A droplet breakup model is developed for a single droplet introduced into transcritical and strong convective environments. The numerical model takes into account variable thermophysical properties, gas solubility in the liquid phase, and vapor–liquid interfacial thermodynamics. The influences of ambient conditions on droplet breakup characteristics are investigated. The results indicate that (1) the drag acceleration decreases slowly at first and then increases drastically with the initial droplet temperature increasing, but always increases at a constant rate with ambient pressure; (2) the pressure and the drop temperature have similar effects on the Kelvin–Helmholtz and Rayleigh–Taylor wave growth at high pressures (reduced pressure higher than 1.2) and high temperatures (reduced temperature higher than 0.7), but the impact of pressure on the wave growth is relatively stronger than that of droplet temperature at relatively low pressures (reduced pressure lower than 0.8) and low temperatures (reduced temperature lower than 0.63); (3) the temperature significantly affects the surface instability growth at high drop temperatures (reduced temperature higher than 0.7), but has no effect on the instability growth at low temperatures (reduced temperature lower than 0.63).
The use of (recycled) plastics and (waste) vulcanized rubber powder is the main polymer of raw materials, and composite organic additives are selected to fully combine with asphalt components. The physical and chemical reactions between different components are completed in dynamic mixing, establishing a morphology structure similar to thermoplastic elastomers (TPEs), and a thermoplastic highly asphaltized alloy material. TPE-modified asphalt not only significantly improves the high-temperature stability of the base asphalt, but also has the social and economic value of rational utilization of resources and turning waste into treasure. There are very few studies on the preparation of modified high-viscosity asphalt formulations using rubber and plastic as modifiers. In this study, rubber, plastic, and plasticizers were added to the base asphalt, and the TPE modifier formulations were developed through the research of new TPE modifier series and functional formulations, preparation process, and its modified asphalt properties. Meanwhile, the preparation method of the rubber–plastic alloy modifier was determined. The performance of the TPE-modified asphalt was verified through performance verification tests to evaluate the modification effect of the modifier on the base asphalt. The test results showed that the penetration, softening point, ductility, and viscosity indexes of the TPE-modified asphalt developed through the proposed formulation, and it met the specification requirements for high-viscosity modified asphalt. Rubber and plastic modifiers significantly improved the high-temperature stability of the base asphalt. In addition, the rubber–plastic modifier had a significant tackifying effect, with a dynamic viscosity of 60 °C and a Brinell rotational viscosity much greater than asphalt and rubber asphalt. The microscopic mechanism of the newly developed TPE-modified asphalt was analyzed by fluorescence microanalysis. The results showed that the rubber–plastic modifier fully swelled in the asphalt and was uniformly dispersed in the asphalt as a floc. The network structure of activated waste rubber powder-modified asphalt was more uniform and dense, resulting in good performance of the modified asphalt, and stable storage of modified asphalt was obtained. Through appropriate formulation, the comprehensive performance of the TPE-modified asphalt obtained met the requirements of pavement application and construction, providing a good theoretical basis for promoting TPE-modified asphalt.
The importance and the selection basis of inputted rain parameters including rainoff duration, rainoff intensity and design return period in drainage design for porous asphalt concrete pavement are discussed in this paper, which is expected to adopt the suitable concept and method in this kind of issue.
The gravity oil feed method dose not suit for microgravity environment as the same way dose for ground lubrication system. It is the key problem to be solved that how to supply the oil to friction surface in space liquid lubrication system. It analyzed the lubricating manner. A space liquid lubrication system was designed based on a principle of using deformation energy to supply oil. In the analysis of its basic structure and operating principle, the film calculation mode was established based on the elastohydrodynamic lubrication theory. The lubricating performance was simulated by ANSYS finite element analysis software in microgravity. The calculation results show that: in the microgravity, it could achieve elastohydrodynamic lubrication on friction surface in this lubrication system. When the oil supply hole diameter is 2mm, the film-thickness ratio changes between 1.91 and 4.28. It belongs to elastohydrodynamic lubrication. The hole diameter decreases, the film thickness reduces. The minimum film-thickness ratio is 0.93 when the temperature changes widely from -50°C~+80°C. It belongs to boundary lubrication state.
The straightener of pulse tube refrigerator (PTR) can change gas flow distribution in the tube and improve performance of PTR .In this paper numerical simulation is used to study and optimize the property parameters of straightener with helium as work fluid. The straightener is treated as porous media. The key parameter fk. is defined as the ratio of streamwise and transverse permeabilities. The smallest length of straightener is optimized by changing the value of fk. The result shows that straightener can change gas flow distribution in tube and improve performance of PTR. fk. is bigger, the length of straightener is shorter and streamwise pressure drop is smaller.
According to the meteorological data between May and September from the year 1991 to 2012 in Dangxiong County,the reference evapotranspiration was calculated by FAO56 Penman-Montieth formula. Variation and influences of annual evapotranspiration and monthly evapotranspiration also had been researched. The results show that: a) in Dangxiong County of Tibet,ET0,the highest temperature,average temperature are in rising interannual variability,while the average relative humidity is decreased year by year from 1991 to 2012 in the period of crop growth. The interannual fluctuation of ET0has obviously been affected by the highest temperatures,average temperature,average relative humidity and average rainfall,and the order of influence is average relative humidity the highest temperatures average temperature rainfall; b) from 1991 to 2012, monthly average of ET0is rising in May and June and decreasing from July to September. The maximum and the minimum value appear in June and September respectively; c) the main influence factors to ET0are different. The hours of sunshine is the main influence factors in May,August and September. The temperature and rainfall are key factor respectively in June and July; d) the interannual variability of ET0is mainly affected by ET0's fluctuation in May and June,followed in July and September,and August is smaller,hence,the climate change in May and June is more significant than the other months in the area of middle Tibet in recent years.
The property and the value of bamboo resources,and the possibility of the sustainable utilization of bamboo resources in Zhaotong city of Yunnan Province were analyzed.The results showed that the exploitation and the sustainable utilization of bamboo resources were a new way of rural sustainable development.At the same time,the countermeasures of the sustainable utilization of bamboo resources were brought forward.
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