Main tank injection (MTI) is a pressurization method which employs through combustion inside a reservoir. MTI is simpler and lighter as compared with the common pressurization methods, hence make in suitable for mission launching applications. In this study we evaluated the MTI pressurization system based on unsteady-thermodynamics approach. We used a numerical code which can be performed for the vessels with diameter in the range of 13inch to 60 inch. The proper model for regent injection into the tank in order to provide the demand pressure of the tank is acquired through transient thermodynamics equations. Composition and properties of the pressurizing gas and rate of ullage saturation with propellant vapors are reported based on extensive mass spectrometer gas analysis, an investigation of propellant-degradation due to the reaction process and dilution by condensate is also-Included. The algorithm also obtains the ullage gas temperature and the wall temperature of the tank by using the heat transfer between the ullage gas, the liquid inside the tank, and tank wall. Finally the numerical results are compared with the experimental data, while shows a good agreement between.

Keywords: Pressurization, Main tank injection, Thermodynamic, Transient

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