集成在微型直接甲醇燃料电池中加热器的设计

根据各种传热机理建立了微型直接甲醇燃料电池的热传导模型,借助有限元分析工具,设计模拟了集成在微型直接甲醇燃料电池中3种不同结构的加热器。仿真结果表明,不同的加热器结构在极板表面将引起不同的温度分布,这将对燃料电池产生不同的加热效果,从而对电池的性能造成影响。其中一种比较理想的加热结构仅引起1.4 ℃的温度偏差,显示了良好的温度均匀性,故在实验中被用来控制工作温度。而另外两种加热结构引起的温度偏差分别是2.1 ℃和3.0 ℃。实验结果表明,当电流53.9 mA时,微型直接甲醇燃料电池工作温度为58.2 ℃,产生的最大功率密度为5.55 mW/cm²。集成后的微型加热器可以通过调整微型直接甲醇燃料电池的工作温度提高其性能,并能在极端环境下工作。     

石油平台用燃料型加热器自动控制与防腐

经特殊设计的石油平台燃料型加热器具有安全可靠、节能高效、抗海水Cl-腐蚀和智能化控制等特点。与"燃气轮机发电-电加热"的原油输送方式相比,热效率成倍提高,经济效益十分显著。在海洋油田井口平台原油加热海底输送方面有较好的应用前景。就海洋石油平台燃料型加热器的结构特点、Cl-腐蚀防护措施以及加热器控制系统的设计进行了介绍。     

Lubricant viscosity and viscosity improver additive effects on diesel fuel economy

This work verifies the impact of lubricant viscosity and viscosity improver additives on diesel fuel economy. Eight lubricants were tested in a single-cylinder, four-stroke, direct injection diesel engine mounted on a dynamometer, under different load and speed conditions. Engine friction power was also investigated through Willans’ line. The results demonstrate that fuel economy obtained from multigrade viscosity oils is higher than that obtained from monograde viscosity oils. A linear relationship was obtained between the high temperature high shear viscosity and specific fuel consumption. The lubricant which provided lower fuel consumption also required lower friction power.     

低温下车用高凝点柴油系统的温度场研究

提出电加热的车用高凝点柴油供油系统能够保证汽车在冬天正常使用高凝点柴油,为确定加热器的功率,建立了系统的物理模型和数学模型,采用ANSYS软件的热分析对系统的温度场进行模拟和进行实车验证试验的方法。上述方法表明:通过ANSYS软件模拟得出电加热输油管的功率(8~20)W之间,电加热吸油管的功率为(90~140)W之间,计算得到电加热吸油管的功率为128.3W和电加热输油管的功率18.7W,两者的功率在模拟的范围之间,实车验证和模拟的误差较小,说明ANSYS软件模拟系统的温度场是可行的。     

An experimental study on spray and combustion characteristics based on fuel temperature of direct injection bio-ethanol-gasoline blending fuel

This study investigated the spray and combustion characteristics of a direct injection spark ignition type system based on the changes in the temperature of the blended fuel (with bio-ethanol and gasoline). The test was performed in a chamber with a constant volume. The diameter and width of the chamber were 86 mm and 39 mm, respectively. The bio-ethanol test fuel was blended at volume ratios of 0 %, 10 %, 20 % and 100 %. The temperature of the fuel was set as −7, 25 and 35 °C. The fuel injection pressure and ambient pressure were set as 4.5 and 0.5 MPa, respectively. The shape and characteristics of the spray were investigated through a spray experiment. The increase in the fuel temperature changed its density and viscosity; this in turn increased spray penetration and spray area and increased the bio-ethanol blending ratio. The combustion visualization and experimental analysis indicated that the decrease in the fuel temperature and the increase in the bio-ethanol blending ratio led to the high viscosity and low heating value. This resulted in an increase in the ignition delay and a decrease in the rate of heat release. It is necessary to adjust the spray strategy and ignition timing to adopt bio-ethanol blended fuel as an alternative fuel.

     

A study on control of heater power and heating time for thermoforming

Obtaining a uniform thickness of the final product using thermoforming is difficult, and the thickness distribution depends strongly on the distribution of the sheet temperature. In this paper, the time-dependent temperature distribution of the total sheets in the storing stage was studied because the temperature after the storing stage is the initial temperature of the heating process. An analytic solution for simulating the storing stage was derived. Using the solved analytic solution, the time-dependent temperature distribution of the total sheets was found out under the condition of assuming that the temperature-dependent specific heat of the ABS sheets was a certain constant value. Finally, the control method for a successful thermoforming using the heater power or heating time was researched in order to improve the quality of the final products. The results show that the satisfied temperature distribution can be obtained by adjusting the heater power or heating time. The method for analysis in this study will be used to improve the quality of the final products.     

火力发电厂在线化学仪表存在的主要问题分析及改进方向

介绍了火力发电厂水汽循环系统在线化学仪表的主要类别,并分析了各类仪表测量误差的常见原因。通过对各电厂在线化学仪表的检测,指出各电厂在线化学仪表计量管理工作中存在的主要问题,并提出了在线化学仪表管理工作的改进方向。     

Influence of Lubricants on Power Loss of Cylindrical Gears©

The total power loss of gears was measured in a back-to-back gear test rig. Test equipment, measuring principle and evaluation of the data are described. The influence of different lubricant type, viscosity and temperature on mesh and churning losses was investigated. The churning losses depended mainly on the viscosity of the lubricant and on the operating conditions, not on the lubricant type. The mesh power loss depended mainly on the type of lubricant, not on viscosity, temperature, or oil additives.

Churning losses can be reduced by using low viscosity lubricants. Mesh power loss can be reduced by as much as 50 percent of the power loss of mineral oils by using polyglycol-type lubricants. In wide application ranges, viscosity and oil additives do not influence mesh power loss. An experimentally-based equation for the coefficient of friction in the gear mesh is given. Earlier derived equations for the mesh power loss of different gear geometry were confirmed.     

An experimental study on the spray characteristics of a dual-orifice type swirl injector at low fuel temperatures

The objective of this study is to investigate the effects of fuel temperature on the spray characteristics of a dual-orifice type swirl injector used in a gas turbine. The major parameters affecting spray characteristics are fuel temperature and injection pressure entering into the injector. In this study, the spray characteristics of a dual-orifice type swirl injector are investigated by varying fuel temperature from — 30°C to 120°C and injection pressure from 0.29 to 0.69 MPa. Two kinds of fuel having different surface tension and viscosity are chosen as atomizing fluids. As a result, injection instability occurs in the low fuel temperature range due to icing phenomenon and fuel property change with a decrease of fuel temperature. As the injection pressure increases, the range of kinematic viscosity for stable atomization becomes wider. The properties controlling the SMD of spray is substantially different according to the fuel temperature range.     

Performance of synthetic oils in the hydrodynamic regime ‐ II. Generalisation

In Parti I the results of an extensive experimental investigation of the performance of environmentally adapted oils in the hydrodynamic regime were reported. Four oils were tested in a tilting‐pad thrust bearing for different combinations of load, shaft speed, and supply oil temperature. In this second part, details of a generalisation procedure are described. A number of parameters representing the physical properties of an oil, such as viscosity and viscosity‐temperature coefficient, are adopted. The influence of each of these parameters on minimum oil film thickness, maximum temperature rise, and bearing power loss is then analysed. It is shown that viscosity measured at the supply oil temperature is the most important parameter. The effects of the viscosity‐temperature coefficient and oil thermal conductivity are less pronounced and yet significant. It is also shown that it is not possible to select an optimum oil that yields maximised oil film thickness, minimised temperature rise, and minimised power loss at the same time.     

考虑混合润滑的飞机燃油泵径向滑动轴承静特性分析

针对飞机燃油泵径向滑动轴承润滑油黏度极低、润滑油膜形成难、表面易磨损等问题,通过综合考虑紊流、热效应、质量守恒、温黏效应及混合润滑边界等因素,建立轴承的热流体动力学润滑分析模型,采用有限元方法联立求解雷诺方程、能量方程、接触方程得到轴承的静态特性,研究轴承间隙比、宽径比、转速、载荷、进油温度等对轴承静态润滑性能如油膜厚度和油膜压力的影响规律。结果表明：由于航空煤油动力黏度低,造成轴承的浮起转速高（大于5 500 r/min）,极限承载力低（小于37 N）、油膜厚度过低;降低进油温度、适当减小间隙,增加轴瓦宽度有利于增加油膜厚度,提高轴承可靠性。研究结果对飞机燃油泵径向滑动轴承设计与运行维护具有一定的工程借鉴价值。     

直接甲醇燃料电池测试用温度控制系统

为了精确控制燃料电池阳极燃料的温度,搭建了直接甲醇燃料电池(DMFC)测试用温度控制系统。针对温度控制对象为定速流动的特点,设计了用于加热流动液体的特殊结构,即将不锈钢软管以双层跑道的布局紧密贴合于三层黄铜板之间,以延长液体在加热块中的流动时间,保证出口流动液体温度的精确控制。计算了不同内径的不锈钢软管最小管长和控制系统的最小加热功率。采用半导体制冷片为流体加热/制冷元件,设计制作了其功率驱动和换向电路。采用基于PID闭环控制的VC++程序设计方法实现了温度自动控制。实验结果表明:温度控制系统的平均升/降温速度为14℃/min,稳态温度控制示值误差±2℃,能够满足DMFC恒定温度条件下实时测试的要求。     

The Effects of Viscosity and Clearance on the Performance of Hydrodynamic Journal Bearings

In the present work, the effects of viscosity and clearance ratios have been analyzed on the reliable performance and design of a steady-loaded, pressure-fed, hydrodynamic cylindrical bearing. The technique for bearing performance evaluation has been developed based on the maximum oil temperature in the region of load carrying oil film, and variation of oil viscosity with temperature.

In this paper viscosity coefficients have been determined using iterative procedures for different oils. And also, a viscosity integral has been evaluated by method of splines as a function of inlet oil temperature to the load carrying oil film and exit oil temperature from the oil film. The viscosity integral has also been evaluated for a bearing operating under different conditions. Thus, by comparison of the viscosity integrals, exit oil temperature from the load carrying oil film and safe load carrying capacity of a bearing with different clearance ratio and using different oils have been examined. Nomographs have also been plotted for easy assessment of bearing performance.

The developed technique gives a more realistic approach for design and performance evaluation of a bearing as compared to conventional procedures. This may have potential as an effective tool to assess performance of a hydrodynamic journal bearing.     

1.5 MW风力发电齿轮箱润滑系统设计研究

开发了多精度等级并联过滤的技术,并合理布局梯度混合型复合纤维过滤材料,有效解决了油液随油温变化自动调节过滤精度并适应高黏度介质的难题;建立了蜡式热动力元件的热力数学模型,根据该模型设计合理的感应元件结构型式,应用于自力式温度控制阀,解决了油液能根据不同油温自动调节通过冷却油路流量的难题。     

基于电喷发动机的挖掘机控制系统设计

现有的机械式发动机排放差、能耗高,采用电喷发动机作为挖掘机的动力源将提高燃油效率,开发电喷发动机的控制系统具有重要意义．在现有挖掘机控制系统的功能分析基础上,确定了基于电喷发动机的控制系统的功能原理图,分析了J1939的协议,确定了电喷发动机的主要参数的解析和控制方法,通过CoDeSys（Controlled Development System）平台设计了电喷发动机的控制系统,并进行了控制试验．试验结果表明：设计的控制系统能正确控制发动机转速和实现相关参数的测量,对挖掘机的电控节能研究具有一定的参考价值．     

物联网技术在火电厂燃料监控管理系统应用中的研究探讨

燃料是火力发电企业的主要生产原料,占发电企业总成本的70％～80％,因此燃料管理是改善发电成本的关键环节。本文提出利用先进的物联网技术作为改善方案,建立传感测控网络,对燃料运行中的各种复杂环节,进行统一监控和管理,达到电厂需要的降低燃料成本、提高生产效率的应用效果,从而发挥提升整个行业进步的技术作用。     

Time Proportioning Computer Control of Resistive Heating

ABSTRACT

The design and construction of an interface to regulate electrical power to a heater (resistive load) for temperature control is described. An overview of various techniques is presented and a specific approach to heater power control is described in detail. The method, however, can be easily adapted to other applications, for example, the manipulation of a solenoid valve to control an average fluid flow rate. The interface described here has a linear relation between the numerical computer output value and the power delivered to the load. This is convenient for both calibration and scaling purposes.     

润滑油水侵对动压可倾瓦推力轴承润滑性能的影响*

针对核主泵、船用轴系等特定工况下推力轴承润滑油的进水问题,以46润滑油和68润滑油为例研究润滑油水侵对推力轴承润滑性能的影响。通过黏度测试获得润滑油中水分质量分数为0、0.5%、1.0%时的运动黏度,采用黏温曲线对润滑油含水前后的动力黏度进行表征。将润滑油的黏温关系代入推力轴承的润滑计算当中,获得不同含水量下轴承的最小油膜厚度、温升、流量及功耗等静态特性参数,并分析含水量对推力轴承起飞转速的影响。研究结果表明：润滑油含水后对最小油膜厚度和功耗影响较大,对温升和流量影响较小;随着润滑油含水量的增加最小油膜厚度和功耗均降低,而温升增大,流量减小;使用2种润滑油在不含水和水分质量分数为0.5%时的起飞转速都在50 r/min以下,水分质量分数为1.0%时起飞转速都在50 r/min以上,表明随着含水量的增加起飞转速增大。     

基于有限元的盾构机主轴承腔内润滑特性研究

盾构机主轴承具有尺寸大、承受载荷高且转速慢的特点,研究其主轴承腔内润滑状况,对于保证盾构机主轴承的可靠性至关重要。运用三维建模软件及流体仿真软件对盾构机主轴承进行建模及腔内流体域仿真,研究主要润滑参数包括进油口位置分布、进油口的选择、润滑油黏度对腔内润滑状态的影响,以及腔内润滑状态与温度的关系。结果表明：进油口位置分布对润滑状态有着较大影响,非对称进油口分布对这种极低速旋转及重载的盾构机主轴承更有利;为改善润滑状态,进油口应分主进油口和副进油口,保持主进油口常开,副进油口的打开视工况而定;润滑油黏度对润滑状态及温度都有较大影响,存在最佳黏度区间使得温度保持较低水平且润滑状态良好;对应位置润滑油体积分数与温度成反比关系。     

火力发电厂煤粉流量测量技术研究

火力发电厂总燃料量的精确测量是进行锅炉燃烧控制优化的关键难点问题。本文系统地提出了火力发电厂煤粉流量的测量技术,并结合实际应用经验提出各种测量方法的技术要点以及制约点,同时结合工程实践提出了煤粉流量测量技术的发展展望,为进一步研究实践煤粉流量的测量技术奠定了基础。