Based On Composite Lumped Parameter Method In Research On Dynamic Characteristics Of Superheater

With the development of electric power industry of our country,the production oflarge-capacity units has a positive effect on both energy conservation and emissionsreduction and the peak regulation for the electrical network;on the other hand,withascent of steam parameters and automaticity level,after the individual device in powerplant such as machine、furnace and electricity alterative working conditions,thedynamic features which parameters vary with time,and the coupling of the,parametersdynamic features among each device,all of above make the nonlinearnature of controlling equation model more prominent.For this reason, new demandsand challenges are offered to the units staff who design and manufacture ordevices.Because of all devices,the design and operation of the boiler iscompiex,which makes the study of dynamic feature on boiler’s heating surfaceespecially the level tail flue has important meanings in theory and practice.The paper is based on the ifnal superheater of number4subcritical boiler unit ofQin Huang Dao power plant which belongs to Shen Hua companies.After analysingoutside flue gas properties and inside steam properties of ifnal superheater,the papercombines the latest two lumped parameter algorithms,which are many segmentslumped parameter and chain lumped parameter.With it,we can conclude theregulation changing with time and space under the condition of coal consumptionincrease5%step of80%B-MCR, excess air coeiffcient step increase5%step of75%B-MCR and Water flow due to the step increase4%step of80%B-MCR.When studying the dynamic characteristics of many pipe screens,we try tosimplify by choosing single pipe to represent the pipe screen.As the rate betweenpressure一flow channel and enthalpy一temperature channel is different,the stiffnessof differential equations is high,so we choose the variable step size一ode23salgorithm that is used for solving stiff dilTerential equations specially during we use the dynamic simulation sotfware MATLAB/simulink.Its absolute error is1E-4,relative error is IE-3.According to time from the beginning of simulation to theequilibrium stale of simulation,the time we set is about250s?300s.On the basis ofmeeting simulation,we can shotren the simulation time in order to save time.We compare the simulation results of using many segments lumped parameterwith the simulation results of using many segments lumped parameter and chainlumped parameter,ifnding the outcomes of two methods are identical.Therefore theoutcome of later simulation method can reflect the dynamic properties of ifnalsuperheater pipe well.It’s a signiifcant material for operation and debugging of boilerunit.