输油管道运行优化目标函数的讨论

Investigation on Object Function's Behavior of Oil Transportation Pipe-line

目标函数的凸性或单峰性是应用非线性规划方法获得问题全局最优解的必要条件。应用数值方法获得多条输油管道算例的运行优化目标函数曲线 ,并研究其是否满足上述条件。结果显示 ,总体搜索范围内目标函数呈多峰性及局部锯齿形 ,表明存在多个局部最优解。据此可推断 ,输油管道运行优化目标函数在总体搜索范围内一般不满足非线性规划方法获全局最优解的必要条件 ,按总体范围搜索极有可能仅获得局部最优解。对已提出的多种处理方法进行综合分析 ,其中任何一种处理方法的实质都是寻找总体搜索范围内全局最优解所处且满足上述条件的较小寻优区间 ,以便获得真正的最佳运行方案。

It is the condition necessary to obtain global optimal solution that the object function satisfies convex or at least unimodal curve property when nonlinear programming method is utilized to implement optimiza-tion analysis. Several curves of object function about oil transporting optimization for pipeline are obtained by use of numerical method. The discussion is made on their characteristic in given searching domain to in-vestigate whether they satisfy the condition above and which measures should be taken to avoid global optimal solution loss in analysis process if they were not satisfied. The results show that these curves all have the feature of multimodal distribution and generally do not satisfy above condition. This demonstrates that there is a great possibility that only local optimal solution would be obtained if available measure were not be taken when using nonlinear programming method to search optimal transportation scheme for oil pipe-line. Thus several measures are outlined in this paper. The inherence of any measure among them is to find smaller zone before optimizing process, in which not only it is the global optimal solution situated but also the above condition could be satisfied.