Numerical simulation analysis on multi-layer low-temperature heating method of asphalt pavement in hot in-place recycling

Asphalt mixture pavement reheating is one of the important steps in hot in-place recycling(HIR).To improve the heating speed of asphalt pavement in HIR,based on the numerical analysis model of asphalt mixture heating process,a new multi-layer low-temperature heating method(MLHM)was proposed.Considering input heat flux,the thermal capacity and thermal resistance of asphalt mixture,the heat transfer model was established based on energy conservation law.By heating the asphalt mixture in layers,it changes the situation that the heat energy can only be input from the upper surface of the asphalt mixture pavement.Through the simulation of the heating method of asphalt mixture in the existing technology,the result shows that the existing heating methods lead to serious aging or charring of the asphalt mixture.By MLHM,the upper and the bottom of the asphalt mixture are heated at the same time,and the heating temperature is lower than other heat methods,which not only reduces the heating thickness and increases the heating area of the asphalt mixture pavement,but also improves the heating speed,saves the energy resource and ensures the heating quality.Especially,by MLHM,the heating uniformity is better and speed is faster.

Deformation simulation of low-temperature high-speed extrusion for 6063 Al alloy

The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine, and the forming of 6063 rod cxtrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of 25 on the platform of DEFORM 2D successfully. From the compression experimental results, the flow stress model of this Al alloy is obtained which could be the constitutive equation in the simulation of low-temperature high-speed extrusion process. From the numerical simulation results, there is a higher strain concentration at the entrance of the die and the exit temperature reaches up to 522 ℃ in low-temperature high-speed extrusion, which approaches to the quenching temperature of the 6063 Al alloy. The results show that the low-temperature high-speed extrusion method as a promsing one can reduce energy consumption effectively.

电弧喷涂在电厂锅炉水冷壁防护的应用研究

对电厂锅炉水冷壁低温热腐蚀现象和原因进行分析,研究现有锅炉管道低温热腐蚀防护方法的优点和不足,提出采用电弧喷涂涂层解决水冷壁热腐蚀问题。通过对电弧喷涂涂层结合力和耐高温腐蚀性能进行试验研究和工业应用,表明电弧喷涂技术是改善锅炉管道低温热腐蚀的有效途径。

Break of thermal equilibrium between optical and acoustic phonon branches of CsPbI_(3)under continuous-wave light excitation and cryogenic temperature

The kinetic of low-temperature carrier and lattice of lead-halide perovskite is yet to be fully understood.In this work,we investigate the steady-state photoluminescences(PLs)of CsPbI_(3)at the environmental temperature(Te)ranging from 20 K to 300 K,and observed anomalous behaviors at cryogenic temperatures:The carrier temperature(Tc)of pure CsPbI_(3)exhibits a negative correlation with Te,accompanied by an expansion in Urbach tails of absorption spectra(Abs.)and excessive red-shifts at peak energy of PLs.These phenomena are also observed in those samples containing a certain amount of Cs_(4)PbI_(6),but to a lesser extent and occurs at lower temperatures.It is attributed to the intensified hot phonon bottleneck effect(HPB)in CsPbI_(3)at cryogenic Te,which hinders the energy transfer from hot carriers,via longitudinal optics(LO)phonons to longitudinal acoustic(LA)phonons,to the ambient.For samples under continuous-wave laser excitation,in specific,the barrier induced by the enhanced HPB at low Teprevents the effective thermalization among carriers,LO and LA phonons,which,therefore,form thermally isolated ensembles with different temperatures.At cryogenic Terange,the elevated temperatures of carrier and LO phonon expand the high-energy side of PLs and the low-energy tail of Abs.,respectively.For those samples in which the CsPbI_(3)is mixed with Cs_(4)PbI_(6),the interfacial LO-LO interaction across them provides a bypass for heat dissipation,mitigating the heat accumulation in LO-phonons of CsPbI_(3).The results suggest that a strong HPB effect may break the thermal equilibrium among different branches of phonons in the lattice under certain extreme conditions.