Analysis Of Structural Dynamic Characteristics And Research Of Vibration Attenuation Techniques For Liquid Rocket Engine In Transportation

Liquid rocket engine is installed on the rocket for the railway transport,because of the transportation time is long and the structure of whole engine is "cantilever",the engine is easy to fatigue damage.In the transportation of a gas generator cycle rocket engine,the junction between nozzle-extension and vent-pipe was found damaged.Therefore,it is of practical engineering significance to analyze the dynamic characteristics of the engine and to optimize the vibration reduction scheme,which is helpful to shorten the period of launch and reduce the cost.The research of this paper is based on this type of engine,first,establishing the initial model of rocket engine.After utilizing some principles on effective simplification,the model of the whole engine was constructed in a “from bottom to top” manner,using ANSYS parametric modeling method to establish finite element model of the components.The modeling of thrust chamber and nozzle-extension takes more consideration.The first 40 modes have been calculated,and the results of modified model have shown good agreement with test results.Second,analyzing structual dynamic-characteristics of the rocket engine in transportation.Test data of railway transportation have been utilized to form the input PSD condition at the fixed position of engine thrust frame,and the random-vibration responses were computed.The damp coefficient was chosen in an iteration process of comparing the calculated results with the test data at main measure points.With the given transportation condition by the rocket design group,random-vibration responses were calculated,and the models of important parts were constructed for statics and fatigue analysis,especially,the stress-strain and fatigue damage,and the fatigue properties of important structure was analyzed.Finally,three kinds of vibration reduction schemes were presented,such as rigid support,rigid rod and flexible zippers,which were compared and evaluated.On this basis,the effectiveness of two reinforcement schemes(i.e.flange supporting and nozzle pulling)were verified,to provide a reference for engineering design.