A Purely Mechanical Energy Storing Concept for Hybrid Vehicles
The paper contains the design and simulation of a purely mechanical system for storing energy during vehicle deceleration, which can be utilized during subsequent acceleration (regenerative braking). A continuously variable transmission (CVT) regulates the energy transfer, energy storage is accomplished by means of a spiral spring and additional use of a planetary transmission. The transmission ratio of the CVT is adapted by a combined feed-forward and feed-back control. A computer simulation for a vehicle with an overall mass of 1500kg, and an energy storage capacity of 30kJ was performed for different driving cycles. In a typical urban stop and go situation the proposed device will save up to 0.72kg fuel per 100km and the overall efficiency analysis together with simple design, easy recycling, and long life expectance, showed a clear advantage over other hybrid concepts for frequent stops and accelerations.
Energy recovery systems for retrofitting in internal combustion engine vehicles: A review of techniques
Energy recovery systems (ERSs) for internal combustion engine vehicles (ICEVs) are reviewed in the context of fuel efficiency improvement and retrofit capabilities. The paper presents technical knowledge on the potential benefits that retrofitted ERSs may achieve in carbon emissions reduction. A first distinction of ERSs is made between the sources of the energy and further sub-divided on the technique to harvest and store the energy. A critical evaluation is performed on the associated characteristics such as weight, size and cost. Finally, the paper summarizes the ERSs technologies under a number of common criteria, and finds out, that the most effective ERSs in terms of fuel efficiency are the ones more difficult to retrofit. Further research is suggested to investigate the trade-off between fuel consumption reduction and investment cost of the system.
Effect of superficial gas velocity on the particle temperature distribution in a fluidized bed with heat production
The heat transfer behavior of particles and gas in an olefin polymerization fluidized bed was numerically analyzed using an in-house developed 3-D computational fluid dynamics discrete element model (CFD-DEM). First the implementation of the model was verified by comparing simulation results with analytical results. A constant volumetric heat production rate was implemented in the particle energy equation to mimic the heat production due to the polymerization reaction. It was found that the probability density function (PDF) of the particle temperature becomes more homogeneous with increasing superficial gas velocity. Furthermore, instantaneous snapshots of the thermal driving force (the difference between the single particle temperature and bed-average gas temperature, Tp− ) for different heat production rates provide detailed insight in the particle temperature distribution inside the fluidized bed. The time- and bed-averaged particle convective heat transfer coefficient, which was calculated by Gunn׳s correlation, was found to be independent of the superficial gas velocity. This is explained by the fact that the relative velocity of gas and particles in the emulsion phase, where most of the particles and gas interact, is hardly influenced when increasing the gas superficial velocity. From the spatial distribution of Nusselt number, it becomes apparent that the high heat transfer regions are found in the wake of rising bubbles, whereas low heat transfer rates are found in the clouds of the bubbles.