Performance Evaluation And Diagnosis Of Gas-steam Combined Cycle Power Plants Based On Thermoeconomic Theory

Gas turbine and combined cycle are widely applied in power generation with the advantages of high efficiency,strong peak load regulation performance,less pollution and so on.Thermoeconomics,a combination of thermodynamics and economics,is applied in cost accounting,performance optimization and fault diagnosis.Based on the structure theory of thermoeconomics,the performance evaluation and diagnosis of 9FA gas-steam combined cycle power plant are carried out.First,the gas-steam combined cycle power plant is modeled.The performance characteristics of combined cycle in different environmental conditions and load demands are simulated.Compared with the performance data obtained from power plant,the relative errors of simulation results are less than 1%.Combined with the operating data of power plant,the simulation provides fundamental data for thermodynamic and thermoeconomic analyses.Second,based on the simulation and operating data of power plant,the effects of atmospheric condition on performance of combined cycle are conducted.The inlet air cooling technology is an effective method to prevent the tendency that the power out and efficiency of combined cycle decrease as ambient temperature rises.Considering super-cooling effect and extra water vapor condenses on surface of heat exchanger,the theoretical and practical cooling load is compared.A new concept,critical relative humidity,is proposed to evaluate the feasibility of inlet air cooling system according to local climatic condition.Then,the basic concepts of thermoeconomics are introduced and the calculation model of unit thermoeconomic cost is summarized.Based on physical structure and productive structure of combined cycle,the fuel and product of every component are investigated.The unit exergy consumption and unit thermoeconomic cost are calculated.The effects of natural gas price and initial investment cost on thermoeconomic cost are discussed.Finally,based on thermoeconomic diagnosis principle,the concept of malfunction and dysfunction are defined.This method is applied to diagnose the malfunction in a 9FA gas-steam combined cycle power plant.The malfunction and dysfunction of each component are compared and the fuel impact is analyzed.