Research On Impingement Cooling Of Gas Turbine Low Emission Combustor

In structural design,on one hand,for enhancing gas turbine efficiency,the temperature rise of combustor is continuous increased.So the combustor cooling structure is forced to improve because of the increasing temperature.Moreover,the environmental problems are focused by the public.The <Emission standard of air pollutants for thermal power plants> is implemented by China in 2012,which required the NOx emission of gas turbine outlet should less than 25 ppm.It promotes the research of low emission combustor to a higher degree.Lean premixed combustion is one of the important methods for reducing the emission index.However,under the condition of lean combustions,more air is needed.And the quantity of cooling air has to reduce for conventional combustor cooling structure.It brings more challenges to combustor structural design.So it's very necessary to carry out the work of analysis and design for the cooling structure of lean premixed combustor.This paper will complete the following tasks principally:Firstly,after investigating some primary cooling structure of combustor,the research of this paper was focused on impingement cooling structure under considering the requirements of low emission and wall cooling efficiency.Numerical simulation has been made to research the aerodynamic performance,temperature field of wall and interior,as well as low emission for the cannular prototype combustor which used film-cooling structure.Secondly,the influence of structure parameters on impingement cooling effectiveness has been researched by simulation of plate impingement cooling.The results show that: the best cooling effectiveness occurs when the hole has no obliquity,the jet-to-surface spacing to diameter ratio is 2 to 3.5,the longitudinal spacing to diameter ratio is about 8,the transverse spacing to diameter ratio is 6.5 to 10,the holes are cross arranged,and the diameter should as small as possible.Thirdly,three new impingement cooling structures have been designed based on the foundation of prototype combustor.Numerical simulation has been made to compare the performance between the combustor which used impingement cooling structures and the prototype combustor which used film-cooling structure.The results show that although the total pressure loss and outlet temperature distribution factor(OTDF)increase when using impingement cooling structure,the maximum temperature of wall and CO emission reduce sharply.In this paper,based on the research of the impingement cooling of Low Emission Combustor,the basic characteristics and laws of lean premixed combustor were mastered.It has important guiding significance to design optimization of subsequent low emission combustor.