The average-passage equation system(APES)provides a rigorous framework to account for the deterministic unsteady effects by the so-called deterministic correlations(DC),which include both deterministic stress correlat...The average-passage equation system(APES)provides a rigorous framework to account for the deterministic unsteady effects by the so-called deterministic correlations(DC),which include both deterministic stress correlations(DCS)and deterministic total enthalpy correlations(DCH).These correlations should be modeled to close the system of equations.In this paper,the distribution of DC in a transonic centrifugal compressor is presented,and its relative importance is revealed.The assumption made by Adamczyk that the pure unsteady fluctuation is significantly smaller than the spatial fluctuation is verified at the impeller-diffuser interface.The decomposition of DCH is also discussed to determine its two different physical mechanisms.Finally,the transport equations in terms of DCS in cylindrical coordinates are derived,and the terms are evaluated to determine the ones that are necessary to model.All these analyses significantly contribute to our model development for DC in centrifugal compressors.展开更多
Numerical simulation on the unsteady flow in a centrifugal compressor isperformed, and compared with the experimental data. The influence of the impeller-diffuserinteraction on the flow-fields is discussed, and the re...Numerical simulation on the unsteady flow in a centrifugal compressor isperformed, and compared with the experimental data. The influence of the impeller-diffuserinteraction on the flow-fields is discussed, and the reasons for the losses are also explored.Results show that qualitative and quite fair quantitative agreements are achieved between thepredicted and measured flowfields. The influence of the impeller wake on the convexity surface ofdiffuser is great. The potential repercussion of the diffuser on the suction surface of the impelleris much larger than on the pressure surface. Effect of the unsteady interaction is strongest in theradial gap. The unsteady flow itself may compensate for the loss generated in stage, and the stageefficiency is inversely proportional to the entropy production.展开更多
The strong interaction in a radial pump due to the relative movement between the impeller and the diffuser may excite not only strong pressure fluctuations but also velocity fluctuations. In this paper, the laser Dopp...The strong interaction in a radial pump due to the relative movement between the impeller and the diffuser may excite not only strong pressure fluctuations but also velocity fluctuations. In this paper, the laser Doppler velocimetry （LDV） technique is successfully applied to measure the periodic flow field in a radial diffuser pump with low-specific speed, in order to investigate the velocity fluctuations caused by the impeller-diffuser interactions both in the impeller and diffuser regions. The velocity fluctuations in the impeller region are quantitatively examined at different radial positions, and the flow structure at the radial gap between two flow components is analyzed at different relative positions. In addition, the downstream effect on the diffuser flow is quantitatively and qualitatively assessed and compared with the turbulence effect.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51376001,51006006,51420105008 and 51376014)the National Basic Research Program of China("973"Project)(Grant Nos.2012CB720205,2014CB046405)+2 种基金the Aeronautical Science Foundation of China(Grant No.2012ZB51014)the Beijing Higher Education Young Elite Teacher Projectthe Fundamental Research Funds for the Central Universities
文摘The average-passage equation system(APES)provides a rigorous framework to account for the deterministic unsteady effects by the so-called deterministic correlations(DC),which include both deterministic stress correlations(DCS)and deterministic total enthalpy correlations(DCH).These correlations should be modeled to close the system of equations.In this paper,the distribution of DC in a transonic centrifugal compressor is presented,and its relative importance is revealed.The assumption made by Adamczyk that the pure unsteady fluctuation is significantly smaller than the spatial fluctuation is verified at the impeller-diffuser interface.The decomposition of DCH is also discussed to determine its two different physical mechanisms.Finally,the transport equations in terms of DCS in cylindrical coordinates are derived,and the terms are evaluated to determine the ones that are necessary to model.All these analyses significantly contribute to our model development for DC in centrifugal compressors.
文摘Numerical simulation on the unsteady flow in a centrifugal compressor isperformed, and compared with the experimental data. The influence of the impeller-diffuserinteraction on the flow-fields is discussed, and the reasons for the losses are also explored.Results show that qualitative and quite fair quantitative agreements are achieved between thepredicted and measured flowfields. The influence of the impeller wake on the convexity surface ofdiffuser is great. The potential repercussion of the diffuser on the suction surface of the impelleris much larger than on the pressure surface. Effect of the unsteady interaction is strongest in theradial gap. The unsteady flow itself may compensate for the loss generated in stage, and the stageefficiency is inversely proportional to the entropy production.
基金supported by the National Natural Science Foundation of China(Grant Nos.51339005,51379174 and 51279160)the Doctoral Fund of Ministry of Education of China(Grant No.20126118130002)
文摘The strong interaction in a radial pump due to the relative movement between the impeller and the diffuser may excite not only strong pressure fluctuations but also velocity fluctuations. In this paper, the laser Doppler velocimetry （LDV） technique is successfully applied to measure the periodic flow field in a radial diffuser pump with low-specific speed, in order to investigate the velocity fluctuations caused by the impeller-diffuser interactions both in the impeller and diffuser regions. The velocity fluctuations in the impeller region are quantitatively examined at different radial positions, and the flow structure at the radial gap between two flow components is analyzed at different relative positions. In addition, the downstream effect on the diffuser flow is quantitatively and qualitatively assessed and compared with the turbulence effect.
