一种新的低温透平膨胀机优化设计方法

为了提高低温透平膨胀机的等熵效率，正确选择影响透平膨胀机性能的各主要参数（特性比u^-1,反动度ρ及轮径比μ）十分重要。为此，提出了一种新的基于遗传算法（Genetic Algorithm)的透平膨胀机优化设计方法，该优化方法无需给出显式的目标函数，无需求导和微分，可以方便地加入专家经验以提高搜索效率，并且在优化过程中可以全面地考虑约束条件，优化结果能够直接用于实际，应用该优化设计方法对一小流量低温透平膨胀机（用于逆Brayton循环制冷机）的设计变量进行优化，结果表明该优化设计方法是行之有效的。     

低温透平膨胀机叶轮逆命题设计方法的研究

系统地提出了低温用透平膨胀叶轮跨盘盖子午面三维逆命题设计方法，首次将控制涡ｒＶθ（平均预旋）用于透平膨胀机的逆命题设计中，并将流线曲率法用于叶轮内部流场的计算。假定流体是无粘的、定常的，同时假定进口无旋。和正命题计算的结果比较表明，该方法所得叶片内部速度场分布明显优于正命题，叶型光滑，扭曲适度。     

小型低温透平膨胀机直线圆弧喷嘴的设计

详细分析了小型低温透平膨胀机直线圆弧喷嘴的几何结构,在此基础上提出了一种新的较准确的设计方法,并通过计算实例同以往的直线圆弧喷嘴设计方法进行了比较。     

采用不同损失模型的低温透平膨胀机性能分析

针对氦气低温透平膨胀机变工况热力性能预测,研究了透平膨胀机各通流部分损失机理,并根据一维无量纲流动控制方程,采用基于焓降的损失系数分析了各部件内流动损失,结合各部件流动特性,确定了适合各通流部件的损失系数计算关联式,进一步开展了氦低温透平膨胀机变膨胀比和变转速的热力性能模拟研究,绘制了透平性能曲线,获得了透平膨胀机变膨...     

新型动压箔片径向气体轴承低温透平膨胀机的开发

针对一台40Nm^3/h的空气低温透平膨胀机，设计了一种新型弹性支承箔片径向气体轴承。并对该透平膨胀机的机械性能做了大量试验，试验获得最大转速为220000r/min。试验表明，该箔片动压气体轴承低温透平膨胀机具有很好的运转稳定性，对进一步开发我国自己的全动压气体轴承低温透平膨胀机具有重要的意义。     

氦低温透平膨胀机的设计和内部流动特性研究

为验证氦低温膨胀机叶片设计的有效性,利用了NUMECA和CFX软件对设计透平流道进行设计工况下的数值模拟计算及分析,其中分别对工作轮流道、喷嘴流道和整体流道进行计算分析,获得了较好的温度场、压力场、相对速度场分布和较高的等熵效率,结果表明了数值计算结果是可信的,叶型设计是合理的。     

产品操作界面元素布局多目标优化设计

目的针对产品设计中操作界面布局设计时存在的随意性、不确定性大等问题,使用多目标优化设计的方法,寻找界面元素的最优布置,以提升界面的使用舒适性和人机交互效率。方法在分析了工效学准则和界面布局美度评价准则的基础上,确立了层次性、相关性、简洁性和舒适性四个界面布局基本原则,并依据原则构建了界面元素布局多目标优化数学模型,在此模型的基础上采用改进的遗传算法,建立基于遗传算法的界面元素布局多目标优化方法。结果给出产品操作界面布局设计的基本原则,提出一种基于遗传算法的产品操作界面元素布局的多目标优化方法及流程。结论提出的布局原则和优化方法能较好地协助设计师获得满足设计需求的布局方案,实例结果表明了理论模型的合理性与遗传算法对于界面元素布局多目标优化问题求解的有效性。     

《基于多目标遗传算法的消声器优化设计》

四端网络法结合遗传算法设计消声器。以四端子网络为理论基础建立消声器的插入损失、传递损失、噪声降低的模型,模拟计算出消声器的消声特性响应曲线。应用多目标遗传算法对得到的消声器的噪声特性进行优化,结果使消声器的消声性能得到明显的改善,可以缩短设计周期,提高效率。     

基于模糊理论的机械多目标优化设计

多目标优化设计各分目标间的矛盾性和不可公度性增加了解决问题的难度,常规求解多目标优化设计方法一般只能求出问题的有效解,而得不到设计的最优结果。该文以蜗杆传动多目标优化设计为例,采用改进的遗传算法求得若干有效解后,根据模糊理论中的相似优先比法从中确定出最有效解,即最优解,并可排出它们的优劣顺序。     

最小偏差法在机械多目标优化设计中的应用

提出了处理多目标问题的最小偏差法,并将其应用于机械多目标优化设计。以流体动压滑动轴承多目标优化设计为例,建立了以摩擦系数最小、发热量最小和承载能力最大为目标函数的多目标优化设计数学模型,根据最小偏差法原理构造统一目标函数,利用改进遗传算法对该问题进行了优化设计。算例整个求解过程和结果表明,该方法既可以避免人为因素的影响,又能够获得比常规设计更佳的设计参数,同时也验证了所提方法对于解决机械多目标优化设计问题的有效性和可行性。     

行波热声发动机的优化设计

对行波热声发动机进行了优化设计，对回热器内部功的损失和回热器的热漏损失进行了分析，给出了行波热声热回热器的优化结构，对于设计行波型热声发动机有非常重要的理论指导意义。     

空冷式冷凝器的优化设计

主要介绍了空冷式冷凝器的优化设计的实现技术。该程序采用VisualC 开发工具，具有良好的人机交互界面。开发的应用程序以参数化设计为原则，并贯穿了模块化设计思想，具有一定的通用性。     

透平膨胀机钎焊叶轮超速试验后的检验

钎焊是高速透平膨胀机铝合金闭式叶轮制造中的一种重要方法，有限元分析（FEA）方法可以了解闭式叶轮在离心力场下的应力及变形的3D分布，并预测轮盘与轮盖钎接缝上的应力大小和变化趋势，及叶轮的最大应力发生区域和最大变形产生位置，有限元分析结果表明，叶轮超速试验后，应注意轮盖内孔钎接区域附近微裂纹的检测，同时在轮盖内孔及外缘处测量超速后的残余弹性变形。     

COMPARATIVE EVALUATION OF DIFFERENT OPTIMIZATION ALGORITHMS FOR STRUCTURAL DESIGN APPLICATIONS

Non-linear programming algorithms play an important role in structural design optimization. Fortunately, several algorithms with computer codes are available. At NASA Lewis Research Centre, a project was initiated to assess the performance of eight different optimizers through the development of a computer code CometBoards. This paper summarizes the conclusions of that research. CometBoards was employed to solve sets of small, medium and large structural problems, using the eight different optimizers on a Cray-YMP8E/8128 computer. The reliability and efficiency of the optimizers were determined from the performance of these problems. For small problems, the performance of most of the optimizers could be considered adequate. For large problems, however, three optimizers (two sequential quadratic programming routines, DNCONG of IMSL and SQP of IDESIGN, along with Sequential Unconstrained Minimizations Technique SUMT) outperformed others. At optimum, most optimizers captured an identical number of active displacement and frequency constraints but the number of active stress constraints differed among the optimizers. This discrepancy can be attributed to singularity conditions in the optimization and the alleviation of this discrepancy can improve the efficiency of optimizers.     

ENHANCED MULTIOBJECTIVE OPTIMIZATION TECHNIQUE FOR MULTIDISCIPLINARY DESIGN

An enhanced multiobjective formulation technique, capable of emphasizing specific objective functions during the optimization process, has been demonstrated on a complex multidisciplinary design application. The Kreisselmeier - Steinhauser (K-S) function approach, which has been used successfully in a variety of multiobjective optimization problems, has been modified using weight factors which enables the designer to emphasize specific design objectives during the optimization process. The technique has been implemented in two distinctively different problems. The first is a classical three bar truss problem and the second is a high-speed aircraft (a doubly swept wing-body configuration) application in which the multiobjective optimization procedure simultaneously minimizes the sonic boom and the drag-to-lift ratio (C_D/C_L) of the aircraft while maintaining the lift coefficient within prescribed limits. The results are compared with those of an equally weighted K-S multiobjective optimization. Results demonstrate the effectiveness of the enhanced multiobjective optimization procedure.     

A SHAPE AND SIZE OPTIMIZATION ALGORITHM FOR MACHINE TOOL ELEMENT DESIGN

A shape and size optimization algorithm is developed to incorporate the shape and size variables in a recently developed machine tool simulation and design methodology known as Integrated Machining Process Design Simulator (IMPDS). This shape optimization algorithm, using coordinates of master nodes, parameters of geometric equations, coordinate linking and symmetry option approaches presents a general and flexible way of controlling and optimizing the structural shape of machine tool elements. An application of the proposed shape and size optimization algorithm indicates that the shape and size parameters have significant effects on the structural characteristics and the dynamic behavior of machine tool elements.     

THE ROLE OF EVOLUTIONARY AND ADAPTIVE SEARCH DURING WHOLE SYSTEM,CONSTRAINED AND DETAILED DESIGN OPTIMIZATION

The paper introduces various strategies which incorporate evolutionary and adaptive search techniques. These strategies incorporate genetic algorithms (GA) and ant colony models combined within co-operating frameworks that provide a capability for decision support and optimization during whole system design and constraint satisfaction/ constrained optimization during the engineering design process. The objective during whole system design is to determine an optimum initial configuration for large engineering systems. Strategies for the efficient integration of evolutionary techniques with detailed design are also introduced. Each of these areas presents specific problems to the evolutionary/adaptive search processes and the overall objective here is to identify the main areas of difficulty and provide solutions that will lead to successful integration. The paper illustrates the flexibility and utility of the various techniques when applied across the various stages of the design process, i.e. from providing decision support during the high-risk stages of preliminary design to the identification of definitive optimal solutions during the more deterministic stages of detailed design.     

A MATHEMATICAL CONVERGENCE ANALYSIS OF THE CONVEX LINEARIZATION METHOD FOR ENGINEERING DESIGN OPTIMIZATION

This paper is concerned with the convex linearization method recently proposed by Fleury and Braibant for structural optimization. We give here a mathematical convergence analysis or this method. We also discuss some modifications of it.