Mathematic simulation and performance computation of combustion products of Combined Solid-propellant Rocket-ramjet Motor gas-generator
Aerospace propulsion engineering
Аuthors*, **, ***
Engineering Design Bureau”Iskra” named after Ivan Kartukov, 35, Leningradskoe shosse, Moscow, 125284, Russia
The article is considered issues of mathematic simulation of flow performance of working medium in combustion chamber of gas-generator and duct of fuel flow controller under computational solution of equations of internal ballistics in nonstationary scenario and calculation in CFD. Examples of such calculation results are given.
Major units of CSRM (Combined Solid-propellant Rocket-ramjet Motor) are air intake, gas-generator of solid propellant, fuel flow controller, afterburner chamber with charge of booster and nozzle. Signal of predetermined consumption is transformed into required pivot angle of fuel controller drive. Drive pivoting changes area of nozzle controller openings, and as a result of it, causes variation of pressure and consumption of sustain engine. After gas-products of incomplete combustion of solid propellant of gas-generator charge got through fuel flow controller, they fell into afterburner chamber where burnt down in the air flow from intake.
During the design phase without reliable experimental data of combustion processes in engine passage under thermodynamic calculation we apply for equilibrium condition model of combustion products. Calculation of the equilibrium condition is numerically carried out by computer. The task optimization-minimization of Gibbs energy of combustion products is solved. Further equation system of internal ballistics is solved for combustion chamber of gas-generator. The solution is got by Runge-Kutta method of fourth order.
The results of preliminary ballistic calculation of gas-generator are used as initial data for flow simulation in fuel flow controller. Study object is unit of consumption regulator of gas-generator products Flow control of gas-generator products is carried out by variation of area of internal cross section in central opening of nozzle insert by means of moving center body along axis of controller.
Controller study was conducted at the limit mode, with almost completely closed central hole. This mode is characterized by a large pressure drop (gas-generator chamber 12 MPa and afterburner chamber 1,4 MPa) and maximum flow of gas-generator products.Computation is done in program complex of СFD in stationary scenario.
Calculated case is characterized by overexpansion of flow in expanding part of nozzles, in consequence of which, shock wave is formed and flow rate transforms from supersonic to subsonic. Movement in passage is uniform, some small eddies are present, major consumption falls on two constantly opened nozzle orifices.
Keywords:CSRM (Combined Solid-propellant Rocket-ramjet Motor), SFDR (Solid Fuel Ducted Rocket Ramjet), gas generator, fuel flow controller, computer simulation, propulsion system, rocket ramjet, ducted rocket engine, solid propellant, mathematic simulation, experimental method
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