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Numerical investigation of three-dimensional heat transfer in traveling wave amplifier collector with input power of 900 and 3000 watts

Number of pages: 155 File Format: word File Code: 32340
Year: 2012 University Degree: Master's degree Category: Facilities - Mechanics
Tags/Keywords: 3D heat transfer - Collector - heat transfer - Microwaves - TWT lamps - Wave amplifiers - Wave lamp
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  • Summary of Numerical investigation of three-dimensional heat transfer in traveling wave amplifier collector with input power of 900 and 3000 watts

    Master's Thesis in Mechanical Engineering (Energy Conversion Orientation)

    Abstract

    Numerical investigation of three-dimensional heat transfer in wave amplifier collector with input power of 900 and 3000 Watt

     

     

     

    The traveling wave lamp[1] is one of the types of microwave amplifiers. This lamp consists of five main parts, which are electron gun, slow wave structure, wave input and output connectors, magnetic concentrator system and collector. The electron beam emitted by the electron gun, passing through the slow wave structure, spends a percentage of its energy to amplify the microwave wave and converts the rest of it into heat when it collides with the collector body. The collector consists of an internal body that is separated from the external body by ceramics that are responsible for electrical isolation. The aim of the current research is to obtain the temperature distribution in the collector and its thermal optimization with regard to ceramics that have different types. The impact of electrons and power distribution on the inner body of the collector has been done by CST simulation software, and the numerical analysis of heat transfer using ANSYS-CFX software, considering the variable thermal conductivity coefficient with temperature for ceramics. In the simulation, ceramics made of alumina [2], beryllium [3] and aluminum nitride [4] were considered and compared with each other. The optimal temperature distribution has been observed in the case where Berlia ceramic is used as an insulator, and the results have been validated using temperature measurement in practical operation mode. Aviation, meteorology, seafaring, communication satellites, remote sensing satellites, medical diagnosis and industrial devices play a major role [1.] After hitting a material, microwave waves are either reflected, or passed, or absorbed by the material, or a combination of passing and absorption and reflection of waves occurs. If these waves hit the surface of metals, they will be reflected, pass through glass and plastic, and materials that contain water, such as food and the human body, absorb the energy of these waves and convert them into heat, so exposure to direct microwave radiation can cause deep tissue burns [1]. rtl;">1-2- Familiarity with microwave lamps

    Microwave lamp is called a device that is used to amplify, or produce and amplify microwave waves. The first microwave lamp was developed in England in the 1930s, and then it was used in the construction and development of radar systems during World War II. Lamps are necessary and necessary to produce very high powers (10 kW to 10 megawatts) and high frequencies of millimeter waves (100 GHz and above)[1].

    Microwave lamps have different types, including magnetron lamps, klystron lamps, and traveling wave tubes, which are called TWT for short. named Some microwave lamps only perform amplification, such as TWT and klystron, and others, such as magnetron, are responsible for generating and amplifying the signal at the same time [1]. rtl;"> 

    This lamp consists of three main parts; Electron gun, slow wave structure and collector are formed (Figure 1-1). The first part, the electron gun, is responsible for emitting electrons. After the electrons are produced in the gun part, they enter the second part of the system; slow wave structure; which has a helix in the middle.On the other hand, the [2] RF wave is introduced into the helix through the connector (the connector is one of the relatively important parts of the TWT, which is located after the helix and before the collector and has the task of transferring power from the helix to the outside). In the helix, due to the interaction of electrons and the RF wave, the wave is amplified. In this part, the electrons transfer only a part of their energy to the RF wave and enter the third part of the system, i.e. the collector. In this part, the electrons give the rest of their energy to the collector, which increases the temperature of the collector. Due to the complex structure of the collector and the presence of different materials in it and different manufacturing processes, thermal analysis of the collector is of particular importance [2]. TWT lamps work based on the coupling of electron beam with RF field in slow wave structure [3] (SWS). The electric and magnetic fields must be parallel to each other in the space inside the lamp, and as a result, the movement of electrons is linear and along the axis of the helix, for this reason, these types of lamps are also called linear lamps. On the other hand, because the electrons move in the RF slow wave space, these lamps are also called traveling wave lamps (TWT) [2]. Traveling wave tube (TWT) is one of microwave amplifier devices. The five main elements of this vacuum microwave amplifier are electron gun, slow wave structure (SWS), RF input and output connectors, magnet focusing system and the collector. An electron beam emitted from the electron gun, passes through SWS to exchange some of its energy with electromagnetic wave and finally is collected at the end part of the tube known as collector. The electron beam energy is dissipated at the collector as thermal energy. The collector consists of internal body that separates by electric isolator ceramics from outer body. The goal of this research is to obtain temperature contour in collector and thermal optimization in presence of ceramic with various materials. Electron beam power distribution in internal body of collector is simulated by CST software and the thermal analysis of the TWT's collector with ceramics that their heat conduction coefficient are variable with temperature has been carried out using ANSYS-CFX. In these simulations the ceramic materials are AL2O3, BeO and ALN and the results are compared. It has been seen that there is optimized temperature distribution in the presence of BeO ceramic as electric insulator. The results are validated by temperature measuring in experiment.

  • Contents & References of Numerical investigation of three-dimensional heat transfer in traveling wave amplifier collector with input power of 900 and 3000 watts

    List:

    1- Introduction. 2

    1-1-Preface 2

    1-2- Familiarity with microwave lamps. 2

    1-3- TWT lamp. 3

    1-4-Research objectives. 5

    2- An overview of previous research. 9

    2-1-Historical background. 9

    3- Research method. 20

    3-1- Introduction. 20

    3-2- Points of theoretical calculations. 20

    3-3- Inadequacies of theoretical calculations. 22

    3-4-Geometry. 23

    4- Governing equations. 35

    4-1- Introduction. 35

    4-2- Boundary conditions. 36

    4-3-Governing equations. 37

    5- Results. 43

    5-1- Introduction. 43

    5-2-Place of crossing lines. 47

    3-5-Results from electron impact simulation in CST software. 50

    5-4-Results from the simulation of sample number 1 in CFX software. 52

    5-4-1-Ceramic material of aluminum nitride with a base temperature of 40 degrees Celsius (mode 1) 54

    5-4-2-Ceramic material of aluminum nitride with a base temperature of 50 degrees Celsius (mode 2) 57

    5-4-3-Ceramic material of aluminum nitride with a base temperature of 70 degrees Celsius (mode 3) 60

    5-4-4-Aluminum nitride ceramic material with a base temperature of 70 degrees Celsius with averaged input heat (mode 4) 64

    5-4-5-Aluminum nitride ceramic material with a base temperature of 90 degrees Celsius (mode 5) 66

    5-4-6-Alumina ceramic material with an aluminum base surface temperature equal to 40 degrees Celsius (mode 6) 68

    5-4-7-Alumina ceramic material with an aluminum base temperature of 50 degrees Celsius (mode 7) 71

    5-4-8-Alumina ceramic material with a base temperature of 70 degrees Celsius (mode 8) 74

    5-4-9-Alumina ceramic material with an aluminum base temperature of 90 degrees Celsius (mode 9) 76

    5-4-10-Alumina ceramic material with a base temperature of 70 degrees Celsius and average input temperature (mode 10) 79

    5-4-11-Alumina ceramic material with a base temperature of 70 and average input temperature with constant thermal conductivity (mode 11) 81

    5-4-12-Berlia ceramic material with an aluminum base temperature of 40 degrees Celsius (mode 12) 84

    5-4-13-Ceramic material from Berlia with aluminum base temperature of 50 degrees Celsius and using constant thermal conductivity (mode 13). 86

    5-4-14-Ceramic material from Berlia with the temperature of the bottom surface of the base of 50 degrees Celsius and using variable thermal conductivity (mode 14) 89

    5-4-15-Ceramic material from Berlia with the temperature of the bottom surface of the aluminum base equal to 70 degrees Celsius (mode 15) 91

    5-4-16-Ceramic material from Berlia with The temperature of the bottom surface of the base is 70 degrees Celsius with an average input heat (mode 16) 95 5-4-17-Ceramic material from Berlia with the temperature of the bottom surface of the base equal to 90 degrees Celsius (mode 17) 98 5-4-18-Ceramic material of Berlia with the temperature of the bottom surface of the base equal to 50 degrees Celsius and without depress system (mode 18) 100

    5-4-19-Ceramic material from Berlia with the temperature of the lower surface of the base equal to 50 degrees Celsius and without depress system in timed mode (mode 19) 102

    5-4-20-Comparison of temperature distribution in the upper ceramic. 105

    5-5-Validation. 106

    5-6-Results from the simulation of sample number 2 in CFX software. 108

    5-6-1-Alumina ceramic material with a base temperature of 50 degrees Celsius and a constant thermal conductivity coefficient (mode 20) 108

    5-6-2-Alumina ceramic material with a base temperature of 50 degrees Celsius and a variable thermal conductivity coefficient (mode 21) 109

    5-6-3-Alumina ceramic material with a base temperature of 50 degrees Celsius and variable thermal conductivity coefficient with average input power (mode 22) 110

    5-6-4-Alumina ceramic material with a base temperature of 50 degrees Celsius and variable thermal conductivity coefficient with copper cooling base material (mode 23) 112

    5-6-5-Alumina ceramic material and variable thermal conductivity coefficient and three-face contact with the converter (mode 24) 113

    5-6-6-ceramic material from Berlia with a base temperature of 50 degrees Celsius and constant thermal conductivity coefficient (mode 25) 114

    5-6-7-ceramic material from Berlia with a base temperature of 50 degrees Celsius and variable thermal conductivity coefficient (mode 26) 116

    5-6-8-ceramic material from Berlia with a base temperature of 50 degrees Celsius and variable thermal conductivity coefficient with average input power (Mode 27) 118

    5-6-9-Ceramic material from Berlia and variable thermal conductivity coefficient and three-sided base contact with the converter (Mode 28) 119

    5-6-10-Ceramic material from108

    5-6-1-Alumina ceramic material with a base temperature of 50 degrees Celsius and a constant thermal conductivity coefficient (mode 20) 108

    5-6-2-Alumina ceramic material with a base temperature of 50 degrees Celsius and a variable thermal conductivity coefficient (mode 21) 109

    5-6-3-Alumina ceramic material with a base temperature of 50 degrees Celsius and variable thermal conductivity coefficient with average input power (mode 22) 110

    5-6-4-Alumina ceramic material with a base temperature of 50 degrees Celsius and variable thermal conductivity coefficient with copper cooling base material (mode 23) 112

    5-6-5-Alumina ceramic material and variable thermal conductivity coefficient and three-face contact with the converter (mode 24) 113

    5-6-6-ceramic material from Berlia with a base temperature of 50 degrees Celsius and constant thermal conductivity coefficient (mode 25) 114

    5-6-7-ceramic material from Berlia with a base temperature of 50 degrees Celsius and variable thermal conductivity coefficient (mode 26) 116

    5-6-8-ceramic material from Berlia with a base temperature of 50 degrees Celsius and variable thermal conductivity coefficient with average input power (Mode 27) 118

    5-6-9-Ceramic material of Berlia and variable thermal conductivity coefficient and three-sided contact with the converter (mode 28) 119

    5-6-10-Ceramic material of alumina with a base temperature of 50 degrees Celsius and variable thermal conductivity coefficient with small contact resistance (Mode 29) 121

    5-6-11-Ceramic material From alumina with a base temperature of 50 degrees Celsius and a variable thermal conductivity coefficient with high contact resistance (mode 30) 121

    5-6-12-Ceramic material From alumina with a base temperature of 50 degrees Celsius and a variable thermal conductivity coefficient with high contact resistance and considering radiation (mode 31) 123

    5-6-13-Covering (coating) of ceramics with nickel. 125

    5-6-14-alumina ceramic material with a base temperature of 50 degrees Celsius and a variable thermal conductivity coefficient in the optimal state. 126

    5-7-Summary and conclusion. 127

    5-8-Proposals. 129 6- References 130 Source: [1] [Online]. < www.Wikipedia.Com >. [Winter  2011].

     

    [2] Gilmour, A. S. (2011).  Klystrons, Traveling Wave Tubes, Magnetrons, Crossed-Field Amplifiers, And Gyrotrons, Artech House685 Can Ton, Streetnor wood

    [3] Baek, S.W., Lee, J. H., Kim, S. H., Cho, K. H., and Kim, H. S.,

    "Thermal Analysis Of Output Connector For Traveling Wave Tube" Third IEEE International Vacuum Electronics Conference: 230-231, 2002. [4] Waldemar, w. and Wymys?owski, A., "Thermal Analysis Of TWT Delay Line By Combined Theoretical And Numerical Approach" IEEE Telecommunications Research,: 359-362, 2009.

    [5] Sharma, R., Bera, A. and Srivastava, V., "Thermal And Structural Analysis Of Electron Gun Assembly For A C-Band 60W Space TWT" Microwave Tubes Division Central Electronics Engineering Research Institute (CEERI), Vol. 4, No. 5,: 309-314, 2009.

    [6] Fong, H. H. and Hamel, D. J., "Thermal/Structural Analysis Of Traveling Wave Tubes Using Finite Elements" IEEE, International Electron Devices Meeting,: 295-298, 1979.

    [7] D'Agostino, S. and Paoloni C.,"A Finite-Element 3-D Method For The Design Of TWT Collectors" Department Of Electronic Engineering University Of Rome, Vol. 26, No. 2,: 119-122, 2000.

    [8] Behnke, L. K., True, R. B. and Watkins, R. F., "Thermal Mechanical Study Of Mini-TWT Ceramic Jacketed Collectors" IEEE International Vacuum Electronics Conference,: 406-406, 2008.

    [9] Guoqiang, X. and Mingming, Y. "Injecting More Millimeter Wave Traveling Wave Tube Collector Thermal Design" China Academic Journal Electronic Publishing House, Vol. 20, No. 2,: 273-276,  2008.

     

    [10] Lie-Ming, Y., Hai, Y., LI, B. and Tao, H., "Thermal Analysis Of TWT Collector" China Academic Journal Electronic Publishing House, Vol. 18, No. 1,: 97-100, 2006. [11] Thermal Analysis Guide 12, ANSYS Inc. Canonsburg, PA. , 2009.

     

    [12] Damacharla,  M.R., "Thermal And Structural Analyzes Of The Multistage Depressed Collector of A Traveling Wave Tube" Department Of Mechanical Engineering the University Of Utah, 2010.

     

     

    [13] Petillo, J., Epplley, K., Panagos, D., Blanchard, P., Nelson, E., Dionne, N. and Deford J., "The MICHELLE Three-Dimensional Electron Gun And Collector Modeling Tool: Theory And Design," IEEE Transactions on Plasma Science., Vol. 30, No. 3,: 1238 – 1264, 2002

    [14] Kaliski, M. A. R., "Evolution In The Thermal Performance Of Radiation-Cooled Traveling Wave Tubes For Satellite Applications" 4th IEEE International Conference on Vacuum Electronics,: 301-302, 2003.

    [15] Sartre, V. and Lallemand, M., "Enhancement Of Thermal Contact Conductance For Electronic Systems" Applied Thermal Engineering, Vol. 21, No. 2,: 221-235, 2001.

    ]16[ Incropra, Frank P., David P., translated by Rostami, A. (2005). Isfahan Institute of Industrial Jihad Publishing Center

    [17] Crivello, R. and Grow, R. W., "Thermal Analysis of PPM-Focused Rod-

    Supported TWT Helix Structures" IEEE Transactions on Electron Devices. Vol.

Numerical investigation of three-dimensional heat transfer in traveling wave amplifier collector with input power of 900 and 3000 watts
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