用双色法研究进气道喷射乙醇柴油引燃时的燃烧过程

利用高速彩色CCD摄像机的3个单色通道信息进行了双色法计算温度和KL因子的可行性研究，并用乙炔火焰对计算结果进行了验证，讨论了不同双色组合对测试精度的影响。在一台可视化发动机上对进气道喷射乙醇柴油引燃时的燃烧过程进行了分析，结果表明：随着乙醇喷入量的增加，燃烧火焰面积减小，温度及代表碳烟浓度的KL因子也相应下降，说明乙醇对柴油燃烧过程中碳烟的生成有抑制作用。     

气道和燃烧室形状对汽油机缸内流场影响的计算研究

为探究气道及燃烧室形状对汽油机缸内流场的影响,以某1.4L多点进气道喷射(MPI)汽油机为研究对象,利用AVL-FIRE软件对原机进气道形状进行稳态数值模拟计算,并对原汽油机在2 800r/min最低比油耗工况点进气及燃烧过程进行瞬态数值模拟计算。基于计算结果对进气道及燃烧室形状进行优化设计,提出4种计算方案,对优化前后各计算方案的缸内速度场、湍动能场、火焰前锋面密度和瞬时放热率进行对比分析。结果显示:改进气道的滚流比明显高于原机气道;结合改进气道,进气侧凸起活塞能够更好地维持滚流;在点火时刻,改进气道结合进气侧凸起活塞这一计算方案的缸内湍流分布及湍动能优于改进气道结合大曲率凹坑活塞、原机气道结合原机活塞(压缩比12)与原机计算方案,点火后火焰传播速度最大,燃烧速度最快。优化进气道及燃烧室形状能够加强缸内气流运动,提高点火时刻缸内湍流强度,加速火焰传播,改善燃烧过程。     

CO_2进气道和缸内喷射对柴油准HCCI燃烧的影响

通过开发的气体喷射系统,研究并对比了进气道和缸内喷射CO2对准均质压燃燃烧排放的影响.准HCCI燃烧由两段喷油实现.结果表明:随着缸内和进气道CO2循环喷射量的增大,缸内最高平均温度降低,燃烧相位推迟,最大压力升高率变化不大;NOX排放减小,HC和CO排放增大.等CO2喷射量下,NOx随着缸内CO2喷射始点的提前而减小;缸内喷射的HC和CO排放较进气道喷射的大.随着CO2循环喷射量的增大,进气道喷射的烟度开始变化不大,然后急剧上升;而缸内喷射的烟度变化不大.     

基于可视化温度场分析的柴油机缸内燃烧过程研究

在一台视窗上置式柴油机可视化实验装置上用高速摄像机记录下缸内燃烧过程的火焰照片,应用三基色法计算了缸内燃烧温度场.结果表明,用三基色法分析的缸内温度场分布与实际情况相一致；结合示功图曲线对柴油机着火和燃烧过程进行了分析,得到的结果符合柴油机实际着火和燃烧过程的发展规律.燃油在高温缺氧情况下会发生裂解形成较高温度的较大碳粒,影响相应零部件的使用寿命和发动机性能.     

复合喷射汽油机冷起动首循环颗粒物数量排放与失火控制

基于复合进气道喷射与缸内直喷两套喷射系统的汽油机,使用进气道喷射(PFI)、缸内直喷(GDI)及复合喷射(PDI)方式,研究不同喷射模式对汽油机冷起动首循环及前10循环的燃烧以及颗粒物数量排放的影响.研究结果表明:复合喷射可大幅降低直喷发动机冷起动首循环颗粒物数量排放;基于离子电流缸内诊断技术可实现冷起动首循环失火诊断与补火控制,避免失火,失火循环补火再燃后的颗粒物数量排放与GDI模式冷起动基本相同,但可避免HC排放恶化.     

双色法在内燃机燃烧诊断中的应用

系统介绍了双色法的测量原理,阐述国内外双色法在内燃机燃烧火焰分析方面的具体应用。经过多年研究,双色法已成功应用于柴油机燃烧诊断,利用燃烧火焰中实际存在的碳粒,可测量柴油机火焰的温度分布和碳烟浓度分布。汽油机属于无焰燃烧,燃烧过程只产生少量的碳烟,直接应用双色法具有较大难度,国内外可见文献较少,本文介绍了关于双色法汽油机测温的实例。     

缸内涡流比对冷起动燃烧火焰的影响探究

针对汽油发动机冷起动存在的燃烧不稳定、燃烧效率低的问题,基于单缸可视化发动机在冷起动工况下调节进气涡流,通过分析缸内燃烧火焰特性来探究增强进气涡流对发动机循环波动及输出功率的影响。试验所用发动机为单缸四气门(两进两出)缸内直喷汽油机,其中一个进气道加装有涡流控制阀,通过将一个进气道关闭或者开启来改变缸内涡流的强度。利用高速相机从活塞上的光学通道得到发动机缸内的火焰传播图像,并计算火焰传播面积,提取火焰边界,获取火焰中心速度及火焰扩散速度等信息,同时也利用燃烧分析仪对缸内压力、燃烧放热率等特性进行同步测量和记录,通过多角度的对比和分析揭示缸内燃烧状况与发动机宏观性能的相关联系,有效地发掘了在不同涡流强度下缸内火焰的传播特征。研究结果从缸内燃烧火焰的角度解释了提高涡流比能够很好地提高冷起动的燃烧稳定性,促进发动机缸内燃烧。研究表明,早期火核分布越集中,波动越小,后期循环波动就越小。试验结果还表明,由缸压计算的瞬时放热率与火焰面积存在很好的线性关系。     

基于LS-SVM的燃煤电站锅炉变工况运行负荷预测

提出了一种基于最小二乘支持向量机理论及可视化火焰检测系统的燃煤电站锅炉负荷预测的方法.利用可视化火焰检测系统对300 MW燃煤锅炉降负荷过程的燃烧火焰及温度场进行了实时测试.通过测试,利用数字图像处理技术提取了燃烧火焰图像特征参数、由双色法测温原理计算得到了其温度场,采用最小二乘支持向量机建立了锅炉负荷预测模型并进行了校验.结果表明.该预测模型泛化能力强、预测精度高,从而为把燃烧火焰图像及温度场信息作为控制信号,进而引入电站锅炉燃烧控制系统提供了技术支持.     

燃用直喷汽油-预混醇混合气的汽油机燃烧特性

通过进气道喷射乙醇/正丁醇方式形成预混醇混合气,通过缸内直喷汽油方式形成分层汽油混合气,研究了相同循环供油总能量下汽油机的燃烧与排放特性.结果表明,在进气过程直喷汽油时,汽油机的平均指示有效压力和指示热效率均高于在压缩过程中直喷汽油时的值,并且前者的碳氢化合物和一氧化碳排放更低.在进气过程中直喷汽油时,进气道喷醇-直喷汽油方式与仅采用进气道喷醇方式下汽油机的指示热效率相近.进气道喷乙醇-直喷汽油(E-GDI)和进气道喷正丁醇-直喷汽油(B-GDI)混合气形成方式下汽油机的效率与排放优于仅采用汽油直喷(GDI)形成混合气方式下的值,而且E-GDI方式下汽油机的指示热效率最高.直喷汽油压力对汽油机燃烧的影响与汽油直喷时刻有关.汽油直喷时刻越早,它对汽油机平均指示有效压力的影响越小.     

燃烧系统结构对中载汽油机爆震边界内燃烧的影响

针对中载汽油机,设计开发了4种进气道和燃烧室的匹配方案,通过数值模拟的方法研究了不同燃烧系统结构对缸内宏观流场、湍流场及爆震边界内燃烧的影响。结果表明:进气道和燃烧室结构对缸内宏观流场及湍流场演化有显著影响。初期火焰传播速度主要由火花塞周围气流的平均速度决定,而主燃烧阶段的燃烧速度与该区域的湍动能大小成正比。双切向进气道匹配中置倒楔形燃烧室能够同时提高湍流强度及气流速度,从而有效缩短滞燃期及燃烧持续期,但其爆震倾向严重。采用复合进气道匹配中置倒楔形燃烧室的方案可显著抑制爆震,提前点火时刻,燃烧速度较快,可明显降低燃烧损失,提升中载汽油机的性能。     

Theoretical investigation of flame propagation process in an SI engine running on gasoline–ethanol blends

Turbulent flame propagation process in a spark-ignition (SI) engine is theoretically investigated. Fueling with gasoline, ethanol and different gasoline–ethanol blends is considered. A quasi-dimensional SI engine cycle model previously developed by the author is used to predict the thermodynamic state of the cylinder charge during the cycle. The flame is assumed to be spherical in shape and centered at the spark plug. Computations are carried out for an automobile SI engine having a disc-shaped combustion chamber, for which the compression ratio and the nominal speed are 9.2 and 5800 rpm, respectively. Geometrical features (flame radius, flame front area and enflamed volume) of the flame, combustion characteristics (mass fraction burned and burn duration), and cylinder pressure and temperature are predicted as a function of the crank angle. Three different positions of the crank angle are studied: −10°, TC and +10°. It was concluded that ethanol addition to gasoline up to 25 vol% accelerated the flame propagation process.     

Investigation on characteristics of ionization current in a spark-ignition engine fueled with natural gas–hydrogen blends with BSS de-noising method

Investigation on ionization current characteristic in a spark-ignition engine fueled with natural gas, natural gas–hydrogen bends and gasoline was conducted. Blind Source Separation (BSS) de-noising method is employed to separate the ionization current signal from the interference of spark tail generated by ignition discharge. Cylinder pressure was recorded, and local temperature at spark plug gap is calculated using AVL-FIRE simulation code. Results show that the simulated cylinder pressures are in good agreement with those of measured and the spark tail and ionization current can be separated using BSS method. Front flame stage and post flame stage in ionization current can be used to analyze the combustion characteristics of natural gas–hydrogen blends. De-noised current shows that the appearance of front flame stage and post flame stage (including the peaks in the stages) fueled with natural gas is postponed and compared with that fueled with gasoline, and the appearance of front flame stage and post flame stage advance with the increase of hydrogen fraction in natural gas–hydrogen blends. In addition, the amplitude of ionization currents in both front flame and post flame (including the two peaks) fueled with natural gas gives lower values compared with those fueled with gasoline and hydrogen addition can increase the amplitude. Maximum post flame current shows similar trend to maximum cylinder pressure and it has good correlation between the timing of maximum post flame current and the timing of maximum cylinder pressure. High correlation coefficient between maximum post flame current and maximum pressure is presented.     

汽油转子发动机燃烧过程模拟技术研究

建立了汽油转子发动机燃烧过程的数学模型;基于实验数据,考察了往复式汽油机湍流燃烧速率计算经验式在汽油转子发动机中应用的不适用性,并对其进行了修正;将建立的燃烧模型和修正后的湍流燃烧速率计算公式用于预测汽油转子发动机燃烧室内气体压力和平均指示压力,预测与测量结果基本吻合。结果表明：建立的汽油转子发动机燃烧过程数学模型和修正后的湍流燃烧速率计算公式准确,可用于汽油转子发动机性能模拟研究。     

汽油机射流燃烧系统火焰传播过程的研究

根据汽油机燃烧火焰电离原理,试制成功了一台火焰传播测试仪。由于火焰前锋内离子浓度的变化将引起电位差的相应变化,所以通过装在气缸盖上的传感器,可使仪器显示出火焰到达燃烧室中某一位置的时刻和燃烧的持续时间。如用微机采样,则可同时检测３２ 个点,也可以用示波器显示任一个传感器输入的电位差变化波形。用此仪器对４９２ Ｑ Ｓ汽油机进行了火焰传播过程的测试,从中可看出射流燃烧系统燃烧过程的特点,有利于今后进一步改进此系统并实现一台性能更好的发动机。     

Spatial combustion analysis of biodiesel fueled engine using combustion chamber endoscopy and modeling

Main objective of this study was to demonstrate endoscopic visualization of combustion events in the combustion chamber of a production grade compression ignition (CI) engine. High speed endoscopic imaging was used to provide qualitative information about the in–cylinder combustion for mineral diesel and biodiesel fueled engine operating at different engine loads. These images were analyzed using image processing program developed in MATLAB, in order to determine the ‘start of combustion’ (SoC), ‘spatial soot distribution’ and ‘spatial flame temperature distribution’. In–cylinder pressure and rate of heat release (RoHR) were validated using simulation results obtained by using a KIVA-3V code. The luminosity of flames in the combustion images was relatively lower for biodiesel compared to baseline diesel. Area of soot distribution decreased in later stages of combustion for both test fuels, which indicated superior oxidation of soot particles formed, during the post combustion events. Biodiesel showed relatively lower dissipation of heat, which caused lower soot radiations in the flames. Simulated soot distribution and flame temperature distribution obtained from KIVA-3V code also showed similar behavior and verified the trends observed by combustion chamber endoscopy.     

Investigating the effects of LPG on spark ignition engine combustion and performance

A quasi-dimensional spark ignition (SI) engine cycle model is used to predict the cycle, performance and exhaust emissions of an automotive engine for the cases of using gasoline and LPG. Governing equations of the mathematical model mainly consist of first order ordinary differential equations derived for cylinder pressure and temperature. Combustion is simulated as a turbulent flame propagation process and during this process, two different thermodynamic regions consisting of unburned gases and burned gases that are separated by the flame front are considered. A computer code for the cycle model has been prepared to perform numerical calculations over a range of engine speeds and fuel–air equivalence ratios. In the computations performed at different engine speeds, the same fuel–air equivalence ratios are selected for each fuel to make realistic comparisons from the fuel economy and fuel consumption points of view. Comparisons show that if LPG fueled SI engines are operated at the same conditions with those of gasoline fueled SI engines, significant improvements in exhaust emissions can be achieved. However, variations in various engine performance parameters and the effects on the engine structural elements are not promising.     

生物柴油碳烟特性的可视化研究

在1台光学可视化发动机上,采用高速摄影法,对不同掺混比例的柴油/生物柴油混合燃料进行研究,获取缸内燃烧火焰图像,通过双色法得到表征缸内碳烟总体分布的KL因子,分析了生物柴油对缸内燃烧过程和碳烟生成特性的影响.研究结果表明,随着生物柴油掺入比例的增加,最高燃烧压力逐渐降低,滞燃期相对延长,燃烧持续期缩短,火焰的亮度和分布面积都随之下降.KL因子的最高浓度降低,碳烟较浓的分布区域减小,碳烟的氧化进程加快.