Zou Z.-Y., Liu S.-R., Zheng S.-M., Cheng L.-D.; Numerical Computation of a Flow Field Affected by the Process Parameters of Murata Vortex Spinning. FIBRES & TEXTILES in Eastern Europe 2010, Vol. 18, No. 2 (79) pp. 35-39. 35 Numerical Computation of a Flow Field Affected by the Process Parameters of Murata Vortex Spinning ZhuanYong Zou, ShiRui Liu, ShaoMing Zheng, LongDi Cheng Key Lab of Textile Science & Technology, Ministry of Education, Donghua University 2999 North Renmin Road, Songjiang District, Shanghai 201620, P. R. China E-mail: ldch@dhu.edu.cn Abstract In this paper, fow patterns, such as the velocity distribution along the radius of the nozzle block at section A-A and static pressure distributions along the nozzle block axis and its radius at section A-A, affected by the nozzle block’s structure parameters and the velocity at the jet orifce exit in Murata vortex spinning are investigated by the method of numerical computation. The results show that the tangential, axial and radial velocities inside the nozzle block are signifcantly affected by the jet orifce angle and velocity at the exit of the jet orifce as well as by the diameter at the inlet of the nozzle block. Static pressure distributions inside the nozzle block are signifcantly affected by the jet orifce angle, the velocity at the exit of the jet orifce, the outer diameter of the hollow spindle and the distance from the inlet of the nozzle block to the inlet of the hollow spindle. Key words: Murata vortex spinning, process parameters, airfow, numerical com- putation. theoretically analysed the special fbre trajectory of MVS yarn with respect to the principle and process of yarn forma- tion. He discovered that the fbre spatial confguration in vortex spun yarn con- sists of core fbre, migration wrapper f- bre and regular wrapper fbre [8]. Soe et al. compared the structure and properties of MVS yarns with ring and rotor spun yarns and found that MVS yarn is mainly composed of core fbres and wrapper f- bres [9]. The structure and performance of MVS yarn is mainly determined by the patterns of the fow feld inside the nozzle block, which is simulated by constructing a Computational Fluent Dynamic (CFD) Model, Zou and Pei et al [10, 11]. Zou also investigated the twisted strength act- ing on vortex spun yarn from the whirled airfow [12]. The velocity of the whirled airfow will gradually attenuate in the yarn formation process, fowing to the outlet of the nozzle block due to the air viscosity resistance, whose attenuated law was discussed by Zou and used to perform a force analysis of a separated f- bre in the twist chamber which explained the generation of thin places in MVS yarn [13]. However, there are few studies that completely focus on the effect of the structure parameters of the nozzle block on fow patterns inside it. In this paper, the effects of the velocity at the exit of the jet orifce and structure parameters of the nozzle block on the characteristics of the fow feld inside the nozzle block has been analysed, which offers the basis of a theory for designing the nozzle system and optimising the spinning process. n Numerical computation A CFD model is constructed according to corresponding structure parameters of the n Introduction In Murata vortex spinning (MVS), the whirled airfow inside the nozzle block, formed by compressed air through the jet orifces, twists the open-trail-end fbres into MVS yarn, which is drawn out from the hollow spindle, as shown in Fig- ure 1 [1]. Previous studies have focused on the structure and properties of MVS yarns through experimental methods. Ty- agi et al. and Basal et al. investigated the infuence of the distance between the hol- low spindle and front rollers, the jet ori- fce angle, nozzle pressure and delivery speed on the structure and characteristics of MVS yarns [2, 3]. Ortlek et al. dis- cussed the effect of the hollow spindle di- ameter and spindle working period on the properties of 100% viscose MVS yarns and found that the various properties of MVS yarns are signifcantly affected by the spindle diameter and spindle working period [4]. Ortlek et al. also researched the infuence of selected process vari- ables, such as the delivery speed, nozzle pressure and elastane linear density, on the mechanical properties of core-spun vortex yarns containing elastane [5]. The viscoelastic behavior of MVS yarns was analysed by Zou et al. [6, 7] in which he Figure 1. Schematic diagram of MVS yarn formation.