Research On Non-uniform Temperature Field Of Giant Radio Telescopes

Radio telescope, also called radio antenna, is an important tool for collectingand catching the electromagnetic radiation information from celestial objects,and it is making giant contribution to the progress of radio astronomy. Allmovable radio telescopes mainly consists main reflector, sub-reflector, backupstructure, azimuth bearings, elevation bearings, pedestal and etc. High precisionand resolution are two important targets in the evaluation of radio telescope’sperformance, it is effective to improve the telescope’s performance byconstructing the telescope in larger dimensions. However, for the large-span andhigh-accuracy required telescope, the non-uniform solar temperature load mayreduce its shape accuracy as the its self-weight or the wind load, which is causedby extraordinary complicated factors such as periodic atmosphere temperature,solar radiation, shading by the structure itself or by the nearby surroundings.Hence, the research is of great engineering application value as well astheoretical significance to analyze thermal behavior of the radio telescope underactual environment by simulation. The main contents of this paper are shown asfollowing.1. Analysis of sun shadow of radio telescopeBased on the software ANSYS, Calculation Program of Shadow (CPOS)module was proposed for the analysis of radio telescope’s shadow under sunshinewith FORTRAN language. Moving onward, the corresponding analysis ofShanghai65-m radio telescope is carried out on the day of summer solstice, theresults introduce the members’ sunshine coefficients.2. Definitions of thermal environment for the simulation of the radiotelescopeAnalyze the complicate thermal environment thoroughly, and settle themethods in which the radio telescope exchanges heat with the surroundingenvironment. Propose simplified ways for the simulation considering the solarradiation and long-wave radiation between structures and surroundingenvironments. The computation method taken the time boundary conditions into consideration was programmed, which bases foundation for the finite elementanalysis.3. Simulation and effect analysis of non-uniform temperature field ofShanghai65-m radio telescopeThe finite element model for thermal calculation of Shanghai65-m radiotelescope in the actual environment is established. Meanwhile, the factors likesolar radiation, shadows caused by the surrounding environment, periodic airtemperature and etc are taken into consideration. The non-uniform solartemperature field is computed using the transient analysis method, thedistribution of temperature field is computed under different working azimuthangles in different periods of the day. Summrise temporal and spatialcharacteristics of the distribution of the temperature field, emphasizing on theRMS temperature error analysis under a variety of azimuth angles based on twooccasions, one is under the condition that taking the rod block into consideration,the other one is to take the block out of mind.4. Research on solar cook effect of Shanghai65-m radio telescopeAnalyse the causes that form the solar cook effect of radio telescopes, makedetailed instructions to compute the solar cook effect by making use of themethod of light projection algorithm. Furthermore, establish finite element modelof Shanghai65-m radio telescope, make parameterized analysis on the solar cookeffect under different working azimuth angles. Compile statistics on thephenomenon’s generation time, lasting time and the highest temperature thatsub-reflector can reach under the conditions mentioned above.