Influence Of Liquid Sloshing On Vibration Characteristics Of Vehicle-mounted LNG Cylinders And Solutions

Liquefied natural gas vehicles(LNGV)have received extensive attention from the relevant automotive industry for their clean,environmentally friendly,long cruising range and other advantages.As the main component of LNGV,on-board LNG cylinders are equipped with LNG under sudden braking,sharp turns and road pits.The gas cylinder will vibrate greatly due to its own weight and the violent sloshing of the liquid inside,which will cause the cylinder to be damaged.The failure of the gas cylinder caused by flow-induced vibration is one of the common failure modes.Therefore,studying the vibration characteristics of vehicle-mounted LNG cylinders is of great significance to improve the vibration resistance of the cylinders.This paper explores the anti-vibration performance of vehicle-mounted LNG cylinders under liquid sloshing combined with numerical simulation and vibration experiments,and optimizes the design of the anti-wave device inside the cylinder.The specific research content and conclusions are as follows:(1)A fluid-solid coupling model of a 1000 L large-volume vehicle-mounted LNG cylinder was established,and the theoretical method and the vibration experimental test were used for comparison and verification.The results show that the model established in this paper can be used for statics,random vibration,and liquid sloshing dynamic analysis;among them,the statics calculation error does not exceed 2%,and the dynamic analysis error does not exceed 7%.(2)By analyzing the modalities of vehicle-mounted LNG cylinders,study the influence of different filling rates and different cylinder lengths on the resonance frequency of LNG cylinders.The results show that when the length of the cylinder remains unchanged,the resonance frequency of the gas cylinder gradually decreases with the increase of the filling volume.When the filling rate is 90%,the first-order resonance frequency of the gas cylinder has been reduced to below 40 Hz allowed by the national standard.It is easy to cause resonance;when the filling rate remains unchanged at 90%,as the length of the cylinder increases,the resonance frequency of the cylinder also shows a decreasing trend.When the length of the cylinder is 0.8 times the original length,the resonance frequency of the cylinder Below 40 Hz,it does not meet the requirements of the national standard on the resonance frequency of vehicle gas cylinders.(3)By testing the vibration performance of the vehicle-mounted LNG cylinder,the amplitude-frequency response curve of the LNG cylinder under different filling quantities is obtained.Extracting the experimental results and analyzing the results: when the cylinder is empty,the three resonance points of the cylinder are in good agreement with the resonance frequency and mode shape of the modal analysis;as the filling volume increases,the resonance frequency of the cylinder gradually Decrease,when the cylinder in this article is fully loaded,its first-order resonance frequency is 39.84 Hz,which is already lower than the40 Hz allowed by the national standard,which is easy to cause resonance.(4)By simulating the mechanical response of the axial liquid structure inside the cylinder,the influence of different filling quantities on the structural strength of the LNG cylinder is analyzed.The results show that when liquid sloshing is considered,the equivalent stress value of the connection between the cylinder liner and the short supporting tube is greatly increased,up to 2.3 times,indicating that the liquid sloshing has a greater impact on the strength of the cylinder;when the cylinder is fully loaded(90 %),the axial liquid sloshing inside the cylinder is not violent.The average maximum pressure value of the inner wall of the front head is close to half the filling volume.It can be seen that the impact of liquid sloshing can be reduced when the filling volume is large;When the loading rate is 70%,the impact force caused by the axial liquid sloshing inside the cylinder is greater,and the average pressure at the front head is 4000 Pa higher than that at full load.(5)In view of the adverse effects of liquid sloshing,a new anti-sloshing structure is proposed.This result is also conducive to strengthening the stiffness of the gas cylinder and avoiding the problem of excessive deformation of the gas cylinder.By comparing with the fluid pressure curve without anti-wave plate,it is found that the new anti-sloshing device can reduce the sloshing of the liquid in the gas cylinder,and can effectively reduce the impact of the liquid on the wall.