A new model of fluid flow to determine pressure balance characteristics

Some projects such as the EUROMET project 463 have underlined the lack of agreement between experimental measurements and calculations by the finite element method (FEM), used to determine the piston fall rate of a high-pressure balance used in primary standards. This is significant because the piston fall rate is an essential parameter to characterize experimentally the mean gap between the piston and the cylinder and to determine the effective area (A p) at each pressure (p) point. By improving the method used to estimate the piston fall rate it is possible to improve the determination of the gap, the effective area and consequently the pressure distortion coefficient. One possible cause of the lack of agreement between the calculated and measured piston fall rates could be inappropriate modelling of the fluid flow. In fact, the former quasi-1D Stokes model assimilates the gap between the piston and the cylinder as formed by two parallel walls, which is an approximation. In addition, the velocity of the piston wall was neglected. In order to evaluate the influence of this model, the equations of the fluid flow are modified and are presented in this paper. Equations that were defined in a parallel-plane model are defined in an annular gap model. In addition to this, corrections due to the velocity of the piston wall are inserted. This research work is applied on a Desgranges et Huot DH 7594 piston-cylinder unit of PTB with a pressure up to 1 GPa, in the continuity of the EUROMET project 463 in order to quantify the influence of each correction that has been inserted in the new equations. This is carried out using the FEM. This analysis will allow us to evaluate the improvement of our knowledge of the behaviour of piston gauges and consequently to better evaluate the uncertainties due to the models.Laboratoire National d'Essais-LN

Numerical investigation of the real and ideal gap profiles in the calculation of the pressure distortion coefficient and piston fall rate of an LNE 200 MPa pressure balance

This paper aims to investigate, by means of numerical simulation, the effect of gap profiles on the calculation of the pressure distortion coefficient (λ) and the piston fall rate (vf) of two piston-cylinder units used in a Laboratoire National de Métrologie et d'Essais (LNE) 200 MPa pressure balance. The ideal mean gap width between the piston and the cylinder was obtained after measuring the piston fall rate at a low pressure, while the piston radius was obtained from the cross-float experiments at a low pressure. The real gap width was obtained from dimensional measurements by measuring the diameter and straightness of the piston and the cylinder. The piston and cylinder radial distortions were calculated using the finite element method. The pressure distribution in the gap was calculated on the basis of the Navier-Stokes equation for Newtonian viscous flow. The results such as pressure distributions, radial distortions, the pressure distortion coefficient and the piston fall rate were presented for the free-deformation operating mode of the assemblies. The calculation resulted in ideal and real gap profiles indicating that the average pressure distortion coefficient was in good agreement within 0.017 × 10-6 MPa-1 and the calculations of piston fall rate depended on the gap profile especially at the inlet and outlet zones of the engagement length.Laboratoire National de Métrologie et d'Essai

La orientación académica y profesional en la ESO. Propuestas de acción.

Castellà: Al terminar 4º ESO el estudiante tiene que tomar una decisión importante en su vida, que tiene que ver con su futuro profesional, y se encuentra ante la disyuntiva de no saber por cual via optar (Bachillerato, CFGM, PQPI ...) El TFM que se presenta analiza cuales son algunas de las causas que conllevan a esta inseguridad, y propone vías para solucionarlas, incidiendo en el trabajo conjunto que deben realizar centro educativo-familia-alumno/a, se trata de hacer partícipes a cada uno del papel que juega en el proceso de Orientación Académica y Profesional. Propone como parte del PAT, unas acciones que irían desde 2º ESO hasta 4º ESO, con el objetivo de acompañar al estudiantado en el proceso de Orientación, expone además dos proyectos realizados en otros institutos que demuestran que es posible vincular al estudiante con el funcionamiento de una actividad laboral, con el objetivo claro de saber insitu lo que sería desarrollar una actividad profesional, a través de sus propias experiencias. Muestra además algunos ejemplos prácticos gestionados por el Departamento de Tecnología del instituto de prácticas, talleres que ayudan a que el alumno/a tenga una visión de lo que son profesiones asociadas a la Ingeniería, en estos casos Ingeniería Química, Ingeniería Informática, Diseñador Informático, entre otras. Existen factores que influyen en la desición final del estudiante, hay que hacerles saber que la decisión final es de ellos, y que la familia, los amigos, los profesores pueden aconsejar, pero si ellos tienen todos los elementos necesarios para tomar la decisión tienen que hacer lo que realmente sientan, porque es su futuro, y si hay alguna equivocación por el camino, que sean conscientes que el sistema educativo también brinda la posibilidad de cambios, porque es un sistema flexible

Forage Production and Nutritional Quality of Angleton climacuna (Dichanthium annulatum-Forssk-Stapf) for Hay, in La Dorada (Caldas)

This study was made on the Rancho Claro Farm, municipality of Doradas (Caldas). The aim was to determine the effects of cutting age on forage production and nutritional quality of angleton climacuna (Dichanthium annulatum) used for hay production. The study was made in previously chosen grassland; 21 lots of 100 m2 were prepared, and the cutting ages were set at random (40, 50, 60, 70, 80, 90, and 100 days). A completely randomized design was used with three replications per treatment. The age effect on production and quality was analyzed through analysis of variance and the Tukey´s test. Regression analysis and the Pearson test were made to determine correlation. Forage production was observed to vary between 5.8 and 23.6 T Ha-1 of FM. The highest protein value was observed 40 days later (7.9%), and it was higher than 5% until the 70th day. The dry matter (DM) percent and neutral detergent fiber (NDF) increased with age; the highest contents were observed after 80 days. The crude energy (CE) values were similar in all the ages. Quality decreased with age, but forage production increased. It was concluded that forage production and quality can be determined at any age, provided that height and forage production values per m2 are known at initial growth stages