Carlos M. López

Determination of flame emissivity in hydrocarbon pool fires using infrared thermography

A methodology is proposed for the determination of flame emissivity in hydrocarbon pool fires using infrared thermography. Experiments on gasoline and diesel oil pool fires with diameters of 0.13, 0.18 and 0.5 m were carried out, determining the flame emissivity for these types of fires in transition regime and turbulent regime. Also analysed was the evolution of the flame emissivity depending on the pool diameter, and a new correlation for the estimation of the emissivity depending on the above mentioned diameter was obtained.

Structural Diagnosis of a Concrete Dam with Cracking and High Nonrecoverable Displacements

AbstractExpansions in concrete dams may be caused by chemical or physical sources; however, in certain occasions the evidences observed in the dam may not be attributed to a single cause. Mequinenza is an example of a concrete dam affected by expansions and high nonrecoverable displacements that cannot be explained by the most frequent pathologies. This paper presents new hypotheses that could justify such behavior by assuming the superposition of a global phenomenon of water induced expansion in concrete in the entire dam and a localized effect consisting in the opening of cracks in the construction joints located in one of the blocks. This is validated by conducting numerical analyses through 2D finite element models that consider the nonlinear behavior of the construction joints and use zero-thickness interface elements to simulate the potential cracking planes in the dam. The results confirmed the diagnosis proposed and the capability of the model to reproduce the behavior of the dam, revealing the si...

Multiaxial behavior of concrete: A mesomechanical approach

ABSTRACT Interface elements for discrete fracture plus meso-level geometric representation are emerging as a powerful tool for the modeling of the behavior of heterogeneous materials such as concrete. The group of mechanics of materials at ETSECCPB has been developing such tools in which meso-geometry is generated numerically via Voronoi/Delaunay approach, and all lines in the FE mesh are considered as potential crack lines with traction-separation constitutive models based on principles of non-linear fracture mechanics. Results of mechanical analysis turn out very realistic, both mesoscopically (distributed microcrack, coalescence, localization) and macroscopically (average stress-strain curves for specimen). On-going extensions aim at modeling diffusion-driven and coupled phenomena such as drying shrinkage.

Constrained-size torque maximization in SynRM machines by means of genetic algorithms

Synchronous Reluctance Motors have always been an alternative to more mainstream machines such as the Permanent Magnet Synchronous Motor, but until recently they have not found their right place in industrial applications. This progressing adoption begins with the replacement of the current solutions, but this presents the design challenge of finding a surrogate which conforms to the specifications for a given application. In order to overcome this challenge, an evolutionary design methodology for SynRM is presented. The proposed approach uses a set of design constraints to maximize the mechanical power of the motor taking into account the specified rated speed. Since the calculation of the torque of the motor is critical, an iterative method for the evaluation of iron losses has been introduced. Finally, the proposed approach is validated by means of FEM simulation and the calculation of the efficiency map of the results.

Sensorless control of five phase PMSM based on extended Kalman filter

This paper deals with the realization of a sensorless five phase permanent magnet synchronous motor (PMSM) drive based on extended Kalman filter (EKF). The vector control for five phase AC machine is applied on dq1dq3 rotor reference planes and structure of the observer is extracted on the fixed stator reference frames of the first and third harmonics. The zero sequence component may also be incorporated in the state vector in order to facilitate fault tolerant operation.

Rotor of synchronous reluctance motor optimization by means reluctance network and genetic algorithm

An optimal design for a rotor of SynRM is proposed on this paper. The inductances of the machine computed in dq-axes allow determining machine performance and the motor behavior. High magnetic saturation on this kind of motor increases the difficulty of inductance calculation. Hence, the finite element analysis is currently used to design and optimize SynRM, from the first instance. This method usually requires a high amount of computational time and resources. For this reason, the reluctance network here proposed is a good alternative to consider for designing these motors, because it is a fast and good method to obtain the inductances of the SynRM. Therefore, an optimal design avoiding FEA is proposed on this paper using the reluctance network to calculate the dq-axes motor inductances.

New SynRM design approach based on behaviour maps analysis

A novel motor design methodology and optimization is proposed, which is applied to a SRM. It greatly reduces the finite element analysis use. A multi physics study is realized in order to couple the thermal, magnetic and electric motor analysis. Then, the information obtained with this study allows creating different behaviors maps in order to evaluate the motor in all operating area. With the joule and iron losses, the thermal network obtains a temperature map for each current and angular speed. Then, the electric model uses the parameters obtained on reluctances network and the phase resistance variation obtained on thermal lumped parameter. Finally, the optimal motor obtained is validated on FEA. To sum up, the motor design is obtained using multi physics analysis taking into account different operating points, i.e. it is a range operation optimization. In addition, reducing FEA computation time is achieved with the methodology proposed.

Dynamic nonlinear reluctance network analysis of five phase outer rotor BLDC machine

This paper presents a dynamic reluctance network (RN) magnetic equivalent circuit (MEC) analysis of a 55/52-pole five phase outer rotor brushless direct current (BLDC) motor. Winding distribution, stator slotting and iron saturation is included in the model. With this analysis the dynamic characteristics of the tested machine can be calculated. Back EMF and cogging torque responses are compared with the ones obtained from the finite element model (FEM) under no load and load conditions. The computation time of the RN network is significantly low with respect to the FEM analysis. The experimental setup results turn to be in very close matching to those provided by the elaborated models.

Free Expansion Tests for ASR at the Level of a Single Aggregate-Matrix Interface: Experimental Results and Numerical Modelling

As part of an on-going research project, a model being developed to simulate ASR in concrete is described. The formulation consists of the three main diffusion/reaction field equations for the concentrations of Alkali, Calcium and Silicate ions in the pore solution, complemented by a number of evolution equations for the local ingredients involved (e.g. local concentration of reactive silica, local availability of portlandite, etc.).

Recent developments in durability mesomechanics of concrete, including cracking via interface elements

The mesomechanical model for concrete previously developed for purely mechanical actions, is used as the basis for coupled durability mechanics calculations. Until now, the phenomena studied include drying shrinkage, external sulfate attack and mechanical effects of high temperatures. On-going work is focusing on alkali-silica reaction (ASR). From the chemical viewpoint, ASR is represented with a three-field diffusion-reaction chemical model, which is shown to qualitatively and quantitatively reproduce some experimental measurements of sandwich-type specimens subject to standardized accelerated ASR tests. The model developed includes the recently identified role of Calcium in this type of expansive reactions.