Chengzhi Zheng

Subatmospheric pressure protection for large diameter long distance pipeline system: A case study

Typical surge analysis of long distance pipelines involve pump power failure and startup at lift stations discharging into force mains. Utilities have several options for protecting pipeline systems from the effects of transients and surges. But how to select an effective surge protection strategy to design the system to withstand the stresses of transients is still a great challenge, especially for a high-lift, multiple peaks long distance system. This paper describes unique considerations that should be addressed when performing hydraulic transient analysis and recommending surge protection for water supply systems. Hydropneumatic tanks, surge tanks, vacuum breaker valves, surge-anticipator valves (SAV), surge relief valve (SRV), or both of them combined, and air valves will be discussed. Recent project examples and the effect of these new devices on surge protection in China will be presented.

STUDY ON RESIDUAL CHLORINE CONTROL OF WATER DISTRIBUTION SYSTEMS WITH MULTIPLE WATER SOURCES

A best chlorine injection schedule for each source and booster station in a distribution system is studied and a multiple object optimal operation model of water distribution system(WDS) considering residual chlorine is also presented. The optimal scheduling of water distribution system is composed of two parts, the hydraulic and the water quality optimal control, and water quality optimal control is based on the hydraulic optimal control. As an important component of water quality optimal control, the residual chlorine control is selected as one of the objective functions of the optimal scheduling of water distribution system. A new multiple objects optimal operation model of WDSs is developed. The objective functions include minimum of residual chlorine and minimum costs of WDSs operation. The decision variables include the demand, pressure and residual chlorine at each water source, nodal demand, nodal pressure, and nodal residual chlorine. The hydraulic and the water quality model are solved by EPANET. The multiple objects optimal operation model of WDS is solved by the non-dominated sorting genetic algorithm (NSGA-II). Adaptive penalty functions are also applied in the process of model solved As a case study, the multiple objectives optimal operation model is applied in a large scale WDS. The WDS ’s total demand is about 1,320,000 m 3 /d, and is composed of 9 water plants, 32 water sources, and 468 wells. The result shows that the optimization of chlorine of each water source makes the distribution of nodal chlorine more reasonable and the concentration of nodal residual chlorine was reduced.

Research on water supply pipeline failure consequence assessment model

In order to evaluate the ability of the service network after taking off some valves in the event of one or more pipeline breakages, the paper has established the water supply pipeline failure consequence assessment model. The model was two hierarchical assessment model using an objective weighting method. It took the node demands decrease of affected pipelines, the node demands decrease and the pressure reduction of non-affected pipelines as three estimate indexes. All of parameters were treated as the properties of the node. The water supply pipeline failure consequences evaluation model based on water supply pipeline failure hydraulic model, which first redistributed node demands, and automatically adjusted the node demands under node pressure, and was calculated by genetic algorithm(GA). Through the simulation experiments in a small water distribution system, it showed that the model worked well. According to the assessment results with the model, the reasonableness of the valves arrangement and the role of some pipelines can be effectively analyzed, and the research proposed measures to reduce the consequences of pipeline failure.

Research on Urban Water Supply Pipeline Breakage Probability Model

In order to predict the breakage trends of each pipeline in the urban water supply networks, investigators collected a great deal of information about pipeline breakage, with the theoretical analysis of pipeline breakage factors and analysis of collected data, the urban water supply pipeline breakage probability model was constructed. And the research used the analytical hierarchy process (AHP) method to analyze the pipeline breakage factors; it took the pipeline internal status and pipeline external status as the two first level indicators, and material, diameter, pipe age, corrosion, operating conditions, seasons changing and construction quality as the seven second level indicators. Including pipelines length, eight variables were synthesized in one model. As expected, all the pipelines can be sorted according to the size of the breakage probability calculated by the model. It had reason to believe that the predictive value of pipeline breakage probability was more accurate than some other models, because such comprehensive factors were taken into it. At last, the model was applied to the data collection area — one city of East China, and the analog value of pipeline breakage probability was obtained, which provided one kind of decision support for the pipeline project, so it should achieve optimization of pipeline maintenance and transformation.

RESEARCH ON LEAKAGE CONTROL OF WATER DISTRIBUTION NETWORK BASED ON PRESSURE-DRIVEN DEMAND MODEL

In order to achieve the control of network leakage, and establish leakage control model, Embedding pressure-driven node flow hydraulic model into leakage control model was developed leakage control model based on pressure-driven node flow was formulated. Taking the total loss as the objective function, the optimal valve setting was solved by genetic algorithm. Reducing leakage can be achieved by reconfiguring valve operation to the biggest extent under the precondition of normal water supply.