涡轮叶片材料及制造工艺的研究进展

针对航空发动机涡轮叶片的工作环境和使用要求,介绍了提高涡轮叶片耐温能力的两种途径,即加强叶片冷却和提高叶片材质自身的耐温性能。文中着重评述了用作叶片材料的合金及其制造工艺的研究进展与发展趋势。     

高韧性管线用钢试轧工艺的研究

对热轧管线用钢板Ｘ６０Ｈ，Ｘ６５Ｈ试轧过程中的轧制工艺和力能参数进行了较全面的分析研究。     

小型RF激励CO_2激光器冷却设计与温度保护

本文详细介绍了小型ＲＦ激励ＣＯ＿２激光器的冷却措施及温度保护系统，对实际应用有较大的参考价值。     

An assessment of the feasibility of solar absorption and vapor compression cooling systems

For absorption cooling systems to operate and produce their cooling effects they need both thermal and electrical energy, while vapor compression systems need electrical energy only. When operating on solar energy the absorption system may receive all its thermal energy needs from solar sources while its electrical needs (parasitic power) are to be supplied from conventional sources. In order to conduct a fair comparison between the two cooling systems, it is proposed to supply both systems with equal amounts of conventional power and to supplement the rest of their needs from solar sources. A solar coefficient of performance, defined as the ratio of the refrigeration effect to the solar radiation input, is introduced and used for comparing some parameters of engineering ane economic importance in both systems. Economic analysis of solar cooling systems indicates that their initial cost is a function of both their design capacities and the number of hours of full load operation required to fulfill the total daily cooling demand. It indicates, also, that the initial cost of both solar cooling systems would break even before the cost of their respective solar conversion devices do.     

Study of magnetite film formation at metal-scale interface during cooling of steel products

A thin layer of magnetite is sometimes observed in the scales of hot-rolled sheets and wire rod at the scale-metal interface. The results of this study show that this layer of magnetite is produced, during the cooling of the products, by the wustite decomposition. The time/temperature field in which it appears has been defined. This inner layer is composed of pure magnetite, in epitaxy with the neighboring wustite, and the metal surface is not essential to its nucleation. The proeutectod reaction which, during cooling, produces an increase in the oxygen concentration of the wustite in contact with the metal favors the subsequent growth of the magnetite layer.This work was conducted with the technical collaboration of M. Malleret.     

Analysis on Phase Transformation (ATP) Using Computational Thermal Principles (CTP)

COMPUTER ANALYSIS is a method of computerapplication that is expected by heat treaters to yieldbetter results.Quenching is an integral part of industrialheat treatment processes for steels and provides ameans by which the mechanical properties of steel canbe controlled.During quenching,the steel is typicallycooled from above the austenizing temperature anddepending upon the temperature field developed withinthe material,different types of phase transformationsoccur which result in variet…     

Effects of steady-state noise and temperature conditions on environmental perception and acceptability

The combined effects of noise and temperature on environmental perception and acceptability were studied on 18 lightly clothed subjects (0.6 clo), individually exposed for 2 h in a climatic chamber. Three homogeneous climatic conditions were chosen (air temperature at 18, 24 or 30 degrees C, air velocity =0.1 m/s). For each of them, three different noise levels were continuously maintained (35, 60, 75 dBA, recorded fan noise). The 18 subjects were divided into three groups and each group experienced only one single thermal condition, at each level of noise, during three different experimental sessions. Subjective answers about perception and comfort were obtained at t = 30 and 120 min. Main results indicate that acoustic perception decreases when thermal environment is far from thermoneutrality. Although the combined effects of noise and temperature did not influence the physiological data, our results show that whatever the ambient temperature, thermal unpleasantness is higher when noise level increases. Finally, equivalence between acoustic and thermal sensations is proposed for short-term exposure (1 degree C = 2.6 dBA) and for steady state (1 degrees C = 2.9 dBA). In conclusion, this study strongly suggests that interactions between environmental components do exist, right from perceptual level, and might explain some combined effects on cognitive performance.     

Hot water defrosting of a horizontal flat plate cooling surfaceDégivrage par eau chaude d'une surface de refroidissement de plaque plane horizontale

Removal of frost from an jupward facing horizontal cooling plate at a subfreezing temperature using a hot water spray is studied experimentally. The variation of the frost layer with time is approximately linear. A simple analytical model predicts the trend of the frost thickness-time change.     

Etude des facteurs d'intensification de l'échange de chaleur dans le refroidissement des fruits et légumesInvestigating the factors for intensifying fruit and vegetable cooling

Increasing the rate of fruit and vegetable cooling is of economic significance for the following reasons: biochemical and microbiological processes are quickly suppressed; surface mass-exchange with ambient air is slowed down; power consumption is reduced, and the freezing output of cooling equipment and installations is increased.It was assumed that the fruits and vegetables in crates were arranged regularly and covered with thin paper of a negligible small thermal resistance in order to eliminate the infiltration of cold air within the layers. Crates were arranged on a pallet so that they touched horizontally. Thus, the packages form plates above and below the cooling air flow. Heat-exchange with a one-dimensional temperature field is established.It was found that intensification of cooling can be achieved by increasing the speed of cooling air as well as by stopping the process at a higher final temperature. Increasing the speed up to 5 m s^?1 shortens the time of the process by a factor of two compared with the low speeds (0.3–0.5 m s^?1) which are normally used. The product can be cooled until the temperature in the layer centre reaches 5°C, and the surface temperature about 2°C, which is low enough. Afterwards the cooled product is transferred to a freezing chamber or to a van-freezer. This factor results in a further halving of the cooling time. The combined effect of the two factors shortens the duration of the process by about 75% and increases the output of the cooling equipment from 3.5 to 4 times.     

Performance analysis of a triple pressure hrsg

Operating characteristics of a triple pressure reheat HRSG are analyzed using a commercial software package (Gate Cycle by GE Enter Software). The calculation routine determines all the design parameters including configuration and area of each heat exchanger. The off-design calculation part has the capability of simulating the effect of any operating parameters such as power load, process requirements, and operating mode, etc., on the transient performance of the plant. The arrangement of high-temperature and intermediate-temperature components of the HRSG is changed, and its effect on the steam turbine performance and HRSG characteristics is examined. It is shown that there could be a significant difference in HRSG sizes even though thermal performance is not in great deviation. From the viewpoint of both economics and steam turbine performance, it should be carefully reviewed whether the optimum design point could exist. Off-design performance could be one of the main factors in arranging components of the HRSG because power plants operate at various off-design conditions such as ambient tempera-ture and gas turbine load, etc. It is shown that different heat exchanger configurations lead to different performances with ambient temperature, even though they have almost the same performances at design points.