基于车载诊断系统的轻型乘用车实际道路油耗特征分析

近年来的一系列研究表明,轻型车实际道路油耗与型式认证油耗间的差异在不断增大,之前的实际道路油耗研究大多基于用户上报数据或车载排放测试系统(PEMS).车载诊断系统(OBD)是一种监测发动机及排放控制系统实时工作状态的仪器.本研究通过OBD解码器采集瞬时发动机进气量计算机动车瞬态油耗并通过2辆轻型汽油车的实验室台架测试证明该方法具有很好的准确性(差异在±5%以内).本研究进一步在北京选取了7辆轻型汽油车,利用OBD解码器开展实际道路油耗测试,并研究运行工况及车辆载重对其实际道路油耗的影响.实际道路结果显示测试车辆在典型工况下的油耗比型式认证油耗高23.1%~46.4%,平均差异为29.2%.通过微观运行模态方法将实际道路油耗修正到法规测试循环(NEDC工况)的交通特征下,道路油耗仍然比型式认证油耗高18.7%±7.1%.研究表明,平均速度与实际道路油耗具有很强的相关性.实际道路油耗在30 km·h-1以下时会随速度降低而显著上升.此外,研究还发现如果车辆载重增加260 kg,实际道路油耗将上升6.2%±2.2%.

Characterizing real-world fuel consumption for light-duty passenger vehicles by using on-board diagnostic (OBD) systems

In recent years, a series of studies have reported that the discrepancy between real-world and type-approval fuel consumption levels for light-duty gasoline vehicles (LDGVs) is increasing. These studies were mostly based on users'' reported data or portable emission measurement system (PEMS). On-board diagnostic (OBD) is a device that is capable of monitoring real-time operating conditions of engine and exhaust control systems. Through instantaneous engine mass air flow rate data collected by the OBD decoder, the real-world vehicle fuel consumption is calculated in this paper, and the accuracy is proved (e.g., discrepancy less than ±5%) in this study according to the comparative tests for 2 LDGVs in a well-controlled laboratory. Furthermore, 7 LDGVs were tested on-road in Beijing using OBD decoders, and the impacts of driving conditions and loading mass on their real-world fuel consumption were further studied. Our results indicate that the real-world fuel consumption levels of tested vehicles were 23.1%~46.4% higher than their type-approval fuel consumption values, with an average discrepancy of 29.2%. Using an operating mode binning methodology, this study reveals that the on-road fuel consumption was 18.7%±7.1% higher than type-approval fuel consumption after being normalized to the traffic pattern of New European Driving Cycle (NEDC). A strong correlation has been identified between average speed and real-world fuel consumption. The relative fuel consumption would dramatically increase when the average speed becomes increasing lower than 30 km· h^-1. In addition, this study also indicates that the real-world fuel consumption would be up by 6.2%±2.2% if the loading mass is increased by 260 kg.