Analysis On Characteristics Of Liquid Sloshing In Automobile Fuel Tank Under Multiple Operating Conditions

The fuel tank is an important safety parts and functional parts of the car,and one of the important functions of the fuel tank is to indicate the fuel quantity accurately.When the vehicle driving conditions change abruptly,the fuel is shaking violently in the tank,which not only affects the indication accuracy of the oil sensor in the tank,but also affects the stability of the structure,while generating significant liquid sloshing noise.In this thesis,a light truck fuel tank was regarded as the research object.Based on the theory of liquid sloshing and VOF method,this thesis analyzes the liquid sloshing analysis model of automobile fuel tank from three aspects: automobile braking condition,lateral working condition and filling ratio condition.Based on the analysis results and combined with the current structure of the tank anti-sway device,the tank structure is optimized from three aspects: thickness,height and aperture to achieve good NVH performance.The main research work in this thesis includes:(1)Establishment of Numerical Model for Fuel Shaking.Based on the liquid sloshing theory and free surface tracking method(Volume of Fluid),a classical numerical model of cylindrical liquid sloshing is established.The accuracy of the numerical model is verified by comparing with the experimental analysis,The maximum error is about 4%.(2)Dynamic analysis of fuel shaking under multiple operating conditions.Based on the finite volume method,the numerical simulation model of fuel sloshing was established to study the different braking acceleration,different lateral acceleration and the shaking characteristics of fuel under different liquid filling ratio.By observing the impact of the flow field on the structure,it is found that the numerical value increases with the increase of the braking excitation and the lateral excitation.When the fuel tank ratio is 0.7 to 0.9,the structure is affected by the maximum impact.(3)Prediction of fuel sloshing radiation noise based on transient flow field.Based on acoustic finite element method and infinite element method,the acoustic analysis model of automobile fuel tank was established to predict the sound pressure level and spectrum distribution of fuel radiation noise.Liquid shaking noise is not determined by a single frequency,but with a certain broadband characteristics.The noise distribution has a certain directivity characteristics,and the sound pressure level is not absolutely proportional to the brake excitation and liquid ratio is proportional to the relationship between the brake excitation.And the liquid-filled ratio is reduced,but it is possible to produce more noise.(4)The optimal design of the anti-swing structure of fuel tank.Based on the above model,the influence of three design factors on the anti-sway effect is studied,which includes the height,thickness and aperture of the anti-sway.And compared the fuel radiation noise changes with and without anti-swing structure to determine the best structure of the anti-rock plate to achieve better NVH performance.It was found that the height ratio had a greater effect than the thickness and aperture on the effect of noise reduction and noise reduction.