Fuel economy and emission of hybrid electric bus

Abstract

A hybrid electric bus (HEB) was tested on heavy-duty chassis dynamometer to explore its fuel consumption and emissions under two different driving cycles, respectively Chinese City Bus Cycle (CCBC) and World Transient Vehicle Cycle (WTVC). During the process of tests, a set of on-board test equipment for fuel consumption and gaseous pollutants measurement was employed. Fuel consumption and emissions under cold and hot test conditions were measured; Fuel consumption per 100 km and emission factors of THC, CO and NOx under two cycles were compared; And contribution rates of different driving models to gaseous pollutants were also studied. Test results showed, Under cold test condition, fuel consumption was nearly the same as that under hot test condition, but emissions of HEB were much worse than those under hot condition, among HC, CO and NOx, HC emissions was the most serious under cold test condition. Fuel economy and emissions of HEB were sensitive to driving cycles. Fuel economy of HEB under WTVC was better than that under CCBC. Fuel consumption per 100 km under WTVC was 83.3% of that under CCBC, while emissions of pollutants were worse than those under CCBC, THC and NOx mileage emission factors under WTVC were 2.1 times, 1.9 times as high as those under CCBC separately. Contribution rates of accelerating models to all kinds of gaseous pollutants were the highest, the lowest were those of idle models. Contribution rates of accelerating models to THC and NOx were 2.2~2.7 times, 1.7 times and 1.5 times higher than those of idle modes, decelerating modes and cruise modes respectively, contribution rate of CO under accelerating modes was about 70%. Under decelerating modes, engine fuel injection quantity decreases rapidly to the lowest, so contribution rates of decelerating modes of gaseous pollutants were lower than those under cruise modes.