多点喷射贫预混喷嘴燃料/空气混合特性研究

Fuel/Air Premixing Characteristics of Lean Premixed Injectors with Multi-Points Injection

关键词:  燃气轮机  低污染燃烧室  多点喷射  贫预混喷嘴  混合特性  预混不均匀度

Key words:  Gas turbine  Low emission combustor  Multi-points injection  Lean premixed injector  Premixing characteristics  Spatial mixing variance

摘要:

基于燃料喷射孔与叶片相耦合的发展趋势，提出了一种新型的带纯收敛出口段的贫预混喷嘴，其燃料喷射孔位于旋流器中空叶片上。验证了采用CO₂代替CH₄研究混合特性的可行性，采用试验和数值计算相结合的方式研究了喷嘴关键结构参数（叶片角度、喷孔孔径和预混段长度）及气动参数（主流空气温度和压力）对喷嘴混合特性的影响。结果表明：旋流器叶片角度增大会增加旋流湍流度进而提高混合均匀度，而喷孔孔径通过控制穿透深度来影响燃料/空气混合特性，加长预混段尽管有利于混合更均匀，但同时会削弱旋流强度而影响燃烧室火焰稳定性。由于燃烧室流动处于“自模化区”，主流空气压力对混合均匀度无显著影响，而温度升高会缩短预混时间使混合均匀度降低。另外不同结构参数的喷嘴在回流区起始点所在截面的SMV（Spatial Mixing Variance）均低于5×10^-4，验证了喷射孔与旋流器叶片相耦合的喷嘴能满足贫预混燃烧室混合均匀度要求。

Abstract:

Based on the development trend of incorporating fuel holes into swirler-vanes， an original lean premixed injector with only-convergent outlet was proposed and its fuel holes were located on the surface of hollow swirler-vanes. Firstly， the feasibility of using CO₂ instead of CH₄ to study premixing characteristics was verified， then the influence of key structural parameters （swirler-vanes angles， fuel hole diameters and premixing section lengths） and aerodynamic parameters （mainstream air pressure and temperature） on premixing characteristics of lean premixed injector was investigated by experimental and numerical methods. The results show that the increase of swirler-vanes angle could improve premixing uniformity by increasing the turbulent intensity， while the fuel hole diameters affected the premixing characteristics by controlling the penetration depth. Although lengthening the premixing section was conducive to more uniform mixing， it also weakened the swirl intensity and affected flame stability of the combustor. Because the swirl flow was in the “self modeling zone”， the mainstream air pressure has no significant effect on the mixing uniformity， while the increase of air temperature could shorten the premixing time and reduce the mixing uniformity. In addition， the Spatial Mixing Variance （SMV） values of the injectors with different structural parameters in the section， where the stagnation point of the main recirculation zone was located， were all lower than 5×10^-4. The lean premixed injector incorporating fuel holes into swirler-vanes can meet the requirement of mixing uniformity for lean premixed combustor.