一、引言 目前城市燃气输配系统设计方向向两级、多级和混合式压力级制发展。通常,把工业企业、动力锅炉和低压网的调压站等大型用户直接联在高(中)压管网上;而居民、公共设施和小型燃气锅炉等联向低压管网。根据管网容量可将管网设计成枝状管网,环状管网和干管为环状,次级管路为枝状的混合式管网。 随着管网向大容量、长距离和多级压力制综合管网发展,其结构日趋复杂,一旦发 I. INTRODUCTION At present, the design direction of urban gas transmission and distribution systems has been developed to two-stage, multi-stage, and hybrid pressure class systems. Usually, large-scale users such as industrial enterprises, power boilers and low pressure network pressure regulating stations are directly connected to the high (middle) pressure pipe network; residents, public facilities and small gas boilers are connected to the low pressure pipe network. According to the capacity of the pipe network, the pipe network can be designed as a branch pipe network, the ring pipe network and the trunk pipe are ring-shaped, and the secondary pipe is a branch-like hybrid pipe network. With the development of pipeline networks to large-capacity, long-distance, and multi-stage pressure-based integrated pipeline networks, their structure has become increasingly complex and once