太阳能碟式二次反射系统的光路分析与比较

Optical analysis and comparison of two-stage solar dish system

比较直径为1 000mm、不同边缘角的碟式一次镜结合旋转椭圆面型、旋转双曲面型、平面型及旋转抛物面型二次镜的聚光效果.除旋转抛物面型二次反射系统,其他系统的焦点位于一次镜顶点,二次镜数值孔径为0.2.随着边缘角的增加,旋转椭圆面型二次反射系统接收板中心的能流密度先增大后减小,二次镜的相对位置降低,遮光率减小;旋转双曲面型二次反射系统的能流密度变化不大,二次镜的相对位置升高,遮光率减小;两者均适用于二次反射低焦系统.随着边缘角的增大,平面型二次反射系统的能流密度先增大后减小;二次镜的相对位置不变,遮光率增大,适用于二次反射高焦系统.旋转抛物面型二次反射系统的能流密度随着边缘角的增大而增大,二次镜的相对位置和遮光率不变,适用于低倍聚光系统.对于误差的容忍性,平面型二次反射系统最优;旋转双曲面型优于旋转椭圆面型二次反射系统.

Four types of secondary mirrors（SM）were compared,including an ellipsoidal,a hyperboloidal,aplanar and a paraboloidal type.A primary dish with a diameter of 1 000mm and a varying rim angle was employed in each system.The concentrated spots were on the vertexes of the dishes and the numerical aperture of the SM was 0.2except for the paraboloidal system.As to the ellipsoidal system,flux density on the receiver increases when rim angle90°and then decreases.The relative location and shading percentage of the SM decreases.As to the hyperboloidal system,when rim angle increases,flux density varies little.The relative location of the SM increases and shading percentage decreases.Both the ellipsoidal and hyperboloidal systems are suitable to cases which need low concentrated spots.As to the planar system,flux density increases when rim angle〈45°and then decreases.The relative location of the SM is invariable and shading percentage increases.A planar SM is suitable to a system which needs a high concentrated spot.As to the paraboloidal system,when rim angle increases,the flux density increases while the relative location and shading percentage of the SM are invariable.A paraboloidal SM is suitable for low concentration ratio system.The hyperboloidal system has better tolerance to errors than the ellipsoidal system while the tolerance of the planner system is the best.