Research on the influence and mechanism of diffusers on the aerodynamic performance of high-load axial compressors
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摘要:
为探明扩压器对先进高负荷轴流压气机气动性能的影响及机理，选用某型带有扩压器结构的2.5级高负荷轴流压气机为研究对象，借助经过校核的数值计算方法系统深入地开展了扩压器的引入及扩张角分配对压气机/扩压器耦合匹配工作性能的影响及机理研究。结果表明：扩压器上、下壁面扩张角分配能够显著影响高负荷轴流压气机气动性能，定扩张比下随着扩压器下壁面扩张角
α 增大，压气机/扩压器耦合流量裕度呈先增加后减小的变化趋势，存在最佳下壁面扩张角（α ≈ 7°）使其耦合流量裕度提高11.5%。扩压器上、下壁面扩张角分配通过改变压气机出口气流参数径向分布来调节流动最先失稳部位和耦合流量裕度，下壁面扩张角α 较小时压气机末级静子叶根因角区分离而最先失稳，而α 的增加将抑制末级静子叶根低能流体迁移堆积并改善来流攻角，进而不断提高压气机/扩压器耦合流量裕度，直至α ≈ 7°时压气机末级转子因叶尖流动分离堵塞而先于末级静子失稳；进一步增加下壁面扩张角α 将诱发扩压器内流动分离加剧，使得扩压器先于压气机发生流动失稳，导致压气机/扩压器耦合流量裕度逐渐降低。Abstract:To investigate the influence and mechanisms of the diffuser on the aerodynamic performance of an advanced high-load axial flow compressor, a 2.5-stage high-load axial flow compressor coupled with a diffuser was selected as the research subject, using validated numerical simulation methods. A systematic and deep study was carried out on the impact and mechanism of the introduction of the diffuser and divergence angle distribution on the performance of the compressor/diffuser coupling matching. The results showed that the divergence angle distribution of the diffuser upper/lower wall can significantly affect the aerodynamic performance of the high-load axial flow compressor. Under a constant area ratio, as the divergence angle
α of the diffuser lower wall changed from small to large, the coupled stall margin of the compressor and diffuser initially increased and then decreased. There was an optimal lower wall divergence angle (α ≈ 7°), which increased the coupling stall margin by 11.5%. The divergence angle distribution of the diffuser upper/lower wall adjusted the first unstable part of the flow and the coupled stall margin by changing the radial distribution of the compressor outlet airflow parameters. When the lower wall divergence angleα was smaller, the compressor final stage stator blade root was the first to become unstable due to angle zone separation, and the increase inα could inhibit the migration and accumulation of low fluid at the root of the final stator blade and improve the inflow incidence, thereby continuously improving the compressor/diffuser coupled stall margin until the final stage rotor of the compressor became unstable before the final stage stator due to tip flow separation blockage whenα ≈ 7°; further increasing the lower wall divergence angleα could induce intensified flow separation in the diffuser, causing the diffuser to become unstable before the compressor, leading to a gradual decrease in the coupling stall margin of the compressor and diffuser. -
图 1 带有扩压器结构的2.5级高负荷轴流压气机子午流道示意图
Figure 1. Schematic diagram of the meridional flow channel of a 2.5-stage high-load axial compressor with a diffuser structure
图 2 扩压器流道参数化设计示意图
Figure 2. Schematic diagram of parameterized design for the flow passage of the diffuser
图 3 计算域网格与末级静子后缘局部网格放大示意图（单位：mm）
Figure 3. Computation domain grid and local grid enlargement diagram of final stator trailing edge （unit：mm）
图 4 不含扩压器的压气机的网格独立性验证
Figure 4. Validation of grid independence of the compressor without diffuser
图 5 2.5级压气机特性线数值与实验结果校核
Figure 5. Comparison between the simulation and experimental results of the 2.5-stage compressor
图 6 不同下壁面扩张角α下压气机与扩压器耦合特性线
Figure 6. Coupling characteristic curves of compressor and diffuser under different lower wall divergence angles α
图 7 不同下壁面扩张角α下压气机与扩压器的流量裕度和峰值效率相较于原型变化趋势示意图
Figure 7. Schematic diagram of the changing trends of stall margin and peak efficiency relative to the baseline at different lower wall divergence angles α
图 8 流量为4.44 kg/s时，baseline与α分别为−1°、6°和7°时在10%、50%和90%叶高处Marel分布云图
Figure 8. Marel distribution contour at 10%, 50% and 90% span for operating point of 4.44 kg/s when α is −1°, 6°, 7° and baseline
图 9 流量为4.44 kg/s时，baseline与α分别为−1°、6°和7°时末级静子在10%、50%和90%叶高处叶片静压系数沿轴向分布
Figure 9. Axial distribution of the static pressure coefficient of final stator blade at 10%, 50%, and 90% span for the baseline and α of −1°, 6° and 7° for mass flow rate of 4.44 kg/s
图 10 流量为4.44 kg/s时，baseline与α分别为−1°、6°和7°时末级静子后10%轴向弦长位置处静压系数沿径向分布
Figure 10. Radial distribution of static pressure coefficient at 10% axial chord length position after the final stage stator for the operating point of 4.44 kg/s when α is −1°, 6° and 7° and baseline
图 11 流量为4.44 kg/s时，baseline与α分别为−1°、6°和7°时末级静子内部三维流动特性图
Figure 11. Three-dimensional flow characteristics contour inside the final stage stator for the operating point of 4.44 kg/s when α is −1°, 6° and 7° and baseline
图 12 在流量为4.33 kg/s的近失稳工况点10%、50%和95%叶高处Marel分布云图（α=7°）
Figure 12. Marel distribution contour at 10%, 50% and 95% span for the operating point of 4.33 kg/s （α=7°）
图 13 末级转子在99%叶高处静压系数分布云图（α=7°）
Figure 13. Static pressure coefficient distribution contour at 99% span of the final rotor （α=7°）
图 14 末级转子在99%叶高处熵分布云图（α=7°）
Figure 14. Entropy distribution contour at 99% span of the final rotor （α=7°）
图 15 末级转子在子午面内叶尖周向平均熵分布云图（α=7°）
Figure 15. Circumferential averaged entropy distribution on the meridional plane of the final stage rotor （α=7°）
图 16 末级转子叶片通道中堵塞因子B沿相对轴向弦长的分布（α=7°）
Figure 16. Distribution of the final stage rotor blade channel blockage factor B along the relative axial chord length （α=7°）
图 17 末级转子分别在其近失稳工况点的99%叶高截面静压系数和熵分布（α=7°，18°）
Figure 17. Static pressure coefficient and entropy distribution at 99% span for the near stall point （α=7°，18°）
图 18 末级转子内部流场涡系结构
Figure 18. Vortex structure of internal flow field in the final stage rotor
图 19 末级转子分别在其近失稳工况点的堵塞因子B沿相对轴向弦长的分布（α=7°，18°）
Figure 19. Blockage factor distribution of the final stage rotor along relative axial chord at near stall point （α=7°，18°）
图 20 在近堵塞点、峰值效率点和近失稳点时子午面相对马赫数分布（α=7°，18°）
Figure 20. Relative Mach number distribution on meridian plane for the near-choke point，peak efficiency point，and near-stall point （α=7°，18°）
图 21 压气机出口气流角沿径向分布（α=18°）
Figure 21. Distribution of compressor outlet airflow angle along the radial direction （α=18°）
表 1 2.5级高负荷轴流压气机主要几何设计参数
Table 1. Main geometric and design parameters of 2.5-stage high-load axial flow axial flow compressor
参数 数值 进口总温/K 288.15 进口总压/Pa 101325 设计流量/（kg/s） 4.6 设计转速/（r/min） 25000 设计总压比 2.7 设计等熵效率 0.865 转子外径/mm 276 出口马赫数 0.42 
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表 2 不同扩张角分配类型
Table 2. Allocation of different divergence angles
结构类型 α/（°） β/（°） 扩张类型 Baseline 0 0 Case 1 −1 10.0 ① Case 2 4 6.2 ② Case 3 6 4.7 ② Case 4 7 4.0 ② Case 5 8 3.3 ② Case 6 10 1.8 ② Case 7 14 −1.2 ③ Case 8 18 −4.1 ③
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