液氮冻结竖直向与水平向温度场特性

分析液氮冻结的现场实施情况,结合工程背景资料建立数值分析模型,通过计算分析并与现场实测成果验证,系统研究液氮冻结过程中竖直方向与水平方向温度场分布特征及其变化规律。结果表明：液氮冻结通过沸腾吸热与对流换热方式达到降温冻结的效果,相较于盐水循环冻结方式,液氮冻结效率高,周期短;但其冻结温度场分布不均匀,在竖直方向上存在较大温差,温度最低区域分布在液氮沸腾区范围,而水平方向上分布较为均匀;温度场中低温区域并不在两排冻结管之间均匀发展,冻结区域向连续墙方向发展的速度比土体方向发展速度快。基于研究成果,提出了液氮冻结加固设计、施工的优化建议,为今后液氮冻结工程提供理论依据与技术参考。     

Energy storage system with ultracapacitors for thermal underwater glider

A power system with proton exchange membrane fuel cells (PEMFC) was designed for thermal underwater glider.Heat generated by PEMFC is used as the propulsion power of the glider,and the electricity is used in the control and sensor system.An electric energy storage system (ESS) is required which possesses high power density with good cycle life.Ultracapacitors which exhibit high power density and cycle life are considered as energy storage devices.Simulations based on a specific voyage condition indicate that ESS with ultracapacitors has positive effects on reducing the output power demand of PEMFC and lightening the power system.Experimental results show that the state of charge (SOC) is related to the capacitance and resistance in ultracapacitor ESS.     

电力企业销售与收款内部会计控制初探

电力销售是供电企业主要的收入来源。鉴于江苏省电力系统销售与收款业务内部会计控制制度建设的现状和存在的问题,加强电力企业销售与收款的内部会计控制建设,对电网企业销售与收款业务相关流程进行改进,总结归纳电网企业销售与收款业务内部会计控制的关键点,对完善江苏省电力公司销售与收款业务内部会计控制制度,有着极其重要的现实意义。     

Simulation of CO2 Brayton Cycle for Engine Exhaust Heat Recovery under Various Operating Loads

A bottoming cycle system based on CO2 Brayton cycle is proposed to recover the engine exhaust heat. Its performance is compared with the conventional air Brayton cycle under five typical engine conditions. The results show that CO2 Brayton cycle proves to be superior to the air Brayton cycle in terms of the system net output power, thermal efficiency and recovery efficiency. In most cases, the recovery efficiency of CO2 Brayton cycle can be higher than 9% and the system has a better performance at the engine’s high operating load. The thermal efficiency can be as large as 24.83% under 100% operating load, accordingly, the net output power of 14.86 kW is obtained.     

惠州电厂联合循环机组旁路控制系统的特点

介绍了惠州LN G电厂联合循环机组旁路控制系统的调节、控制方式,并分析了旁路控制系统在运行中的作用。     

小功率风光互补发电系统最大功率跟踪之变步长扰动法研究

小功率风光互补发电系统控制算法的变步长扰动方法可通过调节触发脉冲的占空比来实现最大功率的跟踪控制．利用MATLAB／Simuiink中的一些元器件搭建了最大功率控制模型．     

Digitally controlled boost PFC converters operating with large scale load fluctuations

When boost power factor correction （PFC） circuit works with large scale load fluctuations, it is easy to cause a higher total harmonic distortion and a lower power factor because of traditional controllers and inductor cur- rent mode. To solve this problem, this paper proposes a PFC control system, which can operate with load fluctuations up to 1 000 W by using duty cycle feed-forward control theory to achieve smooth switching mode. The duty cycles in the next period of the control system are pre-estimated in the current cycle, which enhances the speeds of AD samplers and switching frequency, and reduces the cost and volume of the equipment to some extent. Introductions of system decoupling and feed-forward of input-voltage greatly improve the system performance. Both theoretical simulation and experimental results prove the advantage of the proposed scheme.     

M701F型联合循环机组的汽轮机旁路控制系统分析

通过分析M701F型燃气-蒸汽联合循环电厂的汽轮机旁路控制系统的功能、运行工况,给出适合联合循环机组汽轮机旁路系统的控制逻辑和动作行为,实现了在机组运行不同阶段进行自动控制的模式,并给出定值形成、参数整定、保护和闭锁逻辑的设计,使旁路控制系统能够实现机组运行和启、停机时的安全稳定,使运行人员更好地掌握机组运行中的旁路系统动态特性,并给事故分析提供重要的理论及实践依据。     

Evaluation on energy performance in a low temperature district heating system integrated with organic Rankine cycle

Combined heat and power (CHP) coal-fired plants and heat-only boilers are still working as main heat sources in North China. These provide high temperature water on the primary side of district heating (DH) systems. There can be large temperature differences between the primary side and secondary side deployed in low temperature district heating (LTDH) of buildings. In this paper, a LTDH system, integrated with an organic Rankine cycle (ORC) system, is presented and evaluated on how to utilize the limited temperature difference between the primary and secondary sides in a substation. Two cases are illustrated of the performance of two modes (series or parallel connection) and energy efficiencies of the configurations with or without an ORC system. The results showed that the integrated ORC system could provide sufficient power for the circulating pumps in the DH system. The integration of the ORC leads to only a very slight decrement on the supply water temperature. Generally, the series mode can generate the maximum output power from an integrated ORC system. The parallel mode showed more flexibility on the adjustment of output power from the ORC system, especially where domestic hot water is needed. When the cold tap water was used as a cooling stream in the condenser of an ORC system before preparing to be the domestic hot water, it is very helpful in improving the performance of the ORC and increasing the energy efficiency of the DH system.     

无复位开关的单周控制新方法研究

采用积分复位的单周控制方法在变换器控制领域得到了广泛的研究。但是,由于它采用了积分复位开关,使其变成了一个十分复杂的非线性控制系统,建模和系统设计都非常困难。本文在分析单周控制方法基本原理的基础上,提出了无复位开关的单周控制新方法,以Buck变换器为例,建立了控制系统的小信号模型,通过理论分析和仿真结果证明了该方法的正确性。     

基于ARM的液位自动控制实验系统

为提高嵌入式控制系统设计课程质量,研制一种水箱液位自动控制系统。系统由ARM7S3C44B0X、液位检测模块、直流水泵驱动模块、电源模块以及LCD显示模块等组成。首先采用电阻式液位检测模块获取液位高度脉冲频率信号,根据在单位时间内获取外部中断信号的次数确定液位高度,最后通过PID控制算法计算,经定时器产生PWM波信号控制直流水泵输出的流量。介绍了硬件电路和软件设计过程。研制的实验装置制作简单、成本低廉,并取得了良好的教学效果。     

移动小车电源 SOC 实时估算系统设计

针对移动小车无法实时显示当前电量,易出现电池过放从而降低电池循环使用寿命的问题,利用 Arduino 作为主控制器采集电池的电压、电流、温度数据,将三者作为 BP 神经网络的输入量,计算电源 SOC 值,最后通过 LabVIEW 平台嵌入该算法实现对电源 SOC 的实时估算。实验结果表明,神经网络训练误差可满足实际要求,硬件系统整体运行可靠。系统可以实时监测电源的 SOC 值、电压、电流和温度值,从而避免电源出现异常工作状态,提高电池循环使用寿命。     

从莫斯科大停电浅析发供电设备管理

在分析2005年5月25日莫斯科大停电事故原因的基础上,提出电力企业要打破传统的管理模式,采用先进的管理手段,提高设备综合管理水平,构建发供电设备运行预警体系,促进安全生产。讨论了夏季高温峰荷时的设备管理,强调了大停电时备用发电设备的重要性。     

吉布斯—杜亥姆公式应用的探讨

化学势的零次齐次函数性质是吉布斯—杜亥姆公式的本质内容,并从这个性质导出了在等压与不等压条件下,二组分气液平衡系统,液相组成与各种气体分压关系的一般规律,并对两种不同导出过程的特点进行了比较.     

Simulation and analysis of energy optimization for PEMFC hybrid system

INTRODUCTION Proton Exchange Membrane Fuel Cell (PEMFC) is being rapidly developed in recent years because of its compact structure, light weight, low working temperature and rapid startup characteristics. But its E-I characteristic curve reveals its decreasing per- formance when confronted with suddenly increasing power demand, and high cost also restrains the ap- plication of the fuel cell. So the hybrid power scheme is the most suitable selection presently. Most of researches on fu…     

Measurement of boiling heat transfer coefficient in liquid nitrogen bath by inverse heat conduction method

Inverse heat conduction method （IHCM） is one of the most effective approaches to obtaining the boiling heat transfer coefficient from measured results. This paper focuses on its application in cryogenic boiling heat transfer. Experiments were conducted on the heat transfer of a stainless steel block in a liquid nitrogen bath, with the assumption of a 1D conduction condition to realize fast acquisition of the temperature of the test points inside the block. With the inverse-heat conduction theory and the explicit finite difference model, a solving program was developed to calculate the heat flux and the boiling heat transfer coefficient of a stainless steel block in liquid nitrogen bath based on the temperature acquisition data. Considering the oscillating data and some unsmooth transition points in the inverse-heat-conduction calculation result of the heat-transfer coefficient, a two-step data-fitting procedure was proposed to obtain the expression for the boiling heat transfer coefficients. The coefficient was then verified for accuracy by a comparison between the simulation results using this expression and the verifying experimental results of a stainless steel block. The maximum error with a revised segment fitting is around 6%, which verifies the feasibility of using IHCM to measure the boiling heat transfer coefficient in liquid nitrogen bath.     

Design on general development platform for FPD systems

In this paper, a multi-functional development platform for flat panel display (FPD) development is proposed. With the proposed development platforms, a variety of FPD devices, including organic light-emitting diode (OLED) screens, liquid crystal display (LCD) screens with touchscreens, OLED microdisplay screens, etc., can be directly and instantly connected, examined and utilized. A field-programmable gate array (FPGA) is used in the development system to drive different types of FPD devices, and ARM11 S3C6410 is used as the application processor to provide various services. The development system uses Linux as the system kernel, Qt for Embedded Linux as the UI framework, various system libraries for video and audio services, and a custom-made user engine for fine-polished appearance and behavior. The development platform has been used not only in testing and verification of the FPD devices, but also in building OLED-powered handheld digital devices, shortening the development cycle from OLED devices to mature application products.     

传统液体除湿技术的改进

提出一种新型的液体除湿系统——超声雾化液体除湿系统,该系统用超声雾化技术取代了传统塔式除湿过程中的填料,避免了由填料带来的溶液耗量大和阻力大的缺点.建立了数学模型来预测在理想条件下液体除湿过程的效率及耗液量.通过对比计算结果和传统塔式除湿的实验数据,发现后者的溶液耗量远大于理想情况下的耗量.另外,在提出的系统中除湿过程发生在通过超声作用产生的微小除湿剂液滴表面,等量的除湿剂能够产生更大的反应表面积;整个新系统中没有喷嘴和溶液泵,系统阻力和能耗相应降低.因此,该方法比塔式除湿方式更接近于理想情况.     

电镀工业氮氧化物废气治理技术

本介绍了氮氧化物废气的来源、危害以及电镀工业氮氧化物排放特点，着重介绍了治理氮氧化物废气的几种方法，并对吸收液和吸收塔进行了深入的探讨和研究。结果表明，使用碱性溶液作为作为吸收液．使用旋流板塔作为吸收设备是治理电镀工业氮氧化物废气的一种较为成熟、可靠的技术。     

莲瓣兰内生真菌对氮源利用的研究

本文对分离自莲瓣兰(Cymbidium lianpanTang et Wang)根内的5株内生真菌利用氮源的生理学特性进行研究,采用的方法是三点种植实验,培养5天,测量氮源培养基上内生真菌菌落直径,同时,进行液体培养5天,将菌丝过滤,烘干至恒重,计算菌丝干重。结果如下:这5株内生真菌利用氮源能力各不同;其中,属于木霉属的LP161菌株对多数氮源有较好的利用能力,但对尿素利用能力较差;并且,LP161菌株在硝酸钾液体培养基内生长最快,培养5天后菌丝干重达到0·78g/100ml。