Numerical Study on Transonic Flow with Local Occurrence of Non-Equilibrium Condensation

Characteristics of transonic flow over an airfoil are determined by a shock wave standing on the suction surface. In this case, the shock wave/boundary layer interaction becomes complex because an adverse pressure gradient is imposed by the shock wave on the boundary layer. Several types of passive control techniques have been applied to shock wave/boundary layer interaction in the transonic flow. Furthermore, possibilities for the control of flow fields due to non-equilibrium condensation have been shown so far and in this flow field, non-equilibrium condensation occurs across the passage of the nozzle and it causes the total pressure loss in the flow field. However, local occurrence of non-equilibrium condensation in the flow field may change the characteristics of total pressure loss compared with that by non-equilibrium condensation across the passage of flow field and there are few for researches of locally occurred non-equilibrium condensation in a transonic flow field. The purpose of this study is to clarify the effect of locally occurred non-equilibrium condensation on the shock strength and total pressure loss on a transonic internal flow field with circular bump. As a result, it was found that shock strength in case with local occurrence of non-equilibrium condensation is reduced compared with that of no condensation. Further, the amount of increase in the total pressure loss in case with local occurrence of non-equilibrium condensation was also reduced compared with that by non-equilibrium condensation across the passage of flow field.

Facile synthesis of hierarchical NaX zeolite from natural kaolinite for efficient Knoevenagel condensation

Zeolite catalysts have found extensive applications in the synthesis of various fine chemicals.However,the micropores of zeolites impose diffusion limitations on bulky molecules,greatly reducing the catalytic efficiency.Herein,we explore an economic and environmentally friendly method for synthesizing hierarchical NaX zeolite that exhibits improved catalytic performance in the Knoevenagel condensation reaction for producing the useful fine chemical 2-cyano-3-phenylacrylate.The synthesis was achieved via a low-temperature activation of kaolinite and subsequent in-situ transformation strategy without any template or seed.Systematic characterizations reveal that the synthesized NaX zeolite has both intercrystalline and intra-crystalline mesopores,smaller crystal size,and larger external specific surface area compared to commercial NaX zeolite.Detailed mechanism investigations show that the inter-crystalline mesopores are generated by stacking smaller crystals formed from in-situ crystallization of the depolymerized kaolinite,and the intra-crystalline mesopores are inherited from the pores in the depolymerized kaolinite.This synthesis strategy provides an energy-saving and effective way to construct hierarchical zeolites,which may gain wide applications in fine chemical manufacturing.

Chromatin condensation but not DNA integrity of pig sperm is greater in the sperm-rich fraction

Background Protamination and condensation of sperm chromatin as well as DNA integrity play an essential role during fertilization and embryo development.In some mammals,like pigs,ejaculates are emitted in three separate fractions:pre-sperm,sperm-rich(SRF)and post sperm-rich(PSRF).These fractions are known to vary in volume,sperm concentration and quality,as well as in the origin and composition of seminal plasma(SP),with differences being also observed within the SRF one.Yet,whether disparities in the DNA integrity and chromatin condensation and pro-tamination of their sperm exist has not been interrogated.Results This study determined chromatin protamination(Chromomycin A3 test,CMA_(3)),condensation(Dibromobi-mane test,DBB),and DNA integrity(Comet assay)in the pig sperm contained in the first 10 m L of the SRF(SRF-P1),the remaining portion of the sperm-rich fraction(SRF-P2),and the post sperm-rich fraction(PSRF).While chromatin protamination was found to be similar between the different ejaculate fractions(P>0.05),chromatin condensation was seen to be greater in SRF-P1 and SRF-P2 than in the PSRF(P=0.018 and P=0.004,respectively).Regarding DNA integrity,no differences between fractions were observed(P>0.05).As the SRF-P1 has the highest sperm concentra-tion and ejaculate fractions are known to differ in antioxidant composition,the oxidative stress index(OSi)in SP,calcu-lated as total oxidant activity divided by total antioxidant capacity,was tested and confirmed to be higher in the SRF-P1 than in SRF-P2 and PSRF(0.42±0.06 vs.0.23±0.09 and 0.08±0.00,respectively;P<0.01);this index,in addition,was observed to be correlated to the sperm concentration of each fraction(Rs=0.973;P<0.001).Conclusion While sperm DNA integrity was not found to differ between ejaculate fractions,SRF-P1 and SRF-P2 were observed to exhibit greater chromatin condensation than the PSRF.This could be related to the OSi of each fraction.

Controllable Condensation of Aromatics and Its Mechanisms in Carbonization

In order to obtain liquefied products with higher yields of aromatic molecules to produce mesophase pitch,a good understanding of the relevant reaction mechanisms is required.Reactive molecular dynamics simulations were used to study the thermal reactions of pyrene,1-methylpyrene,7,8,9,10-tetrahydrobenzopyrene,and mixtures of pyrene with 1-octene,cyclohexene,or styrene.The reactant conversion rates,reaction rates,and product distributions were calculated and compared,and the mechanisms were analyzed and discussed.The results demonstrated that methyl and naphthenic structures in aromatics might improve the conversion rates of reactants in hydrogen transfer processes,but their steric hindrances prohibited the generation of high polymers.The naphthenic structures could generate more free radicals and presented a more obvious inhibition effect on the condensation of polymers compared with the methyl side chains.It was discovered that when different olefins were mixed with pyrene,1-octene primarily underwent pyrolysis reactions,whereas cyclohexene mainly underwent hydrogen transfer reactions with pyrene and styrene,mostly producing superconjugated biradicals through condensation reactions with pyrene.In the mixture systems,the olefins scattered aromatic molecules,hindering the formation of pyrene trimers and higher polymers.According to the reactive molecular dynamics simulations,styrene may enhance the yield of dimer and enable the controlled polycondensation of pyrene.

Supersonic expansion and condensation characteristics of hydrogen gas under different temperature conditions

This paper introduced supersonic expansion liquefaction technology into the field of hydrogen liquefaction.The mathematical model for supersonic condensation of hydrogen gas in a Laval nozzle model was established.The supersonic expansion and condensation characteristics of hydrogen gas under different temperature conditions were investigated.The simulation results show that the droplet number rises rapidly from 0 at the nozzle throat as the inlet temperature increases,and the maximum droplet number generated is 1.339×10^(18)kg^(-1)at inlet temperature of 36.0 K.When hydrogen nucleation occurs,the droplet radius increases significantly and shows a positive correlation with the increase in the inlet temperature,and the maximum droplet radii are 6.667×10^(-8)m,1.043×10^(-7)m,and 1.099×10^(-7)m when the inlet temperature is 36.0 K,36.5 K,and 37.0 K,respectively.The maximum nucleation rate decreases with increasing inlet temperature,and the nucleation region of the Laval nozzle becomes wider.The liquefaction efficiency can be effectively improved by lowering the inlet temperature.This is because a lower inlet temperature provides more subcooling,which allows the hydrogen to reach the thermodynamic conditions required for large-scale condensation more quickly.

Finite-Time Thermodynamic Simulation of Circulating Direct Condensation Heat Recovery on Chillers

A time series model is used in this paper to describe the progress of circulating direct condensation heat recovery of the compound condensing process (CCP) which is made of two water cooling condensing processes in series for a centrifugal chiller in the paper. A finite-time thermodynamics method is used to set up the time series simulation model. As a result, an upper bound of recoverable condensation heat for the compound condensing process is obtained which is in good agreement with experimental result. And the result is valuable and useful to optimization design of condensing heat recovery.

Generalized polynomial chaos expansion by reanalysis using static condensation based on substructuring

This paper presents a new computational method for forward uncertainty quantification(UQ)analyses on large-scale structural systems in the presence of arbitrary and dependent random inputs.The method consists of a generalized polynomial chaos expansion(GPCE)for statistical moment and reliability analyses associated with the stochastic output and a static reanalysis method to generate the input-output data set.In the reanalysis,we employ substructuring for a structure to isolate its local regions that vary due to random inputs.This allows for avoiding repeated computations of invariant substructures while generating the input-output data set.Combining substructuring with static condensation further improves the computational efficiency of the reanalysis without losing accuracy.Consequently,the GPCE with the static reanalysis method can achieve significant computational saving,thus mitigating the curse of dimensionality to some degree for UQ under high-dimensional inputs.The numerical results obtained from a simple structure indicate that the proposed method for UQ produces accurate solutions more efficiently than the GPCE using full finite element analyses(FEAs).We also demonstrate the efficiency and scalability of the proposed method by executing UQ for a large-scale wing-box structure under ten-dimensional(all-dependent)random inputs.

New Strategy Leverages Lignin Condensation for Biomass Utilization

There is an old saying in the biorefining industry that“You can make anything from lignin except money.”This bio-based compound is abundant and full of potential,but commercializing it remains a challenge.This may no longer be the case soon with an innovative approach by chemists from the Dalian Institute of Chemical Physics(DICP)of the Chinese Academy of Sciences and their colleagues to harness lignin condensation–often considered a nuisance–for efficient utilization of lignocellulose.

Effect of Nozzle Inlet Shape on Annular Swirling Flow with Non-Equilibrium Condensation

Recently,by combining a swirl flow with non-equilibrium condensation phenomena of condensate gas generated in a supersonic flow,a separating and extracting techniques of condensate gas have been developed.This technique can reduce the size of the device and don't use chemicals.In the present study,by using a non-equilibrium condensation phenomenon of moist air occurred in the supersonic flow in the annular nozzle composed of an inher body and an outer nozzle with a swirl,the possibility of separation of the condensable gas and the effect of shape of nozzle inlet on the flow field were examined numerically.

The Effect of Non-equilibrium Condensation on the Drag Coefficient in a Transonic Airfoil Flow

In this study, a transonic flow past NACA0012 profile at angle of attack α=0^0 whose aspect ratio AR is 1.0 with non-equilibrium condensation is analyzed by numerical analysis using a TVD scheme and is investigated using an intermittent indraft type supersonic wind tunnel. Transonic flows of 0.78-0.90 in free stream Mach number with the variations of the stagnation relative humidity（φ0） are tested. For the same free stream Mach number, the increase in φ0 causes decrease in the drag coefficient of profile which is composed of the drag components of form, viscous and wave. In the case of the same Moo and To, for more than φ0=30%, despite the irreversibility of process in non-equilibrium condensation, the drag by shock wave decreases considerably with the increase of φ0. On the other hand, it shows that the effect of condensation on the drag coefficients of form and viscous is negligible. As an example, the decreasing rate in the drag coefficient of profile caused by the influence of non-equilibrium condensation for the case of M∞=0.9 and φ0 =50% amounts to 34%. Also, it were turned out that the size of supersonic bubble （that is, the maximum height of supersonic zone） and the deviation of pressure coefficient from the value for M=1 decrease with the increase of φ0 for the same M∞.

Effect of Non-Equilibrium Condensation of Moist Air on Unsteady Behaviour of Shock Waves around a Circular Arc Blade

The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan, compressor blades and butterfly valves, and this often causes serious problems such as the aeroacoustic noise, the vibration. In the transonic or supersonic flow where vapour is contained in the main flow, the rapid expansion of the flow may give rise to a non-equilibrium condensation. However, the effect of non-equilibrium condensation on the transonic internal flows around the airfoil has not yet been clarified satisfactorily. In the present study, the effect of non-equilibrium condensation of moist air on the self-excited shock wave oscillation on a circular arc blade was investigated numerically. The results showed that in the case with non-equilibrium condensation, frequencies of the flow oscillation became smaller than those without the non-equilibrium condensation.

Passive Control of Transonic Flow Fields with Shock Wave Using Non-equilibrium Condensation and Porous Wall

When non-equilibrium condensation occurs in a supersonic flow field, the flow is affected by the latent heat released. In the present study, in order to control the transonic flow field with shock wave, a condensing flow was produced by an expansion of moist air on a circular bump model and shock waves were occurred in the supersonic parts of the fields. Furthermore, the additional passive technique of shock / boundary layer interaction using the porous wall with a cavity underneath was adopted in this flow field. The effects of these methods on the shock wave characteristics were investigated numerically and experimentally. The result obtained showed that the total pressure loss in the flow fields might be effectively reduced by the suitable combination between non-equilibrium condensation and the position of porous wall.

Three-Dimensional Structure of Non-Equilibrium Homogeneous Condensation Flow in a Supersonic Rectangular Nozzle

Numerical simulations have been carried out for a supersonic three-dimensional rectangular arc nozzle, where a secondary flow toward the center of the curvature occurs due to the shape of the nozzle. It is known that secondary flow causes longitudinal vortices to form near the wall of the nozzle corner, making the nozzle outlet flow unstable and induces loss of transport energy. When the working fluid is a condensable gas with relatively large latent heat such as moist air or steam, rapid accelerated expansion in the nozzle causes non-equilibrium condensation due to supersaturation. After the release of latent heat during phase transition, nozzle flow continues expanding at an equilibrium saturation condition. In the absence of foreign particles, e.g. ions or dust particles, condensation nuclei are formed in the gas itself causing non-equilibrium homogeneous condensation. Supersonic nozzle flow properties vary considerably due to the occurrence of condensation phenomenon. The objective of this study is to investigate the effect of non-equilibrium homogeneous condensation on the longitudinal vortices which form in the range close to the corner of rectangular arc nozzle numerically.

The Effect of Non-Equilibrium Condensation on Supersonic Air Flows over Rectangular Cavities

Numerical simulations have been carded out for a supersonic two-dimensional flow over open, rectangular cavities （length-to-depth ratios are L/D = 1.0 and 3.0） in order to investigate the effect of non-equilibrium condensation of moist air on supersonic internal flows around the cavity for the flow Mach number 1.83 at the cavity entrance. In the present computational investigation, a condensing flow was produced by an expansion of moist air in a Laval nozzle. The computational results showed that the upstream traveling compression waves become weaker than those without the condensation. Consequently, the weaker compression waves cannot excite the shear layer strongly and amplitudes of oscillation in the cavity became smaller than those without the condensation. The occurrence of the non-equilibrium condensation in case of L/D = 1.0 affected strongly the amplitude and frequency of oscillation in the cavity compared with L/D = 3.0.

Control of Transonic Flow Fields Using Local Occurrence of Non-Equilibrium Condensation

Control of supersonic flow fields with shock wave is important for some industrial fields. There are many studies for control of the supersonic flow fields using active or passive control. When non-equilibrium condensation occurs in a supersonic flow field, the flow is affected by latent heat released. Many studies for the condensation have been conducted and the characteristics have been almost clarified. Further, it was found that non-equilibrium condensation can control the flow field. In these studies, the condensation occurs across the passage of the flow field and it causes the total pressure loss in the flow field. However, local occurrence of non-equilibrium condensation in the flow field may change the characteristics of total pressure loss compared with that by the condensation across the passage of the nozzle and there are few for researches of locally occurred non-equilibrium condensation in supersonic flow field. The purpose in the present study is to clarify the effect of local occurrence of non-equilibrium condensation on the transonic flow field in a nozzle with a circular bump. As a result, local occurrence of non-equilibrium condensation reduced the shock strength and total pressure loss in the transonic flow field by flowing the moist air from trailing edge of the circular bump to the mainstream.

Numerical Investigation on Wet Steam Non-equilibrium Condensation Flow in Turbine Cascade

Based on the two-phase wet steam flow with spontaneous condensation, experimental verification and flow analysis on nozzle and 2D cascade are carried out. The 3D Reynolds-Averaged gas-liquid two-phase flow control equation solver is explored with k-e-kp turbulence model. Furthermore, 3D flow numerical simulation on the last stage stator of the steam turbine is carried out. The results show that a sudden pressure rise on blade suction surface is mainly caused by the droplet growth in condensation flow. The more backward the condensation position is in cascade passage, the less the sudden pressure rise from condensation is, and the larger the nucleation rate is, the maximum under-cooling and the number of droplets per unit volume are. Interaction of condensation wave and shock wave has imposed greater influence on the parameters of the blade cascade outlet.

Preparation of waterborne polyurethane/β-cyclodextrin composite nanosponge by ion condensation method and its application in removing of dyes from wastewater

Currently,polymer nanosponges have received extensive attention.However,developing new synthetic techniques for novel nanosponges remains a challenge.Furthermore,to date,composite nanosponge adsorbents based on waterborne polyurethane(WPU)andβ-cyclodextrin(β-CD)have not been reported.Herein,a novel green method,ion condensation method,was developed in this study for the preparation of polymer nanosponge adsorbents for efficient removal of dyes from wastewater.Based on the principle of charge repulsion between nanoparticles to maintain emulsion stability,waterborne polyurethane/β-cyclodextrin composite nanosponges(WPU-x,y)were prepared by coagulating the emulsions synthesized from 2,2-dimethylolpropionic acid,polypropylene glycol and hexamethylene diisocyanate as raw materials in a mixture of hydrochloric acid and anhydrous ethanol.The structure and appearance of WPU-x,y were characterized by attenuated total reflectance Fourier transform infrared spectroscopy,thermal gravimetric analyzer,scanning electron microscope and mercury intrusion porosimetry.The adsorption capacity of WPU-x,y was tested by parameters such as cross-linking degree,β-CD dosage,contact time,initial dye concentration and p H value.The study found that WPU-4,4.62 had the best adsorption effect on methylene blue(MB),the maximum removal rate was 93.42%,and the maximum adsorption capacity was 136.03 mg·g^(-1).Moreover,the Sips isotherm and pseudo-second-order-model were suitable for MB adsorption.Therefore,this study provides some perspectives for the fabrication of nanosponge adsorbents.

Novel interface engineering of LDH-based materials on Mg alloy for efficient photocatalytic systems considering the geometrical linearity of condensed phosphates

This study presents a facile and rapid method for synthesizing novel Layered Double Hydroxide(LDH)nanoflakes,exploring their application as a photocatalyst,and investigating the influence of condensed phosphates'geometric linearity on their photocatalytic properties.Herein,the Mg O film,obtained by plasma electrolysis of AZ31 Mg alloys,was modified by growing an LDH film,which was further functionalized using cyclic sodium hexametaphosphate(CP)and linear sodium tripolyphosphate(LP).CP acted as an enhancer for flake spacing within the LDH structure,while LP changed flake dispersion and orientation.Consequently,CP@LDH demonstrated exceptional efficiency in heterogeneous photocatalysis,effectively degrading organic dyes like Methylene blue(MB),Congo red(CR),and Methyl orange(MO).The unique cyclic structure of CP likely enhances surface reactions and improves the catalyst's interaction with dye molecules.Furthermore,the condensed phosphate structure contributes to a higher surface area and reactivity in CP@LDH,leading to its superior photocatalytic performance compared to LP@LDH.Specifically,LP@LDH demonstrated notable degradation efficiencies of 93.02%,92.89%,and 88.81%for MB,MO,and CR respectively,over a 40 min duration.The highest degradation efficiencies were observed in the case of the CP@LDH sample,reporting 99.99%for MB,98.88%for CR,and 99.70%for MO.This underscores the potential of CP@LDH as a highly effective photocatalyst for organic dye degradation,offering promising prospects for environmental remediation and water detoxification applications.

In Tube Condensation:Changing the Pressure Drop into a Temperature Difference for a Wire-on-Tube Heat Exchanger

A theoretical study based on the Penalty factor(PF)method by Cavallini et al.is conducted to show that the pressure drop occurring in a wire-on-tube heat exchanger can be converted into a temperature difference for two types of refrigerants R-134a and R-600a typically used for charging refrigerators and freezers.The following conditions are considered:stratified or stratified-wavyflow condensation occurring inside the smooth tube of a wire-on-tube condenser with diameter 3.25,4.83,and 6.299 mm,condensation temperatures 35℃,45℃,and 54.4℃ and cover refrigerant massflow rate spanning the interval from 1 to 7 kg/hr.The results show that the PF variation is not linear with vapor quality and attains a maximum when the vapor quality is 0.2 and 0.18 for the R-134a and R-600a refrigerants,respectively.The PF increases with the refrigerant massflow rate if the inner diameter and saturation temperature constant,and it decreases on increasing the inner diameter to 6.299 mm for constant refrigerant massflow rate and saturation temperature.The PF for R-600a is higher than that for R-134a due to the lower saturation pressure in thefirst case.Furthermore,a stratifiedflow produces higher PF in comparison to the annularflow due to the effect of the surface tension.

Numerical study of the deep removal of R134a from non-condensable gas mixture by cryogenic condensation and de-sublimation

Nowadays,the limits on greenhouse gas emissions are becoming increasingly stringent.In present research,a two-dimensional numerical model was established to simulate the deep removal of 1,1,1,2-tetrafluoroethane(R134a)from the non-condensable gas(NCG)mixture by cryogenic condensation and de-sublimation.The wall condensation method was compiled into the Fluent software to calculate the condensation of R134a from the gas mixture.Besides,the saturated thermodynamic properties of R134a under its triple point were extrapolated by the equation of state.The simulation of the steam condensation with NCG was conducted to verify the validity of the model,the results matched well with the experimental data.Subsequently,the condensation characteristics of R134a with NCG and the thermodynamic parameters affecting condensation were studied.The results show that the section with relatively higher removal efficiency is usually near the inlet.The cold wall temperature has a great influence on the R134a removal performance,e.g.,a 15 K reduction of the wall temperature brings a reduction in the outlet R134a molar fraction by 85.43%.The effect of changing mass flow rate on R134a removal is mainly reflected at the outlet,where an increase in mass flow rate of 12.6% can aggravate the outlet molar fraction to 210.3% of the original.The research can provide a valuable reference for the simulation of the deep removal of various low-concentration gas using condensation and de-sublimation methods.