Flow, Turbulence and Combustion最新文献

{"title":"Review of Modelling of Pyrolysis Processes with CFD-DEM","authors":"Don Dasun Attanayake,&nbsp;Fabian Sewerin,&nbsp;Shreyas Kulkarni,&nbsp;Andrea Dernbecher,&nbsp;Alba Dieguez-Alonso,&nbsp;Berend van Wachem","doi":"10.1007/s10494-023-00436-z","DOIUrl":"10.1007/s10494-023-00436-z","url":null,"abstract":"<div><p>In a pyrolysis reactor, organic polymers from biomass or plastic waste are thermally decomposed into volatile gases, condensable vapours (tar or bio-oil) and solid residues (char). Since these products may serve as building blocks for downstream chemical refinement or form the basis of bio-derived fuels, pyrolysis is thought to be instrumental in our progress towards a circular economy. A pyrolysis reactor constitutes a multiphase reactive system whose operation is influenced by many chemical and physical phenomena that occur at different scales. Because the interactions and potential reinforcements of these processes are difficult to isolate and elucidate experimentally, the development of a predictive modelling tool, for example, based on the CFD-DEM (discrete element method) methodology, is attracting increasing attention, particularly for pyrolysis reactors operated with biomass as feedstock. By contrast, CFD-DEM descriptions of plastic pyrolysis remain a challenge at present, mainly due to an incomplete understanding of their melting behaviour. In this article, we provide a blueprint for describing a pyrolysis process within the scope of CFD-DEM, review modelling choices made in past investigations and detail the underlying assumptions. Furthermore, the influence of operating conditions and feedstock properties on the key metrics of the process, such as feedstock conversion, product composition and residence time, as determined by past CFD-DEM analyses is surveyed and systematised. Open challenges that we identify pertain to the incorporation of particle non-sphericity and polydispersity, the melting of plastics, particle shrinkage, exothermicity on part of the gas-particle chemistry and catalytic effects.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"111 2","pages":"355 - 408"},"PeriodicalIF":2.4,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-023-00436-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4164774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessment of Numerical Accuracy and Parallel Performance of OpenFOAM and its Reacting Flow Extension EBIdnsFoam","authors":"Thorsten Zirwes,&nbsp;Marvin Sontheimer,&nbsp;Feichi Zhang,&nbsp;Abouelmagd Abdelsamie,&nbsp;Francisco E. Hernández Pérez,&nbsp;Oliver T. Stein,&nbsp;Hong G. Im,&nbsp;Andreas Kronenburg,&nbsp;Henning Bockhorn","doi":"10.1007/s10494-023-00449-8","DOIUrl":"10.1007/s10494-023-00449-8","url":null,"abstract":"<div><p>OpenFOAM is one of the most widely used open-source computational fluid dynamics tools and often employed for chemical engineering applications. However, there is no systematic assessment of OpenFOAM’s numerical accuracy and parallel performance for chemically reacting flows. For the first time, this work provides a direct comparison between OpenFOAM’s built-in flow solvers as well as its reacting flow extension EBIdnsFoam with four other, well established high-fidelity combustion codes. Quantification of OpenFOAM’s numerical accuracy is achieved with a benchmark suite that has recently been established by Abdelsamie et al.?(Comput Fluids 223:104935, 2021. https://doi.org/10.1016/j.compfluid.2021.104935) for combustion codes. Fourth-order convergence can be achieved with OpenFOAM’s own cubic interpolation scheme and excellent agreement with other high-fidelity codes is presented for incompressible flows as well as more complex cases including heat conduction and molecular diffusion in multi-component mixtures. In terms of computational performance, the simulation of incompressible non-reacting flows with OpenFOAM is slower than the other codes, but similar performance is achieved for reacting flows with excellent parallel scalability. For the benchmark case of hydrogen flames interacting with a Taylor–Green vortex, differences between low-Mach and compressible solvers are identified which highlight the need for more investigations into reliable benchmarks for reacting flow solvers. The results from this work provide the first contribution of a fully implicit compressible combustion solver to the benchmark suite and are thus valuable to the combustion community. The OpenFOAM cases are publicly available and serve as guide for achieving the highest numerical accuracy as well as a basis for future developments.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"111 2","pages":"567 - 602"},"PeriodicalIF":2.4,"publicationDate":"2023-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-023-00449-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5119465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Active Flow Control of a High-Speed Train Wake Using Synthetic Jets","authors":"Chunjun Chen,&nbsp;Dongwei Wang","doi":"10.1007/s10494-023-00447-w","DOIUrl":"10.1007/s10494-023-00447-w","url":null,"abstract":"<div><p>To improve the aerodynamic performance of a high-speed train (HST) and reduce the safety risk of wake movement on platform commuters, trackside workers, and surrounding infrastructure, an active flow control method based on synthetic jets (SJs) is proposed to suppress the wake of the HST. The wake of the HST controlled by synthetic jets with different momentum coefficients is simulated by the improved delayed detached eddy simulation (IDDES) method embedded in ANSYS Fluent. Then, the slipstream velocity, aerodynamic force, velocity field in the wake region are analyzed. The results show that synthetic jets can effectively reduce the amplitude of the slipstream velocity in the wake region, the aerodynamic drag, and the fluctuation of the aerodynamic side force of the tail car. Furthermore, the synthetic jets delay the flow separation on the side of the tail car through periodic ejection and suction, and then attenuate the vortex motion in the wake region.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"111 2","pages":"439 - 461"},"PeriodicalIF":2.4,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5086053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Varying Internal Geometry on the Near-Field Spray Characteristics of a Swirl Burst Injector","authors":"Md. Nayer Nasim,&nbsp;Imtiaz Qavi,&nbsp;Lulin Jiang","doi":"10.1007/s10494-023-00441-2","DOIUrl":"10.1007/s10494-023-00441-2","url":null,"abstract":"<div><p>Clean and efficient combustion of liquid fuels depends on spray fineness that aids fast fuel vaporization and better fuel–air mixing. Swirl-burst (SB) atomizers generate fine droplets at the injector exit rather than typical jet cores as seen in the conventional atomizers. It integrates the primary breakup by bubble bursting of the Flow Blurring (FB) atomization, and secondary atomization by Rayleigh–Taylor instabilities between the swirling atomizing air and liquid phase. Thus, SB atomization has achieved clean lean-premixed flames of fuels with distinct properties involving diesel and straight oils around fifteen times more viscous. This study gains insights into the effect of the varying internal geometry, H/D ratio, on the atomization process and quantitatively investigates these effects on the near-field spray characteristics of SB injectors using high-spatial-resolution Shadowgraph Imaging Technique (SIT) and particle image velocimetry (PIV) for water sprays. Results acquired by SIT show that the Sauter Mean Diameter (SMD) of the droplets decrease with the reducing H/D ratio. The PIV measurements quantitatively reveal that atomization completion length decreases as the H/D ratio is lowered. Weber number analysis signifies that mostly vibrational and occasionally bag breakup dominates the secondary atomization for all the three H/D ratios. Results also reveal the high scalability of SB concept and its doubled atomization efficiency compared to FB injection.</p><h3>Graphical Abstract</h3>\u0000 <figure><div><div><div><picture><source><img></source></picture></div></div></div></figure>\u0000 </div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"111 2","pages":"641 - 674"},"PeriodicalIF":2.4,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5046225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Turbulence Effects on the Statistical Behaviour and Modelling of Flame Surface Density and the Terms of Its Transport Equation in Turbulent Premixed Flames","authors":"Arun Ravi Varma,&nbsp;Umair Ahmed,&nbsp;Nilanjan Chakraborty","doi":"10.1007/s10494-023-00430-5","DOIUrl":"10.1007/s10494-023-00430-5","url":null,"abstract":"<div><p>The influence of the ratio of integral length scale to flame thickness on the statistical behaviours of flame surface density (FSD) and its transport has been analysed using a Direct Numerical Simulation database of three-dimensional statistically planar turbulent premixed flames for different turbulence intensities. It has been found that turbulent burning velocity based on volume-integration of reaction rate and flame surface area increase but the peak magnitudes of the FSD and the terms of the FSD transport term decrease with an increase in length scale ratio for a given turbulence intensity. The flame brush thickness and flame wrinkling increase with an increase in length scale ratio for all turbulence intensities. However, the qualitative behaviours of the unclosed terms in the FSD transport equation remain unaltered by the length scale ratio and in all cases the tangential strain rate term and the curvature term act as leading order source and sink, respectively. A decrease in length scale ratio for a given turbulence intensity leads to a decrease in Damk?hler number and an increase in Karlovitz number. This has an implication on the alignment of reactive scalar gradient with local strain rate eigenvectors, which in turn increases positive contribution of the tangential strain rate term with a decrease in length scale ratio. Moreover, an increase in Karlovitz number increases the likelihood of negative contribution of the curvature term. Thus, the magnitude of the negative contribution of the FSD curvature term increases with a decrease in length scale ratio for a given turbulence intensity. The model for the tangential strain rate term, which explicitly considers the scalar gradient alignment with local principal strain rate eigenvectors, has been shown to be more successful than the models that do not account for the scalar gradient alignment characteristics. Moreover, the existing model for the curvature and propagation term needed modification to account for greater likelihood of negative values for higher Karlovitz number. However, the models for the unclosed flux of FSD and the mean reaction rate closure are not significantly affected by the length scale ratio.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"111 2","pages":"531 - 565"},"PeriodicalIF":2.4,"publicationDate":"2023-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-023-00430-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5165674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Study on Spray Characteristics of Nano-TiO2/Propylene Glycol Nanofluids","authors":"Junxiao Luo,&nbsp;Weidong Shi,&nbsp;Liang Chen,&nbsp;Guofeng Fang,&nbsp;Liang Zhang","doi":"10.1007/s10494-023-00434-1","DOIUrl":"10.1007/s10494-023-00434-1","url":null,"abstract":"<div><p>Nanofluids have become more and more attractive to the modern industry due to their high performance in heat transfer and combustion. As one of the key influencing factors, the atomization mechanism of nanofluids induced by airflow is more complex than that of pure liquids, which has attracted great attention recently. In this study, the spray characteristics of TiO₂–propylene glycol nanofluids were investigated by focusing on the effects of nano-TiO₂ additives on atomization. On the basis of high-speed shadow imaging, the spray morphology of the base fluid injected from an air atomizing nozzle under different pressures was analyzed first. Then a laser particle size analyzer was used to obtain the droplet size distribution of the nanofluids. The air pressure at the inlet of the atomizer was found to have more contribution to the atomization of nanofluids. And when the air pressure exceeded 0.35?MPa, the Sauter mean diameter (D₃₂) of the base fluid droplets was insensitive to the change of air pressure. Subsequently, the contribution of nanoparticles to atomization was discussed. An empirical correlation was proposed between the Sauter mean diameter (D₃₂) and the dimensionless parameters such as the gas Weber number (We_g), liquid–gas momentum ratio (q), and the volume fraction of nano-TiO₂, etc. Results indicated that adding nanoparticles enhanced the jet stability by increasing the viscosity at a low jet velocity, while the jet instability was increased due to the nanoparticles promoting the cavitation at a high jet velocity.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"111 2","pages":"697 - 715"},"PeriodicalIF":2.4,"publicationDate":"2023-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4827514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical Dissipation Rate Analysis of Finite-Volume and Continuous-Galerkin Methods for LES of Combustor Flow-Field","authors":"Vishal Saini,&nbsp;Hao Xia,&nbsp;Gary Page","doi":"10.1007/s10494-023-00428-z","DOIUrl":"10.1007/s10494-023-00428-z","url":null,"abstract":"<div><p>A growing body of literature indicates that element-based high-order methods can exhibit considerable accuracy/cost benefit over conventional second-order finite-volume (FV) methods for large-eddy simulations (LES). This may even hold true for complex configurations relevant to industry that involve under-resolving unstructured grids. However, it is not often clear whether the accuracy/cost benefit stems from the low-dissipative nature of the high-order numerical schemes or from using a different LES approach (implicit/explicit), or a combination of the two. The present paper employs a numerical dissipation rate analysis technique due to Schranner et al. (Comput Fluids 114:84–97, 2015) to better understand the reasons for the high-order benefit seen previously on a complex LES test case related to gas-turbine combustors. It is established that a high(fifth)-order LES run provides better accuracy than its second-order FV counterpart at the same computational cost primarily because of lower numerical dissipation and the LES model dissipation has a secondary role to play. The numerical dissipation is found to contribute 60–90% of the total (numerical and LES model) dissipation.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"111 1","pages":"81 - 113"},"PeriodicalIF":2.4,"publicationDate":"2023-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-023-00428-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5093211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flame Dynamics Modelling Using Artificially Thickened Models","authors":"Omer Rathore,&nbsp;Salvador Navarro-Martinez","doi":"10.1007/s10494-023-00433-2","DOIUrl":"10.1007/s10494-023-00433-2","url":null,"abstract":"<div><p>Thickened flame models are prolific in the literature and offer an effective method of resolving flame dynamics on coarse LES meshes. The current state of the art relies heavily on the use of efficiency functions to compensate for impaired wrinkling of the thickened flame. However in practice these functions can involve parameters that are difficult to determine, perform poorly outside of certain ranges or require a posteriori analysis to evaluate performance. An alternative based on a generalised thickening is evaluated across a range of canonical configurations. The approach is demonstrated to perform well across a large range of thickening factors in capturing phenomena such as localised quenching and pinch off as well as generation of flame surface. Including good performance even in the case of large flame dynamics under acoustic forcing where the model has a clear advantage over DNS in achieving grid independence. Finally the approach is unified into an Large Eddy Simulation/Adaptive Mesh Refinement framework and applied to a turbulent Bunsen flame. The results show that even if the internal flame structure is poorly resolved on the original mesh, the global system behaviour is well predicted and compares favourably with other approaches.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"111 3","pages":"897 - 927"},"PeriodicalIF":2.4,"publicationDate":"2023-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-023-00433-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"7183592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Investigation of Cyclic Variation of the In-Cylinder Flow in a Spark-Ignition Engine with a Charge Motion Control Valve","authors":"Fuquan Tian,&nbsp;Lei Shi,&nbsp;Zhizhao Che,&nbsp;Zhen Lu,&nbsp;Kai Sun,&nbsp;Tianyou Wang","doi":"10.1007/s10494-023-00429-y","DOIUrl":"10.1007/s10494-023-00429-y","url":null,"abstract":"<div><p>The cycle-to-cycle variations (CCV) have a substantial impact on the improvement of thermal efficiency and the expansion of operational limitations in internal combustion engines. For spark ignition engines, the variation of the in-cylinder flow field, especially the CCV of flow near the spark plug at the ignition timing, is a key factor causing the CCV of combustion. However, the physical mechanisms behind the CCV control of the in-cylinder flow field are still not well understood. The objective of this study is to determine how different tumble intensities induced by manipulating the opening and shutting of a tumble flap influence the flow CCV at the spark plug position at the ignition timing. High-speed particle image velocimetry (PIV) measurements were performed in an optically accessible single-cylinder, spark-ignited engine at a constant engine speed of 800?rpm. The frequency distributions of the velocity magnitude and flow angle are more concentrated under the high tumble intensity, indicating that the CCV of flow at the spark plug position at the ignition timing can be effectively reduced by closing the tumble flap. To gain a deeper insight into the mechanism of flow CCV alleviation, a correlation map analysis was employed, which can determine the relationship between the flow at the spark plug position and the flow distribution during the intake and compression stroke in time and space. To enhance the correlation between the above two, the proper orthogonal decomposition (POD) method was employed to extract the large-scale coherent structures and then the flow fields were reconstructed. The results demonstrated that the factors influencing the flow CCV under the tumble flap opening condition are primarily attributed to the CCV of the collision region position of the two intake jet flows in the later stage of the intake stroke and flow shear with the combustion chamber wall at the late compression stroke, while the factor influencing the flow CCV under the tumble flap closing condition is mostly connected to the CCV of tumble vortex position. Besides, closing the tumble flap can markedly increase the averaged kinetic energy and turbulent kinetic energy of the flow field in the vicinity of the spark plug position in the late compression stroke.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"111 2","pages":"743 - 766"},"PeriodicalIF":2.4,"publicationDate":"2023-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4388956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Representative Phenomena of Cyclic Turbulent Combustion in High-Pressure Fuel Sprays","authors":"Allen Parker,&nbsp;Ajay Agrawal,&nbsp;Joshua Bittle","doi":"10.1007/s10494-023-00432-3","DOIUrl":"10.1007/s10494-023-00432-3","url":null,"abstract":"<div><p>Cyclic variations in conventional diesel combustion engines can lead to large differences in engine out emissions even at steady operation. This study uses an optically accessible constant-pressure flow chamber to acquire fuel injections in quick succession to analyze mixing, auto-ignition, and combustion of diesel-surrogate n-heptane using multiple high-speed optical diagnostics. Prior studies have utilized fewer injections and/or they rely on analysis of ensemble average behavior. These approaches do not yield information on injection-to-injection variation or provide confidence in utilizing individual injection measurements for high-fidelity computational fluid dynamics(CFD) model validation. In this study, a large set of 500 injections is used to obtain global parameters including liquid length, vapor penetration length, ignition delay time, and lift-off length. Results for multiple injections are presented to illustrate large injection to injection variations. Potential sources for these variations are analyzed to conclude localized, small scale turbulence and rate of injection variations as the likely sources. Then, a statistical method based on z-scores is proposed and implemented to identify instantaneous injections that best represent the bulk data-set of jet boundaries measured independently by three different diagnostics. This synthesis of statistics-guided screening of data set and ensemble-average analysis offers higher confidence for CFD model validation relying upon both a representative single and average injection results.</p></div>","PeriodicalId":559,"journal":{"name":"Flow, Turbulence and Combustion","volume":"111 2","pages":"675 - 696"},"PeriodicalIF":2.4,"publicationDate":"2023-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10494-023-00432-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4309172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}