Study On Pressure Characteristics Of Experiment Vessel For Ultra-high Pressure Detonation Of Shale Gas

In this thesis,the strength of the ultra-high pressure ignition cavity used in the insitu ignition and detonation cracking experimental system of shale gas is studied in order to ensure the safety and reliability of the cavity.A detonation chamber is an detonation vessel.Detonation vessel is a kind of equipment commonly used in industrial production.Its safety performance directly affects the safety of production environment and personnel.Reasonable design of the ultra-high pressure ignition cavity is the key to ensure the safety of the experimental system.This thesis focuses on the structural design,material selection and force analysis of methane-air premixed gas ultra-high pressure ignition cavity.Based on the analysis and comparison of the advantages and disadvantages of different design methods,the dynamic response characteristics of the combustion cavity designed by multi-layer structure were studied when the methane-air premixed gas was detonated at ultra-high pressure.The impact load and thermal stress coupling method under the condition of multiple physical fields in the combustion cavity were analyzed in detail.Firstly,the overall scheme design of the ultra-high pressure ignition and detonation system of shale gas is completed,including the data acquisition system and the gas distribution system.The structure design of the combustion and detonation chamber is carried out according to the existing design theory of the combustion and detonation chamber,and the interference of the interlayer on the wall of the double-layer structure is calculated,the cavity parts are designed,and the acquisition module and sensor are selected.Then,LS-DYNA explosion mechanics software was used to simulate the ultrahigh pressure ignition of methane-air premixed gas in the closed and one end opening cavity.The distribution characteristics of impact load on the wall and its variation with time were obtained.It was found that the circumferential stress of the selected model was tensile stress at each point,while the radial stress was compressive stress.The corresponding stress load curve is linear rising exponential attenuation,and the load oscillates with the movement of air flow in the container after the detonation process.FLUENT software was used to numerically simulate the flow field and temperature field of methane-air premixed gas in the ultra-high pressure ignition and detonation chamber pipeline with closed,open end and exploder,and thermal stress analysis was carried out by combining the temperature field and velocity field data obtained with LS-DYNA software.Finally,the impact stress,prestress and thermal stress are coupled with the simulated data.It is found that the inner wall and the interface of the inner and outer layers are the stress concentration area of the thermal stress.By analyzing the strain condition of cylinder block,it is found that closed chamber is not suitable for methaneair ultra-high pressure ignition and detonation.By analyzing the stress distribution of cylinder,it is found that the thermal stress of one end opening is concentrated in the inner side of the cylinder,and the thermal stress of the deflating type detonation chamber is concentrated in the inner side and the outlet.In addition,it is found that the coupling stress of thermal-impact-prestress of the open cavity and the cavity with the detonator is mainly affected by the impact load,while the influence of thermal stress on the cylinder body of the open cavity is greater than that of the cavity with the detonator.At the same time,there is no plastic strain in both of them,so they can be used as the methane-air ultra-high pressure ignition cavity.