考虑气膜冷却脉动特性的涡轮动叶凹槽状叶顶气动和冷却性能研究

Study on Aerodynamic and Cooling Performance of Turbine Blade Squealer Tip with Film Cooling Pulsation Characteristics Considered

为了深入研究压气机抽取的脉动冷气影响燃气涡轮动叶凹槽状叶顶的流动与冷却特性,采用数值求解三维非稳态雷诺时均N-S方程和标准k-ω湍流模型的方法,研究了考虑气膜冷却脉动特性的涡轮动叶凹槽状叶顶的气动和冷却性能。采用正弦函数描述动叶凹槽状叶顶中弧线等间距布置气膜冷却孔的冷气脉动特性,对比研究了3种脉动振幅和5种脉动频率的动叶凹槽状叶顶气膜冷却有效度和总压损失系数。研究结果表明:在一个脉动周期内,不同瞬时冷气的穿透能力和附着能力差异显著。气膜冷却冷气吹风比小幅值脉动时,脉动频率的提高改变了叶顶气膜冷却有效度变化曲线的相位,但对整体的冷却效果基本没有影响;冷气吹风比大幅值脉动时,脉动频率的增大略微提高了叶顶冷却性能,并且当脉动频率增大至最大值2000 Hz时,受到延迟反馈效应的影响,脉动周期内气膜冷却有效度的最低值相比250 Hz时提高约50%。高温主流在冷气吹风比大幅值脉动时周期性入侵冷气管路,对叶顶中间弦长和尾缘处的气膜孔结构造成破环。气膜冷却冷气吹风比低频脉动时,动叶平均总压损失系数以正弦函数规律变化,不同瞬时的总压损失系数差异随冷气吹风比脉动幅值的增大而扩大,同时当脉动频率增加时,不同瞬时之间的总压损失系数差异逐渐缩小。研究工作可为考虑气膜冷却脉动特性影响下动叶叶顶的气热性能分析提供参考。

To study how the pulsating coolant extracted from the compressor affect the flow and cooling characteristics of the squealer tip of a gas turbine blade,the aerodynamic and cooling performance of the turbine blade squealer tip with film cooling pulsation characteristics is studied by numerically solving three-dimensional unsteady Reynolds-averaged Navier-Stokes(URANS)equations and using the standard k-ωturbulence model.Nine film holes are arranged along the middle camber line of the squealer tip at equal intervals,and sinusoidal function is used to describe the discipline of the coolant pulsation.The tip film cooling effectiveness and total pressure loss coefficient are compared and studied at three pulsating amplitudes and five pulsating frequencies.The results show that there are obvious differences in the coolant penetration and adhesion at different instants in a pulsating cycle.When the coolant blowing ratio fluctuates slightly,the increase of the pulsating frequency changes the phase of the tip film cooling effectiveness curve,but has no effect on the overall cooling performance.However,when the coolant blowing ratio fluctuates greatly,the increase of the pulsating frequency will slightly improve the tip cooling efficiency,and affected by the delayed feedback effect,as the pulsating frequency increases to the maximum value of 2000 Hz,the lowest value of film cooling effectiveness is increased by about 50%compared to 250 Hz during the pulsation period.The high-temperature mainstream periodically invades the coolant pipeline with the large amplitude pulsation,causing damage to the original structure of the film holes at the tip middle chord and trailing edge.The averaged total pressure loss coefficient follows the law of sinusoidal function when the coolant blowing ratio pulsates with a low frequency,the total pressure loss difference increases at varied instants with the pulsating amplitude enlargement.Meantime,the difference gradually decreases when the pulsating frequency increases.This study can provide the reference for the aerothermal performance analysis of the turbine blade squealer tip with consideration of the film cooling pulsation characteristics.