碟式抛物面太阳能聚能器焦面特性数值仿真

结合太阳能聚能器的光学特性,同时考虑了太阳不平行度、跟踪指向误差、镜面的反射误差以及焦面位置误差等误差因素,采用蒙特卡罗法对碟式抛物面太阳能聚能器的焦面特性进行了数值模拟分析,获得在等口径和等焦距条件下,边缘角对焦平面热流分布的影响,为碟式太阳能聚能器的设计和安装提供参考依据。     

抛物柱面聚光器焦面能流分布特性研究

采用蒙特-卡罗法对抛物柱面聚光器聚焦光斑能流密度进行计算,分析聚光器的表面形状误差、跟踪误差、接收器位置误差、接收器的遮挡、太阳形状、漫反射和聚光器边缘角对焦面能流分布的直接影响,为该面型聚光器的系统设计、安装和能流密度测量提供依据.     

抛物面型聚光器聚焦光斑能流密度分布的计算

采用光线跟踪法对旋转抛物面型聚光器进行光路分析,应用蒙特-卡罗法计算焦平面上的能流密度分布,考虑了聚光器表面形状误差、跟踪误差、接收器位置误差、接收器遮挡作用、太阳形状、漫反射和不同半张角的影响,并通过实例计算证明了该方法的正确性。该方法为系统的优化设计和接收面处能流密度的测量提供理论依据。     

空间太阳能热动力发电系统10kW聚能器焦平面热流分布计算

考虑了表面形状误差、指向误差、不同的半张角、太阳表面亮度不均匀对聚能器焦平面热流分布的影响，该算法是一种较为全面、可靠的计算焦平面热流分布算法。以10kW太阳能动力系统为例，介绍了采取该算法计算的聚能器焦平面的热流分布。     

抛物柱面聚焦器焦平面上辐射通量分布的理论和实验研究

对抛物柱面聚焦器焦平面上的辐射通量分布作了模拟计算和实验研究。计算时采用经某些改进的“半有限积分法”使之更能反映实际运行情况。实验研究采用摄影法，分别以太阳和月亮为光源的折摄焦平面上的像斑。模拟计算与实验结果比较吻合。     

太阳能集能器自动跟踪装置

太阳能集能器自动跟踪装置是由传感器、方位角跟踪机构、高度角跟踪机构和自动控制装置组成。自动跟踪装置驱动太阳能集能器 ,使集能器的主光轴始终与太阳光线相平行。当太阳光线发生倾斜时 ,传感器输出倾斜信号 ,指示执行器动作调整太阳能集能器的角度 ,直到太阳能集能器对准太阳 ,实现自动跟踪太阳的目的。在阴天或太阳光辐照度低于工作照度时自动关机 ,太阳光辐照度达到工作照度时自动开机。该装置适用于聚光式太阳能集能器、太阳能电池等需要跟踪太阳的装置     

DSG太阳能槽式集热器聚光特性模拟

在槽式集热器光学理论的基础上,以DSG太阳能槽式真空集热器为研究对象,建立DSG集热器模型,并运用蒙特卡罗光线追踪法进行辐射计算及分析.通过研究集热器几何聚光比和边界角对集热器吸热管表面圆周方向热流密度分布的影响,获取了集热器的聚光特性.结果表明：计算结果与文献数据吻合良好;随着几何聚光比的增大,吸热管表面圆周方向的热流密度分布趋势不变,数值相应增大;随着集热器边界角的减小,热流密度的最大值增大,热流密度的分布曲线向圆周角-90°方向偏移相应的角度.     

三角元薄膜拼合太阳能聚光器汇聚性能研究

针对一种轻质量的张拉薄膜太阳能汇聚系统,以三角元薄膜拼合反射面为研究对象,同时考虑模型原理误差、太阳光不平行度、接收器遮挡影响,跟踪误差等因素,采用蒙特卡罗法数值对比2种不同三角元拼合膜面在接收面的汇聚辐射能流密度分布情况,分析不同拼合形式、分环数、焦径比、跟踪误差对接收面辐射能流密度分布的影响,为三角元薄膜拼合太阳能...     

塔式太阳能吸热器表面热流密度预测及优化

以塔式太阳能聚光集热系统为研究对象,耦合蒙特卡洛光线追踪法和卷积法,通过综合考虑定日镜阴影和遮挡因子以及反射光束对热流密度的影响,建立一种精度高、计算量小的吸热器表面热流密度分布预测数学模型,获得考虑光线遮挡、余弦损失、溢出损失及大气衰减等因素时单定日镜及全镜场下的光迹追踪路线及热流密度分布规律。并根据镜场光学效率与镜面所处的位置关系提出一种镜场布局优化方式。优化后12:00时镜场的光学效率从43.5%提高到45.6%,日平均光学效率提高约2%,太阳热流密度分布更加均匀。     

Effects of geometrical parameters of a dish concentrator on the optical performance of a cavity receiver in a solar dish‐Stirling system

Dish‐Stirling concentrated solar power (DS‐CSP) system is a complex system for solar energy‐thermal‐electric conversion. The dish concentrator and cavity receiver are optical devices for collecting the solar energy in DS‐CSP system; to determine the geometric parameters of dish concentrator is one of the important steps for design and development of DS‐CSP system, because it directly affects the optical performance of the cavity receiver. In this paper, the effects of the geometric parameters of a dish concentrator including aperture radius, focal length, unfilled radius, and fan‐shaped unfilled angle on optical performance (ie, optical efficiency and flux distribution) of a cavity receiver were studied. Furthermore, the influence of the receiver‐window radius of the cavity receiver and solar direct normal irradiance is also investigated. The cavity receiver is a novel structure that is equipped with a reflecting cone at bottom of the cavity to increases the optical efficiency of the cavity receiver. Moreover, a 2‐dimensional ray‐tracking program is developed to simulate the sunlight transmission path in DS‐CSP system, for helping understanding the effects mechanism of above parameters on optical performance of the cavity receiver. The analysis indicates that the optical efficiency of the cavity receiver with and without the reflecting cone is 89.88% and 85.70%, respectively, and former significantly increased 4.18% for 38 kW XEM‐Dish system. The uniformity factor of the flux distribution on the absorber surface decreases with the decreases of the rim angle of the dish concentrator, but the optical efficiency of the cavity receiver increases with the decreases of the rim angle and the increase amplitude becomes smaller and smaller when the rim angle range from 30° to 75°, So the optical efficiency and uniformity factor are conflicting performance index. Moreover, the unfilled radius has small effect on the optical efficiency, while the fan‐shaped unfilled angle and direct normal irradiance both not affect the optical efficiency. In addition, reducing the receiver‐window radius can improve the optical efficiency, but the effect is limited. This work could provide reference for design and optimization of the dish concentrator and establishing the foundation for further research on optical‐to‐thermal energy conversion.     

Numerical simulation of the heat flux distribution in a solar cavity receiver

In the solar tower power plant, the receiver is one of the main components of efficient concentrating solar collector systems. In the design of the receiver, the heat flux distribution in the cavity should be considered first. In this study, a numerical simulation using the Monte Carlo Method has been conducted on the heat flux distribution in the cavity receiver, which consists of six lateral faces and floor and roof planes, with an aperture of 2.0 m×2.0 m on the front face. The mathematics and physical models of a single solar ray’s launching, reflection, and absorption were proposed. By tracing every solar ray, the distribution of heat flux density in the cavity receiver was obtained. The numerical results show that the solar flux distribution on the absorbing panels is similar to that of CESA-I’s. When the reradiation from walls was considered, the detailed heat flux distributions were issued, in which 49.10% of the total incident energy was absorbed by the central panels, 47.02% by the side panels, and 3.88% was overflowed from the aperture. Regarding the peak heat flux, the value of up to 1196.406 kW/m² was obtained in the center of absorbing panels. These results provide necessary data for the structure design of cavity receiver and the local thermal stress analysis for boiling and superheated panels.     

Mirror rearrangement optimization for uniform flux distribution on the cavity receiver of solar parabolic dish concentrator system

The nonuniform and high‐gradient solar radiation flux on the absorber surface of solar dish concentrator/cavity receiver (SDCR) system will affect its operational reliability and service lifetime. Therefore, homogenization of the flux distribution is critical and important. In this paper, 2 mirror rearrangement strategies and its optimization method by combining a novel ray tracing method and the genetic algorithm are proposed to optimize the parabolic dish concentrator (PDC) so as to realize the uniform flux distribution on the absorber surface inside the cavity receiver of SDCR system. The mirror rearrangement strategy includes a mirror rotation strategy and mirror translation strategy, which rotate and translate (along the focal axis) each mirror unit of the PDC to achieve multipoint aiming, respectively. Firstly, a correlation model between the focus spot radius and mirror rearrangement parameters is derived as constraint model to optimize the PDC. Secondly, a novel method named motion accumulation ray‐tracing method is proposed to reduce the optical simulation time. The optical model by motion accumulation ray‐tracing method and optimization model of SDCR system are established in detailed, and then, an optimization program by combining a ray‐tracing code and genetic algorithm code in C++ is developed and verified. Finally, 3 typical cavity receivers, namely, cylindrical, conical, and spherical, are taken as examples to fully verify the effectiveness of these proposed methods. The results show that the optimized PDC by mirror rearrangement strategies can not only greatly improve the flux uniformity (ie, reduce the nonuniformity factor) and reduce the peak local concentration ratio of the absorber surface but also obtain excellent optical efficiency and direct useful energy ratio. A better optimization results when the PDC is optimized by mirror rotation strategy at aperture radius of 7.0 m, focal length of 6.00 m, and ring number of 6; the nonuniform factor of the cylindrical, conical, and spherical cavity receivers is greatly reduced from 0.63, 0.67, and 0.45 to 0.18, 0.17, and 0.26, respectively; the peak local concentration ratio is reduced from 1140.00, 1399.00, and 633.30 to 709.10, 794.00, and 505.90, respectively; and the optical efficiency of SDCR system is as high as 92.01%, 92.13%, and 92.71%, respectively. These results also show that the dish concentrator with same focal length can match different cavity receivers by mirror rearrangement and it can obtain excellent flux uniformity.     

A novel integrated simulation approach couples MCRT and Gebhart methods to simulate solar radiation transfer in a solar power tower system with a cavity receiver

An integrated simulation approach, which couples Monte Carlo ray tracing (MCRT) and Gebhart methods, is proposed to simulate solar radiation transfer in a solar power tower system with a cavity receiver. The MCRT method is used to simulate the solar radiation transfer process from the heliostat field to interior surfaces of the cavity receiver, and the Gebhart method is used to simulate the multiple reflections process of solar radiation within the cavity. This integrated simulation method not only reveals the cavity effect on receiver performance but also provides real-time simulation results. Based on this method, the reflection loss of the cavity receiver and solar flux distributions are discussed in detail. The results indicate that the cavity effect can significantly reduce the reflection loss and homogenize the concentrated solar energy distributed on interior surfaces to some extent. Moreover, the surface absorptivity has less effect on the reflection loss when cavity effect is considered. The cavity effect on homogenizing solar flux distributions is greater with lower surface absorptivity. In addition, although the concentrated solar energy is distributed on the cavity aperture with similar shapes at different times, the shape of the solar flux distribution on interior surfaces varies greatly with time.     

新型除尘脱硫一体化装置内部流场的数值模拟研究

以一种新型除尘脱硫一体化装置为研究对象,利用通用的流体计算软件Fluent对其三维流场进行模拟。通过分散的颗粒随机轨道模型,利用单元内颗粒法对粉尘颗粒进行追踪,采用带旋流修正的κ—ε方程模型模拟气相流场。分析了中心筒孔径大小及长度对流场均匀性的影响,并使用提出的截面速度不均匀性系数进行了定量分析,从工程实际出发,确定孔径Ф为1200mm、中心筒长度为400mm时为最优;模拟计算值可作为新型除尘脱硫一体化装置运行优化的依据。