Research On Water Hammer Of Multi-valve Prote Ction Pressure Water Supply System

Long-distance pressurized pump water supply system will cause damage to valves and other components when occur water hammer.This paper proposes a multi-valve water hammer protection measure.The working principle is that the buck wave generated by the pump end and the boost wave before the intermediate valve cancel each other,and the step-down wave after the intermediate valve and the boost wave before the end valve cancel each other out,thereby suppress water hammer damage.Combined with the engineering example,the objective function and constraint conditions of the multi-valve water hammer protection measures are established by the golden section method.Combined with the four-stage pumping station of an industrial park,the MATLAB language is used to calculate the pump-stop water hammer.At the same time,the closing procedure of the end valve for the pressurized gravity flow project was optimized by the golden section method,and optimized with examples.The main achievements are:(1)A multi-valve water hammer protection measure is proposed,which consists of a two-stage closing butterfly valve,an intermediate valve(inspection valve)and an end valve(inspection valve),which are mainly used for water hammer protectionin a pressurized water delivery system.The boundary conditions for multi-valve water hammer protection measures under different working conditions were established.The objective function and constraint conditions of the multi-valve water hammer protection measures are established.The minimum area enclosed by the maximum pressure head envelope and the pipe center line is the objective function,and the multi-valve water hammer protection measures are established.The mathematical optimization model gives the solution steps for optimizing the optimal closing procedure of the valve by the golden section method.This protective measure has been approved for the National Utility Model Patent Certificate.(2)A new method for optimizing the end valve closing procedure of pressurized gravity the end valve is established by the characteristic line method.Taking the minimum pressure head of the pipeline as the minimum objective function.In the process,the pipeline does not have negative pressure and the end valve closing procedure can behave as a constraint condition,and the solution method of optimizing the end valve closing valve procedure by the golden section method is given.The water hammer calculation results show that the end valve of the long-distance pressure gravity flow water transfer project has the optimal valve closing time and opening degree.(3)For the four-stage pressurized pumping station of an industrial park water supply project,five water hammer protection schemes are proposed.scheme A:two-stage closing butterfly valve+18 air valves;scheme B:two-stage closing butterfly valve+20 air valves scheme C:two-stage closing butterfly valve+18 air valve+end valve;scheme D two-stage closing butterfly valve+18 air valve+intermediate valve;scheme E:two-stage closing butterfly valve+18 air valve+end valve+intermediate valve.Using MATLAB language programming and numerical simulation,the water hammer protection of the project was calculated and analyzed.The results show that scheme A and scheme D do not satisfy the constraint conditions,schemes B,C and E satisfy the constraint conditions,and the objective function values M of schemes B,C and E are 1.90,1.78 and 1.58 respectively,and the objective function value M of scheme E is minimum.Comparing schemes B and E,it is found that the total number of valves used in schemes B and E is the same,but the protection effect of scheme E is obviously better than scheme B,so the protection effect of multi-valve water hammer protection measures is significant;the main factors affecting multi-valve water hammer protection measures are the valve closing procedure of the two-stage closing butterfly valve,the intermediate valve and the end valve,and the installation position of the intermediate valve;the multi-valve water hammer protection measure combined with the air valve protection water hammer effect is significantly better than the air valve.(4)By comparing and selecting the water hammer protection scheme that meets the constraint conditions,the water hammer protection scheme finally selected in this project is scheme E,that is 18 air valves combined with multi-valve water hammer protection measures.The relevant parameters of scheme E are:multi-valve water hammer protection measures of the diameter about the intermediate valve and the end valve is 0.59m,the resistance parameter of the intermediate valve bypass pipe is 461,and the optimal installation position of the intermediate valve is the pile number 13225.516m(section 260),The resistance parameters Snl and Sn2 of the end valve bypass pipe are 299 and 294 respectively.The closing procedure of the two-stage closing butterfly valve is as follows:the closing time is 18s,the opening after the closing is 40°,the total closing time is 299s;the closing procedure of the intermediate valve is as follows:the closing time is 8s,and the opening after the closing is 65°,the total closing time is 13s;the closing procedure of the end valve is as follows:the closing time is 8s,the opening after the closing is 24°,the total closing time is 16s,and the total closing time is over,the degree is 4°.