Combustion and Flame最新文献

{"title":"Regression rates and combustion characteristics of dicyclopentadiene based solid fuels with ball milled boron-PTFE additives","authors":"Dhruval N. Patel ,&nbsp;Kyle E. Uhlenhake ,&nbsp;Justin Kruse ,&nbsp;Metin Örnek ,&nbsp;Steven F. Son","doi":"10.1016/j.combustflame.2025.114035","DOIUrl":"10.1016/j.combustflame.2025.114035","url":null,"abstract":"<div><div>Theoretically, boron is attractive as a fuel for air breathing applications; however, its ignition and combustion properties are inadequate for realizing its full potential. In this study, we investigated the effect of polytetrafluoroethylene (PTFE) addition on the combustion and reactivity of boron. We compared the effects of physical mixing and high energy ball milling boron-PTFE mixtures as a function of PTFE loading (0–30 wt.% PTFE). Lower exothermic peak temperatures and minimum ignition energies (MIE) were observed for ball milled boron-PTFE mixtures compared to physically mixed boron-PTFE mixtures, indicating higher reactivity. Conversely, ball milling boron without PTFE was shown to have a negligible or negative impact on exothermic peak temperatures and minimum ignition energy. To elucidate the effects of ball milling on boron-PTFE combustion in a fuel system, physical and ball milled mixtures of boron and boron-PTFE mixtures were added into dicyclopentadiene (DCPD). Fuel mixtures of 70 wt.% DCPD and 30 wt.% boron or boron-PTFE mixtures (PM-mixtures and BM-mixtures) were tested in a closed bomb calorimeter to determine heats of combustion and combustion efficiency and an opposed flow burner to determine regression rates and flame temperatures at varying oxidizer flow rates. Heats of combustion, combustion efficiencies and regression rates of DCPD based fuel mixtures are improved with ball milled additives compared to neat boron additives. Furthermore, increasing PTFE content in ball milled boron-PTFE additives enhanced the heats of combustion, combustion efficiencies and regression rates of DCPD based fuel mixtures. The enhanced combustion characteristics of ball milled boron-PTFE mixtures can be attributed to the reduced diffusion distances between intertwined boron and PTFE. These shorter diffusion distances elevate temperatures and increase the rate of boron oxide gasification. This improvement may render boron a more feasible fuel, especially in air-breathing applications.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114035"},"PeriodicalIF":5.8,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"EM-HyChem: Bridging molecular simulations and chemical reaction neural network-enabled approach to modelling energetic material chemistry","authors":"Xinzhe Chen ,&nbsp;Yabei Xu ,&nbsp;Mingjie Wen ,&nbsp;Yongjin Wang ,&nbsp;Kehui Pang ,&nbsp;Shengkai Wang ,&nbsp;Qingzhao Chu ,&nbsp;Dongping Chen","doi":"10.1016/j.combustflame.2025.114065","DOIUrl":"10.1016/j.combustflame.2025.114065","url":null,"abstract":"<div><div>This study introduced a physics-inspired, top-down approach for modelling the reaction kinetics of energetic materials, based on observations of the time scale separation between pyrolysis and oxidation reactions. This modelling approach, named EM-HyChem, was developed with the inspiration of the original hybrid chemistry (HyChem) model, in which the reaction mechanism is divided into two submodels: pyrolysis and oxidation. In EM-HyChem, the key pyrolysis products and reaction mechanism are identified from the perspective of molecular fragments via geometry analysis, which is validated via neural network potential-enabled molecular dynamic simulations. A chemical reaction neural network (CRNN) model is applied to extract the rate parameters for the pyrolysis step from the reproduction of thermogravimetric experiments. An EM-HyChem model is later constructed by combining the pyrolysis step together with the oxidation models for the pyrolysis products. Two representative EMs, i.e., 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), are considered here to evaluate the performance of the EM-HyChem model. The predicted burning rates across a wide range of pressure conditions (1–100 atm) are in good agreement with the experimental measurements and the results of other models. Further agreement among the temperature profile, melt layer thickness and surface temperatures support the EM-HyChem model.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114065"},"PeriodicalIF":5.8,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143453672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Visualization and modelling study of reaction and heat transfer during gasification of single coal/char particle on slag wall","authors":"Jingyun Bai ,&nbsp;Xudong Song ,&nbsp;Dongbin Mai ,&nbsp;Juntao Wei ,&nbsp;Yonghui Bai ,&nbsp;Jiaofei Wang ,&nbsp;Jie Xu ,&nbsp;Guangsuo Yu","doi":"10.1016/j.combustflame.2025.114063","DOIUrl":"10.1016/j.combustflame.2025.114063","url":null,"abstract":"<div><div>The part of particles inside gasifier is captured by the slag wall and then reacts on the wall. However, the reaction of coal particles on the slag wall surface is very complex and the corresponding mechanism has not been revealed systematically. The CH* distribution can be used to characterise the area of reaction of the coal particles for the devolatilization, and the time of devolatilization of the coal particles in the furnace can be assessed. In this study, the CH* releasing and temperature two-dimensional distribution of single coal/char particle on slag and non-slag walls during gasification were visualized using a high-speed camera with bandpass filters. Moreover, the particle temperatures were calculated by shrinking core model to explore the effect of the slag wall surface on the heat transfer of the particles and the reaction process. The results show that the particles are subjected to heat conducted by slag, accelerating heating, enhancing CH* release, and shortening gasification time. The calculated particle temperatures closely matched experimental values, indicating precise temperature predictions. Based on the variation of CH* peak intensity versus time, coal particle gasification was divided into preheating, volatile components releasing, and coal char reaction stages. For volatile components releasing stage, CH* peak intensity was mainly depended on particle temperature, which can be estimated from CH* intensity. For the coal char reaction stage, the change of particle temperature versus carbon conversion is consistent with the exponential function model.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114063"},"PeriodicalIF":5.8,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143445825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rush-to-equilibrium concept for minimizing reactive nitrogen emissions in ammonia combustion","authors":"Hernando Maldonado Colmán,&nbsp;Michael E. Mueller","doi":"10.1016/j.combustflame.2025.114049","DOIUrl":"10.1016/j.combustflame.2025.114049","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Ammonia is a zero-carbon fuel that has been receiving increasing attention for power generation and even transportation. Compared to hydrogen, ammonia’s volumetric energy density is higher, is not as explosive, and has well established transport and storage technologies. However, ammonia has poor flammability and flame stability characteristics and more reactive nitrogen emissions (nitrogen oxides, nitrous oxide) than hydrocarbon fuels, at least with traditional combustion processes. Partially cracking ammonia addresses its flammability and stability issues, through on-board catalysts or autothermal crackers, into a mixture of ammonia, hydrogen, and nitrogen. However, reactive nitrogen emissions remain a challenge, and mechanisms of their emissions are fundamentally different in ammonia and hydrocarbon combustion. While rich-quench-lean ammonia combustion strategies have shown promise, the largest contributions to reactive nitrogen emissions are the unrelaxed emissions in the fuel-rich first stage due to overshoot of thermodynamic equilibrium within the reaction zone of premixed flames coupled with finite residence times available for relaxation to equilibrium. This work introduces a rush-to-equilibrium concept for partially cracked ammonia combustion, which aims to reduce the unrelaxed reactive nitrogen emissions in finite residence times by accelerating the approach to equilibrium. In the concept, a flow particle is subjected to a decaying mixing rate as it transits the premixed flame. This plays an important role in mitigating the mixing effects that prevents the flow particle approach to equilibrium, and promoting the chemistry effects to push the particle toward equilibrium, all while considering residence times typical of gas turbines for power generation. Evaluated with a state-of-the-art combustion model at gas turbine conditions, the concept shows the potential for a reduction in reactive nitrogen emissions by an order of magnitude at even modest mixing rate decay rates. It is also shown that the concept works irrespective of cracking extent, pressure, temperature, etc. A brief discussion of practical feasibility reveals reasonable geometric and flow parameters characteristic of modern gas turbine combustors for power generation.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and Significance Statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;A novel rush-to-equilibrium combustion concept is proposed with the aim of reducing reactive nitrogen emissions, which include nitrogen oxides and nitrous oxide, from partially cracked ammonia combustion at gas turbine conditions. Reactive nitrogen emissions are elevated in partially cracked ammonia combustion systems because insufficient residence time is available to reach thermodynamic equilibrium. A concept is proposed to address this issue, leveraging decaying mixing rates, without modifying typical gas turbine for power generation residence times by accelerating the approach to thermodynamic equilibrium. The new concept is de","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114049"},"PeriodicalIF":5.8,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetic roles of energy transformation during ignition enhancement of NH3/air mixture by non-equilibrium plasma discharge via nanosecond repetitive pulsed discharge","authors":"Zhencao Zheng,&nbsp;Yong Hu,&nbsp;Ruijiao Cao,&nbsp;Weixin Rong,&nbsp;Feiyang Zhao,&nbsp;Wenbin Yu","doi":"10.1016/j.combustflame.2025.114061","DOIUrl":"10.1016/j.combustflame.2025.114061","url":null,"abstract":"<div><div>In this work, a numerical study and multi-scale process analysis of plasma assisted ammonia ignition with nanosecond repetitive pulse discharge at room temperature and pressure are carried out under varied applied voltages. Analysis of theoretical plasma thermal-chemical instability and Gibbs free energy confidence to ignition spontaneity through plasma intervention are performed. In addition, the present study extends the ability of modelling deposition energy transformation accounted for plasma kinetics interact with vibrational-translational relaxation, electron attachment/detachment. To identify the significant reaction paths on plasma systems reactivity, a plasma-based global pathway analysis (PGPA) was derived from element-flux transfer including repeated nodes within cyclic reaction step (de-excitation to ground state). It is concluded that although a large amount of plasma generated in the pulse discharge causes a rapid but short-lived temperature rise in the system, heat release from chemical reactions during the pulse interval is the primary cause of combustion system heating. Kinetics analysis discloses that oxygen decomposition (O₂=&gt;O) and ammonia dehydrogenation (NH₃=&gt;NH₂) are two key processes stimulating ignition. Furthermore, O₂ is decomposed into O and O(1D) through collisions with electrons and excited state N₂ (N₂(B) and N₂(C)) in the pulse discharge, and O(1D) subsequently relaxes and quenches into O. Ammonia dehydrogenation occurs at the same time as a result of collision dissociation. Provisions on activated radicals and energy transfer at low temperature are made due to plasma participant, thus facilitating to trigger subsequent NH₃ oxidation chain reactions. The present study provides insights and guidance to discover the underlying plasma kinetic roles when performing ignition enhancement of NH₃/air mixture.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114061"},"PeriodicalIF":5.8,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143445826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanism of liquid oxygen temperature on combustion stability of gas-liquid swirl coaxial injectors","authors":"Pengjin Cao,&nbsp;Peng Cheng,&nbsp;Xiao Bai,&nbsp;Qinglian Li,&nbsp;Ziguang Li,&nbsp;Jingjing Liao","doi":"10.1016/j.combustflame.2025.114050","DOIUrl":"10.1016/j.combustflame.2025.114050","url":null,"abstract":"<div><div>Deep-throttling variable thrust cryogenic propellants rocket engines are facing the challenge of unstable combustion caused by propellants temperature. To explore the effect of liquid oxygen temperature on the combustion stability of liquid oxygen/methane engine, spray images and CH* chemiluminescence images were obtained synchronously using laser background light imaging. The dynamic characteristics of spray and flame at different liquid oxygen temperatures were studied. The mechanisms of low- and medium-frequency unstable combustion were analyzed. The liquid oxygen temperature has a significant influence on the combustion stability of the gas liquid swirl coaxial injectors. As the liquid oxygen temperature decreases, the frequencies of low- and medium-frequency oscillation combustion modes decrease, and the oscillation intensity increases. Eventually, both the low- and medium- frequency unstable combustion disappear. At the same total mass flow rate, the spray projection area of liquid oxygen decreases with increasing liquid oxygen temperature, while both the flame projection area and flame length increase. The low-frequency oscillation combustion mode results from the interaction between the fluctuating mass flow of liquid oxygen injected into the combustor and the vaporization of liquid oxygen inside the injector. When the liquid oxygen boiling position is near the surface of the gas core, partial vaporization of liquid oxygen inside the injector occurs, leading to the appearance of the medium-frequency oscillation combustion mode in the combustor. However, when the liquid oxygen boiling position exceeds the liquid sheet thickness of the swirl chamber, the liquid oxygen inside the injector remains in a purely liquid phase, resulting in stable combustion. Both low- and medium-frequency combustion instabilities can be effectively suppressed by increasing the combustor pressure or decreasing the liquid oxygen temperature.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114050"},"PeriodicalIF":5.8,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracking of acoustic and intrinsic modes for thermoacoustic systems with a general flame model","authors":"Alessandro Orchini ,&nbsp;Frida Cronqvist ,&nbsp;Jakob G.R. von Saldern ,&nbsp;Sylvain C. Humbert ,&nbsp;Jonas Moeck","doi":"10.1016/j.combustflame.2025.113998","DOIUrl":"10.1016/j.combustflame.2025.113998","url":null,"abstract":"<div><div>In a thermoacoustic feedback loop, the flame gain parameter can be used to measure the coupling strength between the acoustic field and the flame response. In this study, it is shown for an arbitrary flame model that the thermoacoustic solutions in the zero-coupling limit split into two distinct sets: modes of (i) acoustic and (ii) intrinsic (ITA) origin. This result was previously shown in a rigorous manner only for <span><math><mi>n</mi></math></span>–<span><math><mi>τ</mi></math></span> flame models, which are special in the sense that they have ITA poles only at infinity. Consequently, all thermoacoustic eigenvalues can generally be calculated from the acoustic and intrinsic poles using continuation methods. In this study, we provide an explicit eigenvalue tracking scheme based on the integration of the local eigenvalue sensitivity to the flame gain parameter. The initial conditions required for integration are considered in detail. While the acoustic poles can be determined directly via Helmholtz solvers, the intrinsic poles are less trivial since they depend on the flame model. An asymptotic expansion of a generic transfer function is derived that is representative of all common flame models. It provides the necessary estimates for the intrinsic poles as the flame gain approaches zero in terms of the Lambert <span><math><mi>W</mi></math></span> function. This approach represents an explicit scheme that guarantees to find all thermoacoustic eigenvalues. The methodology is demonstrated using a simple Rijke tube network model and an experimentally determined state-space model of an annular setup.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 113998"},"PeriodicalIF":5.8,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Energy output characteristics of an enhanced aluminized explosive: Impact of Al-Li alloy fuel","authors":"Jie Yao ,&nbsp;Kanghua Chang ,&nbsp;Fengyou Yang ,&nbsp;Xueyong Guo ,&nbsp;Xiaolu Bi ,&nbsp;Jianxin Nie ,&nbsp;Shi Yan ,&nbsp;Qingjie Jiao","doi":"10.1016/j.combustflame.2025.114064","DOIUrl":"10.1016/j.combustflame.2025.114064","url":null,"abstract":"<div><div>Applying new alloy fuels is critical for improving the energy release characteristics of aluminized explosives. Al-Li alloy fuel has become a promising fuel for metallized explosives due to its low ignition temperature, short ignition delay, and fast combustion rate. In this study, three different Al-Li alloy fuels (Li content 2 %, 5 %, and 10 %) were selected to replace pure Al particles, and their effect on oxidation, ignition, and combustion characteristics were examined. Thermogravimetric-differential scanning calorimetry revealed that using Al-Li alloy can cause early oxidation and increase the oxidation rate and weight gain, which is positively correlated with the Li content. Furthermore, the oxygen bomb calorimeter, closed bomb, and laser ignition measurements revealed that adding Li can promote the ignition and combustion of Al and increase its combustion calorific value. Among them, AlLi₁₀ demonstrated the most balanced combination of high combustion calorific value, high combustion intensity, and short ignition delay. Additionally, aging experiments demonstrated that alloy fuels with more Li content are more easily oxidized, which makes it easy to react with HTPB and affects the safety of explosives. The designed HMX/AlLi₂/HTPB explosive samples demonstrated improved detonation heat, detonation velocity, detonation field temperature, and near-field shock wave overpressure of the explosive when using Al-Li alloy fuel due to the ignition and combustion characteristics of Al-Li alloy fuel. Furthermore, the study explained the energy output structure of highly active alloy fuels in metalized explosive systems and proposed a micro-explosion refinement reaction model of Al-Li alloy fuel in the post-detonation combustion zone. The findings of this study may serve to develop AlLi₂ alloy fuel as an attractive candidate for metalized explosives to enhance energy release.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114064"},"PeriodicalIF":5.8,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improve energy release of boron by tunable metal-organic frameworks via synergetic micro-explosion and catalysis","authors":"Kang Xue ,&nbsp;Huaiyu Li ,&nbsp;Lun Pan ,&nbsp;Chongjun Li ,&nbsp;Minhua Ai ,&nbsp;Chengxiang Shi ,&nbsp;Xiangwen Zhang ,&nbsp;Ji-Jun Zou","doi":"10.1016/j.combustflame.2025.114062","DOIUrl":"10.1016/j.combustflame.2025.114062","url":null,"abstract":"<div><div>Boron is considered as one of the most promising high energy additives to improve the energy density of aerospace propellants and energetic materials. However, the low energy release properties restrict its practical applications. Herein, three kinds of boron-based composite energetic particles (nB@MOF) were prepared by encapsulating nano boron (nB) in metal-organic frameworks (MOFs) by a self-assembly method with Zn, Co and Mo as metal nodes, and 2-methylimidazole and ethylenediamine as organic ligands. The characterization and dynamics results show that the combustion of organic ligands can induce micro-explosion to destroy the surface oxidation layer of agglomeration and promote the oxidation efficiency of boron. Furthermore, the metal oxide catalyst generated <em>in-situ</em> on nB surface by metal nodes can reduce the initial oxidation temperature and improve the mass transfer distance and interface contact of the oxidation reaction. Compared with nB, the maximum pressurization rate of nB@MOF with 2-methylimidazole as the organic ligand is increased by 31.1 times, the initial oxidation temperature of nB@MOF with Mo as the metal node is reduced by 185.9°C, and the combustion heat of all nB@MOF are increased by more than 1.2 times. This work demonstrates that the energy release properties of boron can be effectively improved by synergistic effect of micro-explosion process and interfacial catalysis.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114062"},"PeriodicalIF":5.8,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distinct evaporation and combustion behaviors of suspended and unsuspended nanodiesel droplets","authors":"Álvaro Muelas,&nbsp;Taha Poonawala,&nbsp;Javier Ballester","doi":"10.1016/j.combustflame.2025.114060","DOIUrl":"10.1016/j.combustflame.2025.114060","url":null,"abstract":"<div><div>This work reports the main evaporation and combustion characteristics of diesel droplets doped with different concentrations of alumina and ceria nanoparticles (NPs) for a range of conditions scarcely explored and relevant for combustion applications: high-temperature and reducing/oxidizing atmospheres (0/10 % O₂). Due to the potential influence of the particular experimental conditions, all tests are performed using two different setups: a free-falling droplet (FFD) rig and a suspended droplet (SD) facility, following a systematic study that is considered especially pertinent for particle-laden fuels. The reported results demonstrate, for the first time, a great influence of the test method on some of the observed behaviors, which can perfectly justify some contradictions and even inconsistencies observed in previous works. Tests on unsuspended nanodiesel droplets provide smooth evaporation curves until the onset of a single and violent microexplosion that shatters the droplets, whereas the testing of suspended droplets yields a fluctuating evaporation process, with a wide range of sequential disruptive phenomena of different intensities (swelling, puffing, weak microexplosions). These clear differences point to the impact of the suspension filaments on disruptive behaviors for the range of conditions explored, even when very thin ceramic fibers are employed. In spite of these differences, some common features have also been identified. Namely, the addition of NPs does not drive significant changes in the droplet evaporation rate, probably due to the small impact of thermal radiation for the tested conditions. However, the onset of disruptive phenomena shortens the liquid conversion times as compared to neat diesel, with an earlier occurrence as the NP concentration increases, especially for FFD tests. Among the two tested nanoparticles, ceria shows significantly stronger disruptive events and also a progressive reduction in evaporation rate for unsuspended droplets, which is consistent with the formation of a less permeable shell for this kind of NP.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114060"},"PeriodicalIF":5.8,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}