Entropy production by dissipation effects and characteristic vortex evolution in a rocket turbopump

Abstract

The relationship between entropy production and vortex evolution affects the efficiency and stability of rotating machinery. This study investigated the energy characteristics of a rocket turbopump and revealed the correlated mechanisms of the entropy production rate using the dissipation effects and characteristic vortex evolution. For the first time, direct and turbulent dissipation and rigid and shear vorticity decomposition methods were utilized to analyze the correlation between flow loss and characteristic vorticities in rotating machinery. With an increase in the flow rate, the hydraulic losses of the dissipation effects and wall decreased by 60% and 38.3%, respectively, and the proportions of the input energy decreased (from 13% to 8%) and remained stable (8%), respectively. The local direct dissipative entropy production (DDEP) in the inducer-impeller is strongly related to shear entropy, and the correlated effect of total enstrophy on DDEP is weaker than that of shear vorticity, indicating that rigid enstrophy suppresses direct dissipation. The correlation between turbulent dissipation and rigid enstrophy was significantly weaker in the static flow passage of the turbopump owing to the weak rigid rotational effect. The correlation between the rigid entropy and local turbulent dissipative entropy production (TDEP) gradually increased with increasing flow rate, reaching a medium correlation (the maximal correlated degree in the turbopump) and exhibiting rigid rotation effects on the hydraulic loss. Moreover, the flow rate significantly affected the correlation (except for the diffuser), and the two characteristic vorticities reached a maximum at the designed flow rate owing to optimal efficiency and minimum hydraulic loss.