Numerical Analysis and Comparison of Airflow in Rotors with U and V Groove during Rotor Spinning Process

Transcription

1 Numercal Analyss and Comparson of Arflow n Rotors wth and Groove durng Rotor Spnnng Process Ru-Hua Yang, PhD, Chao Lu, Yuan Xue, Hongbo Wang, Wedong Gao Key Laboratory of Eco-textles, Jangnan nversty, Wux, Jangsu Provnce CHINA Correspondence to: Ru-Hua Yang emal: yangrh@jangnan.edu.cn ABSTRACT Rotor spnnng s nown for hgh producton rates and unformty of the resultng yarn. However, determnng machne components whch wll produce the optmum process parameters such as arflow speed to result n the best combnatons of yarn qualty and unformty can be a dffcult tas. The am of ths study s to smulate and analyze the arflow characterstcs n rotors wth and grooves durng the rotor spnnng process. The results obtaned showed that arflow speed resultng from a rotor wth the groove s hgher than that of type. As a result, the statc pressure resultng from the use of the type groove s lower than that of groove. Keywords: Rotor spnnng, groove, arflow, pressure, speed INTRODCTION Rotor spun yarn s one of the most common coarse yarns n the textle maret [1-5]. The ey parts of rotor spnnng consst of the rotor, feedng-combng mechansm, navel and yarn tae up and delvery systems [6]. All components of the system are contaned n a sngle box, called the spn box. Durng the rotor spun yarn spnnng process s fed nto the feed plate, and then fbers are gathered on the collecton groove of the rotor, nsertng twst nto the fbers. The yarn produced s then taen up onto a cross wound pacage, as llustrated by Fgure 1, elmnatng the need for a separate wndng process, as n rng spnnng. The type of groove n the rotors determnes fber type that can be used and yarn thcness that can be produced wth a gven system. and are most wdely used types of rotor grooves (Fgure 2) and both are adaptable to varous fber and yarn types. In ths paper, the statc pressure and ar flow speeds produced by rotors (dameter 46 mm) wth and grooves wll be smulated and analyzed. FIGRE 1. Rotor spun yarn spnnng process. FIGRE 2. Geometrc setch of collecton grooves. Journal of Engneered Fbers and Fabrcs 29

2 MODELS The arflow durng rotor spnnng process obeys mass conservaton and momentum conservaton based upon flud mechancs [7-9]. Mass conservaton accordng to Eq. (1): Where ( ρu ) = 0 u s the ar velocty n (1) x drecton and ρ s ar densty. Momentum conservaton accordng to Eq. (2): ( ρu u ) p = 1 Re τ j Where ρ s ar densty, u s the ar velocty n the x drecton, p s ar pressure, Re s Reynolds number, and τ s the tensor of Newton flud vscous stress from Eq. (3): j j (2) Where G s the result of turbulent netc energy whch s generated by the average velocty gradent, G b s the result of turbulent netc energy b whch s generated by buoyancy, Y M s a result of pulsaton expanson n the compressble turbulent flow, C 1ɛ C 2ɛ and C 3ɛ are expermental constants, σ and σ ɛ are Prandtl numbers accordng to turbulent energy and dsspatve energy separately. S and S ɛ are source terms defned by users. Accordng to the recommended value by Launder et al. [10] and expermental verfcaton, n ths paper, model constants are determned as C 1ɛ =1.42, C 2ɛ =1.68,C 3ɛ =0.09,σ =1.0,σ ɛ =1.3. It s assumed that the arflow speed of nlet s m 3 /s and the pressure of outlet s -8000Pa and the rotor speed s r/mn (Dameter 46 mm wth and grooves respectvely). The SIMPLE algorthm (Sem-Implct Method for Pressure-Lned Equatons) s used to solve the pressure and velocty coupled. The standard -turbulent model s used to smulate ar turbulence, snce the wall functon method s used here. No slp boundary condtons are used at the wall. A geometrc model of the spn box s shown n Fgure 3. τ j u µ = j u j 2 u µ δ j 3 (3) Inlet Where µ s coeffcent of dynamc vscosty, and δ s the functon of Komecer delta. j The standard - turbulent model s appled to smulate the moton of ar flow n rotor as n Eqs. (4) and (5): Outlet FIGRE 3. Geometrc model of spn box. ( ρ) ( ρu ) t µ t = G Gh YM S x µ ρ j σ t j (4) ( ρ ) ( ρu ) t µ t = µ C x j σ j 1 2 ( G C G ) C ρ S 3 b 2 (5) Journal of Engneered Fbers and Fabrcs 30

3 RESLTS AND DISCSSION 0º 0º FIGRE 4. Arflow speed of rotors (-type and -type). 0º 0º FIGRE 5. Arflow speed of grooves (-type and -type). 0º 0º FIGRE 6. Statc pressure dstrbuton of rotors (-type and -type). Journal of Engneered Fbers and Fabrcs 31

4 0º 0º FIGRE 7. Statc pressure dstrbuton of grooves (-type and -type). Arflow speeds and pressures of rotors and grooves are llustrated by Fgures 4-7. They show that arflow speed of the rotor and groove of the -type ( m/s) s slower than that wth -type ( m/s). As a result, the statc pressures of rotor and groove of the type are lower than that of -type (-8287 Pa vs Pa). It can also been seen that arflow speed and statc pressure s not steady at the rotor or groove wall. To understand how the speed and pressure n the groove wall affect the spnnng process, the pressure and speed of a sngle 0 o to 360 o rotaton of the rotor groove are llustrated by Fgure 8 and Fgure 9, respectvely. It s assumed that 0 o s the cross pont of fber transport channel and groove, and angles ncrease n the clocwse rotaton drecton of the rotor. Arflow speeds of and grooves at the groove wall show the same trend, n the shape of the letter M, as shown by Fgure 8. It can be determned that ar flow speed was lowest at 0 o, and then ncreased rapdly to 135m/s at 20 o rotaton. From 20 o to 100 o, the speed s nearly stable, whch s a favorable condton for the combnaton of fbers. The arflow speed then decreased sharply to 30 m/s at 180 o, before ncreasng agan to 110 m/s at 280 o, and then becomng nearly stable untl 340 degrees of rotaton. Durng the rotor spnnng process, the fbers enter the nclne wall, whch s called the slp wall nsde the rotor, as shown by Fgure 1. nder the acton of the centrfugal force of rotor rotaton, the fbers slp nto the groove, and are crculated and pled up nto rngs le lamnated layers, called the fbrous rng or yarn rng tal, whch exerts a doublng effect. When the pecng yarn enters the rotor, t s thrown nto the collectng groove and joned wth the fbrous rng [6]. Then the delvery rollers delver the yarn from the machne and smultaneously the rotor rotaton twsts the yarn tal. Snce the arflow speed reaches a mnmum pont at three separate rotaton angles (0 o, 180 o and 360 o n Fgure 8), the yarn rng tal must formng well before the fber reached the angle of 360 degrees. Ths agrees wth the expermental data, whch shows that that yarn tal s combned wth the pecng yarns and twsted durng the regon of 320 o o rotaton, before t reaches the cross pont of the fber transport channel and groove (0 o and 360 o ). The presence of the valleys n arflow speed durng spnnng process (Fgure 8) may also explan why the rotor spun yarn evenness s not as good as rng spun yarn. Journal of Engneered Fbers and Fabrcs 32

5 FIGRE 8. Arflow speed at the groove wall (-type and -type) from 0 o to 360 o. FIGRE 9. Statc pressure dstrbuton at the groove wall (-type and -type) from 0 o to 360 o. Journal of Engneered Fbers and Fabrcs 33

6 FIGRE 10. Statc pressure dstrbuton at the groove wall (-type and -type) from 20 o to 340 o. The statc pressures of and grooves at the wall showed a smlar trend, n the shape of the letter W as shown n Fgure 9. The plot area s focused between 20 and 340 o n Fgure 10 to more clearly ndcate the trend n ths regon. In the case of each groove type, the statc pressure at the groove wall reaches a maxmum value at 0 o, decreases sharply untl 40 o rotaton, decreases slowly to a trough at about 220 o, then ncreases rapdly untl about 280 o before fallng to a second mnmum at 320 o, fnally ncreasng sharply bac to the orgnal value by the tme the rotaton s complete at 360 degrees. Fgures 8-10 ndcate that the arflow speeds produced by the groove were hgher than those produced by the type. Ths s because the type groove has an nverted bottom, whch more easly collects ar flow under the acton of centrfugal force and pacs the fbers more effcently. Ths could explan why rotor yarn produced by the type rotor showed mproved evenness, hgher breang strength and more even twst between the nsde and outsde yarn structure than that produced usng the type rotor. sually rotor yarn produced usng a type rotor s fluffer and lower n strength wth more wrappng fbers [6]. CONCLSION Arflow characterstcs n rotors wth and grooves durng rotor spnnng process were smulated and analyzed. The maxmum arflow speeds of the and grooves were m/s and m/s respectvely, whle the mnmum were 21.7 m/s and 35.7 m/s respectvely. The valley pont of the statc pressure of and grooves were Pa and Pa respectvely. The data trends n arflow speed and statc pressure of dfferent type of groove ft the expermental resultsrotor yarn produced usng a type rotor showed mproved yarn evenness, hgher breang strength and more even twst than that produced usng the type rotor. ACKNOWLEDGEMENT Ths wor was supported by Natural Scence Foundaton of Jangsu Provnce of Chna No. BK , the Natonal Natural Scence Foundaton of Chna No , the Fundamental Research Funds for the Central nverstes No. JSRP51631A, and A Project Funded by the Prorty Academc Program Development of Jangsu Hgher Educaton Insttutons (PAPD), and the Innovaton Fund Project of Cooperaton among Industres, nverstes & Research Insttutes of Jangsu Provnce (BY ). Journal of Engneered Fbers and Fabrcs 34

7 REFERENCES [1] Hasan H, Semnan D & Tabatabae S, Determnng the optmum spnnng condtons to produce the rotor yarns from cotton wastes, Ind Textla, 61 (6): , [2] Huh Y, Km Y R & Oxenham W, Analyzng structural and physcal propertes of rng, rotor, and frcton spun yarns, Tex Res J, 72 (2) : , [3] Chattopadhyay R & Banerjee S, The frctonal behavour of rng-, rotor-, and frcton-spun yarn, J Text Inst, 87( 1): 59-67, [4] Tyag G K, Goyal A & Dhanda K, Frctonal and mechancal propertes of mercerzed rng- and rotor-spun yarns, Indan J Fber Text, 29 (3) : , [5] Tyag G K, Kaush R C D & Salhotra KR, Indan J Fber Text, Propertes of OE rotor and MJS yarns spun at hgh spnnng speeds, Indan J Fber Text, 22(1): 8-12, [6] Wang S Y & Yu X Y,New Textle Yarns (Donghua nversty, Shangha,) Shangha: Publcaton of Donghua nversty, 2006, 93. [7] Kong L X & Platfoot R A, Tex Res J, Two-dmensonal smulaton of ar flow n tje transfer channel of open-end rotor spnnng Machnes. Tex Res J, 66(10), , [8] Wang F J. Computatonal flud dynamcs analyss (Tsnghua nversty, Bejng), 2004, 7. [9] Kong L X & Platfoot R A. Fber transportaton n confned channel wth recrculatons. Comput Struct, 78(1): , [10] Launder B E, Spaldng D B, Lectures nmathematcal Models of Turbulence, London: Academc Press, 55, ATHORS ADDRESSES Ru-Hua Yang, PhD Chao Lu Yuan Xue Hongbo Wang Wedong Gao Key Laboratory of Eco-textles Mnstry of Educaton Jangnan nversty 1800 Lhu Avenue Wux, Jangsu Provnce CHINA Journal of Engneered Fbers and Fabrcs 35