Developments of High-Efficiency and Low-Emission Gas Turbine Combustors by Diode-laser Absorption Measurements

本研究旨在利用半导体激光吸收测量技术，研究燃烧噪声、燃烧振荡以及CO_2和NO_x排放的有效控制因素，以开发高效低排放的燃气涡轮机燃烧室。考虑到详细的动力学机制和传输和热特性的温度依赖性，直接数值模拟氢/空气和碳氢化合物/空气湍流预混火焰进行。利用直接数值模拟的结果，对半导体激光吸收测量进行了模拟，并阐明了模拟的准确性。结果表明，半导体激光吸收光谱法用于燃烧气体的测量，其测量精度是足够的。在数值模拟的基础上，研制了基于半导体激光吸收的H_2O和CO_2吸收测量系统。测量在基本的实验室燃料箱中进行，以验证准确性，如物质浓度，温度和时间分辨率。从这项研究中，二极管激光吸收测量的优点和局限性。通过直接数值模拟的结果，研究了局部热释放率、火焰前缘曲率和应变率等局部火焰结构与NO_x生成速率的关系，为制定有效的排放控制方案提供了依据。结果表明，由于局部NOx生成速率与局部放热和CH浓度有很好的相关性，CH浓度是NOx生成的一个很好的控制因子。为了确定燃烧噪声和燃烧振荡的有效控制因素，还对化学反应湍流中的声进行了直接数值模拟。从DNS的结果出发，探讨了湍流燃烧的声产生机理，并提出了远场声的预测方法。

In this study, diode laser absorption measurements and effective control factors of combustion noise, combustion oscillations and emissions of CO_2 and NO_x are investigated to develop high-efficiency and low emission gas turbine combustors. Direct numerical simulations of hydrogen/air and hydro-carbon/air turbulent premixed flames are conducted by taking into account detailed kinetic mechanisms and temperature dependence of transport and thermal properties. By using the results of direct numerical simulation, simulations of diode laser absorption measurements are conducted and the accuracy of those is clarified. It is shown that accuracy of diode laser absorption measurements is enough if it was applied in the burnt gas. Based on the numerical simulations, measurement systems based on the diode laser absorption are developed for H_2O and CO_2 absorption. Measurements are conducted in fundamental laboratory buners to verify accuracy such as species concentration, temperature and time resolutions. From this study, advantages and limitations of the diode laser absorption measurement are shown. From the results of direct numerical simulations, relations between NO_x production rate and local flame structure such as local heat release rate, curvature of the flame front and strain rate are also investigated to develop the effective control scheme of emission. It is shown that CH concentration will be a good control factor of NO_x because the local NO_x production rate is well correlated with the local heat release and CH concentration. To identify the effective control factors of combustion noise and combustion oscillations, direct numerical simulations of sound in chemically reacting turbulence are also conducted. From the results of DNS, sound generation mechanism form turbulent combustion is investigated and prediction method of far field sound is developed.