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Academic literature on the topic 'Plug length ratio'

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Published: 4 June 2021

Last updated: 1 February 2022

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Journal articles on the topic "Plug length ratio"

Rezzoug, A., A. Alexis, and P. Thomas. "Écoulement à surface libre dans un massif de sol soumis à la marée : comparaison théorie-expérimentation." Canadian Geotechnical Journal 36, no. 1 (August 8, 1999): 13–20. http://dx.doi.org/10.1139/t98-078.

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We analyze analytically and numerically the stress distribution along the plug-rock interface and within an axially loaded plug emplaced in a borehole in rock. Experiments show that the interface strength increases with decreasing plug radius and with increasing plug length. Axial strength decreases as a power law of plug radius. An increase in the modulus ratio (ratio of plug modulus to rock modulus) increases the interface strength, until it levels off at a ratio of about 5.0. For short plugs, the tensile stresses may reach a magnitude significant to be of concern for long-term stability of the plug and of the host rock. Out studies suggest designing friction plugs with a length to radius ratio of at least 8.0. In practice, especially for short-term performance, e.g., emergency flood control or temporary diversions, a ratio of 8.0 may not be necessary or justified. For permanent abandonment plugs, it is essential to reduce the tensile stresses in the plug and in the host rock to a level that will minimize the risk of long-term deterioration. We recommend in situ experiments on larger diameter plugs to assess the validity of the proposed size effect extrapolation obtained in this study. Key words: borehole plugging (sealing), shaft seal design, plug-rock interface strength, axial strength, bond strength, cement grout.

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Akgün, Haluk, and Jaak JK Daemen. "Design implications of analytical and laboratory studies of permanent abandonment plugs." Canadian Geotechnical Journal 36, no. 1 (August 8, 1999): 21–38. http://dx.doi.org/10.1139/t98-089.

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We analyze analytically and numerically the stress distribution along the plug-rock interface and within an axially loaded plug emplaced in a borehole in rock. Experiments show that the interface strength increases with decreasing plug radius and with increasing plug length. Axial strength decreases as a power law of plug radius. An increase in the modulus ratio (ratio of plug modulus to rock modulus) increases the interface strength, until it levels off at a ratio of about 5.0. For short plugs, the tensile stresses may reach a magnitude significant to be of concern for long-term stability of the plug and of the host rock. Our studies suggest designing friction plugs with a length to radius ratio of at least 8.0. In practice, especially for short-term performance, e.g., emergency flood control or temporary diversions, a ratio of 8.0 may not be necessary or justified. For permanent abandonment plugs, it is essential to reduce the tensile stresses in the plug and in the host rock to a level that will minimize the risk of long-term deterioration. We recommend in situ experiments on larger diameter plugs to assess the validity of the proposed size effect extrapolation obtained in this study.Key words: borehole plugging (sealing), shaft seal design, plug-rock interface strength, axial strength, bond strength, cement grout.

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Tang, Geng, Hui Yan, Jun Li, Xue Feng Song, Xin Zhang, and Xue Li Guo. "Sealing Analysis of Cement Plug in Offshore Abandoned Wells." Materials Science Forum 993 (May 2020): 1333–40. http://dx.doi.org/10.4028/www.scientific.net/msf.993.1333.

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A three-dimensional finite element model of stratum-cement ring-casing-cement plug was established for the failure analysis of the cement plug seal in the abandoned oil and gas wells. The mechanical parameters, length, bottom fluid pressure and casing swaging length of the cement plug under non-uniform ground stress conditions were analyzed. The results showed that when the bottom of the cement plug was subjected to fluid pressure, the stress at the interface between the cement plug and the casing increased, and thereby the cement plug at the bottom and the cementation of the casing failed, resulting in a the decrease in the sealing performance of the cement plug, which may be sealed under fluid corrosion. As the modulus of elasticity and the radius of the cement plug increased, the cement plug stress and the cement failure length increased. As the cement plug length increased, the cement plug stress and the cement failure length decreased, while Poisson's ratio for the cement plug stress and the cement failure length increased. The increase of the bottom fluid pressure could increase the cement plug stress and the cementation failure length. In the abandoned well, where the casing was forged and then grinded after the casing was forged, the length of the casing milling increased, the plug stress of cement reduced. These findings can provide insightful potentials for the parameters of cement plugs when the cement plugs are closed in the offshore oil and gas wells.

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Sano, Yukio, Koji Tokushima, and Tokujiro Inoue. "Multishock Compactions of a Die-Contained Copper Powder Medium Analyzed by Improved Theory." Journal of Pressure Vessel Technology 113, no. 4 (November 1, 1991): 560–69. http://dx.doi.org/10.1115/1.2928796.

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In the present paper, the multishock compaction process of a die-contained copper powder medium supported by an elastic plug at one end and impacted by an elastic punch at the other end, is analyzed by means of an improved theory having the effect of elasticity of the punch and plug. The compactions computed first have a constant sum of lengths of the medium and plug S0*=110, a constant ratio of punch mass to powder mass filled in the die M*=20, and an initial punch velocity ν0=50m/s. The computations of the compactions for the medium with very short lengths and the plug with long lengths confirm the existence of the medium length Scr1* corresponding to the first critical plug-length found in the previous study, and support the compaction process and the final mean density ρmean*-initial medium length S* relation of the medium shorter than the length Scr1* which were inferred in the study. Furthermore, the effect of elastic waves in the punch and plug on the process of the medium longer than Scr1* are examined. There are one common factor and one significant different factor in the processes. Explicitly, the waves in the plug exert different influence on compaction processes of the medium with different lengths, whereas the waves in the punch have similar influence on the processes. The elastic waves in the plug and die wall friction cause the medium length Scr2* corresponding to the second critical plug-length inferred in the previous study. Moreover, the waves in the plug make the form of the computed relation curve more complicated than the inferred one. The computed curve has the lengths Scr3* and Scr4* at which the density has an extreme value, respectively. Approximate similarity conditions for the compactions with various values of S0* are given by two fixed parameters M* and ν0 in region S*<Scr1*, three fixed parameters S*/S0*, M*, and ν0 in region from Scr1* to small S* where the wall friction effect can be neglected, and three fixed parameters S*, M*, and ν0 in region S*>(1/2)S0*. The computed ρmean*–S* and ρmean*–S*/S0* relations support these conditions. Furthermore, the computations of the compactions reveal that the waves in the punch, medium, and plug behave in similar manner during the processes, though they have different strengths.

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Ko, Junyoung, and Sangseom Jeong. "Plugging effect of open-ended piles in sandy soil." Canadian Geotechnical Journal 52, no. 5 (May 2015): 535–47. http://dx.doi.org/10.1139/cgj-2014-0041.

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This paper presents an experimental study of the plugging effect on the capacity of open-ended piles installed in sandy soil. Full-scale tests, including dynamic and static axial compression load tests, were carried out on three instrumented piles with different diameters (508.0, 711.2, and 914.4 mm). To measure the outer and inner shaft resistances acting on the piles, a double-walled system was utilized, with instrumented strain gauges on the outside and inside walls of the pile. The results of field tests show that the inner shaft resistance was mostly mobilized at the location between the pile tip and 18%–34% of the total plug length. It was found that the soil plugging in the lower portion has influence on the inner shaft resistance. In addition, it can be also demonstrated that the ratio of inner shaft resistance plus annulus load resistance to total resistance was decreased with increasing pile diameters. The results of these tests show that the relationship between the degree of plugging and pile diameter is clearly established. Direct observations of the soil plugs were made and used to quantify both the plug length ratio (PLR) and the incremental filling ratio (IFR). Based on this result, it was realized that the N value of the standard penetration test (SPT) is highly correlated with the IFR.

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Jain, Sneha M., Priya M. Pradhan, Supratim Sen, and Bharat V. Dalvi. "Transcatheter closure of elongated and pulmonary hypertensive patent arterial duct in infants using Amplatzer vascular plug II." Cardiology in the Young 30, no. 2 (January 30, 2020): 243–48. http://dx.doi.org/10.1017/s1047951120000104.

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AbstractObjective:To evaluate the feasibility, efficacy, and safety of Amplatzer vascular plug II in large and elongated ducts in infants.Introduction:Patent arterial duct device closure is technically challenging in infants with large and elongated ducts because Amplatzer duct occluder and Amplatzer duct occluder II have high chances of causing aortic coarctation and left pulmonary artery stenosis, respectively. The Amplatzer vascular plug II being soft with no retention discs on either sides helps in mitigating these problems.Method:This is a prospective, observational study involving infants with clinical, echocardiographic and angiographic evidence of large left to right shunt. All the children underwent duct closure using Amplatzer vascular plug II.Results:Eighteen infants qualified for the study. Mean age and weight were 8.63 ± 3.84 months and 6.3 ± 1.7 kg, respectively. The angiographic mean duct diameter at the pulmonary artery end was 4.66 ± 0.92 mm, and the mean duct length was 9.4 ± 2.48 mm. The size of Amplatzer vascular plug II used varied from 6 mm to 10 mm. Technical success was achieved in 16/18 cases. One patient had device embolisation, and in the other, the device was found to be unstable. The ratio of Amplatzer vascular plug II size to the duct diameter was 1.65 ± 0.27, while the ratio of ductal length to device length was 1.48 ± 0.46 in those with successful outcome.Conclusions:Amplatzer vascular plug II is a safe and effective option in appropriately selected infants with elongated ducts. Diameter and length of Amplatzer vascular plug II vis-a-vis those of the ductus are important determinants of the successful outcome.

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Jiang, Xiu Gen, Yang Yang, Feng Jie Zhang, Jin San Ju, and Xiao Chuan You. "Analysis of the Load-Carrying Capability of the Casing Plug Joint of Steel Tube Structures Considering the Contact Effect." Advanced Materials Research 33-37 (March 2008): 321–26. http://dx.doi.org/10.4028/www.scientific.net/amr.33-37.321.

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Nonlinear finite element model analysis of the casing plug joints of steel tubular has been realized by ANSYS software. The law of load-carrying capability and stiffness of joint are separately gained by changing the ratio of length and diameter (R/L) and the ratio of the casing length and the main tube length (l/L). The influence of the casing thickness on the load-carrying capability and stiffness are also discussed. The results indicated that the load-carrying capability and stiffness of the joints both increase with the ratio(R/L) increment and the ratio of the casing length and main tube length (l/L). When the main tube thickness is equal to casing thickness, the load-carrying capacity of joints achieves the most.

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Cassidy, K. J., N. Gavriely, and J. B. Grotberg. "Liquid Plug Flow in Straight and Bifurcating Tubes." Journal of Biomechanical Engineering 123, no. 6 (June 7, 2001): 580–89. http://dx.doi.org/10.1115/1.1406949.

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A finite-length liquid plug may be present in an airway due to disease, airway closure, or by direct instillation for medical therapy. Air forced by ventilation propagates the plug through the airways, where it deposits fluid onto the airway walls. The plug may encounter single or bifurcating airways, an airway surface liquid, and other liquid plugs in nearby airways. In order to understand how these flow situations influence plug transport, benchtop experiments are performed for liquid plug flow in: Case (i) straight dry tubes, Case (ii) straight pre-wetted tubes, Case (iii) bifurcating dry tubes, and Case (iv) bifurcating tubes with a liquid blockage in one daughter. Data are obtained for the trailing film thickness and plug splitting ratio as a function of capillary number and plug volumes. For Case (i), the finite length plug in a dry tube has similar behavior to a semi-infinite plug. For Case (ii), the trailing film thickness is dependent upon the plug capillary number (Ca) and not the precursor film thickness, although the shortening or lengthening of the liquid plug is influenced by the precursor film. For Case (iii), the plug splits evenly between the two daughters and the deposited film thickness depends on the local plug Ca, except for a small discrepancy that may be due to an entrance effect or from curvature of the tubes. For Case (iv), a plug passing from the parent to daughters will deliver more liquid to the unblocked daughter (nearly double, consistently) and then the plug will then travel at greater Ca in the unblocked daughter as the blocked. The flow asymmetry is enhanced for a larger blockage volume and diminished for a larger parent plug volume and parent-Ca.

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Zheng, Y., H. Fujioka, J. C. Grotberg, and J. B. Grotberg. "Effects of Inertia and Gravity on Liquid Plug Splitting at a Bifurcation." Journal of Biomechanical Engineering 128, no. 5 (April 19, 2006): 707–16. http://dx.doi.org/10.1115/1.2246235.

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Liquid plugs may form in pulmonary airways during the process of liquid instillation or removal in many clinical treatments. During inspiration the plug may split at airway bifurcations and lead to a nonuniform final liquid distribution, which can adversely affect treatment outcomes. In this paper, a combination of bench top experimental and theoretical studies is presented to study the effects of inertia and gravity on plug splitting in an airway bifurcation model to simulate the liquid distributions in large airways. The splitting ratio, Rs, is defined as the ratio of the plug volume entering the upper (gravitationally opposed) daughter tube to the lower (gravitationally favored) one. Rs is measured as a function of parent tube Reynolds number, Rep; gravitational orientations for roll angle, ϕ, and pitch angle, γ; parent plug length LP; and the presence of pre-existing plug blockages in downstream daughter tubes. Results show that increasing Rep causes more homogeneous splitting. A critical Reynolds number Rec is found to exist so that when Rep⩽Rec, Rs=0, i.e., no liquid enters the upper daughter tube. Rec increases while Rs decreases with increasing the gravitational effect, i.e., increasing ϕ and γ. When a blockage exists in the lower daughter, Rec is only found at ϕ=60deg in the range of Rep studied, and the resulting total mass ratio can be as high as 6, which also asymptotes to a finite value for different ϕ as Rep increases. Inertia is further demonstrated to cause more homogeneous plug splitting from a comparison study of Rs versus Cap (another characteristic speed) for three liquids: water, glycerin, and LB-400X. A theoretical model based on entrance flow for the plug in the daughters is developed and predicts Rs versus Rep. The frictional pressure drop, as a part of the total pressure drop, is estimated by two fitting parameters and shows a linear relationship with Rep. The theory provides a good prediction on liquid plug splitting and well simulates the liquid distributions in the large airways of human lungs.

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Dini-Papanastasi, O., P. Kostopoulou, and K. Radoglou. "Effects of seed origin, growing medium and mini-plug density on early growth and quality of black locust (Robinia pseudoacacia [L.]) seedlings." Journal of Forest Science 58, No. 1 (January 27, 2012): 8–20. http://dx.doi.org/10.17221/46/2011-jfs.

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The objective of this study was to identify optimal growing conditions for the production of high-quality mini-plug seedlings of black locust (Robinia pseudoacacia [L.].). Two seed origins (Greek and Hungarian), two growing media (enriched peat and stabilized medium) and four mini-plug densities (975; 1,460; 1,820 and 3,500 mini-plugs·m–2) were tested in two phases, in growth chambers and in a nursery after transplanting the mini-plugs into larger containers. Measurements included seedling survival, growth traits (root length, shoot height, leaf area, root dry mass, shoot dry mass, root/shoot ratio) and root growth potential (RGP). In addition, the ratio of variable to maximal fluorescence (Fv/Fm) and the effective quantum yield of photosystem II (ΔF/F’m) were measured. It was found that growing medium produced significant effects mainly in the first phase and seed origin in the second phase while mini-plug density was important in both phases. The Fv/Fm ratio was found to be significantly affected by growing medium while the effective quantum yield was influenced by density. Early survival of seedlings was closely correlated with fluorescence and growth traits (particularly with plant height) suggesting that these parameters might be useful for the grading of black locust seedlings prior to transplanting.

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Dissertations / Theses on the topic "Plug length ratio"

Forni, Fabio. "Investigating the axial response of pile foundations for offshore wind turbines." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.

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I crescenti problemi legati ai cambiamenti climatici rendono l'impiego delle energie rinnovabili sempre più interessante. In questa ottica, in Germania si sta pianificando di aumentare la produzione di energia pulita attraverso lo sfruttamento dell’energia eolica. Nuovi impianti di turbine eoliche sono previsti nel Mare del Nord in acque medio profonde (25-45m) dove la parte immersa della struttura della turbina eolica (chiamata sottostruttura) è spesso costituita da una struttura jacket (traliccio) o tripod (a treppiedi). Questo tipo di sottostrutture trasmettono principalmente carichi assiali alle fondazioni (in genere fondazioni su palo), e il carico a trazione è la forza che maggiormente ne influenza il dimensionamento. Molte compagnie energetiche tedesche sono interessate a migliorare l’efficienza e i costi dei loro impianti eolici e, per questo, incaricano università ed istituti di ricerca (come il Fraunhofer IWES) per indagarne gli aspetti, come ad esempio il comportamento delle fondazioni offshore. All’autore di questa tesi è stata data l’opportunità di studiare e lavorare al Fraunhofer IWES e perciò questa tesi tratterà del compramento di pali caricati assialmente e staticamente pensati per sottostrutture jacket o tripod per turbine eoliche. Nello studio effettuato per questa tesi, i dati seprimentali, ottenuti da una campagna sperimentale condotta (in larga scala 1:10 1:5) su pali infissi in terreno sabbioso, sono confrontati attraverso l’impiego delle load-transfer curves (funzioni che descrivono il comportamento d’interfaccia palosuolo) usando sia un’approccio classico (fornito dal metodo di calcolo API Main Text) sia approcci più recenti (dati dai metodi di calcolo CPT). Uno script Matlab creato appositamente dall’autore di questa tesi riesce ad implementare 11 diversi tipi di load-transfer curves. Il lavoro di tesi si conclude con un esempio pratico in grado di fornire un’idea di come questo script può essere usato nella progettazione.

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Book chapters on the topic "Plug length ratio"

"Hockett TABLE 4 Broad and Narrow Sense Heritability and Genetic Advance Estimates for Grain Yield Components and Other Agronomic Characteristics Since 1964 Heritability" Broad sense Narrow sense Genetic advanceb Number Number Number Average Range references Average Range references Average Range references Characteristic (%) (%) reviewed (%) (%) reviewed (%) (%) reviewed Grain yield 44 5-93 26 27 0-54 11 23 3-46 10 Spike number 49 3-98 24 34 14-66 9 33 4-113 12 Kernels/spike 64 15-99 23 39 2-91 12 28 3-71 8 Kernel weight 63 24-99 22 43 13-78 10 12 2-22 9 Heading date 74 19-100 17 60 34-92 6 10 1-23 9 Lodging score 66 41-88 5 27 6-38 3 123 1 Plant height 66 4-99 30 41 8-73 13 15 1-44 11 Grain protein 53 5-98 14 32 8-76 4 16 5-22 3 Grain plumpness 62 34-90 5 43 24-58 3 18 11-24 2 Diastatic power Barley 82 55-94 5 58 23-94 3 20 Malt 68 50-86 2 Extract Barley 59 43-71 3 12 8-16 211 Malt 57 46-69 3 Spike length 66 3-98 17 50 44-56 5 20 4-34 8 'Computations were most often on the plot basis, but some were on a plant or trial mean basis. 'Given as percentage of the mean. Source: Ref. 15. barley [41] and have been used to produce homozygous sp. spontaneum and bulbosum have about 3000 and 600 lines and study segregation ratios and linkage values in ga-ascensions, respectively [46,47]. The locations of the ma-metes produced by F1 plants (haploids); produce aneu-jor base germplasm collections are shown in Table 5. ploids (triploids); and attempt to produce commercial, 2n = Working germplasm collections are found in Brazil, Bul-4x = 28 chromosome barleys (autotetraploids). Individual garia, the Czech Republic, England, Germany, Slovakia, pairs of barley chromosomes have been added to the chro-Syria, the Netherlands, the United States, and Russia [48]. mosome complement of wheat [41] and used to make ge-Many composite crosses of barley are maintained in the netic and evolutionary studies of barley. Figure 8 shows a United States, with CCXLVII being the last one assigned a micrograph of barley chromosomes. number by the USDA-ARS collection [49]. A new strategy to physically relate RFLP-based genetic Recent attempts have been made to set up "core" col-linkage maps with cytological markers of the barley chro-lections of barley germplasm [50,51]. Selection of these mosomes has been devised by Sorokin et al. [44]. Morpho-genotypes can be divided into four steps: (1) definition of logically distinct translocation chromosome were mi-domain, (2) division into genetically distinct types, (3) al-croisolated, and their DNA was used as a template for location of entries over types, and (4) choice of entries polymerase chain reaction with sequence-specific primers. [51]. Cross [50] has integrated both simply inherited phe-A recent review of these techniques in cereals is given by notypically obvious markers with electrophoretic patterns Kunzel and Korzun [45]. in setting up a core collection. D. Germplasm Resources 2. Wide Crosses Reviews describing the wide crosses made in barley are 1. Collections given by von Bothmer [47,52] and Fedak [53,54]. The ori-About 25,000 barley landraces plus 25,000 breeder lines gin, taxonomy, and related species of barley are described and cultivars are preserved in collections of barley [52], as are the incompatibility, mechanisms, and cytoge-throughout the world [46]. In addition, the wild H. vulgare netics of wild barley crosses [53]. There is a general lack." In Handbook of Cereal Science and Technology, Revised and Expanded, 104–10. CRC Press, 2000. http://dx.doi.org/10.1201/9781420027228-12.

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Conference papers on the topic "Plug length ratio"

Kim, Namwon, Michael C. Murphy, Steven A. Soper, and Dimitris E. Nikitopoulos. "Liquid-Liquid Segmented Flows in Polymer Microfluidic Channels." In ASME 2009 7th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2009. http://dx.doi.org/10.1115/icnmm2009-82277.

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Liquid-liquid segmented flows in microchannels fabricated on polymer test chips were investigated experimentally. Polymer test chips were prepared using hot embossing of polycarbonate (PC) sheets with micro-milled brass mold inserts. Three different configurations of microchannels were prepared with injection to test channels expansion ratios of 16, 4 and 2 and a fixed test channel geometry. Deionized water with blue food-coloring dye (1% v/v) was used as a dispersed fluid at flow rates (QD) between 0.5 and 60 μl/min. The carrier fluid was perfluorocarbon (FC 3283) with nonionic fluorous-soluble surfactant (Perfluorooctanol, 10% v/v) at flow rates (QC) between 3 and 25 μl/min. The two fluids were injected separately into the chips. Droplet and Plug flows with transient Irregular Segmented flows between two flow regimes were mainly observed in the test channels of the three different chips. Flow pattern maps and transitions between flow regimes were determined in terms of a fixed homogeneous carrier fluid volumetric flow ratio (βC) to compare the effect of the expansion ratios from the injection to the test channels. The droplet and plug regimes were shifted to higher carrier and lower dispersed fluid superficial velocities and the plug flow regime was broader with the lower expansion ratio channels. The transient irregular segmented flow was favored in the higher expansion channel ratio and the interval of transient irregular segmented flow between droplet and plug flow regimes were shorter for the low expansion channel ratios. This is evidence that flow regime maps in micro-channels are not universal and depend on the configuration part of the micro-injection system. The length of the dispersed segmented flows and the distance between consecutive droplets or plugs as a function of βC were determined by image processing of frames acquired via CCD camera with bright field illumination. The average length of the dispersed fluid was shown to scale approximately with βC to the −1.2 power. Velocities of the dispersed droplet and plug flows were measured using double-pulsed laser illumination and were found to be 1.25 ± 0.049 and 1.46 ± 0.077 times faster than the superficial velocity of the segmented flow respectively. Two-phase pressure drop measurements were also carried out for all flow regimes and associated trends were correlated with changes in flow topology. Comparisons of experimental pressure drop with the predictions for a modified Lockhart-Martinelli correlation were also made.

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Botros, K. K., M. J. de Boer, G. R. Price, and G. Kibrya. "One-Dimensional Predictive Emission Monitoring Model for Gas Turbine Combustors." In ASME 1997 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-gt-414.

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Current predictive emission monitoring (PEM) techniques are briefly reviewed and the concept for a general predictive model was favorably evaluated. Utilizing the commercial process simulation software ASPEN PLUS®, a one dimensional model based on fundamental principles of gas turbine thermodynamics and combustion processes was constructed. Employing a set of 22 reactions including the Zeldovich mechanism, the model predicted for thermal NOx formation. It accounted for combustor geometry, dilution air injection along the combustor annulus, convective heat transfer across the liner, flame length, and full-load inlet flows. The combustor was subdivided into slices, each of which was modeled by a plug flow reactor, giving insight into profiles of NOx formation, species concentration and temperature along the combustor’s length, as well as quantifying the residence time in the combustor. The simulation predicted the levels of NOx for a particular gas turbine combustor and determined the effects of various parameters, such as flame length, hydrocarbon conversion ratio and recycle zones.

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Chiu, Min-Chie. "Shape Optimization of Multi-Chamber Mufflers With Plug-Inlet Tube on a Venting Process by Genetic Algorithms." In ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-86092.

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Research on new techniques of single-chamber plug-inlet mufflers has been addressed. However, research work on shape optimization of multi-chamber plug-inlet mufflers along with work on the maximal back pressure has been neglected. Therefore, a numerical case for eliminating a broadband steam blow-off noise using multi-chamber plug-inlet mufflers in conjunction with genetic algorithm (GA) as well as numerical decoupling technique under space-constrained pressure drop is introduced in this paper. To verify the liability of GA optimization, optimal noise abatements for various pure tones on a one-chamber plug-inlet muffler are exemplified. Also, the accuracy of the mathematical model has to be checked by experimental data. Results indicate that the maximal sound transmission losses are precisely located at the desired target tones. Consequently, both the pressure drop and the acoustical performance will be increased when the diameters (at inlet tubes and perforated holes), the perforated ratio, and the length of perforated tube decrease.

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Srinivasan, Vyas, Basant Singh Sikarwar, and Sameer Khandekar. "Experimental and Simulation Study on Motion of an Isolated Liquid Plug Inside a Dry Circular Capillary." In ASME 2013 4th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/mnhmt2013-22064.

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Classical study of motion of a single liquid plug (water) inside a micro/mini capillary tube is revisited to understand the contribution of meniscus friction and effect of contact angle hysteresis on the pressure required to initiate the motion of liquid plug of different L/D ratio. Experiments are carried out by injecting a known mass flow rate of air to push the liquid plug from rest. While the plug is at rest, as the air pressure increases linearly, the menisci deform till a limiting value, at which the plug starts moving. The initial phase of plug motion is dominated by its acceleration, which is then opposed by wall shear, and eventually leads to a steady motion of liquid plug at constant pressure and dynamic contact angle hysteresis. Experimental results show that, the pressure required to initiate the motion of the liquid is independent of its length, indicating the dominance of static menisci friction at initial stages. Also, steady state pressure drop is observed to be much greater than that predicted by fully developed tube flow. The flow is simulated in COMSOL using level set method. Simulation results agree well with the experimental result. Contribution of menisci towards static and dynamic friction and velocity development near menisci are obtained from simulations to model the friction factor for the flow.

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Muzychka, Y. S. "Laminar Heat Transfer for Gas-Liquid Segmented Flows in Circular and Non-Circular Ducts With Constant Wall Temperature." In ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icnmm2014-21087.

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A new model is developed for gas-liquid segmented flows in ducts and channels. This model is an improvement of an earlier analysis presented and published by the author. In the present work, it is shown that for constant wall temperature, the dimensionless mean wall flux has two characteristic behaviours: thermal boundary layer flow and fully developed flow. These can also be viewed as short and long residence times as the plug train moves through the tube or channel. The boundary layer limit is dominant for short residence times while fully developed flow occurs for longer residence times. An additional parameter, the plug length to duct length ratio, (Ls/L), is shown to have significant impact on the rate of heat transfer. This parameter has the limits 0 < Ls/L < 1. The new model is compared with data from several published studies in which the variables were well controlled. It is also shown that careful experiments must be undertaken to demonstrate the characteristics of this type of flow under constant wall temperature conditions.

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Kim, Namwon, Estelle T. Evans, Steven A. Soper, Michael C. Murphy, and Dimitris E. Nikitopoulos. "Investigation of Two-Phase Flow in Rectangular Micro-Channels." In ASME 2008 Fluids Engineering Division Summer Meeting collocated with the Heat Transfer, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/fedsm2008-55037.

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This study addresses air-water, two-phase flows in micro-channels fabricated on poly-methyl-methacrylate (PMMA) with walls that are partially non-wetting (typical static contact angle 65° in stock form) and not molecularly smooth. Two different types of chips were prepared: Micro-milled micro-channels of aspect ratios 1, 2 and 3 with fixed hydraulic diameter on PMMA and micro-channels of unity aspect ratio replicated using hot embossing of PMMA with a micro-milled brass mold insert. Flow-maps obtained using the same gas-liquid injection geometry and method for the three aspect ratio micro-channels are presented, and regime boundaries are compared with those found by other investigations. The results indicate that the bubbly flow regime boundary is shifted to higher liquid and/or lower gas superficial velocities for the higher aspect ratio channels, while transition to the Annular and Annular-Dry regimes remains the same to within experimental uncertainty. The emphasis of what is presented is on the Segmented flow regime. Regular and irregular Segmented flow regimes of three types are assessed on the basis of the statistical variation in the associated phase length scales from flow observations over a substantial channel length. Comparison between results of the two different injection geometries and micro-channel manufacturing techniques indicate that feedback effects are a significant but not the only cause of segmented flow irregularity. The variability in the size of the liquid plug separating gas bubbles in Segmented flow is found to be substantially higher than that of the bubbles even when the flow is regular (low variability of bubble size). The average bubble length associated with a part of Segmented flows, regular and irregular alike is shown to scale approximately with the capillary number to the 2/3 power (liquid volumetric flow ratio to the −2/3). Irregular Segmented flow is favored by higher liquid superficial velocities, lower liquid volumetric flow ratios and lower channel aspect ratios. Of the three aspect ratios examined, the microchannel with aspect-ratio 3 displayed the broadest window of regular Segmented flow. Two-phase flow pressure drop was measured for test channels of unity aspect ratio. Each flow regime identified on the basis of topological observations is associated with different trends of the pressure drop variation with respect to volumetric flow ratio.

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Ohtake, Hiroyasu, Hideyasu Ohtaki, Masato Hagiwara, and Yasuo Koizumi. "Experimental and Analytical Studies on Frictional Pressure Drops of Gas-Liquid Two-Phase Flow in Mini-Micro Pipes and at Vena Contract and Expansion." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-44006.

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The frictional pressure drops of gas-liquid two-phase flow in mini-micro pipes and at vena contract and expansion were investigated experimentally and analytically. Pressure drops of straight pipe, sudden enlargement and sudden contraction of gas-liquid two-phase flow in mini-pipes were measured. Test liquid was water at room temperature; test gas was argon. The diameter of the test mini-pipe was 0.5, 0.25 and 0.12 mm, respectively; the length was 500, 250 and 50 mm, respectively. The cross-sectional ratio of the contraction was about 1000; the ratio of the enlargement was about 0.001. The pressure drop data and the flow pattern were collected over 3.0 < UG < 130 m/s for the superficial gas velocity and 0.02 < UL < 6.0 m/s for the superficial liquid velocity. The two-phase friction multiplier data for D > 0.5 mm showed to be in good agreement with the conventional correlations. On the other hand, the two-phase friction multiplier data for D < 0.25 mm differed from the calculated values by the conventional correlations. Then, thickness of liquid film around a gas plug and size of gas core were estimated and the effect of frictional pressure drop on channel size was discussed through Knudsen Number of gas and instability on liquid-gas interface. Namely, the effect of mini-pipe was rarefaction effects, Kn<0.1. New correlation of frictional pressure drop of gas-liquid two-phase flow is proposed for mini pipes. The coefficients of sudden enlargement and sudden contraction in mini-pipes for the gas-water two-phase flow were modified from the present experimental results. The experimental results were also examined through numerical simulation by a commercial code.

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Valk, Martin, Nicolas Vortmeyer, and Günter Kappler. "NOx Emission Characteristics of a Catalytic Combustor Under High-Temperature Conditions." In ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-164.

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A catalytic combustor concept with short catalyst segments and a thermal reactor is investigated with regard to NOx production of this concept under high-temperature conditions. The maximum combustor exit temperature was more than 1800 K with catalyst temperatures below 1300 K. For combustion of iso-octane, NOx emissions of 4 ppm (dry, 15% O2) at a flame temperature of 1800 K were measured. No significant influence of catalyst length, reference velocity and overall residence time on NOx emissions was observed. Additionally, the test combustor was fuelled with commercial diesel and kerosene (Jet-A). In this case, NOx emissions were noticeable higher due to fuel-bound nitrogen. The emissions measured were for diesel, 12 ppm, and for kerosene, 7 ppm, (each dry, 15% O2), again at a flame temperature of 1800 K. To evaluate the conversion ratio of fuel-bound nitrogen to NOx iso-octane was doped with various amounts of ammonia and metyhlamine. The conversion rates were 70 to 90%, with a slight tendency to lower values (50%) for nitrogen mass fractions above 0.1%. Considering the NOx emission level of actual premix burners, the lower emission value of the presented catalytic combustor results from a perfect premixed plug-flow combustion system incorporating a catalyst herein and not from a specific advantage of the principle of catalytic combustion itself. Again similar to a premix-combustor are the NOx emission characteristics in the case of lean combustion of nitrogen bound fuels, which yield very high conversion rates.

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Willems, Hilde, and Roger Sierens. "Modeling the Initial Growth of the Plasma and Flame Kernel in S.I. Engines." In ASME 2001 Internal Combustion Engine Division Spring Technical Conference. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/ices2001-114.

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Abstract The initial size and growth of the plasma and flame kernel just after spark discharge in S.I. engines determines if the flame becomes self-sustainable or extinguishes. On the other hand the development of the kernel during the initial phases has non-negligible influences on the further combustion. For example cyclic variations often find their origin in the beginning of combustion and determine the working limits of the engine and the driving behavior of the vehicle. These factors demonstrate the crucial importance of the knowledge of the initial growth of the plasma and flame kernel in S.I. engines. A complete model is developed for the growth of the initial plasma and flame kernel in S.I. engines, which takes into account the fundamental properties of the ignition system (electrical energy and power, geometry of the spark plug, heat losses to the electrodes and the cylinder wall), the combustible mixture (pressure, temperature, equivalence ratio, fraction of residual gasses, kind of fuel) and the flow (average flow velocity, turbulence intensity, stretch, characteristic time and length scales). The proposed model distinguishes three phases: the prebreakdown, the plasma and the initial combustion phase. The model of the first two phases is proposed in a previous article of the same authors (Willems and Sierens, 1999), the latter is exposed in this article. A thermodynamic model based on flamelet models and which takes stretch into account, is used to describe the initial combustion phase. The difference between heat losses to the electrodes and the cylinder wall is considered. The burning velocity varies from the order of the laminar velocity to the fully developed burning velocity. The evolution is determined as well by the life time as by the size of the kernel. The stretch (caused by turbulence and by the growth of the kernel), the non-adiabatic character of the flame and instabilities have influence on the laminar burning velocity. Validation of this model is done using measurements of the expansion in a propane-air mixture executed by Pischinger at M.I.T. The correspondence seems to be very well.

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Manikantachari, K. R. V., Scott Martin, Ladislav Vesely, Jose O. Bobren-Diaz, Subith Vasu, and Jayanta Kapat. "A Strategy of Reactant Mixing in Methane Direct-Fired sCO2 Combustors." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75547.

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The sCO2 power cycle concept is identified as a potentially efficient, economical, and pollutant free power generation technique for future power generation. Recent work in the literature provides some strategies and best operating conditions for direct-fired sCO2 combustors based on zero-dimensional reactor modeling analysis, however there is a need for a detailed investigation using accurate combustion chemical kinetics and thermophysical models. Here, the sCO2 combustor is modelled by coupling perfectly stirred reactor (PSR) and plug flow reactor (PFR) models. The real gas effects are incorporated using the Soave-Redlich-Kwong (SRK) equation of state. Also, the detailed Aramco 2.0 kinetic mechanism is used for the combustion kinetic rates. It is found that the primary zone must be diluted either with thirty or forty-five percent of the total CO2 in the cycle to have a feasible combustor design. However, the forty-five percent dilution level at 950 K and 1000 K yielded a better consumption of CO, O2 and CH4. Also, the cross-sectional area of the sCO2 combustor can be scaled-down to 10 to 20 times smaller than a traditional combustor with the same power output. Further, from this investigation, it is also recommended to have a gradually increasing secondary dilution in the dilution zone, by using progressively larger diameter holes. This design would help retain relatively high temperature in the initial portion of the dilution zone and would help consume fuel species such as, CO and CH4. It appears that, for sCO2 combustors “lean burn” is the better strategy over stoichiometric burning to eliminate CO build up at the combustor exit. The lean burn condition at equivalence ratio (ϕ) equal to 0.9 is recommended for sCO2 combustor operation. Also, the length of the dilution zone can be scaled-down to 50% by lean burn operation of the combustor. It is also observed that the lean burn increases the net turbine power. Current work provides crucial design considerations for the development of advanced sCO2 combustors to be used with direct-fired power cycles.

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