直喷柴油机喷油速率对燃烧及排放的影响

喷油速率是降低排放的一个重要因素。高压喷射结合小喷孔直径可以减少NO_x与碳烟的排放。本文研究了预喷射及两种较小初始喷油速率的喷油模型对燃烧及排放的影响,发现初始喷油速率比小喷孔油嘴对NO_x排放的影响更大,而后期喷油速率的增加是影响烟度的一个主要原因。     

直喷柴油机喷油速率对燃烧及排放的影响

本文研究了预喷射及两种较小初始喷油速率的喷油模型对燃烧及排放的影响,发现初始油速率比小孔油嘴对ＮＯｘ排放的影响更大,而后期喷油速率的增加是影响烟度的一个主要原因。     

关于高EGR率下的柴油机燃烧及排放的研究

通过试验研究了柴油机在高EGR率下,喷油定时、喷油压力对其燃烧及排放的影响.结果表明:不论是提前还是延迟喷油定时,增加着火延迟,都会减少碳烟排放量,而且喷油定时的提前有保持热效率和防止发动机失火等优点 .在所有的喷油压力下,混合气中氧含量达到9%～10%时,可以实现无烟燃烧.     

喷油定时对柴油机超多喷孔预混合燃烧影响研究

柴油机低温预混合燃烧能够同时大幅度降低NOx和碳烟(soot)排放,本研究采用大量废气再循环(EGR)实现低温燃烧来降低NOx排放,采用超多喷孔喷油嘴并结合高压喷射来缩短喷油持续期,实现预混合燃烧从而降低soot排放,主要对喷油定时如何影响柴油机超多喷孔预混合燃烧性能进行了试验研究,选定4个试验工况,通过改变喷油定时来测试柴油机性能,结果显示随着喷油始点从上止点前向后推迟,各工况的NOx和soot排放都有不同程度的同时下降,有别于传统燃烧方式,但HC,CO,比油耗(BSFC)有所升高。     

喷油系统参数对二甲醚喷雾燃烧过程影响的实验研究

对发动机喷油系统参数对二甲醚(DME)喷雾燃烧过程的影响进行了实验研究，包括喷孔直径和喷油提前角对喷雾燃烧过程的影响。研究结果表明，喷孔直径对DME着火滞燃期和燃烧持续期几乎没有影响，喷孔直径增大，喷雾核心贯穿距增大，燃烧火焰在壁面附近持续时间延长；对于小孔径喷油嘴，燃烧火焰在喷嘴附近持续时间较长，在燃烧中后期可以看到明显的火焰亮光，表明小孔径喷油嘴易产生泄漏，而且随着孔径减小，亮度加强，泄漏越严重；示功图分析结果表明，喷孔直径增大，缸内工质平均温度升高，平均有效压力增大，大孔径喷油嘴有利于提高发动机热效率，但会导致NOx排放升高，在实验条件相当的情况下，喷油提前角对二甲醚着火滞燃期和燃烧持续期几乎没有影响。     

缸内直喷汽油机两阶段喷射喷油规律研究

基于定容积法搭建了均质混合气压燃（HCCI）燃烧模式下的缸内直喷汽油机（GDI）喷油器喷油规律测试台,在保证其测试精度的基础上,研究了GDI喷油器两阶段喷油的喷射压力、喷射背压、两次喷油间隔和体积分数对其喷油规律的影响．结果表明,喷油率随喷射压力增大呈增大趋势;喷射背压只对喷油中期的喷油率有影响且随着喷射背压的增大喷油率有所下降,但喷射背压对喷油总量影响不大．试验测得的喷射间隔小于设定值．另外,两次喷射间隔较小时出现两次喷油过程重叠,使其第2次喷油率高于喷射间隔较大时的第2次喷油率．单次喷油率和喷油持续时间随着喷射体积分数增大而增大．     

喷油定时和燃烧室形状对柴油机燃烧及排放的影响

在保持压缩比不变的条件下,设计了3种不同径深比的燃烧室,并采用CFD数值模拟方法研究了喷油定时和燃烧室形状对柴油机燃烧过程、碳烟和NOx排放的影响.结果表明,随着喷油的推迟,各燃烧室NOx排放均呈下降趋势,碳烟排放则有所增加,尤其是缩口较小的燃烧室,其碳烟生成较多而氧化速率却很低,因此碳烟排放较高.此外,缸内温度为1500～2400K的区域是碳烟生成的主要区域,温度过低不利于碳烟的生成,而较高的温度会促进已生成碳烟的氧化.     

用节流轴针式喷油器的新型直喷柴油机喷油过程研究

对采用节流轴针式喷油器的482Q新型直喷柴油机进行喷油过程测试，并与传统直喷柴油机的喷油系统进行对比。试验表明：482Q新型直喷柴油机喷油系统有较为合适的喷油持续期，最大喷油压力值比传统直喷燃烧用喷油系统低，喷油压力随转速变化小，且低怠速时循环喷油量分散性小，这些特性都有利于柴油机性能的优化。     

喷孔直径对重型柴油机燃烧和排放的影响

为改善重型柴油机大负荷工况下的燃油经济性,通过一台高强化重型柴油单缸机研究了喷油器不同喷孔直径对燃烧和排放的影响,结果表明：随喷孔直径增大(从0.169 mm增大至0.218 mm),最高爆发压力和瞬时放热率峰值均有升高,燃烧持续期缩短,指示热效率提高．喷油器喷孔直径为0.203 mm时的NOx排放最高,而碳烟排放则随着喷孔直径增大而上升．对于大孔径(0.218 mm)喷油器,改善喷雾的雾化性能是提升燃烧速率的关键,通过与高增压和高轨压的协同作用,可进一步提高放热速率和燃烧等容度．模拟结果中,增大喷孔直径会增加单位时间内的气相燃油生成量,且在活塞凹坑底部易产生较大尺度的涡团,利于物质输运,促进混合．     

增压直喷汽油机燃油喷射特性对排放影响的试验研究

基于某1.5L涡轮增压直喷汽油机,搭建试验测试系统,采用试验匹配测试方法研究了喷油模式、喷油时刻、喷油比例、喷油压力等决定燃油喷射特性的关键参数对碳烟排放的影响。试验结果表明:单次喷油模式下在部分负荷时,喷油越提前,碳烟排放越多;在全负荷时,喷油越推迟,碳烟排放越多。在多次喷油模式下,随第一次喷油的推迟碳烟排放降低,随第二、三次喷油的推迟碳烟排放增加。提高喷油压力对部分负荷工况燃烧及排放改善不明显,但外特性工况碳烟排放显著下降,碳氢化合物排放总量也大幅度降低,缸内燃烧速度加快,燃烧稳定性提高,有效燃油消耗率降低约2%。     

在直喷式柴油机上进行HCCI新概念燃烧的探索研究

从形成均匀预混合气及着火后具有良好化学反应动力学效应的角度出发,在单缸135直喷式柴油机上采用双收口型燃烧室、P型喷油泵、预喷射、伞喷油嘴、乳化柴油及乙醇柴油等方法,对实现均质充量压缩着火(homogeneous charge compression ignition,HCCI)燃烧的多种途径进行了对比试验。结果表明:应用伞喷油嘴有效促进了着火前缸内均质预混合气的形成,具有进一步在小排量增压中冷、高压电喷柴油机上推广的潜力;通过燃料设计可控制着火在上止点附近并提高燃烧速率,有利于实现高效、低排放的近似等压预混合燃烧方式。     

Development of variable timing fuel injection cam for effective abatement of diesel engine emissions

Fossil fuel run diesel engines are being favored in light, medium and heavy duty applications as they exhibit higher fuel conversion efficiencies. Direct injection diesels are still facing challenges to obtain trade-off between oxides of nitrogen and particulate emissions. There are sophisticated strategies such as common rail direct injection, particulate filters with associated sensors and actuators but limited to expensive comfort vehicles. In the present experimental study, a mechanically operated simple component, variable timing fuel injection cam, is designed for a 510 cc automotive type naturally aspirated, water-cooled, direct injection diesel engine. Modifications in the fuel injection cam and gear train are carried out to suit the existing engine configuration. Variable speed tests are carried out for testing the efficacy of component on both engine and chassis dynamometers for performance and emissions. It is observed that the engine which is already retarded could further be retarded with variable timing fuel injection cam. Significant reductions in NO_x and smoke emission levels are achieved. Combined effect of VIC with 7% EGR could reduce CO by about 88%, HC + NO_x by 37% and PM emissions by 90%. The Engine incorporated with the designed component and EGR, successfully satisfied the existing emission norms with improved power and specific fuel consumption.     

Effect of pilot fuel injection pressure and injection timing on combustion,performance and emission of hydrogen-biodiesel dual fuel engine

The present study highlights the influence of fuel injection pressure (FIP) and fuel injection timing (FIT) of Jatropha biodiesel as pilot fuel on the performance, combustion and emission of a hydrogen dual fuel engine. The hydrogen flow rates used in this study are 5lit/min, 7lit/min, and 9lit/min. The pilot fuel is injected at three FIPs (500, 1000, and 1500 bar) and at three FITs (5°, 11°, and 17?bTDC). The results showed an increase in brake thermal efficiency (B_th)from 25.02% for base diesel operation to 32.15% for hydrogen-biodiesel dual fuel operation with 9lit/min flow rate at a FIP of 1500 bar and a FITof17?bTDC. The cylinder pressure and heat release rate (HRR) are also found to be higher for higher FIPs. Advancement in FIT is found to promote superior HRR for hydrogen dual fuel operations. The unburned hydrocarbon (UHC) and soot emissions are found to reduce by 59.52% and 46.15%, respectively, for hydrogen dual fuel operation with 9lit/min flow rate at a FIP of 1500 bar and a FIT of 11?bTDC. However, it is also observed that the oxides of nitrogen (NO_X) emissions are increased by 20.61% with 9lit/min hydrogen flow rate at a FIP of 1500 bar and a FIT of 17?bTDC. Thus, this study has shown the potential of higher FIP and FIT in improving the performance, combustion and emission of a hydrogen dual fuel engine with Jatropha biodiesel as pilot fuel.     

预喷正时对柴油机燃烧与排放影响的试验研究

通过台架试验,分析对比柴油机各参数随预喷正时的变化,研究多次喷射预喷正时对柴油机燃烧和排放性能的影响。试验表明,预喷正时决定缸内燃烧的放热始点和放热率,影响缸内的燃烧温度、爆发压力、NOx排放和碳烟的生成,预喷正时为20°时,爆发压力最大;预喷正时为35°时,热效率最高,油耗率和烟度最低;预喷正时为45°时,NOx排放最小。综合分析选择预喷正时40°作为折中优化方案,降低发动机油耗和NOx、碳烟排放,同时提高发动机的热效率。     

Influence of injection timing on performance, emission and combustion characteristics of a DI diesel engine running on waste plastic oil

Environmental concern and availability of petroleum fuels have caused interests in the search for alternate fuels for internal combustion engines. Waste plastics are indispensable materials in the modern world and application in the industrial field is continually increasing. In this context, waste plastics are currently receiving renewed interest. As an alternative, non-biodegradable, and renewable fuel, waste plastic oil is receiving increasing attention. The waste plastic oil was compared with the petroleum products and found that it can also be used as fuel in compression ignition engines. In the present work, the influence of injection timing on the performance, emission and combustion characteristics of a single cylinder, four stroke, direct injection diesel engine has been experimentally investigated using waste plastic oil as a fuel. Tests were performed at four injection timings (23°,20°,17° and 14° bTDC). When compared to the standard injection timing of 23° BTDC the retarded injection timing of 14° bTDC resulted in decreased oxides of nitrogen, carbon monoxide and unburned hydrocarbon while the brake thermal efficiency, carbon dioxide and smoke increased under all the test conditions.     

柴油机高压共轨喷射系统参数对燃烧和排放性能影响的研究

利用AVL-FIRE软件建立TBD234柴油机高压共轨燃烧过程仿真计算模型,通过仿真计算,系统分析了喷射系统主要参数对柴油机高压共轨燃烧和排放性能的影响。最后进行了试验验证,结果表明,仿真值与试验值基本吻合。研究结果为柴油机高压共轨喷射系统参数的优化设计提供了可靠依据。     

Effects of Fischer-Tropsch diesel fuel on combustion and emissions of direct injection diesel engine

Effects of Fischer-Tropsch (F-T) diesel fuel on the combustion and emission characteristics of a single-cylinder direct injection diesel engine under different fuel delivery advance angles were investigated. The experimental results show that F-T diesel fuel exhibits shorter ignition delay, lower peak values of premixed burning rate, lower combustion pressure and pressure rise rate, and higher peak value of diffusion burning rate than conventional diesel fuel when the engine remains unmodified. In addition, the unmodified engine with F-T diesel fuel has lower brake specific fuel consumption and higher effective thermal efficiency, and presents lower HC, CO, NO _x and smoke emissions than conventional diesel fuel. When fuel delivery advance angle is retarded by 3 crank angle degrees, the combustion duration is obviously shortened; the peak values of premixed burning rate, the combustion pressure and pressure rise rate are further reduced; and the peak value of diffusion burning rate is further increased for F-T diesel fuel operation. Moreover, the retardation of fuel delivery advance angle results in a further significant reduction in NO _x emissions with no penalty on specific fuel consumption and with much less penalty on HC, CO and smoke emissions. __________ Translated from Chinese Internal Combustion Engine Engineering, 2007, 28(2): 19–23 [译自: 内燃机工程]     

柴油机二次喷射燃烧系统流场分析

以KIVA3为计算平台，对4气门直喷式非增压柴油机在油注喷向燃烧室侧壁后飞溅形成二次喷射燃烧的整个工作过程进行了模拟计算，着重分析了压缩和膨胀做功冲程缸内流场。得出以下结论：在进气涡流作用下，活塞压缩后期产生的挤流以螺旋线路进入燃烧室，因此对若干几何参数一样的喷孔喷出的油注产生的柴油气的作用不同，进而各油注的燃烧历程也不同。对带有二次喷射导向壁面的小口径比和小径深比的ω型燃烧室，充分利用活塞顶面以上氧气的问题仍有待解决。     

改进燃油喷射系统,降低柴油机有害排放

燃油喷射系统的各结构参数对柴油机的排放有重要的影响。通过对喷射系统的几个主要参数如喷油规律、喷孔直径、喷油压力等的分析来阐明其对排放的影响。     

Effects of injection timing and rail pressure on combustion characteristics and cyclic variations of a common rail DI engine fuelled with F-T diesel synthesized from coal

The use of Fischer-Tropsch (F-T) diesel synthesized from coal in automobiles can alleviate the shortage of petroleum and promote clean utilization of coal. In this study, the effects of injection timing (IT) and rail pressure (RP) on the brake thermal efficiency (BTE), combustion characteristics, and cyclic variations of F-T diesel were investigated on a turbocharged, 6-cylinder, common rail direct injection (CRDI) diesel engine. The results indicate that increasing RP results in higher BTE, whereas advancing IT results in an initial BTE increase and a subsequent BTE decrease. In comparison with petroleum diesel, the BTE of F-T diesel increased by 0.54% on average and by a maximum of 1% under different conditions. When the IT was advanced from 2 °CA to 18 °CA BTDC, the ignition delay periods (IDP) first decreased and then increased, whereas the combustion durations (CD) first lengthened and then shortened; peak cylinder pressure (PCP), peak pressure rise rate (PPRR), and peak combustion temperature (PCT) gradually increased; peak heat release rate (PHRR) first decreased and then increased at the low loads, whereas it always increased at medium and high loads. In comparison with petroleum diesel, the IDP of F-T diesel decreased by 22–31% at various conditions, and the CD was slightly longer than that of petroleum diesel at most conditions. Additionally, increasing RP resulted in a decrease in the IDP and CD, and a significant increase in PCP, PPRR, PHRR, and PCT. At low loads, the PPRR and PHRR of F-T diesel were 32.72% and 32.13% lower than that of diesel owing to the shorter ignition delay. This implies that using F-T diesel can help in attaining smoother engine running and has lower combustion noise. Advancing the injection timing or increasing the engine loads can decrease the cyclic variations, whereas increasing rail pressure results in the increment of COVp_max at low loads and the significant decrement of COVp_max at medium and high loads. In comparison with petroleum diesel, F-T diesel exhibits higher combustion stability owing to the better volatility and higher fuel reactivity.