基于钝体扰流的氢气微混扩散燃烧组织研究

Investigation on hydrogen micromix diffusive combustion organization based on bluff body disturbance

氢气是实现航空发动机零碳排放最具有应用潜力的燃料之一,本文提出一种蜂巢钝体微混扩散燃烧结构,内置微型钝体扰流主流空气,以增强与氢气掺混。采用k-ω剪切应力输运(SST)湍流模型和火焰面生成流行方法(FGM)中的扩散火焰方法,数值仿真模拟了基准方案在无氢气喷注、冷态、热态工况下的流动燃烧特性,详细分析了微混单元气动热力过程。建立了基于响应面预测和遗传算法的蜂巢微混单元优化设计流程,以钝体角度和钝体出口高度为约束条件,NOx排放最低为优化目标,获得了NOx排放的影响规律和最优方案。研究结果表明:钝体三维尾迹涡耦合氢气射流涡可显著增强主流扰动和掺混,氢气射流涡受工况和结构参数影响较大,钝体出口高度是影响NOx生成的敏感性参数,在2030 kPa和818 K的进气条件下,最优方案在15%含氧量条件下NOx的体积浓度低于5×10^(-6)。

Hydrogen is one of the fuels with the most potential to achieve zero carbon emission of aero-engines.In this paper,a micromix diffusive combustion structure based on the honeycomb bluff body is proposed.The micro bluff body is built in the honeycomb to disturb the mainstream air and enhance its mixing with hydrogen.The flow and combustion characteristics of the standard scheme without hydrogen injection,the cold field,and the hot field are simulated using the k-ωShear Stress Transfer(SST)turbulence model and the diffusion flame method in Flamelet Generated Manifold(FGM).The aerothermal process of the micromixing unit is analyzed.The optimal design process of the honeycomb bluff body element is established based on Genetic aggregation approximate model.The design variables are angle and height of the bluff body whereas the minimum NOx emission is the optimization objective.The influences of the parameters on NOx emission and the optimal scheme are obtained.Results show that reverse rotating vortex pairs and three-dimensional jet vortices are formed in the cross section when hydrogen is injected into the highspeed mainstream air,the turbulent disturbance and hydrogen and air mixing are significantly enhanced,the hydrogen jet vortex is considerably affected by the working conditions and structure parameters,and the height of the bluff body is the sensitive parameter affecting the formation of NOx.Under the intake condition of 2030 k Pa and 818 K,the NOx emission of the optimal case is lower than 5×10^(-6)under the 15%O_(2)content condition.