Microwave-assisted ignition(MAI)is a promising technology to improve the ignition stability in internal combustion engines under lean conditions.To investigate the interplay between the microwave pulses and the electrical characteristics of ignition plasma,the high-time-resolved electrical characteristics of MAI are measured based on the discharge voltage and current profiles with microwave power varying from 0 to 1000 W.The effects of microwave pulse on the electrical characteristics in the breakdown and glow discharge phases are discussed respectively.The results show that the microwave-induced-voltage-decline(MIVD)occurs during the glow discharge phase,which originates from the increment of free electrons and the additional microwave field.However,this voltage decline is insignificant in the breakdown phase.Moreover,as the free electron number reaches a critical value,a shining plasma can be observed between the gap of electrodes and the voltage decline is stabilized to a"saturated voltage curve".Ultimately,the effect of microwave plasma on the enhancement of ignition kernel area is explored.The result indicates that the enhancement effect increases with plasma duration rising.Those enhancements of earlier-generated plasmas are more significant than those of subsequent plasmas due to the distance limit of the plasma propulsive effect.
SUN WeiCUI YiSONG DaweiTONG ZongpengWU HuiminWANG Zhaowen
In this context,the present study proposes the use of microwave irradiation to improve the dehydration rate and efficiency of strontium hydroxide octahydrate(Sr(OH)_(2)·8H_(2)O)without introducing contaminants.This study revealed that the use of microwave irradiation to dehydrate Sr(OH)_(2)·8H_(2)O is feasible and surprisingly efficient.The effects of this approach on important parameters were investigated using response surface methodology(RSM).The results revealed that the microwave dehydration process follows a linear polynomial model.In addition,compared with the heating time and material thickness,the microwave-assisted dehydration of Sr(OH)_(2)·8H_(2)O is sensitive to the microwave power and not to the material mass.The relative dehydration percentage reached 99.99%when heated in a microwave oven at 950Wfor just 3 min.In contrast,a relative dehydration percentage of 94.6%was reached when heated in an electric furnace at 180℃for 120 min.The XRD spectra also revealed that most of the Sr(OH)_(2)·8H_(2)O transformed into Sr(OH)_(2)after dehydration via microwave irradiation,whereas a significant portion of the Sr(OH)_(2)·H_(2)O remained after conventional electric dehydration.The experimental data were fitted and analyzed via the thin-layer drying dynamics model,and the results indicated that the dehydrating behavior of Sr(OH)_(2)·8H_(2)O could be well described by the Page model.
Developing favorable bio-based polymers that replace petroleum-based plastics is an essential environmental demand.Lignin is a by-product of the chemical pulping industry.It is a natural UV protection ingredient in broad-spectrum(UVA and UVB)sunscreens.It could be partially and selectively acetylated in a simple,fast,and more reliable process.In this work,a composite film was prepared with UV-resistant properties through a casting method.Bio-based cellulose acetate(CA)was employed as a major matrix while nano-acetylated kraft lignin(AL-NPs)was used as filler during synthesizing UV-shielding films loaded with various amounts(1–5 wt.%)of AL-NPs.Kraft lignin was acetylated through a simple and fast microwave-assisted process using acetic acid as a solvent and acetylating agent.The physicochemical and morphological characteristics of the prepared films were evaluated using different methods,including scanning electron microscopy(SEM),Fourier Transform Infrared Spectroscopy(FTIR),X-ray diffraction analysis(XRD),mechanical testing and contact angle measurement.The UV-Vis spectroscopy optical investigation of the prepared films revealed that AL-NPs in the CA matrix showed strong UV absorption.This feature demonstrated the effectiveness of our research in developing UV-resistant bio-based polymer films.Hence,the prepared films can be considered as successful candidates to be applied in packaging applications.
