循环流化床中糠醛渣与煤混燃特性的试验研究

在炉膛尺寸为150 mm×150 mm×2 500 mm的循环流化床燃烧试验台上进行糠醛渣与煤的混燃试验,研究其燃烧特性、尾部飞灰及烟气排放特性。研究表明:糠醛渣掺混质量比例为10%-50%的混合燃料在循环流化床中均可稳定燃烧;随着糠醛渣的掺混比例增加,炉膛上部温度升高,尾部飞灰含碳量下降,而颗粒排放浓度升高;随着流化风速增加,炉膛上部温度升高。密相区的温度升高,CO排放浓度下降,SO2、NOx排放浓度上升;糠醛渣的掺混比例增加,CO排放浓度上升,SO2、NOx排放浓度下降。     

稀释合成气微混合燃料喷射燃烧火焰特性研究

研究了耦合CO2稀释和微混合燃料喷射燃烧的火焰特性.结果表明:耦合CO2稀释和微混合燃料喷射燃烧是一种降低合成气扩散火焰NOx生成量的有效途径;实验范围内排放的NOx质量浓度一般低于2mg/m3,排放的CO质量浓度低于10mg/m3,排放的CO质量浓度随火焰热功率的增大而降低;燃烧器出口温度、壁面温度和喷嘴出口温度等均随火焰热功率的增大而升高.     

煤与生物质混烧时NO_x排放特性的实验研究

叙述了将稻壳、麦秆、松木屑3种生物质,分别与阳泉煤掺烧时,不同掺混比与过量空气系数对NOx排放规律的影响。指出,在低含O2量区,无论单煤还是混合燃料,NOx浓度均随烟气中的含O2量增加而增大;不同燃料NOx浓度增长速度的快慢,随烟气中的含O2量增加有所不同;在高含O2量区,混合燃料NOx的排放量随烟气中含O2量的增加而降低;生物质与煤掺混对NOx排放规律的影响不明显,燃烧过程中NOx的排放受生物质本身的含N量、煤种以及燃烧方式的影响较大。     

共轨柴油机燃用煤直接液化柴油的燃烧与排放特性

在电控共轨柴油机上,试验研究了煤直接液化柴油(DDCL)、石化柴油及二者混合燃料的燃烧和排放特性.结果表明,与石化柴油相比,DDCL燃烧始点晚,预混合燃烧强,但在大平均有效压力时不明显.DDCL混合一定比例的石化柴油后燃烧始点接近于石化柴油.随DDCL掺混比例增加,在小平均有效压力时的NOx、CO和HC排放增加较显著,而碳烟降低.对于颗粒物排放,纯DDCL较石化柴油略高,而石化柴油掺混小比例DDCL时颗粒物排放降低.     

PODE掺混和喷油参数对柴油机燃烧排放特性影响

在一台增压4缸直喷柴油机上开展了不同聚甲基二甲醚(PODE)掺混比例和喷油参数对柴油机燃烧和排放特性影响的试验.测试燃料包括纯柴油(PD0)、两种柴油/PODE混合燃料分别为PD20(PODE体积分数为20%)和PD30(PODE体积分数为30%).结果表明:随着喷油时刻的推迟,3种燃料缸内压力峰值降低,放热率峰值增加,燃油消耗率增加,热效率下降,CO和HC排放增加,NOx排放减小,颗粒物质量浓度降低,数量浓度先降低后升高;随喷油压力的增加,3种燃料缸内压力和放热率峰值增加,CO和HC排放减小,NOx排放增加,颗粒物数浓度和质量浓度下降.喷油时刻推迟和喷油压力增加都会使PD0的烟度排放明显减少,但对PD20和PD30的烟度排放影响比较小.随着PODE比例增加,热效率提高,但燃油消耗率上升,CO、HC和烟度排放下降,NOx排放小幅增加,颗粒物数浓度和质量浓度显著降低.     

燃料理化特性对柴油机低温燃烧过程及排放特性的影响

在一台单缸柴油机上,通过柴油掺混20%的正庚烷、正庚烷与异辛烷混合物以及异辛烷与40%正庚烷(体积分数),研究燃料组分、沸点和十六烷值等理化特性对柴油机传统燃烧和低温燃烧影响机理.结果表明,不同十六烷值燃料在高比例EGR下对滞燃期影响更显著;随掺混燃料十六烷值降低,碳烟排放降低;在20%掺混比下混合燃料沸点、黏度等物理特性和燃料组分等化学特性改变对燃烧和碳烟排放影响较小.与20%正庚烷掺混相比,低沸点、低黏度燃料在更高掺混比(40%)下对碳烟排放的降低作用变得明显.大比例EGR低温燃烧下,THC排放明显升高,其中甲烷占总碳氢比例达60%;NO2对整体NOx排放影响很小.在20%掺混比下,燃料理化特性的改变对THC、不同成分HC、CO和NOx排放影响很小;在40%正庚烷掺混比例下,芳香烃排放降低,NOx及NO2排放较柴油升高.     

柴油机燃用混合替代燃料的燃烧与排放特性

将生物柴油和F-T柴油(F-T diesel)进行掺混,并将其混合燃料应用于4100QBZL柴油机上.在未对原机做任何改动的情况下,研究了该机燃用不同体积配比混合燃料时的燃烧特性及NOx和碳烟排放性能.研究表明,与0#柴油相比,该机的预混燃烧放热峰值降低、扩散燃烧放热峰值升高、燃烧更柔和;NOx排放随着生物柴油掺混比例的增大而升高;碳烟排放显著下降,较0#柴油的降低幅度高达37%;低比例的混合燃料对NOx排放和碳烟排放的trade-off关系有明显改善.生物柴油与F-T柴油混合燃料宜在较低的生物柴油掺混比例范围内使用.     

掺混比例和喷射定时对二甲醚-乙醇发动机燃烧和排放的影响

在一台电控共轨发动机上,试验研究了乙醇掺混比例和喷射定时对二甲醚-乙醇混合燃料燃烧及排放的影响。结果表明:随乙醇比例的增加,滞燃期延长,燃烧持续期缩短,最大压力升高率上升。随喷射推迟,滞燃期延长,燃烧相位延后,燃烧持续期在纯二甲醚时延长,而在掺混乙醇时则先延长后缩短,最大压力升高率先下降后上升。掺混乙醇和推迟喷射使预混燃烧比例增加。随喷射推迟,混合燃料的排气温度升高,喷射推迟到上止点后,排气温度随乙醇比例的增加而升高,排气温度高,则废气能量高,增压器增压比大,进气流量大,导致缸内压缩压力升高。在上止点前喷射时,掺混乙醇能使HC和CO排放保持在较低范围的同时,一定程度降低NO_x排放,掺混15%的乙醇较纯二甲醚最大降低约11%NO_x排放。随推迟喷射,NO_x排放降低,最大降幅达52%,在过分推迟燃料喷射时,因热效率低,循环喷射量增加,含15%乙醇混合燃料的NO_x排放会高于纯二甲醚。HC和CO排放随喷射推迟而升高,且升高幅度增大。     

柴油机掺烧DMM的燃烧和排放性能影响研究

研究了柴油掺混不同比例二甲氧基甲烷(0～50%DMM)对柴油机燃烧和排放性能的影响.结果表明,在发动机燃油和燃烧系统不作变动的条件下,随着二甲氧基甲烷在柴油中添加比例的增加,排气烟度逐步下降,有效燃油消耗率有所增加,但折算成当量柴油的有效燃油消耗率降低,热效率增加.同一工况下,发动机排气碳烟和CO排放随二甲氧基甲烷的加入而降低,NOx则无明显的上升,HC排放随着二甲氧基甲烷的增加略有增加.混合燃料的放热规律与纯柴油相比预混燃烧量增加,扩散燃烧速率加快,发动机最高燃烧压力、放热率偏高.柴油掺混30%DMM的混合燃料能够取得较好的燃油经济性和排放水平.     

旋流对同轴富氧扩散燃烧NOx排放的影响

对30%～40%的氧浓度下甲烷富氧空气同轴扩散燃烧的火焰形态、可见火焰高度、燃烧特性以及NOx排放进行了实验测量,研究了旋流数对NOx排放控制的影响.结果显示,随着旋流数的增加,火焰高度略有升高,火焰发光由白色逐渐变为橙黄色;最高火焰温度逐渐降低,温度分布也变得平坦;NOx排放指数随旋流数的增加而降低,氧浓度越高,其下降幅度越大.保持其他条件不变,增加氧化剂流速可以增强旋流对燃烧特性及NOx排放的影响.     

A framework for stochastic estimation of electric vehicle charging behavior for risk assessment of distribution networks

Power systems are being transformed to enhance the sustainability. This paper contributes to the knowledge regarding the operational process of future power networks by developing a realistic and stochastic charging model of electric vehicles (EVs). Large-scale integration of EVs into residential distribution networks (RDNs) is an evolving issue of paramount significance for utility operators. Unbalanced voltages prevent effective and reliable operation of RDNs. Diversified EV loads require a stochastic approach to predict EVs charging demand, consequently, a probabilistic model is developed to account several realistic aspects comprising charging time, battery capacity, driving mileage, state-of-charge, traveling frequency, charging power, and time-of-use mechanism under peak and off-peak charging strategies. An attempt is made to examine risks associated with RDNs by applying a stochastic model of EVs charging pattern. The output of EV stochastic model obtained from Monte-Carlo simulations is utilized to evaluate the power quality parameters of RDNs. The equipment capability of RDNs must be evaluated to determine the potential overloads. Performance specifications of RDNs including voltage unbalance factor, voltage behavior, domestic transformer limits and feeder losses are assessed in context to EV charging scenarios with various charging power levels at different penetration levels. Moreover, the impact assessment of EVs on RDNs is found to majorly rely on the type and location of a power network.     

Effect of corrosion inhibitors on hydrogen uptake by Al from NaOH solution

Corrosion rate, hydrogen permeation rate (hydrogen uptake) and stress corrosion cracking of Al were studied in NaOH solutions, pure and with the addition of H₃BO₃, EDTA, KMnO₄ and As₂O₃. The presence of the studied species in electrolyte and the implantation of Al surface with B⁺ ions inhibited corrosion. Hydrogen uptake was found to be promoted or inhibited by means of studied species, depending on the method of their introduction into the base solution and on the applied polarization. The observed different influence of corrosion inhibitors on the hydrogen uptake was associated with the different chemical composition and structure (revealed by XPS analysis) of the surface films, formed on Al under the various conditions. Under similar polarization conditions, the presence of H₃BO₃ in the base solution similarly affected the hydrogen uptake by Al and the susceptibility to stress corrosion cracking of the metal.     

Energy management strategy of Supercapacitor/Fuel Cell energy storage devices for vehicle applications

This paper addresses the management of a Fuel Cell (FC) – Supercapacitor (SC) hybrid power source for Electric Vehicle (EV) applications. The FC presents the main energy source and it is sustained with SCs energy storages in order to increase the FC source lifespan by mitigating harmful current transients. For this aim, the reported work proposes a Grey Wolf Optimizer (GWO) for an efficient power management of the studied hybrid power system. The key idea of the proposed approach is to incorporate the benefit of the GWO in terms of fast optimization and convergence accuracy, in order to achieve efficient energy sources exploitation and provide the desired driving performances. Simulations and experimental results verify the validity of the proposed management algorithm.     

Development of hybrid photovoltaic-fuel cell system for stand-alone application

In this paper we present firstly the different hybrid systems with fuel cell. Then, the study is given with a hybrid fuel cell–photovoltaic generator. The role of this system is the production of electricity without interruption in remote areas. It consists generally of a photovoltaic generator (PV), an alkaline water electrolyzer, a storage gas tank, a proton exchange membrane fuel cell (PEMFC), and power conditioning units (PCU) to manage the system operation of the hybrid system. Different topologies are competing for an optimal design of the hybrid photovoltaic–electrolyzer–fuel cell system. The studied system is proposed. PV subsystem work as a primary source, converting solar irradiation into electricity that is given to a DC bus. The second working subsystem is the electrolyzer which produces hydrogen and oxygen from water as a result of an electrochemical process. When there is an excess of solar generation available, the electrolyzer is turned on to begin producing hydrogen which is sent to a storage tank. The produced hydrogen is used by the third working subsystem (the fuel cell stack) which produces electrical energy to supply the DC bus. The modelisation of the global system is given and the obtained results are presented and discussed.     

A methodology for the performance evaluation of an experimental desiccant cooling system

An experimental investigation was conducted in an open cycle desiccant cooling system (DCS) operating on the ventilation mode in the laboratory site [M. Yıldırım, An experimental investigation on heat and mass transfer in a desiccant cooling system, PhD thesis, Gaziantep University, Turkey (2002). [1]]. Although the operation of DCS is presumably affected by the design of primary components of rotary regenerator (RR) and desiccant wheel (DW) the methodology used in the analysis of experimental data is presented in this paper to set a different approach for the performance evaluation of similar systems.

The rotational speeds of RR and DW (N_RR and N_DW), air mass flow rate (m_a) in process and regeneration lines, and the regeneration temperature (T_R) were defined as operation parameters. Meanwhile coefficient of performance (COP) and cooling capacity (CC) of the system were called as the performance parameters. The system operation with a variety of experimental conditions resulted in an extensive data set covering the ranges of N_RR, N_DW, m_a and T_R as 5 rpm ≤ N_RR ≤ 20 rpm, 0.1 rpm ≤ N_DW ≤ 0.4 rpm, 0.05 kg/s ≤ m_a ≤ 0.139 kg/s and 60 °C ≤ T_R ≤ 90 °C, respectively. The interactive influence of the operation parameters was determined through the realization of the psychrometric cycle in deviation from an ideal cycle. A dimensional analysis based on a trial and error procedure was followed to determine the functional relationship of COP and CC.

The proposed correlations between COP and CC and the introduced system performance parameter (PP) were determined to be a sole function of m_a independent of N_RR, N_DW and T_R in their covered ranges.     

Designing and modelling of the asymptotic perturbed extremum seeking control scheme for tracking the global extreme

This paper presents the designing and modeling of the Asymptotic Perturbed Extremum Seeking Control (aPESC) scheme that is capable to locate and track the Global Extremes on the multimodal patterns. The multimodal patterns may appear on power generated by a photovoltaic (PV) array under Partial Shading Conditions (PSCs), but also on net power generated by a Fuel Cell (FC) system. The proposed aPESC scheme uses a scanning technique to determine the GMPP on different multimodal patterns based on two components of the searching signal: (1) the scanning signal locates the LMPP by sweeping the PV pattern based on a asymptotic dither modulated by the first harmonic of the PV power and controlled by the dither gain (k₂); (2) the tracking signal finds and tracks accurately the GMPP based on similar loop used in PESC schemes proposed in the literature that is controlled by the loop gain (k₁). These tuning parameters are designed based on the averaged model of this aPESC scheme. Also, the averaged scheme and local averaged loop of the aPESCH1 scheme are used to estimate the searching gradient and analyze the closed ESC loop stability. The design methodology is tested on generic multimodal patterns and then is validated considering a PV system and a FC system.     

In-situ hydrogen peroxide synthesis with environmental applications in bioelectrochemical systems: A state-of-the-art review

Hydrogen peroxide (H₂O₂) is a versatile, eco-friendly, strong oxidizing chemical with numerous industrial applications. It is found that bioelectrochemical system (BES) is a promising technology for H₂O₂ biosynthesis including microbial fuel cell (MFC) and microbial electrolysis cell (MEC), generally. Since first discovery of H₂O₂ production in BES in 2009, a growing community of researchers payed attention to on-site H₂O₂ production and environmental applications based on BESs. In this review, we discussed the state-of-the-art development, performance and environmental applications of H₂O₂-BES in detail. The H₂O₂-BES has been getting more and more energy-saving even turning “waste” into wealth completely without other energy input. Moreover, coupling the H₂O₂-BESs with Fenton and ultraviolet/visible light is extensively employed for environmental applications, ranging from dye decolorization, metal deposition, emerging contaminants, real wastewater and primary sludge treatment in lab-scale. However, the pilot- or industrial-scale applications of BESs are challenging enough in environmental remediation up to now.     

Characterisation tools development for PEM electrolysers

Electrochemical impedance spectroscopy (EIS), current interrupt (CI) and current mapping (CM) were investigated as in-situ characterisation tools for PEM electrolysers. A 25 cm² cell with titanium anode and carbon cathode plates were utilised in this study. A commercial MEA consisting of 1 mg IrO₂/cm² on the anode and 0.3 mg Pt/cm² on the cathode was used. The electrocatalyst was deposited on Nafion^® membranes. The electrochemical losses in a PEM electrolyser namely: activation, ohmic and mass transfer losses were identified using EIS and CI and both the advantages and disadvantages of the methods were discussed. The current distribution over the membrane electrode assembly (MEA) at different current densities was measured using the current mapping method. It is also shown that under the given experimental conditions the current density decreases along the serpentine flow field.     

Review of synergistic photo-thermo-catalysis: Mechanisms,materials and applications

Solar energy is potentially the most promising type of renewable energy for large-scale utilization in the future, thus maximizing the use of solar energy has long been long pursued. Photo-thermo-catalysis (PTC) has presented a novel strategy that could utilize the full-spectrum sunlight to stimulate the synergy between photocatalysis (PC) and thermocatalysis (TC), which not only achieves high utilization efficiency of solar energy but also minimizes the energy consumption compared to sole PC and TC. This review strives to give a comprehensive overview of major advances of PTC. It starts with the fundamental mechanisms of PTC categorized by either heating mode (local and global) or photo-thermal synergic mode (thermal-assisted photocatalysis, photo-assisted thermocatalysis, photo-driven thermocatalysis and photo-thermal co-catalysis). Then, various photo-thermal materials are illustrated, including metals, semiconductors, carbon materials, etc. After that, we focus on the diverse applications of PTC, specifically in the fields of energy (CO₂ reduction and H₂ evolution), environment (VOCs and 4-NP degradations) and organic synthesis (Suzuki coupling and cyclocondensation reactions). Special emphasis is placed on the synergism of photo and thermal effect that leads to enhanced catalytic performances in PTC. Finally, the challenges and perspectives of PTC are discussed. We hope this review could shed some light on the fundamental mechanisms of PTC reactions and serve as a clearer guidance for synergistically high-efficient solar energy utilization systems in the future.     

Optimal placement of PMUs for the smart grid implementation in Indian power grid—A case study

Efficient utilization of energy resources is essential for a developing country like India. The concept of smart grid (SG) can provide a highly reliable power system with optimized utilization of available resources. The present Indian power grid requires revolutionary changes to meet the growing demands and to make the grid smarter and reliable. One of the important requirements for SG is the instantaneous monitoring of the voltage, current and power flows at all buses in the grid. The traditional monitoring system cannot satisfy this requirement since they are based on nonlinear power flow equations. Synchro-phasor-measurement devices like phasor measurement units (PMUs) can measure the phasor values of voltages at installed buses. Consequently, the currents passing through all branches connected to that bus can be computed. Since the voltage phasor values at the neighboring buses of a bus containing the PMU can be estimated using Ohm’s law, it is redundant to install PMUs at all the buses in a power grid for its complete observability. This paper proposes the optimal geographical locations for the PMUs in southern region Indian power grid for the implementation of SG, using Integer Linear Programming. The proposed optimal geographical locations for PMU placement can be a stepping stone for the implementation of SG in India.