CFD ANALYSIS OF FLOW IN THE START SYSTEM OF A LIQUID PROPELLANT ENGINE

Starters are mechanisms that are used for generating the working fluid for initial rotation of LPE (Liquid Propellant Engines) turbopumps. The function of the start system is preparation of initial power for starting a turbine. This turbine is attached to the fuel and oxidizer pumps. When these pumps work in a suitable case, the required power of turbine, is prepared from another source (gas generator) and then there isn't need to starter operation. A solid propellant starter is a solid propellant motor that instead of thrust, momentum of it's exit gases is used for rotating the turbine. The values of power and operating time of starter, are specified from downstream conditions of the start system. Generally, the type and efficiency of turbine and pumps, propellant rate and density, control mechanisms in the path of propellant and etc , are determinant of these values. In this type of start system, gases due to combustion, pass through a convergent-divergent nozzle and enter the turbine and rotate it. In this paper, with due consideration to the role and importance of start system in the process of LPE operation, in order to better recognition of present phenomena in this system, the flow due to combustion in a start system that uses solid propellant, has been simulated via solving the navier-stokes equations. These equations have been expressed in the form of time-dependent, axisymmetric, compressible and viscous and have been solved by means of finite volume methods in company with continuity and energy equations. For finite volume methods the domain is divided up into a number of control volumes, with the value at the centre of the control volume being held to be representative for the value over the entire control volume. By integrating the PDEs over the control volume the equations are cast into a form that ensure conservation.