In this paper, we study the connectedness of the invariant sets of a graph-directed iterated function system（IFS）. For a graph-directed IFS with N states, we construct N graphs. We prove that all the invariant sets ...In this paper, we study the connectedness of the invariant sets of a graph-directed iterated function system（IFS）. For a graph-directed IFS with N states, we construct N graphs. We prove that all the invariant sets are connected, if and only if all the N graphs are connected; in this case, the invariant sets are all locally connected and path connected. Our result extends the results on the connectedness of the self-similar sets.展开更多
The rocket ejector has great potential for bridging the thrust gap between the turbine and ramjet modes of the Turbine-Based Combined Cycle(TBCC) engine.In this work,a rocket ejector was proposed and used in the Eject...The rocket ejector has great potential for bridging the thrust gap between the turbine and ramjet modes of the Turbine-Based Combined Cycle(TBCC) engine.In this work,a rocket ejector was proposed and used in the Ejector-Ramjet(ERJ) engine model.Furthermore,the thrust and thermal-fatigue performances of the rocket ejector are investigated through the thrust bench tests.The combustion stability and performance of ERJ engine are studied by the ground direct-connect experiments under different conditions.Experimental results suggest that the rocket ejector can realize a wide range of thrust variation from 510 N to 1 100 N and a specific impulse of more than250 s,whereas accompanying with a short lifespan about 4 s.As expected,the rocket ejector can significantly expand the flight envelope of the ERJ engine downward to Mach number Ma_(∞)=2.0 and altitude H = 13 km.Nevertheless,when Ma∞is less than or equal to 3.0,the ramjet combustor is unable individually operated and that need to be improved for engineering application.The lower oxygen/kerosene ratio of rocket ejector and the equalized injection-forward and injection-center of ramjet fuel are beneficial for enhancing the combustion stability and thrust performance of ERJ engine.Overall,experiments primarily validated that the rocket ejector has the advantages of facilitating ignition and flame stabilization,improving the working environment of the ERJ engine,and expanding the operating range.But the remarkable thing is that both the ejector and ramjet combustor can be greatly improved for optimizing the performance of ERJ engine further.展开更多
基金Supported by the Teaching Research Project of Hubei Province(2013469)the 12th Five-Year Project of Education Plan of Hubei Province(2014B379)
文摘In this paper, we study the connectedness of the invariant sets of a graph-directed iterated function system（IFS）. For a graph-directed IFS with N states, we construct N graphs. We prove that all the invariant sets are connected, if and only if all the N graphs are connected; in this case, the invariant sets are all locally connected and path connected. Our result extends the results on the connectedness of the self-similar sets.
基金funded by the Advanced Aerospace Force Innovation Workstation in China(No.HKCX2019-01–002)supported by the China Association for Science and Technology Youth Talent Nurturing Program+3 种基金the National Key Laboratory of Ramjet in China(No.WDZC6142703202407)the National Natural Science Foundation of China(No.12402393)the Fujian Provincial Natural Science Foundation of China(No.2024J08020)the Natural Science Foundation of Xiamen in China(No.3502Z202372010)。
文摘The rocket ejector has great potential for bridging the thrust gap between the turbine and ramjet modes of the Turbine-Based Combined Cycle(TBCC) engine.In this work,a rocket ejector was proposed and used in the Ejector-Ramjet(ERJ) engine model.Furthermore,the thrust and thermal-fatigue performances of the rocket ejector are investigated through the thrust bench tests.The combustion stability and performance of ERJ engine are studied by the ground direct-connect experiments under different conditions.Experimental results suggest that the rocket ejector can realize a wide range of thrust variation from 510 N to 1 100 N and a specific impulse of more than250 s,whereas accompanying with a short lifespan about 4 s.As expected,the rocket ejector can significantly expand the flight envelope of the ERJ engine downward to Mach number Ma_(∞)=2.0 and altitude H = 13 km.Nevertheless,when Ma∞is less than or equal to 3.0,the ramjet combustor is unable individually operated and that need to be improved for engineering application.The lower oxygen/kerosene ratio of rocket ejector and the equalized injection-forward and injection-center of ramjet fuel are beneficial for enhancing the combustion stability and thrust performance of ERJ engine.Overall,experiments primarily validated that the rocket ejector has the advantages of facilitating ignition and flame stabilization,improving the working environment of the ERJ engine,and expanding the operating range.But the remarkable thing is that both the ejector and ramjet combustor can be greatly improved for optimizing the performance of ERJ engine further.
