Predicting vehicle waste heat recovery potential in road gradient driving cycle - A case study

Abstract

A commercial vehicle was instrumented for assessing the engine operation modes on a mountain route in Romania, in a 70.4 km round trip with mean road gradients +4.2% and -4.5%. The real world test cycle was processed to find the distribution of the most frequent engine operation modes (time intervals versus n × n speed and load rankings) in order to extract a steady-state gradient road cycle. The direct injection turbocharged diesel engine has been tested on the dynamometric brake in the selected operation modes, investigating the energy recovery potential of the exhaust system. An exergy analysis has been performed by processing the variables of the exhaust gas flow rates for each operation mode (gas composition, pressure and temperature) which have been weighted with the time share of each mode in the driving cycle. The exergy exhaust potential has been evaluated by means of several indicators such as mean weighted exergy rate, weighted exergy to energy ratio and weighted exergy to fuel exergy ratio. By comparing the results to local urban and extra-urban cycles from previous works, it has been revealed that the gradient road cycle has a higher energy potential than the urban cycle, but a lower one than the extra-urban cycle.