Rolling Contact Testing of Vapor Phase Lubricants—Part II: System Performance Evaluation

The relative effects of several vapor lubrication parameters on bearing performance were examined using a ball-on-rod tester. Lubricants included in the evaluation were a tertiary-butylphenyl phosphate (TBPP), a 2 cSt polyalphaolefin blended with 15 percent TBPP (PAO+), the TBPP blended with 33 percent tributyl phosphate (TBPP+), a cyclophosphazine (X-1P), a polyphenylether (5P4E), and a perfluoroalkylether (Z). Parameters included in the study were bearing temperature, vapor concentration, and vapor temperature. Additionally, a solid lubricant coating was included to improve the bearing performance under cold-start conditions. The lubricants containing phosphorus demonstrated the best high temperature performance. The TBPP lubricant failed shortly after test at 650°C., while the X-1P lubricant performed satisfactorily over an eight-hour period at 650°C. The TBPP+ lubricant demonstrated the widest temperature range capability, with 600°C operation and a projected pump-ability point of–-45°C. Lubricant concentration was the most significant system parameter affecting bearing friction and wear.     

Temperatures in deep grinding of finite workpieces

This paper investigates the diverse thermal effects generated in high efficiency deep grinding (HEDG). Using a new thermal model of circular arc contact with transient analysis, the transient behaviour of the maximum contact temperature has been analysed for various grinding conditions. It is found that steady state conditions can be achieved for the conditions of sufficient workpiece length and high workspeeds. The effect is important for the understanding of the deep grinding process and for the prediction of satisfactory grinding conditions. HEDG conditions also have very apparent effects on the depth of heat penetration to the workpiece. The parameters investigated include mean contact angle, Peclet number and the heat source distribution. Experimental results are presented for specific energy, energy partition and mean temperature for high efficiency deep grinding.     

Cooling Conditions of Ozone Generators

The efficiency of ozone generators is determined by many factors. Operating conditions such as feed gas quality and especially cooling conditions are of utmost importance. Cooling of ozone generators is absolutely necessary, since ozone destruction reactions increase exponentially with temperature. The most common way to cool an ozone generator is water flowing in close contact to the electrodes. The heat removal out of the discharge gap depends on different parameters. Electrical input power, cooling water flow conditions, electrode geometry and material properties are some of them. Simultaneously lowering cooling water temperature, applied power density and gap width, leads to a lower gas temperature in the discharge gap and thus to increased ozone production efficiency. Minimizing the temperature difference between the cooling water inlet and outlet improves the ozone production efficiency as well. This measure, however, results in high cooling water flows and requires additional cooling water chilling, resulting in higher operational costs and capital expenses. Cooling associated costs rise disproportionally with increasing cooling water flow. Simultaneously, energy consumption of ozone generators decreases as the average cooling water temperature goes down. As a result, there exists an optimum between the operational and capital expenses for the combination of ozone generator and cooling water system related expenses, offering significant cost savings for the customer.     

Infra-red radiation thermometry applied to the development and control of gas turbines

Efficient gas turbines operate close to their thermal limits. Detailed temperature mapping of rotating components is needed in development and reliable monitoring in operation. These needs are being met by infra-red radiation thermometers. These thermometers represent a quantum leap in performance over familiar industrial instruments.     

The horizontal-axis solar furnace at the Central Receiver Test Facility

A new horizontal-axis solar furnace is being used for: calibrating sensors for high solar flux-densities; evaluating high temperature materials and coatings; solar chemistry research; and determining thermophysical properties of materials and surfaces. The furnace uses a 50 m² flat heliostat and a 6.7 m diameter parabolic concentrator to produce a 130 mm diameter beam. The peak concentration is over 4000 and could generate temperatures over 2800 K. The total power is over 16 k W.     

New Retainer Material for High Speed and High Temperature Cylindrical Roller Bearing

Cylindrical roller bearings are being developed which can operate over 300°C and greater than three million DN for innovative gas-generators. Under such severe conditions, it is necessary for retainers to be frictionless, lightweight and strong. After preliminary testing, SiC particle reinforced aluminum alloy composite appeared to have good friction and wear properties. It's specific gravity is about one-third of the present material in use, silver-coated SAE4340. In the course of the study, two different friction and wear tests were conducted to investigate the optimum volume fraction of SiC. The results indicated that the most efficient volume fraction was 20vol%. The tensile strength of Al-20vol%SiC was about 140MPa at 300°C. Based on the results of FEM analysis, 140MPa is considered sufficient to endure any stress concentration caused by tensile hoop stresses up to four million DN.     

高线生产优质率分析与改进

分析影响HPB235、Q195、30MnSi等钢种高线优质率的因素,不改变钢种化学成分,试验总结各钢种的开轧温度、入精轧温度和吐丝温度控制范围,提出了提高优质率的措施。     

Materials requirements for highpressure ceramic heat exchangers

When dirty fuels such as coal are used in gas turbine engines, heat input to the cycle working fluid must be through a heat exchanger. To be efficient, such a heat exchanger must operate at 700-1400 kPa and 1100-1200 DC. At these temperatures a ceramic heat exchanger is necessary, and such exchangers have been under development for several years on a modest scale. These programmes are briefly reviewed.

Important topics concerning materials are discussed, and it is concluded that mechanical reliability and joining technology have proved satisfactory in short-term tests, but long-term durability and reliable large-scale manufacture remain to be demonstrated.     

微尺度氧化铁粉还原过程的动力学模拟

用热重分析法研究中低温条件下,氢气还原不同粒度氧化铁的过程,并提出了多颗粒反应料堆动力学模型,以模拟氧化铁微粉在中低温下的还原过程.该模型包括了化学反应动力学方程和颗粒间的气体扩散方程,采用全隐式有限差分方法对控制方程进行数值求解.通过计算得到不同粒度铁矿粉组成的反应料堆在不同温度下,还原率随时间的变化规律,并根据气体浓度在反应过程中的行为得知化学反应和气体扩散在反应速率控制过程中所起的作用.数值模拟数据与试验结果基本吻合.     

元件布局对PCB回流焊温度场的影响

针对某PCB的无铅焊料回流焊工艺,建立了元件四种不同布局条件下PCB的有限元热分析模型,运用Ansys软件,模拟获得了元件不同布局条件下的回流焊过程的温度场分布.结果表明:不同的元件布局会导致回流焊过程中温度场分布不同;将元件置于板面四角时,焊膏和BGA的回流焊峰值温度较高;元件“十”字形布局时,焊膏和BGA的回流焊峰值温度较低;在一定范围内减小元件的横向间距,对PCB回流焊接的影响不大.