Design And Shape Optimization Of Clover Combustor Based On The Streamline-tracing Technique

The scramjet is considered as the most ideal propulsion power for hypersonic flight in the near space.Combustion design,as the core component of the scramjet design process,has always been the focus of hypersonic propulsion technology.China's next development of hypersonic aircraft,will face many problems on large-scale scramjet engine combustion design.In this paper,a full three-dimensional circle-to-clover combustion is proposed and designed.In order to have a better aerodynamic performance,the combustion wall was optimized and contrastively researched.At the same time,the applicability of the design method was studied for different outlets cross sections.Then,the research on the characteristics of flow,mixing,and combustion of optimized circle-to-clover combustion with wall injection was carried out.Finally,the optimal surface was studied through experiments.The research in this paper has directive significance for the design of large-scale scramjet combustor.In this paper,embarking upon the research background,the significance of the study was analyzed,the origin of the design idea,the advantages and disadvantages of lobe structure and the application and reliability of the design method were provided,and the feasibility and reliability of the design were supported.The paper introduces a method of designing a reasonable outlet section according to lateral jet formula under the premise of high mixing efficiency,and expounds the design method from the design of basic flow field to the whole profile design.The compatibility equations and the characteristic equations used in the basic flow field and the solution process of the basic flow field(two-dimensional axisymmetric non-rotating basic flow field,two-dimensional axisymmetric isentropic rotational basic flow field)are emphatically explained.The formulas and parameters used in streamline tracing method and surface blending method are also described.Then,the models,mesh generation and boundary conditions are introduced.There into,the N-S equation and the single-equation turbulence model are emphatically introduced.Then,the profile of the combustion not being modified by viscosity correction as well as that of the modified combustion were both optimized.By comparing the numerical simulation results,the optimal combustor with viscosity correction under wide Mach number range was obtained.The effectiveness of viscous correction for basic flow field was verified by comparing aerodynamic performances of the combustor configuration before and after viscosity correction.In the lower part of the article,the number of petals was adjusted to three and the outlet section of the combustion was re-designed.The simulation results shows that the method has applicability for the design of clover combustion with different petal numbers.By comparing the mixing efficiency and combustion efficiency of the clover combustor with the circular combustor,the mixing efficiency and combustion efficiency of the combustion were also studied in this paper.In the second part,the experimental research of the designed combustor was carried out.The pressures of the expansion and the compression on the wall were measured by PSI,and the pressure curve was drawn to compare with the simulation results.In the end,the supersonic inlet boundary was solved by gas inlet parameter,and then the corresponding arc expansion region was solved by the arc expansion solver.Then,the pressure gradient of the wall is reduced by regulating the expansion wave and the compression wave.And therefore a basic flow field is obtained by streamline tracking method.The clover cross-section outlet was set on the calculated two-dimensional basic flow field,and then the flow was traced backwards to obtain a three-Dimensional flow field with clover inlet and outlet.At last,the surface of the three-dimensional flow field and the wall of the two-dimensional viscous basic flow field were merged with the corresponding weight to obtain a circle-to-clover three-dimensional combustor.The combustor has been subjected to wave-shrinking treatment so that the total pressure loss due to shock wave is smaller.And because of the clover combustor's structural characteristics which are helpful for injection and mixing,the combustor is expected to have better combustion performance.