Abstract
Motor vehicles rolling in urban conditions dissipate a considerable amount of energy in the braking process. Therefore one of the main ways of decreasing fuel consumption consists of recuperating the energy lost by motor vehicle braking, storing and reusing this energy for propulsion in difficult operating conditions, such as the phases of acceleration, thus enhancing vehicle performances.
For this purpose, vehicles with internal combustion engine must be equipped with an additional propulsion system. A hybrid system solution capable of regenerating the braking energy uses a hydropneumatic accumulator for energy storage and a reversible hydraulic unit for energy retrieval. These components have to be chosen according to motor vehicle specifications and operating conditions, so that energy saving is optimal.
The dynamic behaviour and fuel consumption of a commercial vehicle equipped with a hydropneumatic regenerative braking system were modelled. Four different configurations of the hydropneumatic system were modelled.
The dynamic behaviour of the vehicle was simulated both in absence of the regenerative braking system and in case of hydro-pneumatic system operation, in which simulations of acceleration were performed for the vehicle propelled exclusively by the fully loaded hydro-pneumatic system.
The propulsion potential was emphasized for each of the four system configurations. The system capacity of energy retrieval and storage depends on the sizes of the hydraulic unit and of the accumulator. Vehicle dynamic properties are strongly influenced by the parameters of the hydropneumatic system.
Keywords: regenerative braking, hybrid vehicle, drive cycle, fuel consumption, computer simulation