Progress in Energy and Combustion Science最新文献

Hydrogen is a promising future energy carrier due to its potential for production from renewable resources. It can be used in existing compression ignition diesel engines in a dual-fuel mode with little modification. Hydrogen's unique physiochemical properties, such as higher calorific value, flame speed, and diffusivity in air, can effectively improve the performance and combustion characteristics of diesel engines. As a carbon-free fuel, hydrogen can also mitigate harmful emissions from diesel engines, including carbon monoxide, unburned hydrocarbons, particulate matter, soot, and smoke. However, hydrogen-fueled diesel engines suffer from knocking combustion and higher nitrogen oxide emissions. This paper comprehensively reviews the effects of hydrogen or hydrogen-containing gaseous fuels (i.e., syngas and hydroxy gas) on the behavior of dual-fuel diesel engines. The opportunities and limitations of using hydrogen in diesel engines are discussed thoroughly. It is not possible for hydrogen to improve all the performance indicators and exhaust emissions of diesel engines simultaneously. However, reformulating pilot fuel by additives, blending hydrogen with other gaseous fuels, adjusting engine parameters, optimizing operating conditions, modifying engine structure, using hydroxy gas, and employing exhaust gas catalysts could pave the way for realizing safe, efficient, and economical hydrogen-fueled diesel engines. Future work should focus on preventing knocking combustion and nitrogen oxide emissions in hydrogen-fueled diesel engines by adjusting the hydrogen inclusion rate in real time.

Polyaromatic hydrocarbons, polycyclic aromatics or polyarenes are a major (by-)product fraction of multiple classical, waste, and bio-refinery operations. They have an extremely negative environmental impact, a minimal market, and a lowering demand. Parallelly, lowly alkylated single ring arenes or monoaromatics (benzene, toluene, and xylenes, the so-called BTX fraction) are highly demanded due to their applications as chemicals or fuels. Herein, we review the status of applied polyaromatic selective ring-opening (SRO) by hydrocracking into monoaromatics. This review addresses the involved mechanisms, applicable catalysts, and reported modeling approaches for SRO. Applying the multivariate analysis to the results reported in the literature using model molecules, we showcase the limitations for extrapolating the obtained knowledge to realistic polyaromatic stream processing. We also provide a statistical evaluation of the suitability of several polyaromatic streams for their SRO processing and assess the markets, usage, and production routes for monocyclic aromatics. Finally, the technologies of these processes are also evaluated and compared, while the most promising one is discussed further based on process simulations and a techno-economic assessment.

Turbulence is an effective way to spread particles and drops in a fluid, which is critical for many energy systems, ranging from carbon-based power-production to spray cooling for renewable energy storage. Combining the intricacies of turbulence with the complexities of particle motion has led to numerous advances, especially in the last two decades in terms of turbulent bias, and turbulence modulations, as well as experimental confirmation of previous theories regarding turbulent diffusion and turbulent particle collisions. In this review, the fundamental features of turbulence are related to key Stokes numbers that describe one-way coupling (influence of turbulence on particle motion). This includes turbulent diffusivity for a range of inertias and drift parameters, as well as new work that describes the kinetic energy of particle velocity and of particle relative velocity. Turbulent biases are then reviewed including non-linear drag bias, preferential bias, clustering bias, diffusiophoresis and turbophoresis. Next, recent progress in turbulence modulation and particle collision frequency are discussed. Finally, a generalized flow regimes is presented to summarize the interactions as a function of particle size and particle concentration.

Concentrating solar technologies are promising renewable energy systems for exploiting incident beam solar irradiation with high exergy efficiency values. These systems provide the possibility for producing useful heat at high temperatures that can be utilized by highly efficient power cycles or producing directly solar fuels with receiver reactor technology. In the last years, the concept of beam-down concentrating solar technology gains more and more attention due to a series of advantages associated with this idea. This concept is based on the use of two-stage reflectors for concentrating solar irradiation close to the ground, something that leads to a more compact system with reduced height. Furthermore, the high-temperature heat production and the chemical processes take place on the ground and not at a great height, increasing the safety levels of the system. Moreover, this design leads to compact configurations with lower materials use, lower wind loads and without the need to move the receiver for tracking the sun.

The objective of this review is to present the recent progress on beam-down solar concentrating technology and to highlight the need for giving attention to this direction. Critical advantages of this technology are demonstrated and the associated limitations are discussed. The emphasis is on the presentation of the different technologies that can be coupled with the beam-down technology. Thermodynamic power cycles (Brayton, Rankine and Stirling), photovoltaics, thermochemical processes, as well as other applications are included and discussed. Practically, power production and solar fuels are the major useful outputs that can be generated by beam-down solar concentrating configurations. The reviewed technologies are critically discussed and compared in terms of energy, economic and environmental aspects. Future steps in the field are suggested based on the existing literature.

With the rapid development of the global electronics industry, waste printed circuit boards (WPCBs) has become one of the world's fastest growing waste streams. Exploring an environmentally sound treatment for this abundant and multi-component waste is critical to its sustainable development. This study has been aimed to cover thermochemical conversion of WPCBs (combustion, pyrolysis, gasification and hydrothermal process), focusing on thermal behavior, reaction kinetics, pollutant evolution and corresponding controlling strategies, with the aim of promoting circular economic development and building a sustainable future for the electronics industry.

The membrane process has been considered a promising technology for effective CO₂ capture due to its outstanding features, including a small environmental footprint, reduced energy consumption, simplicity of operation, compact design, ease of scalability and maintenance, and low capital cost. Among the developed polymeric materials for membrane fabrication, polyurethane (PU) and poly(urethane-urea) (PUU) as multi-block copolymers have exhibited great potential for CO₂ capture because of their excellent mechanical properties, high thermal stability, good film formation ability, favorable permeation properties, and a large diversity of monomers (i.e., polyol, diisocyanate, and chain extender) for the synthesis of desired polymers with prescribed properties. However, PU- and PUU-based membranes' gas selectivity is relatively low and thus not attractive for practical gas separation (GS) applications. Therefore, the present review scrutinizes the main influential factors on the gas transport properties and GS performance of these membranes. In this regard, we summarize the recent progress in the PU-based membranes in view of (I) design and synthesis of new PUs, (II) blending with other polymeric matrices, (III) cross-linking PU membranes, and (IV) fabricating PU-based mixed-matrix membranes (MMMs) with deep insight into an increase in CO₂ permeability, as well as CO₂/other gases selectivity. Finally, the challenges and future direction of PU-based membranes will be presented.

Molecular dynamics (MD) has evolved into a ubiquitous, versatile and powerful computational method for fundamental research in science branches such as biology, chemistry, biomedicine and physics over the past 60 years. Powered by rapidly advanced supercomputing technologies in recent decades, MD has entered the engineering domain as a first-principle predictive method for material properties, physicochemical processes, and even as a design tool. Such developments have far-reaching consequences, and are covered for the first time in the present paper, with a focus on MD for combustion and energy systems encompassing topics like gas/liquid/solid fuel oxidation, pyrolysis, catalytic combustion, heterogeneous combustion, electrochemistry, nanoparticle synthesis, heat transfer, phase change, and fluid mechanics. First, the theoretical framework of the MD methodology is described systemically, covering both classical and reactive MD. The emphasis is on the development of the reactive force field (ReaxFF) MD, which enables chemical reactions to be simulated within the MD framework, utilizing quantum chemistry calculations and/or experimental data for the force field training. Second, details of the numerical methods, boundary conditions, post-processing and computational costs of MD simulations are provided. This is followed by a critical review of selected applications of classical and reactive MD methods in combustion and energy systems. It is demonstrated that the ReaxFF MD has been successfully deployed to gain fundamental insights into pyrolysis and/or oxidation of gas/liquid/solid fuels, revealing detailed energy changes and chemical pathways. Moreover, the complex physico-chemical dynamic processes in catalytic reactions, soot formation, and flame synthesis of nanoparticles are made plainly visible from an atomistic perspective. Flow, heat transfer and phase change phenomena are also scrutinized by MD simulations. Unprecedented details of nanoscale processes such as droplet collision, fuel droplet evaporation, and CO₂ capture and storage under subcritical and supercritical conditions are examined at the atomic level. Finally, the outlook for atomistic simulations of combustion and energy systems is discussed in the context of emerging computing platforms, machine learning and multiscale modelling.

MXene (two-dimensional transition metal carbide, nitrides, and/or carbonitrides) has shown considerable interest in a variety of research fields due to its excellent conductivity, hydrophilicity, and abundant surface functional groups. However, MXene's challenges in aggregation and low stability, severely limit its applicability. MXenes can be prepared by a variety of techniques, including exfoliation of MAX phases assisted by HF and non-HF materials, and bottom-up approaches utilizing vapor deposition and templating methods. The preparation of MXene-based heterostructures composite has been recently investigated as a potential nanomaterial in energy storage. Herein, we provided an overview of MXene synthesis and current developments in the MXene-based heterostructure composites for electrochemical energy storage devices. Moreover, the challenges and difficulties for MXene-based heterostructure composites in the future MXene-based structural design have been described.