Optimization of an axial fan for air cooled condensers

We report on the low noise optimization of an axial fan specifically designed for the cooling of CSP power plants. The duty point presents an uncommon combination of a load coefficient of 0.11, a flow coefficient of 0.23 and a static efficiency ηstat > 0.6. Calculated fan Reynolds number is equal to Re = 2.85 x 107. Here we present a process used to optimize and numerically verify the fan performance. The optimization of the blade was carried out with a Python code through a brute-force-search algorithm. Using this approach the chord and pitch distributions of the original blade are varied under geometrical constraints, generating a population of over 24000 different possible individuals. Each individual was then tested using an axisymmetric Python code. The software is based on a blade element axisymmetric principle whereby the rotor blade is divided into a number of streamlines. For each of these streamlines, relationships for velocity and pressure are derived from conservation laws for mass, tangential momentum and energy of incompressible flows. The final geometry was eventually chosen among the individuals with the maximum efficiency. The final design performance was then validated through with a CFD simulation. The simulation was carried out using a RANS approach, with the cubic k -  low Reynolds turbulence closure of Lien et al. The numerical simulation was able to verify the air performance of the fan and was used to derive blade-to-blade distributions of design parameters such as flow deviation, velocity components, specific work and diffusion factor of the optimized blade. All the computations were performed in OpenFoam, an open source C++- based CFD library. This work was carried out under MinWaterCSP project, funded by EU H2020 programme

Nanotribological characterization of industrial Polytetrafluorethylene-based coatings by atomic force microscopy

We present the result of a systematic study of the tribological properties of industrial Polytetrafluorethylene (PTFE)-based coatings carried out with an atomic force microscope. A new characterization protocol allowed the reliable and quantitative assessment of the friction coefficient and adhesion forces at the sub-micrometer scale even for highly corrugated industrial samples. We have studied and compared PTFE coatings charged with different additives in dry and humid environment. The influence of additives and humidity on the friction coefficient and on adhesion forces has been investigated using standard silicon nitride tips as sliders in the low-load regime.Comment: to be published in Thin Solid Films 18 pages, 2 tables, 3 figure

La actividad sísmica en la Sierra Chica de Zonda antes y después del Dique de Ullum

La construcción del Dique de Ullum en la Provincia de San Juan ofrece a los sismólogos una nueva oportunidad para investigar el problema de la Sismicidad Inducida. La suerte quiso que el embalse cayera dentro del área de una red de siete estaciones sismológicas de alta sensibilidad. La ubicación de la presa está en una quebrada de la Sierra Chica de Zonda, a unos 12 km al oeste de la ciudad de San Juan. La Sierra es reconocida como zona sísmicamente muy activa. El primero de abril de 1978 se empezó a estudiar los sismos que se producían dentro de un radio no mayor de 60 km a partir del dique. El llenado del embalse empezó el 28 de diciembre de 1979 y el 12 de diciembre de 1980 el agua alcanzó el umbral del vertedero. El embalse se mantuvo lleno hasta el 20 de marzo de 1981. Durante 21 meses, con el dique vacío, se registraron 119 sismos; mientras que durante los 15 meses del período del llenado y con el dique lleno se registraron 140 sismos. Pero ha sucedido que el 24 de enero de 1980 y el 18 de abril del mismo año, cuando todavía había muy poca agua en el embalse, se produjeron dos fuertes sismos en la Sierra Chica de Zonda, a unos 20 kilómetros al sud del embalse. Ambos fueron seguidos de réplicas que aumentaron notablemente la frecuencia de los sismos. En opinión de los autores, el embalse no ha intervenido en la generación de los dos fuertes sismos y se habrían producido igualmente sin el embalse. Como resultado final no se observa que, aún con el embalse lleno, se modifique la sismicidad natural de la zona.The construction of the Ullum Dam in the Province of San Juan provides, seismologists with a new opportunity to conduct research on the problem of Induced Seismicity. Fortunately, the dam was located within the area covered by seven high sensibility seismologic stations network. The dam is located in the Sierra Chica de Zonda valley, about 12 km, to the West of San Juan City. The Sierra is considered to be a very active seismical area. On April 1st, 1978 a study on the seisms that took place within 60 km from the dam, was started. The filling of the dam started on December 28th, 1979, and the water reached the spillway threshold on December 12th,1980. The dam remained full until March 20th, 1981. During 21 months, period in which the dam remained empty, 119 seisms were recorded, while during the 15 months, corresponding to the period when it was full, 140 seisms were recorded. But, on January 24th, and April 18th, 1980,when there was still very little water in the dam, two strong seisms took place at the Sierra Chica de Zonda at about 20 km South of the dam. Both seisms were followed by aftershocks that increased significantly their frecuency. In the authors opinion, the dam has had no influence in the generation of the two strong earthquakes wich could have taken place, even if the dam had no been built. We can conclude that there is no clear evidence indicating that, even with the dam filled up, the seismic nature of the area has been modified.Asociación Argentina de Geofísicos y Geodesta

Las variaciones de cotas del terremoto de Caucete (San Juan, 23 de noviembre de 1977) y su relación con las anomalías gravimétricas

Gracias a la oportuna coincidencia de que se realizaran, al este de la ciudad de.San Juan, nivelaciones de alta precisión y un relevamiento gravimétrico, en la misma zona que fue luego la zona epicentral del fuerte terremoto de Caucete (23 de noviembre de 1977), ha permitido verificar varios resultados de importancia geodinámica. Los más notables son los siguientes: (a) El fuerte levantamiento del cerro Pie de Palo (1,20 m aprox.) que produjo el terremoto, ya se venía manifestando anteriormente. En efecto, entre 1938 y 1967 el levantamiento del cerro con respecto a su base occidental era de unos 4 cm; este levantamiento llega a 6 cm en 1976, o sea un año antes del terremoto. Finalmente se verificó que después del sismo, entre mayo 1978 y abril 1980, el levantamiento continúa y crece unos 9 cm más. (b) El relevamiento gravimétrico realizado a lo largo de la misma línea sobre la cual se efectuaron las nivelaciones, mostró que en correspondencia con el cerro Pie de Palo existía una Anomalía de Aire Libre positiva de varios miligales respecto de los valores existentes a ambos lados del cerro. El hecho de que el cerro se encuentre en su proceso de levantamiento demostraría que el valor de la anomalía de Aire Libre también seguiría creciendo.High precisión levellings and a gravimetric survey perfomed, to the East of San Juan City in the same area that was later the epicentral area of the strong Caucete earthquake (November 23rd, 1977),made it possible to verify several results of geodynamic importance. The most remarkable are the following: (a) The strong uplift of the Pie de Palo Mount (1.20 m approximately), which caused the earthquake, had been previously shown. In fact, between 1938 and 1967, that uplift with respect to its western base was of about 4 cm, and it reached 6 cm in 1976, i.e. a year before the earthquake. Finally, it was verified that after the earthquake, between May 1978 and April 1980, the uplift continued and grew about 9 cm more, (b) The gravimetric survey carried out along the same line on which the levellings were performed, showed that in correspondence with the Pie de Palo Mount there was a positive Free Air Anomaly of several miligals with relation to the existing values at both sides of the mount. The fact that the mount is undergoing an uplifting process would show that the value of the Free Air Anomaly would also keep on growing.Asociación Argentina de Geofísicos y Geodesta

Linear coupling of modes in 2D radially stratified astrophysical discs

We investigate mode coupling in a two dimensional compressible disc with radial stratification and differential rotation. We employ the global radial scaling of linear perturbations and study the linear modes in the local shearing sheet approximation. We employ a three-mode formalism and study the vorticity (W), entropy (S) and compressional (P) modes and their coupling properties. The system exhibits asymmetric three-mode coupling: these include mutual coupling of S and P-modes, S and W-modes, and asymmetric coupling between the W and P-modes. P-mode perturbations are able to generate potential vorticity through indirect three-mode coupling. This process indicates that compressional perturbations can lead to the development of vortical structures and influence the dynamics of radially stratified hydrodynamic accretion and protoplanetary discs.Comment: 10 pages, 10 figures, MNRAS (accepted

Influence of oxidant agent on syngas composition: gasification of hazelnut shells through an updraft reactor

Thermophysical properties of engineering fluids have proven in the past to be essential for the design of physical and chemical processing and reaction equipment in the chemical, metallurgical, and allied industries, as they influence directly the design parameters and performance of plant units in the of, for example, heat exchangers, distillation columns, phase separation, and reactors. In the energy field, the search for the optimization of existing and alternative fuels, either using neutral or ionic fluids, is an actual research and application topic, both for new applications and the sustainable development of old technologies. One of the most important drawbacks in the industrial use of thermophysical property data is the common discrepancies in available data, measured with different methods, different samples, and questionable quality assessment. Measuring accurately the thermal conductivity of fluids has been a very successful task since the late 1970s due to the efforts of several schools in Europe, Japan, and the United States. However, the application of the most accurate techniques to several systems with technological importance, like ionic liquids, nanofluids, and molten salts, has not been made in the last ten years in a correct fashion, generating highly inaccurate data, which do not reflect the real physical situation. It is the purpose of this paper to review critically the best available techniques for the measurement of thermal conductivity of fluids, with special emphasis on transient methods and their application to ionic liquids, nanofluids, and molten salts

Propulsion Health Management System Development for Affordable and Reliable Operation of Space Exploration Systems

The constraints of future Exploration Missions will require unique integrated system health management capabilities throughout the mission. An ambitious launch schedule, human-rating requirements, long quiescent periods, limited human access for repair or replacement, and long communication delays, all require an integrated approach to health management that can span distinct, yet interdependent vehicle subsystems, anticipate failure states, provide autonomous remediation and support the Exploration Mission from beginning to end. Propulsion is a critical part of any space exploration mission, and monitoring the health of the propulsion system is an integral part of assuring mission safety and success. Health management is a somewhat ubiquitous technology that encompasses a large spectrum of physical components and logical processes. For this reason, it is essential to develop a systematic plan for propulsion health management system development. This paper provides a high-level perspective of propulsion health management systems, and describes a logical approach for the future planning and early development that are crucial to planned space exploration programs. It also presents an overall approach, or roadmap, for propulsion health management system development and a discussion of the associated roadblocks and challenges

Swirling astrophysical flows - efficient amplifiers of Alfven waves

We show that a helical shear flow of a magnetized plasma may serve as an efficient amplifier of Alfven waves. We find that even when the flow is purely ejectional (i.e., when no rotation is present) Alfven waves are amplified through the transient, shear-induced, algebraic amplification process. Series of transient amplifications, taking place sequentially along the flow, may result in a cascade amplification of these waves. However, when a flow is swirling or helical (i.e., some rotation is imposed on the plasma motion), Alfven waves become subject to new, much more powerful shear instabilities. In this case, depending on the type of differential rotation, both usual and parametric instabilities may appear. We claim that these phenomena may lead to the generation of large amplitude Alfven waves and the mechanism may account for the appearance of such waves in the solar atmosphere, in accretion-ejecion flows and in accretion columns. These processes may also serve as an important initial (linear and nonmodal) phase in the ultimate subcritical transition to MHD Alfvenic turbulence in various kinds of astrophysical shear flows.Comment: 12 pages, 11 figures, accepted for publication (25-11-02) in Astronomy and Astrophysic

Immobilization, stabilization and patterning techniques for enzyme based sensor systems.

Sandia National Laboratories has recently opened the Chemical and Radiation Detection Laboratory (CRDL) in Livermore CA to address the detection needs of a variety of government agencies (e.g., Department of Energy, Environmental Protection Agency, Department of Agriculture) as well as provide a fertile environment for the cooperative development of new industrial technologies. This laboratory consolidates a variety of existing chemical and radiation detection efforts and enables Sandia to expand into the novel area of biochemically based sensors. One aspect of this biosensor effort is further development and optimization of enzyme modified field effect transistors (EnFETs). Recent work has focused upon covalent attachment of enzymes to silicon dioxide and silicon nitride surfaces for EnFET fabrication. They are also investigating methods to pattern immobilized proteins; a critical component for development of array-based sensor systems. Novel enzyme stabilization procedures are key to patterning immobilized enzyme layers while maintaining enzyme activity. Results related to maximized enzyme loading, optimized enzyme activity and fluorescent imaging of patterned surfaces will be presented

Abrupt fault detection and isolation for gas turbine components based on a 1D convolutional neural network using time series data

The FDI step identifies the presence of a fault, its level, type, and possible location. Gas turbine gas-path fault detection and isolation can improve the availability and economy of gas turbine components. Data-driven FDI methods are studied in this paper. Some notable gas turbine FDI challenges include: insensitivity to operating conditions, robust separation of faults, noisy sensor readings and missing data, reliable fault detection in time-varying conditions, and the influence of performance gradual deterioration. For conventional ML methods, the problem with handling time series data is its volume and the associated computational complexity; therefore, the available information must be appropriately compressed via the transformation of high-dimensional data into a low-dimensional feature space with minimal loss of class separability. In order to improve the detection and isolation sensitivity, this paper develops a method for FDI based on CNNs. Work in this paper includes: (1) Defining the problem and assembling a dataset. (2) Preparing data for training, validation and test: data generation, feature engineering, data pre-processing, data formatting. (3) Building up the model. (4) Training and validating the model (evaluation protocol). (5) Optimizing: a. deciding the model size. b. regularizing the model by getting more training data, reducing the capacity of the network, adding weight regularization or adding dropout. c. tuning hyperparameters. (6) Evaluation