适宜溶气量改善生物柴油/柴油混合燃油雾化质量

Suitable dissolved gas improving atomization quality of biodiesel/diesel mixed fuel

为探究溶气对燃油雾化性能的影响,该文对生物柴油、0号柴油、混合燃油及经溶气处理的混合燃油的雾化特性进行了试验研究,采用多普勒粒子分析仪(phase doppler particle analyzer,PDPA)测量系统对不同比例的混合燃油在喷孔直径为0.26和0.30 mm下进行喷雾试验。对喷雾中心轴的轴向速度与粒径分布进行测量和分析,并进一步以混合燃油为基础,在其中分别溶入不同体积的CO_2,溶气所占体积比分别为5.74%、12.73%和26.42%,分别使用2种孔径的喷嘴对溶气燃油进行雾化性能的测量。结果表明,混合燃油的雾化效果与生物柴油相比得到明显改善,与生物柴油相比柴油的索特平均直径(sauter mean diameter,SMD)在轴向长度70 mm处下降了25μm,且喷孔直径越小雾化效果越好,当喷孔直径由0.30 mm降低到0.26 mm时,B0与B100的SMD分别降低了12.94%,19.57%。低溶气量的燃油其索特平均直径大于未溶气燃油,且随着喷孔直径的减小对雾化的抑制作用更加明显,当溶气所占体积比为5.74%和12.73%时随着喷孔直径从0.30 mm降低到0.26 mm其SMD分别增加了8.43%和6.82%。溶气量较高时其雾化效果得到改善,且随着喷孔直径的减小,改善效果得到增强,溶气所占体积比为26.42%时随孔径的减小其SMD降低了26.5%。本研究表明适当在生物柴油中溶气可以改善其雾化质量,研究结果可为生物柴油更好地应用于车辆内燃机领域提供参考。

In order to improve the atomization quality of biodiesel and diesel-biodiesel blends containing dissolved gas,the Phase doppler particle analyzer(PDPA,a device that can accurately measures the diameter and velocity of droplets in a spray field)was used to analyse the atomization quality of diesel-biodiesel with and without dissolved gas in this paper.The PDPA measurement system was used to test mixed fuel with different volume ratios(B0、B30、B50、B70、B100)at nozzle diameters of 0.24 and 0.30 mm.The axial velocity and particle size distribution were measured and analyzed.Further,based on the mixed fuel,different volumes of CO2 were dissolved therein,and the percentage of dissolved gas in volume was 5.74%,12.73%and 26.42%,respectively,and the atomization quality of the fuel containing CO2 was measured at nozzle diameters of 0.24 and 0.30 mm.The results showed that at a nozzle diameter of 0.24 mm and 0.30 mm,the sauter mean diameter(SMD)of the biodiesel was greater than that of diesel,the average diameter of diesel fuel was 25μm lower than that of biodiesel at the axial length of 70 mm,the atomization quality of the mixed fuel was obviously improved compared with that of biodiesel,with the decrease of nozzle diameter,the atomization quality was greatly improved.When the volume content of CO2 was 26.42%(C26.42),the droplet size at the axial length of 70 mm was 13.1μm smaller than that of B50.The droplet size of the B50 with dissolved gas volume ratio of 5.74%(C5.74)and 12.73%(C12.73)was 5.3 and 12.2μm higher than that of B50 at the axial length of 70 mm,respectively.When the nozzle diameter was reduced from 0.30 mm to 0.26 mm,C5.74 and C12.73 had a greater inhibitory effect on atomization and the SMD increased by 8.43%and 6.82%,respectively.The atomization quality of C26.42 was enhanced as the nozzle diameter reduced and the SMD was decreased by 26.5%.The fuel that contains a small amount of CO2 had a larger SMD than that of the fuel without dissolved gas,and the inhibition effect on atomization was more obvious with the decrease of nozzle diameter.When the amount of dissolved gas was high,the atomization quality was promoted,and with the decrease of nozzle diameter,the promotion effect was enhanced.This study showed that dissolved gas can improve the atomization quality of biodiesel under certain conditions,dissolved gas in mixed fuel can overcome the disadvantages of high viscosity and density of biodiesel,improve the atomization quality of biodiesel and improve its combustion effect,biodiesel can be better used in internal combustion engines.