| With the continuous development of China’s aerospace industry,the spacecraft also put forwards higher requirements for reliability,safety and other comprehensive performance.Pipeline separation mechanism served as an important separation device in the staged separation process of the spacecraft,its function is to connect the pipeline and ensure that there is a propellant media supply below the pipeline that meets the required pressure and flow rate during docking,or automatically disconnect the pipeline and seal the two ends of pipeline when separating.However,the existing pipeline separation mechanism is faced with some problems such as the complex structure of the separation force,the large resistance loss of the medium flowing through the separation mechanism and the excessive medium force on the slider during the separation process.And these problems will have a significant impact on the work and performance of the pipeline separation mechanism.Therefore,it is particularly important to optimize the structure and improve performance of the pipeline separation mechanism.This paper takes the newly designed pipeline separation mechanism in the main attitude control power system of the liquid propellant propulsion system of a solid rocket vehicle as the research object.Combined with the knowledge of hydrodynamics and the related theories of numerical analysis,the numerical simulation of the flow field in the separation mechanism was studied by using the professional CFD software Fluent.Based on this,the structure is conducted to optimize analysis,and the reliability of the separation mechanism is studied as follow.Firstly,the three-dimensional model of separation mechanism is established by using Creo.The watershed is extracted and meshed after the simplified treatment.By calculating the steady state of flow field in the separation mechanism,it is determined that the flow resistance of the media and the distribution of the internal flow field are more reasonable when the media flows in from the socket and out from the plug.By adjusting the size and position of the plug spring,the rotating position of the plug slider and the plug spring base,the internal flow field,the flow resistance and the hydrodynamic force of the slider under the inlet of different velocities before and after adjustment are compared and analyzed.And it is determined that the first one method of the three types of assembly is the most reasonable after adjustment.Moreover,the flow resistance characteristics of the adjusted separation mechanism are compared and analyzed through some experiments and the error range is controlled within 5%.Secondly,the dynamic numerical simulation of the plug and socket of the separation mechanism from full open state to close state are separately carried out by using Fluent dynamic mesh technology and User-Defined Function(UDF).By analyzing the closing process of the plug and socket slider,the flow field pressure and velocity distribution in the plug and socket at different times,as well as the movement law of the slider and the medium acting force are obtained.Thirdly,according to the above analysis results,the structure optimization analysis of the separation mechanism plug and socket slider is carried out,respectively.Approximation models about change of the plug-slider’s performance parameters with the number of blades n and the longitudinal dip angle ? were created by the second-order of polynomial response surface methodology to study its performance.The results show that the slider structure is reasonable when the number of blades and longitudinal dip angle are 9 and 0.80 rad,respectively.In order to compare the performance of socket slider,the socket slider adopts five Φ3mm uniformly distributed through-holes on the axis of the slider in the direction of 45°,and the results show that the improved slider can effectively improve the closed cavity phenomenon in the process of closure.Finally,the Failure Mode Effect and Criticality Analysis(FMECA)and the reliability estimation of the pipeline separation mechanism are carried out,and the relevant suggestions are put forward as for the analysis results.Furthermore,the reliability verification of the separation mechanism is verified. |
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