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Prediction of spin rate in Polish 70 mm solid rocket motor

Orbekk E.

Problemy Techniki Uzbrojenia

2004

R. 33, z. 90

17--27

Nammo Raufoss AS (Nammo) has positive experience in using Computational Fluid Dynamics (CFD) for prediction and evaluation of different types of thrust vector systems (TVC), internal flow path design and prediction of flow losses in solid propellant rocket motors. Our Finite-Volume CFD code has been extended during our parcipation in the Norvegian Propulsion Technology Development Programme by including chemical reactions, boundary conditions for burning of solid propellants and particle flow models. The code is adapted for flow field evaluation of solid grain rocket motors.The numerical method for solving the presented Euler and/or Navier-Stokes equations is based on an implicit preconditioned time-accurate integration with upwind biased 3rd order accurate finite volume flux formulation. The chemical reactions are defined through curvefits of the Jensen and Jones reaction rate coefficients. The flow domain is represented by structured grids of multi-block type. Turbulence models are of k-? type. The transport equations are solved for each specie including the solid aluminium oxide particles. The code can be used in equilibrium mode, frozen mode or in non equilibrium mode. This paper presents the CFD code at Nammo and its applications on prediction of spinrate and TVC systems on generic type rocket motors, fired and validated at Nammo, and the future Polish 70 mm rocket motor. The gas in the motor chamber is defined with an appropriate set of chemical reactions describing aluminized and/or non-aluminized burning propellant. The different loss mechanisms in the flow field are calculated, and the results are compared with thrust measurements on fired rocket motors. The evaluation of the Polish 70 mm rocket motor with integrated roll control in the nozzle exit cone has also been evaluated with respect to spin-up during rocket motor burn.