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Numerical analysis of external gear pumps including cavitation / D. del Campo in Transactions of the ASME . Journal of fluids engineering, Vol. 134 N° 8 (Août 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 8 (Août 2012) . - 12 p. Titre : Numerical analysis of external gear pumps including cavitation Type de document : texte imprimé Auteurs : D. del Campo, Auteur ; R. Castilla, Auteur ; G. A. Raush, Auteur Année de publication : 2012 Article en page(s) : 12 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : cavitation;  CFD;  gear  pumps;  volumetric  efficiency Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Hydraulic machines are faced with increasingly severe performance requirements. The need to design smaller and more powerful machines rotating at higher speeds in order to provide increasing efficiencies has to face a major limitation: cavitation. The problem is inherently three-dimensional, due to the axial clearances, the relief and circumferential grooves, and to the circular pipes through which the fluid enters and exits the pump. A simplified two-dimensional numerical approach by means of computational fluid dynamics (CFD) has been developed for studying the effect of cavitation in the volumetric efficiency of external gear pumps. The assumptions employed prevent from predicting realistic values of the volumetric efficiency, but show to be valid to understand the complex flow patterns that take place inside the pump and to study the influence of cavitation on volumetric efficiency. A method for simulating the contact between solid boundaries by imposing changes in viscosity has been developed. Experiments of unsteady cavitation in water and oil performed by other authors have been numerically reproduced using different cavitation models in order to select the most appropriate one and to adjust its parameters. The influence of the rotational speed of the pump has been analyzed. Cavitation in the suction chamber very effectively damps the water hammer associated to the sudden change of the contact point position at the end of the gearing cycle. At high rotational speeds, the volume of air becomes more stable, reducing the flow irregularity. When cavitation takes place at the meshing region downstream from the contact point, the volume of air that appears acts as a virtual second contact point, increasing the volumetric efficiency of the pump. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000008 [...] [article] Numerical analysis of external gear pumps including cavitation [texte imprimé] / D. del Campo, Auteur ; R. Castilla, Auteur ; G. A. Raush, Auteur . - 2012 . - 12 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 134 N° 8 (Août 2012) . - 12 p. Mots-clés : cavitation;  CFD;  gear  pumps;  volumetric  efficiency Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Hydraulic machines are faced with increasingly severe performance requirements. The need to design smaller and more powerful machines rotating at higher speeds in order to provide increasing efficiencies has to face a major limitation: cavitation. The problem is inherently three-dimensional, due to the axial clearances, the relief and circumferential grooves, and to the circular pipes through which the fluid enters and exits the pump. A simplified two-dimensional numerical approach by means of computational fluid dynamics (CFD) has been developed for studying the effect of cavitation in the volumetric efficiency of external gear pumps. The assumptions employed prevent from predicting realistic values of the volumetric efficiency, but show to be valid to understand the complex flow patterns that take place inside the pump and to study the influence of cavitation on volumetric efficiency. A method for simulating the contact between solid boundaries by imposing changes in viscosity has been developed. Experiments of unsteady cavitation in water and oil performed by other authors have been numerically reproduced using different cavitation models in order to select the most appropriate one and to adjust its parameters. The influence of the rotational speed of the pump has been analyzed. Cavitation in the suction chamber very effectively damps the water hammer associated to the sudden change of the contact point position at the end of the gearing cycle. At high rotational speeds, the volume of air becomes more stable, reducing the flow irregularity. When cavitation takes place at the meshing region downstream from the contact point, the volume of air that appears acts as a virtual second contact point, increasing the volumetric efficiency of the pump. DEWEY : 620.1 ISSN : 0098-2202 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JFEGA4000134000008 [...]

Numerical analysis of the shaft motion in the journal bearing of a gear pump / R. Castilla in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 132 N° 1 (Janvier 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 1 (Janvier 2010) . - 10 p. Titre : Numerical analysis of the shaft motion in the journal bearing of a gear pump Type de document : texte imprimé Auteurs : R. Castilla, Auteur ; M. Gutes, Auteur ; P. J. Gamez-Montero, Auteur Année de publication : 2010 Article en page(s) : 10 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Finite  element  analysis  Gears  Machine  bearings  Pumps  Runge-Kutta  methods  Shafts Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper describes a numerical analysis of the dynamics of the shaft in the journal bearing of a gear pump. The modulus and direction of the load is a function of the relative position of the gears, causing a precession motion around an equilibrium position. The mean load is the function of the working pressure of the gear pump. The numerical analysis presented in this paper combines the equation of motion of the journal-gear set, based on the linearization of the fluid film load, with calculation of the load due to the pressure distribution on the gears. The damping and stiffness coefficients for the motion equation are calculated with the distributions around the shaft of the pressure and its derivatives. These distributions are calculated from the Reynolds equations using an in-house 2D finite element code with quadrangular elements; the equation of motion is solved with a fifth-order Runge–Kutta scheme. The results provide the stabilized position of the shaft for certain conditions, and allow limitation of the working pressure and the angular velocity of the pump in order to minimize, or to avoid, metal-metal contact and consequent wear of material. The results are compared with experiments and previously reported numerical results. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000132000001 [...] [article] Numerical analysis of the shaft motion in the journal bearing of a gear pump [texte imprimé] / R. Castilla, Auteur ; M. Gutes, Auteur ; P. J. Gamez-Montero, Auteur . - 2010 . - 10 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 1 (Janvier 2010) . - 10 p. Mots-clés : Finite  element  analysis  Gears  Machine  bearings  Pumps  Runge-Kutta  methods  Shafts Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : This paper describes a numerical analysis of the dynamics of the shaft in the journal bearing of a gear pump. The modulus and direction of the load is a function of the relative position of the gears, causing a precession motion around an equilibrium position. The mean load is the function of the working pressure of the gear pump. The numerical analysis presented in this paper combines the equation of motion of the journal-gear set, based on the linearization of the fluid film load, with calculation of the load due to the pressure distribution on the gears. The damping and stiffness coefficients for the motion equation are calculated with the distributions around the shaft of the pressure and its derivatives. These distributions are calculated from the Reynolds equations using an in-house 2D finite element code with quadrangular elements; the equation of motion is solved with a fifth-order Runge–Kutta scheme. The results provide the stabilized position of the shaft for certain conditions, and allow limitation of the working pressure and the angular velocity of the pump in order to minimize, or to avoid, metal-metal contact and consequent wear of material. The results are compared with experiments and previously reported numerical results. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000132000001 [...]