Automotive Science and Engineering

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This study uses real driving cycles of a city bus and a standard driving cycle “WLTP” to implement a full comparison for energy demand and fuel consumption for different propulsion systems (i.e., Diesel ICE, Fuel cell and Electric engines). To better understand the comparison, a life cycle assessment is conducted using “GREET” and “GHGenius” software, which represents a clear demonstration of side effects and emissions of each engine on the environment. The results show that for “WLTP” cycle the bus needs 2423kJ energy for traveling each kilometer while the averaged amount of energy for traveling one kilometer of real driving cycle reaches to 1708kJ. By computing total energy use of  an electric bus we conclude, electric buses use almost 58% of electric energy for driving and the rest is lost. Then fuel cell and internal combustion engine buses have energy efficiency of 36% and 24% respectively. Concerning LCA analysis, it becomes apparent that unlike efficiency, electric buses are not environmentally benign as fuel cell buses. LCA analysis showed that fuel cell buses that use steam reforming hydrogen production process are a cleaner option than electric buses. Finally, since diesel buses produce the most emission, especially CO2, and consume the most energy in the total life cycle, they have no advantage for public transportation fleet.

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This paper introduces a novel powertrain system composed of a liquid ammonia internal combustion engine, a dissociation and separation unit, and a PEM fuel cell system developed for vehicular applications. Using a carbon-free fuel for the ICE and producing hydrogen on board for PEMFC use significantly enhance this novel systemchr('39')s environmental effects. The thermodynamic analyses are conducted using EES and MATLAB software. The results show that while this hybrid powertrain system produces 120 kW output power, energy and exergy efficiencies are 45.2% and 43.1%, respectively. The overall exergy destruction rate of the system becomes 237.4 kW.The fuel consumption, engine speed, and battery state of charge (SoC) analyses are calculated using three driving cycles. These vehicles consume 7.9, 5.7, and 7.7 liters of liquid ammonia per 100 km in FTP-75, NEDC, and HWFET driving cycles, respectively. The battery state of charge differentiation in these three cycles shows the practicality of this novel powertrain system specially in inner-city driving cycles as the battery does not confront any intense decline of SOC to the minimum level. HWFET results show the great dependence of the vehicle on ICE and low PEM fuel cell function, which results in releasing decomposed hydrogen to the environment.

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Environmental pollution and reduction of fossil fuel resources can be considered as the most important challenges for human society in the recent years. The results of previous studies show that the main consumer of fossil fuels and, consequently, most of the air pollutants, is related to the transportation industry and especially cars. The increasing growth of vehicles, the increase in traffic and the decrease in the average speed of inner-city vehicles have led to a sharp increase in fuel consumption. To address this problem, automakers have proposed the development and commercialization of hybrid vehicles as an alternative to internal combustion vehicles. In this paper, the design of an energy management system in a fuel-cell hybrid vehicle based on the look-ahead fuzzy control is considered. The preparation of fuzzy rules and the design of membership functions is based on the fuel efficiency curve of the fuel-cell. In look-ahead fuzzy control, the ahead conditions of the vehicle are the basis for decision in terms of slope and speed limit due to path curves as well as battery charge level. The fuzzy controller will determine the on or off status of the fuel-cell, as well as the power required. The motion of the fuel-cell hybrid vehicle on a real road is simulated and the performance of the proposed look-ahead controller is compared with the base controller (thermostatic method). The simulation results show that using the proposed approach can reduce the fuel consumption of the fuel-cell hybrid vehicle as well as travel time.