Analysis Of The Causes Of The Fracture Of The Screw Connection Of The Gas Turbine Generator

Electricity plays an irreplaceable role in industrial production and daily life.At present,thermal power generation is still the main form of power generation in China.A gas factory found that its 30 MW gas turbine generator pole palm shoe screw fracture occurred.Screws are important components that connect these main components,functioning as joints,positioning and sealing,and they are also the most used.How to explore the relationship between the pre-tightening force of the high-strength screw and the external load,and how to improve the screw joint strength of the pole-tip shoe and ensure the first problem to be solved when the gas turbine generator is safely operated.Therefore,it is necessary to study the stress fatigue strength characteristics of the screw connection.To this end,this paper uses the combination of theoretical calculation algorithm,numerical simulation method,strength theory and fracture mechanics theory to determine the screw joint stress,fatigue strength and material properties of the megawatt gas turbine generator pole palm boots.Research,the main innovations and research work of the thesis are as follows:(1)Analysis of the material of the screw,its alloying element content,yield strength,elongation,Vickers hardness were tested and found that the screw material was alloy steel,the screw strength grade was 12.9,and it was found by the alloying element content.Its alloy steel grade is 40 CrNiMo,and the yield strength,tensile strength and elongation of the screw specimens all meet the requirements.Its Vickers hardness is within the specified range.(2)The traditional engineering algorithm is used to simplify the screw of the gas turbine generator pole pole shoe.Using the basic parameters of the screw and the rotor operating parameters of the generator,the reasonable value range of the screw preload is calculated.The calculation of the disassembly torque of the generator pole pole shoe screw shows that the screw may loosen due to the small pre-tightening force,causing the screw head to be exposed and causing the screw to be cut.Through the relationship between the pre-tightening force of the screw and the displacement and pre-tightening force and the life,the mechanism of the influence of the pre-tightening moment and other factors on thestrength and fatigue life of the high-strength screw is deeply understood.(3)Establish a finite element contact model for the rotor of the gas turbine generator.The stress analysis and fatigue test of high-strength screws were carried out under different pre-tightening conditions by ABAQUS and ANSYS nCode,and the distribution of stress,damage mechanism and screw life of the pole-top pole screw connection was obtained.A comparative analysis yields the range of values for the best preload.