Papers by Emmanuel Fernandez Rodriguez
It is important to understand tidal stream turbine performance and flow field, if tidal energy is... more It is important to understand tidal stream turbine performance and flow field, if tidal energy is to advance. The operating condition of a tidal stream turbine with a supporting structure has a significant impact on its performance and wake recovery. The aim of this work is to provide an understanding of turbine submerged depth that governs the downstream wake structure and its recovery to the free-stream velocity profile. An experimentally validated numerical model, based on a computational fluid dynamics (CFD) tool, was present to obtain longitudinal, transverse and vertical velocity profiles. Wake characteristics measurements have been carried out in an open channel at Hohai University. The results indicate that varying the turbine proximity to the water surface introduces differential mass flow rate around the rotor that could make the wake persist differently downstream. CFD shows the same predicted wake recovery tendency with the experiments, and an agreement from CFD and experiments is good in the far-wake region. The results presented demonstrate that CFD is a good tool to simulate the performance of tidal turbines particularly in the far-wake region and that the turbine proximity to the water surface has an effect on the wake recovery.
En este artículo se presenta un análisis entre dos tipos de materiales, el silicón blanco comerci... more En este artículo se presenta un análisis entre dos tipos de materiales, el silicón blanco comercial común, y el silicón de alta temperatura QM 245. Estos silicones están siendo estudiados actualmente para una aplicación de sellos hidráulicos, en la cual se quiere comparar el tiempo de vida útil, para encontrar el material que presente una menor degradación. Para esto se tomaron dos muestras de cada material. Se realizó un análisis termogravimétrico (TGA) a las primeras muestras con un intervalo de 50°C a 700°C obteniendo una gráfica que representa el porcentaje de pérdida de masa. A las segundas muestras se les realizó un análisis dinámico mecánico (DMA) con un intervalo de-50°C a 90°C obteniendo como resultado el módulo de almacenamiento de las muestras. Palabras Clave: TGA, DMA. A B S T R A C T This article presents an analysis between two types of materials, the common commercial white silicone, and the high temperature silicone QM 245. These silicones are currently being studied for an application of hydraulic seals, in which we want to compare the time of useful life, to find the material that presents less degradation. For this, two samples of each material were taken. A thermogravimetric analysis (TGA) was performed on the first samples within a range of 50 ° C to 700 ° C, obtaining a graph that represents the percentage of mass loss. The second samples were subjected to a dynamic mechanical analysis (DMA) within a range of-50 ° C to 90 ° C, obtaining as a result the storage module of the samples. 1. Introducción Un sello hidráulico es un anillo de hule que tiene una función específica, esta es no dejar pasar flujo. Sella los componentes según la aplicación, por lo que hay diferentes tipos de sellos [1]. Algunos se utilizan en aplicaciones como pistones y cilindros. En calentadores solares se utiliza un sello de silicón para permitir el paso del agua entre los tubos de vacío y el tanque recolector sin fugas. El silicón es frecuentemente utilizado debido a su bajo costo, buenas propiedades mecánicas y facilidad en el proceso de manufactura. Se cuenta con un sistema de calefacción solar el cual se utiliza en una escuela de natación, y se ha observado que se somete a altas temperaturas, teniendo registros con una máxima de 96°C al interior del sistema. Los sellos que se utilizan se reemplazan constantemente al degradarse en dos meses debido a las condiciones extremas. En este artículo se hace un estudio comparativo de dos materiales que se usan para sellos hidráulicos, con el fin de resolver el desgaste prematuro de estos e implementar un nuevo sello, el cual será utilizado en sistemas de calefacción solar. Para el sistema del problema, se necesita un sello de gran resistencia a las condiciones ambientales, por lo que se propone como opción el silicón de alta temperatura QM 245. Existen estudios sobre hules de silicón cuando trabajan en condiciones de temperaturas oscilantes y con ambientes en los que se encuentran en contacto son sustancias ácidas, en los cuales se ha demostrado un aumento en la rigidez del material y una disminución en el peso. [2] Otro estudio con una diferente aplicación de silicones, en este caso para LEDs demuestra que el comportamiento es ISSN 2448-5551 MM 193 Derechos Reservados © 2018, SOMIM
Preliminary analysis is presented of the influence of support structure flexibility on the extrem... more Preliminary analysis is presented of the influence of support structure flexibility on the extreme values of thrust experienced by a tidal turbine due to both turbulent flow and opposing waves. A statistical analysis of experimental measurements of rotor thrust indicate that thrust with a probability of occurrence 1 in a 1000 (0.1%) is approx. 50% greater than mean thrust due to turbulent flow only. For waves with velocity amplitude of half the mean velocity, the 0.1% thrust increases to 100% greater than the mean thrust. Loading and surge response of a rotor plane supported by a flexible structure is subsequently predicted. The basis of this approach is a single degree of freedom model of the response of the rotor plane, in surge only. Excitation force is obtained by a BEM code and hydrodynamic damping based on published data for a porous disc [1]. Response is sensitive to the rotor plane damping coefficients employed but initial findings indicate dynamic response reduces 0.1% thrust due to waves by 15% relative to a rigid structure.
A series of experiments has been conducted to assess the magnitude of turbine loads due to waves ... more A series of experiments has been conducted to assess the magnitude of turbine loads due to waves relative to those due to turbulence only and to determine the characteristics of the flow incident to downstream turbine locations. The distribution of thrust force on a single rotor in turbulent flow is fitted to an extreme value distribution and the modification due to opposing waves determined. The flow-field downstream of a single turbine and a fence of five discs is also studied to inform the loading on downstream turbines.
The suitability of a blade element momentum method for predicting time-varying thrust due to both... more The suitability of a blade element momentum method for predicting time-varying thrust due to both steady flow and opposing waves is assessed by comparison to experimental measurements obtained at small geometric scale. A blade element model is developed and validated for steady flow against published data for both a 0.8 m diameter rotor [1] and a 0.27 m diameter rotor [2]. Time-variation of angular speed, thrust and power are obtained for uniform flow only and flow combined with opposing waves. Comparison is drawn between measured time-varying thrust and predicted time-varying thrust based on flow velocity measured at hub height and assumed quasi-steady over intervals up to one-tenth of a wave period. Blade Element Momentum Theory Blade Element Momentum (BEM) Theory is widely used to obtain the variation of power coefficient (C P) and axial thrust coefficient (C T) with t rbine s rotational speed (TSR). A turbine power curve is obtained by relating the lift and drag curves for each section of a blade to the net thrust and power developed by the rotor. Design software such as GH Bladed is widely used for both wind-and tidal stream turbine design. This approach has been shown to be suitable for prediction of performance of mean performance of tidal stream turbines [1, 2] although corrections for blockage may be required. There is less published information available concerning the suitability of this approach for prediction of time-varying thrust and power. This is particularly important for flows comprising both uniform flow and current for which there is uncertainty on the transient loads effects on the rotor. This research employs the BEM theory to predict in a quasi-steady state the t rbine s unsteady behaviour. Experimental Approach The experimental arrangement is as described in [2]. A rotor of diameter =0.27 m is supported on a strain gauged support structure and assisting or retarding torque applied by a custom dynamometer. Angular speed is obtained from an optical encoder. Torque is held constant in time at values of [0.0039-0.0156] N-m to attain tip-speed ratios over the range 4-6.5 in steady flow. The rotor is located at mid-depth and mid-span of a 5 m wide flume with water depth 0.45 m. The incident flow velocity, , is measured at hub height using a Nortek Vectrino+ ADV prior to rotor installation. All parameters are sampled at 200 Hz. The influence of oscillatory flow on the rotor performance is investigated by development of regular waves of 2 cm amplitude and frequency of 0.5 Hz opposing the mean flow. Mean axial velocity in the absence of waves is = 0.462 m/s. Axial velocity with waves varies from 0.66 to 0.23 m/s with a mean of u c+w = 0.442 m/s. Predicted and Measured Thrust Accuracy of the present BEM implementation is demonstrated by comparison to published predictions from [1] and [2] and to measurements due to steady flow (Figure 1). Comparison is drawn between measured and predicted thrust (F x,m and F x,p) assuming steady flow (averaged over dt = 120 s) and for time-varying flow (averaged over dt = 0.1 s). To facilitate comparison and because velocity measurements are not synchronized with thrust, the time-varying tip speed ratio (TSR) and thrust coefficient are normalized to the steady flow mean velocity for both measurements and predictions. From measurements: Eq.1 31
Time-varying thrust has been measured on a rotor in shallow turbulent flow at laboratory scale. T... more Time-varying thrust has been measured on a rotor in shallow turbulent flow at laboratory scale. The onset flow has a turbulence intensity of 12% at mid depth and a longitudinal turbulence length scale of half the depth, about 5 times the vertical scale, typical of shallow flows. The rotor is designed to have thrust and power coefficient variations with tip speed ratio close to that of a full-scale turbine. Three extreme probability distributions give similar thrust exceedance values with the Type 1 Pareto in mid range which gives 1:100, 1:1000 and 1:10 000 exceedance thrust forces of 1.38, 1.5 and 1.59 times the mean value. With opposing waves superimposed the extreme thrust distribution has a very similar distribution to the turbulent flow only. Exceedance forces are predicted by superposition of a drag force with drag coefficient of 2.0 based on the wave particle velocity only and with an unchanged mean thrust coefficient of 0.89. These values are relevant for the design of support structures for marine turbines.
Revista del Centro de Graduados e Investigacion. Instituto Tecnologico de Merida, 2019
We describe in this paper the results obtained through the research carried out to determine the ... more We describe in this paper the results obtained through the research carried out to determine the carbon footprint of the 12 Technological Institutes certified in the country's SGEn, using the records of the electrical energy consumption calculated through the Measurement, Report and Verification (MRV) methodology. The application of this research produced favorable results for the design of strategies aimed at reducing the generation of the carbon footprint volumes of these institutions
Dams are important water-resisting structures prone to failure, causing huge economic and environ... more Dams are important water-resisting structures prone to failure, causing huge economic and environmental losses. Traditionally, a dam failure is identified using the failure mode and effect analysis. This approach analyzes both the dam failure path (the specific effect chain of the failure mode) and the damage degree, by identifying and sorting the severity caused by the dam failure path. However, this analysis can be misleading since the relationship among the failure paths is not considered. To account for this, the DEMATEL method is used to modify the evaluation result of the severity of the failure consequence, caused by the dam failure path. Based on the fuzzy mathematics and VIKOR method, a dam failure path identification method is established, and then the dam failure paths are identified and sorted for a case study: gravity dam located at the junction of Yibin County (China). According to results, the two top initial failure paths were insufficient design of upstream anti-seepage (R6) or defective watertight screen and corrosion (R7).
Comprehensively evaluating satellite precipitation products (SPPs) for hydrological simulations o... more Comprehensively evaluating satellite precipitation products (SPPs) for hydrological simulations on watershed scales is necessary given that the quality of different SPPs varies remarkably in different regions.
Recently, the output of Computational Fluid Dynamic (CFD) prediction on tidal stream turbine syst... more Recently, the output of Computational Fluid Dynamic (CFD) prediction on tidal stream turbine systems has been receiving great attention owing to the vast and untapped tidal stream potential. For several years, many publications have documented the accuracy of CFD methods for steady flows, but not for unsteady flows. A challenging area persisting in the computational field is its dependence on large computing resources, and the unsteady nature of usual tidal streams. To overcome this problem, researchers have proposed modelling simpler, representative devices or combined CFD with alternative predictive methods. Nevertheless, the turbulent modelling has been a critical issue in the CFD methods and great effort has been devoted to the study of turbulence and wave effect on the wake and functioning of the turbine. The present paper is a review of CFD application on tidal stream turbine performance in both steady and unsteady flows. The performance of the turbine predicted by actuator and blade resolved methods, has been in accordance with laboratory observations. Findings of the wake have been both consistent and inconsistent with measurements, arising from interpretation of the blade force, fluid-solving method and onset flow model, and downstream range distance. With regards to arrays, preliminary work shows turbine arrangement can have profound effects in the onset flow, and in consequence, the performance of adjacent turbine rows. The results reported appear to support the wind similarity assumption, such as wake Gaussian velocity distributions and fluctuating turbine output in unsteady flows. Under the influence of surface waves, the wake recovers faster than steady flow condition due to the flow's convective acceleration, but the mean performance stays almost equal. The findings in this paper give a critical review and insight of important implications for future turbine research, such as experimental validation of the turbine prediction output in small and large arrays.
In this paper we evaluated the feasibility of energy generation by incineration of waste in Mexic... more In this paper we evaluated the feasibility of energy generation by incineration of waste in Mexico. The population of Mexico was split into six population-size classes, each one associated to a waste generation index. The total amount of waste and the lower calorific values were used to estimate the power and energy resulting from each size class. The economic feasibility was evaluated using the Levelized Cost of Energy (LCOE), Net Present Value (NPV) and Internal Rate of Return (IRR). For populations up to 3 million inhabitants the incineration of waste resulted in 58.9 MW. The total energy generation resulted in 11,681.64 GWh contributing to 4.3% of the national demand. The NPV and IRR showed negative values per lower sizes of population and the LCOE resulted in higher values than other energy sources. A sensitivity analysis was conducted, addressing specific elements of the analysis to show how the project can become economically feasible when adjusting investment, O&M and sales tariff. This research provides evidence on how the Waste-To-Energy (WTE) incineration industry is feasible in Mexico and provides significant benefits, not only by strengthening the renewable energy sector but also by significantly improving the waste management system.
The oxidation ditch (OD) plays an important role in wastewater treatment plants.
When sand particles are entrained into carrier flow, such as liquid, a strong interaction occurs ... more When sand particles are entrained into carrier flow, such as liquid, a strong interaction occurs with the surface of the metallic material, resulting in serious erosion damage. However, the effect of the physical properties of particles and materials on erosion characteristics has not been well studied. In this paper, the erosion-wear behavior of a rotating disc surface under the action of solid-liquid two-phase flow was studied by using the discrete particle model (DPM). The wear effects on the surface of sample due to particle diameter (d = 0.1 mm, d = 0.2 mm, d = 0.3 mm, d = 0.4 mm), particle volume fraction (C V = 2%, C V = 3%, C V = 4%, C V = 5%), and particle inlet velocity (v = 1.05 m/s, v = 2.05 m/s, v = 3.05 m/s, v = 4.05 m/s) were analyzed using representative values of operating conditions of rotating machines. The results show that the wear amount increases exponentially with the radius, whilst the maximum wear amount increases faster than the average wear amount with the particle volume fraction. The surface wear grows inversely with the particle diameter but slightly with the particle inlet velocity. A case study of stainless steel samples at different radius positions on the surface of rotating disc is carried out using a mixed velocity of sand and water of 2.05 m/s, an average particle size of 0.1 mm, and a concentration of C V = 2.5%. The experiments show the wear amount increases with the radius on the surface of the rotating disc, just as predicted by the numerical simulation. Two important findings emerge from the study: (1) the wear morphology of the specimen surface develops from two to three regions; (2) when the basal body is rotating at high speed, the wear degree is influenced more by the circumferential than particle inlet velocity. The wear morphology was observed by using a scanning electron microscope (SEM). It exhibited a mixture of fine and coarse scratches and pits, and the distribution of these varied according to the radial distance of the disc.
A multiobjective optimization technique based on the computational uid dynamics (CFD) simulations... more A multiobjective optimization technique based on the computational uid dynamics (CFD) simulations and the orthogonal test is proposed to reduce the pressure pulsation in this paper. ree levels of four well-known performance factors L 9 (3 4 ) were considered in the orthogonal test scheme: the number of blades, the blade setting angle, the hub ratio, and the distance between the blade and the guide vane. e evaluation indexes corresponded to the head, e ciency, shaft power, and pressure pulsation, respectively. An optimal con guration A 2 B 1 C 2 D 3 was obtained by comprehensive frequency analysis method, after intuitive and range analysis. In comparison with the nonoptimized model, the new design's head and e ciency increased by 17.8% and 4.26%, whilst the shaft power and the pressure pulsation coe cient reduced by 1.22% and 11%, respectively. Experiments conducted on the optimized pump were consistent with the CFD model. Six di erent rotational speed conditions in the optimal operating points were numerically calculated in order to explore the internal hydraulic characteristics of the optimized axial ow pump. It is veri ed that the comprehensive frequency analysis method based on the orthogonal test approach is e ective for the multiobjective optimization of the axial ow pump.
In non-design conditions, severe hydraulic instability can affect the stability of a pump station... more In non-design conditions, severe hydraulic instability can affect the stability of a pump station and even shorten its service life. A Francis pump station in the South-to-North Water Transfer Project was examined to carry out a numerical simulation of the entire flow passage using a bidirectional fluid-solid method for static and fatigue life. Due to the inlet setting, reverse power generation exhibited a more distorted flow pattern that resulted in higher energy loss than the pump condition. The radial force acting on the blades in reverse power generation was 39.1% higher. Runner stress was mainly concentrated at the leading edge and blade edge. The maximum stress in reverse power generation was 35.7 MPa, which was about 28.5% higher than in the pump condition. While the maximum deformation was 0.035 mm, almost 94.4% more severe than in the pump condition, mainly concentrated at the leading edge. Based on the fatigue analysis, a minimum safety factor obtained numerically was 8.238 in the pump condition and 6.343 in the reverse power condition, respectively. The safety factors satisfy the safety standard of the runner material and meet requirements of safety and stability in the reverse power generation condition.
Dam behavior is difficult to predict due to its complexity. At the same time, dam deformation beh... more Dam behavior is difficult to predict due to its complexity. At the same time, dam deformation behavior is vital to dam systems. Developing a precise prediction model of dam deformation from prototype data is still challenging but determinant in the structural safety assessment. In this paper, an artificial neural network (ANN), trained by the improved artificial fish swarm algorithm (IAFSA) and backpropagation algorithm (BP), is proposed for predicting the dam deformation. Initially, crossover operator is embedded into AFSA, which aims to enhance the performance. In light of the influence mechanism of many factors on dam deformation behavior, the hybrid (IAFSA and BP) model uses statistical input to obtain the optimal connection weights and threshold values of the neural network. e hybrid model integrates IAFSA's strong global searching ability and BP's strong local search ability. To avoid overfitting the training set data, a validation set is adopted to check the generalization capability. Subsequently, the obtained optimal parameters are applied to predict the dam deformation behavior. e hybrid model's preciseness is verified against the radial displacements of a pendulum in a concrete arch dam and simulations of four models: statistical model, BP-ANN optimized by genetic algorithm (GA), particle swarm optimization (PSO), and AFSA. Results demonstrate that the proposed model outperforms other models and may provide alarms for safety control.
When the pumping operation of pumped storage unit suffers from power outage, the hydraulic transi... more When the pumping operation of pumped storage unit suffers from power outage, the hydraulic transient poses a serious threat to the safe operation of the unit and its pressure pipeline system. For high-head pumped storage power station (PSPS), the water hammer pressure (WHP) and rotational speed rise ratio (RSRR) of each hydraulic unit will be increased during the pump outage condition. In order to limit the fluctuation of rotational speed and WHP in power-off condition, optimizing and choosing a reasonable guide vane closure scheme (GVCS) is an economic and efficient means to improve the dynamic characteristics of pumped storage unit. On the basis of the calculation model of the transition process of single tube-double unit type of a high-head PSPS, an optimization model of GVCS balancing WHP and RSRR objectives is established. Furthermore, the two-stage broken line and three-stage delayed GVCSs are applied to the pump outage condition, and the nondominated sorting genetic algorithm-II (NSGA-II) is introduced to calculate the optimal solution set under different water heads and different closure schemes. For four typical water heads, the multiobjective optimization results of the closure law show that the two-stage broken line law has a better Pareto front under high water head, while the three-stage delayed law has a better performance under low water head. Furthermore, through the results of transition process of typical schemes, the adaptability of GVCS and water head is analyzed. e method proposed in this paper can make the RSRR not more than − 0.89, and the three-stage delayed law can even make the RSRR only − 0.01. Methods of this paper provide a theoretical basis for optimum guide vane closure mode setting of PSPS.
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Papers by Emmanuel Fernandez Rodriguez