How to effectively reduce the air consumption of air-jet looms

How to effectively reduce the air consumption of air-jet looms

The air-jet loom is the fastest-developing shuttleless loom in recent years, but its energy consumption is much greater than other shuttleless looms, which increases production costs. The energy consumption of air-jet looms mainly depends on the amount of air consumption, so reducing air consumption is an issue that all factories attach great importance to.

　　The weft insertion system of the air-jet loom includes: main nozzle, auxiliary nozzle, special-shaped reed, solenoid valve and air storage tank, etc. The main way to reduce air consumption should be from the above aspects.

　　 1. Correctly adjust the best position and air pressure of the main nozzle

　　 Poor installation of the main nozzle position will increase the spread of the air flow it emits, affect the weft yarn into the shed, and waste air consumption. The installation position of the main nozzle mainly depends on the distance between the main nozzle and the first piece of special-shaped reed, and the calculation is usually based on the following formula: ds=6.8 (a.s+0.147do) (s—the measured point is from the nozzle outlet Distance, that is, the range, a—turbulence factor of the nozzle, do—the diameter of the nozzle outlet, ds—the diameter of the jet cone at the section s from the nozzle outlet). In order to make the jet flow into the special-shaped tank as much as possible, calculating ds is of great reference value. In actual installation, the s value can be adjusted by observing the size of the airflow cone entering the special-shaped reed trough through a stroboscope.

　　In the process of weft insertion, the speed of the weft yarn is accelerated by increasing the speed of the airflow, which is determined by the pressure. Therefore, the determination of the pressure must be based on the comprehensive consideration of the quality, number, fabric width, and vehicle speed of the used weft. When adjusting the pressure, it is necessary to observe whether the actual arrival time of the weft is consistent with the set arrival time, and adjust the main nozzle pressure to the minimum limit with less weft breaks, no loose edges, weft shrinkage and other defects. If the pressure is too high, even if the air consumption increases, the weft yarn will be blown off due to the rapid untwisting, forming a weft break. Under the premise of meeting the normal flight requirements of the weft yarn, reducing the main jet pressure can not only save air consumption, but also reduce the flying speed of the weft yarn, extend the flight angle of the weft yarn, reduce the tension of the weft yarn during the flight, and meet the requirements of the weft yarn. Single strong requirement. The relationship between the pressure of the main nozzle and the flying angle of the weft is shown in Figure 1 (the tested variety is C14.5/14.5472/236160cm poplin). It can be seen from the figure that as the main jet pressure increases, the flight angle of the weft decreases. When the pressure increases to a certain value, its effect on the flight angle of the weft decreases. The jet time of the main nozzle should be as small as possible under the condition of weft insertion, which is not only helpful for reducing weft breakage, but also for reducing air consumption.

How to effectively reduce the air consumption of air-jet looms

　　 2. Correctly adjust the process parameters of the auxiliary nozzle

　　 The role of the auxiliary nozzle is to stretch and straighten the weft to keep the initial speed and fly over the shed without twisting. When the loom is operating normally, the air consumption of the auxiliary nozzle accounts for about 75% of the air consumption of the entire loom. Therefore, to reduce air consumption and achieve the purpose of saving gas and energy, it is particularly important to correctly adjust the machine process parameters (air pressure, spray time, installation position) of the auxiliary nozzle.

　　1, auxiliary injection pressure

During the flight of the weft, not only must the air velocity of the auxiliary nozzle be greater than the initial velocity of the weft, that is, the flying speed of the weft (that is, the flying speed of the weft), but also the head end of the weft must always be under the action of high-speed airflow. The auxiliary air jet pressure is greater than the main air jet pressure. At the same time, as the head end of the weft is flying forward, the auxiliary nozzle must open and close the air supply valve in order to prevent the weft from being crowded. In actual production, the auxiliary nozzle pressure is usually determined by adding 0.02~0.03MPa to the fixed main nozzle pressure, but attention should be paid to reduce the weft yarn breakage and save air consumption.

　　2, auxiliary spray time

　　The method to determine the auxiliary spray time is to observe with a stroboscopic instrument, and the air supply time of each group of auxiliary spray is required to be ahead of the time when the weft yarn reaches each group of auxiliary nozzles, that is, the advance angle is generally 10°-20°. About 20° before the end of weft insertion, the main nozzle terminates the air supply, so that the weft yarn is no longer drawn by the airflow of the main nozzle in the final stage of the flight. The weft stretches to the right of the fabric edge. However, the closing time of the last set of auxiliary nozzles does not need to be extended too much, because the closing time is extended to about 20° after the arrival time, and the auxiliary nozzle nozzle is already under the lower warp yarn, which has no effect on the weft yarn, which is not conducive to saving air. Consumption. Generally, the spray time of the auxiliary nozzle is selected between 60° and 80°. Figure 2 Time control of main nozzle and auxiliary nozzle air flow and actual flight curve of weft yarn. It can be seen from the figure that the auxiliary nozzle time control should ensure that the actual flight curve of the weft yarn is within the effective air control range of each solenoid valve, and the opening time of the first auxiliary injection solenoid valve must be basically the same as that of the main nozzle before the weft yarn flight reaches stable state.

　　3, installation location

In order to make the auxiliary jet flow into the center of the special-shaped reed trough and meet the main jet flow accurately and early, the auxiliary nozzle should be installed on the sley and its orifice axis should be upward to form a jet angle a (total 8°) ), the backward oblique constitutes the spray direction angle β (about 5° in total). If β=0°, it should be compensated by the installation angle of the nozzle. By measuring the a and β angles of imported and domestic auxiliary nozzles (10 samples for each), the results show that a and β angles are different: (1) The standard deviation of spray angle a is 0.44 and 0.47; (2) The standard deviation of the spray direction angle β is 0.42 and 0.57. It can be seen that the auxiliary nozzles should be grouped and matched according to the deviation of a and β. At the same time, the a and β capture angles should be adjusted one by one, so as to make the actual flow velocity centerline of each auxiliary nozzle coincide with the incident angle when the special-shaped reed groove and the main jet flow centerline meet each other, so as to obtain the best effect. In order to quickly and accurately complete this adjustment, Xi'an 213 has successfully developed an auxiliary nozzle on-machine adjuster based on similar foreign products. Since the regulator can directly receive the airflow signal in the reed, the optimal installation position of the auxiliary spray can be determined, the airflow can be effectively used, and the effect of saving air and energy is obvious. The effect of Zhengzhou Simian's on-machine adjustment using this adjuster is shown in Table 1. The values ​​in the table show that the adjusted A group auxiliary nozzle not only has a lower working pressure than the unadjusted group B auxiliary nozzle, but also the main The working pressure of the nozzle is also reduced, and a considerable gas saving effect has been achieved.

How to effectively reduce the air consumption of air-jet looms

　　4, auxiliary spray type

　　 The shape and size of auxiliary nozzles are similar to each other depending on the model, sley structure and the shape of the special-shaped reed groove. Therefore, they are generally classified according to the shape and number of spray holes. Common single holes, double holes, multiple holes, round holes, square holes, etc. It is generally believed that the multi-hole auxiliary nozzle composed of 19 small holes with a diameter of 0.05mm and arranged in a regular hexagon is better than the single-hole type in terms of air flow. Therefore, the selection of this auxiliary spray is beneficial to reduce air consumption. .

　　 In short, the indicators for evaluating auxiliary nozzles mainly include three content: outlet wind speed, range (clustering), geometric accuracy (a, β angle consistency). In other words, an auxiliary nozzle with exquisite processing and excellent process performance should have the characteristics of fast spraying, long spraying and good quality.

　　 3. Correctly adjust the solenoid valve action time and working voltage

The solenoid valve that controls the nozzle switch on Toyota Loom uses overexcitation technology. When opening, first add overexcitation voltage (48V) to reduce the time for the initial output air pressure to rise from 0 to 90% of the set output air pressure, that is, the response time of electromagnetic opening . After the valve is opened, the input voltage drops to 15V to maintain the voltage, which can also reduce the time required for the output air pressure to drop by 50% from the set value, that is, the response time for the solenoid valve to close. This can increase the response speed of the solenoid valve to meet the needs of high-speed operation of the loom. At the same time, the opening time is slightly reduced, which is beneficial to saving air.

　　 It can be seen from the above that after the solenoid valve is energized, the valve body does not open immediately, but has an action process. For example, on the Tsudakoma loom, the solenoid valve starts to open to the full opening time is 0.06s, and the air flow from the solenoid valve to the nozzle is about 20.01s, so the air flow at the nozzle from 0 to the maximum time is 0.07s , During the closing time of the valve body, the air flow change rule is shown in Figure 3. It can be seen from the figure that the solenoid valve has a delay time when it is opened and closed. The effective injection time does not include the delay, that is, when the valve is opened, the pressure reaches 90%, and when it is closed, the pressure drops to 50%. This period is the effective injection time. When the action time of the main and auxiliary nozzles is shortened, that is, the effective injection time is shortened, and the compensation angle and lag angle remain unchanged. In fact, the shortened air injection time should be the bc section in the figure, not ab and cd, so The air consumption for weft insertion should be bc×be part, not cf(ef+ad)/2 part. Knowing this rule, when we set the opening and closing time of the main and auxiliary nozzles, we should open it by a compensation angle and close it by a lag angle. In order to save air consumption, the main and auxiliary nozzle spray time should be adjusted.

How to effectively reduce the air consumption of air-jet looms

　　 Fourth, the auxiliary injection adopts segmented air supply

　　 Because during the weft insertion process, when the weft yarn is flying in each section, the mass increases as the length of the weft insertion increases, and the flow velocity of the required weft-carrying airflow also needs to increase accordingly. The auxiliary nozzles should be supplied separately by two air storage cylinders. In addition, the main nozzle is closed when the weft is coming out of the shed. Therefore, the air pressure of the auxiliary nozzles in the right groups should be increased to prevent the weft from falling. In this way, separate air supply can separately control the pressure of the two weft insertion airflows, which can greatly reduce air consumption and also help stabilize the flight of the weft yarn.

　　 5. Reasonable selection of loom speed

　　The speed of air-jet loom is usually above 600r/min, and the exhibition speed can reach 700 or even 1000. Some people think that the loom is driven at 600r/min as a high level, and only at 600r/min is a low level. However, to determine the speed of the loom, many factors must be considered. In actual production, the speed of the loom is not as high as possible. It should be determined according to the specific conditions of each factory.

　　According to the information obtained by the author, there are 156 air-jet looms in a factory with a speed of 500～630r/min. There are three air compressors with 35m3, 38.7m3 and 64m3 air supply per minute. Limited to the lack of power supply from the grid, only two air compressors can be operated, which is only 102.7m3 (38.7+64) based on the maximum air supply. According to actual tests, the air consumption of each single machine is as high as 0.92m3/min for polyester-cotton poplin, feather-proof cloth and other varieties. Therefore, under the condition of a total air supply of 102m3, the factory can only normally operate about 120 looms. Production capacity is emptied.

Under other production conditions and the external factors remain basically unchanged, the actual test shows that a certain type of weft yarn is 18.5×2tex strand. When the speed is 600r/min, the air consumption of a single machine is 0.8m3/min, and the speed drops to The air consumption of a single machine at 500r/min is 0.62m3/min. It can be seen that when the speed of the loom increases from 500r/min to 600r/min, the air consumption increases by 37.1% when the speed is increased by 20%. In other words, the air-jet loom's air consumption growth rate and the loom's rotational speed growth rate are not simply linear. This is because the increase in air consumption on the one hand increases with the increase in the weft insertion rate (increased speed); in addition, due to the increase in speed, although the weft passing through the shed relative to the spindle rotation angle remains unchanged, the weft flight speed must be increased. The increase in the flying speed of the weft is actually achieved by increasing the air supply pressure. Therefore, the increase in the weft insertion rate and the increase in the air supply pressure, two factors lead to a greatly increased air consumption with the increase in the speed of the loom.

In view of the fact that the compressed air that was originally available for 10 looms at 600r/min can be used by 13.7 looms at 500r/min, and the factory has the specific situation of shutting down vehicles due to insufficient air supply, it was decided Reduce the speed of the original 60 600r/min looms to 500r/min, while adding 20 looms. As a result, the total output has not decreased, but increased. At the same time, power consumption has not increased due to the addition of machines. In addition, due to the decrease in speed, the requirements for the quality before weaving and the quality of the original yarn have decreased, the production efficiency has increased, and the machine material consumption has decreased. The number of blocking machines has also increased due to the increase in production efficiency. The total number of workers has not exceeded the original number of workers. Finally, another harvest that has not been considered in advance has been achieved: the original 600r/min loom, the auxiliary nozzle pressure is generally 0.45MPa At this time, the air supply pressure should not be less than about 0.5MPa, otherwise the shrinkage fabric will occur. On the 500r/min loom, the auxiliary spray pressure is generally about 0.4MPa, and the air supply pressure can be reduced to about 0.45MPa. The total air output remains unchanged. When the air consumption increases, the air supply pressure decreases. If the control air supply pressure is not lower than a certain set value, it will not cause the production of weft defects. In fact, at the peak of the plant's consumption, the actual gas consumption reached 122m3/min, and the gas supply pressure dropped to 0.47MPa at this time. This increased gas production compensates for the increased gas consumption due to the increase in efficiency after the speed drops. Through this adjustment of vehicle speed, the actual daily output of the plant has increased from 29,000 meters/day to 32,000 meters/day, and satisfactory results have been achieved.

　　 Six, summary

　　In the weft insertion system of the air jet loom, the main nozzle, auxiliary nozzle, solenoid valve and other respective technological performance and their installation position among each other, the action time is an important factor to ensure the smooth flight of the weft insertion and reduce air consumption. On the premise of not affecting the normal flight of the weft, reducing the air pressure of the main and auxiliary nozzles as much as possible and extending the flight angle of the weft are the keys to reducing air consumption. Excessive air pressure not only increases air consumption, but also breaks the weft yarn. Each factory should also reasonably select the speed of the loom according to the comprehensive factors such as the type and quantity of air compressors and air-jet looms, and the variety of fabrics produced, in order to maximize the utilization of compressed air.