Performance Analysis And Parameters Optimization Of The Bottom Cycle In A Gas Turbine Combined Cycle

Under the multiple background of world,resource shortage and energy saving and emission reduction,more and more attention is paid to the gas power generation and the gas steam combined cycle is an important way of gas power generation.In this paper,taking PG9171 E type gas turbine as object,build component model and introduce relative change rate concept,use MATLAB software programming,and the influence of five kinds of heat recovery boilers with single pressure,double pressure,no reheat,double pressure reheat,three pressure no re heating and three pressure reheat on bottom circulation is analyzed.For non reheat waste heat boiler system,the main steam temperature has the greatest influence on the whole bottom cycle.As for single pressure system,when the main steam increases,the efficiency of waste heat boiler decreases,the efficiency of steam turbine increases and the whole bottom cycle efficiency increases slightly.As for double pressure and the three pressure system,the trend of waste heat boiler efficiency and steam turbine efficiency is the same as single pressure system,and because of its greater impact on turbine efficiency,when the main steam temperature increases,the bottom cycle efficiency increases similarly.For reheat multi pressure HRSG systems,because of the influence of reheat steam,the influence of the main steam temperature on the system is reduced.The influence of reheat steam temperature on the bottom circulation is larger.For the three pressure waste heat boiler system,the influence of medium pressure steam parameters on the bottom circulation is relatively smal.For single pressure waste heat boiler system,node temperature difference has a great influence on the whole bottom cycle,.When the node temperature increases,waste heat boiler efficiency decreases,steam flow reduces,the turbine output power decreases and the bottom cycle efficiency can be reduced.For multi pressure waste heat boiler system,the influence of each node temperature difference on the bottom cycle is not consistent,but in general,consistent with single pressure system.Here we take the node temperature difference as 15 ?.Finally,the constraint conditions are given and the optimization of the bottom cycle efficiency is done.For the single pressure system,main steam parameters are 4.13 MPa,510 ?;For the double pressure non reheat system,the high pressure steam parameters are 6.5 MPa,510?;The low pressure steam parameters are 0.508 MPa,252 ?;For the double pressure reheat system,the high pressure steam parameters are 9MPa,510 ?;The low pressure steam parameters are 0.530 MPa,256 ?;The reheat steam parameters are 2.52 MPa and 510 ?;For the three pressure reheat system,the high pressure steam parameters are6.69 MPa,510 ?;the medium pressure steam parameters are 0.701 MPa,275 ?;the low pressure steam parameters are 0.18 MPa,202 ?;For the three pressure reheat system,the high pressure steam parameters are 9.0MPa,510 ?;the medium pressure steam parameters are 2.55 MPa,325 ?;the low pressure steam parameters are 0.275 MPa,268?;the reheat steam parameters are 2.52 MPa,510 ?.