Gas - Steam Combined Cycle Unit Case Modeling, And Its Characteristics Analysis

The advantage of gas-steam combined cycle is the cascade utilization of chemical energy in the fuel.Gas-steam combined cycle has been developed rapidly and applied more and more extensively because it has preferable energy conservation and environmental protection benefit and investment benefit.Most of the gas-steam combined cycle units used in China are imported at present.The unit parameters provided by the manufacturer are the operation parameters under the design condition,but the gas-steam combined cycle cannot always be operated under the design condition because affected by many factors.So in order to understand the unit performance comprehensively,we not only need master the performance of gas-steam combined cycle under the design condition,but also should calculate the operation parameters under the off-design condition and analyze the property.The emphasis and purpose of this paper is analysis and study of the off-design condition property of gas-steam combined cycle unit.The combined cycle with the single-shaft gas turbine and non-additionally heat recovery steam generator is the research object to calculate and analyze the off-design performance.The research background of this paper had been introduced first of all,which included the prospects of gas-steam combined cycle unit in China and the development status at home and abroad.The significance of study the off-design performance of gas-steam combined cycle unit had been discussed in detail.The working principle of the gas-steam combined cycle unit and the operation mode of the gas turbine,heat recovery steam generator and steam turbine were introduced briefly in the paper.The main infection factors of the off-design condition property of the combined cycle unit was analyzed and studied subsequently.The infection factors included the load of unit,atmospheric temperature,atmospheric pressure and humidity,fuel of combustion,steam circulating mode,intake and exhaust pressure losses and so on.The gas-steam combined cycle was decomposed to three modules:gas turbine, heat recovery steam generator and steam turbine making use of the modular modeling method.The off-design condition performances of the three modules were analyzed in detail and the mathematical model was built afterward.Put the decomposed modules together to the gas-steam combined cycle system according to the inputs and outputs of each module.Gave the model reasonable hypothesis and simplification on the base of the factors the paper wanted to study.The performance parameters were calculated after changing the load of unit,atmospheric temperature,and the fuel of combustion on the base of the simplified off-design mathematical models.The paper also calculated the steam parameters after changing gas parameters.In the end,the calculator results were be analyzed and the modules had been built were be proved correct according to the results.