• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Discharge characteristics and reactive species production of unipolar and bipolar nanosecond pulsed gas–liquid discharge generated in atmospheric N2

    2021-09-10 09:26:38JianpingLIANG梁建平XiongfengZHOU周雄峰ZiluZHAO趙紫璐HaoYUAN袁皓HongliWANG王紅麗WenchunWANG王文春andDezhengYANG楊德正
    Plasma Science and Technology 2021年9期
    關鍵詞:建平

    Jianping LIANG (梁建平),Xiongfeng ZHOU (周雄峰),Zilu ZHAO (趙紫璐),Hao YUAN (袁皓),Hongli WANG (王紅麗),Wenchun WANG (王文春) and Dezheng YANG (楊德正)

    Key Lab of Materials Modification (Dalian University of Technology),Ministry of Education,Dalian 116024,People’s Republic of China

    Abstract In this paper,unipolar pulse (including positive pulse and negative pulse) and bipolar pulse voltage are employed to generate diffuse gas–liquid discharge in atmospheric N2 with a trumpetshaped quartz tube.The current–voltage waveforms,optical emission spectra of excited state active species,FTIR spectra of exhaust gas components,plasma gas temperature,and aqueous H2O2,NO? 2 ,and NO?3 production are compared in three pulse modes,meanwhile,the effects of pulse peak voltage and gas flow rate on the production of reactive species are studied.The results show that two obvious discharges occur in each voltage pulse in unipolar pulse driven discharge,differently,in bipolar pulse driven discharge,only one main discharge appears in a single voltage pulse time.The intensities of active species (OH(A),and O(3p)) in all three pulsed discharge increase with the rise of pulse peak voltage and have the highest value at 200 ml min?1 of gas flow rate.The absorbance intensities of NO2 and N2O increase with the increase of pulse peak voltage and decrease with the increase of gas flow rate.Under the same discharge conditions,the bipolar pulse driven discharge shows lower breakdown voltage,and higher intensities of excited species(N2(C),OH(A),and O(3p)),nitrogen oxides(NO2,NO,and N2O),and higher production of aqueous H2O2,NO? 2 ,and NO?3 compared with both unipolar positive and negative discharges.

    Keywords:nanosecond pulse discharge,gas–liquid discharge,optical emission spectra,reactive species,FTIR spectra

    1.Introduction

    Recently,nanosecond pulsed gas–liquid discharge(NPG-LD)with dielectric-free electrode configuration in atmospheric pressure has been widely used in many applications,including sterilization[1],water purification[2–4],biomedicine[5],and material treatment [6].Compared with the sinusoidal discharge,the discharges driven by nanosecond pulse power supply are prone to cause lower heat and higher energy efficiency for producing reactive species [7–9].For example,Xuet alhave reported that the pulsed plasma jet induces higher concentrations of the aqueous H2O2,OH/,/NOO?and has stronger bacterial inactivation compared with sinusoidal plasma jet under the same discharge power[9].Nerettiet alalso found that the gas–liquid discharge(G-LD) generated by nanosecond pulse power is more homogeneous,has lower gas temperature,and can produce higher concentration of H2O2under the same discharge power[10].The nanosecond pulse voltage characterized by the rapid rising and falling time (~5–50 ns) can preclude the liquid deformation caused by surface charge accumulation,and by short pulse duration time (~10–100 ns) can avoid the undesired spark discharge [10,11].

    Figure 1.The experimental setup of NPG-LD.

    Many researches have used nanosecond pulse power supply to obtain G-LD with a spatial homogeneity and efficient production of reactive species at atmospheric pressure[12,13].It has been found that the efficiency of reactive species production and water treatment depends on the pulse polarity when NPG-LD is excited by unipolar pulse.Thagardet al[14]found that in the unipolar positive pulsed discharge,the production of H2O2relies on the solution pH,whereas in the unipolar negative pulsed discharge,the production of H2O2is lower and depends on the liquid conductivity.Hamdanet al[15] found that the change of the solution conductivity and pH,and concentrations of H2O2,NO?3,and NO?2are similar in both positive and negative polarity pulsed discharges.However,negative pulsed discharge has higher degradation rate of methylene blue,which is attributed to that the untreated solution at bottom can flow to the plasma–liquid interface at higher flow rate in negative pulsed discharge.

    In recent years,bipolar pulse voltage,characterized by a negative pulse following a positive pulse alternatingly,has also been used to obtain NPG-LD.For example,Tanget al[16] used bipolar pulsed DBD for regenerating granular activated carbon to degrade phenol in water,and they found that phenol degradation efficiency can achieve 87% after 100 min of treatment and regeneration efficiencies of the granular activated carbon is increased with enhancing plasma treatment time.Our group also used a bipolar nanosecond pulse power to generate a stable bubble gas discharge in water,in which the H2O2energy yield with Ar bubble reaches 3.04 g kW h?1[17].Although different pulse voltage modes are widely used to generate G-LD in atmosphere pressure,it has been rarely reported to compare the effects among these three pulse voltage modes on the excitation of G-LD.

    Currently,obtaining a stable G-LD plasma source with large plasma volume and large plasma–liquid interface is an important challenge from the requirement of technological point.In this study,based on the typical needle-water discharge structure,a self-designed trumpet tube is added in the discharge reactor.On one hand,the addition of trumpet tube avoids the interference effect of ambient air on discharge.On the other hand,the shape of trumpet tube is beneficial for increasing the plasma source volume.According to previous discussion,the mode of nanosecond pulse supply greatly influences on the discharge properties.To optimize the discharge device,the effects of pulse mode,including unipolar negative pulse voltage,unipolar positive pulse voltage,and bipolar pulse voltage,on the discharge properties and production efficiency of active species of NPG-LD are systematically compared.The comparative studies about the plasma characteristic including electrical behavior and plasma gas temperature in three NPG-LD modes are carried.By using optical emission spectra (OES) and FTIR spectra,the effects of pulse voltage modes,gas flow rate,and pulse peak voltage on spectra intensities of gaseous reactive component are investigated.The solution pH value,and concentration of aqueous reactive species (H2O2,NO?2,and NO?3) are measured to discuss the different water activation mechanisms in three pulsed mode NPG-LDs.

    2.Experimental setup

    Figure 1 shows the experimental setup,which is similar with our previous study [18].For the discharge reactor,a trumpet quartz tube is penetrated into a quartz cup (the 25 mm inner diameter and 2 mm thickness) filled with 10 ml deionized water and fixed on a grounded metal electrode.The largest and smallest dimeters of trumpet quartz tube are 5 mm and 25 mm,respectively,and the height of the conical part is 10 mm.A high-voltage (HV) copper tube electrode (2 mm inner diameter,3 mm outer diameter,and the smaller diameter of conic part of HV electrode is 1.5 mm)is fixed on the axial direction of a trumpet quartz tube and distances 4 mm from the liquid surface.The pure N2is controlled by a mass flow controller,and enters into discharge reactor through the HV electrode and flows out from the branch tube of the quartz tube.Before each discharge,the working gas pre-feds for 5 min to remove the air in the tube.

    Figure 2.(a) The schematic diagram of the pulsed power supply circuit.Examples of resulting waveforms of(b)bipolar pulse,(c)unipolar positive,and (d) unipolar negative pulse voltage.

    The schematic diagram of the nanosecond pulse power supply circuit is shown in figure 2(a),which has two types:positive pulse circuits and negative pulse circuits.Each circuit consists of a rotary spark gap switch,a pulsed capacitor(Cp),and a storage capacitor(C),and theCpis used as the charged storage capacitor.Spark gap is an effective way of producing both fast rise and fall times of HV signals.The single-phase AC 220 V input is boosted by a HV transformer and then rectified to obtain a positive and negative output dc highvoltage.The dc high-voltage charges the energy storage capacitor (C) through the rotary spark gap switch to charge the pulse capacitor (Cp),and then discharges to the load through the rotary spark gap switch,so that the load obtains a high pulse voltage.When both positive and negative circuits are connected at the same time,a bipolar pulse voltage(shown in figure 2(b)) can be exported to discharge reactor.At this case,the switches of the positive and negative pulse circuits are not turned on at the same time.When positive or negative circuits are individually connected to power,the unipolar positive or negative pulse voltage can be exported to discharge reactor (shown in figures 2(c) or (d)),respectively.The pulse frequency is adjusted by changing speed of the rotary spark gap.In order to maintain the same number of pulses,150 Hz of pulse repetition rate is used in both unipolar positive and negative pulsed modes and 75 Hz of pulse repetition rate is used in bipolar pulsed mode.The discharge images of three pulsed mode discharges are shown in figure 3,and captured by Cannon 70D digital camera with the 100 ms of exposure time.The discharges in all three pulsed modes have the strongest intensity near the tips of the copper pipe,and then spread to liquid surface and fill the lower part of the trumpet quartz tube with a diffuse morphology.The discharge current and pulse voltage are measured by using an oscilloscope (Tektronix,Portland,OR,TDS5054B,500 MHz) with a current probe (Tektronix TCP312,100 MHz) and a 1:1000 HV probe (Tektronix P6015A,100 MHz),respectively.

    Figure 3.Images of(a)bipolar,(b)unipolar positive,and(c)unipolar negative NPG-LD under conditions of 200 ml min–1 gas flow rate and 30 kV pulse peak voltage.

    The head of the optical fiber is placed vertically to the axis of the quartz tube under all discharge conditions.The OES of plasma region is diagnosed by using a spectrometer(Andor SR750i,Andor technology,UK; sensitivity range 180–1000 nm,1200 g mm?1grating blazed at 500 nm,0.02 nm entrance slit)equipped with a CCD camera(Newton DU940P-BV,2048×512 pixels,500 ms exposure time).The exhaust gas components of discharge reactor are analyzed by FTIR spectroscopy (Nico-LET iS10; Thermo scientific,Madison,WI) through guiding exhaust gas into absorption pool with an absorption length of 2.4 m [18].In order to eliminate the interference of water,the anhydrous CaCl2was selected as the desiccant to remove the water in the exhaust gas before analysis.After each discharge treatment,the liquid pH is immediately detected by a pH meter (Sartorius,PB-10,Germany).The aqueous H2O2concentration is measured by the titanium sulfate spectrometric method.The concentration of NO?2is quantified by the Griess–Saltzman method,and the concentration of NO?3is quantified by the 2,6-dimenthylephenol spectrometric method.All detailed measurement information of H2O2,NO?2,and NO?3can be found in the previous works [18,19].

    3.Results and discussion

    3.1.Electrical characteristics of the NPG-LDs excited by unipolar and bipolar modes

    Figures 4(a) and (b) show the waveforms of pulse voltageUand discharge currentIof unipolar positive and unipolar negative NPG-LD,respectively.Figures 4(c) and (d) show pulse voltageUand discharge currentIwaveforms of bipolar positive pulse and negative pulse of bipolar NPG-LD,respectively.The experimental conditions are 200 ml min?1gas flow rate and 30 kV pulse peak voltage.As shown in figures 4(a) and (b),the discharge current waveforms of unipolar positive and unipolar negative NPG-LDs have the similar shape except the opposite polarity.Two main discharge current peaks appear in both pulse voltage rising time and falling time of each pulse voltage.The maximum peak currents for both unipolar positive and negative NPG-LD are both about 3 A.When bipolar pulse voltage is used,it can be found that the breakdown process in bipolar pulsed discharge is completely different.According to figures 4(c) and (d),only one main discharge current peak appeared in a single voltage pulse time.Also,the maximum peak current (6 A) is much higher.Besides,it is found that the breakdown voltages in unipolar positive and negative NPG-LD are about 21 kV,while the breakdown voltage in bipolar NPG-LD is about 19 kV.

    The different current waveforms and breakdown voltages between unipolar and bipolar pulse modes are related to the different discharge processes.When discharge is driven by both unipolar positive and negative pulse voltage,two main discharge current peaks appear in each pulse,which suggests that two discharges occur per pulse voltage.The similar behaviors have been found in other works which reported that the second current peak is caused by charge accumulation on dielectric surface in the first discharge [12,20–22].In this study,it should be noted that the quartz tube in discharge reactor is inserted into water,which is indirectly contacted with grounded electrode.In the first discharge,some charge particles can accumulate on the quartz surface.The second discharge current would be generated when potential difference between the discharge electrode and charged quartz surface is sufficient.While the charged particles accumulated on surface of quartz tube can induce opposite electric field,which results in the decrease of the electrical field intensity during the discharge period [22].As for bipolar pulse,only one main discharge current peak in a single pulse suggests that one discharge occurred per pulse voltage.This phenomenon of the secondary discharge disappearing per pulse voltage in bipolar pulsed discharge is consistent with previously reported researches [16,23].As for bipolar pulse voltage,it is a negative polarity pulse followed by a positive polarity pulse alternately.During bipolar pulsed discharge process,the charges in previous pulse voltage accumulate on quartz tube surface.When voltage polarity changes,the direction of electric field caused by charges in previous pulse is the same as the electric field generated by following pulse,and hence it results in stronger electric field and lower breakdown voltage.

    Figure 4.Pulse voltage U and discharge current I waveforms of unipolar(a)positive pulse and(b)negative pulse discharge,and bipolar pulse discharge in (c) positive pulse and (d) negative pulse.

    Figure 5.The OES in the ranges of 300–450 nm and 777–778 nm for bipolar NPG-LD.

    3.2.OES characteristic of the NPG-LDs

    Gaseous active species have the important influences on the generation of secondary aqueous active species and strongly affect water treatment efficiency [24].Figure 5 presents the OES in the ranges of 300–450 nm and 777–778 nm for bipolar NPG-LD under 30 kV pulse peak voltage and 200 min l?1gas flow rate.The OES in both unipolar positive and negative discharges(not shown)are similar with those of bipolar discharge; the detailed comparison is given in the later.As shown in figure 5,the second positive bands N2(C–B)are the dominated,and relatively weak spectra lines including OH(A–X)and O(3p–3s,777 nm)are also identified.

    Figures 6(a)–(c) show emission intensities of N2(C–B),OH(A–X),and O(777 nm) of unipolar (both positive and negative pulses)and bipolar discharges varied as a function of pulse peak voltage,respectively,under the condition of 100 ml min?1gas flow rate.The OES reflect the transition between two states of active species,thus the OES intensity could be used to represent the relative concentration of active species for a qualitative analysis [25,26].In figures 6(a)–(c),the intensities of N2(C–B),OH(A–X),and O(3p–3s) in all three pulsed discharges rise as pulse peak voltage increased,indicating that higher pulse peak voltage,the more excited states N2(C),OH(A),and O(3p).As for those species,the excited states of OH(A),N2(C),and O(3p)are mainly formed by the collision of energetic electron with H2O molecules(R1),N2(R2),and O2molecules (R3),respectively.Higher pulse voltage provides more energy for the reactor,improves the average strength of the electrical field and electron density,and increases higher productions of OH(A),N2(C),and O(3p) [26]

    Figure 6.Effects of pulse peak voltage on the emission intensities of(a)N2(C–B,337 nm),(b)OH(A–X,309 nm)and(c)O(3p–3s,777 nm).

    Figures 7(a)–(c) shows the emission intensities of N2(C–B,337 nm),OH(A–X,309 nm),and O(3p–3s,777 nm)of unipolar (both positive and negative pulses) and bipolar discharges varied as a function of gas flow rate,respectively,under the condition of 30 kV pulse peak voltage.As shown in figure 7(a),the emission intensities of N2(C–B) in all three pulse mode discharges decrease with rising gas flow rates.However,in figures 7(b) and (c),the emission intensities of OH(A–X,309 nm)and O(3p–3s,777 nm)enhance firstly with rising the gas flow rate from 100 to 200 ml min?1,and then decrease when gas flow rate exceeds 200 ml min?1.The weaker emission intensities of N2(C–B)caused by higher gas flow are also found in atmospheric pressure dielectric barrier discharge reported by Zhouet al[27].It should be noted that the plasma is generated in a confined quartz tube in this study,the turbulence can be formed in the tube by the gas.Liet al[28] investigated the effects of gas flow rate on atmosphere pressure plasma confined in a dielectric tube.They reported that faster gas flow velocity results in more charge losses due to turbulence transport of charges to the wall,which would reduce the accumulation of molecules active.Therefore,the decrease of N2(C–B) is caused by more losses of charges at faster N2gas flow rate,which decreases the production of N2(C) via (R2).Besides,rising gas flow rate leads to the increased flow of turbulences in the quartz tube,which can bring more water molecules from liquid surface to the discharge region.The dissociation energy of H2O is about 5 eV,which is less than the excited N2(C) (10 eV) and N2(A)(~5.16 eV)energy.Hence,the H2O can be dissociated by the excited state N2((R4)and(R5))[11].When the gas flow rate increases in the small flow rate range (100–200 ml min?1),increasing a little of water molecules enhances the collision between the H2O and high-energy species (like energy electron,excited state moleculeN2*),which leads to produce more OH(A) and O(3p) via (R4)–(R6) [29].However,as the gas flow rate further increases,much higher content of water vapor will have a quenching effect on the discharge due to its electronegativity,which can decrease discharge intensity,and hence decrease the production of OH(A) and O(3p)

    Figure 7.Effects of gas flow rate on the emission intensities of (a) N2(C–B,337 nm),(b) OH(A–X,309 nm) and (c) O(3p–3s,777 nm).

    Table 1.The intensities of N2(C–B,337 nm),OH(A–X,309 nm),and O(3p–3s,777 nm) in three discharge modes.

    In order to compare three pulse modes under the same discharge power,the 30 kV pulse peak voltage is chosen in bipolar pulse mode and 33 kV pulse peak voltage is chosen in both unipolar pulse modes.Under this condition,the power of three pulsed discharges is 0.74 W.The intensities of N2(C–B,337 nm),OH(A–X,309 nm),and O(3p–3s,777 nm) in three discharge modes are counted in table 1.It is clear that,as for the unipolar pulse mode,the polarity of pulse voltage has little effect on the excited state of active species production,and the emission intensities of those active species in unipolar positive NPG-LD are slightly higher than those in unipolar negative NPG-LD.The results are similar to the work of Hamdanet al[15] who reported that the concentration of gaseous reactive nitrogen and oxygen species produced by both unipolar positive and negative pulse polarities driven discharge in-contact with water is similar.However,under the same gas flow rate and pulse peak voltage,the intensities of N2(C),OH(A),and O(3p) emitted from bipolar NPG-LD are much higher than those of unipolar (both the positive and negative) NPG-LDs.It indicates that bipolar pulse discharge is beneficial for the generation of active species.The reason is that,compared with the unipolar NPG-LD,the bipolar pulse is more efficient for delivering the energy to discharge region,and consequently increasing the electrical field strength and electron density [30].It is confirmed by the results that the current value in bipolar NPG-LD is much higher than those in the unipolar NPG-LD (figure 4).Thus,higher electrical field and larger electron density in the bipolar NPG-LD lead to more production of OH(A),N2(C),and O(3p).

    Figure 8.FTIR spectra of effluent gas components from unipolar positive pulse,unipolar negative pulse,and bipolar NPG-LD at 200 ml min?1 gas flow rate and 30 kV pulse peak voltage.

    Table 2.The intensities of NO2 and N2O in three discharge modes.

    Figure 8 shows FTIR spectra of effluent gas components of unipolar positive,unipolar negative,and bipolar NPG-LDs at 30 kV pulse peak voltage and 200 ml min?1gas flow rate.In both unipolar negative and positive discharges,the main products are N2O and NO2,almost no NO can be detected.In bipolar discharge,NO,N2O,and NO2can all be detected.Also,from table 2,it is found that the absorbance intensities of both N2O and NO2in bipolar pulse mode are much higher than those of both positive and negative discharges under the same discharge power.During discharge process,the nitrogen oxide (N2O and NO) can be produced by the (R7) and (R8)[31],and the NO is easily oxidized by O and OH to form NO2(R9) or HNO2(R10) [31].Compared with bipolar pulse mode,lower excitedN2*and O can be produced in unipolar pulse mode (figures 6 and 7),and hence forming lower N2O and NO2.NO is not detected in unipolar pulsed modes,this is caused by the following reason:the production of NO formed in unipolar pulsed modes is low,and almost all NO are converted to NO2or HNO2

    Figure 9.The effects of pulse peak voltage on the absorbance intensities of (a) NO2 and (b) N2O.

    Figure 10.The effects of gas flow rate on the absorbance intensities of (a) NO2 and (b) N2O.

    Figures 9(a) and(b) show that the absorbance intensities of N2O and NO2varied as a function of pulse peak voltage,respectively,at 200 ml min?1gas flow rate.It is obvious to find that the absorbance intensities of N2O and NO2increase in all three pulse mode discharges when pulse peak voltage is increased,which is consistent with the change of N2(C–B)in figure 6.In addition,figures 10(a) and (b) show that the absorbance intensities of N2O and NO2varied as a function of gas flow rate,respectively,at 30 kV pulse peak voltage.It is found that the absorbance intensities of N2O and NO2decrease when gas flow rate is raised in all three pulse mode discharges,which is also consistent with the change of N2(C–B) in figure 7.Combining with the previous results,it is suggested that increasing pulse voltage and decreasing gas flow are beneficial for producing excitedN*2,which further in crease the production of nitrogen oxide.

    3.3.Plasma temperature of NPG-LDs excited by unipolar and bipolar modes

    The gas temperature is a very important parameter of plasma that affects the chemical reaction pathways and final products,and subsequently affects the performance of water treatment applications [32].The rotational temperature (Trot) of N2(C)molecule is approximately equal to the gas temperature if the next two requirements are satisfied [8,33].First,the relaxation time (τRT) of equilibrium between translation and rotation of N2(C) achieved via collision,is less than or equal to the lifetime (τ0) of N2(C) that has considered the quenched process in atmospheric pressure.Second,the excited state N2(C) are mainly generated by the direct electron excitation of ground state N2(X).In nanosecond pulsed discharge,the τRTis in the order of ns (1–3 ns) due to high frequent collision,which is much lower than τ0in the order of several ten ns[8].Besides,N2gas is used as working gas,the formation processes of excited sate N2(C) satisfy the second requirement.Therefore,in this study,theTrotof N2(C) can be approximately equal to the gas temperature.By using the SPECAIR software [34],theTrotand vibrational temperature(Tvib) can be obtained by comparing experimental spectra of N2(C–B,0–2) with a best simulated spectra.Figure 11 displays the experimental spectra and simulated spectra of N2(C–B,0–2).As shown in figure 11,theTvibandTrotof N2(C–B,0–2) are 3500 K and 360 K in bipolar NPG-LD,respectively,under the condition of 200 ml min?1gas flow rate and 30 kV pulse peak voltage.It indicates that gas temperature of bipolar pulse discharge plasma is 360 K.

    Figure 11.The experimental spectra of N2(C–B,0–2) and correspondingly simulated spectra under 30 kV pulse peak voltage and 200 ml min?1 gas flow rate.

    The effects of pulse voltage onTrotandTvibof unipolar positive pulse,unipolar negative,and bipolar NPG-LDs are shown in figure 12.It is shown that in all three discharge modes,theTrotalways maintain at a low level.When the pulse peak voltage enhances from 26 to 34 kV,theTrotin all three discharge modes only rise from 340 to 410 K.In comparison,theTrotin three pulsed discharge modes have a near value under same discharge conditions.The results indicate that the NPG-LD excited by whatever pulse modes has a weak gas heating effect.In the process of nanosecond pulse discharge,the main energy delivered to discharge is preferentially used to generate high-energy electrons rather than heating the ions and gas molecules[12,35].In addition,since time interval between two discharges is much longer than the duration time of nanosecond pulse at the low repetition,the gas can be cooled effectively,consequently,thermal instability can be effectively suppressed.Therefore,the NPGLDs excited by all pulse modes have relatively low gas temperature.Besides,it is found that the increased temperature of liquid treated by the discharge is less than 2 K under the all discharge conditions after 10 min discharge treatment,suggesting that the NPG-LDs have no obvious heating effect on liquid.

    According to figure 12(b),theTvibof NPG-LDs excited by all bipolar and unipolar pulse voltages rise with the increase of pulse voltage.Such an increase trend inTvibhas also been reported by Wanget al[36],the authors claimed that higher pulse voltage causes higher electron density,which increases frequent collisions between energy electrons and N2molecules.And thus,the population in high vibrational states will increase,consequently,resulting in a significant increase of the vibrational temperature.Also,Tvibare found much higher thanTrotin three pulse modes,which indicates that plasmas in all three pulsed discharges have extremely high degree of the non-equilibrium [8,12].In comparison,as for unipolar pulse mode,voltage polarity has no appreciable influence onTvibunder a certain pulse voltage.However,Tvibin bipolar pulse mode is about 300 K higher in bipolar pulse mode than that in unipolar pulse mode.This is because the population quenching between vibrational levels at excited electronic states is less sufficient than that of rotational levels due to bigger vibrational gaps [37].Under the same discharge condition,the bipolar pulse mode induces more excited state N2,which leads to higherTvib,compared with both unipolar pulse modes.

    3.4.Analysis of solution pH value and production of NO3- ,NO2- , and H2O2

    To determine the effect of pulse polarity on the different characteristics of the G-LDs in N2,the aqueous long-lived species concentrations are measured.Figures 13(a)–(d) show that the solution pH value,and the concentrations of NO?3,,and H2O2varied as a function of plasma treatment time,respectively.The experimental conditions are 30 kV pulse voltage and 200 ml min?1gas flow rate.Based on figure 13(a),during the first 6 min,the pH values in both unipolar pulse modes are almost unchanged,and meanwhile in bipolar pulse mode,it rapidly decreases as plasma treatment time is increased.When the plasma treatment time exceeds 6 min,the pH value begins to decrease,and meanwhile in bipolar pulse mode,it reaches a stable value (about 3.8) which is lower than that in unipolar discharge.Besides,NO?3and NO?2in all three pulsed discharges modes show an increase trend as plasma treatment time is increased(shown in figures 13(b) and (c)).In comparison,NO?3and NO?2concentrations are close in both unipolar positive and negative pulse modes,which is consistent with the works of Hamdanet al[15].While the concentrations of the reactive species in bipolar mode is much higher than those in both unipolar pulse modes.The generation of NO?2and NO?3is mainly originated from the dissolution of NO and NO2(2 NO2+H2O →H++NO?2+NO?3;NO +NO2+H2O→2H++2NO?2)[24,38,39].Higher contents of gaseous NO and NO2in bipolar pulse discharge lead to higher production of NO?2and NO?3.Meanwhile,the formation processes of?NOxcause the production of H+,and higher production of?NOxin bipolar pulse mode also causes lower pH value (higher production of H+).

    Figure 12.Effects of pulse peak voltage on(a)Trot and(b)Tvib of NPG-LDs generated by bipolar pulse,positive pulse,and negative pulse.

    Figure 13.(a) pH of solution,(b)NO? 3 ,(c)NO? 2 ,and (d) H2O2 concentration varied as a function of plasma treatment time.

    H2O2is a major long-lived reactive species in plasma and plays an important role in plasma microbial inactivation[40].In general,several reactions of H2O2formation have been reported in interaction of plasma–liquid,however,the main pathway is the recombination of two OH radicals (OH+OH→H2O2) [41].According to figure 13(d),the concentrations of H2O2in all pulsed discharge modes increase with increasing treatment time.After 10 min treatment time,the energy yield in unipolar positive pulse driven discharge is 1.10 g kW?1h?1,which is larger than those in unipolar negative pulse driven discharge (0.88 g kW?1h?1),the similar results are also obtained by Heet al[42] and Chenet al[41].Heet al[42] reported that lower energy yield of H2O2in the discharge driven by the negative direction voltage is due to the existence of a cathode voltage fall on the liquid surface.Chenet al[41] reported that discharge with liquid anode can produce more aqueous OH than that of discharge with liquid cathode,which results in higher production of H2O2produced by discharge driven by the positive direction voltage.Besides,the energy yield of H2O2in bipolar mode is 1.78 g kW?1h?1,which is much larger than those in unipolar modes.The fastest production rate of H2O2in bipolar pulse mode can be basically caused by the following reasons: the production of OH is related to the charge density and discharge energy.The higher the charge density and discharge energy,the more OH are produced [43].When the unipolar pulse voltage is used to excite discharge,charges can accumulate at the quartz tube and water surface,which decreases the electrical field and electron density.However,the bipolar pulse voltage can eliminate such charge accumulation [21].Hence,higher charge density and discharge energy cause higher production of OH,which resulting in higher production of H2O2.

    4.Conclusions

    In this paper,a comparison of the atmosphere pressure N2NPG-LDs driven by unipolar (both negative and positive pulses)and bipolar pulses in a trumpet tube is experimentally studied.It can be concluded that diffuse NPG-LD can be obtained under the excitation of all three pulse modes in atmospheric N2.The discharge process is completely different between unipolar (both positive and negative) and bipolar pulsed discharges.In both negative and positive NPG-LDs,twice discharges occur in rising time and falling time of each voltage pulse.While only one relatively strong current peak appears in a single pulse of bipolar NPG-LD.However,the gas temperatures of plasmas in three discharge modes are near and kept relative low values(340–410 K)with increasing the pulse voltage from 26 to 34 kV.Besides,rising pulse peak voltage can contribute to increase the emission intensities of OH(A–X),N2(C–B),and O,while the emission intensities of OH(A–X) and O have the largest values at around 200 ml min?1.The FTIR absorbance intensities of NO2and N2O enhance with the increase of pulse peak voltage and decrease with the increase of gas flow rate.

    The polarity of unipolar pulse voltage has a little effect on the discharge current and reactive species production.Compared with unipolar pulse discharge,the bipolar pulse discharge shows lower breakdown voltage and larger production rate of reactive species.Under the same discharge power,the emission intensities of OH(A–X),N2(C–B),and O(3p–3s) in bipolar pulse discharge are higher than those in unipolar(both the positive and negative)pulse discharge.The absorbance intensities of NO2and N2O are higher in bipolar pulse mode than those in both unipolar pulse modes.Solution pH value in bipolar mode is much lower,and the concentrations of H2O2,NO?2,and NO?3in bipolar pulse mode are much higher than those in unipolar modes (both positive and negative pulses).

    Acknowledgments

    This work is supported by National Natural Science Foundation of China (Nos.51977023,51677019,and 11965018)and Fundamental Research Funds for the Central Universities in China (No.DUT18LK42).

    猜你喜歡
    建平
    Her dream came true
    Her dream came true她的夢想成真了
    Spectroscopic study of B2Σ+–X1 2Π1/2 transition of electron electric dipole moment candidate PbF
    建平博物館藏遼代雞冠壺
    仝建平 教授
    Preface
    周建平教授
    清·傅山論書句
    The Effect of Grammar Teaching on Writing in China
    卷宗(2016年3期)2016-05-10 07:41:06
    Ideology Manipulation Reflected in the Translation of Selected Works of Mao Zedong
    教師·下(2009年11期)2009-12-25 08:53:50
    日韩av免费高清视频| 丰满迷人的少妇在线观看| 波野结衣二区三区在线| 国产精品不卡视频一区二区| 97在线人人人人妻| 啦啦啦啦在线视频资源| 狂野欧美白嫩少妇大欣赏| 春色校园在线视频观看| 亚洲欧美清纯卡通| 在线观看国产h片| 国产伦精品一区二区三区视频9| av播播在线观看一区| av网站免费在线观看视频| 欧美日韩综合久久久久久| 欧美激情极品国产一区二区三区 | 亚洲第一av免费看| 国产视频内射| 国产老妇伦熟女老妇高清| 老司机亚洲免费影院| 嫩草影院入口| 亚洲综合精品二区| 91在线精品国自产拍蜜月| 91久久精品国产一区二区三区| 久久久久视频综合| 精品久久国产蜜桃| 黄色怎么调成土黄色| 亚洲欧洲精品一区二区精品久久久 | 桃花免费在线播放| av免费在线看不卡| 国产男人的电影天堂91| 国产成人精品婷婷| 日韩成人av中文字幕在线观看| 美女福利国产在线| 国产精品熟女久久久久浪| 久久精品国产亚洲网站| 欧美日韩亚洲高清精品| av国产久精品久网站免费入址| 大香蕉97超碰在线| 一区二区三区乱码不卡18| 成年人午夜在线观看视频| 女性被躁到高潮视频| 2021少妇久久久久久久久久久| 最近2019中文字幕mv第一页| 国产精品久久久久久精品古装| 又爽又黄a免费视频| 国产av一区二区精品久久| 久久av网站| 日本免费在线观看一区| 国产精品无大码| 久久久久久伊人网av| 青青草视频在线视频观看| 国内精品宾馆在线| 国产视频内射| 国产精品蜜桃在线观看| 国产精品伦人一区二区| 99热这里只有是精品50| 国产探花极品一区二区| 日韩av在线免费看完整版不卡| 99热网站在线观看| 狂野欧美激情性xxxx在线观看| 一二三四中文在线观看免费高清| 热re99久久国产66热| 国产精品熟女久久久久浪| 国产成人aa在线观看| 亚洲成人一二三区av| 成人二区视频| 黄色欧美视频在线观看| 一个人看视频在线观看www免费| 蜜桃在线观看..| 女性生殖器流出的白浆| 亚洲av欧美aⅴ国产| a级毛片在线看网站| 汤姆久久久久久久影院中文字幕| 亚洲熟女精品中文字幕| 精品国产一区二区久久| 日本猛色少妇xxxxx猛交久久| 国产一区亚洲一区在线观看| 久久ye,这里只有精品| 激情五月婷婷亚洲| 精品一区二区免费观看| av免费在线看不卡| 成人影院久久| 日韩熟女老妇一区二区性免费视频| 大香蕉久久网| 国产午夜精品一二区理论片| 欧美+日韩+精品| 亚洲电影在线观看av| 波野结衣二区三区在线| 国产免费一级a男人的天堂| 日韩三级伦理在线观看| 毛片一级片免费看久久久久| 亚洲成人一二三区av| 黄色欧美视频在线观看| 国产熟女欧美一区二区| 国产精品偷伦视频观看了| 免费av中文字幕在线| 男人爽女人下面视频在线观看| 成年av动漫网址| 人人妻人人爽人人添夜夜欢视频 | 成人国产av品久久久| 日韩成人av中文字幕在线观看| 大码成人一级视频| 美女脱内裤让男人舔精品视频| 又爽又黄a免费视频| 亚洲人成网站在线观看播放| 国产又色又爽无遮挡免| 美女脱内裤让男人舔精品视频| 日韩av不卡免费在线播放| 日韩av不卡免费在线播放| 高清黄色对白视频在线免费看 | 我要看日韩黄色一级片| 女性被躁到高潮视频| 欧美97在线视频| 国产免费一级a男人的天堂| 亚洲国产欧美在线一区| 99久国产av精品国产电影| 欧美精品高潮呻吟av久久| 色网站视频免费| 只有这里有精品99| 免费大片18禁| 免费看av在线观看网站| 国产精品人妻久久久久久| 亚洲欧美精品自产自拍| 国产黄频视频在线观看| 精品一区二区免费观看| 色视频在线一区二区三区| 亚洲成人手机| 99久久精品国产国产毛片| 人妻少妇偷人精品九色| 亚洲av不卡在线观看| 欧美97在线视频| 免费大片黄手机在线观看| 一级av片app| 春色校园在线视频观看| 久久精品国产a三级三级三级| 80岁老熟妇乱子伦牲交| 欧美激情国产日韩精品一区| 中国美白少妇内射xxxbb| 亚洲欧美一区二区三区黑人 | 又粗又硬又长又爽又黄的视频| av不卡在线播放| 国产精品麻豆人妻色哟哟久久| 夜夜看夜夜爽夜夜摸| 日本vs欧美在线观看视频 | 波野结衣二区三区在线| 男人舔奶头视频| 黑人猛操日本美女一级片| 欧美日韩av久久| 日韩一区二区视频免费看| 高清黄色对白视频在线免费看 | 丰满饥渴人妻一区二区三| 乱人伦中国视频| 99热这里只有是精品50| 熟女av电影| 国产熟女欧美一区二区| 国产欧美日韩综合在线一区二区 | 天天操日日干夜夜撸| 日韩欧美一区视频在线观看 | 极品人妻少妇av视频| 自拍欧美九色日韩亚洲蝌蚪91 | 中文字幕免费在线视频6| 午夜免费男女啪啪视频观看| 国产精品国产三级专区第一集| 欧美国产精品一级二级三级 | 欧美日韩视频精品一区| 国产成人免费无遮挡视频| 老熟女久久久| 国产高清不卡午夜福利| 99久久中文字幕三级久久日本| 日日爽夜夜爽网站| 亚洲精品乱码久久久v下载方式| 精品少妇黑人巨大在线播放| 欧美bdsm另类| 高清不卡的av网站| 国产深夜福利视频在线观看| 精品少妇黑人巨大在线播放| 亚洲精品自拍成人| 欧美日韩在线观看h| 一区二区av电影网| 久久ye,这里只有精品| 久久午夜综合久久蜜桃| 视频中文字幕在线观看| 久久99热这里只频精品6学生| 亚洲色图综合在线观看| 国产片特级美女逼逼视频| 国产在线一区二区三区精| 又爽又黄a免费视频| 色5月婷婷丁香| 男的添女的下面高潮视频| 日韩中文字幕视频在线看片| 国产精品免费大片| 高清欧美精品videossex| 高清在线视频一区二区三区| 中文字幕人妻丝袜制服| 精品国产乱码久久久久久小说| 九色成人免费人妻av| 日韩免费高清中文字幕av| 精品久久久噜噜| 精品国产露脸久久av麻豆| 七月丁香在线播放| 人妻人人澡人人爽人人| a级毛色黄片| 最近的中文字幕免费完整| 一级毛片 在线播放| av天堂久久9| 丰满少妇做爰视频| 久久精品国产鲁丝片午夜精品| 91精品一卡2卡3卡4卡| 久久久久久久久久久久大奶| 欧美另类一区| 人妻系列 视频| 伦精品一区二区三区| 亚洲精品aⅴ在线观看| 亚洲美女视频黄频| 一区二区三区四区激情视频| 国产精品久久久久久久久免| 岛国毛片在线播放| 看非洲黑人一级黄片| 一边亲一边摸免费视频| 成人漫画全彩无遮挡| 看免费成人av毛片| 国产在线免费精品| 2022亚洲国产成人精品| 十分钟在线观看高清视频www | 9色porny在线观看| 免费看av在线观看网站| 国产精品.久久久| 成人国产av品久久久| videos熟女内射| 国产一区二区三区综合在线观看 | 伊人亚洲综合成人网| 日日撸夜夜添| 国精品久久久久久国模美| 狂野欧美激情性bbbbbb| 在线观看免费视频网站a站| 寂寞人妻少妇视频99o| 一本色道久久久久久精品综合| 精品国产国语对白av| 伊人久久国产一区二区| 亚洲,欧美,日韩| 免费观看无遮挡的男女| 精品国产国语对白av| 国产色婷婷99| 亚洲精品乱码久久久久久按摩| 久久久久视频综合| 国产黄片视频在线免费观看| 久久久久精品性色| 国产成人精品一,二区| 欧美精品人与动牲交sv欧美| 亚洲精品国产色婷婷电影| 韩国av在线不卡| 两个人免费观看高清视频 | 精品国产国语对白av| 亚洲第一av免费看| 国产精品国产三级专区第一集| 久久午夜综合久久蜜桃| 精品人妻熟女av久视频| 一级毛片aaaaaa免费看小| 男女边摸边吃奶| 日本av手机在线免费观看| 乱人伦中国视频| 久久99一区二区三区| 狂野欧美激情性xxxx在线观看| 久久精品国产亚洲网站| 久久国产精品男人的天堂亚洲 | 精品一品国产午夜福利视频| 夫妻性生交免费视频一级片| 高清av免费在线| 人妻少妇偷人精品九色| 在线观看人妻少妇| 亚洲av欧美aⅴ国产| 黄色怎么调成土黄色| 中文在线观看免费www的网站| 亚洲精品自拍成人| 男男h啪啪无遮挡| 成人综合一区亚洲| 国产 一区精品| 夜夜骑夜夜射夜夜干| 亚洲人成网站在线播| 欧美人与善性xxx| 少妇被粗大猛烈的视频| 一区二区三区免费毛片| 国产淫片久久久久久久久| 精品久久国产蜜桃| 免费观看性生交大片5| 成年av动漫网址| 麻豆成人av视频| 最新的欧美精品一区二区| av天堂久久9| 韩国高清视频一区二区三区| 日本黄色日本黄色录像| 国产极品天堂在线| 日本91视频免费播放| 少妇的逼水好多| 国产视频首页在线观看| 国产黄色视频一区二区在线观看| 中文字幕制服av| 国产男女内射视频| 偷拍熟女少妇极品色| 久久99热6这里只有精品| 久久婷婷青草| 亚洲av日韩在线播放| 大片电影免费在线观看免费| 青春草国产在线视频| h视频一区二区三区| 亚洲性久久影院| 成年av动漫网址| 夜夜看夜夜爽夜夜摸| 国产成人精品婷婷| 三上悠亚av全集在线观看 | 亚洲av电影在线观看一区二区三区| 在线亚洲精品国产二区图片欧美 | 最新中文字幕久久久久| 大香蕉97超碰在线| 免费看光身美女| 精品久久久久久久久av| 成年av动漫网址| 日韩一本色道免费dvd| 久久6这里有精品| 观看免费一级毛片| 久久国产乱子免费精品| 99久国产av精品国产电影| 久久久久久久久久成人| 国产一区二区在线观看av| 国产亚洲一区二区精品| av.在线天堂| 久久青草综合色| 亚洲丝袜综合中文字幕| 亚洲国产av新网站| 午夜激情福利司机影院| 成人亚洲精品一区在线观看| 日韩av免费高清视频| 久久精品夜色国产| 中国美白少妇内射xxxbb| 视频区图区小说| 亚洲国产色片| 高清视频免费观看一区二区| 亚洲美女视频黄频| 狂野欧美白嫩少妇大欣赏| 欧美最新免费一区二区三区| 天堂8中文在线网| 日韩一区二区视频免费看| 极品人妻少妇av视频| 亚洲av综合色区一区| 男女免费视频国产| 久久午夜福利片| 欧美人与善性xxx| 黑人猛操日本美女一级片| 精品亚洲成a人片在线观看| 免费高清在线观看视频在线观看| 大香蕉97超碰在线| 国产成人精品福利久久| 亚洲自偷自拍三级| 欧美丝袜亚洲另类| 国产高清不卡午夜福利| 777米奇影视久久| 我要看黄色一级片免费的| 尾随美女入室| 国产一区二区在线观看av| 国产精品久久久久久精品电影小说| 国产成人精品福利久久| 欧美少妇被猛烈插入视频| 国产精品国产三级国产专区5o| 国产又色又爽无遮挡免| 亚洲国产av新网站| 日韩强制内射视频| 国产深夜福利视频在线观看| 天堂中文最新版在线下载| 国产日韩一区二区三区精品不卡 | 亚洲伊人久久精品综合| 欧美少妇被猛烈插入视频| 一本大道久久a久久精品| 亚洲精品国产av蜜桃| 国产成人精品福利久久| av福利片在线| 夫妻午夜视频| 亚洲精品中文字幕在线视频 | 久久精品国产自在天天线| 国产成人aa在线观看| 少妇高潮的动态图| 一区在线观看完整版| 一本一本综合久久| 色5月婷婷丁香| 最近最新中文字幕免费大全7| 久久国内精品自在自线图片| 欧美老熟妇乱子伦牲交| 亚洲av福利一区| 内地一区二区视频在线| 人妻夜夜爽99麻豆av| 少妇猛男粗大的猛烈进出视频| 国产乱人偷精品视频| 欧美亚洲 丝袜 人妻 在线| 精品久久久精品久久久| 精品亚洲成国产av| 日本91视频免费播放| 国内少妇人妻偷人精品xxx网站| 久久午夜福利片| 伊人久久精品亚洲午夜| 久久久久人妻精品一区果冻| 午夜免费男女啪啪视频观看| 亚洲内射少妇av| 亚洲国产毛片av蜜桃av| 亚洲美女视频黄频| 亚洲国产成人一精品久久久| 精品熟女少妇av免费看| 插阴视频在线观看视频| 国产在线免费精品| 黄色怎么调成土黄色| a级片在线免费高清观看视频| 午夜久久久在线观看| 日本欧美视频一区| 97超视频在线观看视频| 晚上一个人看的免费电影| 久久99精品国语久久久| 午夜激情福利司机影院| 精品国产一区二区三区久久久樱花| 在线观看免费高清a一片| 亚洲丝袜综合中文字幕| 少妇的逼好多水| 精品久久久噜噜| 色婷婷av一区二区三区视频| 久久精品夜色国产| 久久国产精品大桥未久av | 精品一区二区三卡| 少妇人妻久久综合中文| 91精品国产九色| 日本午夜av视频| 嘟嘟电影网在线观看| 街头女战士在线观看网站| 老司机影院成人| 国产精品久久久久久久电影| 精品国产国语对白av| 伦理电影大哥的女人| av国产精品久久久久影院| 国产成人一区二区在线| 欧美国产精品一级二级三级 | 一级片'在线观看视频| 精品99又大又爽又粗少妇毛片| 深夜a级毛片| 大香蕉97超碰在线| 欧美人与善性xxx| 亚洲情色 制服丝袜| 国产精品麻豆人妻色哟哟久久| 一本—道久久a久久精品蜜桃钙片| 一级av片app| 欧美日韩在线观看h| 麻豆乱淫一区二区| 亚洲av中文av极速乱| 熟女人妻精品中文字幕| 国产熟女欧美一区二区| 久久久久视频综合| 免费黄频网站在线观看国产| 搡女人真爽免费视频火全软件| 成人二区视频| 午夜av观看不卡| 久久精品久久久久久久性| 蜜桃在线观看..| 久久人人爽人人片av| 我的老师免费观看完整版| 久久午夜综合久久蜜桃| 国产精品人妻久久久久久| 国产男女内射视频| 亚洲第一av免费看| 26uuu在线亚洲综合色| 男人爽女人下面视频在线观看| 天堂中文最新版在线下载| 美女cb高潮喷水在线观看| 夜夜看夜夜爽夜夜摸| 亚洲国产最新在线播放| 国产av精品麻豆| 国产免费一区二区三区四区乱码| 久久久国产精品麻豆| 免费观看无遮挡的男女| 不卡视频在线观看欧美| 亚洲情色 制服丝袜| 久久久欧美国产精品| 日韩强制内射视频| 国产精品不卡视频一区二区| 色哟哟·www| 久热这里只有精品99| 日韩三级伦理在线观看| 亚洲av在线观看美女高潮| 成人国产麻豆网| 国产乱人偷精品视频| 色吧在线观看| 久久久久久久久久久丰满| 国产成人91sexporn| 午夜精品国产一区二区电影| 日韩av在线免费看完整版不卡| 国产免费一区二区三区四区乱码| 99国产精品免费福利视频| 国产精品三级大全| 伊人久久国产一区二区| 美女主播在线视频| a 毛片基地| 免费观看在线日韩| 久久久久久久精品精品| 久久久欧美国产精品| 欧美精品国产亚洲| 乱码一卡2卡4卡精品| 一区二区av电影网| 乱人伦中国视频| 色婷婷av一区二区三区视频| 国产亚洲av片在线观看秒播厂| 亚洲国产av新网站| 亚洲图色成人| 亚洲av成人精品一二三区| 国产91av在线免费观看| 99久久精品热视频| 99久久人妻综合| 日韩不卡一区二区三区视频在线| 丝瓜视频免费看黄片| 日日啪夜夜撸| 麻豆乱淫一区二区| 日本av免费视频播放| 天堂俺去俺来也www色官网| 亚洲美女黄色视频免费看| 久久精品国产a三级三级三级| 男女边吃奶边做爰视频| 成人免费观看视频高清| 国产黄色视频一区二区在线观看| 免费播放大片免费观看视频在线观看| 精品一品国产午夜福利视频| 久久 成人 亚洲| 成人毛片a级毛片在线播放| 国产精品伦人一区二区| 亚洲精品色激情综合| 伦精品一区二区三区| 美女cb高潮喷水在线观看| av播播在线观看一区| 老女人水多毛片| 9色porny在线观看| 日本-黄色视频高清免费观看| 热re99久久精品国产66热6| 99久久中文字幕三级久久日本| 中文资源天堂在线| 亚洲精品国产av成人精品| 国产精品福利在线免费观看| 国产色爽女视频免费观看| 青青草视频在线视频观看| 欧美日韩一区二区视频在线观看视频在线| 久久精品久久久久久久性| 亚州av有码| 亚洲,欧美,日韩| 99久国产av精品国产电影| 亚洲天堂av无毛| 日韩视频在线欧美| 免费观看无遮挡的男女| 久久免费观看电影| 国产乱人偷精品视频| 成人18禁高潮啪啪吃奶动态图 | .国产精品久久| 亚洲欧美日韩另类电影网站| 桃花免费在线播放| 欧美人与善性xxx| 一本一本综合久久| 欧美bdsm另类| av线在线观看网站| 亚洲精品色激情综合| 欧美变态另类bdsm刘玥| 久久午夜福利片| 只有这里有精品99| 成人美女网站在线观看视频| 久久6这里有精品| 久久免费观看电影| av在线app专区| 成人18禁高潮啪啪吃奶动态图 | 蜜臀久久99精品久久宅男| 国产亚洲av片在线观看秒播厂| 在线观看美女被高潮喷水网站| 日本黄大片高清| 狠狠精品人妻久久久久久综合| 97在线视频观看| 99精国产麻豆久久婷婷| 国产无遮挡羞羞视频在线观看| 在线观看三级黄色| 国产精品一区二区三区四区免费观看| 曰老女人黄片| 成人国产麻豆网| 亚洲精华国产精华液的使用体验| 春色校园在线视频观看| 最黄视频免费看| 久久久精品免费免费高清| 欧美日韩国产mv在线观看视频| 91aial.com中文字幕在线观看| 日韩电影二区| 热re99久久国产66热| av在线观看视频网站免费| 久久国产精品男人的天堂亚洲 | 国产亚洲最大av| 欧美日韩一区二区视频在线观看视频在线| 美女视频免费永久观看网站| 国产精品三级大全| 精品国产露脸久久av麻豆| 亚洲成人一二三区av| 日本猛色少妇xxxxx猛交久久| www.av在线官网国产| 免费黄色在线免费观看| 一级毛片 在线播放| 久久鲁丝午夜福利片| 少妇人妻精品综合一区二区| 亚洲精品乱久久久久久| 国产精品一区二区三区四区免费观看| 秋霞在线观看毛片| 国产男人的电影天堂91| 女性生殖器流出的白浆| 久久精品国产亚洲网站| 啦啦啦在线观看免费高清www| 大香蕉久久网| 久久99热6这里只有精品| 国产亚洲欧美精品永久| 亚洲av二区三区四区| 超碰97精品在线观看| 最近最新中文字幕免费大全7| 国产欧美亚洲国产|