Diseño de laboratorio para la evaluación de silenciadores "in situ"

Se ha realizado el diseño de un sistema que permite realizar ensayos de silenciadores “in situ”. Para evaluar el comportamiento del sistema de ensayo de silenciadores se procede a caracterizar los paneles acústicos que son la base del sistema. De los paneles empleados en el sistema, se determinará por diferencia del nivel de presión sonora, el aislamiento a ruido aéreo de los mismos, partiendo del promedio de las medidas obtenidas en la sala emisora de la cámara reverberante con el material instalado y en la sala receptora. Se realizan distintas medidas de los niveles de presión sonora en sala emisora de la cámara reverberante y en la receptora así como del tiempo de reverberación con los paneles instalados en el hueco existente en el elemento de separación vertical de la cámara. Una vez ensayados los paneles, se ha procedido a medir los niveles de presión sonora que se obtienen antes y después de la interposición de distintos silenciadores en el sistema diseñado con el propósito de disponer de un laboratorio de medida de la atenuación de silenciadores. Para ello, se procede a efectuar el montaje, en la puerta sencilla de la cámara reverberante, de los componentes del sistema diseñado y se realizan mediciones de la atenuación que proporciona la colocación de un silenciador en el sistema y su posterior sustitución por un conducto. La medición de la atenuación del nivel de presión sonora que producen los distintos silenciadores se realiza por pérdidas por inserción, siguiendo las directrices de la Norma UNE-ISO 11820 y por el método de conductos forrados como cálculo teórico. ABSTRACT. A system has been designed for testing silencers “in situ”. In first place, to evaluate the behavior of the system in the test of silencers, it has been proceeded to customize the acoustic panels that are the basis of the system. The attenuation sound of the panels used in the system will be determined by the difference of sound pressure level. It will be made through the average of the measurements obtained in the source room of the reverberant chamber, the average of the measurements obtained in the receiving room, as well as the reverberation time, with the material installed in the hole of the walls. Once the panels are tested, and with the purpose of having a laboratory to measure the attenuation of silencers, the sound pressure levels has been measured before and after inserting the different silencers in the designed system. To obtain these measures, the components of the system designed have been installed in the hollow of the single door of the reverberant chamber and then the sound pressure level has been measured with a silencers first and after with a duct instead of the silencer. The measurement of the attenuation of the sound pressure level produced by different silencers has been made by insertion loss, following the 11820 UNE-ISO, as well as theoretical calculation has been made by the method of duct lined.

Analytical Calculation of Stall-inception and Surge Points for an Axial-flow Compresor Rotor

Recently, a theoretical criterion to calculate the stability of an axial-flow compressor rotor has been presented in the scientific literature. This theoretical criterion was used for determining the locus of the stability line over the rotor map and for predicting the post-stall evolution of the constant-speed line of a rotor. The main objective of this paper is to improve the predictions of such a model. To do that, the paper proposes a different characterization of the characteristic azimuthal length and a calculation of the ratio of specific heats based on a polytropic exponent. Thanks to these new values, the model predicts two bifurcation points in the behaviour of the flow: the inception point of the instability and the surge point. Experimental data from a pure axial compressor are used to validate the model showing that the prediction of the flow coefficient at the surge point has an error inferior to 5%. For the rotor studied, the paper provides a quantitative and qualitative description of the inception of the instability and of the mechanism involved in the instable region of the compressor map. The paper also discusses the role of rotor efficiency in the position of the bifurcations and gives a sensitivity analysis of its position. Finally, it presents a discussion about how the model can explain the different behaviours exhibited by the same rotor when the flow coefficient is reduced

Use of Headed Reinforcement Bars in Contruction. A Theoretical Approach to Determine the Dimensions of Anchorage Plates and Experimental Tests on Knee Joints Subjected to a Closing Moment

In order to reduce costs and time while improving quality, durability and sustainability in structural concrete constructions, a widely used material nowadays, special care must be taken in some crucial phases of the project and execution, including the structure design and calculation, the dosage, dumping and curing of concrete: another important aspect is the proper design and execution of assembly plans and construction details. The framework, a name designating the whole reinforcement bars cage already assembled as shown in the drawings, can be made up of several components and implies higher or lower industrialization degree. The framework costs constitute about one third of the price per cubic meter placed in concrete works. The best solutions from all points of view are clearly those involving an easier processing to achieve the same goal, and consequently carrying a high degree of industrialization, meaning quality and safety in the work. This thesis aims to provide an indepth analysis of a relatively new type of anchoring by plate known as headed reinforcement bars, which can potentially replace standard or L-shaped hooks, improving the cleaning of construction details and enabling a faster, more flexible, and therefore a more economical assembly. A literature review on the topic and an overview of typical applications is provided, followed by some examples of specific applications in real projects. Since a strict theoretical formulation used to provide the design plate dimensions has not yet been put forward, an equation is proposed for the side-face blowout strength of the anchorage, based on the capacity of concrete to carry concentrated loads in cases in which no transverse reinforcement is provided. The correlation of the calculated ultimate load with experimental results available in the literature is given. Besides, the proposed formulation can be expanded to cases in which a certain development length is available: using a software for nonlinear finite element analysis oriented to the study of reinforced concrete, numerical tests on the bond-bearing interaction are performed. The thesis ends with a testing of eight corner joints subjected to a closing moment, held in the Structures Laboratory of the Polytechnic University of Madrid, aiming to check whether the design of such plates as stated is adequate for these elements and whether an element with plate-anchored reinforcement is equivalent to one with a traditional construction detail.