COMPUTATION OF BPF PRESSURE PULSATIONS IN THE LRE SCREW-CENTRIFUGAL PUMP WITH 3D ACOUSTIC-VORTEX METHOD

The issues of the liquid rocket engine reliability and service life are taking more attention recently. The key factor in providing the LRE higher service life is reduction the hydrodynamic vibration of screw-centrifugal pumps caused by pressure pulsations in the pump flow path. Blade passing frequency discrete components dominate in spectra of pressure pulsations. These oscillations cause dynamic loads on the pump housing, causing it to vibrate, so the calculation of the amplitudes of pressure pulsations in a screw-centrifugal pump at an early development stage is an important task. In determining the pressure pulsations generated by three-dimensional vortex flow in the screw-centrifugal pump one must account their dual nature. Inhomogeneous distribution of the flow at the outlet of the impeller generates acoustic disturbances that spread with the speed of sound in the working fluid. At the same time there are vortex disturbances that convey with the main flow. Vortex pressure fluctuations of the main flow is called "pseudosound" or vortex mode. The oscillation amplitude of the vortex mode can be determined with the unsteady flow computation using the incompressible fluid model. However, this model is not applicable for acoustic fluctuations spreading to the pump outlet and in the pressure pipe. In this article a three-dimensional acoustic-vortex method is developing for calculation the pressure pulsations, which provides the possibility of determining the acoustic mode amplitude. There are outlined derivation of acoustic vortex equations and example of calculation the amplitude of the pressure pulsations at the screw-centrifugal pump outlet of liquid rocket engine with alternative guide channel designs.