Loss Evolution Characteristics Analysis of Micro Axial-Flow Turbine under Off-Design Conditions
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摘要: 针对微型水下航行器在宽速域运行条件下微型轴流式汽轮机面临的效率问题, 开展了变工况损耗演化机理研究。基于Modelica语言构建了热-机-流多物理场耦合机理模型, 引入了轮盘摩擦损失、部分进汽损失、叶顶间隙泄漏损失及余速损失等微尺度非线性损耗修正。通过典型任务剖面的瞬态仿真与全速域参数扫描, 揭示了变工况过程中损耗机制的阶段性演变: 低速巡航阶段, 余速损失、轮盘摩擦损失与部分进汽损失占比相近, 形成三者协同主导的局面, 同时泄漏损失构成较为稳定的损耗; 高速突击阶段, 部分进汽损失与轮盘摩擦损失成为主导损耗源。进一步研究表明, 系统性能受运行参数与几何参数显著影响: 提高进口压力和进口温度可降低损耗占比, 但是要注意进口参数和气动特性的匹配; 控制叶顶间隙、适当增大部分进汽度并采用偏小的动叶出口角, 可有效抑制动能耗散与微尺度损失, 改善全工况效率。研究结果为微型动力系统的能量管理、高效运行区间界定及结构优化提供了理论依据与仿真支撑。Abstract: To address the efficiency issues of micro axial-flow turbines in micro undersea vehicles operating over a wide speed range, a study on the evolution mechanism of off-design condition losses was carried out. A thermo-mechanical-fluid multiphysics coupling model was developed based on the Modelica language. Micro-scale nonlinear loss corrections were introduced, such as disk friction loss, partial admission loss, tip clearance leakage loss, and leaving velocity loss. Through transient simulations under a typical mission profile and full-speed-range parameter sweeps, the stage-wise evolution of the loss mechanism under off-design conditions was revealed. During low-speed cruise, leaving velocity loss, disk friction loss, and partial admission loss share comparable contributions, forming a co-dominant regime, while leakage loss remains relatively stable. During high-speed dash, partial admission loss and disk friction loss become the dominant loss sources. Further investigation shows that system performance is significantly influenced by both operating and geometric parameters. Higher inlet pressure and temperature can reduce the loss proportion, but proper matching between inlet parameters and aerodynamic characteristics must be ensured. Kinetic energy dissipation and micro-scale loss can be effectively suppressed by controlling tip clearance, appropriately increasing partial admission ratio, and adopting a small rotor exit angle, thereby improving the efficiency over the whole operating conditions. The findings provide a theoretical basis and simulation support for energy management, definition of high-efficiency operating intervals, and structural optimization of micro power systems.
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Key words:
- micro undersea vehicle /
- power system /
- off-design condition /
- loss evolution /
- multiphysics modeling /
- Modelica
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图 1 Li/SF6闭式循环动力系统原理结构图
Figure 1. Principle structural diagram of Li/SF6 closed-cycle power system
图 2 动力系统热-机-流耦合集成模型结构
Figure 2. Structural diagram of thermal-mechanical-fluid coupling integrated model for power system
图 4 变工况过程中各项损失演化曲线
Figure 4. Evolution curves of various losses during the variable operating condition process
图 6 不同进口压力下内效率变化曲线
Figure 6. Change curves of internal efficiency under different inlet pressures
图 7 不同进口温度下内效率变化曲线
Figure 7. Change curves of internal efficiency under different inlet temperatures
表 1 稳态工况仿真与实验数据对比
Table 1. Comparison between simulation and experimental data under steady-state conditions
项目 相对实验值 相对仿真值 相对误差/% 汽轮机转速 nref 0.97nref 2.68 出口蒸汽温度 Tout,ref 0.93 Tout,ref 7.46 蒸汽流量 $ \dot{m}_{\mathrm{ref}} $ $0.96{m_{{\mathrm{ref}}}} $ 4.16 汽轮机功率 Pt,ref 0.96Pt,ref 4.37 
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