柴油/乙醇混合燃料的性质及对发动机性能的影响

研究了不同掺混比例的柴油/乙醇(C2H5OH)混合燃料的相溶问题,分析了柴油/C2H5OH混合燃料对发动机动力性和经济性的影响,并结合13工况下试验结果分析了混合燃料对发动机HC和微粒(PM)排放的影响。实验结果表明,助溶剂可有效解决柴油的相溶问题,燃料较低的十六烷值是造成小负荷下HC和PM中可溶性有机物(SOF)排放恶化的主要因素。     

乙醇柴油着火促进剂对发动机排放的影响

在一台增压中冷柴油机结构不作任何变动的条件下,按13工况排放试验循环进行了不同乙醇柴油的试验研究。结果表明,燃用乙醇柴油与柴油相比,发动机的CO和HC排放率增加,尤其是低转速小负荷工况的分担率增加较大,NOx排放率基本未变。着火促进剂的加入提高了乙醇柴油的着火性,使CO和HC排放率减少,特别在低速小负荷工况减少的幅度更大,但NOx排放率增加。     

不同喷射策略下CRDI柴油机燃用柴油-桐油-乙醇混合燃料的燃烧与排放特性

在1台共轨直喷(CRDI)柴油机上开展了不同喷射策略下桐油、乙醇与柴油混合燃料的燃烧和排放特性研究。试验结果表明:与0号柴油相比,混合燃料的着火延迟期稍长,缸内压力峰值和放热率较高,但燃烧持续期稍短;随着桐油和乙醇体积分数的增加,有效热效率(BTE)也随之增大。在低负荷时,混合燃料的CO和HC排放较高,且随着桐油和乙醇所占体积分数的增大而增加;混合燃料的NO_x排放在低负荷时较低,在高负荷时略高;在高负荷时,混合燃料的炭烟排放大大减少。总体而言,混合燃料中乙醇对发动机性能的影响比桐油大。     

生物柴油-柴油-乙醇混合燃料的燃烧与排放特性

为了改善发动机燃用高比例生物质混合燃料的性能,在中等比例的生物柴油-柴油混合燃料中分别添加5%、10%和20%体积比的乙醇（分别用BD50E5,BD50E10和BD50E20表示）,在一台6缸增压共轨柴油机上,将发动机的转速稳定在1 600 r·min^-1,选择7个不同的负荷点测定不同掺混比生物柴油-柴油-乙醇混合燃料的燃烧与排放性能,并将其与柴油进行对比。结果表明：在平均有效压力为0.322 MPa的低负荷条件下,发动机为预喷加主喷喷油策略,在预喷的低温反应阶段生物柴油-柴油-乙醇混合燃料产生了大量羟基自由基,因此混合燃料的缸内最大压力和最大瞬时放热率均高于柴油;随着负荷的增大,当平均有效压力为0.805 MPa时,发动机的喷油策略转变为单段喷射,乙醇的热值较低导致生物柴油-柴油-乙醇混合燃料的缸内最大压力和最大瞬时放热率低于柴油;随着乙醇掺混比的增大,受乙醇低十六烷值和高汽化潜热的影响,生物柴油-柴油-乙醇混合燃料的滞燃期明显延长;强烈的预混燃烧和乙醇的高含氧量使混合燃料的燃烧速度明显加快,乙醇的添加有利于燃料集中放热从而缩短燃烧持续期;与纯柴油相比,BD50E5,BD50E10和BD50E20的NO_x排放量分别升高了10.46%、12.59%和17.52%,碳烟排放量分别降低了37.91%、45.85%和49.25%,CO排放量分别降低了20.24%、36.43%和46.43%,HC排放量分别降低了12.53%、4.40%和0.76%。     

Influence of turpentine addition in Jatropha biodiesel on CI engine performance,combustion and exhaust emissions

The prospect of using turpentine oil as an additive for Jatropha biodiesel and using it as an alternative fuel for diesel in CI engines has been experimented in this work. Tests were carried out in a single cylinder, air cooled, constant speed, direct injection diesel engine. The results display that the performance of Jatropha-Mineral Turpentine (JMT) and Jatropha- Wood Turpentine (JWT) blends were found close to diesel, emission features were enhanced and combustion parameters were noticed to be comparable with diesel. Brake thermal efficiency of JMT20 blend found closer to diesel at 75 % load. BSFC increases for JMT and JWT blends at part load and maintains at full load. CO, HC and Smoke emissions were reduced with JMT and JWT blends at 75 % load. NOx emissions were on the raise. Furthermore, JMT and JWT blends offered comparable performance and combustion parameters, reduced emissions and both can substitute standard diesel in CI engines.     

EGR回路喷甲醇在柴油机上的应用研究

在YC6A220C柴油机上进行了进气道喷甲醇结合EGR的试验研究,在保持原柴油机动力性基本不变的基础上,研究了在不同负荷下,选用不同的EGR率和不同甲醇消耗率对原机的动力性、经济性、NOx和炭烟排放的影响。研究结果表明:单纯地使用EGR对于降低NOx效果比较明显,但是难以同时降低炭烟的排放,尤其当EGR率超过30%时,随着EGR率或者负荷的增加炭烟也急剧增加。向回路喷入适量甲醇后,不但可以保证NOx排放减少,而且炭烟排放也可以大幅度降低。在1 500r/min(最大扭矩转速)下,在EGR率为20%~35%,甲醇消耗率为50~70g/(kW·h)范围内,可以同时降低NOx和炭烟排放。发动机的动力性和燃油消耗略有降低,排放水平均低于燃用0号柴油。     

Enhancement of NOx-PM trade-off in a diesel engine adopting bio-ethanol and EGR

For realizing a premixed charge compression ignition (PCCI) engine, the effects of bio-ethanol blend oil and exhaust gas recirculation (EGR) on PM-NOx trade-off have been investigated in a single cylinder direct injection diesel engine with the compression ratio of 17.8. In the present experiment, the ethanol blend ratio and the EGR ratio were varied focusing on ignition delay, premixed combustion, diffusive combustion, smoke, NOx and the thermal efficiency. Very low levels of 1.5 [g/kWh] NOx and 0.02 [g/kWh] PM, which is close to the 2009 emission standards imposed on heavy duty diesel engines in Japan, were achieved without deterioration of the thermal efficiency in the PCCI engine operated with the 50% ethanol blend fuel and the EGR ratio of 0.2. It is found that this improvement can be achieved by formation of the premixed charge condition resulting from a longer ignition delay. A marked increase in ignition delay is due to blending ethanol with low cetane number and large latent heat, and due to lowering in-cylinder gas temperature on compression stroke based on the EGR. It is noticed that smoke can be reduced even by increasing the EGR ratio under a highly premixed condition.     

二甲醚／柴油混合燃料在压燃式发动机上的应用

为探索二甲醚/柴油混合燃料作为柴油机替代燃料的应用性能,对D20二甲醚/柴油混合燃料的喷雾特性进行了试验研究;同时,开展了直喷式柴油机燃用二甲醚/柴油混合燃料动力性能、经济性能及排放性能研究。结果表明:在同样的环境背压下,D20混合燃料的油束与柴油相比较,贯穿度有所缩短,喷雾锥角有所增大;柴油机燃用二甲醚/柴油混合燃料时,通过适当调整循环油量,发动机的动力性可以超过原柴油机,最低当量比油耗下降4.5%,烟度指标下降70%以上,NOx排放降低30%~50%;二甲醚/柴油混合燃料是一种能实现高比功率、低排放的石油替代燃料。     

柴油/GTL混合燃料特性及对柴油机排放的影响

研究了不同比例的柴油与天然气合成油(GTL)混合燃料的主要理化特性,采用ECER49十三工况法测试了一台增压柴油机燃用各种混合燃料的有害排放。结果显示:随GTL比例的增加,混合燃料的密度、硫和芳烃含量逐渐减小,黏度、十六烷值和低热值逐步增大,以70%馏出率为界,GTL馏程从大于变为小于柴油的馏程;与柴油相比,GTL能降低所有常规排放,且随GTL比例增加,降低趋势愈明显。     

采用双段喷射改善二冲程柴油机的排放性能

在配有电控共轨系统和扫气系统的二冲程柴油机试验台上进行了3种不同喷油模式对柴油机燃烧及排放性能影响的试验研究。试验结果表明,单段早喷有助于实现低NOx和碳烟排放,但柴油机无法在高负荷下运行;标准喷射的排放很高;双段喷射表现出良好的性能,它实现了柴油机的柔和运行,并且在全负荷范围内使NOx和碳烟排放降低40%以上。在双段喷射基础上,利用高压喷射及内部EGR进一步改善了柴油机的排放。     

Influence of pilot injection on combustion characteristics and emissions in a DI diesel engine fueled with diesel and DME

This work experimentally investigates how the dwell time between pilot injection and main injection influences combustion and emissions characteristics (NOx, CO, THC and smoke) in a single-cylinder DI diesel engine. The experiments were conducted using two fuel injection systems according to the fuel type, diesel or dimethyl ether (DME), due to the different fuel characteristics. The injection strategy is accomplished by varying the dwell time (10°CA, 16°CA and 22°CA) between injections at five main injection timings (?4°CA aTDC, ?2°CA aTDC, 0°CA aTDC, 2°CA aTDC and 4°CA aTDC). Results from pilot-main injection conditions are compared with those shown in single injection conditions to better demonstrate the potential of pilot injection. It was found that pilot injection is highly effective for lowering heat-release rates with smooth pressure traces regardless of the fuel type. Pilot injection also offers high potential to maintain or increase the BMEP; even the combustion-timing is retarded to suppress the NOx emission formation. Overall, NOx emission formation was suppressed more by the combustion phasing retard effect, and not the pilot injection effect considered in this study. Comparison of the emissions for different fuel types shows that CO and HC emissions have low values below 100 ppm for DME operation in both single injection and pilot-main injection. However, NOx emission is slightly higher in the earlier main injection timings (?4°CA aTDC, ?2°CA aTDC) than diesel injections. Pilot injection was found to be more effective with DME for reducing the amount of NOx emission with combustion retardation, which indicates a level of NOx emission similar to that of diesel. Although the diesel pilot-main injection conditions show higher smoke emission than single-injection condition, DME has little smoke emission regardless of injection strategy.     

正丁醇-柴油对柴油机燃烧及排放影响的试验研究

通过配制不同正丁醇掺混比例的正丁醇-柴油混合油,在不改变供油提前角和燃油系统的条件下,测量了柴油机燃用正丁醇-柴油混合油的气缸压力、放热率以及NOx、炭烟等排放污染物,探讨了正丁醇掺混比例对柴油机燃烧过程的影响规律,分析了正丁醇对排放污染物的作用过程。结果表明:正丁醇掺混比例为0%,5%,10%时,低转速、低负荷工况下,缸内最大燃烧压力分别为6.2MPa,5.9MPa和5.8MPa,与燃烧柴油相比略有降低;高转速、高负荷工况时,缸内最大燃烧压力分别为7.5 MPa,7.6 MPa,7.7 MPa,与燃烧柴油相比稍有增加;随着正丁醇掺混比例增加,柴油机的CO和HC排放升高,在中低负荷下NOx排放有所降低,高负荷时升高明显,平均增加了6.4%,炭烟排放降低明显,燃用正丁醇添加比例为5%和10%时,在高负荷下炭烟分别下降了25%和36%。     

掺烧LPG对直喷式柴油机性能的影响

提出一种柴油机混合燃用LPG的新方式,即LPG/柴油混合喷射方式。分析了不同LPG质量掺混比对发动机热效率、排放特性和燃烧特性的影响。试验结果表明,LPG掺混比较小时,可以改善发动机的热效率;掺混比较大时,烟度和NO_x排放大幅降低,平均有效压力较高时CO排放也有所降低,HC略有升高;LPG混入柴油中对发动机燃烧特性也有显著影响。     

Analysis of the capabilities of a two-stage turbocharging system to fulfil the US2007 anti-pollution directive for heavy duty diesel engines

This article presents a two-stage turbocharged heavy-duty diesel (HDD) engine designed to fulfil the US2007 anti-pollution directive. This directive imposes very restrictive limits on the NOx and particle emissions of HDD engines. In this work, the possibility of combining particle traps in the exhaust line to reduce soot emissions with very high EGR rates to reduce NOx emissions is considered. This new generation engine implements two-stage turbocharging in order to improve the bsfc when the engine is working on steady conditions as well as to optimize the engine transient response. After carrying out the tests, the results were analyzed and the engine settings were adjusted to maximise its behaviour and minimise pollutant emissions. NOx and soot emission peaks were also analyzed at engine transient conditions in order to keep them under certain levels, and thus maintain the overall pollutant emissions to a level that is as low as possible. In summary, a double-stage turbocharging configuration can greatly improve engine driveability (between 23% and 36% depending on engine speed), while reducing NOx emissions during transient evolution without increasing opacity peaks beyond the stated limits.     

Multi-response optimization of diesel engine performance parameters using thumba biodiesel-diesel blends by applying the Taguchi method and grey relational analysis

This paper presents an experimental study that involves an application of the Taguchi method and grey relational analysis to determine the optimum factor level to obtain optimum multiple-performance characteristics of a diesel engine run with different low-percentage thumba biodiesel-diesel blends. Four factors, namely, low-percentage thumba biodiesel-diesel blend, compression ratio, nozzle opening pressure and injection timing were each considered at three levels. An L₉ orthogonal array was used to collect data for various engine performance- and emission-related responses under different engine loads. The signal-to-noise (S/N) ratio and grey relational analysis were used for data analysis. The results of the study revealed that the combination of a blend consisting of 30% thumba biodiesel (B30), a compression ratio of 14, a nozzle opening pressure of 250 bar and an injection timing of 20° produces maximum multiple performance of a diesel engine with minimum multiple emissions from the engine.     

柴油机燃用生物柴油的排放特性试验研究

在一台四冲程直喷式柴油机上进行了燃用生物柴油混合燃料的试验研究,分析了掺混不同比例生物柴油时柴油机的燃烧与排放性能.结果表明,与燃用纯柴油相比,燃用生物柴油混合燃料可改善燃烧过程,大幅降低HC、CO的排放,但同时会引起NOx排放量的增大;燃用生物柴油可大幅降低微粒排放,且随柴油中掺混生物柴油比例的增大,降低程度也逐渐增大.     

混合燃料的含氧量对改善柴油机排放的试验研究

在一台S1100A2型单缸柴油机上,通过在柴油中添加乙醇、甲缩醛(DMM)、碳酸二甲脂(DMC)等3种含氧添加剂,研究了在常用工况下混合燃料的含氧量对柴油机排放特性的影响。试验结果表明,含氧混合燃料可以有效改善柴油机的烟度和CO排放,在大负荷下尤为明显,而对NOx和HC的排放影响较小。     

GTL燃料发动机的性能及排放特性

进行了柴油机燃用柴油、天然气制油GTL燃料及GTL-柴油混合燃料(GTL燃料体积分数分别为10％和20％)的外特性、负荷特性和ESC十三工况试验,研究了柴油机燃用GTL燃料的动力性、经济性和排放特性.试验结果表明:与燃用柴油相比,随着GTL燃料比例的增大,柴油机排放逐渐降低.燃用GTL燃料时的外特性功率和扭矩与柴油相当...     

Investigation of soot formation in Diesel-GTL fuel blends under quiescent conditions

In this study, a visual investigation of sprays and flames is performed, and soot formation in Diesel-GTL fuel blends is studied in a specially designed quiescent constant-volume chamber under various ambient gas temperatures and O₂ concentrations. Similar to the case of soot formation during diesel fuel combustion, the sooting zone during the mixing-controlled combustion of Diesel-GTL blends is located in the leading portion of the jet boundaries. Auto-ignition delay and soot concentration decrease with an increase of GTL content in the fuel blend. Soot also decreases with lower O₂ concentration, higher injection pressure, and lower ambient gas temperature. The lack of soot formation at lower O₂ concentrations and lower temperatures suggests that Diesel-GTL fuel blends can be successfully utilized in low-temperature diesel combustion technologies that are currently being developed. Furthermore, this mixing controlled combustion method with Diesel-GTL blends can be used to modulate various engine operation parameters, and therefore to simultaneously reduce the formation of soot and NOx within a wide range of diesel engine loads.     

电控高压共轨柴油机燃用生物柴油的试验研究

在1台电控高压共轨柴油机和装有该型号发动机的轿车上,进行不同掺混比生物柴油—柴油混合燃料的性能对比试验,分析了在不同转速和负荷下柴油机燃用不同掺混比混合燃料的动力性、经济性和排放性。研究结果表明:生物柴油与柴油相比,在2 200 r/min负荷特性下,有效能耗率减少,NOx排放增加较多,中小负荷炭烟排放基本相同,大负荷炭烟排放明显降低,中小负荷HC排放明显降低,大负荷HC排放基本一致,CO排放基本不变;在外特性下,功率略有增加,HC排放和炭烟排放均有所降低,CO排放和NOx排放增加。