Developmentand Numericalstudyof Constant Pressure Combustion Chamberbasedon MILD Combustion

As the development of the stirling engine with high backpressure and efficiency,the combustor in small space and ultrahigh pressure gradually becomes popular,but this kind of combustors always has the problem of unstable combustion that the maximum temperature is excessive,the localtemperature is high,the temperature distribution in the combustor is inhomogeneous,so that the flame plate is sublimated and the fuel nozzle is broken down.As a result,the performance and efficiency of the external combustion system decline.In order to solve the above problem,it is necessary to find a new clean combustion technology to study.MILD combustion technology has advantages of a variety of clean combustion technologies,so that targets of high efficiency,low maximum temperature and homogeneous temperature distribution can be met.Therefore it becomes one of the key combustion technologies to optimizethe external combustion system of stirling engine.Nowadays,research on MILD combustion mainly focuses on gas and solid fuels while gas and liquid fuels are less adopted.Therefore this thesis is based on the study of MILD combustion with gas and liquid fuels,a MILD combustion train for researches on stirling engine is designed,theconstantpressure combustion chamber(CPCC)is established and relative numerical study is also done.The detail work of this thesis is as follows:(1)The network model of Oxy-Fuel MILD combustion is built for numerical study with the skeleton chemical reaction mechanism of n-heptane.The effects of exhaust gas temperature,pressure,fuel oxygen equivalence ratio have been researched.In addition,the entrainment ratioconditionand Damk?hler numberof MILD combustion are discussed and the basic test conditions are givenand the numerical simulation results are verified by relative tests which are done in a chamber of a now available Stirling engine.(2)According to the design conditions and requirementsbased on the study of MILD combustion with gas and liquid fuels,principle design of CPCC system has been finished.The thermal analysis of CPCC consists of the heat balance calculation,theoptimization calculation with zirconia and the calculation of fan cooling power.Besides,the core components of CPCC have been checked for the strength,which includethe inner container with a base,the outer sleeve,the optical glass and the bolt.As a result,CPCC can be applied to do relative studies of MILD combustion on stirling engine.(3)In order to meet the test requirements,CPCC laboratory is established with five subsystems that contain the gas system,the oil system,the optics system,the electronic control system and the visualized interface.(4)Furthermore,numerical study of Oxy-Fuel MILD combustion in 3D combined with CPCC is carried out in both swirled-flow and straight-flow situations.The effects of relative factors are studiedso that the next tests in CPCC can be guided.