Gas And Steam Combined Cycle Unit Modeling And Research On Performance Of Off-design Condition

Due to the advantages of low pollution,quick start,saving investment,good load performance,Gas turbine are receiving more and more attention.In addition,Gas-steam combined cycle can realize cascade utilization of energy,and improve energy utilization efficiency and thermal efficiency of the unit.It has been widely developed and applied in electric power industry in recent years.Companies such as GE,Siemens,Mitsubishi,long-term devote themselves to research of gas turbine work,apply the aviation generator technology to the industrial gas turbine,constantly optimize the performance of gas turbine.Most of the gas-steam combined cycle units of China are imported from abroad.The manufacturer provides the design condition of rated parameters.But in actual operation process,because of the change of environment temperature,atmospheric pressure and humidity,fuel calorific value and unit load,combined cycle unit often run under off-design condition.For a comprehensive understanding of combined cycle unit performance,therefore,we should be at the same time grasp the unit features under the rated condition and off-design condition.This article selects a running 9F combined cycle unit in the domestic power plant as the research object.The research is focused on using heat engine cycle simulation software EBSILON to build a gas-steam combined cycle unit model,analyze and study the change of combined cycle unit output and thermal efficiency under the off-design condition.The paper analyzes the characteristics of different types of combined cycle unit.Gas turbine,heat recovery boiler and steam turbine are three main parts of the gas-steam combined cycle units.After the analysis of their characteristics,the paper studies the affecting factors of the combined cycle unit performance under the off-design condition,including the changes of atmospheric conditions,unit load,unit fuel and exhaust pressure loss,etc.Based on the mass flow,compression ratio and temperature ratio and other main thermodynamic parameters of gas turbine,derive respectively the specific output and thermal efficiency expression of the gas turbine in the ideal simple and practical simple cycle,and study the influence of pressure ratio and temperature ratio on the gas turbine performance.In the case of an appropriate hypothesis,derive the environment temperature,atmospheric pressure and humidity on the relational expression of thermal efficiency and power output of the combined cycle unit,and use the MATLAB simulation to research the influence of environment parameters on the performance of combined cycle unit.Using the heat engine cycle simulation software EBSILON to build a gas turbine model and make variable load simulation.Compare the results with power plant operation data,and verify the validity of the model.Build the gas-steam combined cycle unit model.The parameters setting refer to design parameters of the Beijing combined cycle power plant 9F unit.Change environment parameters at the entrance of compressor and make simulation,obtain the influence diagram of environmental parameters on the output and thermal efficiency,and compare with previous theoretical derivation,the MATLAB simulation results,and the manufacturer correction curve to verify the correctness of the model.