不同海拔下VGT对含氧燃料柴油机性能的影响

利用大气压力模拟装置,试验研究了可变几何截面涡轮增压器(VGT)对高压共轨柴油机分别燃用纯柴油和生物柴油-乙醇-柴油(BED)含氧燃料的经济性、排放特性及燃烧特性的影响。结果表明:随着海拔的升高,柴油机经济性恶化,氮氧化物(NO_x)排放降低,而一氧化碳(CO)和碳氢化合物(HC)排放及烟度升高。燃用纯柴油与含氧燃料,随着VGT喷嘴环开度的增大,柴油机的经济性均有不同程度的恶化,而CO、HC排放及排气烟度也都有不同程度的升高。在高海拔地区,燃用纯柴油的经济性优于含氧燃料,但使用含氧燃料有助于改善柴油机的CO、HC排放及烟度。在中等负荷工况下,NO_x排放随着VGT喷嘴环开度的增大呈现先减小后增大的趋势;在高负荷工况下,放热率峰值和最高气缸压力均随着VGT喷嘴环开度的增大而降低,从而降低了NO_x排放。

Effect of VGT on Diesel Engine Performance Using Oxygenated Fuel at Different Altitudes

The effect of the variable geometry turbocharger(VGT) on fuel economy, emissions and combustion characteristics of a high pressure common rail diesel engine using straight diesel and biodiesel-ethanol-diesel (BED) fuel at different altitudes was investigated by an atmospheric pressure simulation system. Results show that the elevation of altitude leads to a deterioration, of fuel economy coupled to the reduction of nitrogen oxide(NOx) emissions and hence the increase of carbon monoxide(CO), hydrocarbon(HC) and soot emissions. With the increase of the opening area of the turbocharger nozzle ring, the specific fuel consumption goes up. While the emissions of CO, HC and soot increase to varying degrees when using straight diesel and oxygenated fuel separately. In the high altitude area, the fuel economy of the straight diesel operation is better than that of the oxygenated fuel operation, but using oxygenated fuel can help apparently improve the emissions of CO, HC and soot. Under medium load conditions, the NOx emissions decreases first and then increase with the rise of the opening area of turbocharger nozzle ring. However, under high load conditions, the heat release rate and maximum cylinder pressure will fall with the increase of the opening area of nozzle ring, thus reducing the NOx emissions.