Chemical Kinetics - Science topic

Testing detailed combustion mechanisms typically concludes that some mechanisms reproduce the experimental data well at most conditions but are inaccurate at other conditions. However, other mechanisms may perform well under these conditions. A better mechanism ("mosaic mechanism") may be obtained by identifying the overall best-performing mechanis...

Predictive numerical simulations of energy conversion systems involving reacting flows are accompanied by high computational cost of solving a system of stiff ordinary differential equations (ODEs) associated with detailed fuel chemistry. This bottleneck becomes more prohibitive for complex hydrocarbon fuels with an increase in the number of reacti...

We review an iconic class of chemical oscillators driven by phase transition instabilities, namely Gas Evolution Oscillators (GEOs). These systems show oscillatory dynamics in the delivery of gas sustained simple reactions yielding gaseous products in a liquid mixture, due to nucleation and supersaturation phenomena. After presenting the main featu...

Programming matter one molecule at a time is a long-standing goal in nanoscience. The atomic resolution of a scanning tunnelling microscope (STM) can give control over the probability of inducing single-outcome single-molecule reactions. Here we show it is possible to measure and influence the outcome of a single-molecule reaction with multiple com...

Small gas‐phase metal clusters serve as model systems for complex catalytic reactions, enabling the exploration of the impacts of the size, doping, charge state and other factors under clean conditions. Although the mechanisms of reactions involving metal clusters are known in many cases, they are not always sufficient to interpret the experimental...

For spark ignition and compression ignition ammonia engines, a typical approach to ensure stable operation involves the blending of ammonia with hydrogen and diesel, respectively. For the ammonia/hydrogen fuel, in this study a comprehensive comparison was conducted firstly for the differences among existing chemical mechanisms according to the expe...

Carbon nanoparticle interactions with gases are central to many environmental and technical processes, but the underlying reaction kinetics and mechanisms are not well understood. Here, we investigate the oxidation and gasification of carbon nanoparticles by NO2 and O2 under combustion exhaust conditions. We build on a comprehensive experimental da...

The experiment investigated the effect of varying concentrations of hydrochloric acid on the rate of reaction with magnesium. Using six different concentrations of hydrochloric acid (2 mol dm⁻³ to 0.5 mol dm⁻³) and one control with distilled water, magnesium cubes of uniform size and mass were reacted with 15 cm³ of each solution in separate conica...

Thermal explosions in reactive flows present an important risk to industrial engineering systems, where uncontrolled exothermic reactions can compromise safety and operational integrity. This study investigates the theoretical solutions related to thermal runaway and heat transport in a branch-chain bifurcation scenario influenced by hydromagnetic...

In this paper, the aerodynamic performances including shock wave standoff distance (SSD) and heat flux of ELECTRE vehicle at 53.3 km and 4230 m/s for several types of numerical models are investigated. The numerical models include thermal equilibrium/nonequilibrium (1T/2T) assumption, three surface boundary conditions (no-slip/non-catalytic, slip/n...

The formal description of chemical reactions far from equilibrium is an open task. Chemical reactions are central to various phenomena in life, industry, and the environment. In this work, we use a variational principle within the framework of extended irreversible thermodynamics to obtain relaxation equations for the fast variables and close the b...

The book discusses in a simple and lucid language the principles of Chemical Kinetics,an important branch of Chemistry with applications in many fields. The chapters deal with 1) Rate and Order of reaction, 2)Theories of reaction rates, 3) Integrated rate equations,4)Kinetics of reactions in solution,5)Kinetics of complex reactions including surfac...

The dependence on fossil fuels and the overexploitation of it is a bottlenecked problem of the globe leading to finding alternative renewable resources that may be used as an energy source in place of fossil fuels. Thermogravimetric analysis (TGA) is a technique used to identify potential renewable energy sources. This study investigated the kineti...

Although thermal waves are ubiquitous in nature and engineering, the development of diagnostic tools capable of elucidating the roles of reaction and transport remains an unmet need. This limits our comprehension of the physics and ability to predict wave dynamics. Here we demonstrate that thermal properties and chemical kinetics can be learned dir...

Chemical kinetics can be a useful tool for determining the optimal operating time of electrochemical processes. The main objective of the study was to determine the mineral oil removal rate by sono-electrochemical treatment. In this study, zero-, first-, and second-order kinetic models were used to determine the reaction rate of mineral oil removal...

Objective: We present a physics-based, temperature and state-dependent electrical conductivity model for soft biological tissue under thermal therapies with a quantified damage parameter that represents the state of soft biological tissue (degree of denaturation). Most existing models consider electrical conductivity to be only temperature-dependen...

This article presents simulations of a turbulent lifted flame using the large eddy simulation-transport probability density function-discretized population balance equation approach. This approach takes into account the interaction between turbulent reacting flow and soot particle formation. A reduced chemical kinetics mechanism including a series...

Chemical reactions underpin biological processes, and imbalances in critical biochemical pathways within organisms can lead to the onset of severe diseases. Within this context, the emerging field of “Nanocatalytic Medicine” leverages nanomaterials as catalysts to modulate fundamental chemical reactions specific to the microenvironments of diseases...

Affected by environmental states and power supply parameters, the discharge mode of surface dielectric barrier discharge (SDBD) plasma may gradually transfer from O3 mode to NOx mode, resulting in various gas-phase species for different applications. Despite the intensive study of attempts to control this discharge mode transition by changing disch...

We present KinetiX, a software toolkit to generate computationally efficient fuel-specific routines for the chemical source term, thermodynamic and mixture-averaged transport properties for use in combustion simulation codes. The C++ routines are designed for high-performance execution on both CPU and GPU architectures. On CPUs, chemical kinetics c...

This study examines the necessity for standardized assessment instruments in STEM chemistry for senior high school students, with a focus on four important areas of physical chemistry: thermochemistry, chemical kinetics, chemical thermodynamics, and electrochemistry. Developing such assessment tools is essential to ensure fair assessments, identify...

Relevance. The widespread distribution and availability of biomass in the regions of Russian Federation make it possible to consider it as a renewable energy source with a lower negative impact on the environment compared to fossil fuels, since biomass is recognized as a carbon-neutral fuel. The use of biomass as a fuel in the form of pellets is in...

Asymmetric chemical reactions on the surfaces of colloidal particles are known to propel them into directional motion. The dynamics of such chemical micromotors are sensitive to their local chemical environments, which also continually evolve with the reactions on motor surfaces. This two‐way coupling between the motor dynamics and the local enviro...

The utilization of hydrogen-enriched liquefied petroleum gas (LPG) is an effective means of reducing carbon emissions, but the special physical and chemical properties of hydrogen have raised concerns among the public. To delve into the intricate chemical kinetic mechanisms governing the inhibitory effect of CO2 on the explosion of hydrogen-enriche...

The Thomas equation, which controls ion exchange as well as chemical kinetics and advection processes in chemical systems, has its coefficients expanded as functions of time in this work. The goal of this modification is to produce simulations of advection and kinetic processes that are more precise and lifelike. In order to examine the nonlinear d...

Unimolecular gas phase chemical reactions could be activated by both infrared (IR) radiation and inter-molecular collision in the interstellar environment. Understanding the interplay and competition between the radiation and collision activation mechanisms is crucial for assessing accurate reaction rate constants with an appropriate model. In this...

In this article, ve violations of the Principle of Relativity are presented, all of which are immediately deduced from the Lorentz Transformation. Each of these violations implies that certain physical laws, which should hold in all inertial reference frames, do not hold in all inertial reference frames. The areas involved include hydrostatics, str...

Mineral scales formed during water injection impose a significant threat to economic and efficient field operation. Most previous studies are one dimensional, thermodynamic modeling without the consideration of reaction kinetics. In this paper, two-dimensional reactive transport modeling (RTM) with chemical reaction kinetics is performed to investi...

Although methods to derive the rate equation from a kinetic model have been known for over a century, it remains mathematically challenging to derive the rate equation for complex reactions involving multiple steps, as the derivation requires a solution for simultaneous differential equations. Furthermore, the derived kinetic equations are often di...

pH regulation of eukaryotic cells is of crucial importance and influences different mechanisms including chemical kinetics, buffer effects, metabolic activity, membrane transport and cell shape parameters. In this study, we develop a microfluidic system to rapidly and precisely control a continuous flow of ionic chemical species to acutely challeng...

Vertical mixing is a crucial disequilibrium process in exoplanet atmospheres, significantly impacting chemical abundance and observed spectra. While current state-of-the-art observations have detected its signatures, the effect of vertical mixing on atmospheric spectra varies widely based on planetary parameters. In this study, we explore the influ...

This study addresses a longstanding question regarding the mathematical proof of chaotic behavior in kinetic differential equations. Following the numerous numerical and experimental results in the past 50 years, we introduce two formal chemical reactions that rigorously demonstrate this behavior. Our approach involves transforming chaotic equation...

Today, bio-sourced materials represent an important technological field of study, as they could sink atmospheric carbon dioxide into buildings. Little-processed construction materials would also reduce the environmental impact of the construction sector, which emitted more than 2.9 Mt of CO2 in 2020. Hemp-lime is a material that meets both these re...

Plain Language Summary When rock dissolves, it creates different patterns depending on the interplay of flow, reactant transport, and chemical kinetics. These patterns are classified into various types, known as dissolution regimes. However, this classification is often based solely on visual examination of the final structures and lacks quantitati...

Nowadays, emissions from internal combustion engines are a relevant topic of investigation, taking into account the continuous reduction of emission limits imposed by environmental regulatory agencies around the world, obviously as the result of earnest studies that have pointed out the impact on the human health of high levels of contaminants rele...

We study the transient dynamics of three-dimensional detonation cells when the detonation front is subjected to weak expansion due to the diffraction from a straight channel to a diverging channel. We focus on the effect of the cross-sectional shape, namely square or round, using diverging channels with the same initial cross-sectional area of 16 c...

An actuality of modernizing advancement the modern adopted combustion theory is due to a significant change in the composition of fuels at the market of developed countries by rejection of basic mineral (organic) fuels (fossil fuels), which have been used in the world for 250 years. The transformation of traditional fuels’ orientation towards an ap...

Stricter aviation emissions regulations have led to the desire for lean-premixed-vaporized combustors over rich-quench-lean burners. While this operation mode is beneficial for reducing NOx and particulate emissions, the interaction of the flame and hot exhaust gases with the cooling flow results in increased CO emissions. Predicting CO in computat...

Although many models have been developed for solute partition coefficient (or solvation Gibbs free energy, ΔGsolv), how to develop models for rapid and accurate solvation energy predictions still remains challenging. In this work, a relation named the A-P scheme based on the Q–e scheme in radical copolymerizations and the Arrhenius equation for che...

This article describes the production of biogas in a cellulose-based substrate using a multifractional dynamic model. The objective is to give more precise depiction of the nonlinear characteristics of the chemical reactions involved in anaerobic digestion. In addition well-posedness and consistency, we present the sensitivity analysis used to dete...

This study explores in depth rotating detonation engines (RDEs) fueled by premixed stoichiometric hydrogen/air mixtures through two-dimensional numerical simulations including a detailed chemical kinetic mechanism. To model the spatial reactant non-uniformities observed in practical RDE combustors, the referred simulations incorporate different num...

Experimental studies and numerical analyses were conducted to estimate the laminar flame speeds of butyl ether, n-octane, iso-octane, and 1-octene at temperatures of 373 and 443 K and pressures ranging from 0.03 to 0.3 MPa in a constant-volume combustion chamber. Iso-octane had the slowest laminar flame speed whereas butyl ether had the highest. Th...

This work employs partial and non-OH models to mimic 2D steady-state spray combustion. The study examines the status of the partial OH model following the NOx forecast, comparing it to the non-model. It assumes that the O model is in equilibrium with the predicted NOx. The study assesses the numerical models by using data from Mao et al. (35). This...

Combustion involves the study of multiphysics phenomena that includes fluid and chemical kinetics, chemical reactions and complex nonlinear processes across various time and space scales. Accurate simulation of combustion is essential for designing energy conversion systems. Nonetheless, due to its multiscale, multiphysics nature, simulating these...

Ammonia is carbon-free and is a very promising renewable fuel. The ammonia/diesel dual-fuel combustion strategy is an important combustion strategy for ammonia internal combustion engines. To achieve clean and efficient combustion with a high ammonia blending ratio in ammonia engines, it is important to thoroughly investigate the combustion charact...

Civil aviation has been going through continuous development since the invention of jet engines. With the continuously increasing demands, there are still challenges to be faced in order to meet the emission goals. Even with operational improvements, novel combustion technologies with hydrogen and drop-in fuels and increased component efficiencies,...

Recorded presentation is available at: https://combustiondata.elte.hu/presentations/AndrasSzanthoffer_SoAE2024_presentation_v20240915_recorded.mp4 *** Testing detailed combustion mechanisms typically concludes that some mechanisms reproduce the experimental data well at most conditions but are inaccurate at other conditions. However, other mechani...

Although various hypergolic propellants like MMH/N2O4 (monomethylhydrazine/dinitrogen tetroxide) are widely used in small rocket engines, there remains a lack of in-depth study conducted on their chemical reactions and spray combustion behaviors. To fill this research gap, a simplified chemical kinetic model that is suitable for three-dimensional s...

Controlling fluxes of vacuum ultraviolet (VUV) radiation is important in a number of industrial and biomedical applications of low pressure plasma sources because, depending on the process, VUV radiation may be desired, required to a certain degree, or unwanted. In this work, the emission of VUV radiation from O atoms is investigated in low-pressur...

The objective of this work was to evaluate the physicochemical and adsorptive characterization of Fe tailing collected in the district of Brumadinho; and verify its effect on Raphanus sativus germination. The material was collected on the surface layer (0-20 cm) and disintegrated for pH, redox potential – Eh, electrical conductivity – EC, OM, catio...

In order to reveal the deflagration mechanism of DME/H2-blended gasses, the micro-mechanism was studied based on the constructed UC San Diego 2016 pyrolysis oxidation mechanism model. The results show that adiabatic flame temperature and laminar flame speed increase with the increase in the equivalence ratio (Φ); they first increase and then decrea...

In the global push for sustainable energy, in-situ combustion gasification (ISCG) has emerged as a transformative technology to leverage the world's abundant heavy oil reserves for producing carbon-zero hydrogen. Chemical kinetics are crucial for modeling subsurface hydrogen generation and optimizing production schemes to maximize hydrogen yield, w...

Azo dyes are carcinogenic and if taken would lead to debilitating adverse health effects in animals, man and aquatic organisms. In this study, novel Boron Doped Diamond (BDD) electrodes coated with silver nanoparticles were applied. Iron (11) sulphate was used as a supporting electrolyte and silver nanoparticles as electrocatalyst to enhance the de...

This paper aims to identify research areas that address the issues of fuel consumption and pollutant emissions in transportation and other internal combustion engines (IC engine). The author's view, will help Three types of IC engines are discussed and compared: Spark-Ignited (SI), Conventional Diesel, and Low Temperature Combustion (LTC), with the...

Plasma-neutral interactions, including reactive kinetics, are often either studied in 0D using ODE-based descriptions, or in multi-dimensional fluid or particle-based plasma codes. The latter case involves a complex assembly of procedures that are not always necessary to test effects of underlying physical models and mechanisms for particle-based d...

The rate constant matrix contraction (RCMC) method, proposed by Sumiya et al. (2015, 2017), enables fast and numerically stable simulations of chemical kinetics on large-scale reaction path networks. Later, Iwata et al. (2023) mathematically reformulated the RCMC method as a numerical algorithm to solve master equations whose coefficient matrices,...

The simulation of reactive flows is a very challenging task from the computational point of view, as in addition to taking into account all the complex aspects of fluid dynamics, it requires a detailed description of the chemical kinetics involved in the process. Thus, the use of strategies to reduce simulation time is essential. Among the existing...

The intramolecular H-migration reaction of RIORIIOO· radicals constitute a key class of reactions in the low-temperature combustion mechanism of ethers. Despite this, there is a dearth of direct computations regarding the potential energy surface and rate constants specific to ethers, especially when considering large molecular systems and intricat...

The development of computational models for the numerical simulation of chemically reacting flows operating in the turbulent regime requires the solution of partial differential equations that represent the balance of mass, linear momentum, chemical species, and energy. The chemical reactions of the model may involve detailed reaction mechanisms fo...

Perovskites can absorb solar energy and are extensively used in various catalytic and photocatalytic reactions. However, noble metal particles may enhance the catalytic, photocatalytic, and antibacterial activities. This study demonstrates the cost-effective green synthesis of the photocatalyst perovskite LaMnO3 and its modification with noble meta...

We introduce Finenzyme, a Protein Language Model (PLM) that employs a multifaceted learning strategy based on transfer learning from a decoder-based Transformer, conditional learning using specific functional keywords, and fine-tuning to model specific Enzyme Commission (EC) categories. Using Finenzyme, we investigate the conditions under which fin...

The hypersonic regime is defined by Mach numbers larger than 5. The challenges are different from supersonic flight and include significant surface heating, complex transition physics, and air high-temperature effects. Research in hypersonics requires investment-heavy experimental facilities and instrumentation. This motivates numerical simulations...

To study the impact of faults on the enrichment and mobility of shale oil in the Gulong area, representative rock samples were selected in this paper. Based on geochemical data and chemical kinetics methods, coupled with shale oil enrichment and mobility analysis techniques, the shale oil generation quantity and in situ oil content were evaluated f...

This paper reports the investigation of the effect of chemical kinetic mechanisms on the thermoacoustic behaviour of a premixed combustor test rig. This was done by exploring the flame transfer function (FTF) of three chemical kinetic mechanisms; a global (6 species, 2 reaction) mechanism, a reduced (19 species, 55 reaction) mechanism and a detaile...

Lithium-ion cells exhibit superior energy and power density, longer cycle life, and lower cost compared to other types of batteries. Research is required to streamline the utilisation of lithium-ion cell stacked battery packs with battery management systems (BMS). The Battery Management System (BMS) detects temperature, current, and voltage, and of...

This chapter delves into the intricate realm of environmental chemistry, with a particular emphasis on the difficulties that are brought about by pollutants in the systems of air, water, and soil. The purpose of this research is to investigate the chemical kinetics of commonly found pollutants and to evaluate novel approaches to remediation. Improv...