加氢裂化装置高压空冷器风机的改造

某石化公司150×10^4t／a加氢裂化装置高压空冷器风机风量小,叶片和翼型存在缺陷．传动方式效率低,导致高压分离器温度上升,气相循环氢体积增大,相应增大了循环氢压缩机负荷,造成汽轮机蒸汽耗量增加,循环氢纯度降低,产品质量变差。对高压空冷器4台风机实施了改造：采用新型HY系列玻璃钢叶片替换TB型铝风机叶片．采用啮合传动型的同步带传动替换摩擦传动型的多楔带传动。与改造前相比,改造后风机全压从170Pa提高到200Pa,风量从36×10^4m^3／h提高到46×10^4m^3／h,平均风速从3．391m／s提高到3．875m／s;反应流出物的温降提高了5℃;汽轮机3．5MPa蒸汽消耗量每小时可节约0．6t;加氢裂化装置运行平稳。加工量从149．44t／h提高到164．75t／h。     

Approbation of an innovative method of pretreatment of dark fermentation feedstocks

According to the International Energy Agency, only a small part of the full potential of biomass energy is currently used in the world. The annual amount of agricultural waste in the Russian Federation is estimated at about 152 million tons, and the energy potential of animal waste is 201 PJ/year. Anaerobic digestion is an efficient method of converting organic waste into renewable energy sources. Previously, the positive effect of pretreatment of various organic feedstocks in vortex layer apparatus (VLA) on the characteristics of anaerobic digestion and energy efficiency was shown. Currently, there is a significant interest in the world in obtaining biohydrogen from organic waste using the dark fermentation (DF) process. During pretreatment in the VLA, the iron working bodies are abraded and iron particles are introduced into the feedstock of the DF reactor. This may have a positive effect on the production rate and yield of hydrogen, which has not been previously studied. This work is aimed at evaluating the possibility of using the VLA as a method for pretreatment of a dark fermentation feedstock for the intensification of biohydrogen production. To achieve this goal, an experimental setup was constructed. It consisted of a 45 L DF reactor, a VLA and a process control system to collect data on the DF process parameters every 5 min. At a hydraulic retention time in the DF reactor of 24 h and in the VLA of 30 s, the hydrogen content in the biogas increased from 51.1% to 52.2%. At the same time, the pH increased from 3.85 to 4.8–4.9, and the hydrogen production rate increased by 16% to 1.941 L/(L day). The hydrogen yield was 80.9 ml/g VS. Thus, pretreatment of the feedstock in VLA can be an effective way to intensify the DF process; however, further study of the VLA operating modes is required in order to optimize the concentrations of iron particles introduced into the feedstock for the most efficient continuous production of dark fermentative biohydrogen.     

Computational analysis of the feasibility of a micro-pulsejet

This paper investigates the feasibility of a 2-cm micro-pulsejet by numerically simulating the inviscid gas dynamic phenomena within the exhaust tube and comparing them with those for a pulsejet on the order of 50 cm in length. After initial combustion, the pressure wave propagates towards the exit and reflects back as a rarefaction wave, which generates a minimum pressure in the combustion chamber. This low pressure must be sufficient to open the reed valves to allow fresh reactants to enter. It is shown that for both large and micro-pulsejets, the minimum pressure is low enough. The characteristic operating frequency is found to be approximately inversely proportional to the pulsejet length. Estimation of the boundary layer thickness in the pulsejet shows that viscosity plays a very significant role in the micro-pulsejet and cannot be neglected.     

Modeling of thermal stresses and probability of survival of tubular SOFC

The temperature profile generated by a thermo-electro-chemical model was used to calculate the thermal stress distribution in a tubular solid oxide fuel cell (SOFC). The solid heat balances were calculated separately for each layer of the MEA (membrane electrode assembly) in order to detect the radial thermal gradients more precisely. It appeared that the electrolyte undergoes high tensile stresses at the ends of the cell in limited areas and that the anode is submitted to moderate tensile stresses. A simplified version of the widely used Weibull analysis was used to calculate the global probability of survival for the assessment of the risks related to both operating points and load changes. The cell at room temperature was considered and revealed as critical. As a general trend, the computed probabilities of survival were too low for the typical requirements for a commercial product. A sensitivity analysis showed a strong influence of the thermal expansion mismatch between the layers of the MEA on the probability of survival. The lack of knowledge on mechanical material properties as well as uncertainties about the phenomena occurring in the cell revealed itself as a limiting parameter for the simulation of thermal stresses.     

燃煤可吸入颗粒物声波团聚效果的实验研究和数值分析

1引言我国是燃煤大国,每年燃煤产生的一次和二次颗粒物数量巨大。排放到空气中的颗粒物不仅降低了大气的能见度,影响环境和气候,而且危害人体健康,使致病率和死亡率上升。可吸入颗粒物(<10μm)是目前我国城市大气环境的主要污染物,尤其是空气动力学直径小于2.5μm的颗粒物(PM2.     

Mechanism of indirect initiation of detonation

Based on the first-order Arrhenius kinetics of chemical reaction and hydrodynamics, we proposed a mechanism to interpret the physical process of detonation onset. In the proposed mechanism, all the movements of chemical mixture are described by the characteristic waves of hyperbolic system. Each wave in different manner contributes to the transition from deflagration to detonation. The triggered detonation is the result of interaction of the multiple waves, more accurately, is a direct result of the re-ignition in the gaseous explosive in the unreacted zone by the reaction-released energy that is transferred in the form of the characteristic wave. This mechanism provides a complete and theoretic explanation to “explosion in the explosion” observed in experiments. It associated with the traditional ignition theory may be used to build up the criterion for deflagration-to-detonation transition (DDT). The mechanism is further verified by our numerical solutions to the mathematic model.     

Investigation of the performance of a staggered configuration of tidal turbines using CFD

This paper investigates the influence of wake interaction and blockage on the performance of individual turbines in a staggered configuration in a tidal stream farm using the CFD based Immersed Body Force turbine modelling method. The inflow condition to each turbine is unknown in advance making it difficult to apply the correct loading to individual devices. In such cases, it is necessary to establish an appropriate range of operating points by varying the loading or body forces in order to understand the influence of wake interaction and blockage on the performance of the individual devices. The performance of the downstream turbines was heavily affected by the wake interaction from the upstream turbines, though there were accelerated regions within the farm which could be potentially used to increase the overall power extraction from the farm. Laterally closely packed turbines can improve the performance of those turbines due to the blockage effect, but this could also affect the performance of downstream turbines. Thus balancing both the effect of blockage and wake interaction continues to be a huge challenge for optimising the performance of devices in a tidal stream farm.     

Coordinated discharge of a collection of batteries

Collections of batteries are used to supply energy to a variety of applications. By utilizing the energy in such a collection efficiently, we can improve the lifetime over which energy can be supplied to the application. We say that the discharge of a collection of batteries is coordinated when, at the end of discharge, the difference in the remaining capacity of individual batteries is small. This paper presents a decision-maker based on a goal-seeking formulation that coordinates the discharge of a collection of batteries. This formulation allows us to use a simple battery model and simple decision-making algorithms. We present results from MATLAB simulations that demonstrate the performance of the decision-maker when energy is drawn out of the collection in three different discharge scenarios. The new decision-maker consistently improves the discharge efficiency obtained using scheduling methods. Our results show that when the discharge is coordinated, the lifetime of the collection is extended.     

桨叶翼型弯度对摆线桨前飞状态气动性能的影响

以前飞状态下的摆线桨为研究对象,使用CFD软件进行数值模拟,非定常时间推进采用双时间法,计算模型的刚体运动采用滑移网格技术处理,分别研究了桨叶相对弯度X和最大弯度位置Y对摆线桨气动性能的影响。研究表明:与桨叶为对称翼型的摆线桨相比,当桨叶具有一定的弯度且最大弯度位置适中时,推力和推进效率都有显著提高;随着相对弯度的增加,推进效率先增大后减小,存在一个最佳的相对弯度X使得推进效率最高;随着最大弯度位置向尾缘移动,相对弯度X=2%C时,推进效率缓慢上升,相对弯度X2%C时,推进效率先增大后减小,存在一个最佳的最大弯度位置Y使得推进效率最高,但升力和载重系数都有所下降。实际应用时,需综合考虑飞行器实际载重确定合适的桨叶弯度。     

Study of a nickel catalyst under conditions of the SER process: Influence of RedOx cycling

The conditions under which a reforming catalyst works in the conventional steady state steam methane reforming process differ considerably from those in the sorption enhanced reforming (SER). First of all these differences are related to a periodic exposure of the catalyst in SER to a reducing or an oxidizing atmosphere. Tests of a commercial nickel catalyst in a fixed bed reactor have shown that in the course of a SER process the catalyst undergoes oxidation–reduction cycles. At higher contents of steam in the mixture of reagents the reduction of the catalyst is suppressed. At the same time, the reduction rate sharply increases in the presence of a small admixture of hydrogen. A comparison of the behavior of Ni and Rh catalysts exposed to SER cycles with that of a Pt catalyst shows a favorable effect of RedOx transformations on the catalytic activity. The best results in a fixed bed reactor were obtained with a catalyst load consisting of a bed of a Ni catalyst and a frontal layer of a noble metal catalyst.     

Study of the transient release of water vapor from a fuel bed of wet biomass in a reciprocating-grate furnace

The present study investigates how sudden changes in fuel moisture affected the combustion characteristics of the fuel bed in a 4-MW reciprocating-grate furnace. The moisture content of the fuel fed to the furnace was monitored online using a near-infrared spectroscopy device, and the water vapor concentration in the flue gas was measured continuously. To obtain experimental data on fuel-bed conditions, the temperature and gas composition in the bed were measured using a probe. A simplified drying model was developed using the measured gas composition values as inputs. The model was then used to estimate the drying rate and to simulate the extent of the drying zone along the grate. Measurements indicated that a change in the moisture content of the fuel fed to the furnace was detected as a change in water vapor concentration in the flue gas with a delay of about 2 h. The model predicted that a portion of wet fuel would need about 2 h to become dry, in line with the measured time delay of the water vapor concentration change in the flue gas. Overall, there was good alignment between the measured and simulated results, supporting the validity of the model and the assumed mechanisms.     

Superposition of vortex cylinders for steady and unsteady simulation of rotors of finite tip‐speed ratio

Joukowski introduced in 1912 a helical vortex model to represent the vorticity of a rotor and its wake. For an infinite number of blades but finite tip‐speed ratio, the model consists of a vortex cylinder of longitudinal and tangential vorticity, a root vortex and a bound vortex disk. A superposition of cylinders is used in this paper to model rotors of radially varying circulation. The relations required to form a consistent system of cylinders are derived. The model contains a term which is not accounted for in the standard blade element momentum (BEM) algorithm. This term is identified as the contribution from the pressure drop due to the wake rotation. The BEM algorithm can be corrected to account for this effect. Unlike previous work on the topic, the contribution is derived for a radially varying circulation. A high‐thrust correction is also presented to extend the model. The optimal power coefficient obtained with this model for the constant circulation rotor is assessed and compared with that of existing solutions. Results from prescribed thrust distributions are compared with that of actuator disk simulations. Steady simulations are performed to compare with the BEM algorithm. The model is also applied to compute the velocity field in the entire domain and perform unsteady simulations. Results for an unsteady simulation corresponding to a pitch change of the rotor is used to compare the model with measurements and a BEM code with a dynamic inflow model. Copyright © 2015 John Wiley & Sons, Ltd.     

Simulation of performance of intermediate fluid vaporizer under wide operation conditions

The intermediate fluid vaporizer (IFV) is a typical vaporizer of liquefied natural gas (LNG), which in general consists of three shell-and-tube heat exchangers (an evaporator, a condenser, and a thermolator). LNG is heated by seawater and the intermediate fluid in these heat exchangers. A one-dimensional heat transfer model for IFV is established in this paper in order to investigate the influences of structure and operation parameters on the heat transfer performance. In the rated condition, it is suggested to reduce tube diameters appropriately to get a large total heat transfer coefficient and increase the tube number to ensure the sufficient heat transfer area. According to simulation results, although the IFV capacity is much larger than the simplified-IFV (SIFV) capacity, the mode of SIFV could be recommended in some low-load cases as well. In some cases at high loads exceeding the capacity of a single IFV, it is better to add an AAV or an SCV operating to the IFV than just to increase the mass flow rate of seawater in the IFV in LNG receiving terminals.     

Properties of a passivating film on the surface of lithium electrodes

The properties of the primary passivation film formed on a lithium electrode in a solution of LiAlCl₄ in thionyl chloride are described. The thickness of the film grows rapidly to 1 – 1.5 nm during the first few hours after contact of the lithium with the electrolyte, and then becomes ≈ 5 nm after a certain period of time. The film has a continuous, not obviously crystalline, structure, and its conductivity for lithium ions has a semiconductor nature that is determined by the presence of defects in the crystal. The film exhibits a p-type electronic conductivity that is caused by electron holes as the minority current carriers, and its presence leads to the further growth of a continuous film. The decrease in the concentration of the minority carriers in the bulk of the film during exposure of the electrode to the solution can be associated with slow structure-ordering processes. The formation of a thick, crystalline secondary film after long electrode exposure hinders mass transfer in the solution layers adjacent to the electrode and preserves the primary film.     

An investigation of wind characteristics on the campus of Izmir Institute of Technology, Turkey

The European Wind Atlas shows a very high wind energy capacity over the Aegean Sea and its coastal regions. Therefore, the western region of Turkey, which has a long coast along the Aegean Sea, appears to have high potential of wind energy. As a result of this fact, several studies have been performed to estimate the wind potential, especially, in western Turkey. However, due to the absence of a reliable and accurate Wind Atlas of Turkey, further studies on the assessment of wind energy in Turkey are necessary. In this study, the characteristics of wind on the campus of Izmir Institute of Technology, located in Cesme peninsula which has long coastline along the Aegean Sea, were studied over a period of one year. Measured data set and its evaluation showed that Izmir Institute of Technology campus area has a considerable wind energy potential. The study presented here is an attempt to promote wind energy in Turkey and to bridge the gap in order to create prospective Turkish Wind Atlas.     

蒸汽喷射式热泵变工况性能分析

采用数值模拟的方法对低压蒸汽增压利用系统中的蒸汽喷射式热泵在非设计工况下的操作性能进行研究，计算并分析了工作蒸汽压力和温度、引射流体压力及混合流体压力等热力参数对热泵操作性能的影响。数值结果表明：当混合流体的压力低于一定的数值时，喷射系数维持一定值；而热泵对引射流体压力的变化极为敏感，引射压力的微小变化可能导致热泵操作性能的急剧下降；提高工作蒸汽的压力并不一定能改善喷射泵的工作性能，这是因为提高工作蒸汽压力会增加额外的蒸汽量所致；喷射系数随工作蒸汽温度的升高而略有增大，并近似呈线性率。     

Comparative study and performance evaluation of central and distributed topologies of photovoltaic system

In this paper, we present a new alternative for improving both the performance of photovoltaic (PV) systems and the efficiency of the energy conversion by using different configuration of power converters. For this purpose, a comparative study between two configurations is carried out. The first configuration consists of a classical PV generator with a single centralized high power converter and the second one concerns a distributed topology. For this latter we use a certain number of PV strings with low power converters attached in series, in parallel or in a combination of series and parallel. Obviously the string topology has some advantages. Each power converter can control the power conversion of each module individually, which results in increased overall energy conversion of the entire system. The MPPT control system in this case can react effectively to atmospheric variations, to shading effect and to changes in the load. The PV system still operates even in case of failure on one of the power converters in a string. We simulated and compared the different conversion configurations in order to find the best one in terms of efficiency and produced energy. The obtained results are very interesting and can lead to optimal sizing and selection of best PV topology for a given application.     

The automotive battery of the future—the role of electronics

The automotive battery is being asked to carry out more challenging duties than ever before. Many of these duties are a result of new types of electrical load. The way in which a battery is operated and managed within a vehicle can be optimized significantly through the use of battery-related electronics with embedded software. Potential benefits include extended life, early warning of deterioration and failure, greater availability and an improved match to the vehicle's requirements. The impact of electronics in other areas shows that there is considerable potential to go much further in this direction with battery systems. There are, however, important system-wide issues to be considered. The battery system must conform to a wide range of standards and practices applicable to automotive electronic systems and embedded software. The automotive industry is itself trying to come to terms with the inherent difficulties involved in developing, qualifying and upgrading complex networks of software-based controllers within the vehicle. The battery system must be compatible with the results of these initiatives. Cost will always be a major influence, but the cost model is different from that familiar to battery producers. This study outlines the main areas where the battery industry must consider a change from being a component to a system supplier, and makes some recommendations for an industry wide approach to smooth the transition.