考虑多消防工况的旅游古城镇供水管网优化设计

Optimal Design of Water Distribution System in Ancient Tourism Town Considering Multiple Fire-fighting Conditions

针对旅游古城镇市政管网消防供水能力不足,而传统方法存在消防设计流量取值偏小、消防工况选取不合理等问题,提出考虑多消防工况供水管网优化设计方法。在旅游古城镇不同片区选取典型建筑物,采用ISO法计算其消防需水量并构建消防工况,将不同工况下最小要求水压作为约束条件,以管网中所有管道管径作为决策变量,构建以管网造价为目标函数的优化问题,采用差分进化算法求解满足不同工况约束且经济上最优的设计方案。将所提出的方法用于丽江大研古镇供水管网优化设计,结果表明,优化后的管网方案较传统方案的整体消防供水能力提升约6 L/s,而管网造价较传统方案减少约8%,且优化后典型建筑物消防供水能力达到了设计要求,这表明所提出的方法可行。通过分析管网布局及节点水压变化发现,对于地形高差较大、火灾风险较高的旅游古城镇供水管网设计,主管应向消防用水量大、地势高的控制点敷设,这样有利于提高管网整体消防供水能力并降低管网造价。

Municipal water distribution systems(WDSs) in ancient tourism towns usually have insufficient fire-fighting capacity, and traditional design method has the problems of relatively small value of fire-fighting design flow rate and unreasonable selection of fire-fighting conditions. A method for optimal design of WDS considering multiple fire-fighting conditions was thus proposed. The proposed method first selected typical buildings in different areas of ancient tourism towns and calculated their fire water demand by ISO method to build fire-fighting conditions, and then took the minimum required water pressure under different conditions as the constraint and the pipe diameter as the decision variable to formulate the optimization problem with network cost as the objective function. Differential evolution algorithm was applied to solve the optimization problem which satisfied the constraints of different design conditions and minimized the network cost. The proposed method was applied to the optimal design of WDS in Dayan ancient town, Lijiang. Overall fire-fighting capacity of the optimized scheme was about 6 L/s higher than that of the traditional scheme, and the network cost was about 8% lower than that of the traditional scheme. Besides, the fire-fighting capacity of the WDS for typical buildings met the design requirements after optimization, indicating that the proposed method was feasible. The WDS layout and nodal pressure changes were analyzed. For design of WDS in ancient tourism towns with large elevation variation and high fire risk, the main pipe should be laid to the control points with large fire water demand and high elevation, which was conducive to improving the overall fire-fighting capacity of the WDS and reducing the network cost.