第6章 工程优化概述.pptVIP

6 工程优化 数学定义 优化发展史 优化问题分类 优化算法分类 热力系统优化：特殊性 热力系统优化：方法 Calculus methods：要求有显式的且连续可微的目标函数。仅适用于简单热力系统。 geometric programming：要求有显式的且连续可微的目标函数。适用于有大量实验数据可供曲线拟合的热力学系统。 Linear programming：很少能用于热力系统。因为热力系统的非线性性质 热力系统优化：方法 Dynamic programming：应用有限，主要用于流体管网设计 Search methods：应用最多 Optimization can mean many different things. However, mathematically speaking, it is possible to write an optimization problem in the generic form… where fi(x),jj(x) and \pk{x) are functions of the design vector… * 优化过程、优化现象无时无处不在。 动物如猫、狗已知两点之间直线距离最短。 生命体（动物、植物、微生物）优化自身以使能耗最低。 无生命物质如分子、原子、电子都处于能量最低态，光传播遵循最小作用量原理（费马原理）。 没有优化就没有生命。上帝是真正的优化大师。 但是只有人类把优化理论化，用于发明创造和生产生活。 * Ref: Xin-SheYang. Engineering Optimization An Introduction with Metaheuristic Applications. John Wiley Sons, Inc., 2010 * Ref: Xin-SheYang. Engineering Optimization An Introduction with Metaheuristic Applications. John Wiley Sons, Inc., 2010 * Several different optimization methods have been mentioned earlier and will be discussed in detail in later chapters. Some of these have only limited applicability with respect to thermal systems. Calculus methods require continuous functions that can be differentiated, and geometric programming requires sums of polynomials to characterize the system. Therefore, both of these methods can be used only if the system behavior can be represented by explicit, closed-form expressions. This is possible only for simple systems, with few components and idealized behavior, or for cases where curve fitting is employed to obtain representative equations. The latter approach is used for many systems, particularly for thermodynamic systems such as engines heating and cooling systems, where curve fitting can be effectively employed to represent material and process characteristics * Dynamic programming is of greater interest in thermal systems, particularly in networking of channels for material and fluid flow. However, it is still of limited use in the optimization of common thermal systems. Search methods