Topology optimization of turbine disk considering maximum stress prediction and constraints

For the stress-constrained topology optimization of a turbine disk under centrifugal loads, the jagged boundaries of the mesh and the gray densities on the solid/void interfaces could make the calculated stress field inconsistent with the actual value. It may result in overestimating the maximum stress and thus affect the effectiveness of stress constraints. This paper proposes a new method for predicting the maximum stress to overcome the difficulty. In the process, a predicted density is newly defined to obtain stable boundaries with thin layers of gray elements, a transition factor is innovatively proposed to evaluate the effects of intermediate-density elements, two different stiffness penalty schemes are flexibly used to calculate the elastic modulus of elements, and a linear stress penalty is further adopted to relax the stress field of the structure. The proposed approach for predicting the maximum stress value is verified by the analysis of a structure with smooth boundaries and the topology optimization of a turbine disk. An updating scheme of the stress constraint in the topology optimization is also developed using the predicted maximum stress. Some key ingredients affecting the optimization results are discussed in detail. The results prove the effectiveness and efficacy of the proposed maximum stress prediction and developed stress constraint methods.     

On a plastic instability criterion for ultra-large radial-axial ring rolling process with four guide rolls

A dynamic mechanical model is proposed to describe the complexing actions of all the rolls on the ring during the ultra-large radial-axial ring rolling(RARR) process with four guide rolls. Based on the model, the calculation models for bending moment and normal stress at any section of the ring are deduced by force method. If the maximum section bending normal stress exceeds the yield stress of the ring materials, the ring will be distorted thus leading to the instability of the RARR process. Ac...     

启动过程压缩空气储能向心涡轮三维流动特性研究

为研究压缩空气储能系统的向心涡轮启动过程内部流动损失特性，本文采用全三维计算流体动力学（CFD）模型对其启动过程过程进行了数值模拟，与实验结果对比表明，虽然该模型在启动初始阶段与转速稳定阶段存在一定误差，但仍能够整体上反映启动过程的效率变化特征。在此基础上，进一步分析了启动过程中动叶通道内损失区及流场变化特征，结果发现，动叶进口攻角是影响内部流场主要因素：在启动初始阶段，叶轮进口攻角较大，动叶载荷集中在叶片前缘，形成明显的通道分离涡与前缘涡；在快速启动段，攻角减小，动叶载荷沿弦长分布更为均匀，通道分离涡及前缘涡逐渐减小并向叶片吸力面迁移。在整个启动阶段，动叶通道内高损失区也随着通道分离涡逐渐迁移且变小，并向相邻叶片吸力面集中。     

超低空反导中的多径效应仿真

为得到超低空背景下目标特性参数对脉冲雷达导引头目标检测的影响,根据导引头和目标的空间几何关系,推导了波程差、多普勒频移、相位差的表达式,并结合比例导引法建立多径效应仿真模型。针对目标飞行参数进行仿真,并结合仿真结果对参数的影响效果进行了分析,为导引头末制导段的弹道规划与有效地规避多径效应提供参考依据。     

涡轮动叶部分吸力侧肩壁凹槽状叶顶气热和冷却性能研究

为了获取高性能的燃气涡轮动叶叶顶结构和气膜冷却布局，采用数值求解三维Reynolds-Averaged Navier-Stokes (RANS) 方程和标准 湍流模型的方法研究了涡轮动叶部分吸力侧肩壁的凹槽状叶顶气热和冷却性能。数值模拟得到的动叶平叶顶传热系数与实验数据吻合良好，验证了数值方法的准确性。对比0.95吹风比时动叶凹槽状叶顶沿中弧线和近压力侧布置的2种气膜冷却布局的叶顶泄漏流动形态、传热系数和气膜冷却有效度，指出近压力侧的气膜冷却布局B的总压损失大于沿中弧线的气膜冷却布局A；但近压力侧的气膜冷却布局B具有更好的冷却效果。基于近压力侧气膜冷却布局的凹槽状叶顶结构，通过切除尾缘处不同轴向长度的吸力侧肩壁，设计了5种不同的部分吸力侧肩壁的叶顶结构。结果表明：切除10%吸力侧肩壁的Case 7能有效降低总压损失，平均总压损失系数相比完整肩壁的Case 2降低了6.3%；叶顶净热流密度减少和传热系数分布与Case 2基本相同，尾缘处的冷却效率因冷气受到压制附着于叶顶而提高。     

船用多级轴流压气机低工况扩稳优化研究—“航海专刊”

对某型船用九级轴流压气机，为了探讨减少可转导叶列数的可行性，并提升低工况喘振裕度，本文通过数值模拟方法研究通流布局优化对压气机低工况稳定性的影响。通过特性分析和详细流场分析，结论表明，一维关键参数选取对最佳可转导叶控制策略影响较大，本文优化部分级关键参数，不仅减少了可转导叶列数，而且提升了低转速下的喘振裕度，在75%转速下喘振裕度提升了2.27%，在70%转速下喘振裕度提升了3.3%。     

超临界二氧化碳多槽型干气密封泄漏流动与动力特性研究

针对超临界二氧化碳（SCO₂）旋转机械面临的严重泄漏、气流激振引发转子失稳等问题，以美国通用电气公司10MWe SCO₂循环中高压涡轮的轴端密封为研究对象，设计了螺旋角15°和30°的螺旋槽、T型槽和ST型槽的四种槽型结构的干气密封。采用基于动网格技术和非定常CFD数值方法的微尺度摄动模型，研究了在实验边界条件下干气密封的稳态性能及在轴向简谐微扰动下SCO₂涡轮轴端干气密封的非稳态动力学特性。对比分析了3种动压槽深度、2种动压槽角度下的干气密封泄漏量、静态气膜刚度、动态气膜刚度和阻尼系数。研究表明：四种槽型均满足泄漏流量的设计要求。随着动压槽深度的增加，干气密封开启力与泄漏流量均增大。ST型槽干气密封有着较大的气膜刚度和刚漏比，同时其在面对轴向微尺度摄动时最为稳定，是综合性能最优秀的干气密封结构。     

Uncertainty analysis of measured geometric variations in turbine blades and impact on aerodynamic performance

Inevitable geometric variations significantly affect the performance of turbines or even that of entire engines; thus, it is necessary to determine their actual characteristics and accurately estimate their impact on performance. In this study, based on 1781 measured profiles of a typical turbine blade, the statistical characteristics of the geometric variations and the uncertainty impact are analyzed, and some commonly used uncertainty modelling methods based on PrincipalComponent Analysis(PCA)...     

火箭发动机涡轮泵转速遥测数据实时处理方法

火箭飞行试验过程中,一般通过连续处理测量设备输出的脉冲周期计算发动机涡轮泵转速.受测控站接力跟踪及接收条件限制,遥测数据存在不连续、短时中断等现象,极易造成数据处理错误.通过研究脉冲参数在传输时的状态及状态转移,并对实时跟踪时出现的数据中断、异常值处理等情况进行分析,提出一种基于有穷自动机理论的处理模型,有效解决了测量...     

某船载无人操控天线末段跟踪的数引策略改进

从无人操控天线需要依赖数引完成目标自动捕获以及现有的主动段航天测量的数引模型精度不够的背景出发,指出提高数引精度即进行数引改进的必要性。然后结合末段跟踪的特殊性,从时差、视差和延时累积误差三个影响数引精度的最主要方面详细分析了它们的形成机理,并给出了各自的改进方法。