I ndian Journal of Fibre & Textile Research Vol. 3 1 , December 2006, pp. 5 2 1 -528

Hairiness reduction in polyester spun yarns during ring spinning using air nozzles - Optimization of nozzle and other parameters

R S Rengasamy", V K Kothari & Asis Patnaik

Department of Texti le Technology, I ndian I nstitute of Technology, New Delh i 1 1 0 0 1 6, India

and

S K Bhatia

I ndo Rama Synthetics Ltd., New Delhi 1 1 0 00 I , I ndia

Received I Septell/ber 2005; accepted 21 Novell/bel' 2005

Nozzle and other parameters have been optimized using factorial design approach to reduce the hairiness of ring-spun yarns as the fibre strand coming out of the nip of front roller of ring frame is passed through an air-vortex nozzle before going to the lappet. The parameters. such as axial angle of air in lets in the nozzles, diameter of yarn channel in the nozzle, air pressure suppl ied to the nozzles and denier of fibres used to spin the yarns. have been considered. The 45° angle for air i n lets, 2.2 mm diameter of nozzles, 1 .0 denier fibre and 0.9 bar (gauge) air pressure are the best combinations to obtain lowest yarn hairi ness when using nozzles during spinning. Computational fluid dynamics model has been used to simulate ai rflow pattern inside the nozzle. Swirl ing effect of air, caused by the design of the nozzles, is the main reason behind yarn hairiness reduction. Vortex nature of air along with air velocity is important phenomenon in reducing yarn hairiness. Tensi le and evenness properties of NozzleRing yarns are almost s imi lar to those of the conventional ring yarns spun without nozzle.

Keywords: NozzleRing, Polyester, Swirl ing. Yarn hairi ness IPC Code: Int. Cl 8 DO I H. D02G3/00

1 Introduction The yarns spun from fibres have protruding ends

and loops standing out of the core of the yarns, termed as hairiness. Yarn hairiness affects the appearance of staple yarns and fabrics as well as the efficiency of conversion of staple yarns i nto fabrics. Generation of yarn hairiness during spinn ing and various factors affecting this have been described by several workers. 1 ·(, Yarn hairiness can be reduced by conventional techniques, such as s iz ing for short staples and two-folding for long staples. New technologies, developed to reduce hairiness of ring­spun yarns, are compact spinn ing7.9 and use of air nozzle in r ing spi nning. The l ater technique is also called JetRing spi nning lO. 1 2 or NozzleRing spinning technique. 1 3 NozzleRing spinning technique combines both features of ring and air-jet spinn ing technology. The s ingle nozzle placed below the yarn formation zone acts in a way s imilar to the first nozzle used i n air-jet spinning. The swirl i ng air current inside the nozzle is capable of wrapping the protruding hairs

"To whom al l the correspondence should be addressed. E-mail : rsrengasamy@yahoo.co. in

around the yarn body, thereby reducing yarn hairiness . I O. 1 3 Simulation of airflow pattern by means of computational fluid dynamics (CFD) inside the nozzle can provide a much better i nsight into the actual mechanism of hairiness reduction . In thi s work, a mechanism of hairi ness reduction by using CFD has been proposed. Different nozzle parameters, such ax ial angle of air in lets and nozzle diameter, affect ai rflow characteristics, thereby i nfluencing magnitude of hairi ness reduction . F ibre denier also affects the hairiness formation characteristics of yarns, thereby in tluencing h ai ri ness reduction by the nozzle. S imi larly, different levels of air pressure i nside the nozzles govern the swirling i ntensity of air, which, i n turn, affects the efficiency o f hairiness reduction. There is a lack of publi shed information avai l able on these aspects. The presen t work also deals with opt imization of nozzle parameters, v iz . axial angle of air in lets and nozzle diameter, fibre denier, and air pressure, in reducing yarn hairiness using Box and Behnken factorial design . 14 Tens i le and evenness properties of NozzleRi ng yarns are compared with those of the conventional r ing yarns to check whether there is any deterioration i n yarn quality.

522 IND I AN J. FIBRE TEXT. RES .. DECEMBER 2006

2 Materials and Methods

2.1 Yarn Preparation, Nozzle Mounting, Nozzle Parameters

and Testing Procedures

Polyester fibres of 38 mm length were used to produce 30 tex Z-twisted ring-spun yarns. The yarns were spun separately using I , 1 .2 and 1 .4 denier fibres. The spinning process parameters were as follows: spindle speed 14000 rpm, traveller type and number EM 1 UDR 2/0 and twist per inch (tpi) 1 2 .97. Nozzles placed in nozzle housings were mounted between the front roller nip and the lappet eye at a distance of 1 0 cm from the front rol ler nip on a Lakshmi LG-5/1 ring frame. Compressed air was suppl ied to the nozzles through pipes with a pressure regulator and an air filter. A frame to mount the nozzle housing was fabricated after studying the geometry of the ring fr<.lme for exact positioning of the nozzles without altering the yarn path. A smal l ceramic guide was fixed at the bottom of the frame to keep the yarn i n ccntre of the nozzles. The nozzles were placed in such a way that the front roller nip, axes of nozzle, yarn and ceramic guide l ie in a straight l ine.

To create a swirl i ng effect, four air inlets of 0.4 mm diameter were made tangential to the inner walls of the nozzle. The axial direction of airflow in the nozzles was kept opposite to the direction of yarn movement. Front view of the nozzle along with housing is shown in Fig. 1 .

The process variables used for experimental plan were as follows: nozzle parameters- axial angles 40°, 45° & 50° for air inlets; yarn channel diameter 2.2 mm; fibre deniers 1 .0, 1 .2 & 1 .4 to spin yarns and air pressures 0 .5 , 0.7 & 0.9 bar (gauge). These variables were used for the first series of experiment (Table 1 ) . Second series of experiment consists of the following variables: nozzle parameters - yarn channel diameters 1 .8 , 2 .2 & 2 .6 mm; axial angl e 40° for air i nlets; fibre deniers 1 .0, 1 .2 & 1 .4 and air pressures 0.5 , 0.7 & 0.9 bar (gauge).

The hairiness of yarns was tested on Zweigle G 566 hairiness tester. Number of hairs protruding from yarn (N 1 , N2, N3 , N4, N6 and N8) that are equal to or exceeding 1 mm, 2 mm, 3 mm, 4 mm, 6 mm and 8 mm respectively were observed. S3-hairiness value is the sum of the values N3 , N4, N 6 and N8 . For each sample, 800 m length of yarn was tested for hairiness at a speed of 50 mlmin . Statimat ME tensile tester was used to test the tensi le properties of yarns using a gauge length of 500 mm and cross-head speed of

N 01.1. Ie

" ;&?!o� ./ ' "V.I..¥" Air supply

Fig. I - Front view of the nozzle along with housing

Table I - Ln els of variable

Variable

- I

Angle Series

Axia l angle of air i n lets (X). deg 40 ri bre denier ( Y) 1 .0 Air pressure (Z). bar 0.5

Diameter Series

Nozzle diameter (X). m m Fibre denier ( l') A i r pressure (Z). bar

1 .8 1 .0 0.5

Coded level

0

45 1 .2 0.7

2.2 1 .2

0.7

+ 1

50 1 .4 0.9

2.6

1 .4 0.9

200 mm/min. Thirty readings were taken for each sample. Evenness characteristics of yarns were tested on the Uster evenness tester UT- I . A 1 000 m length of yarn was tested at a speed of 200 m/min. The sensit ivi ty settings used for counting thick, thin and neps were +50% -50% and +200% respectively . Yarn diameters were measured randomly at 1 000 places along the yarns on Leica MZ6 microscope using Lcica quin software. Yarn samples were kept t il standard testing condition for 24 h prior to testi ng.

2.2 Airnow Simulation Method

A fluid flow analysis package (Fluent 6. 1 ) has been used for airflow s imulation i nside the nozzles. The airflow inside the nozzle is turbulent and hence the standard k-E model of turbulence along with standard wall functions was used. l s I t has been assumed that the airflow inside the yarn channel affects the yarn but the presence of yarn has no effect on the airflow patterns and hence yarn was not modeled. The cross­sectional area occupied by yarn is very small compared to that of nozzle diameter ( I : 1 00); hence it is directly not modeled in the simulation. H igh pressure and velocities of the air coupled with the considerably low volume of the yarn compared to that of the diameter of the nozzle also justifies this assumption. Tn the present study, air inlet boundaries are assumed to be "pressure inlet" type while outflow boundaries are assumed to be "pressure outlet" type . I t is a three-di mensional s imulation model ; because of the positioning of air inlets, air veloci ty is resolved

RENGASAMY el al.: OPTIMIZATION OF NOZZLE AND OTHER PARAMETERS 523

into three components, v iz . axial (X-direction), tangential ( Y-direction) and i nward radial veloci ties (Z-direction). Swirling action in the nozzle is created by the tangential and axial air veloc i ty components. Magni tude of radial velocity is negligible because the fluctuation in the Z-axis is very small as compared to fluctuations in the X-axis and Y-axis . For simplification, i t i s assumed that the process is adiabatic, i .e. with no heat transfer through walls . The flow model used was viscous, compressible airflow. Air pressures used for s imulation studies were 0.5 and 0.9 bar (gauge). All the nozzles used were of the same length and outer diameters of the nozzles were kept constant for experimental purpose.

3 Results and Discussion Box and Behnken 14 design was chosen for three

variables and three levels (Table 1 ) . S3-hai riness values are given in Table 2 . The response surface

Run. no.

A l A2 A3 A4 A5 A6 A7 A8 A9 A I O A l l A I 2 A I 3 A I 4 A I 5

D I D2 D3 D4 D5 D6 D7 D8 D9 D I O D I I D I 2 D 13 D 1 4 D I S

Table 2 - S3-hairiness values

__ L_e_v_e_Is_o_f_va_r_ia_b_le ___ S3-hairiness X y Z

Angle Series

- I - I 0 - I 0

- I I 0 I 0

- I 0 - I 0 - I

- I 0 I 0 0 - I - I 0 - I 0 - I I 0 I I 0 0 0 0 0 0 0 0 0

Diameter Series

- I - I 0 - I 0

- I 0 I 0

- I 0 - I 0 - )

- I 0 I 0 0 - I - I 0 - I 0 - I ) 0 I I 0 0 0 0 0 0 0 0 0

482 498 1 042 1 1 04 494 507 458 474 479 1056 453 937 464 469 473

487 502 1060 1 1 2 1 500 525 466 484 497 1 1 30 470 997 488 480 476

equations for S3-hairiness values are given i n Table 3 along wi th the square of correlation coefficients between the experimental values and calculated values obtained from the response surface equations.

3. 1 Mechanism of Hairiness Reduction

S3-hairi ness values for yarns spun from 1 .0, 1 .2 and 1 .4 denier fibres without using nozzles are 590. 629 and 1 528 respectively . S3-hairiness values of NozzleRing (using nozzles) yarns are significantly lower than these values. Using CFD, a mechanism of hairiness reduction is proposed. Figure 2 shows the path lines of airflow, released from air inlet swirl ing i n anti-clockwise direction when viewing the nozzle from front roller towards the lappet . Swirling action is created by the tangent ial and axial veloci ty components of air velocity. Air enters the nozzles at the angles of 40°, 45° and 50° wi th the axis of nozzles. All the four air inlets lie on the same horizontal plane. Absence of staggering in the location of air i nlets helps to generate swirl i ng airflow, as air coming form one air inlet does not i ntrude i ns ide the other, rather

Fig. 2 - Typical path l i nes of air i nside the nozzle

Table 3 - Response surface equations for various parameters

Parameter Response surface equation Coefficient of determination

S3-hairi ness 457.7 + 278.4X - 26.8Z 0.992 (Angle Series) + 33.8X2 + 2 8 1 .8 y2

S3-hairiness 488.4 + 1 4.9X + 294Y 0.997 (Diameter Series) - 29.4Z +294.6y2 - 26.5YZ

524 INDIAN J. FIBRE TEXT. RES., DECEMBER 2006

airflow coming from all the four air inlets goes spirally around the yarn, resulting in vortex flow. Divergent portion i n the upper section of the nozzle also assists in swirling. Due to the action of thi s vortex or the swirling motion, yarn with Z twist i s untwisted at the core of the nozzle as i t enters the nozzle while the protruding hairs being wrapped over the yarn surface in S direction. As the yarn leaves the nozzle, the false twisting action of swirling air currents twists the yarn having wrapped fibres, thereby restoring the original twist in the yarn. This process leads to the wrapping of protruding hairs around the yarn body, thereby reducing yarn hairiness.

3.2 Influence of Nozzle Axial Angle, Fibre denier and Air Pressure on S3-hairiness Values

Figure 3 shows the influence of fibre denier and air pressure on S3-hairi ness values for nozzle with air inlets having axial angle of 45°. The S3-hairiness values increase with the increase in fibre denier. This trend is simi lar to that reported by other workers. 1 6

This can be attributed to the fact that with the increase in fibre denier, bending and torsional rigidities of the fibre increase. It is difficult for air currents to fold/bend and wrap the hairs. Also, rigid fibres have more tendencies to protrude from yarn surface giving higher hairiness. 1 7 There is slight increase in the hairiness values as the fibre denier increases from - 1 .0 to 0.0 levels. Although the number of fibres in yarn cross-section using 1 .0 denier fibres is more in comparison to yarn spun from 1 .2 denier fibres, the torsional rigidity of the fibres i s the major influencing

w :; til til w .... c. .... <

1 .D �· ��

. • ' .'I ' / �I .' .. ' .• l . 1 1 / 1 1 1 ) 1 / 1 1 i

0 .5

I I I II

0.0 "

-0.5

- 1 .0 L-.�_..L...:...�...L.-""-'-�.....!......L.:.!.""--'-'--- 1 .0 -0 .5 0 ,0 0 .5 1 .0

Fibre denier

Fig. 3 - Influence of levels of fibre denier and air pressure on S3-hairiness values (per 1 000 m) for nozzle with air i nlets having axial angle of 45°

factor contributing to yarn hairiness during spinning.5

With the i ncrease i n air pressure S3-hairiness values decrease. At high air pressure, as the swirl ing intensity of air ins ide the nozzle i ncreases, there is improvement in wrapping of fibres around yarn body, thus decreasing the yarn hairiness. 1 3

The combined effect of fibre denier and air pressure on S3-hairiness values indicates that -0.5 level of fibre denier ( 1 . 1 denier) and 1 .0 level of air pressure (0.9 bar) give the optimum zone in terms of reducing the hairiness of yarns.

The i nfluence of air pressure and axial angle of air inlets on S3-hairiness values i s shown in Fig. 4. With the i ncrease in air pressure from - 1 .0 to 1 .0 levels, S3-hairiness values decrease. With the i ncrease in nozzle axial angle from - 1 .0 to 0 levels, the S3-hairiness values decrease, but from 0 to 1 .0 levels, S3-hairiness value increases. The best resul t i s found for 0.0 level of axial angle (45°) ; other levels, i .e. - 1 .0 and 1 .0 levels, show more or less s imilar S3-hairiness values. CFD model ing has been used to describe the results by comparing resultant air velocity of the nozzle having axial angle of 45° with nozzle having axiai angle of 50°. All the measurements are made at constant air pressure of 0.5 bar. For this purpose, 30 tex yarn spun with nozzle was taken and i ts diameter was measured on a microscope using Leica quin software. The measured diameter of yarn is 0.238 mm. As mentioned previously in the simulation section, it is assumed that the yarn does not have much intluence on the flow and hence it was not modeled during simulation. A cylinder of 0.238 mm (analogues to yarn) was superimposed on the air

� : :�/ c ro ro 'x ro Q) N N a Z

-0.5

. .......

.

. : .•..

.

:.

: ..... : .. :.: . .......... :.:.: •.. .... : ... ",:

....

.

� ..

- 1 .0 L.;:.��L:::.-'-..;....::L.;;.........;...�J;....;:.�;;...;;..J - 1 ,0 -0.5 0.0 0 .5 1 .0

Air pressure

Fig. 4 - I nfluence of levels of air pressure and axial angle of air i nlets on S3-hairiness values (per 1 000 m) for yarn spun from 1 .2

denier fibres

RENGASAMY et al.: OPTIMIZATION OF NOZZLE AND OTHER PARAMETERS 525

velocity profile obtained from s imulation such that the nozzle and cylinder are coaxial to get air velocity acting on yarn surface.

Figure 5 shows resultant velocity of air acting on yarn surface and hair at various distances measured along the axi s of the nozzle, tak ing neck of the nozzle (X = 0 and Y = 0) as origin . Air velocity Vty and Vth (near inner wall of the nozzle) represents resultant air velocity acting on yarn surface and hair respectively. Other legends indicated in the Fig. 5 represent the respective axial angle. The figure indicates that the air i s coming from the bottom of the nozzle with constant resultant velocity, while near the neck, it increases suddenly. This sudden increase in resultant veloci ty i s due to the presence of four air i nlets, the air stream from them mix up w ith the air coming through the entry of yarn channel creating a swirling effect. After that the resultant air velocity decreases due to the presence of d ivergent portion of the nozzle where air diffuses very quickly. Resultant air velocity trend acting on the yarn and hair is s imilar, except that the hair i s subjected to a h igher resultant air veloci ty due to a reducing air veloci ty gradient from nozzle i nner wall to axi s of the nozzle. Resultant air velocity acting on the surface of yarn and hair in the case of the nozzle with 45° axial angle i s h igher than that of the nozzle with 50° axial angle. So, the swirl ing i ntensity created by nozzle with 45° axial angle i s stronger than that of the nozzle w ith 50° axial angle, thereby more hairiness reduction by the former. The combined effect of air pressure and nozzle axial angle on S3-hairiness values indicates that 0.0 level of nozzle axial angle (45°) and 1 .0 level of air pressure (0.9 bar) give

(J) E :5-Ti o Qj >

-'-Vty50 350 -Vth-50 --Vty45 300 --Vth-45

�.Ol -0 008 -0.006 �.004 �.002 0 0.002 0.004 0.006 0.008 om Distance, m

Fig. 5 - Resultant velocity of air acting on the surface of yarn and hair in the nozzles with axial angles of 45" and 50°

the optimum zone i n terms of reducing the hairiness of yarns.

3,3 Influence of Yarn Channel Diameter, Fibre Denier and

Air Pressure on S3-Hairiness Values

Figure 6 shows the combined effect of fibre denier and air pressure on S3-hairiness values which indicates that -0.5 level of fibre denier ( 1 . 1 denier) and 1 .0 level of air pressure (0.9 bar) give the optimum zone in terms of reducing the hairiness of yarns when the yarn channel d iameter is kept as 2.2 mm. This result follows the s imilar trend as described earlier.

The influence of nozzle diameter and air pressure on S3-hairiness values for yarn spun from 1 .2 denier fibre is shown i n Fig. 7. With the increase in air

Fibre denier Fig. 6 - Influence of levels of fibre denier and air pressure on S3-hairiness values (per 1000 m) for nozzle with a channel d iameter of 2.2 mm

- 1 .0 L-"":""-,-L::..... __ L:....L......-"-L:....-'-.L....J - 1 .0 -0.5 0.0 0 .5 1 .0

Nozzle diameter Fig. 7 - Influence of levels of yarn channel diameter and air pressure on S3-hairiness values (per 1000 m) for yarn spun from 1 .2 denier fibres

526 INDIAN 1. FIBRE TEXT. RES .. DECEMBER 2006

pressure from - 1 .0 to 1 .0 levels, the yarn hairiness decreases due to the i ncrease in swirl i ng i ntens i ty . 1 3

S imilarly, with the i ncrease i n yarn channel d iameter from - 1 .0 to 1 .0 levels, the yarn hai ri ness i ncreases. Us ing CFD modeli ng, the nozzles with 1 .8 and 2.6 mm yarn channel diameters are compared for air veloci ty at an operati ng pressure of 0.5 bar.

A i r veloc i ty Vty and Vth (near i nner wall of the nozzle) represents resu l tant air veloc ity acting on yarn surface and hair respect ively. Other legends i ndicated i n the Fig. 8 represent the respect ive channel

1 __ �:�-·�-·�----·--· 3:;O --- ·---·--·--·�--I . --Vty-l .& 300 . I --Vth-1 .8

� I :.:. 1 R I � � I ; 1 � I ; I L I

��--���4-.001 ·0 (1]3 .0 00.; ·0 004 ·0.002 0 0.002 0 0(14 0 .006 OWS O.oI

Distance. m

Fig. S - Resultant veloc i ty of air aCling on the surface of yarn and hair for the nozzles with yarn channel diameters of 1 .8 111111

ancl 2.6 1111ll

d iameter. H igher air veloc i ty i s observed i n the vic in i ty of both yarn and hair for nozzle with l . 8 mm diameter, whereas the air veloci ty is much lower i n the case o f the nozzle w i th 2 . 6 m m diameter. So. swirl i ng i ntensi ty created by nozzle with 1 .8 mm d iameter i s stronger than that of the nozzle with 2.6 mm diameter, thereby more hairiness reduction by the fanner.

The combined effect of nozzle d iameter and air pressure on S3-hairiness values i nd icates that - 1 .0 level of nozzle d iameter ( 1 .8 mm) and 1 .0 level of air pressure (0.9 bar) g ive the opt imum zone in terms of reducing the hairiness of yarns .

3.4 Comparison of Conventional ami NozzlrRing Yarns for

Tensile and Evrnness CharackI"istics

NozzleRing and ring yarns have been evaluated for tens i le and evenness properties and the resu l ts are shown i n Table 4.

The tenaci ty of NozzleR i ng yarns is s l ightly better than that of convent ional ring yarns (spun \vi thout nozzle). The sl ight i mprovement in tenac i ty is probably due to the tight wrapping of the surf<]('p fibres around the yarn body, which contributes to tile

h 10· t t B h · · . . . yarn strengt . li t t I S lIlcrease III tenac i ty tS not statistical ly s ignificant. There IS no s ignificant difference between the breaking elongation of NozzleRing yarns and conventional r ing yarns.

There i s a sl ight i ncrease in the unevenness of NozzleRing yarns i n comparison to conventional ring

Table 4 - Tensile and evenness prop�rties of ring and NozzleRing yarns

Sample Tenacity Ell ltlgat i on Thin places Thick places Neps U% I mperfections/krn rode cN/tl:x Sb (·50% ) ( +50%) (+200%)

Control sample 1 .0 den 34.30 1 3 .39 2 5 I I 7.04 1 9 1 .2 den 35. 1 1 1 3 .40 4 7 i 3 7.56 24 1 .4 den 35.82 1 3 .42 7 1 0 1 6 7.90 33

A I 35.58 1 3 .46 4 7 1 4 7. 1 0 26 A2 35.22 1 3 .55 4 8 1 5 7 . 1 2 27 A3 37.77 1 4.74 10 1 2 1 8 8 . 1 8 40 A4 37.92 1 4.62 1 0 1 3 20 8 .20 43 AS 35.26 1 3.43 6 8 1 4 7.69 28 A6 35.43 1 3 .38 6 9 1 5 7.63 30 A7 38.29 14.53 1 0 1 4 1 9 8.3 1 43 A8 37.8 1 1 4.3 1 I I 1 3 20 8.27 43 A9 34.42 1 3 .24 3 7 1 2 7. 1 3 22 A IO 36. 1 7 1 3 .47 7 1 2 1 8 8.03 37 A l l 36.70 1 4.35 7 9 16 7.53 32 A 1 2 38.95 14 .8 1 1 2 1 5 22 8.52 49 A i 3 36.54 1 3.66 7 1 0 1 7 7.83 34 A 1 4 36.64 1 3.63 8 1 1 1 7 7 .87 36 A 1 5 36.70 1 3.52 7 1 0 1 8 7.62 35

COllld -

RENGASAMY ef al. : OPTIMIZATION OF NOZZLE ANO OTHER PARAMETERS 527

Table 4 - Tensi le and evenness properties of ring and NozzleRing yarns - Contd

Sample Tenacity Elongation Thin places code cN/tex % (-50%)

0 1 35 .25 1 3 .38 4 02 35.32 1 3 .6 1 5 03 37.62 1 4.42 1 0 04 37.79 1 4.5 1 1 2 05 35.2 1 1 3 .23 7 06 35 .48 1 3 .2 1 8 07 38.32 1 4.32 1 0 08 38.4 1 1 4.43 1 1 09 34.53 1 3 .48 4 0 1 0 36.07 1 3 .2 1 8 0 1 1 36.92 1 4.25 7 0 1 2 39.06 14.28 14 0 1 3 36.39 1 3 .49 8 0 1 4 36.47 1 3 .24 7 0 1 5 36.56 1 3 .46 7

yarns. The overall change in yarn evenness i s probably due to the concentration of the mass in a very short length brought about by the swirling action of nozzle pressure. I D- 1 1 The difference between the evenness values of NozzleRing and regular ring yarns is not statistically significant.

4 Conclusions A process of hairiness reduction is explained with

the help of CFD. Swirling effect of air, caused by the design of the nozzles, is the main reason for hairiness reduction. Fibre denier i s major i nfluencing factor in reducing yarn hairiness. The combined effect of fibre denier and air pressure on S3-hairiness values indicates that the 1 . 1 denier fibres and 0.9 bar air pressure give the optimum zone in terms of reducing the hairiness of yarns . The combined effect of ai r pressure and axial angle on S3-hairiness values indicates that the 45° axial angle and 0.9 bar air pressure give the optimum zone for hairiness reduction . The combined effect of channel diameter and air pressure on S3-hairiness values indicates that the 1 .8 mm diameter and 0.9 bar air pressure give the optimum zone for controll ing the hairiness of yarns. Axial angle of 45°, channel di ameter of 2.2 mm, fibre denier of 1 .0 and air pressure of 0.9 bar give the lowest value in terms of reducing yarn hairiness. NozzleRing yarns have sl ightly better tensile strength compared to conventional ring yarns . Unevenness of NozzleRing yarns is sl ightly h igher than that of the conventional ring yarns. The difference between the

Thick places Neps U% Imperfections/km (+50%) (+200%)

8 1 5 7.08 27 9 1 5 7 . 1 4 29 1 3 20 8.02 43 1 4 2 1 8. 1 2 47 9 1 5 7.56 3 1 9 1 5 7 .67 32 14 2 1 8.27 45 1 5 2 1 8.39 47 9 1 3 7.20 26 1 4 20 7.93 32 1 0 1 8 7.67 35 1 7 24 8.69 55 1 1 1 9 7.60 38 14 20 7.7 1 4 1 1 3 2 1 7 .8 1 4 1

NozzleRing and ring yarns in terms of tensile and evenness properties is not statistically significant.

Acknowledgement The authors acknowledge Department of Science

and Technology, Government of I ndia, for providing financial assistance to carry out this research work.

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