燃气轮机排气管道非均匀进口喷雾冷却数值研究

Numerical Study on Non-uniform Inlet Spray Cooling of Gas Turbine Exhaust Pipe

为研究燃气轮机排气管道非均匀进口条件下喷雾冷却过程中管道内部流场、喷雾雾滴汽化运动轨迹和冷却效果,基于Realizable k-ε模型结合壁面函数和DPM模型进行喷雾冷却数值研究,探究在非均匀进口条件下喷雾喷头位置分布、不同喷雾雾滴直径和喷雾流量对管壁和出口降温效果的影响。排气管道为直径1.524 m的圆柱体,前直段长5 m,后直段长8 m,转弯半径2.8 m。喷雾喷射的锥角为45°、速度为30 m/s、温度为328.15 K。研究表明:在非均匀进口条件下,非均匀分布且集中于高温区域的喷头喷雾降温效果最佳,管壁温降为111.08 K,出口温降为97.14 K,而喷头排数对其降温效果影响较小;喷雾冷却前、后的管道出口平面速度分布标准差分别为12.77和11.14 m/s,喷雾可改善后直段流场均匀性;非均匀进口条件对直径小于25μm的雾滴影响大,雾滴汽化速度快,无法与壁面碰撞进行充分汽化吸热;随着流量的增大,喷雾对管壁和出口降温效果的影响程度相似,喷雾雾滴的汽化受喷雾流量的影响,流量越大喷雾雾滴汽化长度越长。

In order to study the influence of non-uniform inlet conditions on the internal flow field, evaporation motion trajectory of spray droplet, and cooling effect during the spray cooling process in the exhaust pipe of a gas turbine, a spray cooling numerical study based on the Realizable k-ε model combined with the wall function and DPM model was conducted. The influence of the distribution of spray nozzle positions, different spray droplet diameters and spray flow rates on the pipe wall and outlet cooling effect under non-uniform inlet conditions was explored. The exhaust pipe was a cylindrical pipe with an equal diameter of 1.524 m, a front straight section of 5 m, a rear straight section of 8 m and a turning radius of 2.8 m. The cone angle of spray jet was 45°, the velocity was 30 m/s and the temperature was 328.15 K. The study shows that under non-uniform inlet conditions, the best cooling effect are obtained with non-uniformly distributed spary nozzles concentrated in the high temperature region, with a wall temperature drop of 111.08 K and an outlet temperature drop of 97.14 K, and the effect of the number of nozzle rows on the cooling effect is small. The standard deviations of the pipe outlet planar velocity distribution before and after spray cooling are 12.77 and 11.14 m/s, respectively, indicating that spray can improve the uniformity of the flow field in the straight section. Non-uniform inlet conditions have a greater impact on droplet smaller than 25 μm in diameter, with rapid evaporation and insufficient vaporization heat absorption due to insufficient collision with the wall. As the flow rate increases, the influence of spray on the pipe wall and outlet cooling effect is similar, and the vaporization of spray droplet is affected by the spray flow rate, with larger flow rates resulting in longer vaporization lengths of spray droplet.