Abstract: Based on the principle of porous jet diffusion and jet superposition, a dual-layer laminated structure was used to develop a wear-resistant throttle air volume control valve. It can replace the widely used throttling pipe and air volume control valve in the dust removal pipe network to balance the pipe network resistance, have better wear resistance, long service life, unlimited installation position and convenient adjustment. Keywords: Air flow control valve Throttle jet 1 Dust removal system Throttle problems and analysis In order to balance the resistance of the dust removal pipe network and adjust the air volume, the throttle system and the air volume control valve are widely used in the dust removal system. Throttle is usually installed in the pipe network is relatively short branches, its resistance coefficient is generally larger. The structure of the choke tube is shown in Fig. 1, its opening rate is fixed and can not be adjusted. Let the orifice of the throttle pipe have an opening rate of φ and the speed of the pipe v0, then the wind speed at the outlet of the middle core pipe is (1) where φ = A / A0, where A is the area of ​​the core pipe and A0 is the area of ​​the outer pipe . Generally, the opening rate of the throttle pipe is between 0.2 and 0.5, so that the wind speed v at the outlet of the intermediate core pipe is v = (2 ~ 5) v0 from the formula (1). When the speed in the pipeline is 16m / s, the maximum wind speed at the outlet of the core tube will reach 80m / s. If the throttle pipe installation location is not good (outlet and elbow, tee pipe fittings such as the distance of less than 5 to 10 times the diameter), such a high speed will greatly speed up the dust on the throttle after the elbow, tee Tube wear. Because the speed of wear the greatest extent, the amount of wear and speed is proportional to the third power [1]. In the WISCO sintering plant site observation shows that the outlet of the throttle tube near the 6mm elbow and tee, in a week or two the time was worn wear. Based on the above analysis shows that although the throttle can be effectively used to balance the pipe network resistance, but also has some limitations: First, the throttle opening rate can not be adjusted, and second, high-speed airflow at the exit of the throttle will result Behind the pipe wear and tear worse. Dust removal system is usually used to regulate the amount of air flow control valve branch and vacuum point. In general, air-flow control valves should be installed at each suction point in the system, even on branch lines fitted with throttles. Currently used in ventilation and dust removal system in the main type of air volume control valve flapper and butterfly type. If the airflow dust concentration, wear strong, and the air volume control valve opening is relatively small, flapper and butterfly valves have a common disadvantage is that the valve body, the valve core is easy to wear, or even connected with Straight pipes cause serious wear and tear. Air volume control valve is easy to wear the main reason is because the valve structure is unreasonable, resulting in sharp changes in the flow field, uneven air flow, causing dust on the valve and tube wear increased, as shown in Figure 2. In metallurgical enterprises, this situation can be seen everywhere, the newly installed air flow control valve, wear out quickly a week or two, resulting in greater economic losses. Data show that at present there is no low cost, good wear resistance of the air flow control valve. Some existing air volume control valve made of thick steel, and some expensive wear-resistant materials, this passive anti-wear, not only can not fundamentally solve the problem of wear and tear, but also greatly increased costs. This article describes the wear-resistant throttle air flow control valve with throttle and air volume control valve function, the two can be combined. 2 throttle wear air volume control valve structure and principle of wear-resistant throttle air volume control valve structure shown in Figure 3. It consists of the valve body, activities porous plate, fixed porous plate and opening adjustment device. The activities of perforated plate and fixed perforated plate openings exactly the same situation, there are two main types of openings, namely, the hole and the hole-shaped hole, as shown in Figure 4. The opening adjusting device is isolated from the dusty air current and adopts double gears and rack drives. This structure can not only prevent the opening adjusting device from malfunctioning due to the clogging of dust, but also can not easily rust to death. By turning the adjustment knob on the opening adjustment device, the movable porous plate can be driven to move left and right so as to achieve the purpose of balancing the resistance and adjusting the air volume. The opening of the movable perforated plate is the largest when the opening of the movable perforated plate is completely overlapped with the opening of the fixed perforated plate. When the opening of the movable perforated plate and the opening of the fixed perforated plate are completely dislocated, the opening of the valve is minimized. The opening adjustment device is equipped with an opening indicator, which can be quickly and accurately read out the current valve opening. The valve uses small holes (strip hole, circular hole) jet diffusion and superposition principle, the air flow in a short distance evenly mixed. When the airflow passes through the fixed porous plate and the movable porous plate, the parallel jets are superposed on each other and mixed in a confined space. Figure 5 shows two parallel jets superimposed on each other as an example: when two parallel jets are close, the jet development will affect each other. Before the confluence, each jet developed independently. After confluence, the jet boundaries intersect and interfere with each other to form a total jet. After the total jet has been fully developed, it can be uniformly mixed within a short distance, so that the velocity can be evenly distributed along the valve cross section. Generally, the width of the strip hole or the diameter of the circular hole takes 10mm, and the width of the hole bridge takes 10mm. The jet diffusion angle θ is generally between 2 ° and 16 ° [2] The well-mixed position is at a distance of x = b / tanθ (2) Substituting b = 15mm and θ = 12 ° into equation (2) yields x = 71mm. This shows that the use of porous structure, the use of small hole jet diffusion, superposition principle, the airflow through the wear-resistant throttle air volume control valve, less than 100mm in the distance can be evenly mixed, so you can avoid high-speed airflow on the valve body and valve After the pipe caused serious wear and tear. Secondly, due to the porous structure, vortexes are hardly formed at the intersection of the valve body and the perforated plate, thereby greatly reducing the wear of dust on the valve body. In addition, dust and the valve core (perforated plate) collision angle to avoid the easy to wear range. Dust angle of incidence has a greater impact on wear, when the incident angle of 20 ° ~ 30 °, the maximum wear [3]. 3 Conclusion wear-resistant throttle air flow control valve can replace the throttle and the general air volume control valve, and can be widely used in dust removal system. Its successful development, will bring greater economic and social benefits, with good application prospects. Compared with the throttle and the traditional air volume control valve (flap valve, butterfly valve), wear-resistant throttle air volume control valve has obvious advantages: (1) the structure is very simple and low cost. (2) wear resistance, long life, the general service life can be extended 3 to 5 times more. (3) The installation position is unlimited, without any adverse effect on the fittings behind it. (4) The valve with double gears and rack drives, not easy to rust, and the traditional plug-type air volume control valve is driven by a screw, easy to rust death. (5) easy to operate, easy to reach the purpose of air volume adjustment, and can quickly and accurately get the current valve hole rate. References [1] Yao Qun etc .. Dust pipe wear and abrasion-proof measures. Building thermal ventilation and air conditioning, 2000,1 [2] Tan Tianyou, Liang Fengzhen. Industrial ventilation and dust removal technology. Beijing: China Building Industry Press .1988.130 [3] Chen Wansheng et al. WISCO four burning dust removal system air volume balance debugging. Industrial Safety and Environmental Protection .2001,8
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