提高重型柴油机低速高负荷热效率的试验研究

为了改善重型柴油机低速高负荷的燃油经济性,在一台两级可变截面涡轮增压重型柴油机上开展了空气系统与喷油参数优化策略研究。试验结果表明:对于缸内最高燃烧压力受限工况,获得最低有效燃油消耗率(BSFC)的可变截面涡轮增压器(VGT)关度应该使泵吸功基本为零;选取合适的喷油压力可提高机械效率,在改善燃油经济性的同时使NO_x排放有一定降低,而碳烟排放也能保持在较低水平。基于该优化策略,研究了缸内最高燃烧压力限值对不同工况点燃油经济性的影响,进而研究了提高缸内最高燃烧压力对改善燃油经济性的潜力。结果表明:随着转速与负荷的升高,提高最高燃烧压力限值对燃油经济性的改善作用更加明显;但缸内最高燃烧压力提高到一定程度以后,其对燃油经济性的改善作用逐渐减小。

Experimental Study for Improving Thermal Efficiency of a Heavy Duty Diesel Engine at Low Speed and High Load

In order to improve the fuel economy of a heavy duty diesel engine at low speed and high load, study on the optimization strategy of intake air system and fuel injection parameters was carried out on a two-stage variable geometry turbocharged heavy duty diesel engine. Results show that in the case of limiting the maximum burst pressure in the cylinder, the turbocharger vane can be adjusted to achieve the lowest fuel consumption only when the pumping loss is substantially zero. Moreover, choosing a right injection pressure can increase mechanical efficiency and improve fuel economy, while reducing NOx emissions and keeping soot emissions low. Based on the optimization strategy proposed in the above study, the influence of maximum burst pressure in the cylinder on the fuel economy under different operating conditions was studied, and the potential of increasing maximum burst pressure in the cylinder to improve fuel economy was further explored. Results show that as speed and load increase, the advantage of increasing the maximum burst pressure limit is more obvious for improving fuel economy. However, after the maximum burst pressure is increased to a certain extent, its effect on improving fuel economy will gradually decrease.