An experimental investigation is conducted to evaluate the performance, combustion, and emission characteristics of a diesel engine using cerium oxide (CeO2) nanoparticles as diesel fuel additives. Using cetyl trimethyl ammonium bromide (CTAB) as the cationic surfactant and with ultrasonic vibration, CeO2 nanoparticles at dosing levels of 50 and 100mg/L can be stably and uniformly dispersed in diesel. Physically, the mixing of fuel blends with air is enhanced by microexplosion events because of the large surface-volume ratio and intensified thermal transmissibility of nanoparticles. Moreover, chemically, CeO2 in diesel fuel plays a positive role in the dehydrogenation reaction at a high temperature because of its excellent redox ability. As a result, the addition of nano-CeO2 to neat diesel (50 and 100mg/L) leads to a gradual increase in the cylinder pressure compared with the reference neat diesel. Meanwhile, the ignition of fuel blends with a high dosing level of nano-CeO2 occurs earlier by approximately 1.2 degrees crank angle (CA) and 1.8 degrees CA, respectively. At full load, the effective thermal efficiencies for nano-CeO2 fuels are augmented by approximately 1.7 and 2.3%. Because of the distinctive merits of nano-CeO2 in promoting fuel atomization and its favorable intrinsic catalytic effect, the level of harmful pollutants (such as HC, CO, NOx, and soot) in exhaust gases is appreciably reduced to varying degrees.

研究了乙醇柴油及燃油添加剂对柴油机颗粒排放及其挥发氧化特性的影响.采用热重分析法分析柴油机燃用不同燃料时排气颗粒物的可溶性有机物挥发性、碳烟样品和颗粒物氧化特性.研究结果表明:含添加剂的乙醇柴油颗粒物排放远低于0 #柴油的颗粒物排放,降幅在50％以上.颗粒在热失重过程中经历颗粒失水干燥、可溶性物质氧化和烟煤基元发生氧化反应三个阶段.与0 #柴油相比,乙醇柴油及柴油添加剂能降低颗粒物中的可挥发部分质量份额,且乙醇柴油的效果最佳.乙醇及柴油添加剂有助于降低碳烟起燃温度和最大氧化速率对应的温度;与0 #柴油相比、N5E10、N5E10XY0.1％和N5E10CN0.3％的碳烟最大氧化速率对应的温度依次降低了39、92、146℃.

The PM emission of diesel mixed with 50 mg/kg and 100 mg/kg CeO2 or Co3 O4 nano‐particle was measured on 186FA diesel engine and the microstructure and thermo gravimetric characteristics of collected particulate samples were analyzed with the scanning electron microscope and thermo gravimetric analyzer .The results show that both CeO2 and Co3 O4 nano‐parti‐cles can improve the PM emission of diesel engine .Compared with 0# diesel fuel ,the specific PM emission of blended fuel re‐duces by 16 .4%‐35 .9% .The particle size of blended fuel shows the single peak distribution of 0 .56‐1 .0 μm ,the microscopic particle size and porosity decrease obviously and the accumulation strengthens .The ignition temperature ,weight loss peak tem‐perature and burnout temperature of particle oxidation reaction during the combustion of blended fuel decrease and the maxi‐mum weight loss rate increases obviously .

In this paper,effects of diesel /DMC blends on engine's performance and emissions were investigated in a single-cylinder diesel engine. The results showed that when the engine was fueled with diesel /DMC blends,the effective thermal efficiency decreased significantly,and the HC and CO emissions increased rapidly under low and moderate loads,however,the NO x emissions reduced by 20% ~ 46%. The PM emissions were improved with lower mixing proportion of DMC,but increased rapidly when the mixing proportion of DMC in diesel was over 5%. Because high latent heat of vaporization and low cetane number of DMC have an important impact on combustion process,it is necessary to optimize the combustion system when the engine is fuelled with such fuel.

In this paper, two kinds of micro-emulsified biodiesel containing 5.6% and10% water are prepared. The effects of micro-emulsified biodiesel on engine's power, combustion and emission characteristics are investigated in a DI diesel engine The results show that under the rated speed and full load operating conditions, the maximum pressure rise rate and peak heat release rate for micro-emulsified biodiesel increase dramatically, while the ignition delay is prolonged and the combustion duration becomes shorter. Compared to base diesel, the HC, CO and smoke emissions from the engine fueled with biodiesel decrease sharply, except for a 9% increased NOx at large loads. However, micro-biodiesel could significantly reduce the NOx and smoke emissions, except for the higher HC and CO emissions at low and medium loads. When fuelled with 10%MB, the NOx and smoke emissions are 9% and 90% lower than that of diesel, respectively. Results reported here suggest that the application of micro-emulsified biodiesel in diesel engines has a potential to improve combustion process and reduce NOx, PM emissions simultaneously.

10%rapeseed oil(RO),10%dimethyl carbonate(DMC),and 5%RO plus 5%DMC were separately mixed in pure diesel,forming three kinds of oxygenated fuels.Comparing with the pure diesel,some experiments on their combustion characteristics and emissions were carried out in a single cylinder diesel engine with these mixtures.Results showed that the properties of the oxygenated fuels had a little effect on fuel consumption and thermal efficiency,but greater influence on combustion and emission.These three oxygenated fuels have a little influence on maximum explosion pressure of the cylinder.Comparing with fueling the pure diesel,the ignition delay period was shorter with fueling two mixtures,10%RO and 5%RO plus 5%DMC,but longer with 10%DMC.Comparing with the pure diesel,5%RO plus 5%DMC and 10%DMC slighdy made the CO,HC and NOx emission increase on full load condition of the engine,10%RO has a lower emission on smoke and HC,and a higher emission on CO and NOx.

Being a multi-component fuel,the micro-emulsified ethanol-diesel differs from pure diesel oil in evaporation characteristics.For droplet of 20~30μm and under conditions of relatively intensive convective flow,the Distillation Curve Model for multi-component droplets may be acceptable for establishing their single droplet evaporation model.The model was employed to investigate the evaporation process to obtain effects of ambient temperature,pressure and ethanol content on the single droplet evaporation and rules.Results indicate that with ambient temperature rising droplet evaporation accelerates,equilibrium temperature increases and droplet lifetime shortens,and under a relatively low temperature environment,the droplet lifetime increases with ambient pressure rising.In condition of environment temperature 500K and ambient pressure 1.0MPa,the droplet lifetime decreases,and the droplet transient heating time and equilibrium temperature variate little with ethanol content increasing.

Developing new and highly efficient fuel additives have become an important topic of controlling engine combustion and emissions. For its unique physiochemical properties, nano-particles CeO2 makes it own a unique role in the field of catalytic combustion and exhaust gas purification. Through adding a trace amount of nano-particles CeO2 to diesel oil, two CeO2-diesel blends with the masse fraction of 50 and 100 mg/L of nano-particles CeO2 have been prepared, which makes D50C, D100C and Diesel these three test fuels, together with pure diesel as a reference. And the influences of these three test fuels on 186FA diesel engine combustion and emission have been investigated. The results show that: By using physical and chemical methods such as adding surfactant and ultrasonic processing, nano-particles CeO2 can be suspended stably in diesel. At full load at rated speed , the in-cylinder pressure peak, pressure rise rate peak and heat release rate peak have increased slightly when engine fuelled with D50C and D100C, while the corresponding crank angles are in advance accordingly, their ignition delay periods are also shorten by 1° or 2° crank angle accordingly. The engine’s brake specific fuel consumption has reduced slightly with the effective thermal efficiency slightly increased when fuelled with D50C and D100C. Four conventional pollutants have reduced with different degrees with the addition of nano-particles CeO2 into diesel, and their reduction margins are more evident with the increase of the amount of nano-particles CeO2 in diesel. As compared to diesel, at full load at rated speed, the brake specific fuel consumption of D50C and D100C have droped 1.6%and 2.3%with a increase of 1.7%and 2.3%in corresponding effective thermal efficiency. The CO、HC、NOx and smoke emissions of D50C and D100C have decreased in average by 3.4%and 6.5%、15.1%and 18.4%、2.4%and 5.4%、4.0%and 7.8%, respectively. The costs of D50C and D100C blends are 0.8%and 1.6%higher than that of diesel. On the whole, with a slight increase in fuel price through the trace addition, nano-particles CeO2 is a kind of fuel additives with excellent performance, which can achieve highly combustion、energy conservation and emission reduction of engine.

To further research the influence of biodiesel and DMC mixing ratio on diesel engine performance,90%diesel blended fuels mixed with 10% biodiesel,10% DMC,5% biodiesel and 5%DMC were prepared respectively and formed B10,D10,B5D5and diesel four test fuels together with pure diesel.The effects of different oxygenated fuels on combustion process,economy and emission were investigated.The results show that the three oxygenated fuels have little influnce on maximum incylinder pressure and pressure rise rate.The maximum heat release rate of B10slightly decreases,while that of B5D5and D10 increase significantly due to the addition of DMC.The ignition delay caused by DMC is more obvious than the ignition advance caused by the same amount of biodiesel.B10and D10have the same equivalent brake specific fuel consumption as diesel,but that of B5D5slightly decreases.When fueled with B10,CO,HC and soot emssion all decrease except 7.9%increase of NOx at full load.Though the introduction of DMC to mixed fuels is bad for the oxidation of HC and CO,it can reduce the smoke and NOx emissions simultaneously.

According to the ESC 13-mode test cycle,an experimental study was conducted to investigate the purification effect of integrated purifier DOC/POC on the pollutant emissions of a 4-cylinder diesel engine fueled with Euro-Ⅲ/Ⅳ fuels.The results show that the difference in test fuels has little effcet on HC,CO and NOx emissions of the engine without DOC/POC.The purification effects of integrated purifier on HC and CO emissions can reach up to 85% and 90%,respectively,but with little effect on NOx.Influenced by the sulfur content in test fuels,when equiped the integrated purifier,the engine with Euro-Ⅲ fuel shows a 22.3% increase in its PM emissions however,45% decrease of PM emissions with Euro-Ⅳ fuel.On the whole,in order to ensure this engine meets China IV-stage emission standard,it is necessary to redesign such integrated purifier and optimize the matching parameters of it and the engine.

The addition of 10% biodiesel and 10%DMC,together with pure diesel form three test fuels which were called B10,D10 and diesel respectively,then effects of different oxygenated fuels with low proportional addition on combustion process,economic and emission characteristics were investigated in a single-cylinder engine.Results showed that under the rated operating condition,these two oxygenated fuels had little influnce on engine's maximum cylinder pressure and pressure rise rate peak,the maximum heat release rate of B10 was slightly decreased,while the addition of DMC,that of D10 was increased significantly.As compared to diesel,the ignition delay of B10 has shortened by about 1 ℃A which the ignition delay of D10 has extended by 2 ℃A;the effect of DMC on prolonging ignition delay was more obvious than the impact of biodiesel with same proportion on shortening ignition delay.The fuel comsupation of B10 was almost the same as that of diesel,while that of D10 was higher.The B10 could slightly reduce HC、CO and smoke emissions,except for a 7.9% higher NOx emissions at full load.Though the introduction of DMC in mixed fuels didn't promote the oxidation of HC and CO,it could simultaneously reduce NOx and smoke emissions.The NOx and smoke emissions of D10 have decrased by 13.1% and 17.7%.On the whole,the low proportional addition of biodiesel and DMC in diesel could partly achieve excellent subtitute of diesel without influencing the engine's performance.

Emulsifier mixture OP4/Span80, n-butanol and biodiesel were utilized as co-solvent to prepare three kinds of ethanol-diesel with the same mixing proportion of ethanol (R5E10, N5E10 and B10E10). The experiments were conducted to comparatively analyze the performance, combustion and emission characteristics of a diesel engine fuelled with diesel and ethanol-diesel. The results showed that the brake specific fuel consumption of diesel engine fuelled with ethanol-diesel was lower than that with diesel, and B10E10 and N5E10 had the lowest brake specific fuel consumption. The combustion timing was postponed, and the maximum cylinder pressure, the maximum pressure rise rate and peak heat release rate increased when fuelled with ethanol-diesel, while the corresponding crank angle delayed. The maximum pressure rise rate and peak heat release rate were highest when fuelled with N5E10, the second highest was with B10E10, while the maximum cylinder pressure had the highest value at full load when fuelled with R5E10. As compared to diesel, ethanol-biodiesel could significantly improve NOx and smoke emissions, except for the higher HC and CO emissions under low and moderate loads. On the whole, biodiesel is an optimum co-solvent for preparation of ethanol-diesel, which has important impact on improving combustion and optimizing pollutant emissions.