Thermodynamic Effects on Pressure Fluctuations of a Liquid Oxygen Turbopump

Abstract

Liquid oxygen turbopumps are an important component of rocket engines. The instability induced by cavitation flow in turbopumps has received considerable attention because of thermodynamic effects. In this study, unsteady numerical simulations of a turbopump with thermodynamic effects were performed. The frequency composition and source of pressure fluctuations in a turbopump were analyzed, and the difference in pressure fluctuations with/without thermodynamic effects was revealed. The results showed that the pressure fluctuations were mainly caused by the interaction between the impeller and diffuser, and the thermodynamic effects slightly increased the amplitudes of the characteristic frequencies. In addition, in the inducer and impeller, three characteristic frequencies (4.089fn, 2.519fn, and 3.238fn, where fn is the rotational frequency) were confirmed. Analyses revealed that the 4.089fn was due to the periodic shedding of cavitation structures on the suction surfaces at the inducer outlet, 2.519fn was induced by the periodic occurrence and collapse of cavitation on the suction surfaces at the impeller inlet; and 3.238fn was from the periodic shedding of cavitation structures on the suction surfaces at the impeller middle blades. The existence of thermodynamic effects decreased the frequency of cavitation shedding and increased the frequency of the periodic occurrence and collapse of cavitation.

Investigation on pressure fluctuations of dual - and analogical single-rotor turbine flowmeters

“…There is a complex three-dimensional flow inside the flowmeters. The normalised pressure coefficient is represented by equation (7) 19 here, Cp is the pressure coefficient, p is the pressure of the monitoring points (Pa), ptrue¯ is the average pressure of the monitoring points after the rotational speed of the rotors is stable (Pa) and U is the circumferential velocity of the upstream rotor outlet (m/s).…”

“…The monitoring points (13)(14)(15)(16)(17)(18) around the downstream transition are symmetrical to those around the upstream transition. The swirling flow from the back rotor affects the downstream support, and we named more points (19)(20)(21)(22)(23) in the downstream support. Behind the downstream support, 24 and 25 were added.…”

Influence of Rotating Speeds and Thermodynamic Effects on LOX Turbopump Performance

“…In this section, the influence of the thermodynamic effects at a constant rotational speed was studied. In the calculation, the total energy equation considering the viscosity effect and rotation energy was added to obtain the internal flow field, which is applicable to the temperature field calculation of turbopumps and other rotating machinery [41]. To analyze the influence of thermodynamic effects, physical parameters such as density, specific heat capacity, thermal conductivity, and dynamic viscosity that vary with temperature are fitted as functions and written into commercial software ANSYS CFX using CEL language.…”

“…To meet the requirements of liquid rocket engines, researchers are still comprehensively exploring the thermodynamic effects of cryogenic media [35][36][37][38][39][40]. In addition to the thermodynamic effects on cavitation, Li et al [41] employed a liquid oxygen turbopump to investigate the thermodynamic effects on pressure fluctuations. During the exploitation of a new generation launch vehicle, detailed pressure distributions on the rear side of the impeller, which affect the axial thrust characteristics, were obtained via compressible simulation [42][43][44].…”

Comparative Analysis of Strength and Modal Characteristics of a Full Tubular Pump and an Axial Flow Pump Impellers Based on Fluid-Structure Interaction

“…As the core component of the pump, the structural stress of the impeller is caused by periodic water pressure [5,6]. Long-term operation will cause cracks or fatigue damage on the blade surface, which seriously threatens the safe and stable operation of the pump [7][8][9][10].…”