An unsteady numerical analysis has been conducted to study the strong interaction between impeller blade and volute tongue of a centrifugal pump. The 3-D-URANS equations were solved with the shear stress transport tur...An unsteady numerical analysis has been conducted to study the strong interaction between impeller blade and volute tongue of a centrifugal pump. The 3-D-URANS equations were solved with the shear stress transport turbulence model for a wide range of flow rates. These unsteady interactions are mostly related to the unsteady radial force due to an imbalance in the pressure field at the impeller periphery. This force represents dynamic load that are one of the most important sources of vibration and hydraulic noise. Based on this phenomenon, this work analyzes and gives a more realistic prediction of the pressure fluctuation and the radial force during steady and unsteady calculation by considering the effect of the change in the pump operating point. Actually, the pressure fluctuations in the impeller and the volute were recorded by mounting nine monitoring points on the impeller and volute casing. The results of the existing analysis has proven that the pressure fluctuation is periodic due to the relative position of impeller blade to volute tongue. The characteristics of the time domain and frequency domain of the pressure pulsation were analyzed under different coupling conditions. Fast Fourier transform was performed to obtain the spectra of pressure pulsation. Besides, the steady and unsteady forces were calculated around the impeller periphery to fully characterize the pump behavior. The obtained pump performance curves were numerically compared with the experimental ones, and the outcome have shown an acceptable agreement between both curves.展开更多
Cavitating flows inside a diesel injection nozzle hole were simulated using a mixture model.A two-dimensional(2D)numerical model is proposed in this paper to simulate steady cavitating flows.The Reynolds-averaged Nav...Cavitating flows inside a diesel injection nozzle hole were simulated using a mixture model.A two-dimensional(2D)numerical model is proposed in this paper to simulate steady cavitating flows.The Reynolds-averaged Navier–Stokes equations are solved for the liquid and vapor mixture,which is considered as a single fluid with variable density and expressed as a function of the vapor volume fraction.The closure of this variable is provided by the transport equation with a source term Transport-equation based methods(TEM).The processes of evaporation and condensation are governed by changes in pressure within the flow.The source term is implanted in the CFD code ANSYS CFX.The influence of numerical and physical parameters is presented in detail.The numerical simulations are in good agreement with the experimental data for steady flow.展开更多
文摘An unsteady numerical analysis has been conducted to study the strong interaction between impeller blade and volute tongue of a centrifugal pump. The 3-D-URANS equations were solved with the shear stress transport turbulence model for a wide range of flow rates. These unsteady interactions are mostly related to the unsteady radial force due to an imbalance in the pressure field at the impeller periphery. This force represents dynamic load that are one of the most important sources of vibration and hydraulic noise. Based on this phenomenon, this work analyzes and gives a more realistic prediction of the pressure fluctuation and the radial force during steady and unsteady calculation by considering the effect of the change in the pump operating point. Actually, the pressure fluctuations in the impeller and the volute were recorded by mounting nine monitoring points on the impeller and volute casing. The results of the existing analysis has proven that the pressure fluctuation is periodic due to the relative position of impeller blade to volute tongue. The characteristics of the time domain and frequency domain of the pressure pulsation were analyzed under different coupling conditions. Fast Fourier transform was performed to obtain the spectra of pressure pulsation. Besides, the steady and unsteady forces were calculated around the impeller periphery to fully characterize the pump behavior. The obtained pump performance curves were numerically compared with the experimental ones, and the outcome have shown an acceptable agreement between both curves.
文摘Cavitating flows inside a diesel injection nozzle hole were simulated using a mixture model.A two-dimensional(2D)numerical model is proposed in this paper to simulate steady cavitating flows.The Reynolds-averaged Navier–Stokes equations are solved for the liquid and vapor mixture,which is considered as a single fluid with variable density and expressed as a function of the vapor volume fraction.The closure of this variable is provided by the transport equation with a source term Transport-equation based methods(TEM).The processes of evaporation and condensation are governed by changes in pressure within the flow.The source term is implanted in the CFD code ANSYS CFX.The influence of numerical and physical parameters is presented in detail.The numerical simulations are in good agreement with the experimental data for steady flow.
