Design of the nozzle of a yarn suction gun for fully drawn yarn

Abstract

The yarn suction gun is a kind of fluid machinery using compressed air as power. Airflow geometry in the gun has a significant influence on the airflow distribution, which decides the yarn suction performance. To clarify the effect of the nozzle structure on the yarn suction performance, we designed 16 nozzles, determined yarn suction force F, mass flow rate of compressed air G and analyzed yarn suction efficiency η, which is defined as the ratio of F to G. The rational geometrical parameters are obtained as follows: the number of jet orifices N = 3, jet orifice diameter d = 1.6 mm, jet orifice angle Φ = 75° and passage diverging angle of the nozzle θ = 60°. A smaller N reduces the conflict between jet streams and then increases η. Decreasing d contributes to greater η but smaller F. In the range of Φ ≤ 75, increasing Φ causes both F and η to increase. An appropriate θ promotes the yarn suction performance by helping the injected air to go forward smoothly and reducing backflow. It is more rational to use η to evaluate the yarn suction performance.

Keywords

Yarn suction gun yarn suction efficiency spinning machinery fluid machinery

The yarn suction gun (called YSG hereafter), an indispensable part of the spinning machine for producing yarns, is used to pick up a running yarn at the beginning of spinning or yarn breakage and take it to a bobbin, and also to transfer the yarn from a full bobbin to an empty one during the bobbin exchange step. The YSG is also used for producing nonwoven fabrics.¹

Compressed air is mostly used as a working fluid of the YSG. Yamaguti and Takahashi² and Sano et al.³ proposed a YSG based on the idea of utilizing pressurized water instead of compressed air. A fine YSG is capable of giving powerful suction of a yarn with high energy efficiency, that is, low consumption of the compressed fluid.

Some works have been reported on the YSG since the first patent for a YSG invented by Miller.⁴ Ashby et al.^5,6 and Bunting et al.⁷ made some improvements to Miller’s type YSG. The above YSG has airflow geometry similar to that of an air-jet loom by virtue of Bernoulli’s principle and therefore could only be used to handle the polyester yarn moving at a speed of up to 2700 m/min.⁸ Richter⁹ and Vanderip¹⁰ used an air vortex to increase the capacity of the YSG, which was capable of handling a yarn at a speeds of up to 4500 m/min. McFall¹¹ synthesized the Miller’s and Richter’s type YSG to make a new one with less noise. Tseng¹² carried out an improvement by adding an accelerator in the YSG, which was similar to the present YSG.

So-called super-high-speed spinning is at the wind-up speed of 6000 to 10,000 m/min, even more. However, the speed of the yarn sucked by the conventional YSG is less than 6000 m/min. For introduction of the super-high-speed winder, rotation of the winding roller has to be slowed down so that the YSG can capture the running yarn, and after threading, the winding roller is sped up to the regular speed. In this mode the available high speed is not fully used and the super-high-speed winder cannot display its full performance. Hence the demand has developed for a new YSG with super-strong suction capacity.

In order to provide a technological support for designing a YSG with high performance such as strong suction of yarn and low consumption of compressed air, Iemoto et al.¹³ and Li et al.^14–17 have conducted a systematical study on the effect of four geometrical parameters of a YSG for polyester fully drawn yarn (FDY) , which is the most representative, on the yarn suction performance,¹³ flow field^14,15 and yarn motion.^16,17 However, the effect of nozzle structure, especially the number of jet orifices and jet orifice diameter, still remains unclear.

In this research, we studied the effect of the nozzle structure on the yarn suction performance of the YSG for polyester FDY for improvement of the YSG with high suction performance.

Experimental details

Experimental apparatus and method

The outline of experimental apparatus is shown in Figure 1. The compressed air from a compressor ① arrives in a rectification tank ②. Passing through a valve ③ and flow meter ④, the air from the rectification tank is regulated to a set pressure by a pressure adjuster ⑤, and then is supplied to the YSG ⑥. It finally flows out into the atmosphere with a yarn. Tension and speed of the yarn released from a bobbin ⑦ is regulated by a tension adjuster ⑧ and feed roller ⑨, respectively, and the yarn is then sucked into the YSG. Then yarn suction force, that is, yarn tension, measured by a tension meter ⑩ is used to show the yarn suction performance.

Figure 1.

Outline of experiment apparatus.

Geometry of the yarn suction gun

Figure 2 shows the illustration of the YSG used in this study. It is mainly composed of a yarn inhalation tube ①, nozzle including four jet orifices ②, and yarn propulsion tube consisting of a Laval tube ③ and straight tube ④. The basic working mechanism has been described in previous papers^13,14 and therefore the description of it is omitted here.

Figure 2.

Illustration of yarn suction gun (the number of jet orifices N = 4).

In this study, we limit consideration to four geometrical parameters of the nozzle: the number of jet orifices N, jet orifice diameter d, jet orifice angle φ, and passage divergence angle of nozzle θ, as shown in Figure 2. Values of each geometrical parameter are shown in Table 1. For the purpose of comparability with the previous study,¹³ polyester yarn of 166.7 dtex/48 f was used; feed speed of the yarn and supplied air pressure were set at 600 m/min and 0.5 MPa (gauge pressure), respectively.

Table 1.

Geometry parameters of the nozzle

Geometry parameter	Value
The number of jet orifices N	1, 2, 3, 4, 5
Jet orifice diameter d (mm)	1.6, 1.8, 2.0, 2.2, 2.4
Jet orifice angle ϕ (°)	60, 65, 70, 75, 80
Passage divergence angle of nozzle θ (°)	30, 45, 60, 75

Evaluation of yarn suction performance

The yarn suction force F, speed of the sucked yarn and pressure at the inlet of yarn inhalation tube can be used as indexes to compare the yarn suction capacity of the YSG. In order to determine the rational geometry of the YSG from the viewpoint of energy efficiency, performance of the YSG is evaluated by the ratio of F to mass flow rate of compressed air G, named yarn suction efficiency η.

Results and discussion

Effect of the number of jet orifices N

Figure 3 shows the effect of the number of jet orifices N on the yarn suction performance of the YSG. The total cross-sectional area of the jet orifices in each nozzle is 12.56 mm². We fixed the other geometrical parameters at ϕ = 75° and θ = 60°. The yarn cannot be sucked into the yarn inhalation tube when N = 1. Therefore, both the yarn suction force F and the yarn suction efficiency η are zero, as shown in Figure 3(a) and (c). It is considered that, in this case, there is no or a weak swirling flow developed in the YSG because the injected air expands and diffuses freely near the outlet of jet orifice.

Figure 3.

Effect of the number of jet orifices N on yarn suction performance at ϕ = 75° and θ = 60°: (a) yarn suction force F; (b) mass flow rate of compressed air G; (c) yarn suction efficiency η.

The yarn suction force F, that is, frictional force between the yarn and the air, can be represented by the following equation according to the computation theory of air drag:^14,18

F = C_{f} \frac{ρ}{2} (v - v_{y})^{2} \cdot π d_{y} L_{y}

(1)

where C_f is frictional drag coefficient, ρ air density, v air speed, v_y yarn speed, d_y yarn apparent diameter and L_y length of yarn in the airflow. Thus, F exerted on a yarn running at the same speed will depend on v, ρ and L_y.

When being supplied with the compressed air, the YSG produces a swirling airflow, that is, helical airflow, with high speed and high density near the wall in the yarn propulsion tube. The high-speed rotation of airflow causes the sucked yarn to run in the helical airflow. Therefore, a strong frictional force is exerted on the sucked yarn owing to large v and ρ according to Equation (1). This helical motion of the yarn causes L_y to increase greatly because the yarn length in the air is larger in a helix than in a straight line. From Equation (1), a larger F is produced owing to a longer L_y. Ignoring the friction between the yarn and the tube wall, F increases with the intensity of the swirling flow.

When N is increased, the swirling flow develops and becomes strong because free expansion of the injected air is constricted among jet streams and they move forward in a helix motion. Therefore F becomes large. F increases and then decreases with an increase in N, and takes the maximum at N = 3, as shown in Figure 3(a). The reason for this variation may be due in part to the conflict among jet streams, which converts kinetic energy into thermal energy and weakens the swirling flow. The jet stream conflict increases with N, more kinetic energy transforms into thermal energy, and is therefore ineffective in producing the increase of the action on the yarn. The mass flow rate of compressed air G does not change too much with N (Figure 3(b)) because of the constant total cross-sectional area of the jet orifices in each nozzle. Therefore, the variation of η with N shown in Figure 3(c) is similar to that of F shown in Figure 3(a). Thus, it is considered that the rational value of N is 3 in terms of η and F.

Effect of jet orifice diameter d

Dependence of the performance of the YSG on the jet orifice diameter d is shown in Figure 4, fixing N, ϕ and θ at 3, 75° and 60°, respectively. When d ≤ 2.2 mm, the yarn suction force F increases with d, as shown in Figure 4(a). The maximum value of F is reached at d = 2.2 mm. With further increase in d, F decreases. The mass flow rate of compressed air G increases with d generally (Figure 4(a)). Choking of the flow may occur in the jet orifices, where air velocity (Mach number = 1.0) and density are constant. G is proportional to the total cross-sectional area of the jet orifices. This appears to be the reason why increasing d causes the increase in G, which increases F because more energy of the compressed air is exerted on the yarn. An over-large d is not helpful for the development of swirling flow, and therefore decreases F. The yarn suction efficiency η decreases with an increase in d, as shown in Figure 4(b). The main reason is considered as follows. When the YSG is supplied with the compressed air, jets, that is, streams, issue from the orifices. If d is decreased, the velocity of the air at exits of the orifices is larger, accompanied by the streamlines with smaller curvature.¹⁴ It tends to produce the swirling flow with larger intensity, and therefore promotes η. To facilitate the processing and ensure the machining accuracy, d also should not be too small. Thus the rational value of d is about 1.6 mm, taking account of both F and η.

Figure 4.

Effect of jet orifice diameter d on yarn suction performance at N = 3, ϕ = 75° and θ = 60°: (a) yarn suction force F and mass flow rate of compressed air G; (b) yarn suction efficiency η.

Effect of jet orifice angle ϕ

Figure 5 shows the yarn suction force F, the mass flow rate of compressed air G and the yarn suction efficiency η at different jet orifice angles ϕ. Values of N, d and θ are fixed at 3, 1.6 mm and 60°, respectively. In the range of ϕ from 0° to 75°, F increases with ϕ and is at a maximum at ϕ = 75°, as shown in Figure 5(a). The reason is considered as follows: the airflow maintains a helical motion in the yarn propulsion tube, where the sucked yarn is developed into helical motion owing to the airflow rotation. As ϕ increases, the helical pitch of the swirling flow becomes small and the yarn length in the yarn propulsion tube becomes long, and as a result, frictional force between the air and the yarn becomes large according to Equation (1). This leads to an increase in F. When ϕ = 80°, the promotion of F is hindered because of a decline in the action of airflow on the yarn in the axis direction, in spite of the increasing action in circumference. The G variation with ϕ is similar to that of F, but the variation of G is very small (Figure 5(a)) because of the same total cross-sectional area of jet orifices in each nozzle. Therefore, F and η present the same trend with variation of ϕ, and η also reaches the maximum value at ϕ = 75° (Figure 5(b)). It is not necessary to increase ϕ above 75°. The results shown in Figure 5 are in good agreement with the previous study.¹³

Figure 5.

Effect of jet orifice angle ϕ on yarn suction performance at N = 3, d = 1.6 mm and θ = 60°: (a) yarn suction force F and mass flow rate of compressed air G; (b) yarn suction efficiency η.

Effect of passage diverging angle of nozzle θ

Figure 6 shows plots of the yarn suction force F, the mass flow rate of compressed air G and the yarn suction efficiency η at different passage diverging angles of nozzle θ. The other three geometrical parameters are fixed at N = 3, d = 1.6 mm and ϕ = 75°. In the range of θ < 60°, F increases with θ, and becomes highest at θ = 60°, as shown in Figure 6(a). When θ > 60°, F decreases with increasing θ. G shows a distribution opposite to F, and the variations of G are also not large and can be neglected.

Figure 6.

Effect of passage diverging angle of nozzle θ on yarn suction performance at N = 3, d = 1.6 mm and ϕ = 75°: (a) yarn suction force F and mass flow rate of compressed air G; (b) yarn suction efficiency η.

The diverging part of the nozzle is designed not only to provide a surface to generate a tangential velocity component of the injected airflow, but also to hinder the backflow from the outlets of the jet orifices produced owing to the expansion of the injected compressed air. A reduction of θ results in an increase in the backflow; this causes a decline in the velocity of entrained ambient air in the yarn inhalation tube. Therefore, F decreases. An over-large θ causes a highly turbulent condition near the throat. This is because more backflows are produced in the converging part of the Laval tube, since the outlets of the jet orifices are too close to the inner wall of the converging part. This lowers the intensity of the swirling flow, and causes F to decrease. F shows a distribution similar to η shown in Figure 6(b), because of the negligible variation of G. Thus the results of experiments suggest that the optimum value of θ is 60°.

Comparison with the previous studies

Effects of the number of jet orifices N and the jet orifice diameter d were not considered in the previous research, setting N = 4 and d = 2 mm.¹³ Under this condition, the rational geometry of the nozzle is ϕ = 75° and θ = 60°. In this study, an improved, more efficient YSG with the geometrical parameters of N = 3, d = 1.6 mm, ϕ = 75° and θ = 60° is achieved.

Conclusions

In order to improve a YSG with high performance and low energy consumption, 16 nozzles were made and relations between the nozzle geometry and the yarn suction performance were discussed. The rational geometrical parameters of the nozzle are obtained as follows: the number of jet orifices N = 3, the jet orifice diameter d = 1.6 mm, the jet orifice angle ϕ = 75° and the passage diverging angle of the nozzle θ = 60°. Effects of the geometrical parameters on the yarn suction performance were established. A smaller N reduces the conflict between jet streams and then increases the yarn suction efficiency η. Decreasing d contributes to greater η, but smaller yarn suction force F. In the range of Φ≤75°, increasing ϕ causes both F and η to increase. An appropriate θ promotes the yarn suction performance by helping the injected air to go forward smoothly and reducing backflow. The yarn suction efficiency is more rational for evaluating the yarn suction performance.

Footnotes

Funding

This work was supported by the Fundamental Research Funds for the Central Universities (No. JUSRP 31104 and No. JUSRP 51301A).

References

Kaneko A, Higashiya N and Hamasuna H. Yarn suction gun for producing nonwoven fabrics. Patent 91109278.1, China, 1991.

Yamaguti K and Takahashi S. Yarn suction apparatus. Patent SHO51-28424, Japan, 1976.

Sano T, Sekido T and Ogasawara M. Yarn-threading method and device. Patent 4844315, USA, 1989.

Miller CE. Yarn handling device. Patent 2667964, USA, 1954.

Ashby WC, Bunting WW Jr, Meagher R, et al. Improved yarn handling sucker gun. Patent 3094262, USA, 1963.

Ashby WC, Bunting WW Jr, Meagher R, et al. Fluid pressure method for transferring yarn. Patent 3156395, USA, 1964.

Bunting WW Jr, Meagher R, Swayne KG, et al. Yarn handling apparatus. Patent 3175290, USA, 1965.

Ishida

Okajima

. Flow characteristic of the main nozzle in an air-jet loom Part I: measuring flow in the main nozzle. Textil Res J 1994; 64: 10–20.

Richter HH. Yarn handling apparatus. Patent 3452910, USA, 1969.

10.

Vanderip HA. Yarn handling method and apparatus. Patent 3570339, USA, 1971.

11.

McFall AJ. Yarn-handling device. Patent 4181247, USA, 1980.

12.

Tseng C. Ultra-high speed suction gun. Patent 5857606, USA, 1999.

13.

Iemoto

Tanoue

Hosokawa

. Geometry effect of air suction gun on the yarn suction characteristics. J Textil Eng 2008; 54: 41–47.

14.

Iemoto

Tanoue

. Numerical simulation of airflow characteristics in air suction gun. J Textil Eng 2010; 56: 97–106.

15.

Iemoto

Tanoue

. Numerical analysis of the geometrical effects on the airflow characteristics of an air suction gun. J Textil Eng 2010; 56: 163–172.

16.

Iemoto

Tanoue

. Yarn posture in an air suction gun. J Textil Eng 2010; 56: 173–179.

17.

Iemoto

Tanoue

. Yarn motion in an air suction gun. J Textil Eng 2011; 57: 29–35.

18.

Finnemore

Franzini

. Fluid mechanics with engineering applications, 10th ed. New York: McGraw-Hill Companies, Inc, 2003, pp. 357–357.