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包钢烧结φ250卸灰阀设计【10张CAD图纸+毕业论文】【答辩优秀】

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包钢烧结φ250卸灰阀设计

摘  要

电动蘑菇头式双层卸灰阀是烧结厂专用的一种卸灰装置，烧结机双层卸灰阀的作用是在保证不漏料的情况下,把台车底部从风箱漏下的烧结矿料粒,定时排到除尘皮带运输机上。它的使用性能直接影响到烧结机产量、作业率能否进一步提高。而φ250电动蘑菇头式双层卸灰阀结构简单、工作效率高、除尘量较大（3t/h）、具有双层结构密封性能好、占地面积小、适合在恶劣的环境中工作。因此，电动蘑菇头式双层卸灰阀在各钢铁厂得到广泛的应用。

在这次毕业设计中，主要是对电动蘑菇头式双层卸灰阀的传动部分进行设计，具体设计步骤分成一下几部分：进行传动方案的总体设计、传动零件的设计、轴系部件的设计以及金属的热处理和零件的磨损、密封与润滑。




关键词：卸灰阀；蘑菇头式；除尘；主传动

Design of sintering Φ250 dust valve in Baotou Steel Factory

Abstract

Electric cone type double dust valve is a special type of dust device in sintering plant. The double dust valve of the sintering machine is used to pledge not to leak materials,the sintering meterial from the Bellows which is at the bottom of the machine ,should be transport to the Belt Conveyor on time. It's direct influence of performance characteristics goes to sintering machine production and  that whether work rates have a further raising. Φ250 electric cone type double dust valve have simple structure,high working efficiency, comparatively large dust-clearing quantity ( 3t/h) , it have double structural sealing that can be good , little area of occupancy , and it suits to work in bad environment. Therefore, electric cone type double dust valve gets extensive application in each steel factory.

In this graduated design , it’s major is the design of the part of the transmission to  Electric cone type double dust valve, specific design step is divided into some parts of: the general design of transmission scheme, the design of transmission parts, the design of shaft parts as well as the heat treatment ,and of the wear of metal, the part of the seal and lubrication.




Keyword: Dust valve; Cone type; dust-clearing; Main transmission device



设计卸灰阀的有关参数

项目

序号设备性能参数数值单位备注

1烧结散料粒  度0~10mm

温  度<150℃

密  度1.7t/

2处理量3t/h

3阀工作周期28.6s

4重锤量46Kg


目   录


摘  要I

AbstractII

第一章 绪  论1

1.1  课题来源及课题设计的意义1

1.1.1 烧结厂粉尘来源1

1.1.2 烧结厂生产工艺中废气的产生2

1.1.3 污染物特点及其技术参数2

1.2 烧结厂废气治理所采取的措施3

1.2.1 烧结机废气除尘3

1.2.2 烧结机烟气中二氧化硫的治理3

1.2.3 烧结机尾除尘4

1.2.4 整粒系统除尘5

1.2.5 球团竖炉烟气治理5

1.2.6 生产工艺流程的改革6

1.2.7 烧结厂烟气冷却机废气的余热回收方式6

1.2.8 除尘技术装备水平和效果普遍提高7

1.2.9 烧结厂粉尘二次污染控制采取的措施7

1.2.10加强设计工作适应生产要求7

1.2.11加强操作和设备维护8

1.3 卸灰阀的分类及其工作原理8

1.3.1 卸灰阀的选用原则8

1.3.2 常见卸灰阀的结构及其工作原理9

第二章 传动装置的总体设计13

2.1 确定传动方案13

2.1.1 传动装置的组成13

2.1.2 合理确定传动方案13

2.1.3 确定减速器结构及其零部件13

2.1.4 选择电动机的型号14

第三章 传动零件的设计17

3.1  摆线针轮行星传动设计17

3.1.1 特点17

3.1.2 减速器的选择18

3.1.3 设计计算18

3.2 传动托阀摇臂轴的设计21

3.3 圆柱螺旋压缩弹簧的设计计算30

第四章 其余零部件的设计35

4.1 键的选择和键联结的强度计算35

4.1.1 减速器与拨盘轴静联结所用键35

4.1.2 上拨杆与轴静联接所用键35

4.1.3 托阀摇臂与轴联接所用键35

4.2 轴承选择与校核36

4.2.1 托阀摇臂轴左端轴承选择与校核36

4.2.2 托阀摇臂轴右端轴承选择与校核37

第五章 主要部件结构设计及金属的热处理38

5.1 箱体（焊接件）38

5.2 锥阀体（QT50-5）38

5.3 弹簧39

第六章 磨损、润滑与密封41

6.1 影响开启阀磨损的各种因素41

6.2 密封42

6.3 润滑（轴承的润滑）43

结  束  语45

参考文献47


第一章 绪  论

1.1  课题来源及课题设计的意义

烧结厂所产生的颗粒物对人体健康会产生一定的影响，其影响程度取决于颗粒物的浓度和在其中暴露的时间。研究数据表明，因上呼吸道感染、心脏病、支气管炎、气喘、肺炎、肺气肿等疾病而到医院就诊的人数的增加与大气中颗粒物浓度的增加是相关的。对患呼吸道疾病和心脏病的老人的死亡率研究表明，在颗粒物浓度一连几天异常高的时期内，死亡率就有所增加。[1]

粉尘（dust）一般指悬浮于气体介质中的微小固体颗粒，在重力作用下沉降，但在一段时间（甚至相当长时间）内能保持悬浮状态。它通常是由固体物质的破碎、研磨、分级、输送等机械过程，或土壤、岩石的风化等自然过程形成的。颗粒的形状往往不规则。颗粒的尺寸范围一般为1~200μm左右。其不仅对于人体、生物有生理危害，对机器设备也同样有害。[1]


内容简介：
Z. Tan, Y. Zhang, and S. Ford. “Decay of Rotational Airflow with Flow Conditioner in Larger Diameter Ducts for Dust Concentration Measurement using Isokinetic Sampling”. Agricultural Engineering International: the CIGR Journal of Scientific Research and Development. Manuscript BC 03 007. Vol. V. December 2003. 1Decay of Rotational Airflow with Flow Conditioner in Larger Diameter Ducts for Dust Concentration Measurement using Isokinetic Sampling Z. C. Tan, Y. Zhang, S. E. Ford Department of Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign, 1304 West Pennsylvania Avenue, Room 332, Urbana, Illinois 61801. Phone: (217) 244-6316, Fax: (217) 244-0323. Email: Abstract Within this study the decay speed of centrifugal device induced rotational airflow in round ducts and its conditioning for dust concentration measurement was investigated. Tests were conducted under room conditions at average Reynolds numbers within the range of 0.71.14x105. Duct diameters were 152 mm and 203 mm. Airflow in the ducts was found nonuniform and unsteady within the axial location to diameter ratio (x/D) of 10.5. The nonuniformity of axial airflow was nearly independent of the average Reynolds number. The study proved that it is impractical to decay the rotational airflow simply by using straight extension duct. A flow conditioner with minimal particle loss is needed to make the air flow uniform and steady. As a case study, a simple flow conditioner was tested. It decayed the rotational airflow to an acceptable level within x/D=2. The measured dust concentrations at 5 radial locations at x/D=2 were uniform: /1% for total mass concentration, and /10% for all the particles smaller than 10 m. Keywords. Rotational airflow, airflow conditioning, dust sampling Introduction Cyclones have been widely used in many agricultural engineering applications. They were primarily used for larger particle separation (Carpenter 1986) or dust sampling at low airflow rates (Crook 1995, Lacey and Venette 1995). Although cyclones have been well industrialized and commercialized, uncertainties remain and they encourage researchers to further study the particle separation mechanism. Recent advances in this area indicate that it is very likely to be further developed for separating respirable particles at low cost and higher airflow rates (Zhang et al. 2001, Wang et al. 2002). During the investigation process, dust separation efficiency of a cyclone needs to be measured. With the increasing concern of respirable particles in environments, air-cleaning devices are often tested based on particle size (ANSI/ASHRAE 1999). Isokinetic sampling systems are often used for dust concentration measurements in ventilation ducts. In order to minimize the anisokinetic effects (Hinds 1999), the sampling nozzles should be correctly aligned to match the Z. Tan, Y. Zhang, and S. Ford. “Decay of Rotational Airflow with Flow Conditioner in Larger Diameter Ducts for Dust Concentration Measurement using Isokinetic Sampling”. Agricultural Engineering International: the CIGR Journal of Scientific Research and Development. Manuscript BC 03 007. Vol. V. December 2003. 2air velocity profile. Consequently rotational airflow exiting a cyclone has to be conditioned to an acceptable steadiness before air velocity profile can be determined and dust concentration can be measured. In addition, uniform airflow is also preferred to reduce other sampling errors. It is a challenge to pick a representative sampling point in the rotational airflow. A multipoint sampling system could be employed. One apparent disadvantage is that many sampling heads will inference with the airflow pattern and introduce a significant error factor. Another disadvantage is that more sampling points require more sampling tubes, and consequently increase particle loss in sampling tubes. Therefore, a single point sampling system is preferred. The upstream airflow is not rotational. A single sample point is acceptable. However, before a single downstream sample point can be taken, we must condition the rotational airflow to an acceptable uniformity. ANSI/ASHRAE (1999) standard requires that qualification tests shall be performed for uniformities of air velocity and aerosol in the test duct. The ANSI/ASHRAE standard also recommends bending the test duct 180o to bring the downstream sample locations relatively close to the upstream location, which allows short sample lines to the particle counter. It reduces the overall length of the test duct, facilitating its placement within the test room. However, it should be noted that this introduces another error factor. The bending could create rotational airflow. This swirl poses challenges in accurate measurements of airflow rate (McManus et al. 1985, Laribi et al. 2001), and maybe consequently, the dust concentration. Two methods are often considered for airflow conditioning. One is the use of long straight extension ducts and another is the use of flow conditioners. The rotational airflow in a duct will decay to an acceptable level provided the straight duct is sufficiently long. The question is how long it should be. If the duct is too long, excessive space is needed to setup the measurement system, and more importantly, there might be too much particle loss on the inner surface of the duct. Studies on rotational flow have been reported since the 1950s. The majority of these studies dealt with rotational flows in burners and air mixing in combustion areas. Only few of them are about decay of rotational flows. One of the early studies on rotational flow in ducts is an analysis of rotational flow of a constant property fluid in a straight duct of circular cross-section by Talbot (1954). The subject was steady and laminar flow in ducts. Kreith and Sonju (1965) later presented the average decay of tape-induced fully developed turbulent swirl in water flow through a duct. The duct was 25.4 mm in diameter and 2,540 mm long. The twisted tape inducers consisted of 0.85 mm thick galvanized steel strips. The experiments were done with Reynolds numbers from 104 to 105. It indicated that the rate of decay depended on the axial Reynolds number: the decay rate increased as the Reynolds number decreased, but the decay was found to be independent of the initial swirl intensity. It was observed that turbulent swirl decayed to about 10-20% of its initial intensity at an axial location to diameter ratio (x/D) of 50. Recently Laribi et al. (2001) experimentally studied the decay of swirling turbulent gas (petroleum) flow in a long duct. The inner diameter of the duct was 100 mm. The swirling flow was generated by double Z. Tan, Y. Zhang, and S. Ford. “Decay of Rotational Airflow with Flow Conditioner in Larger Diameter Ducts for Dust Concentration Measurement using Isokinetic Sampling”. Agricultural Engineering International: the CIGR Journal of Scientific Research and Development. Manuscript BC 03 007. Vol. V. December 2003. 390-degree elbow. Tests were conducted at Reynolds number ranging from 3x104 to 1.1x105. It was observed that the flow was fully developed at x/D=90. The decay of a swirling flow of nitrogen gas in long ducts was reported by McManus et al. (1985). Tests were conducted under ambient temperature and pressure of 40 kPa at Re=8x105 to 1.4x106. The decay of 60 degrees of swirling across a 100 mm smooth-walled duct measured at x/D=0, 10, 33, and 70. It was found that at x/D=70, the decay was 59%. Based on 6 sets of experimental data, they gave a fit decay equation, Percent Decay = 0.954Dx0126. 0exp (1) where x is the axial location in the duct, D the inner diameter of the duct, and x/D the axial location to diameter ratio. From this equation, we can predict that the decay can be reduced to 10% at x/D=200. Although the exact x/D numbers are different for the rotational flow to become fully developed, the above representative studies have shown that the duct has to be very long to reduce swirl to acceptable levels. In a laboratory, it might not be a practical solution for eliminating possible measurement errors attributed to swirl simply by using long ducts. Objective Among the limited amount of literature on decay of rotational fluid flow, few of them are about decay of rotational airflow in long ducts, and most of them were conducted in ducts less than 100 mm in diameter. The objective of this research is to study the decay of a rotational airflow created by a rotation device (i.e. centrifugal fan or cyclone) in ducts larger than 100 mm in diameter. It will be proved that a long duct is impractical, and a flow conditioner has to be used to condition the rotational airflow. As a case study, a flow conditioner with a large open ratio and with smooth surfaces was made and its effect on flow conditioning was tested. It is also expected that researchers who measure dust emission rate downstream of exhausting fans can find useful information from the results herein. Experimental Methods Ducts used in this research were commercial galvanized steel ducts with inner diameters of D= 152 mm and 203 mm. Maximum length of the ducts was 2,100 mm. The maximum length to diameter ratio, L/D, was about 10.8 due to space limitations in the laboratory. Axial velocity profile was measured using an anemometer from TSI, Inc. The anemometers measurement range was 0 to 20.3 m/s, with an accuracy of 5.0% of reading or 0.025 m/s whichever is greater. In this paper, airflow direction is our major concern for isokinetic sampling purpose. We wanted to condition the rotational airflow into a one-dimensional airflow. Therefore, only the axial velocity profile was measured. If axial velocity is not steady or uniform, the total velocity is Z. Tan, Y. Zhang, and S. Ford. “Decay of Rotational Airflow with Flow Conditioner in Larger Diameter Ducts for Dust Concentration Measurement using Isokinetic Sampling”. Agricultural Engineering International: the CIGR Journal of Scientific Research and Development. Manuscript BC 03 007. Vol. V. December 2003. 4not steady or uniform. While rotating the anemometer during test, other velocity components were obvious if the axial flow was not steady or uniform. On the other hand, other two velocity components were not apparent when the axial flow was steady and uniform. Samples were taken at different axial locations (x/D). At each location, velocities were measured at different radial locations. The rotational airflow was generated with an in-line centrifugal fan. The airflow rate was adjusted with a variable transformer. The transformers maximum output settings were 120 V and 140 V. It could be adjusted from 0% to 100% of each maximum output. In this project, seven voltage levels of fan power were used: 90% and 100% of 140V, and 60%, 70%, 80%, 90% and 100% of 120V. For each power level and each x/D in duct, axial air velocities at up to 13 evenly distributed points were measured, with increase of 12.7 mm or 25.4 mm (see Figure 5). To verify the conditioning effect of the simple airflow conditioner, dust spatial distribution downstream was measured using an isokinetic sampling system. Particle concentrations were measured using APS 3321 (TSI, Inc.). The sampling points were 2D downstream of the flow conditioner, and their relative radial locations are shown in Figure 1. The corresponding radial locations of #1, #2, #3, #4 and #5 are 1/3 R, 1/6 R, 1/6 R, 7/12 R, and 5/6 R, respectively. 10 samples were taken at each of the 5 radial locations. The tests were conducted under Reynolds number of Re=2.2x104. D2D2D#2#4#3#5#1Flow conditioner Rotational airflow R Figure 1. Particle sampling locations Standard Arizona test dust was dispersed using a turntable dust generator. The size distribution of particles entering the air stream is shown in Figure 2. As seen in the graph, 95% by volume are less than 12 m with a mass median of 4.8 m. Z. Tan, Y. Zhang, and S. Ford. “Decay of Rotational Airflow with Flow Conditioner in Larger Diameter Ducts for Dust Concentration Measurement using Isokinetic Sampling”. Agricultural Engineering International: the CIGR Journal of Scientific Research and Development. Manuscript BC 03 007. Vol. V. December 2003. 50%25%50%75%100%0.5231.0372.1294.3718.97718.434Particle diameter (dp), umCummulative Volume Figure 2. Particle size distribution Results and Discussion In this paper, a coordinate system as illustrated in Figure 3 is used. Axial direction is x, and radial direction is r. The length, radius and diameter of the duct are L, R, and D, respectively. At any axial location x, the velocity at different radial location r is Vr. The velocity on the centerline is Vc. The average velocity at x is V. D L x r r R x Vr Vc Centerline Figure 3. Illustration of the parameters referred in this paper In this paper, dimensionless parameters including Reynolds numbers, nonuniformity parameter, and dimensionless velocity are used for data analysis. For airflow inside a duct, Reynolds number is defined as (ANSI/ASME 1979), Re=vVl (2) Z. Tan, Y. Zhang, and S. Ford. “Decay of Rotational Airflow with Flow Conditioner in Larger Diameter Ducts for Dust Concentration Measurement using Isokinetic Sampling”. Agricultural Engineering International: the CIGR Journal of Scientific Research and Development. Manuscript BC 03 007. Vol. V. December 2003. 6where: V is the average fluid velocity (m/s). , l a characteristic dimension of the system in which the flow occurs (m), and v the kinematic viscosity of the fluid (m2/s). The characteristic dimension is the inner diameter of the duct, D. The kinematic viscosity is 1.5x10-5 m2/s for room air at 20 oC and 1 atm. Average Reynolds numbers are calculated using the averaged axial velocities. The average Reynolds numbers in ducts in our tests were within the range of 0.7-1.14x105. 1. Effect of centrifugal device location The airflow pattern inside a duct created by pushing air into a duct is different from pulling air out. Curves in Figure 4 are dimensionless velocities, the velocity at r over the average velocity (Vr/V), against dimensionless radial location, radial location r over the radius of the duct (r/R). For the example cases in Figure 4, the average Reynolds number was 1.14x105. The effects under other operation conditions were similar. When the fan was pulling air out of the duct, Vr/Vs at all the measured locations, even at x/D=0.46, were very close 1. It indicates that airflow was uniform. However, when the duct was downstream the device, Vr/Vs at most of the measured points are way off unity, even at x/D=8.8. It indicates that downstream centrifugal device does not create strong rotational flow in duct, but upstream centrifugal device does. 0.01.6-1-0.500.51r/RVr/VPullx/D=0.46Pullx/D=2.3Pushx/D=5.2Pushx/D=8.80 Figure 4. Effect of device location (pulling air out of and pushing air in duct) (r is the radial location, R is the Radius of the duct, Vr is the velocity at r, V is the average velocity, x is the axial location, and D is the diameter of the duct). Since the rotational effect was negligible when the duct was upstream of our fan, only those cases where the duct was downstream of the fan are presented below. An example velocity profile is first given to visualize the airflow inside the ducts with and without flow conditioner. Z. Tan, Y. Zhang, and S. Ford. “Decay of Rotational Airflow with Flow Conditioner in Larger Diameter Ducts for Dust Concentration Measurement using Isokinetic Sampling”. Agricultural Engineering International: the CIGR Journal of Scientific Research and Development. Manuscript BC 03 007. Vol. V. December 2003. 7Then the uniformity and steadiness of the airflow are compared. At the end, as a case study, the dust concentration distribution after the flow conditioner is presented. 2. Axial velocity profile Axial velocity patterns were similar for all 7 average Reynolds numbers (fan levels). Figure 5 is an example that illustrates the axial velocity profile in ducts with and without flow conditioner at different x/D. The corresponding average Reynolds number was 1.14x105 (140V x 100% fan power). The flow conditioner was made of galvanized steel sheet metal. It had 4 vanes with L/D=2. When a flow conditioner is used, we have to take into consideration the particle loss on the flow conditioner. Particle loss on the flow conditioner should be minimized as much as possible. Therefore, the open area of the conditioner should to be as large as possible, and the surfaces should be as smooth as possible. Flow conditioners that are made up of multiple small tubes (i.e. 1 mm diameter) were not considered. The sheet metal is about 1 mm thick with smooth surface. The open ratio of a conditioner in a 152 mm duct is about 98.3%. Considering the large open ratio and smooth surface of the vanes, and small downstream particles, it is expected that the pressure drop and particle loss were minimal. This should be verified. x/D=5.17x/D=8.83x/D=10.75 xs/D=0.67 xs/D=1.4xs/D=2.92xs/D=5 Figure 5. Decay of rotational airflow in a long duct without and with a flow conditioner 3. Nonuniformity As mentioned above, at each axial location (x/D), velocities at about 10 radial locations (r/Rs) were measured. Then we have an average velocity (V) and a standard deviation () for each x/D. A nonuniformity parameter was defined to quantitatively compare the rotational effect at different x/Ds under different operational conditions. The nonuniformity parameter is defined as the standard deviation over the average value of the velocities. The higher the standard deviation over the average, the higher the level of nonuniformity is. a) Without Flow Conditioner b) With Flow Conditioner Z. Tan, Y. Zhang, and S. Ford. “Decay of Rotational Airflow with Flow Conditioner in Larger Diameter Ducts for Dust Concentration Measurement using Isokinetic Sampling”. Agricultural Engineering International: the CIGR Journal of Scientific Research and Development. Manuscript BC 03 007. Vol. V. December 2003. 8Figure 6 shows some examples of the variation of /V with average Reynolds number. In most cases of rotational airflow, /V dropped slightly with average Reynolds number. For conditioned airflow, the variation is negligible. For any fixed point in the duct, the value of /V did not change significantly with fan power. This also explained that the velocity profile mentioned above was similar at different average Reynolds numbers (velocities). Therefore, only the average /V was used for each Reynolds number to quantitatively illustrate the nonuniformity at each x/D. Figure 7 is based on this idea. 0.00.46000080000100000120000Average Reynolds Number/Vx/D=2.5 w/ocond.x/D=5.2 w/ocond.x/D=8.8 w/ocond.x/D=0.67 wcond.x/D=1.4 wcond.x/D=2.9 wcond. Figure 6. Nonuniformity of velocity under test conditions (V is the average velocity, is standard deviation of velocity. x/D is the axial location over diameter of the duct) Figure 7 compares the nonuniformity of airflow in duct. Each point in Figure 7 is the average of 7 values of /Vs as shown in Figure 6. Within the accuracy in the tests, /V of air velocities at any axial location in round ducts was higher than 0.1 (or 10%) (for x/D2/3) is always less than 0.1. The experimental results here show that airflow approached uniformity level of 0.05 (5%) after x/D=1.5. On the other Z. Tan, Y. Zhang, and S. Ford. “Decay of Rotational Airflow with Flow Conditioner in Larger Diameter Ducts for Dust Concentration Measurement using Isokinetic Sampling”. Agricultural Engineering International: the CIGR Journal of Scientific Research and Development. Manuscript BC 03 007. Vol. V. December 2003. 9hand, even with a flow conditioner, it is not recommended to take samples right after the conditioner. Taking samples at x/D1.5 after the flow conditioner is a safe choice, unless it is impractical like in the situations reported by Marsh et al. (2003). The fitting curve gives the relationship between /V and x/D as, =V0.081-0.33Dx (R2=0.89) (4) 0.00.4036912x/D/Vw/o Flow Cond.With Flow Cond. Figure 7. Nonuniformity of velocity over x/D for flow with and without flow conditioner (V is the average velocity, is standard deviation of velocity. x/D is the axial location over diameter of the duct) 4. Steadiness Another parameter to evaluate the effect of the flow conditioner is flow steadiness. In this paper steadiness of the flow is characterized using centerline dimensionless velocity, Vc/V. Where, Vc is air velocity at the centerline, and is the average velocity at x/D. It shows the velocity change along the duct. For tested conditions without flow conditioner, the centerline axial velocity keeps increasing along the duct length (see Figure 5). Figure 8 gives an example when average Reynolds number is 1.14x105. It shows that the centerline velocity approached the average velocity as x/D increased. For airflow without flow conditioner, the axial velocity kept increasing and approaching steady state, but it did not reach steady state within our test conditions (x/D50 (tested) x/D=200 (Predicted from fitting equation) x/D=90 (tested) x/D10. (x/D2 with flow conditioner) Table 1 shows that rotational flow exists in many general engineering applications. Rotational flow could be created by, but not limited to, 1) bending vanes, such as vanes used in cyclones, 2) sudden changes in flow direction, including 90o bends (McManus et al. 1985) and double 90o elbows (Laribi et al., 2001), and 3) air flow downstream of a centrifugal device such as a centrifugal fan. The rotational airflow will affect the accuracy in airflow rate measurement using an orifice meter (Laribi et al., 2001) as well as dust concentration measurements using isokinetic sampling techniques, as addressed in this paper. Z. Tan, Y. Zhang, and S. Ford. “Decay of Rotational Airflow with Flow Conditioner in Larger Diameter Ducts for Dust Concentration Measurement using Isokinetic Sampling”. Agricultural Engineering International: the CIGR Journal of Scientific Research and Development. Manuscript BC 03 007. Vol. V. December 2003. 13Summary and Conclusions This research investigated decay of centrifugal device created rotational airflow in round ducts under room condition. An example velocity profile was first given to visualize the airflow inside the ducts with and without flow conditioner. Then the uniformity and steadiness of the airflow were compared. As a case study, the dust concentration distribution after the flow conditioner was presented. The following conclusions can be drawn from this study: 1. Centrifugal device has negligible effect in creating rotational flow on upstream airflow in round ducts. The same device can create very strong nonuniform and unsteady rotational airflow in downstream ducts. 2. Once a rotational airflow is created in a duct, it is impractical to lessen it to an acceptable level simply by using long ducts. 3. The nonuniformity parameter of the airflow at certain point in a duct is nearly independent of the average Reynolds number. When /0.05, the airflow is considered uniform. 4. A simple flow conditioner can significantly reduce the airflow swirl. The flow conditioner with length to diameter ration (L/D) of 2 lessens the rotational airflow to an acceptable level quickly within x/D=2. Duct concentrations at 5 radial locations at x/D=2 downstream the conditioner was observed uniform (/0.01). On the other hand, it is not recommended to take samples right after the flow conditioner. References ANSI/ASME MFC-1M-1979. Glossary of terms used in the measurement of fluid flow in pipes. ANSI/ASHRAE Standard 52.2-1999. Method of testing general ventilation air-cleaning devices for removal efficiency by particle size. Carpenter, G. A. 1986. Dust in Animal indoor environments-Review of Some Aspects, Journal of Agricultural Engineering Research. 33: 227-241. Crook, B. 1995. Inertial samplers: biological perspectives, in Bioaerosols Handbook (edited by Cox and Wathes), chapter 9, Florida: CRC Press, Inc. Hinds, W. C. 1999. Aerosol Technology: Pro
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