| Tower solar power plant is a new-style generating equipment, by transforming sunlight into thermal energy power generation system and generating electricity finally, in which heliostat is a major component to be taken into consideration sunlight to the heat absorbing tower. In actual engineering, due to changes in the sun’s azimuth angle, the angle of reflected light is likewise equally changed. In order to secure the sunlight reflection is helpful, the spatial position of the mirror plate to be adapted at times. In addition, the heliostats required to normally operation under certain wind conditions, and thus the heliostats are highly susceptible to the wind.To meet the demand for power generation, solar power station to be collected in a large area of sunlight, and therefore, the heliostat field is often composed of a large number of heliostats. For the interference in the vicinity of the heliostats, the wind pressure disturbed will change, so wind interference study for a group of heliostats yet more in-depth attention involved.The surface wind field characteristics, heliostat surface wind load distribution and the interference effect is basis of heliostat wind resistance studies. Unfortunately, in these areas in China is basically in a blank state, this is bound to affect the development of the solar-thermal industry in China.In the face of these problems, the field test, wind tunnel experiments and theoretical analysis method were combining applied in this article, for solar tower heliostat group of wind loads was investigated in-depth and systematic. The main results are as follows:(1) To explore the wind characteristics near ground, a testing device was erected near the heliostat group. By the field measurements, longer time wind datum were acquired, and further analysis was carried out to obtain the parameters of wind characteristics. The results demonstrate the wind profile is a discrepancy with the value of various codes. The measured turbulence intensity is close to the foreign standard but higher than the value recommended by the Chinese code. The turbulence integral scale is different from some codes’ recommended values. The decay coefficient of coherence function is altered with the distance, and an obvious contrast between the results of measurements and the recommendation value by Davenport was pointed out.(2) Select a typical heliostat, a variety measurement taps was laid at mirror panel section and the pillar portion respectly, using hammer excitation at a fixed measuring point, in turn pick-up at the other measuring taps, and based on a least squares fit, the dynamic properties of a variety of elevation was gutted. Using ANSYS software, the type heliostat numerical modal analysis was conducted, through the field modal testing, get the type of elevation heliostat under a variety of dynamic parameters. The numerical results of modal analysis and field measurement results were compared and verifying the numerical simulation results is reasonable.(3) By the site test, wind pressure distribution results of single heliostat under multiple working conditions were obtained. The results show that the average wind pressure coefficients at the front facade taps tends to be larger, and contraries at rear position taps’. due to the presence of the braces, the pressure distribution at the back of taps is more complex, The fluctuating wind pressure coefficient at the leading edge of the taps was larger, the trailing edge’s was smaller. For non-Gaussian wind pressure processes, probability distribution was better by using the three-parameter gamma distribution when its absolute value of skewness great than 0.3. Based on the field test results of the single heliostat’s wind pressure, laid the foundation for the subsequent verification of reliable wind tunnel experiments, and also fill the research blank of heliostat tower solar thermal power plant pressure distributions site measured.(4) A rigid scale heliostat with 128 taps was manufactured, and the pressure measurements were made in a kind of turbulent boundary layer, which simulated the natural winds in accordance with results of the site measurement. Comparison was carried out by selected consequences of field measurement and wind tunnel testing.the comparison results showed that the average wind pressure coefficient comparison results are in good agreement, and affected by changes in wind direction, there are some differences in comparing the results fluctuating wind pressure coefficients, but both of the same trend, the wind tunnel experiments’ measured results of the measuring point probability density function, pressure power spectral density function and coherence function agree well with the results of full measurement. The reliability of the results of wind tunnel tests was confirmed. That verifies the reliability of the wind tunnel test results and also provides support for the follow-up study of heliostats.(5) Synchronous multi-channel pressure and high-frequency dynamic balance winds tunnel experiment were adopted to obtain the pressure and load distribution rule of heliostat. A comparison with similar structure’s research results was conducted firstly. The results showed that it is important to accurately obtain the actual wind field characteristic parameters. Built on wind tunnel test results, the values of shape coefficient, local pressure shape coefficient, gustiness factor and additional design parameters were recommended.(6) At different pitches, a variety of layout conditions, based on the synchronization manometry heliostat rigid model and the high-frequency dynamic balance wind tunnel experiments, obtained this type of situation by force heliostats. Based on the analysis results are given based on the type of heliostat shape coefficient, gust factor, the wind loads and other parameters of the interference factor values recommended various arrangements.The research methods and results of this paper provide reference for a similar heliostat design and research. |
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