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Liu, Haijun, Zhanbin Guo, Lixin Zhao, Xinyu Wang, and Shan Lan. "Numerical simulation and experimental verification of stability on multi-cavity spiral cascade heat transfer system." Thermal Science, no. 00 (2020): 319. http://dx.doi.org/10.2298/tsci200625319l.
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In order to improve the insufficient effect of heat transfer in pyrolysis carbonization system and reveal the effects of velocity and temperature field of hot flue gas on heat transfer and stability in the biomass, the structure with rectangular groove combined with a spiral baffle is designed to form a multi-cavity spiral cascade heat transfer system. Numerical simulation and experimental verification of stability are carried on multi-cavity spiral cascade heat transfer system. The results show that the hot flue gas with high temperature flows fast at the inlet and outlet, while the flow speed is slow and stable in the cavity of heat transfer. The temperature of hot flue gas reaches the highest at the entrance, and decreases in the heat exchange chamber in a cascade. The spiral inclination angle of 35? and the pitch of 1.2m. The combustion of gas produced by pyrolysis of raw materials can meet the requirement of continuous and stable operation, when the temperature of monitor point 1, 3, 6 and 8 reaches 800 ?, 530 ?, 250 ?and 200 ? respectively. The temperature of hot flue gas changes fluctuate in the range of 15 ?. The combustion of pyrolysis gas generated during the pyrolysis process of raw materials can ensure the continuous and stable operation of the equipment.
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Chang, Y. C., and M. C. Chiu. "Optimization of Rectangular Multi-Chamber Plenums Equipped with Multiple Extended Tubes Using the BEM, Neural Networks, and the Genetic Algorithm." Journal of Mechanics 30, no. 6 (October 21, 2014): 571–84. http://dx.doi.org/10.1017/jmech.2014.66.
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AbstractThe focal point of this paper is to uncover, by analyzing the higher order wave effect, an improved mechanism for space-constrained rectangular plenums using a simplified objective function in conjunction with a genetic (GA). Three kinds of rectangular mufflers hybridized with extended tubes will be assessed: Plenum A: A two-chamber plenum equipped with an extended tube; plenum B: A three-chamber plenum with two extended tubes; and plenum C: A two-chamber plenum equipped with three extended tubes. In order to shorten the numerical assessment, a simplified objective function (OBJ) is established using a boundary element model (BEM) in conjunction with the neural network model (NNM). To expediently approach an optimal plenum, the best OBJ will be numerically searched using a genetic algorithm (GA). However, before the GA operation is performed, the accuracy of the BEM is verified using analytical data. And, because the simplified objective function (OBJ) is seen to be in agreement with the BEM, the numerical cases of sound elimination relative to the various parameter sets and pure tones (300, 750, and 1300Hz) can be carried out.Results reveal that the maximum value of the sound transmission loss (STL) can be accurately obtained at the desired frequencies. Additionally, the acoustical performance of the lower frequencies will be improved if the number of chambers and rectangular tubes are increased. However, the acoustical performance of the higher frequencies will decrease when the number of chambers and rectangular tubes are decreased. Consequently, the algorithms proposed in this study will efficiently develop optimal rectangular plenums with multiple rectangular extended tubes.
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Philo, John J., Rohan M. Gejji, and Carson D. Slabaugh. "Injector-coupled transverse instabilities in a multi-element premixed combustor." International Journal of Spray and Combustion Dynamics 12 (January 2020): 175682772093283. http://dx.doi.org/10.1177/1756827720932832.
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Combustion instabilities in a high-pressure, multi-element combustor are studied in order to understand the relationship between the chamber and injector dynamics. A linear array of seven injectors supplies premixed natural gas and air into a rectangular combustion chamber designed to promote high-frequency, transverse thermoacoustic instabilities. The effect of equivalence ratio on the combustion dynamics was investigated for two injector lengths, 62.5 and 125 mm. For all operating conditions, the 125 mm injectors promote high-amplitude instabilities of the fundamental transverse (1T) mode, which has a frequency of 1750–1850 Hz. Reducing the injector length significantly lowers the instability amplitudes for all operating conditions and, for lower equivalence ratio cases, excites an additional mode near 1550 Hz. The delineating feature controlling the growth of the instabilities in each injector configuration is the coupling with axial pressure fluctuations in the injectors that occur in response to the transverse modes in the chamber.
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Krupińska, Andżelika, Marek Ochowiak, Sylwia Włodarczak, Magdalena Matuszak, and Julia Kaźmierczak. "Analysis of the dedusting process in a rectangular chamber filter." Polish Journal of Chemical Technology 24, no. 4 (December 1, 2022): 72–77. http://dx.doi.org/10.2478/pjct-2022-0031.
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Abstract Purifying air from dust is a very important, current topic. There are many methods to minimize the amount of dust, one of them being chamber filters. This paper presents the research results of a newly designed rectangular chamber filter. The efficiency of the dedusting process is influenced by contamination properties, but also by the construction of the apparatus, inlet, and outlet location, the ratio of certain dimensions, and the gas flow rate. The airflow containing solid particles is a multi-phase, difficult-to-describe issue, therefore an attempt to determine the trajectory of particle movement in the apparatus was carried out using the PIV method. A decrease in the dedusting efficiency was observed with the increase of the gas flow rate, as well as for smaller diameters of the solid particles. The obtained values of the efficiency of the apparatus are comparable with the values obtained for the constructions discussed in other papers.
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Zhang, Wanqing, Xin Gao, and Angui Li. "Effects of multi-orifice plate with different geometric parameters on flow distribution of plenum chamber for ventilation duct systems." E3S Web of Conferences 356 (2022): 02044. http://dx.doi.org/10.1051/e3sconf/202235602044.
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Plenum chambers are common devices used for flow and pressure equalization in ventilation and air conditioning systems. Aiming for reducing energy consumption and improving ventilation performance, the optimal cross-sectional aspect ratio (W/H) and length (L) of the single-path unlined rectangular plenum chamber is obtained through the authors’ preliminary research. In this study, based on the analysis of interior flow characteristics of single-path plenum chamber, it is shown that the traditional chamber configuration commonly used in engineering is not an ideal structure that can achieve uniform flow distribution. The multi-orifice plate is proposed to add inside chamber to improve flow uniformity. Under the two typical design schemes of W/H=1/1 and 5/1, the effect of multi-orifice plate with different geometric parameters on flow distribution of plenum chamber is investigated, and the optimal installation position and aperture rate of orifice plate is proposed. The optimized aperture ratio is designed to be 30% for both the two typical chamber configurations. When W/H=1/1, it is recommended to install the multi-orifice plate at the position of y/L=0.1, as for W/H=5/1, the y/L=0.3 is preferred. Besides, the fluid equalizing effect of the plenum chamber with multi-orifice plate is verified under four commonly used air ducts specifications in engineering.
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Kim, Hongsuck, Byunggoon Kim, Jiyeon Kim, and Jaecheul Yu. "Effect of organic loading rates and influent sources on energy production in multi-baffled single chamber microbial fuel cell." Desalination and Water Treatment 56, no. 5 (August 18, 2014): 1217–22. http://dx.doi.org/10.1080/19443994.2014.950986.
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Chiu, Min-Chie, Ying-Chun Chang, Ho-Chih Cheng, and Wei-Ting Tai. "Shape Optimization of Mufflers Composed of Multiple Rectangular Fin-Shaped Chambers Using Differential Evolution Method." Archives of Acoustics 40, no. 3 (September 1, 2015): 311–19. http://dx.doi.org/10.1515/aoa-2015-0034.
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Abstract There has been considerable research done on multi-chamber mufflers used in the elimination of industrial venting noise. However, most research has been restricted to lower frequencies using the plane wave theory. This has led to underestimating acoustical performances at higher frequencies. Additionally, because of the space-constrained problem in most plants, the need for optimization of a compact muffler seems obvious. Therefore, a muffler composed of multiple rectangular fin-shaped chambers is proposed. Based on the eigenfunction theory, a four-pole matrix used to evaluate the acoustic performance of mufflers will be deduced. A numerical case for eliminating pure tones using a three-fin-chamber muffler will also be examined. To delineate the best acoustical performance of a space-constrained muffler, a numerical assessment using the Differential Evolution (DE) method is adopted. Before the DE operation for pure tone elimination can be carried out, the accuracy of the mathematical model must be checked using experimental data. The results reveal that the broadband noise has been efficiently reduced using the three-fin-chamber muffler. Consequently, a successful approach in eliminating a pure tone using optimally shaped three-fin-chamber mufflers and a differential evolution method within a constrained space has been demonstrated.
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Guo, Kangkang, Yongjie Ren, Yiheng Tong, Wei Lin, and Wansheng Nie. "Analysis of self-excited transverse combustion instability in a rectangular model rocket combustor." Physics of Fluids 34, no. 4 (April 2022): 047104. http://dx.doi.org/10.1063/5.0086226.
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A methane/oxygen mixture is considered to be an appropriate propellant for many future rocket engines due to its practicality and low cost. To better understand the combustion instability in methane/oxygen-fed rocket engines, the spontaneous transverse combustion instability in a rectangular multi-element combustor (RMC) was analyzed both experimentally and numerically. Severe combustion instabilities occurred in the RMC during repeatable hot-fire tests. The physical mechanisms were systematically investigated through numerical simulations based on the stress-blended eddy simulation and flamelet-generated manifolds method with detailed chemical mechanisms (GRI Mech 3.0). The numerical results for the frequency spectrum and spatial modes agree well with the theoretical analysis and experimental data. The driven regions of the combustion instability were identified on both sides of the combustion chamber through a Rayleigh index analysis. The longitudinal pressure oscillations in the oxidizer post were found to be coupled with the transverse pressure waves in the combustion chamber and led to periodic oscillations of the mass flow rate of propellant. Moreover, the mixing was highly enhanced when the pressure wave interacted with walls of the combustion chamber. Therefore, a sudden release of heat occurred. The pressure oscillations were enhanced by pulsated heat release. A closed-loop system with positive feedback associated with periodic oscillations mass flow rate of the propellant, and sudden heat release, was believed to account for the present combustion instability.
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Yang, Shiliang, Hua Wang, Yonggang Wei, Jianhang Hu, and Jia Wei Chew. "Particle-scale characteristics of the three distinct regions in the multi-chamber slot-rectangular spouted bed." Powder Technology 360 (January 2020): 658–72. http://dx.doi.org/10.1016/j.powtec.2019.10.038.
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Yi, Tae-Hyeong, Jing Lou, Cary Kenny Turangan, and Piotr Wolanski. "Numerical Study of Detonation Processes in Rotating Detonation Engine and its Propulsive Performance." Transactions on Aerospace Research 2020, no. 3 (September 1, 2020): 30–48. http://dx.doi.org/10.2478/tar-2020-0015.
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AbstractNumerical studies on detonation wave propagation in rotating detonation engine and its propulsive performance with one- and multi-step chemistries of a hydrogen-based mixture are presented. The computational codes were developed based on the three-dimensional Euler equations coupled with source terms that incorporate high-temperature chemical reactions. The governing equations were discretized using Roe scheme-based finite volume method for spatial terms and second-order Runge-Kutta method for temporal terms. One-dimensional detonation simulations with one- and multi-step chemistries of a hydrogen-air mixture were performed to verify the computational codes and chemical mechanisms. In two-dimensional simulations, detonation waves rotating in a rectangular chamber were investigated to understand its flowfield characteristics, where the detailed flowfield structure observed in the experiments was successfully captured. Three-dimensional simulations of two-waved rotating detonation engine with an annular chamber were performed to evaluate its propulsive performance in the form of thrust and specific impulse. It was shown that rotating detonation engine produced constant thrust after the flowfield in the chamber was stabilized, which is a major difference from pulse detonation engine that generates repetitive and intermittent thrust.
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Pawar, Ajinkya M., and Shishir Singh. "The morphology of the pulp chamber floor of permanent mandibular first and second molars in an Indian subpopulation—a descriptive cross-sectional study employing Pawar and Singh classification." PeerJ 10 (November 29, 2022): e14392. http://dx.doi.org/10.7717/peerj.14392.
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Background Mandibular molars are multi-rooted teeth with a complex and strenuous root canal anatomy. Because there is relatively negligible literature describing the pulp chamber floor anatomy, predicting the exact anatomical layout and its variations is daunting. A thorough comprehension and knowledge of the same is required for efficacious endodontic treatment consequence. The purpose of this study was to characterise and ascertain the pulp chamber floor anatomy of permanent mandibular first (ManFMs) and second (ManSMs) molars in an Indian population. Methods On 2,134 extracted human mandibular first (ManFMs = 1,067) and second molars (ManSMs = 1,067), a descriptive cross-sectional investigation was executed. Cleaning and removal of hard and soft tissue debris were performed, followed by flattening the anatomical crown until the pupal architecture was uncovered. A stereomicroscope with a magnification of 4.5 magnification was used to investigate the pulpal anatomy. Statistical analysis was carried out using chi square test, with 95% confidence intervals and a p value of 0.05 considered statistically significant. Results The majority of the ManFMs showed presence of three canal orifices in 57.73%, followed by four orifices 31.31%, five orifices 8.81%, and six orifices 2.15%. For ManSMs, majorly three orifices were found in 39.83% specimens, followed by two orifices in 37.39%, four orifices in 16.31%, and single root canal orifice was observed in 6.47%. The mesio-buccal, mesio-lingual, disto-buccal, disto-lingual canal orifices exhibited round and oval shapes in both ManFMs and ManSMs. The shape was predominantly oval with a single distal canal orifice (84.25% ManFMs and 74.16% ManSMs). In ManSMs, among the single root canal orifice, 66.66% were round in shape and 33.34% were C-shaped. In ManSMs with two root canal orifices, mesially 79.44% exhibited oval and 20.56% round shape. Distally, 74.16% were oval and 25.84% were round. The shapes of the access cavities for ManFMs were rectangular in 46.67% and triangular in 53.33%. For the ManSMs, the access cavities were triangular in 39.83%, rectangular in 16.31% and non-classified (others) in 43.86% of specimen. In both ManFMs and ManSMs, the pulp chamber floor morphology was predominately Y shaped (57.73% and 39.83%) according to the Pawar and Singh classification© of pulp chamber floor anatomy. Conclusion Our study indicated that the orifices on the pulp chamber floor are arranged in a typical manner, supporting the proposed categorization. Furthermore, description of the anatomical patterns of the pulp chamber guides the clinicians in chair-side treatment decisions.
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Li, Mi, Xiao Wu, Dongxue Han, Renyu Peng, Yong Yang, Li Wu, and Wencong Zhang. "A High-Efficiency Single-Mode Traveling Wave Reactor for Continuous Flow Processing." Processes 10, no. 7 (June 24, 2022): 1261. http://dx.doi.org/10.3390/pr10071261.
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This paper proposes a high-efficiency single-mode traveling wave reactor based on a rectangular waveguide and its design method for continuous flow processing. The reactor has a large-capacity reaction chamber (1000 mm × 742.8 mm × 120 mm) that can provide high-energy-efficiency and approximately uniform microwave heating. The microwave heating uniformity is improved by maintaining single-mode microwave transmission and eliminating higher-order modes in such a multi-mode reaction chamber. The high energy efficiency of microwave heating is achieved by adopting impedance matching techniques. The incident microwave in the reactor can remain in a traveling wave state, and the power reflection can be minimized. Several numerical simulations based on multi-physics modeling are conducted to investigate the heating uniformity, the energy efficiency and the flexibility under different operation conditions. The results show the microwave energy efficiency can be higher than 99%, and meanwhile, the coefficient of temperature variation can be lower than 0.4. Furthermore, when the reactor is operated under different flow velocities and with different heating materials, both the energy efficiency and the heating uniformity can also meet the above requirements. The proposed reactor can be used in the applications such as oil processing, wastewater tackling, chemical synthesis, beverage sterilization and other microwave-assisted continuous flow processes that require high heating uniformity, high energy efficiency and good adaptability.
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Pappas, Vasileios M., Achillia Lakka, Dimitrios Palaiogiannis, Vassilis Athanasiadis, Eleni Bozinou, George Ntourtoglou, Dimitris P. Makris, Vassilis G. Dourtoglou, and Stavros I. Lalas. "Optimization of Pulsed Electric Field as Standalone “Green” Extraction Procedure for the Recovery of High Value-Added Compounds from Fresh Olive Leaves." Antioxidants 10, no. 10 (September 29, 2021): 1554. http://dx.doi.org/10.3390/antiox10101554.
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Olive leaves (OLL) are reported as a source of valuable antioxidants and as an agricultural by-product/waste. Thus, a twofold objective with multi-level cost and environmental benefits arises for a “green” standalone extraction technology. This study evaluates the OLL waste valorization through maximizing OLL extracts polyphenol concentration utilizing an emerging “green” non-thermal technology, Pulsed Electric Field (PEF). It also provides further insight into the PEF assistance span for static solid-liquid extraction of OLL by choosing and fine-tuning important PEF parameters such as the extraction chamber geometry, electric field strength, pulse duration, pulse period (and frequency), and extraction duration. The produced extracts were evaluated via comparison amongst them and against extracts obtained without the application of PEF. The Folin-Ciocalteu method, high-performance liquid chromatography, and differential scanning calorimetry were used to determine the extraction efficiency. The optimal PEF contribution on the total polyphenols extractability (38% increase with a 117% increase for specific metabolites) was presented for rectangular extraction chamber, 25% v/v ethanol:water solvent, pulse duration (tpulse) 2 μs, electric field strength (E) 0.85 kV cm−1, 100 μs period (Τ), and 15 min extraction duration (textraction), ascertaining a significant dependence of PEF assisting extraction performance to the parameters chosen.
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Trine, Allison, Margaret Miller, Emily Buss, G. Christopher Stecker, and Brian B. Monson. "Speech directivity patterns generated from a high-fidelity speech corpus." Journal of the Acoustical Society of America 153, no. 3_supplement (March 1, 2023): A292. http://dx.doi.org/10.1121/10.0018894.
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Human talkers are directional sound sources—a phenomenon that has consequences for speech perception in multi-talker environments. Directivity patterns for speech showing frequency- and angle-dependent radiation reveal that speech generally becomes more directional toward the front of the talker as frequency increases. Differences in physical attributes can lead to individual variability in directivity patterns across talkers. Here, we examine individual variability in speech directivity using frequency-dependentdirectivity indices and directivity maps. Speech directivity was examined in the horizontal plane using a corpus of simultaneous multi-channelfull-bandwidth (48-kHz sampling rate) recordings of the Bamford-Kowal-Bench (BKB) sentences recorded in an anechoic chamber. Thirty subjects (15 female) were recorded. The long-term average speech spectrum was utilized to calculate directivity indices in 1-ERB (equivalent rectangular bandwidth) bands. Gender differences in directivity indices were evaluated using a linear mixed-effects model. There was no main effect of gender. There was a main effect of ERB band with higher-frequency bands tending to have higher (i.e., more directional) directivity indices, however there was a nonmonotonic relationship between average directivity indices and frequency. Directivity maps demonstrated individual differences in speech radiation. [Work supported by NIH under Grant No. R01-DC019745.]
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Jauvin, Matthias, Yajing Yan, Emmanuel Trouvé, Bénédicte Fruneau, Michel Gay, and Blaise Girard. "Integration of Corner Reflectors for the Monitoring of Mountain Glacier Areas with Sentinel-1 Time Series." Remote Sensing 11, no. 8 (April 25, 2019): 988. http://dx.doi.org/10.3390/rs11080988.
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Glacier flow and slope instabilities in Alpine mountain areas represent a hazard issue. Sentinel-1 satellites provide regular Synthetic Aperture Radar (SAR) acquisitions that are potentially useful to monitor these areas, but they can be affected by temporal decorrelation due to rapid changes in the surface. The application of interferometric synthetic aperture radar (InSAR) therefore seems difficult due to loss of coherence. On the other hand, Corner Reflectors (CR) can be used as coherent targets in SAR images for accurate displacement measurement thanks to their strong backscattering property and temporal stability. The use of CRs in multi-temporal InSAR analysis in Alpine mountain areas can thus be beneficial. In this study, we present a comparison between triangular and rectangular CRs, based on Radar Cross Section (RCS) measurements in an anechoic chamber and on long-term experiments over the Argentière glacier and the surrounding slopes and moraine. The visibility in both summer and winter of 10 CRs installed on the test site was investigated. As this area is exposed to heavy precipitation including snow falls, two perforated CRs were tested. The amplitude stability and the phase error of each CR were estimated. A precise tracking of two CRs installed at the glacier surface was also able to measure the displacement of the Argentière glacier, giving results close to previous GPS measurements. Furthermore, a Persistent Scatterer Interferometry (PSI) study was conducted, using the most stable CR as reference point to estimate slope instabilities, which led to the identification of an area corresponding to a tectonic fault called “Faille de l’angle”. The precise absolute locations of the CRs were successfully estimated and PS heights were compared with a LiDAR-based (Light Detection And Ranging) digital elevation model (DEM) and GPS measurements.
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"The excavation of tomb M1 in Quangou cemetery, Wulan County, Qinghai." Chinese Archaeology 21, no. 1 (November 1, 2021): 91–106. http://dx.doi.org/10.1515/char-2021-0006.
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Abstract Tomb M1 at Quangou cemetery in Wulan, Qinghai, is the only Tubo-period tomb with mural paintings discovered thus far on the Qinghai-Xizang Plateau. The tomb includes a tomb entry ramp leading to a rectangular multi-chambered structure built from bricks and timber. The walls of the antechamber and burial chamber are all painted with various images heavily influenced by typical Tang painting techniques, displaying Tang-period stylistic influence, although painted subjects present characteristic scenes of nomadic life on the Qinghai-Xizang Plateau. The color-painted lacquered coffins in the tomb are the first of their kind found in the region, indicating that the tomb occupant must have been of high social status. There is a secret compartment behind the tomb’s burial chamber, where a wooden chest was found containing a luxuriously decorated gilt silver crown and a turquoise-inlaid gold cup. The findings suggest that the tomb occupant was probably closely related to the local royal family under Tubo’s sovereignty.
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Abdollahzadeh Jamalabadi, Mohammad Yaghoub, Noemi Zabari, and Łukasz Bratasz. "Three-dimensional numerical and experimental study of fracture saturation in panel paintings." Wood Science and Technology, September 22, 2021. http://dx.doi.org/10.1007/s00226-021-01328-z.
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AbstractPanel paintings—complex multi-layer structures consisting of wood support and a paint layer composed of a preparatory layer of gesso, paints, and varnishes—are among the category of cultural objects most vulnerable to relative humidity fluctuations and frequently found in museum collections. The current environmental specifications in museums have been derived using the criterion of crack initiation in an undamaged, usually new gesso layer laid on wood. In reality, historical paintings exhibit complex crack patterns called craquelures. The present paper analyses the structural response of a paint layer with a virtual network of rectangular cracks under environmental loadings using a three-dimensional model of a panel painting. Two modes of loading are considered—one induced by one-dimensional moisture response of wood support, termed the tangential loading, and the other isotropic induced by drying shrinkage of the gesso layer. The superposition of the two modes is also analysed. The modelling showed that minimum distances between cracks parallel to the wood grain depended on the gesso stiffness under the tangential loading. Despite a nonzero Poisson’s ratio, gesso cracks perpendicular to the wood grain could not be generated by the moisture response of the wood support. The isotropic drying shrinkage of gesso produced cracks that were almost evenly spaced in both directions. The modelling results were cross-checked with crack patterns obtained on a mock-up of a panel painting exposed to several extreme environmental variations in an environmental chamber.