A theoretical model of focused acoustic field for a multi-annular phased array on concave spherical surface is proposed. In this model, the source boundary conditions of the spheroidal beam equation （SBE） for multi-...A theoretical model of focused acoustic field for a multi-annular phased array on concave spherical surface is proposed. In this model, the source boundary conditions of the spheroidal beam equation （SBE） for multi-annular phased elements are studied. Acoustic field calculated by the dynamic focusing model of SBE is compared with numerical results of the O＇Neil and Khokhlov-Zabolotskaya-Kuznetsov （KZK） model, respectively. Axia/dynamic focusing and the harmonic effects are presented. The results demonstrate that the dynamic focusing model of SBE is good valid for a concave multi-annular phased array with a large aperture angle in the linear or nonlinear field.展开更多
Efficient air-fuel mixing is essential for achieving stable combustion,reducing emissions,and enhancing the overall performance of gas turbine combustors.This study provides a detailed computational investigation of s...Efficient air-fuel mixing is essential for achieving stable combustion,reducing emissions,and enhancing the overall performance of gas turbine combustors.This study provides a detailed computational investigation of swirling air jet mixing in confined geometries,with direct relevance to air-fuel mixing processes in gas turbine applications.The simulations employed the realizable k-εturbulence model and were validated against existing experimental data,showing strong agreement.Computational investigations were performed using ANSYS Fluent in enclosures of fixed length but varying diameter,achieved by progressively introducing annular jets to form multi-annular configurations comprising 2 to 6 jets.While the central jet is conceptualized as a fuel jet and the surrounding annular jets as air,all jets are modelled as air to isolate the fundamental mixing behaviour.The introduction of additional annular jets increases the total mass flow rate,significantly influencing internal flow structures.Clear signs of improved mixing were seen in the significant increase in the central recirculation zone(CRZ)and the corresponding decrease in centreline axial velocity.To gain deeper insight into the flow behavior,each set of jet’s configurations was investigated using two different swirl intensity combinations.Findings indicated that a greater difference in swirl strength enhanced the formation of the central recirculation zone(CRZ)and reduced axial velocities along the centerline,suggesting more effective interaction and mixing between the jets.展开更多
Multi-annular jets are derived from coaxial jets,which are used to improve the mixing of fuel and air before ignition in a gas turbine combustor and it is essential to achieving stable and effective combustion.In the ...Multi-annular jets are derived from coaxial jets,which are used to improve the mixing of fuel and air before ignition in a gas turbine combustor and it is essential to achieving stable and effective combustion.In the present work,a multi-annular jet comprising two co-annular and one central jet has been used to understand the flow characteristics and mixing of jets in nonexpanded and expanded confinement with different angular outlets.A computational investigation has been performed with different swirl combinations in three air jets inlet under non-combustion conditions.After validation from existing experimental results,parametric studies have been investigated with different expansion ratios,different swirl combinations,and different angular outlets.Using the realizable k–εturbulence model and commercial software ANSYS FLUENT,results were obtained in the form of streamlines plots,axial velocity contours,and center line axial velocity.Following a comprehensive analysis of the computational output,it is found the mixing process in confinement depends on expansion ratios,swirl combinations,and angular outlets.Results show that the mixing of jets is enhanced in expanded confinement at particular swirl combinations and at certain angular outlets.展开更多
The technique of the use of multi-annular opposed jets as different from using swirl and bluff body creates an excellent recirculation zone with desired size in a large space.The size of recirculation,the magnitude of...The technique of the use of multi-annular opposed jets as different from using swirl and bluff body creates an excellent recirculation zone with desired size in a large space.The size of recirculation,the magnitude of reverse velocity and turbulence intensity are much greater than those formed by bluff body.Factors affecting the flowfield include the velocity ratio of the opposed jets to the primary air J,the diameter and construction of the opposed jet ring,secondary air velocity and configuration,and confined or unconfined flow condition and so on.This method is a promising way for flame stabilization in combustion technology.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos. 39970209 and 30772072
文摘A theoretical model of focused acoustic field for a multi-annular phased array on concave spherical surface is proposed. In this model, the source boundary conditions of the spheroidal beam equation （SBE） for multi-annular phased elements are studied. Acoustic field calculated by the dynamic focusing model of SBE is compared with numerical results of the O＇Neil and Khokhlov-Zabolotskaya-Kuznetsov （KZK） model, respectively. Axia/dynamic focusing and the harmonic effects are presented. The results demonstrate that the dynamic focusing model of SBE is good valid for a concave multi-annular phased array with a large aperture angle in the linear or nonlinear field.
文摘Efficient air-fuel mixing is essential for achieving stable combustion,reducing emissions,and enhancing the overall performance of gas turbine combustors.This study provides a detailed computational investigation of swirling air jet mixing in confined geometries,with direct relevance to air-fuel mixing processes in gas turbine applications.The simulations employed the realizable k-εturbulence model and were validated against existing experimental data,showing strong agreement.Computational investigations were performed using ANSYS Fluent in enclosures of fixed length but varying diameter,achieved by progressively introducing annular jets to form multi-annular configurations comprising 2 to 6 jets.While the central jet is conceptualized as a fuel jet and the surrounding annular jets as air,all jets are modelled as air to isolate the fundamental mixing behaviour.The introduction of additional annular jets increases the total mass flow rate,significantly influencing internal flow structures.Clear signs of improved mixing were seen in the significant increase in the central recirculation zone(CRZ)and the corresponding decrease in centreline axial velocity.To gain deeper insight into the flow behavior,each set of jet’s configurations was investigated using two different swirl intensity combinations.Findings indicated that a greater difference in swirl strength enhanced the formation of the central recirculation zone(CRZ)and reduced axial velocities along the centerline,suggesting more effective interaction and mixing between the jets.
文摘Multi-annular jets are derived from coaxial jets,which are used to improve the mixing of fuel and air before ignition in a gas turbine combustor and it is essential to achieving stable and effective combustion.In the present work,a multi-annular jet comprising two co-annular and one central jet has been used to understand the flow characteristics and mixing of jets in nonexpanded and expanded confinement with different angular outlets.A computational investigation has been performed with different swirl combinations in three air jets inlet under non-combustion conditions.After validation from existing experimental results,parametric studies have been investigated with different expansion ratios,different swirl combinations,and different angular outlets.Using the realizable k–εturbulence model and commercial software ANSYS FLUENT,results were obtained in the form of streamlines plots,axial velocity contours,and center line axial velocity.Following a comprehensive analysis of the computational output,it is found the mixing process in confinement depends on expansion ratios,swirl combinations,and angular outlets.Results show that the mixing of jets is enhanced in expanded confinement at particular swirl combinations and at certain angular outlets.
文摘The technique of the use of multi-annular opposed jets as different from using swirl and bluff body creates an excellent recirculation zone with desired size in a large space.The size of recirculation,the magnitude of reverse velocity and turbulence intensity are much greater than those formed by bluff body.Factors affecting the flowfield include the velocity ratio of the opposed jets to the primary air J,the diameter and construction of the opposed jet ring,secondary air velocity and configuration,and confined or unconfined flow condition and so on.This method is a promising way for flame stabilization in combustion technology.
