Neural Network Based Central Heating System Load Prediction and Constrained Control

A neural network (NN) based heating system load prediction and control scheme are proposed. Different from traditional physical principle based load calculation method, a multilayer NN is incorporated with selected input features and trained to predict the heating load as well as the desired supply water temperature in heating supply loop. In this manner, a complicated load calculation model can be replaced by simple but efficient data-driven scheme and the response time to outdoor temperature variation can be enhanced. Moreover, in order to handle the input and output constraints in valve opening degree control task to achieve desired supply water temperature, Barrier Lyapunov candidate function and axillary system technique are involved. An additional NN is employed to approximate the system transfer function with reliable accuracy. The stability of the system is guaranteed through rigorous mathematical analysis. The excellent performance of the novelly proposed control over traditional PID is demonstrated via extensive simulation study. A quantitative case study is also conducted to verify the flexibility and validity of proposed load prediction strategy

Experimental and Numerical Investigation on Effects of the Steam Ingestion on the Aerodynamic Stability of an Axial Compressor

In order to investigate the influence of steam ingestion on the aerodynamic stability of a two-stage low-speed axial-flow compressor, multiphase flow numerical simulation and experiment were carried out. The total pressure ratio and stall margin of the compressor was decreased under steam ingestion. When the compressor worked at 40% and 53% of the nominal speed, the stall margin decreased, respectively, by 1.5% and 6.3%. The ingested steam reduced the inlet Mach number and increased the thickness of the boundary layer on the suction surface of the blade. The low-speed region around the trailing edge of the blade was increased, and the flow separation region of the boundary layer on the suction surface of the blade was expanded; thus, the compressor was more likely to enter the stall state. The higher the rotational speed, the more significant the negative influence of steam ingestion on the compressor stall margin. The entropy and temperature of air were increased by steam. The heat transfer between steam and air was continuous in compressor passages. The entropy of the air in the later stage was higher than that in the first stage; consequently, the flow loss in the second stage was more serious. Under the combined action of steam ingestion and counter-rotating bulk swirl distortion, the compressor stability margin loss was more obvious. When the rotor speed was 40% and 53% of the nominal speed, the stall margin decreased by 6.3% and 12.64%, respectively

Efficient CO2 electroreduction on a solid oxide electrolysis cell with La0.6Sr0.4Co0.2Fe0.8O3-delta-Gd0.2Ce0.8O2-delta infiltrated electrode

Solid oxide electrolysis cells are promising electrochemical devices for converting CO2 to useful products with high efficiency and simultaneously storing renewable energy. We here report a cell infiltrated with La0.6Sr0.4Co0.2Fe0.8O3-delta-Gd0.2Ce0.8O2-delta composite on yttria-stabilized zirconia scaffold as cathode and anode for CO2 electroreduction. The cell delivers a current density of -1.01 A cm(-2) at 1.4 V and 800 degrees C, along with an CO production rate of 6.95 mL min(-1) cm(-2) and a Faraday efficiency of 98.8%. CO2 electroreduction on La0.6Sr0.4Co0.2Fe0.8O3-delta-Gd0.2Ce0.8O2-delta cathode passes through two charge transfer reactions, in which the second charge transfer reaction from the carbonate intermediate reduction to CO is the key rate-dtermining step. The cell also exhibits little performance degradation during a 220 h run under a current density of -0.20 A cm(-2) at 800 degrees C

Highly Active Ag-TiO2 Nanocomposite from Atom Deposition in Ethylenediamine-Complexing Silver Mirror Reaction

Ag-TiO2 nanocomposite consisting of Ag clusters on the surface of TiO2 nanocrystals has been prepared by an ethylenediamine-complexing silver mirror reaction, which employs ethylenediamine (C2H8N2) rather than ammonia as a complexing agent. In this synthesis, the reduction reaction is finely tuned by varying the C2H8N2/H2O volume ratio. With the C2H8N2/H2O volume ratio at 1:4, the reduction can proceed in a more controllable manner, and the emerging Ag atoms in solution directly deposit on TiO2 nanocrystal surfaces, while self-nucleation and growth of nuclei to large size of free-standing Ag nanoparticles cannot occur. The obtained Ag-TiO2 nanocomposite shows excellent catalytic activity for the reduction of p-nitrophenol (4-NP) into p-aminophenol (4-AP) by NaBH4

Electrochemical behaviors of infiltrated (La, Sr) MnO3 and Y2O3-ZrO2 nanocomposite layer

(La0.8Sr0.2)(0.9)MnO3-delta-Y0.15Zr0.85O1.93 (LSM-YSZ) nanocomposite layer is infiltrated into three different scaffolds of ion-conductive YSZ, ionic and electronic conductive LSM-YSZ composite and insulating Al2O3 and used as cathode for anode supported cells. The cell performance and impedance spectra analysis reveal that the LSM-YSZ nanocomposite layer shows considerable high ORR activity using its own electronic and ionic conducting network, however, the electrochemical performance seems to be constrained by its limited ionic and electronic conductivity. The construction of ionic conducting path using YSZ scaffold is more effective for raising electrochemical performance than the construction of both electronic and ionic conducting paths using LSM-YSZ composite scaffold. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

Highly active Ag clusters stabilized on TiO2 nanocrystals for catalytic reduction of p-nitrophenol

Ag/TiO2 nanocomposites comprising of Ag clusters on TiO2 nanocrystal surfaces are of great significance in catalysts and advanced functional materials. Herein a novel method to synthesize Ag/TiO2 nanocomposites with Ag clusters under 2 nm on TiO2 nanocrystal surfaces have been developed. The success of this method relies on a silver mirror reaction in toluene, which refers to the reduction of silver-dodecylamine complexes by acetaldehyde in the presence of mono-dispersed TiO2 nanocrystals. The prepared Ag/TiO2 nanocomposites have been characterized by FT-IR spectra, UV-vis absorption spectra, X-ray diffraction (XRD) analysis, ultra high resolution scanning electron microscope (Ultra-HRSEM), high resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectra (XPS). Catalytic activity of Ag/TiO2 nanocomposites is evaluated for the reduction of p-nitrophenol (4-NP) into p-aminophenol (4-AP) by NaBH4. Results demonstrate that Ag/TiO2 nanocomposites have shown an outstanding catalytic activity as well as a good stability in successive reduction of 4-NP. Noticeably, TOF of Ag/TiO2-0.75 nanocomposites obtained in this work is the highest among Ag based catalysts previously reported. (C) 2016 Elsevier B.V. All rights reserved

Size-controlled synthesis of silver nanoparticles from silver mirror reaction in toluene

Size-controlled silver nanoparticles (Ag NPs) with a size of 2-15 nm have been synthesised from silver (Ag) mirror reaction in toluene , which refers to reduction of Ag precursor (Ag-dodecylamine complexes solution) by acetaldehyde (CH3CHO) in the presence of oleic acid (OLA). In this synthesis, the size of Ag NPs was finely tuned by just varying the Ag precursor concentrations (c(Ag)). The addition of OLA can play an important role in stabilising the emerging Ag nuclei. With the OLA/Ag molar ratio at 3:1, the adsorption layer of enough OLA on the surface of the emerging Ag nuclei prevented the direct contact between Ag+ ions and Ag nuclei, and Ag nuclei grew up to their final size by the aggregation mechanism

The Reduction Process of a NiO/YSZ Anode for Intermediate Temperature Solid Oxide Fuel Cells

The reduction behavior of a sintered NiO/YSZ anode used for intermediate temperature solid oxide fuel cells was studied by hydrogen temperature-programmed reduction (H-2-TPR). The reduction process of the NiO/YSZ anode in the cell was in situ monitored by open circuit voltage (OCV) and electrochemical impedance spectroscopy (EIS). H-2-TPR results show that the higher sintering temperature of the NiO/YSZ anode results in a slower reduction of NiO to metallic Ni. However, when the sintering temperature is elevated to 1500 degrees C, the reduction of sintered NiO/YSZ anode powder instead becomes easier. The higher NiO content in the anode leads to the more rapid reduction of the corresponding anode powder. The above H2-TPR results can be attributed to the combined effects of the growth up of NiO particles and the interface separation between NiO and YSZ caused by the anode sintering. The variation of OCVs reveals that for the cells, the anode with higher NiO content has a slower reduction process, which can be ascribed to the retarding effect of excessive H2O produced during the initial reduction period. It was found from the EIS results that the 50% NiO/YSZ anode has a most stable reduction process, whereas for the cells with 30 % and 70 % NiO/YSZ anodes, both the polarization resistances gradually increase after experiencing an initial decrease for a short period. The cell polarization resistance with 30 % NiO/YSZ anode keeps no change any more after reduction for 600 min, whereas the cell polarization resistance with 70 % NiO/YSZ anode increases continuously

LSM-YSZ nano-composite cathode with YSZ interlayer for solid oxide fuel cells

Low temperature prepared (La-0.8 Sr-0.2)(0.9) MnO3-delta-Y-0.15 Zr-0.85 O-1.93 (LSM-YSZ) nano-composite cathode has high three-phase boundary (TPB) density and shows higher oxygen reduction reaction (ORR) activity than traditional LSM-YSZ cathode at reduced temperatures. But the weak connection between cathode and electrolyte due to low sintering temperature restrains the performance of LSM-YSZ nano-composite cathode. A YSZ interlayer, consisted of nanoparticles smaller than 10 nm, is introduced by spinning coating hydrolyzed YSZ sol solution on electrolyte and sintering at 800 degrees C. The thickness of the interlayer is about 150 nm. The YSZ interlayer intimately adheres to the electrolyte and shows obvious agglomeration with LSM-YSZ nano-composite cathode. The power densities of the cell with interlayer are 0.83, 0.46 and 0.21 W/cm 2 under 0.7 V at 80 0, 70 0 and 600 degrees C, respectively, which are 36%, 48% and 50% improved than that of original cell. The interlayer introduction slightly increases the ohmic resistance but significantly decreases the polarization resistance. The depressed high frequency arcs of impedance spectra suggest that the oxygen incorporation kinetics are enhanced at the boundary of YSZ interlayer and LSM-YSZ nanocomposite cathode, contributing to improved electrochemical performance of the cell with interlayer. (C) 2016Science Press and Dalian Institute of Chemical Physics,Chinese Academy of Sciences. Published by Elsevier B. V. and Science Press. All rights reserved