A Study of Turbulent Combustion Mechanism in a High Temperature, High-Pressure, and Low-Oxygen Environment

本项目旨在将高压高温湍流燃烧的研究扩展到低氧浓度燃烧，用于废气再循环的新型预混式燃气轮机燃烧室。用N_2和CO_2稀释的氧化剂对湍流预混火焰和湍流非预混火焰进行了研究。利用OH-PLIF和CH-PLIF对火焰的瞬时结构进行了观察和分析。湍流特性、NOx排放和湍流燃烧速度的测量也进行了。对于湍流非预混火焰，用CH-PLIF对氧化剂预热至1300 K，氧浓度最小为4 vol %的CO_2和N_2稀释火焰进行了可视化。已经证明，气泡状火焰结构在火焰升腾时形成。低氮氧化物排放也已证实，即使使用氮氧化物分析仪非提升火焰。对于紊流预混火焰，在1.0 MPa压力下，用CO_2稀释的空气混合物预热至573 K，取得了稳定火焰的成功。模拟带有废气再循环的预混式燃气轮机燃烧室，混合气的氧浓度可降低10 vol %。获得瞬时OH-PLIF图像，并进行分形分析，探讨内在火焰不稳定性对CO_2稀释预混火焰的影响。测定了湍流燃烧速度和产物种类的时间平均产率。结果表明，由于高压高温下CO_2的稀释作用，低氧浓度湍流预混火焰的放热面积增大，燃烧产物的时间平均生成率降低，放热程度较轻。这些特性是降低预混式燃气轮机燃烧室燃烧不稳定性的重要因素，也是本课题提出的实现新型废气再循环预混式燃气轮机燃烧室的有利特点。少

This project aims to extend the research of high-pressure and high-temperature turbulent combustion to the low oxygen concentration combustion in terms of utilizing for new premix-type gas turbine combustors with an exhaust gas recirculation. Turbulent premixed flames and turbulent non-premixed flames using oxidizer diluted with N_2 and CO_2 were investigated. Observation and analysis of instantaneous flame structure using OH-PLIF and CH-PLIF were conducted. Measurements of turbulence characteristics, NOx emission, and turbulent burning velocity were also performed.For turbulent non-premixed flames, oxidizer preheated up to 1300 K, whose oxygen concentration was 4 vol % minimum diluted with CO_2 and N_2 were visualized using CH-PLIF. It has been proved that bubble-like flame structures are formed especially in the case of lifted flames. Low NOx emission has been also confirmed even for non-lifted flame using a NOx analyzer.For turbulent premixed flames, flame stabilization for the meth … More ane-air mixture preheated up to 573 K diluted with CO_2 at pressure up to 1.0 MPa has been succeeded. The oxygen concentration of the mixture could be reduced up to 10 vol % simulating the condition of premix-type gas turbine combustors with exhaust gas recirculation. Instantaneous OH-PLIF images were obtained and fractal analysis was performed to explore the effects of intrinsic flame instability on CO_2 diluted premixed flames. Moreover, Turbulent burning velocity and time-averaged production rate of product species were determined. As a result, turbulent premixed flames for low oxygen concentration due to CO_2 dilution at high pressure and high temperature increases the volume of heat release region and reduces the time averaged production rate of combustion products, leading to mild heat releasing. These characteristics are an important factor for reducing combustion instability of premix-type gas turbine combustors and profitable features in terms of realizing new premix-type gas turbine combustors with exhaust gas recirculation proposed in this research project. Less