Study On Exhausted Flow Field And Noise Of Underwater Thermal Power Propulsion

The propulsion device of thermal power is now widely used in various fields,such as various types of aircraft in the aerospace field,all kinds of underwater vehicles in the navigation field,and so on.The exhaust gas generated by the propulsion device is usually discharged into the surrounding environment,but it will lead to many adverse effects.In particular,when the exhaust gas of the underwater vehicle using this device is discharged into water,bubble tracks and emission noise are generated,thereby destroying the stealth of the vehicle.The exhaust gas underwater emission is a complex gas-liquid two-phase flow accompanied by a strong radiated noise’s process.It has been affected by many factors,such as the parameters of exhaust pipe structure,navigation,etc.,and its mechanism of action is still not verified.Many relevant research references were investigated and the methods of numerical simulation were used in this paper.Numerical calculations were performed on the exhaust underwater emission’s process,which direction is opposite to the direction of gravity,by using the Mixture multi-phase model and k-ε turbulence model.The results obtained from the simulation were compared with the results in the literature and they were found to have good agreement.On the basis of the simulation,the underwater discharge process of the exhaust gas under the influence of speed,depth,the exhaust pipe diameter and shape was simulated.Then,the gas distribution,pressure,speed,temperature of the flow field were analyzed,and thus their flow field’s change rules were also obtained.At the same time,the FW-H noise model was used to forecast the underwater emission noise,and the rules of the noise was also obtained.The calculation results show that under a certain flow rate,with the increase of the diameter of the exhaust pipe,the flow state of the exhaust gas underwater emission was transformed from the jet flow state into the bubble flow state,the flow field pulsation is also weakened,and the emission noise is enhanced in the same flow state.Under the same area of cross-section of the exhaust pipe,when the long axis of the elliptical exhaust pipe is perpendicular to the direction of gravity,the exhaust gas emission flow parameters are very different from the circular exhaust pipe,and the emission noise is also weaker than circle exhaust pipe.The exhaust flow fields of the vehicles under the different depth are basically similar,but the emission noise in deep water is stronger than that in shallow water.When the vehicle moves linearly at a certain fixed speed,its exhaust gas formed a narrow gas flow channel under the water,and its emission noise is stronger at the low frequency than that at the hydrostatic conditions.Therefore,the research results of this paper have important engineering guidance significance for the methods of obtaining emission noise suppression.