Soft computing based multi-objective optimization of Brayton cycle power plant with isothermal heat addition using evolutionary algorithm and decision making

An irreversible regenerative Brayton cycle model considering internal and external irreversibilities is developed in matrix laboratory (MATLAB) simulink environment and thermodynamic optimization based on finite time thermodynamic analysis along with multiple criteria is implemented. Evolutionary algorithms based on second version of non-dominated sorting genetic algorithm (NSGA-II) and multi-objective evolutionary algorithm based on decomposition (MOEA/D) are employed to optimize power output and thermal efficiency simultaneously where isobaric-side heat exchanger effectiveness (ε_H), isothermal-side effectiveness (ε_H1), sink-side effectiveness (ε_L), regenerator-side effectiveness (ε_R), and working medium temperature (T₅) are taken as design variables. The optimal values of aforementioned design variables are investigated. Pareto optimal frontiers between dual objectives are obtained and the final optimal values of power output and thermal efficiency are chosen via LINMAP, fuzzy Bellman–Zadeh, Shannon’s entropy and TOPSIS decision making approaches. The obtained results are compared and the best one is preferred. An improvement in thermal efficiency from 18.29% to 21.10% is reported. In addition to this, variations of different input parameters on the power output and thermal efficiency are conferred and presented graphically. With the goal of error investigation, the maximum and average errors for the obtained results are designed at last.     

Effects of CO addition on shock wave propagation,self-ignition,and flame development of high-pressure hydrogen release into air

In this study, an experimental investigation is conducted to study the effects of CO addition (0%–7.5% vol.) on the self-ignition of pressurized hydrogen leakage. The result shows that more CO addition significantly decreases the likelihood of self-ignition inside the tube and the formation of self-sustained jet flame outside the tube. This can be mostly explained by the reduction of leading shock intensity inside the tube. Furthermore, CO addition effectively inhibits the flame propagation and development inside the tube. For pure hydrogen, the ignited flame quickly develops an intense flame spanning the tube width and eventually form a jet flame in ambient air. However, the H₂–CO diffusion flame initiated approaching tube sidewall tends to propagate adjacent to the wall or be soon quenched with more CO addition. If the CO-weakened flame spouts to the tube exit, it may not survive the expansion at the tube exit and thus it is quenched.     

Low area/power decimal addition with carry-select correction and carry-select sum-digits

We improve a carry-select technique for decimal adders, where pairs of corrective carry-out bits for all decimal positions are computed in parallel. Selection is based on the corresponding positional carry-in bits, which are produced by a quaternary parallel prefix carry network. Carry-out bits select pairs of corrected or intact sum-digits to be later selected by actual carry-in bits at the end of addition process. Analytical evaluation and synthesis results for various hardware sharing architectures on binary, decimal, adders, and subtractors show lower area consumption and less power dissipation of the proposed designs at no additional latency, compared to previous works.     

Polar silicones: structure-dielectric properties relationship

A series of polar silicones was synthesized in order to compare their dielectric properties. Different substituents with high dipole moment (epoxy, pyridyl, aldehyde, cyano-, nitroazobenzene) were attached by hydrosilylation to a poly(dimethyl-methylhydro)siloxane. Thiol-ene addition on a dimethyl-methylvinyl siloxane copolymer with similar composition was also used for chemical modifications with chloro- or carboxy- derivatives. This approach allowed comparison of properties with emphasis on dielectric behavior measured in liquid state, as a preliminary step in design and preparation of materials suitable for dielectric elastomers. Although a relatively low content of polar groups was used (8%), permittivity values of 5.4 and even 7.4 were achieved (at 10 kHz), either due to the large dipole moment or to the presence of important amounts of moisture. The water sorption capacity of the polar silicones was investigated by dynamic vapor sorption, while structural parameters of model molecules were calculated, in order to correlate the dielectric properties with the polarity/hydrophilicity of the substituents to the silicone chain. A combined effect of the calculated dipole moment, molar polarizability, molar volume, and the measured water sorption capacity on dielectric permittivity was observed.     

Synthesis and application of nonionic polyacrylamide with controlled molecular weight for fracturing in low permeability oil reservoirs

Nonionic polyacrylamide (NPAM) with controlled molecular weight was successfully synthesized as a gel fracturing fluid by aqueous solution polymerization. The effects of the monomer concentration, initiator concentration, reaction time, feeding temperature and reaction temperature on the molecular weight were systematically investigated through single‐factor and orthogonal experiments. The NPAM molecular weight can be controlled by adjusting these factors. The decisive factor is the acrylamide concentration, whereas the initiator concentration and feeding temperature are secondary factors. These synthetic NPAMs can be crosslinked with zirconium acetate to produce a gel fracturing fluid for use in low permeability oil reservoirs. Gel fracturing fluids based on synthetic NPAMs have high shear resistance, low filtration performance, easy gel breaking performance, good proppant carrying capability and low core damage capability. By adjusting the NPAM or crosslinker concentrations, the gel fracturing fluid can be adapted for use in low permeability oil reservoirs for a wide temperature range (60–120°C). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41637.     

Al(OH)_3对双组分加成型液体硅橡胶热稳定性的影响

采用非等温热分析(TG)技术,在惰性气氛和5、15、20 K/min线性升温速率条件下,考察了不同Al(OH)3用量的双组分加成型液体硅橡胶的非等温热降解机制及反应动力学,采用Flynn-Wall-Ozawa(FWO)动力学模型对非等温动力学数据进行分析,并研究了热分解反应的表观活化能Ea。以表观活化能对转化率α作图的结果显示引入一定量的热稳定性添加剂可以大大提高液体硅橡胶的热稳定性。     

基于炉排炉的生活垃圾与污泥混烧技术

为了更深入地研究生活垃圾与污泥的混烧工艺技术,本文基于我公司的逆推往复式生活垃圾机械炉排炉,对生活垃圾与污泥混烧过程进行了研究。结果表明:时间、温度和湍流度是影响混合燃料燃烧的主要因素;工程应用中需根据现场条件和焚烧炉装置的特点等因素选择合理的污泥加入方式,并解决好炉排底部的漏渣问题;混烧污泥在一定程度上降低了燃烧效果和发电量,建议污泥混烧比例为10%~15%,并确保烟气在不低于850℃的条件下停留时间大于等于2 s;含水率超过80%和重金属含量过高的污泥不适于直接焚烧。生活垃圾和污泥混烧是可行的,为市政污泥的处理提供了一个很好的方向。     

On the influence of methanol addition on the performances of PEM fuel cells operated at subzero temperatures

The storage and the operation of proton exchange membrane fuel cells (PEM FCs) at subzero temperatures result in the ageing and degradation of membrane-electrode assemblies (MEAs). In this study, we investigated the effect of a freeze-thaw temperature cycles (from ambient down to ?80 °C) on various properties of PFSA membranes and on the performance level of MEAs. The beneficial effects resulting from the addition of methanol vapor to the hydrogen have been put into evidence. Small angle x-ray scattering (SAXS) data have been measured on membranes swollen with water and water-methanol mixtures, to identify possible microstructure differences. It was found that the addition of methanol tends to increase the ionic resistivity of the membranes but has a protective effect on the catalytic layers during the freeze-thaw cycles. The degradation rate of the catalytic layer was reduced by almost a factor of two as a result of optimal methanol addition.     

Kinetic analysis of the chemical effects of hydrogen addition on dimethyl ether flames

The chemical effects of hydrogen addition on premixed laminar low-pressure dimethyl ether flames were studied by kinetic analysis. The chemical effects of hydrogen addition on flame structures and mole fractions of major species, intermediate species and free radicals have been distinguished clearly from the dilution and thermal effects. The results show that the chemical effects of hydrogen addition cause the DME profile to move toward the upstream side and can suppress the production of acetylene and ethylene. The production of formaldehyde is promoted by the chemical effects of hydrogen addition but the dilution and thermal effects are more dominant which decrease the mole fraction of formaldehyde so that the overall effects make formaldehyde mole fraction decrease. The dominant effects of hydrogen addition on H, OH and O radicals are the chemical effects that make mole fractions of these radicals increase.