Study On Thermal Coupling Of Straw Powder Compression Molding

The development and utilization of straw biomass briquette can not only avoid the environmental pollution caused by the on-site burning of crops,but also play an important role in industrial heating and civil heating.Firstly,the viscoelastic-plastic constitutive equation of particle system is established by introducing contact mechanics and thermal models of particle material.According to the basic knowledge of particle mechanics,the contact and heat transfer relationships between particles and between particles and between particles and molds were analyzed,the viscoplastic model of particle contact phase was constructed,and the contact forces between straw particles and molds in the heat transfer process were calculated iteratively using Verlet method.Secondly,the mechanical and thermal models of particles were written by C++ language,and the API interface between EDEM particles and contact model was developed for the second time.In order to verify the influence law between heating temperature and molding pressure,a single plunger biomass molding test bed was built,and the established discrete element particle model was verified by means of molding sleeve heating.Orthogonal experiment was used to analyze the influence of various factors on the hot pressing process of straw.The multiple regression equation was established,and the multiple regression model and equation of the average temperature,the maximum temperature,the central point temperature and the factors of the cross section of straw molding block were obtained through effective simplification.The primary and secondary influencing factors of the block density are the water content of the raw material,the frequency of the motor and the heating temperature.The primary and secondary influencing factors of maximum temperature are heating temperature,motor frequency and water content of raw material.Finally,the compressed molding block is regarded as a continuous medium,and ANSYS is used to carry out the finite element simulation in the extrusion mold stage to analyze the change law of temperature field and the change trend of stress and strain.According to the result of experiment and simulation analysis was made on the problems of straw powder compression molding process three stages: the plastic stage,stage of viscoelastic and viscoplastic fluid phase,established the corresponding mathematical model of three phase three mechanics and the whole process of temperature field model,and according to the three model,mechanical model and a temperature field with time as the intermediate variable,so as to construct three group of thermodynamic coupling model,comparing with the previous data.Through residual analysis,the accuracy of the simulation model is determined,and the stress-strain relationship and variation trend can be predicted at different heating temperatures.