Characterization of Driving Pattern of CNG Inter City Buses and Development of New Real World Driving Cycle and Comparison with Regulatory Driving Cycles 2019-01-0927
The New Delhi city which is the capital of India is one of the most polluted cities in the world. The policy makers have implemented various control measures, such as mandatory use of CNG fuel by all commercial vehicles in place of diesel. There has been reports which concludes a gap between real world driving cycles and regulatory driving cycle used for type approval emission testing of vehicles in a laboratory. Development of real world driving cycle for intra-city CNG buses is of great importance for energy economy and emissions performances tests, as well as evaluation of control strategy of using CNG as an alternative fuel over diesel fuel using modelling approach.
In this study, speed and position of the buses were collected, using Automated Vehicle Location (AVL) system in synchronization with global positioning systems (GPS) and data loggers. These driving data were used for development of new driving cycles by applying micro trip-based method. These newly developed driving cycles were modelled in International Vehicle Emission Model for estimating both regulated and unregulated emissions. This study also comprehensively compares real world driving parameters and emission characteristics with two regulatory cycles, i.e., European Transient Cycle (ETC) cycle and World Harmonized Transient Cycle (WHTC) cycles. The Emissions simulation were also carried out for both CNG and diesel fuel by considering appropriate category of vehicles to assess the advantage of one fuel over other for different pollutants.
It is shown in the study that real-world driving parameters and emissions are different as compared to standard driving cycles. The real world driving average speed was around 18~22 km/h in comparison to 40 km/h and 59 km/h for ETC and WHTC cycle, respectively. The Real world average VOC emission were simulated 0.040 g/km with respect to 0.031 g/km for ETC and 0.0275 for WHVC cycle. The PM emission were much lower for CNG fuel (Avg-0.0049 g/km) as compared to 0.54 g/km for diesel fuel and CO emissions were observed 6.60 g/km for CNG and 0.20 g/km for diesel fuel. However, for most of the emissions WHVC cycle better represented real-world driving emissions of CNG buses driving pattern as compared to ETC cycle.