Dynamic modeling of a liquid rocket engine turbo pump rotor

Resumo

Liquid propelled rocket engines present many advantages over its solid propelled counterpart: the
possibility of shutdown and re-ignition in flight and the fact that they are more efficient (greater specific
impulse). For these reasons, they are used in most satellite launching rockets. In a liquid propellant rocket
engine, the oxidizer and fuel must be injected under high pressure into the combustion chamber. This can be
achieved by using pressurized tanks. This solution is technologically simpler and less costly but significantly
limits the injection pressures of propellants. To obtain more powerful engines, propellants must be injected at
higher pressures into the combustion chamber. This is done using a turbo pump, a high-capacity pump powered
by a gas turbine. Turbo pumps operate at high angular speeds (tens of thousands of rpm) and undergo intense
dynamic loads in flight, in addition to the dynamic loads intrinsic to the operation of rotating machines.
Therefore, the dynamic behavior of this type of system must be evaluated at the design stage. In this work, the
transverse displacements of a turbo pump rotor are analyzed using routines developed in the numerical
computation software Octave. The mathematical model developed considers the rotor shaft flexible and rigid
disks. The axis is modeled using finite elements and point masses and inertias are used to represent the disks.
Campbell’s diagram, response to unbalance and forces applied on bearing are obtained. The influence of
bearings positioning on the rotor unbalance response is studied.