Progress in Energy and Combustion Science最新文献

Carbon capture and storage is recognized as one of the most promising solutions to mitigate climate change. Compared to conventional separation technologies, supersonic separation is considered a new generation of technology for gas separation and carbon capture thanks to its advantages of cleaning and efficient processes which are achieved using energy conversion in supersonic flows. The supersonic separation works on two principles which both occur in supersonic flows: the energy conversion to generate microdroplets and supersonic swirling flows to remove the generated droplets. This review seeks to offer a detailed examination of the cutting-edge technology for gas separation and carbon dioxide removal in the new-generation supersonic separation technology, which plays a role in carbon capture and storage. The evaluation discusses the design, performance, financial feasibility, and practical uses of supersonic separators, emphasizing the most recent progress in the industry. Theoretical analysis, experiments, and numerical simulations are reviewed to examine in detail the advances in the nucleation and condensation characteristics and the mechanisms of supersonic separation, as well as new applications of this technology including the liquefaction of natural gas. We also provide the perspective of the challenges and opportunities for further development of supersonic separation. This survey contributes to an improved understanding of sustainable gas removal and carbon capture by using the new-generation supersonic separation technology to mitigate climate change.

Solid oxide fuel cells (SOFCs) have witnessed significant advancements in recent years, emerging as potential alternatives to low-temperature fuel cells for mobile applications owing to their wide fuel flexibility and high efficiency. This paper offers a comprehensive assessment of the progress achieved thus far and the challenges faced in transitioning from stationary to mobility sectors. Three pivotal aspects are highlighted across different levels: enhancing fuel tolerance and flexibility at the anode level, achieving rapid start-up at the cell level, and realizing compact integration at the stack level. This review can lay a theoretical foundation for the development of SOFC systems tailored to unique requirements, such as high power density and rapid start-up, crucial for mobile applications. This review will facilitate commercial breakthroughs and advances in the mobility of SOFCs, which holds substantial strategic importance.

Solar and other renewable energy driven gas-solid thermochemical energy storage (TCES) technology is a promising solution for the next generation energy storage systems due to its high operating temperature, efficient energy conversion, ultra-long storage duration, and potential high energy density. Experimental and theoretical studies suggest that the respective gravimetric and volumetric TCES energy storage densities vary from 200 to 3000 kJ kg⁻¹ and 1–3 GJ m⁻³. Solar radiation or heat generated from electric furnaces powered by renewable electricity can be stored in the form of chemical energy through endothermic reactions, while the stored chemical energy can be converted to thermal energy via an exothermic reaction when needed. The design of highly effective reactors requires a deep understanding of materials, thermodynamics, chemical kinetics, and transport phenomena. At time of writing, TCES reactors are yet to be deployed at commercially relevant scales, leaving a substantial gap between development efforts and commercial feasibility. Therefore, this review aims to examine the state-of-the-art design and performance of particle-based TCES reactors with different reactive materials. Fundamentals related to TCES reactive materials, reaction conditions, thermodynamics and kinetics, and transport phenomena are reviewed in detail to provide a comprehensive understanding of the reactor design and operation. Five major types of TCES reactors have been comprehensively reviewed and compared, including fixed, moving, rotary, fluidized, and entrained bed reactors. Most reported prototype reactors in the literature operate at lab scale with thermal inputs below 40 kW, and scaled TCES reactors (e.g., at megawatt level) are yet to be demonstrated. The nominal reactor operating temperatures range from 300 to 1500 °C, depending on the selected chemistry, reactive material, and heat sources. To evaluate their designs, the reactors are assessed in aspects of performance, cost, and durability. Discrepancies in performance indicators of energy storage density, extent of reaction, and various energy efficiencies are highlighted. The scale-up of reactors and power block integration, which hold the key to the successful commercialization of TCES systems, are critically analyzed. Advanced materials (both reactive materials and ceramic reactor housing materials), effective particle flow control, advanced modeling tools, and novel system design may bring significant improvement to the energy efficiency, storage density and cost competitiveness of particle-based TCES reactors.

This article describes the combustion behavior of combustible gases as they are released from the clathrate cages of a hydrate. Gas hydrates (clathrates) are ice-like crystalline solids that encapsulate guest gas molecules. It has become known that a significant methane storehouse is in the form of methane hydrates on the sea floor and in the arctic permafrost. There is great interest in this large fuel storehouse, particularly how to extract the methane from the clathrates. One of the unique features of methane clathrate is that it is flammable, despite being 85% water – fiery ice. While methane clathrates are the most prevalent in nature, other combustible gas hydrates (notably, propane and hydrogen) also have potential energy technology implications. In addition, carbon-dioxide hydrates have been proposed as a potential post-combustion greenhouse gas sequestration strategy, and there is a wide range of separation technologies and thermal management that take advantage of the unique thermodynamic and kinetic features of hydrate formation. To better understand the important implications of direct utilization of fuel clathrates and the related potential environmental consequences of CO₂ hydrates, we describe the state-of-the-art knowledge regarding the formation and structure of gas hydrates, and the combustion behavior of flammable gas hydrates. The combustion studies involve determining the rate of ice melt and water evaporation during the hydrate burn, as well as the interesting phenomenon of self-healing, where the hydrates stop burning by forming an ice sheet on their surface. Experimental results are used to estimate the heat transfer from the flame into the hydrate and to calculate the amount of energy released to sustain the flame. This article provides the reader with a comprehensive understanding of the basics and the subtleties of hydrates and their combustion, thereby explaining the true meaning of fiery ice.

Progress in recent years has opened the door for yet another area of application for the lattice Boltzmann method: Combustion simulations. Combustion is known to be a challenge for numerical tools due to, among many other reasons, a large number of variables and scales both in time and space. The present work aims to provide readers with an overview of recent progress and achievements in using the lattice Boltzmann method for combustion simulations. The article reviews some basic concepts from the lattice Boltzmann method and discusses different strategies to extend the method to compressible flows. Some of the lattice Boltzmann models developed to model mass transport in multi-species system are also discussed. The article provides a comprehensive overview of models and strategies developed in the past years to simulate combustion with the lattice Boltzmann method and discuss some of the most recent applications, remaining challenges and prospects.

Conventional diesel combustion is a mixing-limited process that passes through high temperature and fuel-rich zones, leading to oxides of nitrogen (NO_x) and particulate matter (PM) formation. Simultaneous reduction of NO_x and PM is difficult due to NO_x-PM trade-off. As alternative fuels, emulsions of water-in-diesel offer several advantages, including a simultaneous reduction in NO_x and PM formation. There are, however, disparities in the reported engine performance and emission characteristics, as they appear to depend on the constituents and microstructure of the emulsion fuel used and engine conditions. Studies on engine performance and exhaust emissions were often carried out without adequate characterization of the emulsions. Therefore, the paucity of cohesive data can be circumvented by standardizing the protocols for emulsion fuels, tailoring their morphology, structure, and characterization, and optimizing engine conditions. This review article recapitulates the salient features of emulsion fuels, from their synthesis, microstructure, characterization, and macroscopic spray characteristics to performance and emissions in diesel engines. A critical analysis of the current state of knowledge is also presented, emphasising the tunability of droplet size and characterization of emulsion stability. The review concludes by suggesting the path forward to utilizing emulsion fuels.

Capturing CO₂ from air (DAC) is becoming an attractive technological route to face the climate crisis. This paper reviews the existing research efforts to integrate DAC with conversion technologies to transform the captured CO₂ into chemicals or fuels. The approach can potentially lead to net zero carbon emissions, thus being of interest in a circular economy framework. A growing amount of research has been devoted to the combination of DAC with CO₂ conversion, leading to creative strategies which start to be scaled up. In this review, we have critically analysed the existing approaches by the degree of process integration. From the point of view of process intensification, the integration of both capture and reaction in the same vessel can potentially lead to equipment and energy cost savings besides other synergistic effects. In this vessel, the DAC and conversion can occur either in consecutive stages with change of feed or spontaneously in a cascade reaction without changing the conditions. As a side effect, the benefits entailed by process intensification in different levels of integration may be a decisive driving force for the widespread deployment of DAC. This paper discusses the ongoing research and perspectives to guide researchers in this promising new field.