Low Emission Design Research Of Annular Combustor

The emission standard of engine is increasingly demanding in today’s world,low emission becomes one of the important performance indexes of advanced combustor,so it becomes very necessary to design advanced low emission combustor.For the NOx emission of gas turbine combustor,the major influence parameters are temperature and excess air ratio of reaction zone.So the usual way of decreasing NOx emission is controlling these two parameters when designing low emission combustors.But traditional design method of combustor structure mainly using experience formula and half experience formula,it may take long period,high cost,and poor portability.If the reactor network method is used to design the low emission combustor flow field,it will optimize the combustor air inlet plan,lower the NOx emission and combustion temperature by design the excess air ratio of each reaction zone in flow field.It will also give us a middle step between 0-D design and 3-D design.This 1-D design results can modify 0-D design and guide 3-D design.And finally confirm the detail design of combustor structure by comparing the numerical simulation results of three-dimensional combustion flow field,and analyzing the performance and optimal design,this may not only save costs,but also shorten the design period.To ensure the efficiency and accuracy of this 0-D 1-D and 3-D interactive design method of low emission combutors,there are lots of problems need to be solved.Such as:how to control the excess air ratio of reaction zone in 1-D design to lower NOx emission,how to achieve the air inlet ratio plan and the reactor volume of 1-D design,which are major influence parameters when adjusting combustor structure to fit 1-D design,how to simplify the adjusting process to fulfill the low emission design requirement quickly,and so on.It can save more time if parametric modeling method is used in the design process to establish the combustor geometry structure and build mesh.But parametric modeling method has never been used in such complex structure as combustor,so a lot of difficulties must be overcame in order to achieve the combustor parametric modeling.To solve these problems,this paper conducted the following research work:1.A parametric modeling system including swirler and flame tube of gas turbine combustor is established,which has clearly and perfectly design of menu and windows,it can realize the parametric geometric modeling of swirler and flame tube of annular combustor,it only takes a few minutes to modify and update the combustor model,which saves 99%time comparing with the traditional method.2.A multi-dimensional interactive design method of low emission combustor is established,by controlling the excess air ratio of reaction zone to lower NOx emission,a low emission combustor geometry structure is designed using this method:(1)Preliminary zero-dimensional design is carried based on the traditional experience formula of normal combuator.The thermal dynamic calculation of combustor,aerodynamic calculation of overall size of combustor,and experience estimation of the air inflow of each part are carried out.(2)Low emission combustor one-dimensional design is analyzed by using CRN method.Chemical reactor network of flow field is established.The air inlet ratio plan with the lowest emission is optimized by analyzing NOx emission under different excess air ratio of reaction zone,the effective combustion volume of the combustor is confirmed by micro-element method,and the one-dimensional characteristic length is calculated.(3)By using parametric modeling system,with guidance of one-dimensional design about the gas distribution plan and the characteristic length,combustion flowfield of different combustor structures are compared to choose one combustor structure.It proves that this multi-dimensional interactive design method of low emission combustor saves more time than the traditional method.3.After analyzing the parameters wich influencing recirculation zone,the connection between recirculation zone and the swirl number of swirler is fitted to a polynomial expression.The connection between recirculation zone and circulation zone is calculated.4.A area-flow coefficient is defined and used in combustor design work.The accuracy of the coefficient is verified.It can be used to quickly compute the size of the three-dimensional geometry structure based on air inlet size parameter from the one-dimensional design result.That will save a lot of adjusting work and improve the accuracy of the three-dimensional design.