Power balancing method in aero-engine whole-engine performance simulation
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摘要:
提出了一种在CFD三维整机仿真中实现功率平衡的计算方法。推导确定了决定平衡关系的关键变量:涡轮前温度与物理转速。提出了基于稳态流场和功率经验关系实现功率平衡的数值迭代方法。本文将该迭代方法与CFD三维求解耦合,发展了一种可用于三维整机CFD耦合仿真的功率平衡计算方法。采用该功率平衡计算方法对MTJ-80涡喷发动机开展了三维整机CFD数值计算,实现了整机性能三维仿真与控制规律的耦合和预测。在控制燃油量不变的条件下,通过转速迭代可以实现压气机和涡轮的功率差小于0.1%,可以预测固定燃油供给量条件下所能达到的稳态运转转速。在控制转速不变的条件下,通过调节燃油量实现压气机和涡轮的功率差小于0.15%,可以预测固定转速条件下的燃油流量。数据验证结果表明:该功率平很给计算方法可以与CFD三维整机计算耦合,并且具有很强的收敛性,解决了以往整机三维性能仿真过程中的功率不平衡问题。
Abstract:A calculation method of power balance in CFD 3D machine simulation was presented. The key variables determining the equilibrium relationship such as temperature before turbine and physical speed were deduced and determined. The numerical iterative method based on the steady state flow field and power empirical relationship was proposed to realize the power balance. The power balance calculation method was used to carry out the CFD numerical calculation of the MTJ-80 turbojet, and the coupling and prediction of the performance simulation and control law were realized. Under the condition of constant fuel quantity, the power difference between compressor and turbine can be less than 0.1% through speed iteration, and the steady running speed can be predicted under the condition of fixed fuel supply. Under the condition of constant control speed, the power difference between compressor and turbine was less than 0.15% by adjusting the fuel quantity, and the fuel flow rate under the condition of constant control speed can be predicted. The data verification results showed that the proposed method can be coupled with CFD 3D machine calculation with strong convergence, which solved the power imbalance problem in the previous 3D performance simulation of the machine.
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表 1 发动机关键设计参数及设计点性能
Table 1. Key engine design parameters and performance of design points
参数 符号 数值 发动机最大外径/mm ${r_{{\text{max}}}}$ 145 发动机核心长度/mm ${L_{{\text{core}}}}$ 470 进口支板数 ${N_{{\text{IS}}}}$ 6 叶轮(分流叶片)
叶片数${N_{{\text{CI}}}}$ 10(10) 径向扩压器叶片数 ${N_{{\text{RD}}}}$ 21 轴向扩压器叶片数 ${N_{{\text{AD}}}}$ 42 燃烧室燃油喷嘴数 ${N_{{\text{FSN}}}}$ 12 涡轮导叶数 ${N_{{\text{TGV}}}}$ 16 涡轮转子叶片数 ${N_{{\text{TR}}}}$ 29 出口支板数 ${N_{{\text{OS}}}}$ 4 换算转速/(r/min) ${{n} }$ 60000 燃油流量/(kg/s) ${\dot m_{{\text{fuel}}}}$ 0.0336 油气比 ${f_{\text{a}}}$ 0.015628 表 2 各组件网格节点数
Table 2. Number of mesh nodes of each component
组件 网格类型 节点 网格数 进口支板 六面体 726516 686955 离心叶轮 六面体 528583 489162 径向扩压器 六面体 188428 175362 轴向扩压器 六面体 97218 87822 燃烧室 四面体 112826 563418 涡轮导叶 六面体 176064 163701 涡轮转子 六面体 312145 294048 出口支板 六面体 403580 378147 总计 2545360 2838615 表 3 发动机性能参数
Table 3. Engine performance parameters
性能参数 数值结果 压气机总压比${\pi _{\text{c}}}$ 4.1235 燃烧室温升${\theta _{\text{4}}}$ 2.2248 涡轮前温度${T_{{\text{t4}}}}$/K 1060.86 涡轮总压膨胀比${\pi _{\text{t} } }$ 2.8256 油气比(燃油/进口流量)${f_{\text{a}}}$ 63.815 非安装推力${F_{{\text{ax}}}}$/kN 0.779 进口质量流量${\dot m_2}$/(kg/s) 2.1142 出口质量流量${\dot m_{\text{9}}}$/(kg/s) 2.1789 压气机扭矩${T_{{\text{qc}}}}$/(${\text{N}} \cdot {\text{m}}$) 65.057 涡轮扭矩${T_{{\text{qt}}}}$/(${\text{N}} \cdot {\text{m}}$) 71.723 表 4 方案 (12a) 不同迭代因子对流量迭代功率平衡计算的影响
Table 4. Scheme (12a) influence of different iteration factors on flow iteration power balance calculation for
算例 ${\dot m_{{\text{fuel}}}}$/
(kg/s)$ {\dot m_2} $/
(kg/s)${e_{{\text{mass}}}}$/
%${e_{{\text{torque}}}}$/
%${\pi _{\text{c}}}$ ${\theta _{\text{4}}}$ ${T_{{\text{t4}}}}$/K ${\pi _{\text{t}}}$ ${F_{{\text{ax}}}}$/kN 结果状态 Test_a2 ($\lambda = {\text{1}}{\text{.0}}$) 0.0263 2.147 0.033 −0.12 3.89 1.98 937.0 2.819 0.642 收敛 Test_a3 ($\lambda = {\text{5}}{\text{.0}}$) 0.0262 2.147 0.031 0.002 3.89 1.98 936.4 2.831 0.635 收敛 Test_a4 ($\lambda = {\text{8}}{\text{.0}}$) 0.0206 2.149 5.315 23.58 3.59 1.75 819.7 2.639 0.460 发散 表 5 方案12(b)不同迭代因子对流量迭代功率平衡计算的影响
Table 5. Scheme (12b) Influence of different iteration factors on flow iteration power balance calculation
算例 n/ (r/min) $ {\dot m_2} $/ (kg/s) ${e_{{\text{mass}}}}$/% ${e_{{\text{torque}}}}$/% ${\pi _{\text{c}}}$ ${\theta _{\text{4}}}$ ${T_{{\text{t4}}}}$/K ${\pi _{\text{t}}}$ ${F_{{\text{ax}}}}$/kN 结果状态 Test_b2 ($\lambda {\text{ = 0}}{\text{.5}}$) 64325 2.192 0.105 0.08 4.25 2.14 1067.0 2.863 0.808 收敛 Test_b3 ($\lambda {\text{ = 1}}{\text{.0}}$) 64283 2.192 0.005 0.01 4.25 2.14 1065.0 2.865 0.807 收敛 Test_b4 ($\lambda {\text{ = 1}}{\text{.2}}$) 65153 2.199 0.032 2.17 4.27 2.13 1074.4 2.885 0.797 未收敛 -
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