Research Of Determining Typical Elements' Luminance At Tunnel Portals By Radiation-Illuminance Conversion Method

This is the sub-topics of National Natural Science Foundation of China "Research on road tunnel lighting design with the perceived contrast method"(project approval No: 51278507) to further improve the most important benchmarks of the tunnel lighting standards- typical elements' luminance at tunnel portals, to provide a more scientific basis for the development of tunnel lighting design standards and the practice of tunnel lighting design.Scenery elements' luminance at tunnel portals is the most important parameter of tunnel lighting design. Reasonable choice of the elements' luminance values at tunnel portals is necessary to ensure the safety of traffic in the tunnel but also to ensure that the tunnel lighting is economic. Based on the perceived contrast method, this thesis investigated with emphasis the scenery elements' luminance at tunnel portals under the concept of equivalent veiling luminance Lseq. CIE88: 2004 proposed “to use the highest luminances likely to occur during at least 75 daytime hours per year as reference” to calculate Lseq reference value, which is actually the concept of a cumulative frequency. Although CIE 88: 2004 and China's specifications for design of highway tunnel lighting are given scene luminance reference values for different orientations, but in fact, different locations, different climatic conditions of light and so on, will cause the surface luminance values outside the cave vary widely, and we are currently lack of large-scale and long-term observed data accumulation of elements' luminance at tunnel portals. Therefore, the reference luminance of elements at tunnel portals that the specification recommends are short of measured basis and theoretical basis.In order to solve this problem, This article according to the actual needs of tunnel lighting, and based on the measured data of radiation, illumination of a year in Chongqing, firstly used vertical illuminance to reflect the typical elements' luminance, analyzed its various factors, took the vertical conversion luminous efficacy as the key parameters of radiation- illuminance conversion method, and then developed the mathematical models of vertical conversion luminous efficacy and clearness index as well as solar altitude in four directions,which is the radiation- illuminance conversion model. After compared with the measured data of another year in Chongqing and experimental verification by myself, it proved that the models have relatively high precision. On this basis, with the use of solar radiation data and weather conditions observation of weather station in nearly two years, combined with the concept of cumulative frequency, the reference vertical illuminance can be obtained. Considered the tunnel scene surface as diffuse surface, I made experimental tests to obtain the reflection coefficient of vertical scene outside the cave. By the reference vertical illuminance and reflectance coefficient, the reference values of(vertical) scene luminance at tunnel portals can be finalized. Chapter 4.4 will be the results of examples of this study applied in the calculation of equivalent veiling luminance of multiple tunnels in Chongqing, combined with other scene luminance and parameters from the existing achievements. At this point, it is accessible to obtain a relatively quickly and accurately method to determine typical elements' reference luminance at tunnel portals, by radiation- illuminance conversion model, which is adapted to the Chongqing area.