Aerodynamic optimization for elbow-type exhaust duct with a built-in output shaft tube
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摘要:
分析了带输出轴的肘弯式排气管直扩压段扩张角度(
α =4°~28°)、弯曲段弯曲角度(β =55°~75°)和下壁面引导线F 值(F =0.15~0.75)这三个决定性结构参数对其气动性能的影响;基于响应面模型和多目标遗传算法进行了排气管气动性能优化。结果表明:弯曲排气管内的流动损失主要来源于弯曲管内侧回流、中心套管和支板绕流尾迹涡,排气管中偏转气流和内置构件复杂绕流的耦合流动是其气动损失物理机制。在给定的参数范围内,单一结构参数对排气管总压损失和静压恢复的影响规律均具有很强的非单调变化。相较单因素分析中的特定优选模型(α =16°、β =60°和F =0.6),多目标优化后的排气管具有更大的直扩压段扩张角度(α =18.36°~18.95°)和更小的弯曲段下壁面引导线F 值(F =0.39~0.48),弯曲角度基本相当(β =60.2°~65°),排气管的流通能力得到进一步提升。Abstract:Numerical simulations were performed for the internal flow inside an elbow-type exhaust duct with a built-in output shaft tube. Given the constrained condition relating to the section contours and locations of inlet and outlet, three geometric parameters were mainly considered to illustrate their individual effect on the aerodynamic performances respectively, including straight diffuser angle (
α =4°—28°), bent angle (β =55°—75°) and lower guide lineF value (F =0.15—0.75) of the exhaust duct. Furthermore, an optimization and sensitivity analysis was made by using the response surface methodology and multiobjective genetic algorithm. The results showed that the flow losses mainly originated from the recirculating flow near inner-side bent section, the wake vortices behind the central tube and struts. The flow deflection inside the bent duct and the cross flow around built-in components were coupled together to form very complicated flow fields and flow loss mechanisms. Within the present scope, non-monotonous influencing role behaved clearly for each individual geometric effect on the total pressure loss coefficient and the static pressure recovery coefficient. Compared with the specifically preferred situation obtained from single-factor analysis (α =16°,β =60° andF =0.6), the optimized elbow-type exhaust duct had a greater straight diffuser angle (α =18.36°—18.95°) and smaller lower guide lineF value (F =0.39—0.48), with nearly consistent bent angle (β =60.2°—65°). It improved the aerodynamic performances effectively. -
表 1 基准排气管结构参数
Table 1. Geometric parameters in baseline exhaust duct
参数 数值 Dm/D0 0.510 L0/D0 0.121 α/(°) 4 Ls/D0 0.164 Lt/D0 0.95 Ht/D0 1.05 R21/D0 0.529 R22/D0 0.265 R23/D0 1.058 A2/A0 1.3 W2/H2 1.65 F 0.6 β/(°) 60 表 2 排气管设计变量
Table 2. Selected design variables for current exhaust duct
参数 设计范围 取值 扩张角度α/(°) 4~28 4,10,16,22,28 弯曲角度β/(°) 55~75 55,60,65,70,75 下引导线F 0.15~0.75 0.15,0.3,0.45,0.6,0.75 表 3 总压损失系数和静压恢复系数计算结果
Table 3. Calculation results of total pressure loss coefficient and static pressure recovery coefficient
序号 α/(°) β/(°) F Ctp Csp 1 10 60 0.3 0.128 0.359 2 16 65 0.3 0.085 0.403 3 22 60 0.6 0.099 0.421 4 22 60 0.3 0.105 0.396 5 16 55 0.3 0.119 0.416 6 16 60 0.45 0.091 0.432 7 22 65 0.45 0.087 0.418 8 22 55 0.45 0.132 0.392 9 16 65 0.6 0.091 0.398 10 16 60 0.45 0.091 0.432 11 10 55 0.45 0.14 0.378 12 16 60 0.45 0.091 0.432 13 10 65 0.45 0.12 0.312 14 16 60 0.45 0.091 0.432 15 16 60 0.45 0.091 0.432 16 16 55 0.6 0.11 0.41 17 10 60 0.6 0.123 0.318 表 4 总压损失系数的ANOVA结果
Table 4. ANOVA results for total pressure loss coefficient
变异来源
(source)SS DOF MS F统计值 P值 回归模型整体(model) 0.0051 9 0.0006 131.82 < 0.0001 α 0.0010 1 0.0010 229.65 < 0.0001 β 0.0017 1 0.0017 411.17 < 0.0001 F 0.0000 1 0.0000 6.05 0.0435 αβ 0.0002 1 0.0002 35.33 0.0006 αF 0.0001 1 0.0001 0.17 0.6935 βF 0.0001 1 0.0001 12.61 0.0093 α2 0.0018 1 0.0018 397.52 < 0.0001 β2 0.0003 1 0.0003 62.14 < 0.0001 F2 0.0000 1 0.0000 4.44 0.0731 残差
(residual)0 7 0 失拟项
(lack of fit)0 3 0 纯误差
(pure error)0 4 0 校正总和
(corrected total)0.0051 16 决定系数R2为 0.9941 ,调整R2为0.9866 ,预测R2为0.9061 表 5 静压恢复系数的ANOVA结果
Table 5. ANOVA results for static pressure recovery coefficient
变异来源(source) SS DOF MS F统计值 P值 回归模型整体(model) 0.0227 9 0.0025 223.34 < 0.0001 α 0.0084 1 0.0084 741.97 < 0.0001 β 0.0005 1 0.0005 45.06 0.0003 F 0.0001 1 0.0001 7.89 0.0262 αβ 0.0021 1 0.0021 184.94 < 0.0001 αF 0.0011 1 0.0011 97.31 < 0.0001 βF 0 1 0 0.0221 0.8859 α2 0.0086 1 0.0086 757.98 < 0.0001 β2 0.0006 1 0.0006 52.03 0.0002 F2 0.0007 1 0.0007 64.35 < 0.0001 残差(residual) 0.0001 7 0 失拟项
(lack of fit)0.0001 3 0 纯误差
(pure error)0 4 0 校正总和(corrected total) 0.0228 16 决定系数R2为 0.9965 ,调整R2为0.9911 ,预测R2 为0.9445 表 6 优化的设计参数取值范围
Table 6. Range of optimized design parameters
参数 取值范围 α/(°) 18.36~18.95 β/(°) 60.2~65 F 0.39~0.48 表 7 优化设计点的气动性能
Table 7. Aerodynamic performance at the optimized design points
模型 参数 $ {C}_{\text{tp}} $ $ {C}_{\text{sp}} $ α/(°) β/(°) F CFD计算值 RSM预测值 CFD计算值 RSM预测值 Ref-1 16 60 0.6 0.095 0.412 Ref-2 4 60 0.6 0.213 0.079 Ref-3 4 60 0.45 0.191 0.165 Opt-A 18.74 62.39 0.473 0.085 0.084 0.442 0.436 Opt-B 18.36 60.25 0.468 0.090 0.089 0.434 0.438 -
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