全氟弹性体的化学结构及物理性能

论述了全氟弹性体的化学组成、结构及其交联剂。对全氟弹性体的物理特性 :如热变形、对工作介质的稳定性、气密性、耐低温性能和热老化性能等作了详细论述。只要选择适宜的单体进行合成 ,并根据具体要求使用不同的交联剂 ,就可制得能满足各种需求的全氟弹性体。

GFY-5(7)型“剪切”防堵关风器

文章着重阐述了这种新型关风器的构造。通过改变叶片的倾角,提高叶轮的加工精度及含油轴承的运用,使关风器具有较强的防堵性能与密气性能。

Study on hydrostatic gas lubricated non-contacting mechanical seal

The principle and characteristics of hydrostatic gas lubricated non-contacting mechanical seal （HSGLNMS） are introduced. The flow field of the gas film is established by numerical analysis of end faces of HSGLNMS. The distribution of gas film pressure and seal performance parameters inclu- ding opening force and leakage are obtained. Influence of operating parameters and sealing configu- ration on the sealing performance is studied. HSGLNMS has been designed and manufactured. Its working film thickness and leakage are measured to verify the theoretical analysis. The investigation results show that HSGLNMS demonstrates good speed adaptability, which means that the seal runs successfully with both low and high speed, showing excellent performance. The seal can be regula- ted and controlled online ; the opening force will not be raised greatly with the increasing of the num- ber of throttle orifices, but the leakage of seal increases apparently ; the uniform pressure groove im- proves the sealing performance, for example, opening force and stiffness are raised obviously. While leakage is reduced. Finally, the theoretical analysis is verified by experiment.

Adsorption structures of frothers at gas–liquid interface using DFT method

Density functional theory (DFT) simulation was performed to investigate the adsorption mechanisms between frothers and gas–liquid interface. In water phase, the polar head group of the frother molecule was connected with water molecules by hydrogen bonding, while the non-polar group showed that hydrophobic property and water molecules around it were repelled away. The adsorption of water molecules on single frother molecule suggests that the complexes of α-terpineol-7H2O, MIBC-7H2O and DF200-13H2O reach their stable structure. The hydration shell affects both the polar head group and the non-polar group. The liquid film drainage rate of DF200 is the lowest, while α-terpineol and MIBC are almost the same. The adsorption layer of frother molecules adsorbed at the gas-liquid interface reveals that the α-terpineol molecules are more neatly arranged and better distributed. The DF200 molecules are arranged much more loosely than MIBC molecules. These results suggest that the α-terpineol molecule layer could better block the diffusion of gas through the liquid film than DF200 and MIBC. The simulation results indicate that the foam stability of α-terpineol is the best, followed by DF200 and MIBC.

Modeling Relative Humidity Effects on Power Electronic Performance

Variations in the behavior of power supplies caused electrical behavior dependence with environmental conditions. by environmental conditions require accurate characterization of the This paper introduces models to help predict relative humidity （Rtt） and other environmental factors influence on sensitive circuitry in power electronic systems. The resistivity and permittivity of an insulator have been modeled using different water contents i.e. RH, such model also included the mechanical properties of the design. An application example of a high power density, high voltage DC-DC converter is used to verify the results.

Thermal transfer experimental research of a horizontal tube evaporative condenser

The thermal resistances distribution in different wet-bulb temperatures, air velocities and spraying water densities were achieved by the experimental test. The fluctuation of the water film convection and the water-air interfacial thermal resistance were reviewed especially. In the distribution of thermal resistance, the rank of the thermal resistance proportion （from max to min） is air flow heat transfer resistance, heat transfer resistance between refrigerant and wall, water film convection resistance and wall heat transfer resistance. When the heat flux is constant, the total resistance lowers nearly along with the increasing of air flow and water spray density. But there are a best air flow value of 2.98 m/s and a best spray water density of 0.064 kg/（m ·s） respectively, if continue to increase them, condensation performance is not significantly improved any more. The test results are available to improve the evaporative condenser performance and the designing lever.

Seat tightness of pneumatic cryogenic control valve

Pneumatic cryogenic control valves(PCCV)are designed to meet the special requirements for the large cryogenic helium refrigeration system.Polychlorotrifluoroethylene(PCTFE)is adopted as the flat seal material of the valve seat.The leakage rates and compressive strain of the PCTFE gasket with different sealing stress are tested at both room temperature(293 K)and liquid nitrogen temperature(77 K).After 300 open/close cycles,the experimental results show that the sealing properties of the PCTFE gasket are improved.The leakage rates are about 10-8(293 K)and 10-4(77 K)Pam3 s-1 respectively.Finally,the effects of working pressure on sealing characteristics are discussed.The working pressure has little effect on compressive strain but it has a great influence on leakage rate.The leakage rate is linear with the working pressure of inlet at room temperature,but at liquid nitrogen temperature the leakage rate is linear with the square of the working pressure.

Experimental Study on Frictional and Sealing Performances of Packing Rings in an Oil-free Gas Compressor

To enhance the reliability and to extend service life of packing rings, tribological and sealing perfor- mances are investigated based on the experimental results. Friction force, leakage rate and power consumption of three materials of pressure packing seals are measured in a refitted vertical gas compressor. The rings are made of common filled polytetrafiuroethylene （Filled PTFE）, PTFE reinforced with 30% mass fraction carbon fiber （30%CF^PTFE）, and carbon-carbon composites infiltrated with PTFE （C/C＋PTFE）, respectively. It is found that packing rings will periodically vibrate with the periodic vibration of pressure packing after the travel direction of motion abruptly turns to the reverse direction. Furthermore, the amplitude of vibration slows down with the increasing crank angle. Approximate value of friction force is available by multiple-point fast Fourier transformation （FFT） employed to process the experimental results by reducing the impact of vibration to a great extent. Of three materials of rings employed in experiments, Filled PTFE presents minimal leakage rate accom- panied with maximum power consumption. And 30%CF＋PTFE exhibits minimum friction power and moderate leakage rate. As for C/C＋PTFE, its high mechanical and thermal properties are favorable factors to enhance the ability of operating under high pressure and velocity and to improve the wear resistance. Unfortunately, this also leads to a large leakage rate. Comprehensive consideration should be taken into to evaluate the availability, reliability and service life for a type of packing ring under dry running conditions.