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CLALIFICATION OF FUNDAMENTAL PHENOMENA ON NON-EMISSION BURNING OF CO_2AND NOx

CO_2和NOx非排放燃烧基本现象的澄清

基本信息

批准号：
10450078
负责人：
NIIOKA Takashi
金额：
$ 5.31万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

To develop a combustion system that is suitable for CO_2 recovery and has less emission of pollutants, a new combustion method using CO_2/O_2as oxidant has been proposed. However, the epically thin and gray-gas radiation model with Planck mean absorption coefficient, which has no reabsorption, has overestimated the emission, especially for "low-speed" flames. The effects of nongray radiation on the propagation and flammability limit of premixed CH_4/O_2/CO_2 flames were numerically analyzed. The results can be summarized as follows :1. The nongray radiation effects described by the statistical narrow-band (SNB) model on the laminarburning velocity and flammability limit become larger as the dilution ratio of CO_2 is increased.2. The gray radiation described by the optically thin model (OTM) loses effectiveness for higher CO_2 dilution ratios and lower equivalence ratios.An experimental and numerical study of diluent (CO_2 or N_2) effects on structure and stability of axisymmetric lifted laminar diffusion CH_4/(Diluent+O_2) flames were also performed over a wide range of the dilution ratio, Z.Results showed that3. As increasing the Z, attached flames are lifted off at the Z_<lim> (0.72 for CO_2, 0.83 for N_2 diluted flame, respectively) and there were steady responses that the flame length. L_f, shortened and the lift off height, H_f, increased as well as the spreading out of the flame base in the radial direction until the Z_b (0.78 for CO_2, 0.86 for N_2 diluted flame, respectively).4. The leading edge structure of the lifted flame has a triple flame, where fuel rich premixed wing is smaller than lean one and the trailing nonpremixed flame inclines immediately to the fuel side from trip point.5. It is also shown that CO_2 effects are stronger than N_2 on the structure and stability due to high heat capacity and low transport rate of Co_2.

为了开发一种适合于CO2回收的低污染物排放的燃烧系统，提出了一种以CO2/O2为氧化剂的燃烧新方法。然而，具有普朗克平均吸收系数的超薄灰色气体辐射模型没有重吸收，高估了排放，特别是对于低速火焰。数值分析了非灰色辐射对CH4/O2/CO2预混火焰传播和燃烧极限的影响。主要研究结果如下：1.统计窄带(SNB)模型所描述的非灰色辐射对层板燃烧速度和燃烧极限的影响随CO_2稀释比的增大而增大。光学稀薄模型(OTM)描述的灰色辐射在较高的CO_2稀释率和较低的当量比下失效。在较宽的稀释率范围内，实验和数值研究了稀释剂(CO_2或N_2)对CH4/(稀释剂+O_2)层流扩散火焰结构和稳定性的影响。随着Z的增大，附着火焰在Z&lt；Lim&gt；(CO_2为0.72，N_2稀释火焰为0.83)处被掀起，并对火焰长度有稳定响应。L_f缩短，升空高度H_f增大，火焰底部沿径向扩散到Z_b(CO_2为0.78，N_2稀释火焰为0.86)。提升火焰的前缘结构为三重火焰，富燃预混翼比贫燃预混翼小，尾随非预混火焰从起止点直接向燃料侧倾斜。CO_2对结构和稳定性的影响比N_2强，这是由于CO_2的高热容和低的输运速率所致。