不同温况点下铝合金液压阀岛溢流阀性能的测试研究

为测试铝合金阀岛溢流阀的性能在(-50～140)℃温况下能否满足使用要求,根据铝合金液压阀岛系统结构和工作原理,并在分析其试验要求的基础上构建了阀岛溢流阀测试平台总体结构。将整个阀岛置于能够调温的高低温柜内,通过在(-50～140)℃的温况下对阀岛溢流阀的动态特性进行测试,分析测试的动态特性曲线,得出测试的结果:液压阀岛在设定的测试温度范围内均能正常调压,无外渗漏现象;液压阀岛溢流阀在(-50～-20)℃的温度下工作时其响应稍为缓慢,但压力稳定可调能正常工作;在(-21～79)℃温况下工作时其响应与(80～140)℃温况下基本没有差异。液压阀岛电磁阀在(-50～79)℃温况下能正常换向,在(80～140)℃温况下却不能。

活塞式制冷压缩机中温工况工质替代的实验研究

近年来,寻求安全、高效、环保的替代制冷剂成为制冷界一项紧迫而重要的任务。在冷藏冷冻半封闭活塞式制冷压缩机上,使用新制冷剂 R404A 的机组已经得到广泛的应用。我国由于成本和施工工艺的限制,R404A 的产品还没有广泛推广,但其需求已经呼声四起。本文通过对半封闭活塞式制冷压缩机中温工况范围内不同工质的性能测试,对压缩机使用 R404A 替代 R22的可行性进行研究。结果表明,活塞式制冷压缩机选用 R404A 作为替代工质,就目前的技术水平而言是适宜和可行的。

Climate state of the Three Gorges Region in the Yangtze River basin in 2022–2023

Based on daily observation data of the Three Gorges Region(TGR)of the Yangtze River basin and global reanalysis data,the climate characteristics,climate events,and meteorological disasters of the TGR in 2022 and 2023 were analyzed.For the TGR,the average annual temperature for 2022 and 2023 was 0.8℃ and 0.4℃ higher than normal,respectively,making them the two warmest years in the past decade.In 2022,the TGR experienced its warmest summer on record.The average air temperature was 2.4℃ higher than the average,and there were 24.8 days of above-average high temperature days during summer.Rainfall in the TGR varied significantly between 2022 and 2023.Annual rainfall was 18.4%below normal and drier than normal in most parts of the region.In contrast,the precipitation in 2023 was considerably higher than the long-term average,and above normal for almost the entire year.The average wind speed exhibited minimal variation between the two years.However,the number of foggy days and relative humidity increased in 2023 compared to 2022.In 2022–2023,the TGR mainly experienced meteorological disasters such as extreme high temperatures,regional heavy rain and flooding,overcast rain,and inverted spring chill.Analysis indicates that the abnormal western Pacific subtropical high and the abnormal persistence of the eastward-shifted South Asian high were the two important drivers of the durative enhancement of record-breaking high temperature in the summer of 2022.

State of China’s Climate in 2020

This report is a summary of China’s climate,as well as major weather and climate events,during 2020.In 2020,the mean air temperature in China was 10.25℃,which was 0.7℃ above normal(1981–2010 average),and the annual rainfall was 694.8 mm,which was 10.3%above normal.In general,disasters caused by rainstorms and flooding were more serious than those by drought.In summer,southern China experienced the most severe flooding with extreme heavy rainstorms since 1998.Drought brought slight impacts and losses in China.The seasonal transition from spring to summer was earlier than normal.High temperatures occurred earlier than normal with extreme values,and lasted longer than normal in summer over the south of China.The number of landfalling typhoons was lower than normal.Cold-air processes had a wide influence and brought a substantial decrease in air temperature in local areas.Compared with the average values of the past 10 years,the affected crop area and the numbers of deaths and missing persons in 2020 were significantly smaller,while direct economic losses were slightly larger.

Bifurcation characteristics of coal spontaneous combustion and analysis of critical state of gaseous reaction in a packed bed

The numerical model was presented for the coal combustion in the packed bed. The bifurcation characteristic of the ignition-extinction of solid-phase smoldering and tran- sition to flaming was studied for the packed bed of coal.One of the Frank-Kamenetskii parameter β_1 was selected as the control parameter.The computed results show that the bifurcation curve is obviously divided into two zones of solid-phase reaction and gas- phase reaction,and the total process of ignition-extinction presents twice bifurcation cha- racteristic.Moreover,the vanishing of critical state of ignition-extinction is studied.One of the transition points,ε_2=0.05,is numerically solved for the vanishing of critical state.The larger the value of ε_2 is,the easier the gas-phase can react.However,the combustion temperature will decrease with increasing ε_2.The other transition point α_2=0.53 is also ob- tained.With increasing the value of α_2,the combustion temperature of gas-phase reaction is close to the smoldering temperature of coal.When α_2 is infinite,the only reaction occur- ring is the smoldering combustion of solid-phase,and the gas-phase cannot react.

Research and Development of ITER Bellows Assemblies

In ITER facilities, there are some special expansion joints connected with the openings of cryostat. Expect for the assemblies connected with NB openings, others are rectangular section with big dimensions and severe working conditions and they are important for ITER safe runing.

Numerical analysis on thermal regime in double-loop channel inductor

In order to investigate the temperature distribution, a three-dimensional finite element model （FEM） was developed to simulate the temperature regime in the channels of double-loop inductor, and the simulated results were compared with experimental data from low load trials of a 400 kW inductor. The results of numerical simulations, such as the temperature and Joule heating rate, show reasonable correlation with experimental data. The results indicate that Joule heating rate and the temperature reach the maximum at the comers and the minimum at the centre of the cross-section area. The temperature difference between the inlet and outlet is in an inverse proportion to mass transport. Joule heating rate and the temperature are directly proportional to power frequency. It is concluded that mass transport and power frequency play a critical role in determining the temperature regime and Joule heating rate, the relative permeability of the magnetic core shows no significant influence on temperature regime and Joule heating rate, when the relative permeability varies from 5 000 to 10 000.

Current Soil Nutrient Status of Intensively Managed Greenhouses

Nine districts covering the main greenhouse vegetable areas in Tianjin Municipality of the North China Plain were selected for the soil investigation in 2010 to survey the current soil nutrient status (soil available N, P and K), acidification and salinization due to excessive input of fertilizers in greenhouses in Tianjin. The study showed that, in particular, soil available P content increased with the age of greenhouses. In contrast, our results did not reveal higher K accumulation and lowered pH in the greenhouse soils compared with cultivation in open fields. Over-fertilization, causing high NO 3 accumulation, most likely resulted in salinity problems in the greenhouses. Ninety percent of the investigated greenhouse soils had electrical conductivity values of saturated paste extracts of 2-10 d S m-1 , which might affect the yields of vegetable crops like green bean, pepper, cabbage, carrot, eggplant, lettuce, spinach, celery, cucumber and tomato. The findings of our survey of the current fertility and salinity problems in greenhouse soils suggest that there is an urgent need to improve the farmers' practices and strategies in fertilization management in greenhouses of China. Because education and the agricultural technical extension services may play a more important role in avoiding overuse of fertilizers, we suggest that current nutrient management practices should be improved in the near future through training of local farmers in farmers' schools and through strengthening the agricultural extension services with practical techniques.