Dynamic Analysis Of A Closed Brayton Cycle Using Supercritical Carbon Dioxide

Supercritical carbon dioxide?S-CO2?Brayton cycle power generation is developing rapidly in the international.S-CO2 Brayton cycle has a great advantage in the cycle efficiency and equipment size compared with traditional thermal power generation.Most of the current researches focus on the steady-state thermal calculation and system layout design of the circulatory system.There are few researches on the dynamic simulation of the circulatory system.Establishing the system dynamic simulation model has practical engineering significance for the operation,commissioning and maintenance of the actual power plant.Therefore,the establishment of a dynamic simulation model of the circulatory system is a necessary way to deepen the study.Aspen Plus software was used to establish the S-CO2 Brayton cycle system model with different circulation arrangements,and the performance of the circulation system with different layouts was compared and analyzed.Taking S-CO₂ shunt and recombination Brayton cycle system as the research object,the effects of turbine inlet temperature and pressure,outlet temperature of pre-cooler and compressor shunt coefficient on cycle thermal efficiency were studied.The physical property of CO2 near the critical point was analyzed by REFPROP physical calculation method.According to the basic theories of thermodynamics,fluid mechanics and heat transfer the mathematical models of each equipment are established.The FORTRAN language algorithm is used for the second modeling,and the algorithm is imported into the algorithm library of Panysimu simulation system.Using the existing algorithms of the simulation system and the new algorithm to build the S-CO2shunt and recombination Brayton cycle model.The experimental data were used to verify the accuracy of the model.The model was perturbed to study the influence of heater heating,valve opening and precooler cooling capacity on the system,and the dynamic characteristics of the system were analyzed.The simulation results are as follows:Under the condition of higher parameters,the thermal efficiency of the simple Brayton cycle is much lower than that of the recombination Brayton cycle and the shunt and recombination Brayton cycle.The influence of the compressor outlet pressure and the turbine inlet temperature on the recombination Brayton cycle efficiency is significant.Machine shunt coefficient optimum value between 0.5-0.7;The static results of the model built by using the Panysimu simulation platform are in suitable agreement with the experimental values and meet the simulation requirements.The model can be used to study the dynamic characteristics of the S-CO2 Brayton cycle system;The established model can be used to analyze the overall dynamic characteristics of the operation,and can calculate the thermodynamic parameters of any module;The results of dynamic perturbation experiment show that the amount of heater heating has a significant impact on the system.The small opening of the valve helps to improve the circulation efficiency,and the cooling capacity of the precooler has less effect on the circulation efficiency.