面向排放量化的低速区间机动车比功率分布特性与模型

随着排放建模方法从基于行驶周期和平均速度演变为基于VSP(Vehicle Specific Power)参数,利用VSP分布刻画交通状态成为最新的研究需求.近期研究中,针对城市快速路上大于20 km·h-1的速度区间建立了基于平均行程速度的VSP分布数学模型,却未对低速区间的VSP分布特征作深入研究.基于北京快速路大量逐秒浮动车数据,研究0～20 km·h-1的VSP分布与平均行程速度的关系.通过分析大量逐秒浮动数据的VSP分布与平均速度间关系,发现VSP分布与平均行程速度具有规律性:各VSP分布的峰值出现在VSP Bin=0处,且随速度的增加单调递减.因此,针对VSP分布的正、负区间以及VSP Bin=0处分别建立数学模型,并利用该模型进行机动车油耗/排放测算.对比分析油耗/排放的预测值和实测值得出,所建立的VSP分布模型可以有效用于机动车油耗/排放测算.

Distribution characteristics and model of low-speed vehicle specific power for emission quantification

With the recent evolution of the emission modeling approach using from the average speed associated with the driving cycle to the parameter Vehicle Specific Power (VSP), a new direction has emerged to characterize traffic conditions by using the VSP distribution. For the average travel speed higher than 20 km·h^-1, an applicable mathematical model describing the VSP distributions is available. However,for the average travel speed lower than 20 km·h^-1, the characteristics of VSP distribution are still unclear. In this context, we use large samples of second-by-second floating car data to associate the VSP distributions with the average travel speed. Regular patterns are found between the VSP distribution and the average travel speed. Specifically, the highest fraction always appears in the VSP bin of 0, which decreases monotonically with the increase of the average travel speed. Based on the separate analysis of VSP fractions in negative, 0, and positive VSP Bins, a mathematical model of VSP distribution is proposed. By comparing the estimated fuel consumption and emissions with the actual fuel consumption and emissions, the result demonstrates that the proposed VSP distribution model is reliable and accurate for the estimation of fuel consumptions and emissions.