The Numerical Study On The Performance Of Gas-Liquid Two-Phase Atomization Of Fuel Injector

In order to study the atomization of the fuel injector in the gas turbine combustor,the plannar prefilming airblast atomizer and the KIAI n-heptane spray combustor with a radial swirl atomizer provided by CORIA laboratory were selected as the research objects in this paper.OpenFOAM,an open-source computational fluid dynamics software,was used to study the atomization process and performance during the primary and secondary atomization.A primary study of the coupling methods of primary atomization and secondary atomization was also carried out.The results of the study in this thesis provide support to the research and design of gas turbine atomizer.In this paper,the multiphase flow solver interFoam which based on the VOF method was chosen to simulate the primary breakup in a planar prefilming airblast atomizer.The turbulence models applied were the standard k-ε turbulence model(URANS: Unsteady Reynolds Average Navier-Stokes)and the sub-grid scale k-equation turbulence model(LES: Large Eddy Simulation).The simulation results were compared with the experimental results.The results show that:(1)The numerical simulation results of gas phase velocity and RMS agree well with the experiment data for the single phase case;(2)With the increase of weber number,the turbulent kinetic energy at the gas-liquid interface increases,which promotes the breakup of the liquid film;(3)The results of LES clearly reflect the change of the fuel from continuous liquid film to blob or mass,and the instability on the surface of liquid film.Then in order to study the characteristics of secondary atomization,A cone hollow injector with radial swirler from the KIAI n-heptane spray combustor was selected as the research object.The sprayFoam solver based on Lagrange approach was used to simulate the droplets’ breakup and development of the n-heptane spray in the combustor.At the same time,the influence of injection model and breakup model to the simulation of the secondary atomization was also studied.Compared with the experiment data,the results show that:(1)The velocity distribution of single-phase flow case and multiphase flow case is in good agreement with the experiment results;(2)when the breakup model is not taken into account,the mean diameter of fuel droplet and the radial expansion distance of spray is larger than that obtained by TAB(Taylor Analogy Breakup)model.And the simulation results with the TAB model are in better agreement with the droplet diameter distribution measured in the experiment.In order to solve the coupling problem between primary atomization and secondary atomization in the whole process of atomization simulation,the droplet transfer method was introduced in this paper.In the flow field after primary atomization,the liquid structure captured through the interface is searched by this method,and droplets that meet specific standards are screened out.Then the information of these droplets will be transmitted to the Lagrange particle tracking system,used to simulate the initial droplet conditions of secondary atomization.The algorithm of droplet transfer was programed and implemented into the solver of OpenFOAM.Numerical simulation was carried out with the airblast atomizer as the validation case,and the preliminary simulation results of the droplet selection from primary atomization were obtained.