors investigated here were found to be similar.     

Droplet combustion in the presence of acoustic excitation

This experimental study focused on droplet combustion characteristics for various liquid fuels during exposure to external acoustical perturbations generated within an acoustic waveguide. The alternative liquid fuels include alcohols, aviation fuel (JP-8), and liquid synthetic fuel derived via the Fischer–Tropsch process. The study examined combustion during excitation conditions in which the droplet was situated in the vicinity of a pressure node (PN). In response to such acoustic excitation, the flame surrounding the droplet was observed to be deflected, on average, with an orientation depending on the droplet’s relative position with respect to the PN. Flame orientation was always found to be consistent with the sign of a theoretical bulk acoustic acceleration, analogous to a gravitational acceleration, acting on the burning system. Yet experimentally measured acoustic accelerations based on mean flame deflection differed quantitatively from that predicted by the theory. Phase-locked OH^∗ chemiluminescence imaging revealed temporal oscillations in flame standoff distance from the droplet as well as chemiluminescent intensity; these oscillations were especially pronounced when the droplets were situated close to the PN. Simultaneous imaging and pressure measurements enabled quantification of combustion-acoustic coupling via the Rayleigh index, and hence a more detailed understanding of dynamical phenomena associated with acoustically coupled condensed phase combustion processes.     

无焰燃烧发展及研究现状

无焰燃烧是一种同时具备高效和低排放特点的燃烧技术,然而传统实现无焰燃烧所需的高温预热空气及高速射流两大重要条件,提高了整体工业设备实现无焰燃烧的复杂性,限制了该技术在更广阔领域的发展。本文综述了无焰燃烧燃烧机理与特性的研究发展,并提出了未来可能的发展趋势。分析发现：高温预热空气并不是实现无焰燃烧的必要条件,而通过高速射流提高炉内烟气循环率却必不可少;使用EDC模型结合GRI 3.0反应机理能在数值模拟中得到贴合实验数据的结果;气体、液体及固末燃料均可实现无焰燃烧,使用CH4/H2混合气体实现无焰燃烧可在提升燃烧稳定性的同时依旧保持低排放的特点;炉膛结构可很大程度上影响炉内流场进而影响无焰燃烧效果。因此,研究无需预热的无焰燃烧系统在降低工业成本的同时可增大燃料种类的选择性,通过设计合理的炉膛结构,营造良好的炉内流场在强化无焰燃烧效果的同时可一定程度降低对初始射流速度的要求,研究CH4/H2混合气体的燃烧机理具有十分重要的意义。     

准均质充气压缩点燃系统燃烧特性研究

准均质充气压缩点燃（QHCCI）燃烧系统是在柴油机上实现稀薄预混合气燃烧的有效方法，建立了一个燃烧过程准维数学模型，结合试验结果，对QHCCI系统的燃烧特性进行了研究。内容包括引燃柴油喷射定时对系统燃烧性能的影响，引燃柴油喷射量对系统的影响，以及发动机工作粗暴的特性。模拟结果与试验结果一致，并发现QHCCI燃烧系统的放热律曲线一般呈双峰，引起爆震的原因主要是引燃柴油喷射量大或喷射早造成上止点附近的大量剧烈燃烧造成的。     

锅炉氧煤无焰燃烧技术分析

氧煤燃烧是一种全新燃烧方式,将氧煤燃烧器的表观氧气浓度从30％提高到50％、将O2/CO2混合气改变为纯氧气与再循环CO2烟气分离、将喷嘴速度从50m/s左右提高到200 m/s左右组织炉膛烟气形成高倍率内循环,从而在炉膛内实现高温低氧的氧煤无焰燃烧状态,氧煤无焰燃烧技术能实现煤粉高效燃烧和较低NO浓度排放的统一,锅炉...     

First and second thermodynamic-law analyses of hydrogen-air counter-flow diffusion combustion in various combustion modes

In this paper, from the viewpoints of both the first and the second law of thermodynamics, we conduct a comprehensive study on hydrogen-air counter-flow diffusion combustion in various modes. The effects of air inlet temperature (T_oxi) and effective equivalence ratio of fuel (φ) on the reaction zone structure and entropy generation of combustion are revealed over a wide range of T_oxi and φ. Through the present work, five interesting features of combustion of this kind, which are quite different from that reported in the literature, are presented. Especially, for the first time we divide various combustion modes in the φ − T_oxi map instead of the popular way used in previous studies. Such innovation can help judge the final combustion regime more straightforwardly for any given operative condition.     

掺氢对微尺度空间内预混层流火焰转捩爆燃特性的影响

针对基于燃烧的微小型动力装置存在燃烧效率低、火焰传播速度慢的问题,设计了一个可视化的、特征间距仅为0.45 mm的微尺度定容燃烧室,实验比较了0~1的掺氢比例下,丙烷/氢气/空气预混火焰在该燃烧室内的传播以及加速过程.实验发现没有掺氢时,丙烷/空气预混火焰需要在0.25 MPa初始压力下才能够传播;当掺氢比例为0.2时,火焰在传播过程中会发生从缓燃到爆燃的转变,这种燃烧模态的转变可以大幅缩短燃烧室内火焰传播时间,极大提升火焰传播速度.实验还发现掺氢比例以及初始压力的提升均能使得微尺度火焰传播速度提升.     

摆动式水平浓淡风煤粉燃烧器在670 t/h锅炉的应用研究

我厂2号锅炉(DG 670/13.7-8A)为四角切圆布置,一、二次风间隔布置,分上下两组,设计煤种为晋中贫煤.在实际运行中,煤质不稳定,锅炉着火和燃烧稳定性差.采用"摆动式水平浓淡风煤粉燃烧器"技术对燃烧器改造后,燃烧效率提高0.84%、在300 t/h时能稳定燃烧、炉膛无结渣,锅炉参数稳定.     

一种高效率的内燃机燃烧模式

本文探讨了以双燃料发动机为代表的预混合和扩散燃烧共存的复合燃烧模式。认为这种燃烧模式兼有预混合燃烧和扩散燃烧的优点，而且有比传统的燃烧模式更高的热效率。实验证明，采用这种燃烧模式工作的发动机可以有比火花点火式发动机更高的压缩比，有比压燃式发动机更高的燃烧速率。最后对这种发动机的燃烧特性及获得较高热效率的原因进行了分析。