Investigation Of Numerical Method And Application Of Spray Combustion For Aeroengine Combustion Chamber

As one of the main components of aeroengine,the performance of combustion chamber directly affects the overall performance of aeroengine.The atomization,evaporation and mixing in combustor have a significant effect on the ignition,flame stabilization,combustion efficiency,pressure loss,exit temperature distribution and emissions.Thus,a thorough study about the process of spray atomization,especially about the process of primary atomization,is critical to bring insight into the mechanism of atomization combustion in aeroengine combustion chamber with high temperature and pressure,and strong swirl.It has an important theoretical significance and practical value for understanding the turbulent two-phase combustion in aeroengine combustion chamber and guiding the design of combustion chamber that experimental and numerical researches on the kerosene atomization combustion are carried out in aeroengine combustion chamber.In this work,the researches on jet atomization theory are reviewed,and the jet atomization mechanisms are summarized,including the primary atomization mechanisms,the secondary atomization mechanisms,and the collision and the evaporation process of sprays.Meanwhile,the research progresses in fuel atomization combustion of aeroengine combustion chamber at home and abroad are summarized.In current paper,the numerical models about the primary and secondary atomization and heating and evaporation of sprays are established,and a self-developed numerical software of the three-dimensional two-phase combustion in aeroengine combustion chamber is developed.The primary atomization model adopts Linearized Instability Sheet Atomization(LISA)model and WAVE breakup model.LISA model can model the establishment and breakup process of liquid film,and its atomization process.WAVE breakup model is developed based on Kelvin-Helmholtz(K-H)Instability theory,which can model the primary atomization of jet.Kelvin-Helmholtz Ravleigh-Taylor(KH-RT)model is adopted as the secondary atomization model,which takes the effects of KH and RT instability into consideration simultaneously.The reliability of the atomization models developed in current paper is verified through several cases.In the case of jet atomization in cross flow,the reliability of WAVE breakup model and KH-RT model is verified,and the applicability of several secondary atomization models is compared.In the case of methanol spray atomization lifted flame,the lifted height,flame structure,distribution of species and spatial distribution of sprays properties under different conditions are studied numerically,and the reliability of WAVE breakup model and KH-RT model is further validated,and moreover the reliability of standard evaporation model and flamelet combustion model adopted in current paper is verified.In the case of spray combustion of lean direct injection injector,the LISA and KH-RT models are used in the simulation of primary and secondary atomization process under condition of strong swirl respectively,and standard evaporation model and flamelet model are used to model the sprays combustion process.The velocity and diameters distributions of sprays droplets are obtained in non-reactive and reactive conditions.The reliability of LISA model and KH-RT model is verified in strong swirl condition,and the reliability of evaporation model and combustion model is further validated.The atomization field of a pressure-swirl atomizer is measured under atmospheric pressure and temperature,using the particle field pulsed laser holography imaging technique,and the spatial distribution of sprays droplets diameter and number density obtained.Moreover,This pressure-swirl atomizer is studied numerically,and the numerical results have a good agreement with experimental results,verifying the correctness of atomization model developed in current paper.Using Volume of Fluid(VOF)method coupled with Large-eddy Simulation(LES),the primary breakup process of direct injection and deformation and breakup process of jet column in the cross flow are directly simulated,exploring the primary breakup mechanism of jet column.The detailed structure of the process of jet column is captured successfully,and during the breakup developing process from the windward side to two sides of jet column,the breakup is dominated by R-T surface wave firstly and then dominated by K-H surface wave.The atomization process in aeroengine combustion chamber is studied with the particle field pulsed laser holography imaging technique,the spatial distribution of droplets diameter,velocity and number density in combustor are obtained.In addition this atomization process in this combustor is studied numerically,obtaining the distribution of fuel spray droplets in combustor,and comparing the droplets diameters with experimental results.Moreover the spray combustion process in this combustor is studied under mode condition numerically,obtaining the distribution of species concentration,exit temperature,kerosene droplets which include droplets number,diameter and velocity.As shown from the results,atomization model developed in current paper can properly reflect the whole process from injection and combustion of fuel under the conditions of high temperature and pressure and strong swirl in aeroengine combustion chamber.