燃气轮机旋流通道小孔射流问题的大涡模拟

Large eddy simulation of small hole jet flow inside swirl channel of gas turbine

针对PRECCINSTA燃气轮机旋流通道中的小孔燃料射流问题,采用大涡模拟方法对冷态的甲烷和空气混合现象进行了研究,采用流场计算程序LESOCC2C对PRECCINSTA旋转混合室进行LES计算,共计算了4个算例:全局当量比为0.70,0.83和网格总数为120万、180万的组合.结果表明:甲烷由小孔射入主流空气后,由于混合时间短,混合气在进入燃烧室时,存在很大的当量比波动,导致强烈的部分预混燃烧现象;全局当量比为0.83时,其当量比波动范围接近[0.59,1.15];全局当量比为0.70时,其波动范围为[0.40,1.00],超出部分反应机理的适用范围,对PRECCINSTA燃烧室中火焰开展大涡模拟计算时,必须采用合适的部分预混燃烧模型和化学反应机理.

To solve the problem of smallhole fuel jet flow in PRECCINSTA gas turbine, the large eddy simulation （LES） method was used to simulate the mixing process of methane and air in cold isothermal state by the flow field calculation program of LESOCC2C. Four simulations were performed with global equivalent ratio of 0.70,0.83 and with grid combination of 1.2 million or 1.8 million cells, respectively. The results show that because of the short mixing time, there is large equivalent ratio fluctuation when the mixture enters combustion chamber, resulting in strong partially premixed combustion phenomenon in combustion chamber. For the global equivalent ratio of 0.83, the calculated equivalent ratio fluctuation range is close to [0.59, 1.15]. For the global equivalent ratio of 0.70, the equivalent ratio fluctuation range is [0.40, 1.00], which is beyond the applicable range of partial reaction mechanism. Therefore, suitable combustion model and simplified reaction mechanism are required to conduct the LES of PRECCINSTA combustion problems with small hole fuel jet flow phenomenon.