Co-simulation Study On Thermal,Stress And Electric Characteristics Of Helix Traveling Wave Tube

Traveling wave tube is a kind of very important microwave vacuum electronic devices.For its high power,high gain,high efficiency,broad band and other advantages,it is widely used in modern radar,electronic countermeasures,communication and military equipment and so on.With the continuous development of advanced radar and microwave navigation communication system,the performance of the traveling wave tube is higher and higher.In addition to the electrical performance,the heat dissipation and thermal stress of these high-performance travelling-wave tubes are also required to be analyzed to ensure the stability and reliability.Due to the constraint between the external structure and internal parts of TWT,temperature changes in any part of TWT will produce thermal stress between parts of the traveling wave tube.When the thermal stress exceeds the material's endurance limit,the parts will break.The performance of the wave tube is very size-sensitive,and the thermal stress deformation will affect the electrical performance.Temperature,stress and electrical parameters restrict each other,and it is of great significance to ensure the stable and reliable operation of the travelling wave tube.This thesis combines the thermodynamics theory with the simulation calculation,and studies the three components(electron gun,slow wave structure and collecting pole)of a certain type of helix TWT.The thermal distribution was obtained by ANSYS and then the thermal distribution was used as the initial condition of static analysis of thermal stress.According to the temperature distribution and stress,the reliability of each component can be analyzed,and the effect of the deformation on the electrical performance was calculated by remodeling the deformed structure and comparing the change of the electric properties before and after the deformation.The main work and innovation of this thesis include:1.The environmental adaptability of electronic gun was studied.Chang the environment temperature from-20? to 80?,make the steady state thermal analysis of the electric gun and get the cathode temperature.It is found that the cathode temperature is always around the working temperature of 1050? with a deviation less than 0.67%.This implies that the electric gun can work stable in a varying environment temperature.2.Radar and military equipment requires fast response capability(less than 3 minutes),while the start-up time of electric gun determines the response speed of TWT.The startup time of electric gun is calculated by the transient thermal analysis module of ANSYS.The start-up time is about 2 minutes 55 seconds,satisfying the requirement of fast launch in 3 minutes.3.Co-simulation of electric gun is studied.The relationship between electron gun thermal analysis and grid,material,thermal contact resistance and environment temperature is analyzed and the co-simulation of the electron gun is performed to obtain the temperature distribution and thermal stress deformation,and then the deformation model was imported into MTSS to recalculate the electrical performance.Comparing the electric performance before and after deformation,the waist position of the electron gun was increased by 0.05%,and the cathode emission current decreased by 8.4%.4.The co-simulation of helix slow-wave structure is performed and the thermal,thermal stress and deformation is obtained by ANSYS.In this simulation,a more precise power loss distribution is loaded and it is found that nearest to the output window,the highest temperature of helix TWT is 249.13?.Remodeling of thermal stress deformation and calculating the high frequency characteristics,the coupling impedance and dispersion characteristics was found to be 2.1% and 5.4‰ changed respectively.5.The co-simulation of multi-stage depressed collector is performed.Using MTSS to calculate the power loss of each plate as a heat source,the temperature and stress distribution were obtained by ANSYS.When ignoring secondary electron,the highest temperature and the maximum stress of the collector were 189.7?,67.471 Mpa respectively.With secondary electron considered,the highest temperature and the maximum stress were 275.55?,112.35 Mpa,which increased by 45.2%,66.5% comparing with those ignoring secondary electron.