侧卷流和复合卷流燃烧系统混合燃烧特性

为研究侧卷流燃烧系统(LSCS)和复合卷流燃烧系统(MSCS)对直喷式柴油机性能的影响,通过单缸柴油机台架开展了LSCS和MSCS的燃烧性能试验,结合仿真分析,揭示了LSCS和MSCS的缸内油、气混合特性．结果表明：在小负荷和高过量空气系数φa下,MSCS体现出较好的燃烧性能,相比于LSCS,其燃油消耗率最大降幅为3.6 g/(kW·h),碳烟排放最大降幅为0.13 g/(kW·h),燃烧持续期最大降幅为2.6°CA;但在大负荷和低φa下,LSCS体现出更好的燃烧性能,相比于MSCS,其燃油消耗率最大降幅为2.6 g/(kW·h),碳烟排放最大降幅为0.56 g/(kW·h),燃烧持续期最大降幅为2.8°CA．仿真结果表明：随负荷减小或φa增大,燃油射流贯穿能力减弱,复合卷流燃烧室的弧脊能更有效地提升油、气混合质量;随负荷增大或φa减小,燃油射流贯穿能力增强,复合卷流燃烧室的弧脊阻碍了燃油射流扩散,侧卷流燃烧室的分流造型能更显著地改善油、气混合过程．     

直喷式增压柴油机燃烧过程可视化研究

介绍采用高速摄影技术研究直喷式增压柴油机的燃烧过程，研究工作在单缺柴油机上进行。研究结果表明，进气增压改善了上柴油机燃烧过程；促进了燃油和空气的混合，增加了燃油束向燃烧室中心的扩展区域，壁面附近燃油堆积量减小；缩短了着火延迟期，增加了扩散燃烧的比例，火焰扩展速度降低；改善了燃烧室内的燃烧条件，抑制了燃烧火焰向活塞顶部外溢。     

BUMP燃烧室的稀扩散燃烧机理

开发了BUMP燃烧室并进行了对比实验,发现BUMP燃烧室中可以形成稀的扩散燃烧氛围,使NOx和碳烟排放同时降低．喷射定时3°CA ATDC时,烟度排放降低了约70％,NOx排放与对比燃烧室相当．CFD模拟研究表明,不同的喷射定时下,燃油到达燃烧室壁面时的混合和燃烧状态不同,只有油束在滞燃期内到达燃烧室壁面,由限流沿(BUMP环)扰动形成的二次空间射流才能充分形成,稀扩散燃烧才能明显发生．     

柴油机多维燃烧模拟程序及其参数灵敏性研究

在一个模拟直喷式柴油机燃烧过程的二维模型的基础上,开发了可在微机上运行的二维计算程序,程序名为ＲＥＳＤ－２Ｄ。程序中采用了亚网格尺度（ＳＧＳ）湍流模型、蒸发性液体射流喷雾模型、着火延迟期模型,燃烧和排放的计算采用部分平衡流方法。随后对该模拟程序中与计算参数、燃油喷射、混合、燃烧等相关参数的灵敏性进行了研究,所得到的结论对于ＲＥＳＤ－２Ｄ程序走向实用化有指导意义。还应用该程序针对１２１５０Ｌ柴油机进行了计算,给出了计算结果     

TRB燃烧系统喷雾半壁射流混合的三维数值模拟

为了优化小型柴油机油气混合过程,发展了一种新型的丰田反射燃烧系统。在燃烧室壁面形状和燃油喷雾碰壁相匹配的研究基础上,应用一个包含喷雾碰壁模型的内燃机缸内气体流动和燃油喷雾混合的大型微机化软件包ＧＦＦＳＭ,进行了缸内气体流动和双喷孔柴油喷雾半壁射流混合过程的三维数值模拟计算,以分析ＴＲＢ燃烧系统提高发动机性能、减少排气污染的原因     

两种燃烧室内燃油空气混合情况的定量比较分析

对一传统ω形燃烧室和一种新式BUMP燃烧室内燃油空气混合质量进行了对比性研究,发现燃油撞壁以后在ω形燃烧室壁面形成壁面射流,这一层燃油浓度很高,很难与空气混合,而在BUMP燃烧室内,壁面射流遇到BUMP后,会在空间形成二次射流,二次射流进一步能快速与空气充分混合.利用3个评价参数：体积分数、浓度方差以及浓度耗散率对ω形燃烧室和BUMP燃烧室内燃油空气混合好坏进行了定量比较,发现BUMP燃烧室与ω形燃烧室相比,燃油能在更大的体积内与空气混合,燃油在燃烧室内分布相对更均匀,燃油能更快与空气混合.     

新型低NOx排放高温空气燃烧的数值研究

通过数值模拟对燃料射流环绕空气射流的五喷口高温空气燃烧的燃烧特性进行了研究.详细阐述了燃烧室内燃烧温度和燃烧组分的分布情况,并对NOx生成及其影响因素进行了分析.结果表明:燃烧室出口可燃物浓度低于0.1%,燃烧反应完全;燃烧反应主要发生在燃料射流包围的圆柱体内,沿射流方向,燃烧逐渐向空气射流方向扩大,燃烧过程缓慢,并在燃烧室后半段稳定燃烧;NOx主要在燃烧室的高温区域形成,降低燃烧室内高温区域的氧气浓度是抑制燃烧过程NOx生成的关键,在燃烧室入口附近,NOx的生成受燃料射流的入口温度影响较大.     

一种新的小缸径柴油机单孔直喷燃烧系统的研究

小缸径柴油机燃烧系统直喷化已经成为发展趋势，但仍面临实现柔和运行及降低有害排放产物的难题，燃烧室周边混合式燃烧系统具有工作柔和，变速适应性好等优点。但由于形成较多的壁面面膜，而使燃烧速率低，ＨＣ和微粒排放品质差，为此，本研究了旋转流场中轴针喷嘴油束扩展与混合的特性，提出了利用油束撞壁效应加速混合，改善燃烧过程的概念。在Ｓ１９５涡流室柴油机基础上设计了一种新的单孔直喷式燃烧系统。研究结果表明，该系     

新型“射流燃烧技术”在EQ6100汽油机上的应用研究

介绍应用于东风ＥＱ６１００汽油机上的一种“Ｄ”字型凹坑燃烧室的射流燃烧系统。经性能实验结果表明：这种新型汽油机比原机提高功率７．５ｋＷ，提高扭距３０Ｎ·ｍ，并节约燃油１０％左右。     

基于NURBS理论的射流燃烧汽油机缸盖模具气道的CAD／CAM技术研究

本文以当前国际上ＣＡＤ／ＣＡＭ领域最流行的非均匀有理Ｂ样条（ＮＵＲＢＳ）理论为数学模型，对射流燃烧汽油机缸盖模具的气道进行了曲面造型和曲面拟合；并结合气道曲面的实际，在数控加工中对气道曲面通过轴心线实施了分段剖分，并采用参数线法确定了刀心轨迹，进行刀具轨迹仿真，获得了数控加工气道曲面和型芯的ＮＣ程序。本研究对提高射流燃烧汽油机缸盖的模型的精度和效率，改进汽油机的气道设计均有重要意义。     

一种基于稀扩散燃烧的BUMP燃烧室及其对柴油机碳烟和NOx排放影响的实验研究

在壁面布置限流沿 (BUMP)后 ,撞壁射流从壁面被剥离 ,形成二次空间射流 ,可大大加快空气与流体的混合速率。基于此 ,设计了带有 BUMP的燃烧室 ,采用了可灵活控制喷油规律的 FIRCRI电控共轨式喷油系统进行了发动机实验。实验结果表明 :BU MP燃烧系统能显著降低 NOx 和碳烟排放 ,在平均有效压力为 0 .6 6 MPa(原机 5 0 %负荷 )时 ,烟度只有 0 .1BSU,NOx 为 42 0× 10 - 6;由于在缸内能够形成较均匀的混合气 ,缸内平均过量空气系数在 1.3～ 2 .0的范围内时 ,烟度一直保持在 0 .3BSU以下。实验还发现 BUMP的位置以及喷油定时对排放有重要影响。BUMP燃烧系统在降低 NOx 和碳烟排放方面显示了极大的潜力。     

Influence of coaxial air jet on mass diffusion of hydrogen jet injected through lobe-injector at supersonic flow

The technique of fuel injection in the combustion chamber is crucial for increasing the performance of hypersonic vehicles. This study tries to investigate the mechanism of fuel injection and distribution when fuel and air are injected through coaxial lobe injectors. The main attention of this work is to present the mechanism of fuel mixing of transverse jet injected from various lobe injectors. Comparison of coaxial gets (air and fuel jet) with equivalent simple jet (fuel without air jet) is done to achieve an efficient model for the combustion chamber. In this work, finite-volume is used to simulate and study of fuel injection performance of a transverse hydrogen jet in different lobe injectors. 3-D flow visualizations are done to reveal the mechanism of the fuel penetration and streamline pattern for introduced models. Strength of circulation and fuel mixing efficiency are also investigated in the present work for 2-, 3-, and 4-lobe nozzles. Our outcomes indicate that the mixing performance of coaxial air and fuel jet injected through the 3-lobe nozzle is about 25% better than other nozzle types. Our findings confirm that injection of air jet through the core of the lobe nozzle increases fuel mixing up to 200% at the combustion chamber.     

旋流冷壁燃烧室燃烧性能的数值分析

为进一步深化对中心空气射流及相关参数影响燃烧室性能变化规律的认识,采用雷诺应力模型(RSM)开展了有无中心空气射流、射流速度与射流孔径对燃烧效果影响的仿真研究。结果表明:增加空气中心射流以及改变相关参数能提高燃烧效率的主要原因在于湍流强度的增强改善了传热性能。壁面附近的协同角是影响旋流冷壁效果的重要因素,协同角越接近90°,越有利于获得较好的冷壁效果。     

"Bump燃烧室"内新概念稀扩散燃烧混合气形成机理的研究

基于自行研制的实验装置,用片状激光诱导荧光法(PLIF)对普通商用柴油喷雾的撞壁混合过程进行了实验研究,并用CFD数值分析软件对其进行了模拟计算,二者结果基本吻合．平板和实际燃烧室的实验及计算结果均表明,撞壁射流在遇到限流沿(Bump)后会剥离壁面,形成二次空间射流,扩大撞壁射流与空气的空间混合体积及混合速率,出现与周围空气迅速混合的“闪混”现象,减少壁面燃油堆积量．计算结果还表明,Bump的存在改变了缸内气流运动的流场结构,Bump附近旋向相反的“双涡结构”极大地增强了二次空间射流对周围空气的卷吸,促进了燃油与空气的混合,是Bump燃烧室内稀混合气形成及稀扩散燃烧的关键所在．     

CFD study on influence of fuel temperature on NOx emission in a HiTAC furnace

The influence of the fuel temperature on NOx formation was investigated numerically. For this purpose CFD modeling of NOx emission in an experimental furnace equipped with high temperature air combustion (HiTAC) system was studied. The comparison between the predicted results and measured values have shown good agreement, which implies that the adopted combustion and NOx formation models are suitable for predicting the characteristics of the flow, combustion, heat transfer, and NOx emissions in the HiTAC chamber. Moreover the predicted results show that increase of the fuel temperature results in a higher fluid velocity, better fuel jet mixing with the combustion air, smaller flame and lower NOx emission.     

Effect of hybrid coaxial air and hydrogen jets on fuel mixing at supersonic crossflow

In this research study, a computational method is applied to examine the impacts of coaxial hybrid air and fuel jets on fuel mixing at the supersonic cross-flow of Mach = 4. This study examined the coaxial air and fuel jet effects on main parameters i. e. circulation, mixing efficiency, and fuel penetration. Computational Fluid Dynamic is employed for the modelling of the coaxial jet at cross supersonic flow. Reynolds Average Navier-Stocks equations with SST turbulence model for achieving hydrodynamic feature of the main model. Impacts of air-jet pressure and nozzle configurations on fuel distribution are also presented and the main effective factors for efficient fuel mixing condition are explained. Our results disclosed that injection of coaxial air and fuel jets at supersonic cross airflow significantly improves the fuel penetration and mixing inside the combustion chamber. Flow study analysis shows that the coaxial injector augments the spiral feature of the fuel jet, which surges fuel mixing downstream. Our circulation analysis confirms that circulation strength increases in far away from an injector by the injection of a coaxial air jet.     

Effect of hydrogen percentage and air jet Reynolds number on fuel lean flame stability of LPG-fired inverse diffusion flame with hydrogen enrichment

The flame type studied in this paper is a circumferential-fuel – jet inverse diffusion flame, and the fuel is liquefied petroleum gas enriched with hydrogen gas. Fuel lean flame stability limit regarding to the volumetric percentage of hydrogen and the air jet Reynolds number was investigated. There were three flame stable-related limits examined: local extinction limit, restore limit, and complete extinction limit. Global Energy Consumption Rate of fuel, fuel jet velocity, and overall equivalence ratio of the air/fuel mixture at the three stable-related limits were presented. Experimental results indicate that with hydrogen addition, the inverse diffusion flame can sustain burning with a lower global energy than without it. The most significant stabilization effect was obtained with 30% hydrogen addition for complete extinction limit and 30%–90% for local extinction limit. The corresponding fuel jet velocity at complete extinction limit also decreases with hydrogen addition. However, fuel jet velocities at local extinction limit and restore limit increase significantly, when hydrogen percentage is larger than 70%. Air jet Reynolds number does not show notable influence on Global Energy Consumption Rate or fuel jet velocity at the three stability limits. In addition, overall equivalence ratio, which is an important parameter of inverse diffusion flame combustion dropping dramatically with air jet Reynolds number when it is less than 2000.     

限流沿燃烧室中实现柴油喷雾稀扩散燃烧的混合气形成过程

提出了一种在于激光诱导荧光法的实验方案，采用增压式共轨喷油器，在定容燃烧实验装置内进行柴油喷雾形成、发展、撞壁和混合过程的实验。实验发现，燃油喷雾在燃料室壁面的沉积可通过在壁面设置一个“限流沿”（BUMP），使之从壁面剥离，剥离后的壁面射流形成一个迅速扩散的二次空间射流，进而形成较均匀、较稀薄的混合气，它有利于减少碳烟和NOx排放。     

Free radical imaging techniques applied to hydrocarbon flames diagnosis

introductionThe current industrial needs for hydIDcrton-fuelcombushon systems involve simul~s assessllled ofdecreasing pollutal emissions, increasing equipmentlifetime and reducing fuel consumphon. withoutcompromising final PIDduct quality and Promotingflexible and clean Operation modes. Ih thes context,exhaust endssions chendcal composition have been arelevant issue for researchers and engineers, namelyunbumed hydrocboons and nitric and carbon Oboes,Which can direCtly or indireCtly hann e…     

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.