| Heliostat is a kind of reflector tracking the sun on support of steel structure by regulating its azimuth and elevation in real time. A heliostat group is the major part of solartower power station, also the power station's principal investment part since its construction cost accounts for approximately 50% of the total. Starts from the tower system solar energy power plant establishment, problem of heliostat's wind resistance has been a hard one in design from establishment of tower-typed solar power station. Generally the design of heliostat need to satisfy normal work under strong breeze, and undestroyed under fresh gale. When heliostat works, the sunlight reaching the lens must be guaranteed to always reflect to the target accurately. Since distance between heliostat and target point is comparatively far, a minute deflection on axis of rotation brings huge error, influencing effect of light collecting. Heliostat is also easy to be destroyed subjected to action of strong wind. Such cases are not few in history. And in China heliostat's accidents due to wind destruction happen now and then. Usually solar power system locates at spacious & smooth ground where atmosphere flow affects greatly on the body for its great strength, so it's necessary to study heliostat's surface wind load and its wind effects. In countries whose industry of electricity generation by solar energy is mature, such as the US, Spain, etc., there have been proper wind resistant standard and design methods tuned with the specific climate and landform environment. But in countries that start later on solar energy technology, it's still an urgent problem to assure the reflex attachment's normal work under wind of certain velocity and the equipment's safety. And the present related researches are comparatively few.This dissertation develops fine investigation on heliostat's aspects of surface wind pressure distribution, fluctuating property, statistical property, flow field appearance, wind vibration response, equivalent wind load and so on through technologies of theoretical analysis, wind tunnel test, numerical simulation, etc. Simultaneously, a new versatile interpolation method is proposed. The main research products include:(1) A wind tunnel test on numerous operating conditions got carried on with heliostat group's radiating arrangement and features of different elevation angles & wind directions on various positions accorded. The heliostat's wind pressure distribution under 130 operating conditions in range of 0°~90°elevation angle and 0°~180°wind direction was obtained. The wind pressure distribution's variation rules at different wind directions & elevation angles got summarized. The drag coefficients, the lift coefficients, and the three-dimensional moment coefficients in wind power coordinate under all operating conditions were computed with the least advantageous operating condition got discovered and the local wind pressure's extreme value and position indicated.(2) The CFD model of single heliostat under typical operating situation was founded with technology of numerical simulation used. The corresponding UDF program was framed and used to simulate the wind field entry conditions coincident with the wind tunnel test. The standard k ?εonflow model was selected to compute, and the obtained simulated heliostat's surface wind pressure distribution is consistent with the result of wind tunnel. Moreover, the flow field distribution uneasy to acquire in wind tunnel test was compensated to further explain origin of heliostat's wind pressure distribution, and the influencing factors and the variation rules were discovered. The interference effect of heliostat group's wind field was investigated through numerical simulation. Simulations on different operating situations, different distances and different arrangements were executed to compute correlated interference factors. The flow field distribution was referred to further analyze each factor's influence on heliostat's surface wind pressure.(3) The fluctuating wind pressure's property of heliostat's surface wind pressure was deep researched by contrastive analyzing the measuring points'wind pressure power spectrum. Indexes like skewness, kurtosis and so on were used to appraise wind pressure's statistical property under each operating situation; the normal guarantee rates under different peak value factors were given; the goodness of fit was examined; the wind pressure's Gaussian features were discriminated. For heliostat's non-Gaussian features in local parts, the method of target probability was used to determine its surface wind pressure's calculated peak value factors. The fluctuating wind pressure estimation formula got revised; the mean wind pressure coefficients on mirror surface obtained through CFD simulation, the wind speeds of reference points at mirror surface and the onflow kinetic parameters are used to estimate the fluctuating wind pressure coefficient on mirror surface, which was contrasted with the result obtained in wind tunnel test.(4) A new interpolation method basing on POD technology and referring'grid'thought in geographical statistics was proposed to deal with spatial latent vectors which are'quasistatic'. The Kriging interpolation method was introduces to frame Matlab program interfacing with Surfer software whose powerful space interpolation capacity got played to carries on the spatial interpolation to the structure's surface latent vectors of each phases. This method is strongly universal, could be widely applied in wind tunnel tests & field surveying, and is prospective to be further expanded. (5) The time domain analysis and the frequency domain analysis on heliostat's wind vibration response were made. In order to realize heliostat's parameterized modeling under varied operating situations, the dynamic properties including the heliostat structure frequency, the mode of vibration, the mode's participating coefficient of vibration, mass participating coefficients and so on were used to predict its wind vibration response. The finite element computation model was established to make kinetic time interval analysis, compute dynamic response, and obtain its wind vibration coefficients under different operating situations. In response computation, with the POD method and the CQC method combined, according to the feature that random load's major energy concentrates in several few modalities while only several modalities could represent the real process, combination of the first certain steps of time main coordinates accounting for most energies and the latent vectors were used to replace the original time interval data to enhance calculating efficiency. Study on the result of wind vibration response obtained through methods of time domain and frequency domain discovers that the wind vibration's resonating response weighs much on its modalities of the first several steps, and is good to separate. Thus the method of IWL - LRC's applicability to this kind of structure got proved. The analysis results were based to search more practical design method and formulate heliostat's detailed parameters of wind resistance design. |
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