Process of Microcellular Propellants with Adjustable Skin Thickness

Microcellular propellants show a vast applicable prospect due to their special shell-pore structure. The effects of saturation pressure and desorption time on skin thickness are studied. The skin thickness is observed and measured using scanning electron microscope (SEM). The results show that the skin thickness decreases when saturation pressure increases from 15 MPa to 30 MPa. In contrast, the skin thickness increases as the desorption time changes from 2 min to 20 min.Therefore, the microcellular propellants with adjustable skin thickness can be obtained under the variable process conditions such as saturation pressure and desorption time.

Dispersion hydrophobic electrolyte enables lithium-oxygen battery enduring saturated water vapor

Li-O_(2) batteries gain widespread attention as a can didate for next-generati on energy storage devices due to their extraordinary theoretic specific energy.The semi-open structure of Li-O_(2) batteries causes many parasitic reactions,especially related to water.Water is a double-edged sword,which destroys Li anode and simultaneously triggers a solution-based pathway of the discharge product.In this work,hexamethyldisilazane(HMDS)is introduced into the electrolyte of an aprotic Li-O_(2) battery.HMDS has a strong ability to combine with a trace of water to gen erate a hydrophobic hexamethyldisiloxa ne(MM),which eliminates water from the electrolyte decomposition and then prevents the Li anode from producing the insulating LiOH with water.In this case,the hydrophobic MM disperses in the ether-based electrolyte,forming a dispersion hydrophobic electrolyte.This electrolyte can anchor water from the environment on the cathode side,which triggers a solution-based pathway and regulates the growth morphology of the discharge product and consequently increases the discharge capacity.Compared with the Li-O_(2) battery without the HMDS,the HMDS-containing Li-O_(2) battery contributes an about 13-fold increase of cyclability(400 cycles,1800 h)in the extreme environment of saturated water vapor.This work opens a new approach for directly operating aprotic Li-O_(2) batteries in ambient air.

Modeling and Simulation of Lithium Vacuum Evaporation Process Using COMSOL Multiphysics

Based on the COMSOL Multiphysics simulation software,this study carried out modeling and numerical simulation for the evaporation process of liquid metal lithium in the vacuum free molecular flow state.The motion of lithium atoms in the evaporation process was analyzed through a succession of studies.Based on the available experimental values of the saturated vapor pressure of liquid metal lithium,the relationship between saturated vapor pressure and temperature of liquid lithium in the range of 600 K-900 K was obtained.A two-dimensional symmetric model(3.5 mm×20 mm) was established to simulate the transient evaporation process of liquid lithium at wall temperatures of 750 K,780 K,800 K,810 K,825 K,and 850 K,respectively.The effects of temperature,the evaporation coefficient,back pressure,and length-to-diameter ratio on the evaporation process were studied;the variation trends and reasons of the molecular flux and the pressure during the evaporation process were analyzed.At the same time,the evaporation process under variable wall temperature conditions was simulated.This research made the evaporation process of liquid lithium in vacuum molecular flow clearer,and provided theoretical support for the space reactor and nuclear fusion related fields.

Data driven prediction of oil reservoir fluid properties

Accuracy of the fluid property data plays an absolutely pivotal role in the reservoir computational processes.Reliable data can be obtained through various experimental methods,but these methods are very expensive and time consuming.Alternative methods are numerical models.These methods used measured experimental data to develop a representative model for predicting desired parameters.In this study,to predict saturation pressure,oil formation volume factor,and solution gas oil ratio,several Artificial Intelligent(AI)models were developed.582 reported data sets were used as data bank that covers a wide range of fluid properties.Accuracy and reliability of the model was examined by some statistical parameters such as correlation coefficient(R2),average absolute relative deviation(AARD),and root mean square error(RMSE).The results illustrated good accordance between predicted data and target values.The model was also compared with previous works and developed empirical correlations which indicated that it is more reliable than all compared models and correlations.At the end,relevancy factor was calculated for each input parameters to illustrate the impact of different parameters on the predicted values.Relevancy factor showed that in these models,solution gas oil ratio has greatest impact on both saturation pressure and oil formation volume factor.In the other hand,saturation pressure has greatest effect on solution gas oil ratio.

Enhanced application for FSRU recondensing equipment during periods of low or no gas send out to minimize LNG cargo losses

Most modern floating storage and regasification units(FSRU)are fitted with recondensing equipment that feed condensed boil-off gas(BOG)to the regasification unit in addition to a stream of liquefied natural gas(LNG)extracted from the cargo tanks.Use of the recondenser during regasification operations reduces gas losses on FSRU.It does so by avoiding consumption of excess BOG,with no associated commercial benefit,in gas combustion units(GCU),steam dumps,flares etc.Here we consider the benefits of also using the recondenser in recirculation mode,returning condensed BOG to the cargo tanks in the form of slightly warmed LNG.Such recirculation can be beneficial during periods of low or no gas send out from the FSRU,often achieving significant reductions in gas losses,although it is not standard practice in the industry to do so.Once regasification is halted not much BOG is required by the FSRU engine room,so the vessel must handle this excess.By condensing the BOG to LNG and returning it to the cargo tanks,the significant volume reduction involved has the beneficial impact of slowing down tank pressure increase.The saturated vapor pressure(SVP)of the LNG,linked to its composition and temperature,plays a key role in the boil-off rate and resulting cargo tank pressure changes.Detailed analysis is provided to explain how using the FSRU recondenser in recirculation mode can be best exploited by considering the prevailing fill levels,temperatures and pressures in each of the cargo tanks,and returning the condensed LNG preferentially to certain tanks.FSRU efficiency can be improved,gas losses and emissions can be reduced,and more cargo sold by exploiting the capabilities of the FSRU recondenser in recirculation mode.Running the FSRU in recirculation mode requires no equipment modifications to standard recondensers,neither does it increase FSRU operating costs.