Research On Non-uniform Temperature Field And Its Effct Of Shanghai65m Radio Telescope

Shanghai65m radio telescope is Asia’s largest full-range rotatable radiotelescope by now. Its reflector surface area is equivalent to the size of the eightstandard basketball courts. High precision is required for its large span reflectorto meet the objectives of VLBI positioning scientific objectives.Gravity, windand temperature fields are threee main factors affecting the precision of radiotelescope. Non-uniform temperature field and its effect on main reflector’ssurface precision were simulated, which can provide effective reference forthermal monitoring and thermal control of similar radio telescopes. Thefollowing work is carried out in this paper:1. Basic principles of radio telescope’s thermal analysisBasic ways of heat exchange are introduced. Modes of heat transfer thatradio telescope interacts with the surrounding environment in outdoorenvironment are analysed. The methods of computing air, sky and groundtemperature according to the requirements of calculation of temperature field arestudied. Method for calculatation of solar radiation is investigated. Finite elementmethod of computing radio telescope’s temeprature field is studied.2. Analysis on non-uniform temperature field of main reflector ofShanghai65m radio telescopeThe thermal finite element models (FEMs) of main reflector of Shanghai65m radio telescope at four kinds of elevation angle status are established inactural summer environment. The methods for calculation of shadowing,convection heat transfer, sky and ground radiation are investigated. Temperaturefield transient analysis is done under3kinds of typical wind speeds with thestructure in different elevation angle status. Laws of distribution of shadowingand non-uniform tempearture field under each evelation angle status arepresented. Differences of temperature field under different wind speeds arecompared as well as summarizing the law of effect that wind speed have on mianreflector’s non-uniform temperature field.3. Analysis on non-uniform temperature field of supporting structure of Shanghai65m radio telescopeThe thermal FEM of supporting structure of Shanghai65m radio telescope isestablished under actural summer environment. Method is discussed forcalculation of structure’s temperature field which takes solar radiation, airconvection, sky radiation and ground radiation into account. Temperature filedtransient analysis is conducted under the conditions of3kinds of typical windspeeds. Characteristics of distribution of temperature field are summarized inaccordance with time and spatial form of the structure. Differences oftempearture field under conditions of different wind speeds are compared toanalyze the effect that wind speed have on supporting structure’s temperaturefield.4. Analysis on non-uniform temperature field and its effect of the wholestructure of Shanghai65m radio telescopeThe thermal FEM of the whole structure considering both main reflector andsupporting structure is established. The method for calculation of temperaturefield of the whole structure is considered. Analysis is carried out on non-uniformtemperature field and its effect on main reflector’s surface precison on twospecific days with different wind speeds in summer and winter, respectively.Laws of wind speed’s influnce on temperature field and its effect in differentseasons are analysed. Differences of temperature field and its effect between theresults of reflector or supporting structure considering only models and thereflector and supporting structure combined model are compared in summer.