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。     

柴油/汽油双燃料准均质燃烧过程及其降低有害排放物的潜力

常规柴油机受扩散过程控制，由于存在局部高温和局部浓混合气，NOx和微粒排放较高。为了解决这一问题，提出了用柴油/汽油双燃料方式实现准均质燃烧过程（QHCCI）的方案。将一台自然吸气的N485柴油机通过增加一套自行开发的汽油多点喷射系统，履行成实验样机。实验研究表明，这种燃烧方式保留了柴油机良好的燃油经济性，与原机相比，HC、CO排放高，而NOx与微粒排放具有在自然吸气条件下实现欧洲II标准的潜力。     

天然气发动机混合气形成与燃烧特点及性能评述

本文根据天然气发动机混合气的形成特点,把天然气发动机分为预混合燃烧型和非均质扩散燃烧型,并分析了这两种天然气发动机的技术特点、燃烧特点与排放等性能。本文重点介绍了实现非均质扩散燃烧的不同型式高压缸内直喷天然气发动机技术及其性能特点,最后提出非均质扩散燃烧天然气发动机技术需要研究的相关问题。     

大气温度对某型燃气轮机燃烧稳定性和 NOx排放影响的数值研究

为了对比扩散和预混两种不同燃烧模式下大气温度对燃气轮机燃烧稳定性和NO_x排放的影响规律,针对某重型燃气轮机燃烧室,对多旋流喷嘴燃烧室的燃烧稳定性和NO_x排放进行了数值研究。结果表明:对于扩散燃烧,大气温度升高,燃烧室内高频脉动增强,燃烧稳定性变差;对于预混燃烧,大气温度升高,有利于提高燃烧的稳定性;在扩散燃烧模式下燃烧室燃料喷嘴下游回流区的温度最高,NO_x生成量最大;预混燃烧下燃烧室头部温度分布较均匀,燃烧室NO_x生成主要集中在驻涡回流区和燃烧室中下游位置,燃料喷嘴下游回流区NO_x生成量很小;随着大气温度的升高,扩散燃烧和预混燃烧下燃烧室内NO_x的生成量均增加。研究结果可为指导燃气轮机运行提供参考。     

气道喷射汽油机缸内燃烧过程的可视化研究

利用光学单缸机和高速摄像系统,研究了喷油正时对气道喷射汽油机暖机工况缸内燃烧过程的影响,并从不同喷油正时对缸内混合气形成影响过程出发,解释了出现的缸内燃烧现象。研究结果表明,气道喷射汽油机在暖机工况缸内燃烧过程会出现较多的扩散燃烧现象;不同喷油正时对应的雾化和燃油进入缸内的机理不同,所形成的混合气质量也有较大差异,导致出现不同的燃烧现象;在排气行程晚期、进气行程早期和压缩行程中期进行燃油喷射,缸内混合气燃烧过程中出现扩散燃烧现象较少。     

低排放分级燃烧器中CH4燃烧特性

烟气回流是实现柔和燃烧的手段,为精确控制回流比例,建立了分级燃烧器,实验研究了回流比例、当量比对CH4柔和燃烧火焰形态和NO、CO排放的影响。当量比为0.8,回流比例为0.6～0.7时实现柔和燃烧,反应区分散不分层,烟气中NO和CO体积分数分别小于1.2×10-5和4×10-5;回流比例过小时发生扩散燃烧,过大时燃烧不稳定;NO排放主要在烟气发生区产生。回流比例为0.6、当量比为0.6～0.8时,射流和主流有效掺混并伴有火焰抬升,实现柔和燃烧;相同当量比时,分级燃烧的NO排放较旋流扩散低,当量比0.8时,分级燃烧相对旋流扩散减排NO达44%。     

GT13E2燃气轮机混合-预混燃烧模式切换优化

介绍了GT13E2燃气轮机燃烧系统和脉动检测装置,结合GT13E2燃气轮机厂家提供的实验室研发数据,通过升负荷燃烧模式切换调试试验,对切换时的燃气轮机相对额定负荷点和扩散燃烧延时退出时间这两个参数进行了优化;通过降负荷燃烧模式切换调试试验,对切换时的燃气轮机相对额定负荷点,燃烧模式切换指令激活后主预混燃烧延时退出时间、辅助预混燃烧延时投入时间和扩散燃烧天然气流量从零增加到燃烧模式切换后流量所用时间这四个参数进行了优化,优化后的参数有效提高了燃气轮机燃烧模式切换过程中燃烧的稳定性和运行安全可靠性。     

湿度对HAT循环燃烧室旋流扩散燃烧特性的影响

为研究湿度对燃烧特性的影响,采用湍流雷诺应力模型和层流小火焰模型,对湿空气透平(HAT)循环燃气轮机带有旋流器的燃烧室内甲烷扩散燃烧过程进行了数值模拟对比了在4种不同空气含湿量(0、100、200、300g／kg(DA))情况下的燃烧室内部温度场、速度场以及NO组分分布的情况,分析了湿度对HAT循环燃烧室扩散燃烧特性的影响结果表明,加湿降低了整个燃烧室的温度,并使其内部温度分布更加均匀;加湿使燃烧室的NO浓度大大降低;加湿减小了回流区长度。     

预测直喷式柴油机燃烧率经验公式的研究

４区现象学燃烧模型可由实测示功图预测直喷式柴油机的燃烧率及ＮＯｘ排放并具有较高的精度。为使该种模型适用于热力过程的优化模拟，本文由多种燃烧系统及工况的匹配实验数据推导出了预测直喷式柴油机燃烧率的经验公式。应用该式分别以不同韦全函数对预混合及扩散燃烧阶段进行了计算。研究结果表明，预测结果与实测结果是相当吻合的。     

预混合比例实时优化控制正庚烷复合HCCI燃烧

在一台单缸柴油机上试验研究了预混合比例对正庚烷复合HCCI燃烧的影响,并在各个负荷下实现预混合比例的优化控制.结果表明:复合HCCI燃烧呈现三阶段放热模式,并且随着预混合比例的增大,复合HCCI燃烧第2阶段高温反应着火提前,燃烧持续期缩短,第3阶段扩散燃烧滞燃期缩短,同时缸内最高压力和最大压力升高率均升高.复合HCCI的NOx排放与直喷相比显著降低,且随预混合比例的增大先降低后升高.同时,复合HCCI的CO排放随预混合比例增大先增大后减小,而HC则随预混合比例增大而增大.通过预混合比例优化控制,复合HC-CI燃烧能够显著拓展负荷范围,并且保持较高的热效率.     

A spherical cell model for multi‐component droplet combustion in a dilute spray

A model for sphericosymmetric thin‐flame combustion of a multi‐component fuel droplet in a dilute spray has been developed using a unit cell approach. The gas‐phase transport has been modelled as convective–diffusive while the liquid‐phase processes as transient–diffusive. Convective heat and mass transfer condition has been used at the cell surface. The results indicate that evaporation and combustion characteristics of the droplet are strongly affected by the variation of both ambient conditions and convective transfer coefficients. Using the model, the effects of droplet spacing in spray, ambient oxidizer concentration, ambient temperature and pressure have been considered. Droplet life increases with decrease in droplet spacing, ambient temperature and ambient oxidizer concentration. However, droplet life has a weak dependence on ambient pressure. Copyright © 2001 John Wiley & Sons, Ltd.     

激波风洞中超声速燃烧现象的初步实验研究

激波风洞可以提供超声速燃烧现象研究需要的高速和高温实验模拟条件,而且在实验时间上优于膨胀管和重活塞风洞,但是由于其技术难度,很少用于超声速燃烧现象研究。文章介绍了启用激波风洞进行燃烧研究所作的改造和得到的初步实验结果。实验除测量常规流场参数和模型表面的动态参数外,主要使用二维实验模型,利用高温气体的自发光和燃烧伴随的发光现象,采用高速摄影技术来观测燃烧现象,记录到高焓流场中叠加燃料喷射和燃烧的流场,观察到自由边界条件下扩控制的超声速燃烧现象。结果表明激波风洞用于超声速燃烧研究的一些必要的技术问题已基本解决。     

Performance and emission characteristics of QHCCI dimethyl ether engine

Experimental investigation into the effects of different pilot amounts of dimethyl ether (DME) on the performance and emission of a single-cylinder direct-injection DME engine is conducted. The results show that a DME engine can operate at a wider range of speeds and loads at quasi-homogenous charge compression ignition (QHCCI) mode. The brake thermal efficiency increases while the exhaust temperature decreases. NO_x emission decreases by about 30%–50% although there is a slight increase in HC and CO emissions. NO_x, HC and CO emissions increase with an increase in the amount of DME pilot. QHCCI is a good way to increase thermal efficiency and decrease NO_x emission.     

A catalytic burner using propane and toluene alternately for the drying of textile coatings

This study aims to develop a low‐temperature catalytic burner using propane and toluene alternately as a fuel and to apply it to the drying of acrylic coatings on textiles. Pt catalysts deposited on ceramic fibres (Al₂O₃) were employed. For propane, the diffusive catalytic burner was used. The combustion efficiency of the diffusive catalytic burner deteriorated rapidly when it was installed in a downward position. Two concepts of forced diffusion combustion and premixed combustion were introduced to improve the downward placed diffusive catalytic burner. The combustion efficiency was enhanced with these modifications, but the forced diffusion was preferred since premixed combustion raised the temperature of the catalyst above 700°C leading to sintering of the catalyst. For the toluene catalytic burner the premixed combustion mode was adopted. Its optimum operation conditions were obtained by analyzing the temperatures within the catalyst layer and by adjustment of the toluene mixture. Field tests were performed on the drying acrylic coatings using the catalytic burners. The results showed that the use of catalytic burners had several benefits such as energy savings and less pollutant emissions. Copyright © 1999 John Wiley & Sons, Ltd.     

A theoretical study of quasisteady sphericosymmetric combustion of alcohol droplets

A distinct characteristic of alcohol droplet combustion is absorption of moisture, generated as combustion product, during early part of the droplet life. A theoretical model for combustion of alcohol droplets has been developed. The quasisteady sphericosymmetric gas phase equations have been solved analytically while the transient diffusive liquid phase equations have been solved numerically. It is observed that neglecting the effect of moisture absorption in combustion modelling leads to underprediction of droplet life and overprediction of flame temperature and flame stand-off ratio. The results show that for alcohols with boiling points lower than that of water, a significant amount of moisture, generated during combustion is absorbed by the droplet. Absorption of this moisture prolongs droplet life and reduces flame temperature. A similar effect is also observed with increasing initial moisture content in the droplet.     

Numerical studies of heterogeneous reaction in stagnation flows using one-dimensional and two-dimensional Cartesian models

Flow over a thin strip is one of the major experimental configurations in the study of catalytic combustion. 1D laminar stagnation-flow models are generally employed to investigate the catalytic combustion characteristics in this experimental configuration. In this study, a 2D Cartesian model is developed to examine the conditions under which 1D models are applicable. The results show that the 1D model is only appropriate in the experimental configurations with a length-to-width ratio less than 1 to 3 (depending on the flow conditions). The 1D model failed because of the neglecting of transverse diffusive mass transfer (at Re < 30) and of the oversimplified convective mass transfer (at Re > 60). The calculations of the 1D and 2D models are also compared against the OH measurements performed in a typical stagnation-flow reactor with a length-to-width ratio of 16. The results show that the computations of the 2D model are in better agreement with the experimental data.     

低重力下典型固体燃料的火焰特征及燃烧速率

利用实验时间为2.2,s,低重力水平为10-2,g0简易实验系统,对易升华典型固体燃料试样从常重力到低重力环境过渡的瞬态燃烧过程进行了实验研究,考察了火焰形态、火焰亮度和温度以及燃料试样燃烧速率受重力水平影响的变化趋势.结果表明,随着重力水平的变化,火焰从常重力环境中的湍流扩散火焰,过渡为低重力环境中的层流火焰,火焰高度、亮度和温度以及燃烧速率都随重力水平的下降而降低.由于进入低重力状态后,常重力燃烧诱导的空气流动并没有完全消失,观察到了逆风侧火焰温度、火焰平均亮度,以及燃烧速率因气流作用而回升的现象,这种现象会使低重力环境中的火灾复杂性和危害性增强.     

燃烧反应干熄炉内传热模拟的浅析

建立了干熄炉内焦炭层床循环气体的传热模型,并耦合燃烧反应计算,分析了干熄炉冷却室内的温度变化,计算结果与实测数据基本一致。本文还进一步分析了化学反应活化能、风料比和燃烧反应对干熄炉内传热的影响,以期为干熄炉的优化设计提供一定参考。