用光纤燃烧传感器测量汽油机的燃烧时间参数的研究

本文介绍了一个光纤燃烧传感器及ＯＭＡ４光多通道分析仪组成的测量系统，用以测量汽油机燃烧火焰光谱。光谱分析结果再次证实了燃烧火焰中ＣＨ（４３１．５ｎｍ），Ｃ２（５１６．５ｎｍ），Ｈ２Ｏ（５８９ｎｍ）等自由基的特征光谱同Ｃ粒子的热辐射连续光谱叠加在一起，构成了火焰光谱。根据光谱曲线中Ｈ２Ｏ光强峰值变化，可以确定汽油机燃烧过程中重要的时间参数：着火延迟期和燃烧持续期。由于汽油机燃烧循环变动大，与单色仪和ＢＯＸＣＡＲ积分平均器组成的测量系统相比，光纤燃烧传感器＋ＯＭＡ４用光多通道分析仪系统测量汽油机燃烧火焰光谱，测量精度高，工作效率高。     

废气再循环降低汽油机NOx排放的实验研究及其微机控制系统的设计

为大幅度降低汽油机ＮＯｘ排放，同时使发动机动力性，经济性，ＨＣ和ＣＯ排放及工作稳定性基本不变，采用废气再循环，导气屏组织进气涡流加快燃烧速率和多火花点火助燃措施，在ＥＱ６１００汽油机上进行试验研究。根据实验结果，制作了不同工况下最佳废气再循环率的脉谱，并以８０３１芯片为核心，脉谱为依据，设计出一种能付诸实用的车用发动机废气再循环控制系统。     

火花点火发动机的 HC 排放

本文综合国外火花点火发动机ＨＣ排放领域的研究成果，对发动机燃烧过程中部分燃料脱离主燃段及其在发动机缸内和排气系统内的不完全氧化和传输机理加以分析和讨论。总结了发动机在稳定工况和冷起动工况下ＨＣ排放形成的主要原因。     

二冲程汽油机着火时刻的火焰光谱分析

二冲程汽油机排气污染严重，尤其是燃烧混合油、浓混合气时有害物排放量大，着火时刻火焰光谱分析表明，ＣＨ９４３１．５ｍｍ）及Ｃ２（５１６．５ｍｍ）自由基光强峰值比较强，尤其是ＣＮ（３８７ｎｍ）自由基光强峰值比较突出。根据Ｆｅｎｉｍｏｒｅ机理可以解释排气中ＮＯＸ的生成机理。     

再燃燃料中HCN对NO_x还原的影响

燃烧再燃是降低ＮＯｘ排放的一项重要的炉内措施。通过对再燃区不同的空气过量系数和再燃温度条件下的数值计算,研究了用含有ＨＣＮ的天然气（ＣＨ４）作为再燃燃料的再燃过程。研究发现,再燃燃料中含氮组分的存在,以及再燃区的工况条件都对ＮＯｘ的还原率有很大的影响。因此,在实施降低ＮＯｘ排放的再技术过程中,应当根据实际情况对再燃区的燃烧工况进行优化,选择合适的再燃区温度和空气过量系数。     

汽油载重车排放净化研究

采用试验方法，研究载重车汽油机在使用过程中，由于气缸磨损和水套冷却状况的变化造成尾气排放中的ＨＣ和ＣＯ排放量增加，采用引入旁通空气和控制各气缸混合气空燃比的措施后，致使运行的载重其汽油机的ＨＣ和ＣＯ排放得到很好的控制。     

492WQB汽油机排放的缸间差异研究

对４９２ＷＱＢ汽油机的每个试验工况从各缸排气道出口中心附近进行了连续１０ｓ共９０次的采样,对采样气体中ＮＯｘ、ＨＣ及ＣＯ的浓度分别采用了化学发光法、氢火焰离子法及不分光红外法进行了分析,并把连续采样气体的排放平均值作为每个测试工况的排放值。试验结果表明,各缸空燃比等的微小差异,引起的各缸ＮＯｘ、ＨＣ及ＣＯ排放的最高值与最低值比可达１０倍、５倍及６倍;缸间排放差异随着点火时间、转速、节气六开度、混合     

电控摩托车汽油机排放特性的试验研究

利用MicroEFI电喷系统开展了摩托车汽油机在怠速工况和常用部分负荷工况下的排放研究。结果表明采用隔次喷射技术、点火优化以及稀混合燃烧可使怠速工况HC排放下降68％左右、CO下降60％左右，在部分负荷工况下的HC排放下降30％～40％、CO下降20％～60％、NOx下降30％～50%。     

咨询服务

１ 如何降低柴油机的排气污染？ 答：同汽油机比较，柴油机的平均过量空气系数大，燃烧比较完全，ＣＯ、ＨＣ、ＮＯｘ的排出量相对较少。但柴油机中ＳＯ２和碳烟的排出量却比汽油机大得多。目前，柴油机净化的工作重点是降低ＮＯｘ、ＨＣ的合计排出量和减少碳烟。 柴油机燃烧室的型式对排污量影响很大，分隔式燃烧室排污量比直喷式低得多。采用分隔式燃烧室时，副燃烧室中的混合气浓度较大，且燃烧温度峰值较低，对ＮＯｘ的形成不利。而当燃油及燃烧气体喷到主燃室进行二次燃烧时，又由于大量空气的冷却作用，活塞又开始下移，燃烧最高温度…     

汽油机燃烧沉积物对发动机性能影响的研究

本介绍了作在一台４９２Ｑ型汽油机上进行燃烧沉积物对发动机性能影响的研究结果，发现燃烧沉积物导致发动机压缩比提高，废气排放中ＮＯｘ、ＨＣ排放增多并导致发动机充气效率下降，此外还分析了燃烧沉积物影响发动机性能的主要原因。     

LPG点燃式发动机冷起动首循环进气富氧试验研究

基于循环控制,详细研究了LPG点燃式发动机冷起动首循环进气富氧的燃烧及排放特性。试验在一台电控LPG进气喷射单缸风冷四冲程125 mL发动机上进行,采用膜式富氧方法实现富氧进气燃烧。研究表明:当过量空气系数大于0．7时,富氧进气燃烧缸压峰值与空气相比增加不显著,此后随混合气加浓,富氧进气燃烧缸压峰值开始明显大于常规空气进气燃烧;过量空气系数在0．4～0．876时,富氧进气燃烧与常规空气进气燃烧相比,HC排放没有较大降低,在此范围之外,富氧显著降低HC排放;过量空气系数在0．4～0．7,富氧与空气相比CO显著降低;富氧进气燃烧,使得首循环NO排放大幅增加;计算放热率发现,富氧燃烧速度比常规空气进气燃烧更快,放热更集中。     

Effects of intake air temperature on SI engine emissions during a cold start

This paper presents the concept of preheating the intake air to reduce cold-start emissions from gasoline engines. The effects of intake air temperature on emissions from a gasoline engine were studied by using an air heater based on spark ignition. A light-duty vehicle test of cold-start emissions was carried out at an ambient temperature of?7°C according to New European Driving Cycle for Euro 3 and Euro 4 exhaust emission legislations. The results showed that preheating the intake air could effectively reduce both hydrocarbon (HC) and carbon monoxide (CO) emissions and improve fuel economy during a cold start. During idling conditions, the key phase of the HC and CO emissions was the first 40 s. With the aid of the air heater, cold-start HC and CO emissions from the vehicle were lower than the limit values in the Euro 3 and Euro 4 regulations.     

Combustion and emissions performance of a hybrid hydrogen–gasoline engine at idle and lean conditions

Due to the narrow flammability of gasoline, pure gasoline-fueled spark-ignited (SI) engines always encounter partial burning or even misfire at lean conditions. Gasoline engines tend to suffer poor combustion and expel large emissions at idle conditions because of the high variation in the intake charge and low combustion temperature. Comparatively, hybrid hydrogen engines (HHE) fueled with the mixtures of hydrocarbon fuels and hydrogen seem to achieve lower emissions and gain higher thermal efficiencies than the original hydrocarbon-fueled engines due to the wide flammability and high flame speed of hydrogen. Since a HHE only requires a small amount of hydrogen, it also removes concerns about the high production and storage costs of hydrogen. This paper introduced an experiment conducted on a four-cylinder SI gasoline engine equipped with a hydrogen port-injection system to explore the performance of a hybrid hydrogen–gasoline engine (HHGE) at idle and lean conditions. The injection timings and durations of hydrogen and gasoline were governed by a hybrid electronic control unit (HECU) developed by the authors, which can be adjusted freely according to the commands from a calibration computer. During the test, hydrogen flow rate was varied to ensure that hydrogen volume fraction in the intake was constantly kept at 3%. For the specified hydrogen addition level, gasoline flow rate was reduced to make the engine operate at idle and lean conditions with various excess air ratios. The test results demonstrated that cyclic variations in engine idle speed and indicated mean effective pressure were eased with hydrogen enrichment. The indicated thermal efficiency was obviously higher for the HHGE than that for the original gasoline engine at idle and lean conditions. The indicated thermal efficiency at an excess air ratio of 1.37 was increased from 13.81% for the original gasoline engine to 20.20% for the HHGE with a 3% hydrogen blending level. Flame development and propagation periods were also evidently shortened after hydrogen blending. Moreover, HC, CO and NOx emissions were all improved after hydrogen enrichment at idle and lean conditions. Therefore, the HHE methodology is an effective and promising way for improving engine idle performance at lean conditions.     

Starting a spark-ignited engine with the gasoline-hydrogen mixture

Because of the increased fuel-film effect and dropped combustion temperature, spark-ignited (SI) gasoline engines always expel large amounts of HC and CO emissions during the cold start period. This paper experimentally investigated the effect of hydrogen addition on improving the cold start performance of a gasoline engine. The test was carried out on a 1.6-L, four-cylinder, SI engine equipped with an electronically controlled hydrogen injection system. A hybrid electronic control unit (HECU) was applied to control the opening and closing of hydrogen and gasoline injectors. Under the same environmental condition, the engine was started with the pure gasoline and gasoline-hydrogen mixture, respectively. After the addition of hydrogen, gasoline injection duration was adjusted to ensure the engine to be started successfully. All cold start experiments were performed at the same ambient, coolant and oil temperatures of 17 °C. The test results showed that cylinder and indicated mean effective pressures in the first cycle were effectively improved with the increase of hydrogen addition fraction. Engine speed in the first 20 start cycles increased with hydrogen blending ratio. However, in later cycles, engine speed varied only a little with and without hydrogen addition due to the adoption of close loop control on engine speed. Because of the low ignition energy and high flame speed of hydrogen, both flame development and propagation durations were shortened after hydrogen addition. HC and CO emissions were dropped markedly after hydrogen addition due to the enhanced combustion process. When the hydrogen flow rate increased from 0 to 2.5 and 4.3 L/min, the instantaneous peak HC emissions were sharply reduced from 57083 to 17850 and 15738 ppm, respectively. NOx emissions were increased in the first 5 s and then reduced later after hydrogen addition.     

怠速工况发动机富氧燃烧排放及其稳定性研究

利用氧的体积分数为21%～27%的富氧空气进气,研究点燃式发动机启动后最初怠速工况排放特性和规律.试验表明,在氧的体积分数为23%～25%的低富氧程度下,CO、HC排放降低作用更加显著,同时NOx排放升高程度处于较低水平.相反,在高富氧浓度下,CO、HC排放降低程度明显减小,NOx排放大幅提高.因此,低富氧浓度在改善发动机怠速工况燃烧排放中具有重要作用和应用潜力.研究还表明,随着供气氧的体积分数的增加,压力峰值提高,相位提前,发动机循环变动减小.进气氧的体积分数对瞬时转速循环变动性影响是有限度的,23%左右的低富氧作用最为明显,随着富氧程度增加,作用逐渐减小.     

基于符号序列的汽油机瞬态排放分析

本文对符号时间序列方法进行了说明,使用此方法分析两种汽油发动机瞬态排放中的HC和CO,结合排放值,在它们之间进行对比分析,提出新的评价参数,进而可以评价它们的燃烧状况。     

燃烧参数对汽油/柴油双燃料HPCC性能和排放影响的试验

在一台改造的单缸柴油机上,转速为1,500,r/min、平均指标压力为0.9,MPa工况进行了不同参数对汽油/柴油双燃料高比例预混合低温燃烧(HPCC)方式燃烧和排放性能影响的试验研究.结果表明,调整EGR率和汽油比例可实现HPCC燃烧过程优化,在保持发动机高燃油经济性的前提下使NOx和碳烟(Soot)排放大幅降低;进气压力对Soot的影响不明显,但进气压力过低将限制汽油比例的提高,NOx排放偏高,进气压力过高使燃烧效率和热效率降低;提高柴油喷油压力,滞燃期延长,最大压升率及最大爆发压力降低;提高喷油压力可同时降低NOx和Soot排放,但喷油压力对燃烧效率、指示油耗、HC和CO排放影响不大.在HPCC燃烧中,通过优化EGR率、汽油比例、进气压力和柴油喷油压力,在不使用后处理器的前提下可使NOx和Soot排放分别低于0.4,g/(kW.h)和0.003,g/(kW.h),并保持较高的热效率,但HC和CO排放偏高,需要采用有较高转换效率的氧化后处理器加以解决.     

火花点火发动机碗形燃烧室的设计与研究

本文介绍了在同一台单缸汽油试验机上分别采用浴盆形和压缩比不同的碗形燃烧室进行动力性、经济性、排放指标和燃烧过程分析的对比试验研究。结果表明，采用碗形燃烧室，发动机的总燃烧期缩短，循环变动下降，适合采用较高的压缩比。在排放指标大致相当的条件下，动力性改善，节油效果达１０％以上，具有良好的实际应用价值。在国产汽车发动机向小缸径、高转速、高压缩比的方向发展时，采用碗形燃烧室将会取得良好的效果     

Effect of addition of hydrogen and exhaust gas recirculation on characteristics of hydrogen gasoline engine

The effects of exhaust gas recirculation (EGR) on combustion and emissions under different hydrogen ratios were studied based on an engine with a gasoline intake port injection and hydrogen direct injection. The peak cylinder pressure increases by 9.8% in the presence of a small amount of hydrogen. The heat release from combustion is more concentrated, and the engine torque can increase by 11% with a small amount of hydrogen addition. Nitrogen oxide (NOx) emissions can be reduced by EGR dilution. Hydrogen addition offsets the blocking effect of EGR on combustion partially, therefore, hydrogen addition permits a higher original engine EGR rate, and yields a larger throttle opening, which improves the mechanical efficiency and decreases NOx emissions by 54.8% compared with the original engine. The effects of EGR on carbon monoxide (CO) and hydrocarbon (HC) emissions are not obvious and CO and HC emissions can be reduced sharply with hydrogen addition. CO, HC, and NOx emissions can be controlled at a lower level, engine output torque can be increased, and fuel consumption can be reduced significantly with the co-control of hydrogen addition and EGR in a hydrogen gasoline engine.     

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions of a gasoline/hydrogen SI engine

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions was presented for a gasoline/hydrogen SI engine. Three kinds of injection modes (gasoline, gasoline plus homogeneous hydrogen and gasoline plus stratified hydrogen) and five excess air ratios were applied at low speed and low load on a dual fuel SI engine with hydrogen direct injection (HDI) and gasoline port injection. The results showed that, with the increase of excess air ratio, the brake thermal efficiency increases firstly then decreases and reaches the highest when the excess air ratio is 1.1. In comparison with pure gasoline, hydrogen addition can make the ignition stable and speed up combustion rate to improve the brake thermal efficiency especially under lean burn condition. Furthermore, it can reduce the CO and HC emissions because of more complete combustion, but produce more NO_X emissions due to the higher combustion temperature. Since, in the gasoline plus stratified hydrogen mode, the hydrogen concentration near the sparking plug is denser than that of homogeneous hydrogen, the ignition is more stable and faster, which further speed up the combustion rate and improve the brake thermal efficiency. In the gasoline plus stratified hydrogen mode, the brake thermal efficiency increases by 0.55%, the flame development duration decreases by 1.0°CA, rapid combustion duration decreases by 1.3°CA and the coefficient of variation (COV) decreases by 9.8% on average than that of homogeneous hydrogen. However, in the gasoline plus stratified hydrogen mode, due to the denser hydrogen concentration near the sparking plug and leaner hydrogen concentration near the wall, the combustion temperature and the wall quenching distance increase, which make the NO_X and HC emissions increase by 14.3% and 12.8% on average than that of homogeneous hydrogen.