The Research Of Ground Based Solar Telescope Dome Performance And Mechanical Structure Thermal Control Technology

In order to study the solar flares, coronal mass ejections and proton event, which are the dynamic origin of solar activity, and verify the existing physical model for prediction of solar activity, requires the ground-based solar telescope has excellent optical and mechanical performance. Ground-based solar telescope, however, as a complex measurement system, any fluctuations of each link can cause measurement errors, affecting its performance. Therefore, in addition to specify a complete scheme for the design, manufacture, and installation of the telescope, also must have a good performance of the dome to provide a stable environment for observation, so it is of great significance to design and analyse dome for improving the environmental adaptability and guaranteeing the observations performance of ground-based solar telescope The previous research methods of dome performance were simply by comparing the internal air pressure drop, up-left effects and fluid dynamics parameters to select and design dome, although a lot of valuable conclusions had obtained, since high spatial resolution, high temporal resolution and high spectral resolution of "three highs" observation had been put forward, there would be more strict with the dome, only through analysis of the single fluid dynamics parameters, the conclusion was hard to avoid having a lot of one-sided. Aiming at the shortcomings of the these analysis, this paper proposed a optical performance evaluation method, through calculating the ambient air refractive index of dome, and the change of light intensity and phase of target after light through the dome environment air to get the influence of dome on the quality of imaging.First, thermal network model was set up to calculate the indoor air temperature, since the open dome could guarantee consistent inside and outside air temperature, the preliminary scheme of dome structure had been decided. And the numerical solution of air refractive index were attained through CFX software, which was based on the finite volume method, under different boundaries Secondly, the transmission rule of light waves in the turbulent atmosphere, and the multi-level phase screen algorithm to calculate light intensity and phase of target waves on the observation screen were discussed in detail.Then, through 3:200 scaled dome model wind tunnel tests, at the same condition, the deviation of air speed was less than 20% between the results of numerical simulation and wind tunnel test, and the deviation of wind pressure of the primary mirror between the results of numerical simulation and wind tunnel test was less than 5%, the accuracy of the numerical simulation result had been verified, which provided a important basis for using CFX results to calculate the change of light intensity and phase of the target light after through dome ambient air.Then, the distribution of light intensity and phase on the screen, under different speed and angles of flow were obtained based on the finite volume method and multi-level phase screen algorithm, after target waves through the open dome ambient air. And the characteristics of the imaging were lee observation under the same flow speed, the quality of imaging were bad, and the greater the flow speed was, the quality of imaging was more poor.In order to solve this problem a semitransparent circular wind windshields, which the interval of wind windshields was 1/45 of the distance to the telescope, was designed. Through wind tunnel tests and comparing the quality of imaging with and without the wind windshields, confirmed the windshield had the ability of reducing wind speed and played an important role in improving the optical performance of open dome.On this basis, in order to further improve the ground-based solar telescope’s environmental adaptability, this paper also researched the influence of the temperature non-uniformity on the pointing accuracy of telescope. After the contrast test of different thermal control method, the hybrid thermal control scheme, which contained insulating coating, sun-shields and forced air cooling for solar telescope mechanical structure was identified.When environmental wind speed was low, insulating coating adopted nanometer titanium dioxide, the inlet velocity of forced air cooling was 8m/s, aluminum sun-shields, the distance between the mechanical structure and sun-shields was 40 mm, and the flux of solar radiation was 845.17W/m2.Through the conjugate heat transfer numerical simulation, the maximum temperature difference for the mechanical structure was 2.4℃, which met temperature nonuniformity of the mechanical structure less than 3℃.