封严涂层脱落对高压压气机性能影响的数值模拟

Numerical Simulation on High-pressure Compressor Performance Affected by Fall-off of Seal Coating

目的研究封严涂层脱落对高压压气机转子工作稳定性、流场结构的影响。方法以某型航空发动机高压压气机末端第12级转子作为研究对象,生成单通道网格,选择Spalart-Allmaras一方程湍流模型,采用数值模拟的方法研究了起飞工况、不同脱落厚度下的叶栅通道内的流动特性。结果随着封严涂层脱落,高压压气机效率和总压比均降低,失速裕度呈指数型下降;脱落厚度为4τ时,工作流量下压气机达到近失速边界。工作流量下,随着封严涂层脱落,叶尖泄漏涡与来流交界面、二次泄漏流进入泄漏涡的位置前移,出现后返流和在叶尖前部反复泄漏的流线;脱落厚度≥3τ后,叶尖通道后部泄漏涡涡核剧烈膨胀,出现显著的低速团。非定常数值模拟中,脱落厚度为4τ时,叶尖泄漏流呈现出显著的周期性和自诱导非定常性,并存在瞬时涡破碎现象。结论封严涂层的脱落会大幅度降低高压压气机的工作稳定性,其主要影响因素为叶尖泄漏涡、二次泄漏流与主流相互作用形成的复杂流动及低速团,并具体表现为叶尖通道流场的非定常性。

The work aims to study the working stability and the flow field structure of high-pressure compressors affected by fall-off of seal coating.The 12th-stage rotor of a high-pressure compressor was taken as the research object,and its single passage grid was generated so as to investigate the flow characteristics by numerical simulation under the taking-off condition and different fall-off thickness with Spalart-Allmaras one-equation turbulence model.As the seal coating fell off,the efficiency and the total pressure ratio decreased,and the stall margin declined exponentially in particular.The compressor reached the stall margin at 4τfall-off thickness under the working flow rate.Under the working flow rate,the fall-off of seal coating led to a moving forward of the tip leakage vortex/incoming flow interface and the position that the secondary leakage flow entered the leakage vortex.Meanwhile,the backflow and repeated streamlines leakage in front of the blade tip could be observed.After the fall-off thickness was greater than 3τ,the leakage vortex core in the rear tip passage expanded violently,and a remarkable low-velocity region appeared.The unsteady simulation showed that when the fall-off thickness increased to 4τ,the tip leakage flow exhibited significant periodicity and self-induced unsteadiness,accompanied by instantaneous vortex breakdown phenomenon.Therefore,the fall-off of seal coating can dramatically degrade the working stability of the high-pressure compressor,and the main influencing factors are complicated flow and low-velocity region produced by the interaction of tip leakage vortex,secondary leakage flow and the main flow,which presents the unsteadiness of the flow field in the tip area.