Thermodynamic Research And Optimization Of Rankine Cycle Based On Supercritical Regeneration

The Rankine cycle is the basis of many complex power cycles and an important part of the thermodynamic cycle theory.The theoretical research and optimization of the Rankine cycle can promote the understanding of the cycle,and then improve the energy utilization rate.It plays an important role in the sustainable development of our country and the improvement of the security and economy of power supply.This paper analyzes the Rankine cycle from the perspective of heat recovery,explores the heat recovery limit of the Rankine cycle,and analyzes the Rankine cycle based on the first and the second law of thermodynamics.Firstly,according to the imperfection of the current regeneration method,based on the subcritical regeneration,the supercritical regeneration form of the Rankine cycle is proposed,and the feasibility of the supercritical area recuperation is proved by theoretical derivation method.Based on the Rankine cycle of one-stage reheating with eight-stage regeneration,the thermodynamic characteristics of the new cycle were explored,and the effect of different cycle parameters on the thermal efficiency of the cycle was studied.In this case,the cycle thermal efficiency can be improved by up to 1.25%after adding the supercritical regenerative process.At the same time,with the analysis method in this paper,the circulating feedwater temperature and feedwater flow rate will also be greatly improved.Secondly,under the framework of Carnot cycle,this paper compares the water Rankine cycle and the CO₂ Brayton cycle with the average temperature at which heat is added and rejected as the index.The supercritical regenerative process was used in the reheating process,and a supercritical regenerative reheat cycle was proposed.The analysis results show that the average temperature at which heat is added of the supercritical regenerative reheat cycle can reach or even exceed that of the S-CO₂ cycle,and the average temperature at which heat is rejected is lower than that of the S-CO₂ cycle.Under different main steam parameters,the thermal efficiency of supercritical regenerative reheat cycle can reach higher than that of S-CO₂ cycle.From this point of view,the Rankine cycle is more advantageous than the S-CO₂ cycle.Finally,this paper compares and analyzes different regenerative technologies for coal-fired units,and discusses the applicability of supercritical regenerative in the field of coal-fired power generation.The exergy analysis of the secondary reheat units with different regenerative methods is carried out.The analysis results show that the application of the BEST small machine can effectively reduce the exergy loss of the regenerative process,and the application of the supercritical regenerative process can greatly reduce the exergy loss of the boiler.After the two methods are coupled,the efficiency can be further improved.