Study On Cooling Characteristics Of An Exhaust Cooling Silencer

Marine engine is generally characterized by large power and high working load,and the exhaust temperature is relatively high.A great amount of exhaust gas with high temperature produces obviously infrared radiation,which reduces the stealth characteristics of the ship.Therefore,the exhaust cooling silencer is generally used to cool the engine exhaust system.In this paper,a CFD numerical simulation method of exhaust cooling silencer cooling technology is established by ANSYS Fluent;the cooling effect of wall-type cooling is analyzed;the influencing factors of spray cooling technology based on pressure swirl nozzle are analyzed;and the cooling performance of exhaust cooling silencer is studied.In this paper,a droplet crushing model is established to study the secondary crushing process of droplet under high-speed airflow,and explore the rule of the secondary crushing of droplet.Changing the initial state of the droplet,the droplet complete evaporation time and droplet vaporization distance are considered as the indexes to measure the evaporation effect of the droplet,and explore the factors affecting the evaporation of the droplet.The results show that increasing the initial relative velocity between gas and liquid and decreasing the droplet diameter have positive effects on the droplet crushing and evaporation.In this paper,a 3D model of the pressure swirl nozzle is established to analyze its internal and external flow field.And the working mechanism of the pressure swirl nozzle is studied.The results show that flow field in the pressure swirl nozzle has certain partial velocity in axial,tangential and radial direction,which is suitable for irregular external flow field.Considering the droplet diameter as the index of atomization effect to study on the influence of nozzle parameters such as nozzle pressure,nozzle aperture and jet half angle on atomization effect.Based on a specific exhaust cooling silencer with wall-type cooling method,the effect of non-fin cooling effect is studied.For spray cooling technology,the optimal distribution of spray cooling nozzle is determined,and the influences of nozzle aperture,spray flow rate and environmental pressure on spray cooling effect are studied.