Journal articles: 'Film Blowing'

1

Liu, C. C., D. C. Bogue, and J. E. Spruiell. "Tubular Film Blowing." International Polymer Processing 10, no. 3 (September 1995): 226–29. http://dx.doi.org/10.3139/217.950226.

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Liu, C. C., D. C. Bogue, and J. E. Spruiell. "Tubular Film Blowing." International Polymer Processing 10, no. 3 (September 1995): 230–36. http://dx.doi.org/10.3139/217.950230.

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3

Pinheiro, I. M. R. "NONISOTHERMAL NEWTONIAN FILM BLOWING." Mathematical Modelling and Analysis 10, no. 3 (September 30, 2005): 305–18. http://dx.doi.org/10.3846/13926292.2005.9637289.

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In this paper, we refine Han and Park results for nonisothermal film blowing: we propose a correction in their temperature and force balance equations, and prove that with this change the actual system should be split into three other systems, and use a different scaling supposedly more suitable to find the solution of the equations. Besides all that, we also provide an analysis on how our nonisothermal model could improve modeling of the film blowing process. It is worth mentioning that, even though we have corrected (mathematically) the force balance equation by Han and Park, we only make use of the first version of the split model in our simulations to match the other simulations done with the model so far. Future work will include further refinements on the simulations. Šiame straipsnyje tobulinami Hano ir Parko rezultatai apie neizotermini filmo juostos pūtima. Autoriai patikslina temperatūros ir jegu balanso lygtis ir irodo, kad tai išskaido lygčiu sistema i tris sistemas. Tai igalina rasti uždavinio sprendini. Taip pat pateikta analize kaip šis modelis, gali patobulinti pūtimo procesa. Kadangi naudojamas pataisytas Hano ir Parko modelis, todel modeliuojant gauti rezultatai ne visuomet sutampa su kitu eksperimentu rezultatais. Ateityje numatoma tobulinti šiuos eksperimentus.

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4

Greener, J., and J. R. G. Evans. "Film blowing of ceramics." Journal of Materials Science 28, no. 22 (November 1993): 6190–94. http://dx.doi.org/10.1007/bf00365042.

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Pak, A. Ram, Jung Hyun Park, and Seung Geol Lee. "Blowing Properties and Functionality of Thermoplastic Polyester Film Using Thermally Expandable Microcapsules." Polymers 11, no. 10 (October 11, 2019): 1652. http://dx.doi.org/10.3390/polym11101652.

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Blowing film was prepared using a polyester elastomer with thermally expandable microcapsules to investigate its blowing properties and functionality. Film with 11% microcapsule contents showed the lowest specific gravity and the highest blowing efficiency. However, the collapse and merging of blowing cells with 11% microcapsule contents was found by SEM. Therefore, film with 9% microcapsule contents was shown to have better blowing and cell stability than that of film with 11% microcapsule contents. Tensile strength and elongation decreased by increasing microcapsule contents. Film curl and film shrinkage properties were unaffected by microcapsule contents. Water vapor permeability and hydrostatic pressure was decreased by increasing microcapsule contents.

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Jiang, Yuanping, Cong Yan, Kai Wang, Dawei Shi, Zhengying Liu, and Mingbo Yang. "Super-Toughed PLA Blown Film with Enhanced Gas Barrier Property Available for Packaging and Agricultural Applications." Materials 12, no. 10 (May 22, 2019): 1663. http://dx.doi.org/10.3390/ma12101663.

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Polylactic acid (PLA) holds enormous potential as an alternative to the ubiquitous petroleum-based plastics to be used in packaging film and agricultural film. However, the poor viscoelastic behavior and its extremely low melt strength means it fails to meet the requirements in film blowing processing, which is the most efficient film processing method with the lowest costs. Also, the PLA’s brittleness and insufficient gas barrier properties also seriously limit PLA’s potential application as a common film material. Herein, special stereocomplex (SC) networks were introduced to improve the melt strength and film blowing stability of PLA; polyethylene glycol (PEG) was introduced to improve PLA’s toughness and gas barrier properties. Compared with neat poly(l-lactide) acid (PLLA), modified PLA is stable in the film blowing process and its film elongation at break increases more than 18 times and reaches over 250%, and its O2 permeability coefficient decreased by 61%. The resulting film material also has good light transmittance, which has great potential for green packaging applications, such as disposable packaging and agricultural films.

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Sikora, Janusz W., Łukasz Majewski, and Andrzej Puszka. "Modern Biodegradable Plastics—Processing and Properties Part II." Materials 14, no. 10 (May 12, 2021): 2523. http://dx.doi.org/10.3390/ma14102523.

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Four different plastics were tested: potato starch based plastic (TPS-P)–BIOPLAST GF 106/02; corn starch based plastic (TPS-C)–BioComp BF 01HP; polylactic acid (polylactide) plastic (PLA)—BioComp BF 7210 and low density polyethylene, trade name Malen E FABS 23-D022; as a petrochemical reference sample. Using the blown film extrusion method and various screw rotational speeds, films were obtained and tested, as a result of which the following were determined: breaking stress, strain at break, static and dynamic friction coefficient of film in longitudinal and transverse direction, puncture resistance and strain at break, color, brightness and gloss of film, surface roughness, barrier properties and microstructure. The biodegradable plastics tested are characterized by comparable or even better mechanical strength than petrochemical polyethylene for the range of film blowing processing parameters used here. The effect of the screw rotational speed on the mechanical characteristics of the films obtained was also demonstrated. With the increase in the screw rotational speed, the decrease of barrier properties was also observed. No correlation between roughness and permeability of gases and water vapor was shown. It was indicated that biodegradable plastics might be competitive for conventional petrochemical materials used in film blowing niche applications where cost, recyclability, optical and water vapor barrier properties are not critical.

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Mapleston, Peter. "Blowing Hot and Cold: Advances in Blown-Film Technology." Plastics Engineering 64, no. 8 (September 2008): 10–18. http://dx.doi.org/10.1002/j.1941-9635.2008.tb00360.x.

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Mistretta, Maria Chiara, Luigi Botta, Rossella Arrigo, Francesco Leto, Giulio Malucelli, and Francesco Paolo La Mantia. "Bionanocomposite Blown Films: Insights on the Rheological and Mechanical Behavior." Polymers 13, no. 7 (April 5, 2021): 1167. http://dx.doi.org/10.3390/polym13071167.

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In this work, bionanocomposites based on two different types of biopolymers belonging to the MaterBi® family and containing two kinds of modified nanoclays were compounded in a twin-screw extruder and then subjected to a film blowing process, aiming at obtaining sustainable films potentially suitable for packaging applications. The preliminary characterization of the extruded bionanocomposites allowed establishing some correlations between the obtained morphology and the material rheological and mechanical behavior. More specifically, the morphological analysis showed that, regardless of the type of biopolymeric matrix, a homogeneous nanofiller dispersion was achieved; furthermore, the established biopolymer/nanofiller interactions caused a restrain of the dynamics of the biopolymer chains, thus inducing a significant modification of the material rheological response, which involves the appearance of an apparent yield stress and the amplification of the elastic feature of the viscoelastic behavior. Besides, the rheological characterization under non-isothermal elongational flow revealed a marginal effect of the embedded nanofillers on the biopolymers behavior, thus indicating their suitability for film blowing processing. Additionally, the processing behavior of the bionanocomposites was evaluated and compared to that of similar systems based on a low-density polyethylene matrix: this way, it was possible to identify the most suitable materials for film blowing operations. Finally, the assessment of the mechanical properties of the produced blown films documented the potential exploitation of the selected materials for packaging applications, also at an industrial level.

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10

Sidiropoulos, V., J. J. Tian, and J. Vlachopoulos. "Computer Simulation of Film Blowing." Journal of Plastic Film & Sheeting 12, no. 2 (April 1996): 107–29. http://dx.doi.org/10.1177/875608799601200204.

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11

THUNWALL, M., V. KUTHANOVA, A. BOLDIZAR, and M. RIGDAHL. "Film blowing of thermoplastic starch." Carbohydrate Polymers 71, no. 4 (March 7, 2008): 583–90. http://dx.doi.org/10.1016/j.carbpol.2007.07.001.

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12

Mehendale, A. B., J. C. Han, S. Ou, and C. P. Lee. "Unsteady Wake Over a Linear Turbine Blade Cascade With Air and CO2 Film Injection: Part II—Effect on Film Effectiveness and Heat Transfer Distributions." Journal of Turbomachinery 116, no. 4 (October 1, 1994): 730–37. http://dx.doi.org/10.1115/1.2929466.

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The effect of unsteady wake flow and air (D.R. = 0.97) or CO2 (D.R. = 1.48) film injection on blade film effectiveness and heat transfer distributions was experimentally determined. A spoked wheel type wake generator produced the unsteady wake. Experiments were performed on a five-airfoil linear cascade in a low-speed wind tunnel at the chord Reynolds number of 3 × 105 for the no wake case and at the wake Strouhal numbers of 0.1 and 0.3. A model turbine blade with several rows of film holes on its leading edge, and pressure and suction surfaces ( −0.2<X/C< 0.4) was used. Results show that the blowing ratios of 1.2 and 0.8 provide the best film effectiveness over most of the blade surface for CO2 and air injections, respectively. An increase in the wake Strouhal number causes a decrease in film effectiveness over most of the blade surface for both density ratio injectants and at all blowing ratios. On the pressure surface, CO2 injection provides higher film effectiveness than air injection at the blowing ratio of 1.2; however, this trend is reversed at the blowing ratio of 0.8. On the suction surface, CO2 injection provides higher film effectiveness than air injection at the blowing ratio of 1.2; however, this trend is reversed at the blowing ratio of 0.4. Co2 injection provides lower heat loads than air injection at the blowing ratio of 1.2; however, this trend is reversed at the blowing ratio of 0.4. Heat load ratios under unsteady wake conditions are lower than the no wake case. For an actual gas turbine blade, since the blowing ratios can be greater than 1.2 and the density ratios can be up to 2.0, a higher density ratio coolant may provide lower heat load ratios under unsteady wake conditions.

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Teixeira, P. F., J. A. Covas, M. J. Suarez, I. Angulo, and L. Hilliou. "Film Blowing of PHB-Based Systems for Home Compostable Food Packaging." International Polymer Processing 35, no. 5 (November 1, 2020): 440–47. http://dx.doi.org/10.1515/ipp-2020-350506.

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Abstract One of the routes to minimize the environmental impact of plastics waste is the use of bio-sourced and biodegradable alternatives, particularly for packaging applications. Although Polyhydroxyalkanoates (PHA) are attractive candidates for food packaging, they have poor processability, particularly for extrusion film blowing. Thus, one relatively successful alternative has been blending PHA with a biodegradable polymer. This work proposes film blowing of a co-extruded Poly (hydroxybutyrate) (PHB) layer with a poly butylene adipateco- terephtalate (PBAT) layer to enhance bubble stability, mechanical and barrier properties. Co-extrusion is detailed, together with the different strategies followed to improve adhesion between film layers and the PHB content in the films. Films with thicknesses below 50 micron and elongation at break beyond 500% were consistently produced.

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14

Zhang, Bo, Libing Lin, Naru Zhang, Shuangsong Xue, and Honghu Ji. "Experimental investigation of geometrical effect on flow and heat transfer performance of lamilloy cooling structure." Thermal Science 24, no. 3 Part A (2020): 1835–43. http://dx.doi.org/10.2298/tsci190528071z.

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Effect of film hole diameter to discharge coefficients and film cooling effectiveness of the lamilloy were experimentally investigated at the blowing ratios ranging from 0.6 to 2.5. Generally, the cooling effectiveness on the test surface is increased with the film hole diameters and blowing ratios increasing, and the variation tendency along the streamwise through the centerline of film holes also keeps consistent. In the upstream, all configurations have a relatively lower cooling effectiveness, however, with the flows to the downstream, cooling effectiveness grows gradually, and the peak values of effectiveness appeared periodically, the position matches the film hole positions. Besides, between the film holes, fluctuation exists simultaneously. By comparison, the cooling effectiveness and discharge coefficients are both increased with the blowing ratio with same film hole diameters, Moreover, under the same blowing ratios, the cooling effectiveness and discharge coefficients are getting higher when hole diameters increase.

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15

Liu, Cun-Liang, Dan Zhao, Ying-Ni Zhai, Hui-Ren Zhu, Yi-Hong He, and Zhi-Xiang Zhou. "Investigations on the Film Cooling of Counter-Inclined Film-Hole Row Structures for Turbine Vane Leading Edge." International Journal of Turbo & Jet-Engines 35, no. 3 (July 26, 2018): 291–303. http://dx.doi.org/10.1515/tjj-2016-0047.

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AbstractNumerical simulations have been performed on the film cooling characteristics of counter-inclined structures, which have advantage in manufacturing relative to the usually used parallel-inclined film-hole row structure, on a turbine vane leading edge model. Single row structure and dual-row structure with counter-inclined film holes were applied in the simulation of leading edge film cooling of turbine vane. The effect of jet-interaction between counter-inclined film-hole rows was studied. The distributions of film cooling effectiveness and heat transfer coefficient were obtained at blowing ratios of 1.0 and 2.0. The results of single row structure show that the film cooling performances of counter-inclined film-hole row are not weakened compared to the traditional parallel-inclined film-hole row structure. The film cooling effectiveness of the counter-inclined film-hole row structure decreases with the increase of blowing ratio, while the heat transfer coefficient increases. The jet-interaction in the dual-row film cooling structure has more notable influence on the film cooling effectiveness than the heat transfer coefficient. Compared to the single row case, the interactions between the upstream counter-blowing jets and the downstream jet improve the film coverage performance and reduce the heat transfer intensity of this downstream jet under larger blowing ratio condition.

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16

Li, Shao Hua, Ge Wu, and Ling Zhang. "Numerical Investigation on Leading Edge of Film Cooling Blade with Different Turbulence and Blowing Ratios." Advanced Materials Research 1070-1072 (December 2014): 1731–34. http://dx.doi.org/10.4028/www.scientific.net/amr.1070-1072.1731.

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In order to investigate the influence of cooling efficiency of leading edge of film cooling blade with different turbulence intensity and blowing ratios,which use method of N-S equation,various blowing ratios of 1.0、1.5 and 2.0,various turbulence intensity of 5%、12%、20% and 30%,it simulated temperature field in leading edge of film cooling blade.The results show: cooling efficiency decreased when blowing ratios is increased.When turbulence intensity is 5%、12% and 20%,it obtains maximum cooling efficiency blowing ratios of 1.0.When turbulence intensity is 30%,it obtains maximum cooling efficiency blowing ratios of 1.5. In blowing ratios of 1.0,cooling efficiency decreased when turbulence increased.But in blowing ratios of 1.5 and 2.0,cooling efficiency increased when turbulence increased.

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17

Ou, S., and J. C. Han. "Influence of Mainstream Turbulence on Leading Edge Film Cooling Heat Transfer Through Two Rows of Inclined Film Slots." Journal of Turbomachinery 114, no. 4 (October 1, 1992): 724–33. http://dx.doi.org/10.1115/1.2928025.

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The effect of film slot injection on leading edge heat transfer coefficient and film cooling effectiveness under high mainstream turbulence conditions was experimentally studied for flow across a blunt body with a semicylinder leading edge and a flat afterbody. High mainstream turbulence levels were generated by a bar grid (Tu = 5.07 percent) and a passive grid (Tu = 9.67 percent). The incident mainstream Reynolds number based on the cylinder diameter was about 100,000. The spanwise and streamwise distributions of the heat transfer coefficient and film effectiveness in the leading edge and on the flat sidewall were obtained for three blowing ratios (B = 0.4, 0.8, and 1.2) with two rows of film slots located at ± 15 and ± 40 deg from the stagnation line. The cross-sectional slot length-to-width ratio was two. The slots in each row were spaced three cross-sectional slot lengths apart and were angled 30 and 90 deg to the surface in the spanwise and streamwise directions, respectively. The results show that heat transfer coefficient increases with increasing blowing ratio, but the film effectiveness reaches a maximum at an intermediate blowing ratio of B = 0.8 for both low (Tu = 0.75 percent) and high (Tu = 9.67 percent) mainstream turbulence conditions. The leading edge heat transfer coefficient increases and the film effectiveness decreases with mainstream turbulence level for the low blowing ratio; however, the mainstream turbulence effect decreases for the high blowing ratio. The leading edge heat load is significantly reduced with two rows of film slot injection. The blowing ratio of B = 0.4 provides the lowest heat load In the leading edge region for the low mainstream turbulence, but B = 0.8 gives the lowest heat load for the high mainstream turbulence conditions.

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18

Ou, Shichuan, and J. C. Han. "Leading Edge Film Cooling Heat Transfer Through One Row of Inclined Film Slots and Holes Including Mainstream Turbulence Effects." Journal of Heat Transfer 116, no. 3 (August 1, 1994): 561–69. http://dx.doi.org/10.1115/1.2910907.

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The effects of film opening shape and mainstream turbulence on the leading edge heat transfer coefficient and film effectiveness were experimentally investigated. The experiments were performed using test models with a semi-cylindrical leading edge and a flat afterbody. A bar grid (Tu = 5.07 percent) and a passive grid (Tu = 9.67 percent) produced two levels of mainstream turbulence. Two separate cases of one-row injection through film slots or holes located only at ±15 deg or only at ±40 deg from the stagnation line were studied for three blowing ratios of 0.4, 0.8, and 1.2 at the Reynolds number (ReD) of 100,000. The slots in each row were spaced three cross-sectional slot lengths (P = 3l) apart, while the holes were spaced four holes diameters (P = 4d) apart. Both geometries had equal cross-sectional area and pitch. The results show that the leading edge heat transfer coefficient increases and the film effectiveness decreases with increasing blowing ratio; however, B = 0.8 provides the highest film effectiveness for the film hole with ±40 deg injection. The heat transfer coefficient increases and the film effectiveness decreases with increasing mainstream turbulence level. However, the mainstream turbulence effect on the film effectiveness is reduced as the blowing ratio is increased. Slot geometry provides better film cooling performance than the hole geometry for all test cases at the lowest blowing ratio of 0.4. However, at higher blowing ratios of 0.8 and 1.2, the reverse is true for ±40 deg injection at mainstream turbulence of 0.75 and 9.67 percent.

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19

Kazemi Kelishami, Mojtaba, and Esmail Lakzian. "Optimization of the blowing ratio for film cooling on a flat plate." International Journal of Numerical Methods for Heat & Fluid Flow 27, no. 1 (January 3, 2017): 104–19. http://dx.doi.org/10.1108/hff-07-2015-0284.

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Purpose The purpose of this paper is to report the result of a numerical investigation of film cooling performance on a flat plate for finding optimum blowing ratios. Design/methodology/approach Steady-state simulations have been performed, and the flow has been considered incompressible. Calculations have been performed with 3D finite-volume method and the k-e turbulence model. Findings The adiabatic film cooling effectiveness and the effects of density ratio (DR), blowing ratio (M) and main stream turbulence intensity (Tu), coolant penetration, hole incline and diameter are studied. The temperature and film cooling effectiveness contours, centerline and laterally film cooling effectiveness are presented for these cases. Results show that the cases with smaller Tu have better effectiveness. In the console, using the air coolant and in cylindrical hole cases, using CO2 coolant fluid has higher effectiveness. The results indicated that there is an optimum blowing ratio in the cylindrical hole cases to optimize the performance of new gas turbines. Research limitations/implications Investigation of optimum blowing ratio for the convex surfaces and turbine blades is a prospective topic for future studies. Practical implications The motivation of this study comes from several industrial applications such as film cooling of gas turbine components. This research gives the best blowing ratio for receiving maximum cooling effectiveness with minimum coolant velocity. Originality/value This study optimizes the blowing ratio for film cooling on a flat plate.

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Scaffaro, Roberto, Fiorenza Sutera, and Luigi Botta. "Biopolymeric bilayer films produced by co-extrusion film blowing." Polymer Testing 65 (February 2018): 35–43. http://dx.doi.org/10.1016/j.polymertesting.2017.11.010.

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21

SHINOHARA, Masayuki, Toshihisa KAJIWARA, and Kazumori FUNATSU. "Viscoelastic Analysis of Tubular Film Blowing." Seikei-Kakou 9, no. 3 (1997): 238–44. http://dx.doi.org/10.4325/seikeikakou.9.238.

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22

Dirama, Taner, and Lloyd Goettler. "Film Blowing of Layered Silicate Nanocomposites." Materials and Manufacturing Processes 21, no. 2 (April 1, 2006): 199–210. http://dx.doi.org/10.1081/amp-200068675.

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23

Cain, John J., and Morton M. Denn. "Multiplicities and instabilities in film blowing." Polymer Engineering and Science 28, no. 23 (December 1988): 1527–41. http://dx.doi.org/10.1002/pen.760282303.

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24

Luo, X.-L., and R. I. Tanner. "A computer study of film blowing." Polymer Engineering and Science 25, no. 10 (July 1985): 620–29. http://dx.doi.org/10.1002/pen.760251008.

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25

Ghaneh-Fard, A., P. J. Carreau, and P. G. Lafleur. "Study of instabilities in film blowing." AIChE Journal 42, no. 5 (May 1996): 1388–96. http://dx.doi.org/10.1002/aic.690420519.

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Dintcheva, Nadka Tzankova. "Film blowing of silane-modified polyethylene." Journal of Applied Polymer Science 114, no. 1 (October 5, 2009): 503–8. http://dx.doi.org/10.1002/app.30512.

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Williams, H. M., J. R. G. Evans, J. E. Shemilt, and M. J. Edirisinghe. "Film Blowing of Ceria Electrolyte Plates." Materials and Manufacturing Processes 13, no. 1 (January 1998): 147–58. http://dx.doi.org/10.1080/10426919808935225.

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Chen, Ping-Hei, Min-Sheng Hung, and Pei-Pei Ding. "A Transient Method Using Liquid Crystal for Film Cooling Over a Convex surface." International Journal of Rotating Machinery 7, no. 3 (2001): 153–64. http://dx.doi.org/10.1155/s1023621x01000148.

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In order to explore the effect of blowing ratio on film cooling over a convex surface, the present study adopts the transient liquid crystal thermography for the film cooling measurement on a straight circular hole configuration. The test piece has a strength of curvature(2r/D)of 92.5, pitch to diameter ratio(P/D)of 3 and streamwise injection angle(γ)of35∘All measurements were conducted under the mainstream Reynolds number(Red)of 1700 with turbulence intensity(Tu)of 3.8%, and the density ratio between coolant and mainstream(ρc/ρm)is 0.98. In current study, the effect of blowing ratio(M)on film cooling performance is investigated by varying the range of blowing ratio from 0.5 to 2.0. Two transient tests of different injection flow temperature were conducted to obtain both detailed heat transfer coefficient and film cooling effectiveness distributions of measured region. The present measured results show that both the spanwise averaged heat transfer coefficient and film cooling effectiveness increase with decreased blowing ratio.

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Bin Pairan, Mohamad Rasidi, Norzelawati Binti Asmuin, and Hamidon bin Salleh. "Simulation Film Cooling in the Leading Edge Region of a Turbine Blade (Trench Effect on Film Effectiveness from Cylinder in Crossflow)." Applied Mechanics and Materials 554 (June 2014): 317–21. http://dx.doi.org/10.4028/www.scientific.net/amm.554.317.

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Film cooling is one of the cooling techniques applied to the turbine blade. Gas turbine used film cooling technique to protect turbine blade from directly expose to the hot gas to avoid the blade from defect. The focus of this investigation is to investigate the effect of embedded three difference depth of trench at coolant holes geometry. Comparisons are made at four difference blowing ratios which are 1.0, 1.25 and 1.5. Three configuration leading edge with depth Case A (0.0125D), Case B (0.0350D) and Case C (0.713D) were compared to leading edge without trench. Result shows that as blowing ratio increased from 1.0 to 1.25, the film cooling effectiveness is increase for leading edge without trench and also for all cases. However when the blowing ratio is increase to 1.5, film cooling effectiveness is decrease for all cases. Overall the Case B with blowing ratio 1.25 has the best film cooling effectiveness with significant improvement compared to leading edge without trench and with trench Case A and Case C.

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Abdala, Antar M. M., Fifi N. M. Elwekeel, and Qun Zheng. "Film Cooling Adiabatic Effectiveness for Cylindrical Holes Embedded in Multi Trench Configuration." Advanced Materials Research 588-589 (November 2012): 1866–69. http://dx.doi.org/10.4028/www.scientific.net/amr.588-589.1866.

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In this study, computational simulations were made using ANSYS CFX to predict the improvements in film cooling performance with multi trench. Multi-trench configuration consists of two trenches together, one wider trench and the other is narrow trench that extruded from the wider one. Several blowing ratios in the range (0.5, 1, 2 and 3) were investigated. By using the multi trench configuration, the coolant jet impacted the trench wall two times allowing increasing the spreading of coolant laterally in the trench, reducing jet velocity and jet completely covered on the surface. The results indicate that this configuration increased adiabatic effectiveness as blowing ratio increased. The multi trench configuration increased adiabatic effectiveness up to 100% near the hole, 43% at X/D = 40 and 31% at downstream X/D = 137 for blowing ratio of 3 and no observed film blow-off at this blowing ratio. The adiabatic film effectiveness of multi trench configuration outperformed the narrow trench at different blowing ratios

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Ekkad, S. V., J. C. Han, and H. Du. "Detailed Film Cooling Measurements on a Cylindrical Leading Edge Model: Effect of Free-Stream Turbulence and Coolant Density." Journal of Turbomachinery 120, no. 4 (October 1, 1998): 799–807. http://dx.doi.org/10.1115/1.2841792.

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Detailed heat transfer coefficient and film effectiveness distributions are presented on a cylindrical leading edge model using a transient liquid crystal technique. Tests were done in a low-speed wind tunnel on a cylindrical model in a crossflow with two rows of injection holes. Mainstream Reynolds number based on the cylinder diameter was 100,900. The two rows of injection holes were located at ±15 deg from stagnation. The film holes were spaced four hole diameters apart and were angled 30 and 90 deg to the surface in the spanwise and streamwise directions, respectively. Heat transfer coefficient and film effectiveness distributions are presented on only one side of the front half of the cylinder. The cylinder surface is coated with a thin layer of thermochromic liquid crystals and a transient test is run to obtain the heat transfer coefficients and film effectiveness. Air and CO2 were used as coolant to simulate coolant-to-mainstream density ratio effect. The effect of coolant blowing ratio was studied for blowing ratios of 0.4, 0.8, and 1.2. Results show that Nusselt numbers downstream of injection increase with an increase in blowing ratio for both coolants. Air provides highest effectiveness at blowing ratio of 0.4 and CO2 provides highest effectiveness at a blowing ratio of 0.8. Higher density coolant (CO2) provides lower Nusselt numbers at all blowing ratios compared to lower density coolant (air). An increase in free-stream turbulence has very small effect on Nusselt numbers for both coolants. However, an increase in free-stream turbulence reduces film effectiveness significantly at low blowing ratios for both coolants.

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Mehendale, A. B., and J. C. Han. "Influence of High Mainstream Turbulence on Leading Edge Film Cooling Heat Transfer." Journal of Turbomachinery 114, no. 4 (October 1, 1992): 707–15. http://dx.doi.org/10.1115/1.2928023.

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The influence of high mainstream turbulence on leading edge film effectiveness and heat transfer coefficient was studied. High mainstream turbulence was produced by a passive grid and a jet grid. Experiments were performed using a blunt body with a semicylinder leading edge with a flat afterbody. The mainstream Reynolds number based on leading edge diameter was about 100,000. Spanwise and streamwise distributions of film effectiveness and heat transfer coefficient in the leading edge and on the flat sidewall were obtained for three blowing ratios, through rows of holes located at ±15 and ±40 deg from stagnation. The holes in each row were spaced three hole diameters apart and were angled 30 and 90 deg to the surface in the spanwise and streamwise directions, respectively. The results indicate that the film effectiveness decreases with increasing blowing ratio, but the reverse is true for the heat transfer coefficient. The leading edge film effectiveness for low blowing ratio (B = 0.4) is significantly reduced by high mainstream turbulence (Tu = 9.67 and 12.9 percent). The mainstream turbulence effect is diminished in the leading edge for higher blowing ratios (B = 0.8 and 1.2) but still exists on the flat sidewall region. Also, the leading edge heat transfer coefficient for blowing ratio of 0.8 increases with increasing mainstream turbulence; but the effect for other blowing ratios [B = 0.4 and 1.2) is not as systematic as for B = 0.8. Surface heat load is significantly reduced with leading edge film cooling.

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Han, J. C., and A. B. Mehendale. "Flat-Plate Film Cooling With Steam Injection Through One Row and Two Rows of Inclined Holes." Journal of Turbomachinery 108, no. 1 (July 1, 1986): 137–44. http://dx.doi.org/10.1115/1.3262013.

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Experiments have been performed to investigate the film-cooling characteristics with steam injection through one row (7 tubes) and two rows (13 tubes) of holes, inclined at an angle of 35 deg, over a flat plate. The spacing between the holes as well as the distance between the rows is 2 1/2 hole diameters. Data have been obtained for both steam and air film-cooling effectiveness at different axial and lateral locations downstream of the injection holes. The blowing rate M varied from 0.2 to 1.5. In the case of one-row injection, the results show that the film-cooling effectiveness with steam injection is about 50 to 100 percent higher than that with air injection at downstream locations, depending upon the blowing rate; however, the increase in film-cooling effectiveness is reduced near the injection hole region at high blowing rates. In the case of two-row injection, the laterally averaged film cooling effectiveness η can be correlated with the two-dimensional film-cooling parameter ξ. The η with steam injection is about 80 to 100 percent higher than that with air injection at low blowing rates and/or at downstream locations (ξ ≥ 15). However, the increase in η with steam injection is reduced near the injection hole region and/or at high blowing rates (ξ ≤ 15).

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Ali, R. R., W. A. W. A. Rahman, H. Hasbullah, R. M. Kasmani, N. Ibrahim, A. N. Sadikin, and U. A. Asli. "Effect of Plasticizers on Tapioca Starch-Based Biofilms via Blown Film Extrusion Process." Advanced Materials Research 1113 (July 2015): 539–44. http://dx.doi.org/10.4028/www.scientific.net/amr.1113.539.

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In this study, a series of tapioca starch-based low density polyethylene (LDPE) biofilms were prepared via extrusion process and further using blown film extrusion with various contents of starch. Various contents of glycerol and palm oil based olein as plasticizers, both ranging from 5 wt% to 20 wt% were added to blends. The starch-based LDPE blends were undergo the melt flow index analysis to study its processability before further process by film blowing extrusion. Both film blowing ability and melt indexes displayed the effect of both plasticizers in starch-based LDPE blends. Starch based LDPE biofilms with addition of 5 wt% palm oil based glycerin show large influence on the shear viscous properties of starch polymer melts compared to glycerol. Palm oil based glycerin would decrease the viscosity of starch polymer melt since it can decrease the polymer entanglement density and increase the ease of disentanglement.

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35

Du, H., J. C. Han, and S. V. Ekkad. "Effect of Unsteady Wake on Detailed Heat Transfer Coefficient and Film Effectiveness Distributions for a Gas Turbine Blade." Journal of Turbomachinery 120, no. 4 (October 1, 1998): 808–17. http://dx.doi.org/10.1115/1.2841793.

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Unsteady wake effects on detailed heat transfer coefficient and film cooling effectiveness distributions from a gas turbine blade with film cooling are obtained using a transient liquid crystal technique. Tests were performed on a five-blade linear cascade at a axial chord Reynolds number of 5.3 × 105 at cascade exit. Upstream unsteady wakes are simulated using a spoke-wheel type wake generator. The test blade has three rows of film holes on the leading edge and two rows each on the pressure and suction surfaces. Air and CO2 were used as coolants to simulate different coolant-to-mainstream density ratio effect. Coolant blowing ratio for air injection is varied from 0.8 to 1.2 and is varied from 0.4 to 1.2 for CO2. Results show that Nusselt numbers for a film-cooled blade are much higher compared to a blade without film injection. Particularly, film injection causes earlier boundary layer transition on the suction surface. Unsteady wakes slightly enhance Nusselt numbers but significantly reduce film cooling effectiveness on a film-cooled blade compared with a film-cooled blade without wakes. Nusselt numbers increase slightly but film cooling effectiveness increase significantly with an increase in blowing ratio for CO2 injection. Higher density coolant (CO2) provides higher effectiveness at higher blowing ratios (M = 1.2) whereas lower density coolant (Air) provides higher effectiveness at lower blowing ratios (M = 0.8).

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Chen, Wei, Hong Hui Shi, Ruo Ling Dong, and Lan Fei Liu. "Experimental Study on Film Cooling Efficiency of Flat Plate through Infrared Thermography Technique." Advanced Materials Research 941-944 (June 2014): 2440–43. http://dx.doi.org/10.4028/www.scientific.net/amr.941-944.2440.

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Experimental investigations were performaed on the flat plate cooling effectiveness through infrared thermography technique. Surface temperature distribution on the flat plate was measured by means of infrared thermography. The experimental facility and infrared thermography method are described in detail. Tests were conducted under different blowing rations which range from 0.3 to 2.0. The result, presented in terms of cooling efficiency distribution along the plate surface shows the influence of blowing ration on heat transfer. The maximum cooling efficiency achieved in the immediate region with a blowing ration of 0.3, then decreases significantly along the streamwise direction. Cooling efficiency increase slightly at the high blowing ration in far downstream area because of the jet adhere to the plat again. Along the spanwise direction, the jet concentrated in the center of the hole at low blowing ration, while spread evenly at high blowing ration. The jet can take different forms, depengding on the blowing ration, the jet can remain attached, detach and reattach or lift-off comletely. Therefore, cooling efficiency does not change with blowing ration monotonously.

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Md Yazid, Muhammad Haziq, and Hamidon Salleh. "An Experiment Investigation of Film Cooling Effectivenes of Sister Hole of Cylindrical Shaped Hole Film Cooling Geometry on a Flat Plate Surface." Applied Mechanics and Materials 773-774 (July 2015): 309–22. http://dx.doi.org/10.4028/www.scientific.net/amm.773-774.309.

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Gas turbines are widely used nowadays for aircraft propulsion and in land-based power generation or in the industrial application. The operating temperature of gas turbine has to be increased in order to increase their effectiveness. Thus, a cooling method known as film cooling is introduced to cool down the high operating temperature of the gas turbine. Film cooling is one of the effective methods in reducing the heat load to a turbine airfoil. This method is cost effective and by far the most common and widely researched method in the industry. Film cooling effectiveness plays a vital role in modern gas turbine technology. This present study will focus on sister holes that are attached to the primary holes at shallow angle of 30°, with 4 different blowing ratios ranging from 0.5 to 2.0. The roles of the different in blowing ratios are to observe the different values of film effectiveness presented by the sister holes design and to select the most effective blowing ratio that suits the design at shallow angle. From the results obtained, the usage of sister holes with shallow angle further increases the film cooling effectiveness particularly at low blowing ratio.

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38

Du, Hui, Srinath V. Ekkad, Je-Chin Han, and C. Pang Lee. "Detailed Film Cooling Measurements over a Gas Turbine Blade Using a Transient Liquid Crystal Image Technique." International Journal of Rotating Machinery 7, no. 6 (2001): 415–24. http://dx.doi.org/10.1155/s1023621x01000367.

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Detailed heat transfer coefficient and film effectiveness distributions over a gas turbine blade with film cooling are obtained using a transient liquid crystal image technique. The test blade has three rows of film holes on the leading edge and two rows each on the pressure and suction surfaces. A transient liquid crystal technique maps the entire blade midspan region, and helps provide detailed measurements, particularly near the film hole. Tests were performed on a five-blade linear cascade in a low-speed wind tunnel. The mainstream Reynolds number based on cascade exit velocity is5.3×105. Two different coolants (air andCo2) were used to simulate coolant density effect. Coolant blowing ratio was varied between 0.8 and 1.2 for air injection and 0.4–1.2 forCo2injection. Results show that film injection promotes earlier laminar-turbulent boundary layer transition on the suction surface and also enhances local heat transfer coefficients (up to 80%) downstream of injection. An increase in coolant blowing ratio produces higher heat transfer coefficients for both coolants. This effect is stronger immediately downstream of injection holes. Film effectiveness is highest at a blowing ratio of 0.8 for air injection and at a blowing ratio of 1.2 forCo2injection. Such detailed results will help provide insight into the film cooling phenomena on a gas turbine blade.

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Zhang, Sheng-Chang, Jing-Zhou Zhang, and Xiao-Ming Tan. "Numerical Investigation of Film Cooling Enhancement Using an Upstream Sand-Dune-Shaped Ramp." Computation 6, no. 3 (September 4, 2018): 49. http://dx.doi.org/10.3390/computation6030049.

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Film cooling enhancement by incorporating an upstream sand-dune-shaped ramp (SDSR) to the film hole exit was numerically investigated on a flat plate under typical blowing ratios ranging from 0.5 to 1.5. Three heights of SDSRs were designed: 0.25D, 0.5D, and 0.75D. The results indicated that the upstream SDSR effectively controlled the near-wall primary flow and subsequent mutual interaction with the coolant jet, which was the main mechanism of the film cooling enhancement. First, a pair of anti-kidney vortices was formed at the trailing ridges of the SDSR, which helped suppress the kidney vortex pair due to the interaction between the coolant jet and the primary flow. Second, a weak separation and a low pressure zone were induced behind the backside of the SDSR, which caused the coolant jet to spread around the film cooling hole and improve the lateral film coverage. With respect to the baseline cylindrical film cooling holes, the effect of the upstream SDSR was distinct under different blowing ratios. Under a low blowing ratio, the upstream SDSR shortened the streetwise film layer coverage in the vicinity of the film hole centerline but increased the span-wise film layer coverage. A relatively optimal ramp height seemed to be 0.5D. Under a high blowing ratio, both the streamwise and span-wise film layer coverages improved in comparison with the baseline case. The film cooling effectiveness improved gradually with increasing ramp height.

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Goldstein, R. J., and P. Jin. "Film Cooling Downstream of a Row of Discrete Holes With Compound Angle." Journal of Turbomachinery 123, no. 2 (February 1, 2000): 222–30. http://dx.doi.org/10.1115/1.1344905.

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A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35 deg inclination angle and 45 deg compound angle with 3d hole spacing and relatively small hole length to diameter ratio (6.3). Both film cooling effectiveness and mass/heat transfer coefficients are determined for blowing rates from 0.5 to 2.0 with density ratio of unity. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficients obtained following injection of naphthalene-vapor-saturated air with that of pure air injection. This technique enables one to obtain detailed local information on film cooling performance. General agreement is found in local film cooling effectiveness when compared with previous experiments. The laterally averaged effectiveness with compound angle injection is higher than that with inclined holes immediately downstream of injection at a blowing rate of 0.5 and is higher at all locations downstream of injection at larger blowing rates. A large variation of mass transfer coefficients in the lateral direction is observed in the present study. At low blowing rates of 0.5 and 1.0, the laterally averaged mass transfer coefficient is close to that of injection without compound angle. At the highest blowing rate used (2.0), the asymmetric vortex motion under the jets increases the mass transfer coefficient drastically ten diameters downstream of injection.

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Ligrani, P. M., and A. E. Ramsey. "Film Cooling From Spanwise-Oriented Holes in Two Staggered Rows." Journal of Turbomachinery 119, no. 3 (July 1, 1997): 562–67. http://dx.doi.org/10.1115/1.2841158.

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Adiabatic effectiveness and iso-energetic heat transfer coefficients are presented from measurements downstream of film-cooling holes inclined at 30 deg. with respect to the test surface in spanwise/normal planes. With this configuration, holes are spaced 3d apart in the spanwise direction and 4d in the streamwise direction in two staggered rows. Results are presented for an injectant to free-stream density ratio near 1.0, and injection blowing ratios from 0.5 to 1.5. Spanwise-averaged adiabatic effectiveness values downstream of the spanwise/normal plane holes are significantly higher than values measured downstream of simple angle holes for x/d < 25–70(depending on blowing ratio) when compared for the same normalized streamwise location, blowing ratio, and spanwise and streamwise hole spacings. Spanwise-averaged iso-energetic Stanton number ratios range between 1.0 and 1.41, increase with blowing ratio at each streamwise station, and show little variation with streamwise location for each value of blowing ratio tested.

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42

Li, Guangchao, Yukai Chen, Zhihai Kou, Wei Zhang, and Guochen Zhang. "Mechanism of Film Cooling with One Inlet and Double Outlet Hole Injection at Various Turbulence Intensities." International Journal of Turbo & Jet-Engines 35, no. 1 (March 26, 2018): 1–9. http://dx.doi.org/10.1515/tjj-2016-0024.

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AbstractThe trunk-branch hole was designed as a novel film cooling concept, which aims for improving film cooling performance by producing anti-vortex. The trunk-branch hole is easily manufactured in comparison with the expanded hole since it consists of two cylindrical holes. The effect of turbulence on the film cooling effectiveness with a trunk-branch hole injection was investigated at the blowing ratios of 0.5, 1.0, 1.5 and 2.0 by numerical simulation. The turbulence intensities from 0.4 % to 20 % were considered. The realizable$k - \varepsilon $turbulence model and the enhanced wall function were used. The more effective anti-vortex occurs at the low blowing ratio of 0.5 %. The high turbulence intensity causes the effectiveness evenly distributed in the spanwise direction. The increase of turbulence intensity leads to a slight decrease of the spanwise averaged effectiveness at the low blowing ratio of 0.5, but a significant increase at the high blowing ratios of 1.5 and 2.0. The optimal blowing ratio of the averaged surface effectiveness is improved from 1.0 to 1.5 when the turbulence intensity increases from 0.4 % to 20 %.

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43

Imram, Ahmed A., Humam K. Jalghef, and Falah F. Hatem. "The Effect of Using Ramps with Trench Cylindrical Holes on Film Cooling Effectiveness." Wasit Journal of Engineering Sciences 3, no. 2 (October 1, 2015): 15–27. http://dx.doi.org/10.31185/ejuow.vol3.iss2.37.

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The effect of introducing ramp with a cylindrical slot hole on the film cooling effectiveness has been investigated experimentally and numerically. The film cooling effectiveness measurements are obtained experimentally. A test study was performed at a single mainstream with Reynolds number 76600 at three different coolant to mainstream blowing ratios 1.5, 2, and 3. Numerical simulation is introduced to primarily estimate the best ramp configurations and to predict the behavior of the transport phenomena in the region linked closely to the interaction between the coolant air injection and the hot air mainstram flow. The results showed that using ramps with trench cylindrical holes would enhanced the overall film cooling effectiveness by 83.33% compared with baseline model at blowing ratio of 1.5, also the best overall flim cooling effectevness was obtained at blowing ratio of 2 while it is reduced at blowing ratio of 3.

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44

Kebir, Farouk, and Azzeddine Khorsi. "Numerical Approach at Flat Plate for Predicting the Film Cooling Effectiveness Part B: Effect Injection Angle." Diffusion Foundations 16 (June 2018): 57–71. http://dx.doi.org/10.4028/www.scientific.net/df.16.57.

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In order to improve the cooling effectiveness of the film, a numerical study was conducted to study the effects of different film-cooled angles on surface heat transfer. In this work CFD simulation has revealed the difference of injection angles ranging from 35°,45°,55°,65° and 90° with different blowing, where the low blowing ratios are represented by M = 0.5, and the high blowing ratios by M = 1.0 and 1.5. And the turbulence closure is done with the help of the k - ω shear stress transport (SST) turbulence model. It is found that the stream-wise variations in the angles of the holes do not really provide a significant change in the adiabatic film cooling effectiveness results. On the other hand, the results indicate that the hole of angles 35°and 45° improved the centerline and laterally averaged adiabatic effectiveness, and the effectiveness decrease particularly at high blowing ratios.

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45

Kim, Kwang Su, and Youn Jea Kim. "Experimental Study on the Film Cooling Performance at the Leading Edge of Turbine Blade Using Infrared Thermography." Key Engineering Materials 326-328 (December 2006): 1161–64. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.1161.

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In order to protect turbine blades from high temperature, film cooling can be applied to gas turbine engine system since it can prevent corrosion and facture of material. To enhance the film cooling performance in the vicinity of the turbine blade leading edge, flow characteristics of the film-cooled turbine blade have been investigated using a cylindrical body model. Mainstream Reynolds number based on the cylinder diameter was 1.01×105 and the mainstream turbulence intensities were about 0.2%. CO2 was used as coolant to simulate the effect of coolant-tomainstream density ratio. The effect of coolant flow rates was studied for various blowing ratios of 0.5, 0.8, 1.1 and 1.4, respectively. Results show that the blowing ratio has a strong effect on film cooling effectiveness and the coolant trajectory is sensitive to the blowing ratio.

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Coulthard, Sarah M., Ralph J. Volino, and Karen A. Flack. "Effect of Jet Pulsing on Film Cooling—Part II: Heat Transfer Results." Journal of Turbomachinery 129, no. 2 (May 31, 2006): 247–57. http://dx.doi.org/10.1115/1.2437230.

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Pulsed film cooling was studied experimentally to determine its effect on film-cooling effectiveness and heat transfer. The film-cooling jets were pulsed using solenoid valves in the supply air line. Cases with a single row of cylindrical film-cooling holes inclined at 35 deg to the surface of a flat plate were considered at blowing ratios of 0.25, 0.5, 1.0, and 1.5 for a variety of pulsing frequencies and duty cycles. Temperature measurements were made using an infrared camera and thermocouples. The plate was equipped with constant flux surface heaters, and data were acquired for each flow condition with the plate both heated and unheated. The local film-cooling effectiveness, Stanton numbers, and heat flux ratios were calculated and compared to baseline cases with continuous blowing and no blowing. Stanton number signatures on the surface provided evidence of flow structures, including horseshoe vortices wrapping around the film-cooling jets and vortices within the jets. Pulsing tends to increase Stanton numbers, and the effect tends to increase with pulsing frequency and duty cycle. Some exceptions were observed, however, at the highest frequencies tested. Overall heat flux ratios also show that pulsing tends to have a detrimental effect with some exceptions at the highest frequencies. The best overall film cooling was achieved with continuous jets and a blowing ratio of 0.5. The present results may prove useful for understanding film-cooling behavior in engines, where mainflow unsteadiness causes film-cooling jet pulsation.

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Coulthard, Sarah M., Ralph J. Volino, and Karen A. Flack. "Effect of Unheated Starting Lengths on Film Cooling Experiments." Journal of Turbomachinery 128, no. 3 (January 16, 2006): 579–88. http://dx.doi.org/10.1115/1.2184355.

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The effect of an unheated starting length upstream of a row of film cooling holes was studied experimentally to determine its effect on heat transfer coefficients downstream of the holes. Cases with a single row of cylindrical film cooling holes inclined at 35deg to the surface of a flat plate were considered at blowing ratios of 0.25, 0.5, 1.0, and 1.5. For each case, experiments were conducted to determine the film-cooling effectiveness and the Stanton number distributions in cases with the surface upstream of the holes heated and unheated. Measurements were made using an infrared camera, thermocouples, and hot and cold-wire anemometry. Ratios were computed of the Stanton number with film cooling (Stf) to corresponding Stanton numbers in cases without film cooling (Sto), but the same surface heating conditions. Contours of these ratios were qualitatively the same regardless of the upstream heating conditions, but the ratios were larger for the cases with a heating starting length. Differences were most pronounced just downstream of the holes and for the lower blowing rate cases. Even 12 diameters downstream of the holes, the Stanton number ratios were 10–15% higher with a heated starting length. At higher blowing rates the differences between the heated and unheated starting length cases were not significant. The differences in Stanton number distributions are related to jet flow structures, which vary with blowing rate.

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bin Salleh, Hamidon, and Jing Zu Yee. "Experimental Study on Film Cooling Effectiveness of Shallow Hole with Upstream Sister Holes." Applied Mechanics and Materials 773-774 (July 2015): 393–97. http://dx.doi.org/10.4028/www.scientific.net/amm.773-774.393.

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In order to increase the thermal efficiency of a gas turbine, the operating temperature has to be increased. This increment may cause the material of the blade to melt. Film cooling is a good option to solve this problem. Various studies has been done on film cooling include the shallow hole and sister holes. The present study focused on an experimental of film cooling effectiveness on shallow hole of 20° with upstream sister holes with 3 blowing ratios which are 1.0, 15 and 2.0. The result showed significant improvement compared to shallow hole of 35°. The optimum blowing ratio is 1.5. Smaller shallow angle and upstream sister holes reduce the jet lifting effect of the secondary air flow. Future study can be done on shallow hole of shallow angle and blowing ratio around 1.5 in order to further improve the film cooling effectiveness.

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Ekkad, Srinath V., Shichuan Ou, and Richard B. Rivir. "Effect of Jet Pulsation and Duty Cycle on Film Cooling From a Single Jet on a Leading Edge Model." Journal of Turbomachinery 128, no. 3 (January 25, 2006): 564–71. http://dx.doi.org/10.1115/1.2185122.

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The effect of jet pulsation and duty cycle on film effectiveness and heat transfer was investigated on a film hole located on the circular leading edge of a blunt body. A transient infrared technique was used to measure both heat transfer coefficients and film effectiveness from a single test. Detailed Frossling number and film effectiveness distributions were obtained for all flow conditions. Jet pulsing frequencies of 5 Hz, 10 Hz, and 20 Hz have been studied. The effect of duty cycle created by the valve opening and closing times was also set at different levels of 10%, 25%, 50%, and 75% of designated 100% fully open condition for different blowing ratios from 0.25 to 2.0. The combination of pulse frequency and duty cycle was investigated for different blowing ratios on a single leading edge hole located at 22 deg from geometric leading edge. Results indicate that higher effectiveness and lower heat transfer coefficients are obtained at the reduced blowing ratios, which result from reduced duty cycles. The effect of varying the pulsing frequency from 5 Hz to 20 Hz is not discernable beyond the level of experimental uncertainty. Effective blowing ratio due to lowering of the duty cycle at a given blowing ratio seems to play a more important role in combination with pulsing, which provides improved cooling effectiveness at lower heat transfer coefficients.

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Zhang, Z., P. G. Lafleur, and F. Bertrand. "Effect of Aerodynamics on Film Blowing Process." International Polymer Processing 21, no. 5 (November 2006): 527–35. http://dx.doi.org/10.3139/217.0037.

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Journal articles on the topic 'Film Blowing'

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