超低排放脱硝喷氨格栅优化策略

超低排放改造后脱硝系统普遍出现氨逃逸大、空预器堵塞严重、喷氨自动无法投入等问题。通过仿真设计优化、喷氨格栅调整、精准喷氨改造等优化手段,能改善催化剂入口氨氮摩尔比,从而保证NOx减排系统的稳定运行。喷氨格栅优化能实现对氨逃逸的控制,可以减少还原剂耗量和降低引风机电耗,具有明显的经济性。     

基于CFD建模的1000MW电站锅炉SCR脱硝系统喷氨策略优化

以某1 000 MW电站锅炉的选择性催化还原(SCR)脱硝系统为研究对象,入口截面采用现场实测流场和NO_x浓度场分布数据,对耦合反应器内的湍流流动、多组分混合及化学反应进行了基于CFD建模的数值计算研究,并基于氨氮比一致分配理论,利用数值模拟多次试算获得最优喷氨策略,对该最优喷氨策略进行现场验证.结果表明:实际入口为非均匀流场和浓度场,采用均匀喷氨策略,催化剂上部截面氨氮比及出口附近测点位置氨气浓度分布极度不均,氨逃逸严重;现场验证实验表明,本文方法确实可有效地指导喷氨优化调整,降低调整盲目性,提高现场工作效率.     

500MW机组脱硝系统喷氨格栅优化设计

合理的喷氨系统可保证烟气中的氮氧化物和脱硝剂氨均匀混合,有利于提高脱硝效率,节约氨耗量;减少催化剂预装量,延长催化剂寿命;保证达标排放,降低硫铵堵塞引发的安全风险;降低投资和运行管理成本。以某500 MW机组SCR系统为研究对象,设计3种不同形式的喷氨格栅进行数值模拟。选择催化剂入口截面速度和氨浓度分布最为均匀的方案,对原喷氨系统进行改造。结果表明:工程改造后,SCR出口NO_x浓度不均匀度由最高57.40%降低到20.20%,氨逃逸由最高24×10~(-6)降低到1×10~(-6),液氨耗量节约10%以上。     

650MW电厂SCR脱硝系统喷氨装置协调优化

山东某电厂650MW燃煤机组SCR（selective catalytic reduction）脱硝系统氨气逃逸率较大,导致催化剂的堵塞、失活及中毒。通过FLUENT数值模拟建立三维脱硝系统模型,模拟了在反应器顶部不同导流板数量及喷氨速度下SCR系统流场分布,通过对结果的分析比较,得出适当增加导流板组数和合理差异化的调整各喷口喷氨速度能够使第一层催化剂入口的NH₃浓度、NO_X浓度及NH₃/NO_X分布更加均匀化合理化,很好的满足了设计和运行的双重检测,为SCR脱硝系统的协调优化和机组运行的稳定性提供了实际参考价值。     

超低排放SCR烟气脱硝系统的优化分析

SCR烟气脱硝系统超低排放改造后出现了NH_3/NO_x分布均匀性及喷氨优化调整要求提高的现象。对此,在流场优化的基础上提出了基于氨氮比修正因子的SCR喷氨优化调整方法,采用CFD数值计算对比分析了某300 MW机组优化导流装置前后考核截面速度分布、压差变化以及喷氨优化调整前后的氨氮比分布,最后将计算结果与工业性试验进行了比较。结果表明:通过对导流装置的优化,SCR反应器的流场得到较大改善,可满足超低排放后SCR系统对流场的要求。基于氨氮比修正因子的SCR喷氨优化调整方法解决了仅依靠经验调整反应器出口NO_x浓度场耗时长、效率低、难度大的缺点,优化后的SCR脱硝系统运行指标良好,实现了稳定的超低排放运行。     

基于RBF神经网络的SCR脱硝系统喷氨优化

为实现对电厂选择性催化还原(SCR)脱硝装置喷氨的优化控制,以广东某电厂350 MW锅炉为研究对象,采用径向基函数(RBF)神经网络法,以锅炉负荷、烟气体积流量、SCR烟气温度、脱硝进口NO_x 质量浓度以及喷氨质量流量等为输入变量,以SCR脱硝效率为输出变量,建立输入变量与输出变量之间的关系模型,实现对SCR脱硝效率及脱硝出口NO_x 质量浓度的预测.在满足NO_x 排放标准的前提下,以SCR系统运行成本最小为目标,利用Matlab对该模型进行仿真实验,寻求氨耗成本和电耗成本与NO_x 排放费用的临界点,得到最佳喷氨质量流量.结果表明:最佳喷氨质量流量计算值比实测值或高或低,但在满足NO_x 排放标准的前提下,其SCR系统运行成本呈降低趋势.     

基于延迟特性的NOx浓度软测量与喷氨优化

针对NO_x浓度测量延迟导致NO_x排放浓度波动较大的问题,为提升脱硝系统运行的稳定性,试验分析了NO_x浓度测量的延迟时间和锅炉关键控制参数改变后SCR入口NO_x浓度的响应时间,建立了表征锅炉运行动态特性的SCR入口NO_x浓度软测量的数据结构,进一步建立了基于XGBoost算法的动态工况下SCR入口NO_x浓度实时软测量模型。结果表明：SCR入口NO_x质量浓度的测量延迟时间约为1 min,软测量模型能够提前近1 min得到实际NO_x质量浓度,软测量曲线与实际曲线具有理想的跟随性和准确性;软测量模型在660 MW机组上投入应用后,喷氨流量曲线和NO_x排放质量浓度曲线的稳定性得到显著提升。     

混合集箱结构优化数值模拟

本文采用数值模拟方法分析集箱管接头的排布情况对介质混合过程的影响,研究表明,集箱管接头的合理排布可以提高介质的混合均匀性和流畅性。     

基于神经网络的分区喷氨量研究

电厂烟气脱硝常采用SCR(选择性催化还原)系统,在实际运行过程中发现第一层催化剂入口往往存在NOX浓度分布不均的情况,按照已有的均匀喷氨方案往往导致催化剂层入口氨氮比分布偏差大的问题,从而进一步影响脱硝效果。文中在已有的SCR反应器冷态试验台的基础上,以喷氨格栅(AIG)分区精准喷氨为研究对象,首先将AIG分为10个分区,其次以催化剂入口截面设置的25个测点的与分区喷氨量相对应氨气浓度为目标,建立CFD仿真模型,得到不同的AIG分区喷氨量组合在25个测点上的氨浓度分布;然后将25个测点的氨气浓度为输入参数,分区喷氨量为输出参数对BP人工神经网络进行训练,而在实际使用中根据测点NOX浓度按照设定氨氮摩尔比将所需氨浓度输入神经网络,即可得到当前NOX分布下的所需的分区喷氨量;最后针对几种典型的入口NOX分布,使用训练好的BP神经网络得到分区喷氨量,将该分区喷氨量输入CFD仿真发现第一层催化剂入口前25个监测点的氨氮比标准偏差系数在3.6%以下,满足电厂低于5%的技术需求。     

涡流混合式SCR系统喷氨特性试验研究

对涡流混合式脱硝系统进行喷氨优化试验.通过喷氨支管手动蝶阀的调节,脱硝出口A侧不均匀度下降了4％;B侧脱硝出口不均匀度下降了24.8％.试验发现,NOx浓度沿烟道深度方向分布不均.分析可能的原因,一是涡流盘结构限制导致的氨浓度分布不均;二是烟道结构导致的流场不均,从而影响脱硝反应进行得不够均匀.综合考虑经济与环保,推荐...     

The effect of chemical reaction on the mixing flow between aqueous solutions of acetic acid and ammonia

The basic characteristics of the reacting mixing flow of two streams were investigated. The reaction between aqueous solutions of ammonia and acetic acid, which produces ammonium acetate, was investigated in terms of the effect on the fluid–fluid interface of the mixing flow relative to fluids that did not react. The reaction between these solutions was negligibly exothermic, and there were minimal differences in density. The velocity field in the reacting mixing flow was quantitatively measured using high-speed time-resolved particle image velocimetry (PIV) and the behavior of the mixing flow was qualitatively investigated using laser-induced fluorescence (LIF). The jet width, the velocity field, the kinetic energy and the turbulent intensities are qualitatively estimated and discussed. It was found that the chemical reaction resulted in the suppression of the mixing flow.     

质子导体固体氧化物电化学装置中氨的利用与合成

氨作为一种理想的储能材料和氢能源载体,其在质子导体固体氧化物电化学装置中的利用与合成可实现高效清洁的发电和储能.本文综述了质子导体固体氧化物电化学装置中氨的利用与合成的实验和理论研究进展,在实验研究方面全面分析了电解质和氨电极材料的开发,在理论研究方面重点讨论了热力学-电化学模型和密度泛函理论(DFT)的研究概况.电解质的质子电导率和氨电极的催化活性是影响电化学装置性能的关键因素,因此开发高质子电导率的电解质和高催化活性的氨电极仍是主要的研究方向.热力学-电化学模型和基于DFT的理论研究可分别为电化学装置的结构设计/运行条件的优化和氨电极材料的开发提供有效指导和思路,但是对于更高层次(三维)的热力学-电化学模型理论研究和氨电极材料上氮气的电化学活化机理的研究仍需加强.最后总结指出了质子导体固体氧化物电化学装置中氨的利用与合成的未来研究方向.     

带错排V肋和反V肋矩形通道强化传热机理及规律研究

采用热色液晶瞬态测量技术研究了带45°V肋和45°反V肋的矩形通道端壁的传热特性,分析V肋诱导产生二次流强化传热机理及其传热系数分布规律。通道进口雷诺数变化范围是10 460~32 100,肋高与当量直径的比为0.13,肋间距与肋高的比为10。实验结果表明:带V肋和反V肋矩形通道传热系数随着雷诺数的增大而增大;正V肋诱导产生沿V肋从中间向两侧发展的二次流,反V肋片诱导气流沿肋方向产生从两边流向中间的二次流;斜置V肋诱导产生的二次流增强了通道的传热能力;带V肋通道的传热强于带反V肋通道。     

Effects of plate vibration on the mixing and combustion of transverse hydrogen injection for scramjet

Transverse injection is an effective mixing enhancement technique for the combustor of scramjets. Vibration of the plate structure in combustor will easily be induced due to aerodynamic load and harsh aerothermodynamic load simultaneously. Effects of the plate vibration on the mixing and the combustion of the transverse hydrogen injection have been investigated numerically in this study. Finite rate chemistry model is used as combustion model. The supersonic jet experimental model of the Stanford University is modified slightly and used as the analysis model. Effects of the frequency and the amplitude of the plate vibration on combustion performance and flow field structure have been investigated in detail. The results show that the plate vibration increases the mixing efficiency, the combustion efficiency and the total pressure loss coefficient. Besides, it can change the flame structure and the shock wave structure, as well as increase the shock wave intensity at downstream of the injection. The vibration frequency has relatively little effect on the combustion efficiency and the total pressure loss coefficient. When the vibration frequency is large, it presents some high frequency pulsations for the total pressure loss coefficient. However, the vibration amplitude has large effect on combustion efficiency and the total pressure loss coefficient. When the vibration amplitude is small, the combustion efficiency presents regular periodic change with time. When the vibration amplitude is large, it diverges with time, and the flow tends to be unstable. The large vibration amplitude changes the stability of the original flow. Consequently, the combustion with large amplitude fluctuation can critically damage the combustion stability.     

The Effect of Injection Angle on Mixing and Flame Holding in Supersonic Combustor

IntroductionMixing of fuel with oxidizer and their combustionare encountered in many engineering applicationsincluding hypersonic propulsion system in space vehicles.Particularly, the fuel injection scheme in hypersonicvehicles incorporating Scramet (Supersonic CombustionRamjet) engines, requires special attention for efficientmixing and stable combustion. Though a considerablenumber of researches has been cwhed out on ndxing andcombustion of fuel with oxidizer in Scramet program,still it fa…     

掺混比例和喷射定时对二甲醚-乙醇发动机燃烧和排放的影响

在一台电控共轨发动机上,试验研究了乙醇掺混比例和喷射定时对二甲醚-乙醇混合燃料燃烧及排放的影响。结果表明:随乙醇比例的增加,滞燃期延长,燃烧持续期缩短,最大压力升高率上升。随喷射推迟,滞燃期延长,燃烧相位延后,燃烧持续期在纯二甲醚时延长,而在掺混乙醇时则先延长后缩短,最大压力升高率先下降后上升。掺混乙醇和推迟喷射使预混燃烧比例增加。随喷射推迟,混合燃料的排气温度升高,喷射推迟到上止点后,排气温度随乙醇比例的增加而升高,排气温度高,则废气能量高,增压器增压比大,进气流量大,导致缸内压缩压力升高。在上止点前喷射时,掺混乙醇能使HC和CO排放保持在较低范围的同时,一定程度降低NO_x排放,掺混15%的乙醇较纯二甲醚最大降低约11%NO_x排放。随推迟喷射,NO_x排放降低,最大降幅达52%,在过分推迟燃料喷射时,因热效率低,循环喷射量增加,含15%乙醇混合燃料的NO_x排放会高于纯二甲醚。HC和CO排放随喷射推迟而升高,且升高幅度增大。     

V形肋片型太阳能空气集热器换热特性的研究

本文运用数值模拟的方法,对带有多重V形肋片的平板型太阳能空气集热器的换热与流动特性进行了研究。在雷诺数5 000~20 000范围内,采用RNG k-ε湍流模型,研究了相对肋宽比(W/w)对集热器换热特性的影响规律,并对集热器内部流场进行了分析。研究结果表明,V形肋片增强了空气的对流换热。这是由于流体掠过肋片后,产生旋涡和回流,加强了流体扰动,从而使换热增强。相对其它肋宽比而言,W/w=6时,集热器具有较好的换热效果,努塞尔数为光滑壁面的2.54倍,但肋片的存在导致摩擦损失增加,换热性能因数最大为1.55。     

Numerical investigation on the mechanism of the effects of plate vibration on mixing and combustion of transverse hydrogen injection

This study numerically investigates the effects of plate vibration and deformation on the combustion performance, the shock wave structure, the mixing characteristics and the flame structure for transverse hydrogen injection. The finite-rate method is used to simulate combustion. Results show that plate vibration causes the combustion performance to oscillate both temporally and spatially, while plate deformation can only change the static characteristics of the flow. Plate vibration and deformation increase the intensity and number of shock wave reflections in different ways. In addition, both plate vibration and deformation increase the momentum flux ratio and the jet penetration depth, which enhances mixing. Finally, plate vibration widens the flame and moves it upward to a greater extent than plate deformation.