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  • Transient analysis of open cycle liquid propellant rocket engine

    Paper number



    Mr. Soon-young Park, Korea Aerospace Research Institute, Korea


    Dr. Woo Seok Seol, Korea Aerospace Research Institute, Korea


    Dr. Won-Kook Cho, Korea Aerospace Research Institute, Korea



    There are several definite objects for developing the startup of liquid rocket engine (LRE). One is the repeatability of startup to ensure the reliability, and the other is to reduce the time required for the startup transient. Also it is very ambiguous for us to define the initial conditions of the engine system test and to conjecture the whole time required for startup. \\
      Before preceding the hot-firing test it is quite evitable to develop a computer program which can help the study on the transient features of LRE. In this work, we developed a startup transient analysis tool by introducing the mathematical model of each components of open cycle rocket engine. Oxidizer was LOx, and fuel was kerosene. 
    Combustion chamber pressure was calculated as a function of supplying mass flow rate and propellant mixture ratio using the well-known CEA code. Gas-generator combustion temperature was interpolated existing experimental results. Also, turbopump performance curve was used to represent the off-design characteristic of it. Especially we proposed a mathematical model for the thrust regulating device and coupled gas-generator combustion pressure stabilizing device (PS). PS was modeled as an 1-dimensional mass-spring-damp system with an external force which is actually the product of pressure difference and area of the membrane at the PS. At the end we composed mass and pressure balancing logic to integrate all these components of LRE. \\
      As an example we derived the time required from the startup command to the nominal state of the 250 kN thrust level engine, also it was possible to optimize the intermediate thrust level during the startup for two step startup sequence. And we were able to define the mechanical stability map as a function of damping ratio and natural frequency of the PS by applying temporal transient analysis around the nominal state of the engine.
    Abstract document