Neural Network for Balance of Plant SOFC-GT Actuator Control

This work aims to study the feasibility of using an online feedforward artificial neural network (ANN) to control various actuators in a hybrid fuel cell gas turbine (FC-GT) simulation plant. This unique facility known as Hybrid Performance, or HYPER, is housed at the US Department of Energy’s National Energy Technology Laboratory in Morgantown, WV. Using a cyber-physical approach, HYPER incorporates a high-fidelity FC model in software, which interacts with a gas turbine and corresponding balance of plant components in hardware, in real time. This methodology allows research of FC-GT operational issues as well as control application studies for such systems in a safe manner. An open loop perturbation of the FC model load current is used to retrieve target data from load bank and bypass airflow valve actuators which control turbine speed and FC cathode airflow respectively. The steady state FC anodic side fuel flow is also fed to a supervised ANN which learns the pattern of actuator response to the given FC perturbations. By mimicking the manually operated actuators, the FC solid temperature gradient is maintained within safe operating bounds. The feedforward ANN is useful for its simplicity and flexibility in controlling a variety of desired actuator responses based on input combinations. The benefits and drawbacks of using ANN’s are discussed, as well as suggestions for improvement.

Electrochemical Determination of Hydrogen Entry to HSLA Steel during Pickling

Pickling with hydrochloric acid is a standard method to clean steel surfaces before hot-dip galvanizing. When normal low strength steels are pickled, hydrogen formed in pickling reactions does not have any significant harmful effect on the mechanical properties of steel. However, in pickling of steels with higher strength, the penetration of hydrogen into the steel may cause severe damages. The effect of pickling of high-strength low-alloy (HSLA) steels was investigated using a cell construction based on the Devanathan-Stachurski method with modified anodic surface treatment and hydrogen production using acid. The penetration and the permeability of hydrogen were measured using an electrochemical cell with hydrochloric acid on the one side of the steel sample and a solution of NaOH on the other side. No protective coating, for example, palladium on the anodic side of the sample, is needed. The penetration rate of hydrogen into the steel and exit rate from the steel were lower for higher strength steel.

Tin electrodeposition from sulfate solution containing a benzimidazolone derivative

Tin electrodeposition in an acidic medium in the presence of N,N’-1,3-bis-[N-3-(6-deoxy-3-O-methylD-glucopyranose-6-yl)-2-oxobenzimidazol-1-yl)]-2-tetradecyloxypropane as an additive was investigated in this work. The adequate current density and the appropriate additive concentration were determined by gravimetric measurements. Chronopotentiometric curves showed that the presence of the additive caused an increase in the overpotential of tin reduction. The investigations by cyclic voltammetry technique revealed that, in the presence and in absence of the additive, there were two peaks, one in the cathodic side attributed to the reduction of Sn2+ and the other one in the anodic side assigned to the oxidation of tin previously formed during the cathodic scan. The surface morphology of the tin deposits was studied by scanning electron microscopy (SEM) and XRD.

Transient Analysis of Gas Distribution in the Anodic Flow Field in a Fuel Cell Stack

In a polymer electrolyte fuel cell (PEFC), the catalyst degradation on cathodic side is one of the fatal problems caused by mal-distributed hydrogen supply into each channel on active area in a fuel cell, especially in a fuel cell stack for automotive fuel cell systems which consist of several hundreds of fuel cells stacked. For example, before getting the fuel cell system started-up, the gas in all the anodic flow passage including channels in each fuel cell is occupied by air instead of hydrogen due to cross leak from cathodic side to anodic side through the membrane employed as an electrolyte. In this situation, if hydrogen is supplied partially or unevenly between cells to start up the system, a concentration interface of air and hydrogen will be made within a fuel cell. This causes a state of local cell within a single fuel cell and the catalyst degradation (carbon corrosion or Pt dissolution) occurs. In this paper, to avoid this catalyst degradation, the gas distribution is investigated with pressurized hydrogen supply into channels located on the hundreds stacked fuel cells statically filled with air initially. A transient computational fluid analysis was applied to the flow fields of anodic side which consist of channels on fuel cells, both distributing and collecting manifold connected to the fuel cells under parameters: 1) number of stacked fuel cells (i.e. manifold length), 2) the rate of pressure rising (Pa/sec.) which makes the gas flow velocity. A gas analysis experiment was also carried out for a validation with mass spectrometer taking gas sample from several points along the gas channels on alternative fuel cells which are made of transparent acrylic resin. The results show that the uniform distribution in concentration between cells and its profile within the channels along the flow direction are strongly affected by flow field formed within the distributing manifold located upstream of stacked plates with channels.

MGT/HTFC Hybrid System Emulator Test Rig: Experimental Investigation on the Anodic Recirculation System

The Thermochemical Power Group (TPG) of the University of Genoa designed and installed a complete hybrid system emulator test rig equipped with a 100 kW recuperated micro gas turbine, a modular cathodic vessel located between recuperator outlet and combustor inlet, and an anodic recirculation system based on the coupling of a single stage ejector with an anodic vessel. The layout of the system was carefully designed, considering the coupling between a planar SOFC stack and the 100 kW commercial machine installed at TPG laboratory. A particular pressurized hybrid system was studied to define the anodic side properties in terms of mass flow rates, pressures, and temperatures. In this work, this experimental facility is used to analyze the anodic ejector performance from fluid dynamic and thermal points of view. The attention is mainly focused on the recirculation factor value in steady-state conditions. For this reason, a wide experimental campaign was carried out to measure the behavior of this property in different operative conditions with the objective to avoid carbon deposition in the anodic circuit, in the reformer, and in the fuel cell stack.

Microstructure evolution during electromigration between Sn–9Zn solder and Cu

This study investigated the electromigration behavior between Cu and Sn–9Zn solder under a current density of 1.0 × 103 A/cm2 for up to 230 h. The experimental results indicated that Cu5Zn8 was formed at the interface between Cu and the cathode side of the Sn–9Zn solder as well as in the bulk near the anode. Consumption of Cu was also observed for the Cu plating on the cathode side and anodic side, but with less compound formation and Cu consumption at the anode. The intermetallic compound layer on the cathode side was always thicker than that on the anode side after the same current-stressing time. The effect of chemical potential overwhelms electromigration in inducing Zn diffusion when a counterflow of electrons and chemical potential gradient exists. Voids formed at the Cu5Zn8–solder interface inside the solder regardless of the direction of current flow.

Experimental Study of Concentration Polarization at a Microchannel-Nanochannel Interface

Recent advances in fabrication methods allow us to study and leverage the unique flow regimes offered by nano-scale fluidic channels, [1–3] and recent work suggests that the physics of microchannel/nanochannel interfaces present opportunities for novel methods of sample preconcentration and analysis. [4–6] In nanochannels, channel height is of the same order of the electric double layer (EDL) thickness, leading to a decreased electrical resistance relative to the fluidic resistance of the channel. More importantly, analyte molecules undergoing electrophoresis spend a significant amount of time within EDLs. This has a profound effect on the interfaces between micro- and nanochannels. In particular, for negatively charged walls and a nanochannel in series with two microchannels, the concentration of ions (of both signs) increases on the cathodic side of the nanochannel and decreases on the anodic side. This phenomenon is called concentration polarization (CP) or the exclusion enrichment effect. [4, 5] There is a dearth of basic studies of these phenomena and the coupling of electroosmotic flow with concentration polarization. We present experimental validation of a computational model which predicts the development of concentration polarization. Furthermore, we will show preliminary results demonstrating focusing and separation of analyte anions in the cathodic side microchannel. This focusing is due to a balance of advection and electrophoretic migration. Anionic analytes focus and separate according to electrophoretic mobility.

Transient Analysis of Solid Oxide Fuel Cell Hybrids: Part B — Anode Recirculation Model

The aim of this work is the transient analysis of hybrid systems based on high-temperature Solid Oxide Fuel Cells (SOFC). The cell models were presented and discussed in Part A of this work. In this part attention is focused on the anode recirculation system. In a SOFC hybrid system it is necessary to recirculate part of the exhaust gas in order to maintain a proper value for the Steam-To-Carbon Ratio and to support the reforming reactions. This is carried out with an ejector, which exploits the pressure energy of the fuel to recirculate part of the anodic exhausts to fuel cell anodic side. Initially, a “dynamic” stand-alone ejector model is presented and validated for the analysis of unsteady flows. Particular attention was paid to the effect of time variation in the mixture composition, creating a general model for the unsteady simulation of flows with variable composition. To analyze the whole anodic circuit the “dynamic” model was simplified to the “lumped volume” model, which, even if it cannot properly analyze supersonic flows and shock waves, considerably reduces calculation time. So, it is suitable for transient system simulations, generally longer than a few minutes. The “lumped volume” model has been tested with the “dynamic” model and it has been used for the anodic recirculation system time-dependent simulations.

Quantitative Three-Dimensional Characterization of the Morphology of Stressed and Electromigrated Aluminum Lines

The volumes of slit, edge, erosion and erosion/slit voids in stressed and electromigrated aluminum conductor lines were quantitatively determined with low resolution standard and high resolution enhanced tips by atomic force microscopy. These three-dimensional results were compared to semiquantitative determinations of void volumes extrapolated from two-dimensional backscattered scanning electron microscopy area determinations of the passivated aluminum conductor. After the passivation was removed by plasma etching, void volumes were also determined from two-dimensional scanning electron microscopy micrographs. The volumes of the nearest hillocks on the anodic side of the voids were quantitatively determined by atomic force microscopy, and these hillock volumes were determined to be independent of the respective void volumes.

Inflorescence and flower development in Costus scaber (Costaceae)

The inflorescence of Costus scaber terminates an erect axis of a sympodial rhizome system. Primary bracts are borne on the inflorescence in spiral monostichous phyllotaxy. One-flowered cincinni occur in the axils of these bracts. Each cincinnus consists of an axis bearing a terminal flower and a secondary bract on the anodic side of the flower. A tertiary bud forms in the axil of this bract but does not complete development. The inflorescence terminates by cessation of growth of the apex and precocious development of the primary bracts. Floral organs are formed sequentially beginning with the calyx, and continuing with the corolla and inner androecial whorl, outer androecial whorl, and gynoecium. All flower parts, except for the calyx, originate from a ring primordium. Regions of this primordium separate to form the corolla and inner androecial members. It was not possible to determine the sequence of androecial member formation. The labellum is composed of five androecial members, three from the outer whorl and two from the inner. The third member of the inner whorl forms the stamen and its petaloid appendage. The gynoecium forms from three conduplicate primordia. The margins of two of these primordia are the product of phyietic fusion.