The Study Of The Supercritical And Subcritical CO₂Cleaning Technology For Remanufacturing

Remanufacturing is one of the key processes to realize sustainable manufacturing, which is also an important means to promote the development of circular economy in China. Remanufacturing cleaning is an important procedure of remanufacturing processes, thesis aims at developing demonstration and research of a new kind of green remanufacturing cleaning technology towards the environmental protection from the perspective of design of remanufacturing engineering technology. At present, the supercritical and subcritical carbon dioxide fluids have become the first choice of new environmentally friendly cleaning agent, which have bigger densities, stronger permeability and mass transfer ability, lower viscosity and surface tension, and also can be recycled. Thesis carries out the related theory analysis and experimental research of this cleaning technology on the background of remanufacturing cleaning, and also explores the feasibility study of ultrasonic coupling to strengthen the cleaning.Thesis introduces the basic concepts and characteristics of supercritical and subcritical" carbon dioxide, and explains the dissociation of dirt from the viewpoints of dissolving and swelling combining with the physicochemical characteristics of carbon dioxide. It has carried out the qualitative analysis of factors which have influence on the cleaning effect by building the cleaning mechanism theory system whose main parts are the theories of solubility parameter, second law of thermodynamics, phase equilibrium thermodynamics, convective mass transfer, swelling, infiltration and cosolvents.Set up a dynamic cleaning experiment platform, take the engine lubricating oil and grease for machinery equipment as the objects of experiment in order to carry out basic experiment research and the remanufacturing cleaning process parameters of the supercritical and subcritical CO2fluids have been planned and optimized under the experimental conditions. Meanwhile the optimal cleaning process parameters have been applied to clean the real parts having typical adhesion dirt layer, curing of the layer makes it become easier to grind and remove.In order to shorten the cleaning time and improve the cleaning effect, thesis carries out the feasibility study of enhancement method of the ultrasonic wave coupling and the theoretical analysis of the thermal effect and the effects of vibration and cavitation which are triggered by the ultrasound, and meanwhile analyses the influence of system pressure and temperature on the cavitation threshold of subcritical carbon dioxide fluid. A model is proposed that can simulate the dynamics of cavitation bubbles in the subcritical carbon dioxide fluid based on the Rayleigh-Plesset equation, and then the fourth-order Runge-Kutta algorithm is used to calculate the reduced order model. Thesis analyzes the cavitation effects produced in the ultrasound coupling subcritical carbon dioxide fluid under different process conditions, so as to estimate the ideal process parameters, and get the optimal process parameters by setting the boundary conditions and objective function, which has a certain reference value for engineering application.