A Study On The Intake And Exhaust Characteristics And Structural Performance Of Air Valves

Long distance water conveyance projects are one of the important ways to appropriately optimize the allocation of regional water resources.For pressurized water conveyance pipeline system,either the close of valve or the stop of pump by accident can result in the transient of pipeline pressure and the formation of water hammer.The positive pressure of water hammer may easily lead to pipeline rupture and water supply interruption;the negative pressure of water hammer will make the pipeline collapse and the water supply flow reduce.As important equipment of water hammer protection,Air valves are widely used in water pipes,because of their unique advantages.In engineering applications,the selection and layout of air valves usually depend on experience,but because the production standards of manufactures are various,even the protection effect on water hammer of the same type of air valves is rather different.Therefore,it is necessary to study the effects of intake and exhaust characteristics of air valves on the protection of water hammer from the perspective of the structure characteristics of air valves,which can further guide the optimization of air valve design.In this dissertation,the air valve water hammer protection characteristics as the research object,through the Fluent software on the three-dimensional structure of the air valve,according to the "big hole exhaust","small hole exhaust" and "inhale" Get intake and exhaust flow rate characteristics of the air valve,flow coefficient and water hammer buffer transition pressure;Hammer software installation of the air valve on a water pipeline to stop pumping water hammer analysis to verify the air valve on the water hammer protection effect.The main findings of this dissertation are as follows:(1)The original air valve "big hole exhaust" flow coefficient is 0.474;"small hole exhaust"flow coefficient is 0.176;"inhale" flow coefficient is 0.297;air valve waterproof hammer buffer transition pressure is 1500Pa.Comparative analysis of exhaust flow characteristics curve,the air valve has a certain buffer exhaust performance.(2)The water hammer installed on the original air valve to stop the water hammer analysis found that the original air valve on the pipeline water hammer positive pressure has a good protective effect,but inferior protection of water hammer negative pressure;comparative analysis of different aperture size air valve water hammer protection and found that the original air valve exhaust aperture is too large,resulting in water hammer protection can not be reached within the safe range.(3)By improving the structure of the original air valve,the water hammer buffer piece is arranged on the upper end of the valve body.When the ratio of the flow area of the buffer piece to the area of the outlet hole of the air valve is 0.025,the water hammer protection effect of the air valve reaches the safety range within.