Coal is the most abundant fossil fuel and is widely used as an energy source for combustion and gasification. Both experimental methods and computational tools are required for the development of new advanced, innovative clean coal technologies and systems. In particular, 3D computational fluid dynamics (CFD) simulations can provide detailed local and global information on the interaction of fluid dynamics, mixing, and heterogeneous and homogeneous chemical reactions even for complex systems such as combustors, gasifiers, or chemical reactors. The predictive capabilities of CFD simulations depend directly on appropriate models and their mutual interactions. The current state of modeling is reviewed in this paper and the need for further improvements of both individual models and their respective coupling is addressed. In addition, to evaluate and validate the models and their interactions, systems with increasing complexity and well-defined boundary and operating conditions are required that can provide suitable experimental data. A number of reference burners and combustors, developed especially at universities and research institutions, are also presented and recent simulation data for these systems is reviewed.

The Co-Optimization of Fuels and Engines (Co-Optima) initiative from the US Department of Energy aims to co-develop fuels and engines in an effort to maximize energy efficiency and the utilization of renewable fuels. Many of these renewable fuel options have fuel chemistries that are different from those of petroleum-derived fuels. Because practical market fuels need to meet specific fuel-property requirements, a chemistry-agnostic approach to assessing the potential benefits of candidate fuels was developed using the Central Fuel Property Hypothesis (CFPH). The CFPH states that fuel properties are predictive of the performance of the fuel, regardless of the fuel's chemical composition. In order to use this hypothesis to assess the potential of fuel candidates to increase efficiency in spark-ignition (SI) engines, the individual contributions towards efficiency potential in an optimized engine must be quantified in a way that allows the individual fuel properties to be traded off for one another. This review article begins by providing an overview of the historical linkages between fuel properties and engine efficiency, including the two dominant pathways currently being used by vehicle manufacturers to reduce fuel consumption. Then, a thermodynamic-based assessment to quantify how six individual fuel properties can affect efficiency in SI engines is performed: research octane number, octane sensitivity, latent heat of vaporization, laminar flame speed, particulate matter index, and catalyst light-off temperature. The relative effects of each of these fuel properties is combined into a unified merit function that is capable of assessing the fuel property-based efficiency potential of fuels with conventional and unconventional compositions.

Electric vehicles play a crucial role in reducing fuel consumption and pollutant emissions for more sustainable transportation. Lithium-ion batteries, as the most expensive but least understood component in electric vehicles, directly affect vehicular driving range, safety, comfort, and reliability. However, the overall performance of traction batteries deteriorates significantly at low temperatures due to the reduced electrochemical reaction rate and accelerated health degradation, such as lithium plating. Without timely and effective actions, this performance degradation causes operational difficulties and safety hazards for electric vehicles. Battery warm-up/preheating is of particular importance when operating electric vehicles in cold geographical regions. To this end, this paper reviews various battery preheating strategies, including external convective and conductive preheating, as well as the latest progress in internal heating solutions. The effects of low temperature on batteries from the perspectives of cell performance as well as materials properties are briefly summarized. Thermal science issues involved in warm-up are also elucidated. The framework of battery management systems (BTMS) at low temperatures, including the key design considerations at different battery integration levels and the overall classification of warm-up approaches into external and internal groups, are introduced in detail. Next, a comprehensive literature review on different warm-up strategies is presented, and the basic principles, advantages, disadvantages, and potential improvements of each strategy are elaborated. Finally, future trends of battery warm-up methods are discussed in terms of key technologies, promising opportunities, and challenges.