Study On Emission Characteristics Of CNG/Gasoline Dual-Fuel Taxi

Under the background of promoting energy conservation and emissions reduction and advocating CNG taxi, this paper is a study on the characteristics of dual fuel taxis’emission in Nanjing. The Portable Emission Measurement System (PEMS) and Chassis dynamometers tests were used to carry out the experiments for the emission of dual fuel taxi. A vehicle emission model was built, based on the analysis of the emissions differences between CNG and gasoline dual fuel taxis under various conditions.Firstly, taxis were chosen to obtain the vehicle using the SEMTECH PEMS operated on different roads in Nanjing. And a total of 20,000 sets of CNG taxi and 14,000 sets of gasoline fuled taxi of data were acquired, including the instantaneous emissions of CO2, CO, NOx,HC, taxi speed, altitude and other parameters. Besides, Acceleration Simulation Mode(ASM) is applied to test the emissions of dual fuel taxi on chassis dynamometers by the AVL machine.Secondly, the characteristics of dual-fuel taxis’ emissions in Nanjing are analyzed on the basis of measured data. It is found that the instantaneous emissions of CO2, CO, NOx, HC,which come from CNG and gasoline taxis, change similarly with the variable speeds and accelerations, although the instantaneous emissions of CO2, CO from the gasoline taxi was higher than that from CNG taxi obviously. The relationship between Vehicle Specific Power(VSP) distribution and the emission of dual taxis in Nanjing is analyzed. It shows that the VSP distribution of dual-fuel taxis has a tendency of concentrating in the vicinity of zero, and about 95% of the data is located in the interval of-10kw/ton to 10kw/ton. The emission rates are lower and more stable when VSP is negative. And when VSP is positive, the emission rates would monotonically increase with the increasing VSP. The relationship between emission rates and vehicle speed is similar under various conditions, which means that the on-road test and the chassis dynamometer test using ASM, but the relative error of PEMS and AVL is higher.Finally, the dual taxi emission characteristics are analyzed and the emission models of dual taxi are built by the regression method and neural network method that were based on speed and acceleration and some other parameters. The model was compared with the IVE, and the results tell that the model can predict the emission rates of dual-fuel taxi effectively.