离子电流
The relationship between ion current and temperature at the electrode gap
Zhongquan Gao,Xiaomin Wu *,Chao Man,Xiangwen Meng,Zuohua Huang
Institute of Internal Combustion Engine,School of Energy and Power Engineering,Xi ’an Jiaotong University,Xi ’an 710049,China
a r t i c l e i n f o
Article history:
Received 12June 2009Accepted 10July 2011
Available online 20July 2011Keywords:Ion current
Electrodes position Combustion
Local temperature
a b s t r a c t
The relationship between ion current and local temperature was investigated with compressed natural gas (CNG)as a fuel.The ion current was measured using a pair of ignition electrodes and a pair of detector electrodes inside of a constant volume combustion bomb.The average temperature of the whole gas and the temperature at electrode gap were calculated using AVL-FIRE software.Meanwhile,?ame development and pressure were recorded by a high-speed camera and a pressure sensor,respectively.The study indicates that,when ignition electrodes were used for detection,the current showed ignition,front-?ame and post-?ame stages.However,the ignition and part of the front-?ame current were lost,when detector electrodes were used.The critical temperature for NO tgeneration and the appearance of post-?ame current was about 2000K.There were a linear relationship between the temperature and the number of NO t.With the increase in the distance between the two pair electrodes,the ion current and temperature decreased and the appearances of the front-?ame and post-?ame currents were postponed.The lower the temperature at the electrode gap was,the more obvious the in ?uence of the contact area between the ?ame and the internal bomb wall on the post-?ame current was.
ó2011Elsevier Ltd.All rights reserved.
1.Introduction
To meet the requirements for the emission reduction and fuel economy of spark-ignition (SI)engines,electronic engine diagnosis has been conducted in various ways in the last two https://www.wendangku.net/doc/b86163126.html,bustion parameters play an important role in the control of the timing and quantity of fuel supply.To get the parameters correlated to the combustion process inside the cylinder volume,several different sensor technologies have been implemented.For example,pressure sensor and laser technique have been success-fully applied in the engine on-line survey ?eld [1,2].Although pressure sensor can record the pressure in the combustion process and withstand the violent environment inside a combustion engine,it has to be installed in the engine as an additional device and consequently,the cost goes up.As to the advanced laser technique,despite its successful application in laboratory,it has been proved to be unsatisfactory in practical usage [2].In search of an economic and convenient sensor,ion current measurement,a new electronic control technique using spark plug as detection sensor,has been developed.It has been widely used in mis ?re detecting,knock detecting,cam phase determination,air-fuel ratio estimation,pressure estimation and peak maximum pressure position estimation [3e 14].In addition,its successful applications
have been reported in ignition control and close-loop combustion control in SI engine [10e 17].
As the principle of the ion current measurement goes,a constant DC voltage applied over the spark plug gap leads to the generation of ion current during the combustion process.Generally,the ion current has three distinct phases,ignition,front-?ame and post-?ame.The current is a local parameter affected by ion density,gas ?ow and temperature around the electrodes [18,19].Therefore,where the ion current is detected is essential for analysis.A detailed knowledge of the relationship between the spark position and the ion current has been reported in previous investigations.A.Franke et al.[2]equipped the cylinder cap with a spark plug in two positions (central and periphery)respectively and observed that the front-?ame current in the central location was more pronounced than the one in the peripheral position,but the post-?ame current showed the opposite trend.The study of H.Kubach [20]showed that the position of the probe had an essential in ?uence on the measurement results of ion current,and that the probe should be located near the nozzle jets to best detect the ions of the combustion.L.Peron et al.[21]found that the best location for detecting a complete ion current,including the “post-?ame ”peak and the “front-?ame ”,was near the zone where the combustion process was initiated.
Current in post-?ame is closely related to the temperature near the spark plug.Therefore,a detailed knowledge of the temperature distribution around the electrodes in the combustion chamber is of great importance in ion current technology.Great efforts have been
*Corresponding author.Tel.:t862982663587;fax:t862982668789.E-mail address:xmwu@https://www.wendangku.net/doc/b86163126.html, (X.
Wu).Contents lists available at ScienceDirect
Applied Thermal Engineering
journal ho mepage:www.elsevier.co m/lo
cate/apthermeng
1359-4311/$e see front matter ó2011Elsevier Ltd.All rights reserved.doi:10.1016/j.applthermaleng.2011.07.014
Applied Thermal Engineering 33-34(2012)15e 23
made to depict the temperature distribution more precisely.A.Franke et al.[22]studied the temperature e current relationship using a one-zone model to calculate the temperature.The result showed that the current was dependent on the temperature of the burnt gas.I.Anderson [23]utilized three different models to calculate the temperature:a single-zone,a mixed two-zone,and a kernel zone model.His study showed the average temperature of the whole combustion chamber and the burnt gas.In addition,some researchers investigated the temperature using other methods.A.Saitzkoff [24],M.Tiele [25],and M.Bach [26]depicted the average temperature in a small volume element and the temperature distribution using two-dimensional numerical method and optical ?ber sensor.
It is inconvenient to study the effect of electrode location on ion current if electrodes are arranged at regular intervals in engine chamber.In addition,previous works calculates the average temperature of the burnt gas or the whole chamber to study the ion current e temperature relationship,but the current in post-?ame is directly related to the local temperature around the electrodes gap.In this paper,the experiment was conducted in a constant combustion bomb.A pair of ignition electrodes for ignition and detection and a pair of detector electrodes in parallel to the ignition electrodes for detection were used,and the parallel distance between the two pairs of electrodes could be adjusted freely.The temperature around detector electrodes,the average temperature and the temperature distribution in the whole bomb were
calculated using AVL-FIRE software.The study was expected to clarify the relationship between the ion current and the local temperature around detector electrodes.2.Experiments and procedures
Fig.1(a)shows the schematic diagram of the constant volume combustion bomb and the measuring circuit of ion current.The combustion bomb was a cubic chamber with a volume of 108?108?135cubic millimeter.Two sides of the bomb were transparent,which made the inside of the chamber optically acces-sible.The charge ?owed into the combustion bomb via the inlet/outlet valve.No gas motion was generated in the combustion chamber.A pair of straight threaded stainless steel electrodes with a diameter of 2mm,a gap (d )of 2mm and a sharp tip were used for ignition and measurement.Another pair of detector electrodes of the same material and diameter were located in parallel to the ignition electrodes for ion current measurement.The parallel distance (h )could be adjusted freely.The distances were 0,10,15,20,25mm in this study.An electrical ?eld was set up by 380V DC power supply after the ignition discharge.The resistance R 1and R 2were 10M U and 150k U .The measurement circuit was connected to the two pairs of electrodes,respectively.The cathode electrodes (at b1,c1)and the wall of the bomb were connected to the ground (Fig.1(a)).When point a and a1connected with point b and b1respectively,the igni-tion electrodes were used for both ignition and
detection.
Fig.1.Schematic diagram of experimental system.(a)Constant volume combustion bomb and measuring circuit.(b)Schlieren system.
Z.Gao et al./Applied Thermal Engineering 33-34(2012)15e 23
16
Nevertheless,when point a and a 1connected with point c and c 1respectively,the ignition electrodes were used for ignition only and the detector electrodes were used for detecting the ion current.
Fig.1(b)shows the optical system used to record the ?ame growth.A 12-bit,544?544pixel REDLAKE HG-100K high speed camera was used in the schlieren optical system to record the ?ame development at a speed of 5000pictures per second.The quartz glass windows were square-shaped with a side length of 80mm,and thus the spatial resolution of the ?ame image was 0.147?0.147mm.
Fig.2shows the system used to measure the ion current.In this system,the gas sources were compressed natural gas,oxygen (O 2)and nitrogen (N 2).The quantity of each gas in the mixing chamber was adjusted according to the partial pressure of each component.Those gases were well mixed into a homogeneous mixture at stoichiometric air-fuel ratio in the mixing chamber.A vacuum pump was used to draw out the gases from the chamber.The initial pressure in the combustion bomb was measured by a mercury manometer with a pressure accuracy of 1mmHg.The pressure during the combustion was recorded by a piezoelectric absolute pressure transducer and model Kistler 4075A,with a resolution of 0.01kPa.The initial temperature inside the combustion chamber was measured using a thermocouple with an accuracy of 1K.The initial pressure and temperature in the chamber were set at 100kPa and 293K.The initial conditions were strictly controlled in the experiments to ensure the same initial pressure and temperature.The in ?uence of wall temperature on mixture temperature could be avoided by allowing a long-enough time interval between experi-ments for the wall to recover to the initial temperature.3.Calculation model 3.1.Temperature
The temperature ?eld in the chamber is simulated on the AVL-FIRE.The chamber of the combustion bomb is chosen as the
control volume.Due to the center symmetry of the combustion chamber,a quarter of the combustion bomb (the dashed area of lower right part of the bomb in Fig.3(a))is selected as the calcu-lation region to ef ?ciently demonstrate the calculation process.Additionally,only a pair of ignition electrodes are used to simplify the calculation process.
The differential control equations of mass,momentum,energy and species conservations are shown as follows [27]:
v r v t t
v r u i
v x i ?0(1)
r
v u j v t tu j v u i
v x i
?r g i à
v P v x j t
v v x j
s ij àr u i u j (2)
r v H tU j
v H j !?r _q g tv P j tv i àU j s i átv j l v T
j !
(3)
r v C v t tU j
v C v x j !?r _r tv v x j D v C
v x j
àr cu j !(4)
where t ,u and x are the time,velocity and coordinate of the Cartesian coordinate;subscript i ,j and k are the coordinate direc-tion;r ,T ,P ,l ,g i ,_q
g ;_r ,U ,H and C are density,temperature,pressure,thermal conductive coef ?cient,acceleration of gravity,heat ?ux,variation caused by combustion,internal energy,enthalpy and component concentration,respectively.In momentum equation,r u i u j ?s t
ij is the turbulent stress tensor (turbulent ?ux-transport
of momentum per unit volume,r u i ,by velocity ?uctuation u i ),
and r cu j ?m 00t i is the turbulent mass ?ux vector.The k-3Model and
the Probability Density Function Approach (PDF)are applied for the turbulence and the combustion,respectively.The simulation is based on the Finite Volume method.The isothermal combustion wall (293K)and the ignition electrodes with adiabatic boundary are assumed.
The mesh is established by block structure mesh method.According to the rise rate of pressure and the timing of the maximum pressure value every time,the chamber are divided into optimalizing size meshes with maximum side length 0.1mm and minimum side length 0.03mm.The length of mesh side is opti-mized according the curvature variation of the meshes by FAME advanced hybrid tools.After the meshes are generated,the meshes are checked for avoiding negative volume cell,negative normal cell and twisted face.The meshes including negative volume cell and negative normal cell will be optimized with auto smooth tools,and the meshes including twisted face are optimized volume
optimizer
Fig.2.Measuring
system.
Fig.3.Calculation region composed of the control volumes.(a)The region for calculation in constant volume combustion bomb.(b)The grids of calculation region.
Z.Gao et al./Applied Thermal Engineering 33-34(2012)15e 2317
tools.Finally,164,029meshes(known as control volumes)with 172,670nodes were generated as shown in Fig.3(b).The meshes representing the center of the detector electrodes in different distances(h?0,10,15,20,25mm)are marked in Fig.3(b).The initial condition of the temperature,pressure and the air/fuel ratio are same as that of the experiment.The calculated pressures are compared with that measured.
3.2.Mass fraction burned
The mass fraction burned(u b)is determined using Rasswei-ler e Withrow method[28],the mass fraction burned can be induced and expressed as:
u b?pàp1
2
àp1(5) where p1and p2is the initial pressure and the maximum pressure respectively.
4.Results and discussions
4.1.Temperature distribution in the bomb
Fig.4presents the temperature?eld corresponding to calcula-tion region(surface A)shown in Fig.3(b).Evident boundary between the higher and lower temperature?eld,which was regarded as?ame front,was observed in Fig.4.The temperature of the?ame front was about1800K,and there was obvious temper-ature gradient(1800K e400K)from the boundary to the unburnt gas as Fig.4shown.These calculation results are in agreement with Law CK’s study on premixed?ame.In his study,the temperature of the?ame front was about1800K,and there was larger temperature gradient around the?ame front due to active chemical reaction of the combustion[29].
Fig.5shows the?ame photographs recorded by schlieren optical system during the combustion process.It was observed that the burnt zone and unburnt zone were divided by the?ame.The rectangle zone marked by dash line is corresponded to the temperature?eld for calculation shown in Fig.4.The radius of the ?ame could be measured from the photographs and the calculated temperature?eld,respectively.Fig.4and Fig.5,taken together, show that the development of?ame measured from the photo-graphs was consistent with that from the calculation.
During the combustion process,the parameters of meshes from the center to the wall change with time.The mixture at different part of the bomb underwent different compression process.The mixture at the ignition center burned earliest and expanded with lower pressure?rstly,and then,returned to the initial volume due to high pressure in the bomb.The mixture around the ignition center acquired more compression energy than the mixture far from the center[30].Therefore,the temperature was highest at ignition electrode gap,and the temperature of the burnt gas showed a radical decrease from the ignition center to the isothermal wall during the whole combustion process.The temperature of the wall remained constant at293K.
Figs.6and7show the pressure and?ame radius calculated by AVL-FIRE and obtained in the experiment,respectively.The ignition started at zero;the pressure increased with the combustion proceeding and dropped after60ms due to the temperature drop caused by the heat transfer to the wall.The calculated results,such as peak pressure value,the increasing slop of the pressure,the radius of the?ame,were in agreement with the experimental results.The maximum pressure difference and the maximum?ame radius difference between the calculated results and experimental results were5percent,which is in the range of the allowable error.
4.2.Ion current measured by ignition electrodes
In this part,the ignition electrodes were used for both ignition and detection.The ion current,pressure,average temperature of the whole mixture,the temperature at electrode gap(the mesh at the center of the electrode)and mass fraction burned(u b)
are
Fig.4.(a e f)Temperature distribution at different time.
Z.Gao et al./Applied Thermal Engineering33-34(2012)15e23
18
illustrated in Fig.8.The average temperature was much lower than the temperature at the electrode gap and the local temperature at the electrode gap related to the current was chosen for analysis.As shown in Fig.8,the ion current shows three characteristic phases:ignition,front-?ame,and post-?ame.After the ignition at zero,the ?rst peak of the ion current persisted for a duration of less than 5ms,then dropped to near zero over a period of time (point 1)and remained at a low level.This phase was called ignition stage in this paper.
The front-?ame stage lasted from point 2to point 4.About 2ms after point 1,the current increased remarkably to the second peak value (point 2)with a small rise of u b .The temperature at electrode gap increased rapidly during this short period of time.As the ?ame propagated,the current dropped to a lower level (point3)until to
point 4.It is well-known that radical ions such as CH 3t,CHO t
,C 3H 3tand H 3O t,are produced by the chemical reactions in the propa-gating ?ame zone during the combustion when CH 4is used as the fuel [31e 33].Thus,the chemic-ionization was the predominant ionization from point 2to point 4.The peak of front-?ame (point 2)was related to the ?ame kernel that was present in the vicinity of the electrode at the beginning of ?ame development [6,21,24,34].
The phase after point 4was called post-?ame stage.From point 4to point 6,the pressure,temperature and mass fraction burned grew rapidly.The current also increased ceaselessly.When u b was close to 95%(point 6),the temperature and pressure were close to the maximum value and a third peak value of current occurred.Subsequently,the current decreased to zero.The temperature was about 2000K when post-?ame current reached point 4.With the increase of the temperature after point 4,thermal ionization pre-dominated the ionization process in the bomb [6,24,35].The major contributor to the thermal ionization was NO tbecause NO mole-cules with lower ionization energy (9.26405eV)were easily ionized into NO tat high temperature [3,6,24,33,36].
A noteworthy phenomenon was that,60ms after the ignition,the current on post-?ame stage declined more sharply than the temperature.It is known that the NO generation depends on the
temperature and the oxygen-rich circumstance in the combustion chamber [37].After the temperature reached the maximum value,it decreased due to the convective heat transfer from the gas to the wall.Meanwhile,the CH 4/air mixture was almost completely consumed because u b was close to 100%,and the generation rate of NO decreased dramatically due to the scarcity of oxygen.The ionization ratio of NO was 2.44e-8[38],and the generation rate of NO tdecreased quickly with the decreased generation rate of NO.
4.3.Ion current measured by detector electrodes
In this part,the ignition electrodes and the detector electrodes were used for ignition and detection,respectively.The detector electrodes were in a parallel distance (h ?10mm)from the ignition electrodes.Fig.9plots the ion current,pressure,temperature at the detector electrode gap,and mass fraction burned (u b )versus the time.As shown in Figs.9and 6points corresponding to the time shown in Fig.8are marked by https://www.wendangku.net/doc/b86163126.html,pared with the current detected by ignition electrodes in Fig.8,the current obtained using detector electrodes in Fig.9did not show the three stages.This ?nding indicates that the ignition stage and part of the front-?ame stage (0ms to point 3)were missing and that part of the ion current was lost when the detector electrodes were separated from the ignition electrodes.In Fig.9,the current was divided into two parts by point 4,the front-?ame stage and the post-?ame stage.At point 3,the current showed a slight offset,u b merely increased by 6.78%,and the pressure showed a slight rise.Current remained at a low level until u b was close to 32%at point 4.At point 4,the temper-ature was about 2000K and the post-?ame stage began.
The current on post-?ame stage showed two peak values,the local maximum value and the global maximum value.Fig.9illu-minates the occurrence of the local maximum value on the post-?ame stage.Since both the cathode and the wall were connected to the ground and the resistor R 2(Fig.1(a)),when the ?ame front reached the wall,the wall absorbed the ions and electrons in
the
Fig.5.Schlieren photographs of the ?ame during the ?ame
development.
Fig.6.The measured and simulated
pressure.Fig.7.The measured and simulated ?ame radius.
Z.Gao et al./Applied Thermal Engineering 33-34(2012)15e 2319
?ame front.The number of the charged particles collected by the wall was decided by the contact area between the ?ame and the wall.The detailed process of ?ame (the internal zone in Fig.10(a))contacting the wall was investigated.The centrally ignited spher-ical shell-shaped ?ame front contacted the six internal walls,forming ring/arc(s)on the internal walls.The contact areas with the six internal walls were nearly the same.Internal top wall A in Fig.10(a)was analyzed and shown in Fig.10(b).Ring 1,ring 2,and arc 3illustrate three speci ?c statuses of the contact areas between ?ame front and wall A.Ring 1suggests that during the time between the ?ame front contacting the wall (r ?0,R ?L )and the ?ame front arriving at the bomb arris (ring 2,r ?L ,R ????2p L ),the contact area was always in the form of a ring.After that,the contact zone remained in the form of four arcs until the ?ame arrived at the vertexes of the bomb (r ????2p L ,R ????3p L )as is depicted by arc 3.Fig.10(c)shows the geometric relationship between the ?ame front radius and the internal wall A.L (54mm)is half the length of bomb arris,r is the radius of the circular zone,and R is the radius of the ?ame obtained from Fig.7.d 1is the width of the ring/arc(s)rep-resenting the thickness of the ?ame front,q is the arc chord angle,and u is an incoming parameter used to simplify the relationship between the arc and the ?ame radius (q t2u ?p /2).
Since the ?ame thickness d 1,much smaller than r ,was assumed to be constant in fully-developed ?ame [29,39,40],the area of the ring/arc (s )could be computed using the following equations:
S ?2p r $d L R ?????2L p
(6)
S ?4r q $d ???2p L (7) According to the plane geometry theory,the parameter r could be expressed as: r ???????????????????eR T2àL 2 q (8) Hence, S ?2p ??????????????????????h eR T2àL 2i r $d L R ???2p L (9) S ?4?????????????????? eR T2àL 2q $2 64p 2 à2acr cos 0B @L ??????????????????eR T2àL 2 q 1C A 375 $d ???2p L e10 T Fig.8.Ion current,pressure,temperature,and mass fraction burned. Z.Gao et al./Applied Thermal Engineering 33-34(2012)15e 23 20 Formula (9)is an increasing function while Formula (10)is a decreasing function.They are both determined by a unique variable,the radius of the ?ame (R ).In Fig.9,from point 2to point 5(the local maximum value,45ms),R increased from 66mm to about 76.5mm (close to ???2p L )and thus Formula (9)was used.The calculation showed that the number of chemi-ions increased with the ?ame development.From the local maximum value to the global maximum value (point 6),the radius of the ?ame was greater than ???2p L but smaller than ???3p L .Thus,Formula (10)was applied.The calculation result indicated that the number of the chemi-ions decreased with the decrease in the arc area.The in ?uence of chemi-ions on the post-?ame current grew signi ?cantly at ?rst but reduced later.The local maximum value was produced due to the largest area of the ring (45ms).Figs.8and 9reveals that although the two measurements showed similar contact area between the ?ame front and the wall due to the ?xed initial parameters of the mixture,the post-?ame current obtained by the ignition electrodes did not show the local maximum value at point 5.This may be because the temperature at the ignition electrode gap was higher than that at the detector electrode gap.When the ignition electrodes were used,the temperature at electrode gap was about 2625K at point 5.The in ?uence of the temperature on the current was more signi ?cant than that of the contact area.Thermal-ionization dominated the current on post-?ame stage,which led to the one-peak phenom-enon on the post-?ame stage,as is shown in Fig.8.When the detector electrodes separated from the ignition electrodes were used for detection,the temperature at the detector electrode gap Fig.9.Ion current,pressure,temperature,and mass fraction burned. Fig.10.The relationship between the ?ame and the bomb wall.(a)Three -dimensional sketch of the ?ame contacting the wall.(b)Contact area in internal wall A.(c)Geomentrical relationship between the ?ame and the wall. Z.Gao et al./Applied Thermal Engineering 33-34(2012)15e 2321 was about 2540K at point 5.The contact area had an apparent in ?uence on the current and resulted in a local maximum value on the post-?ame stage,as shown in Fig.9. 4.4.Correlation between the ion current and the temperature at different positions Fig.11presents the ion current obtained by the detector elec-trodes in different parallel distances (h ?0,10,15,20,25mm)from the ignition electrodes.It can be seen in Fig.11that all the current curves contained the front-?ame and post-?ame stages,and that the local and global maximum values of all the post-?ame ion currents occurred at nearly the same time. The amplitude of the current on the front-?ame stage decreased with the increase in the distance because the density of the chemi-ions formed in the ?ame kernel decreased gradually with the propagation of the ?ame.The timing of the appearance of the front-?ame current was postponed because the duration of the chemi-ions diffusion to the detector electrodes increased with the increased parallel distance h .The local maximum values appeared at nearly the same time because the ?ame in each combustion process propagated in a similar way and the largest contact area between the front-?ame and the internal wall occurred at almost the same time after ignition. To clarify the relationship between the post-?ame current and the temperature,the calculated temperatures at the detector electrode gap are shown in Fig.12.The in ?exions between the front-?ame and post-?ame stages at different distances (h ?0,10,15,20,25mm)are also marked in Fig.12.The temperatures at the in ?exions were all about 2000K,indicating that 2000K was the pivotal factor for the NO tand current generation.As shown in Fig.12,the temperatures corresponding to the local maximum currents decreased with the increase in distances,while the in ?u-ence of the contact area became more obvious with the increase in the parallel distance.Thus,the contact area affected the current more markedly with the decrease in temperature.The global maximum value of the current on post-?ame stage decreased with the increase in distance due to the decrease in temperature.Therefore,the global maximum values of current on post-?ame stage appeared at nearly the same time,just as the maximum temperatures did. Fig.13presents the relationship of the current on post-?ame stage and temperature in different parallel distances.When the temperature was higher than 2000K,the current on post-?ame stage appeared.The ion current showed a nearly linear relation-ship with the temperature.The higher the temperature was,the larger the current generated by NO twas.When temperature increased from 2000K to 3000K,the current increased from 5m A to 40m A with an increasing slope of 0.0357m A/K.This means that a temperature rise of 100K raised the current by about 3.6m A.5.Conclusions An experimental study of the relationship between ion current and temperature at the electrode gap was conducted in a constant volume combustion bomb.The main conclusions are summarized as follows: (1)When the ignition electrodes were used for detection,the ion current had three phases,ignition,front-?ame stage and post-?ame stage,with one-peak value.In contrast,when the detector electrodes,in combination with the ignition elec-trodes,were used for detection,the ion current showed two phases,front-?ame and post-?ame,with two peak values.The ignition stage and part of the front-?ame stage were missing.(2)Post-?ame current is directly related to the temperature.When the temperature was higher than 2000K,the current on post-?ame stage appeared due to the generation of NO tions,and there was a linear relationship between the temperature and the NO tions. (3)Both chemi-ionization and thermal-ionization contributed to the appearance of the current on the post-?ame stage when Fig.11.The ion current in different parallel distances. Fig.12.The temperature at the electrode gap of different parallel distance. Fig.13.Ion current value versus temperature. Z.Gao et al./Applied Thermal Engineering 33-34(2012)15e 23 22 the combustion chamber was connected with cathode elec-trode.The contact area between the?ame front and the internal walls led to the local maximum value since the temperature at the detector electrodes was lower than that at the ignition electrodes.The lower the temperature at the electrode gap was,the more obvious the local peak was. (4)With the increase in the distance between the detector elec- trodes and the ignition electrodes,the ion current decreased, and the timings of the appearances of the front-?ame and post-?ame currents were both postponed.The maximum temper-ature values and the global maximum values of post-?ame currents appeared at almost the same time. Acknowledgements This study is supported by National Science Foundation of China (No.50876087)and National Basic Research Project(No. 2007CB210006). References [1]Y.Shimasaki,M.Kanehiro,S.Baba,S.Maruyama,T.Hisaki,S.Miyata,Spark plug voltage analysis for monitoring combustion in an internal combustion engine,SAE Technical Paper930461(1993). [2] A.Frank,P.Einewall,B.Johnhansson,W.Nicholas,R.Raymond,L.Anders,The effect of in-cylinder gas?ow on the interpretation of ionization sensor signal, SAE Technical Paper2003-01-1120(2003). [3] E.Depussay,C.Mounaim,S.Burnel,A probe to estimate the local fuel concen- tration in spark ignition engines:design and validation study of catalytic hot wire probe,Flow Measurement and Instrumentation12(2001)313e325. [4]Y.Moudden,A.Seghouane,O.Bouba,Extraction of peak pressure position information from the spark-plug ionization signal,Computer Standards and Interfaces24(2002)161e170. [5]P.Attard,J.Micallef,Ion current combustion technology for controlled auto- ignition gasoline engines,Engine Research8(2007)429e437. [6] A.Saitzkoff,R.Reinmann, F.Mauss,M.Glavmo,In-cylinder pressure measurements using the spark plug as an ionization sensor,SAE Technical Paper970855(1997). [7]X.W.Wu,K.Li,D.M.Jiang,Investigation of air-fuel ratio control using ionic current signal:proceeding of the institution of mechanical engineering,part D,Journal of Automobile Engineering221(9)(2007)1139e1148. [8] A.Franke,P.Einewall,B.Johansson,R.Reinmann,Employing an ionization sensor for combustion diagnostics in a lean burn natural gas engine,SAE Technical Paper2001-01-0992(2001). [9]S.Yoshiyama,E.Tomita,Combustion diagnostics of a spark ignition engine using a spark plug as an ion probe,SAE Technical Paper2002-01-2838(2002). [10]S.R.Thorsteinn,J.C.ian, E.G.Stan, C.Carlsson,M.Hellring,R.Jessica, https://www.wendangku.net/doc/b86163126.html,rsson,T.Munther,N.Wickstrom,Robust AFr estimation using the ion current and neural networks,SAE Technical Paper1999-01-1161(1999). [11] D.Schneider,https://www.wendangku.net/doc/b86163126.html,i,Real-time air/fuel control in a small engine using the ionic current signal,SAE Technical Paper1999-01-3323(1999). [12]H.Klovmark,P.Rask,U.Forssel,Estimating the air/fuel ratio from gaussian parameterizations of the ionization current in internal combustion SI Engines, SAE Technical Paper2000-01-1245(2000). [13] C.Daniels,G.G.Zhu,W.James,Inaudible knock and partial-burn detection using in-cylinder ionization signal,SAE Technical Paper2003-01-3149(2003). [14]M.Asano,T.Kuma,M.Kajitanl,Takeuchi Manabu,Development of new ion current combustion control system,SAE Technical Paper980162(1998). [15]L.Eriksson,L.Nielsen,M.Glavenius,Closed loop ignition control by ionization current interpretation,SAE Technical Paper970854(1997).[16]T.Huang,D.Mehta,Investigation of an in-cylinder ion sensing assisted HCCI control strategy,SAE Technical Paper2005-01-0068(2005). [17]L.Eriksson,L.Nielsen,Ionization current interpretation for ignition control in internal combustion engines,Control Engineering Practice5(8)(1997) 1101e1113. [18]Y.Hirano,T.Suzuki,Y.Hashimoto,et al.,Fundamental characteristics of cylindrical electrostatic probe for examining premixed?uctuated?ames, Transactions of the Japan Society of Mechanical Engineers e Part B46(405) (1980)1007e1015in janpanese. [19]T.Suzuki,Y.Hashimoto,L.Mashiko,T.Hirano,Ion-current?uctuations recorded with a cylindrical electrostatic probe passing premixed?ames, Combustion and Flame36(1979)179e192. [20]H.Kubach,A.Velji,U.Spicher,W.Fischer,Ion current measurement in diesel engines,SAE Technical Paper2004-01-2922(2004). [21]L.Peron,A.Charlet,P.Higelin,Limitations of ionization current sensors and comparison with cylinder pressure sensors,SAE Technical Paper2000-01-2830(2000). [22] A.Franke,P.Einewall,https://www.wendangku.net/doc/b86163126.html,rsson,R.Reinmann,Analysis of the ionization equilibrium in the post-?ame zone,SAE Technical Paper2003-01-1715 (2003). [23]I.Andersson,A comparison of combustion temperature models for ionization current modeling in an SI engine,SAE Technical Paper2004-01-1465(2004). [24] A.Saitzkoff,R.Reinmann,T.Berglind,An ionization equilibrium analysis of the spark plug as an ionization sensor,SAE Technical Paper960337(1996). [25]M.Thiele,M.Thiele,S.Selle,J.Warnatz,R.Schiessl,U.Maas,A detailed two- dimensional numerical study of spark ignition including ionization,SAE Technical Paper2002-01-1110(2002). [26]M.Bach,J.Reissing,U.Spicher,Temperature measurement and no determi- nation in SI engines using optical?ber sensors,SAE Technical Paper961922 (1996). [27]M.Z.Xie,Computational combustion theory of internal combustion engine Da lian(2005)4e5 [28]G.M.Rassweiler,L.Withrow,Motion pictures of engine?ames correlated with pressure cards,SAE Technical Paper800131(1980). [29] https://www.wendangku.net/doc/b86163126.html,w, C.J.Sung,Structure aerodynamics and geometry of premixed ?amelets,Progress in Energy and Combustion Science26(4e6)(2000) 459e505. [30] D.M.Jiang,Theory of the Internal Combustion Engine Xi’an(1988)pp. 106e177. [31]H.F.Calcote,Ion and electron pro?les in?amesNinth symposium(interna- tional)on combustion,(1963)622e634. [32]M.J.Hall,The in?uence of?uid motion on?ame kernel development and cyclic variation in a spark ignition engine,SAE Technical Paper890991(1989). [33]S.Yoshiyama,E.Tomita,Y.Hamamoto,Fundamental study on combustion diagnostics using a spark plug as ion probe,SAE Technical Paper2000-01-2828(2000). [34]Y.Shimasaki,H.Maki,J.Sakguchi,K.Nishizawa,A.Kato,H.Suzuki,N.Kondo, T.Yamada,Study on combustion monitoring system for formula one engines using ionic current measurement,SAE Technical Paper2004-01-1921(2004). [35] D.Upadhyay,G.Rizzonl,AFR control on a single cylinder engine using the ionization current,SAE Technical Paper980203(1998). [36]J.Heywood,Internal Combustion Engine Fundamentals.Mcgraw-hill Book Company,1988,572e586. [37]X.M.Wu,Z.Q.Gao,D.M.Jiang,Z.H.Huang,Experimental investigation of effect of electrodes on ionization current during combustion,Energy&Fuel22(5) (2008)2941e2947. [38] D.Schneider,An Experimental Study of Correlations Between Ionic Current and Operating Parameters in SI Engine,USA:Dissertation for degree of PhD Bell&Howell information and learning(2000)10e22. [39] https://www.wendangku.net/doc/b86163126.html,w,G.Jomaas,J.K.Bechtold,Cellular instabilities of expanding hydrogen/ propane spherical?ames at elevated pressures:theory and experiment, Proceedings of the Combustion Institute30(1)(2005)159e167. [40] D.Bradly,R.A.Hicks,https://www.wendangku.net/doc/b86163126.html,wes,C.G.W.Sheppard,R.Woolley,The measure- ment of laminar burning velocities and markstein numbers for iso-octane e air and iso-octane e n-heptane e air mixtures at elevated temperatures and pressures in an explosion bomb,Combustion and Flame115(1e2)(1998) 26e144. Z.Gao et al./Applied Thermal Engineering33-34(2012)15e2323 离子通道研究进展 陆亚宇（江苏教育学院生物系） 指导老师：戴谷（江苏教育学院生物系） 摘要：随着对离子通道研究的逐步深入, 各种研究方法都暴露出一定的局限性. 目前, 对于离子通道的研究工作进入了一个新阶段,即对不同方法的综合应用阶段,这不仅有助于人们在分子水平上认识离子通道的结构和功能的关系,也为不同领域的科学家提供了更多的合作机会.首先介绍了离子通道理论及实验研究方法, 并分析了各种研究方法综合应用的必要性,展望了这一领域的发展前景及其所面临的挑战性问题.并介绍最新的全自动膜片钳技术及其最新进展,它具有直接性、高信息量及高精确性的特点。近来在多个方面作出新的突破,如高的实验通量表现,较高的自动化程度、良好的封接质量、微量加样等。目前,该技术在以离子通道为靶标的药物研发,药物毒理测试以及虚拟药筛等方面有广阔的应用前景。全文对全自动膜片钳仪器的原理和技术细节作简单介绍。并简单介绍最新的关于K+通道在烟草中的发现，并对利用现代生物技术手段提高烟叶含钾量进行了展望。 关键字：离子通道; 实验方法; 全自动膜片钳；钾离子通道 前言： 细胞是通过细胞膜与外界隔离的,在细胞膜上 有很多种离子通道（如右图）,细胞通过这些 通道与外界进行离子交换。离子通道在许多细 胞活动中都起关键作用,它是生物电活动的基 础,在细胞内和细胞间信号传递中起着重要作 用。随着基因组测序工作的完成,更多的离子 通道基因被鉴定出来,离子通道基因约占 1 . 5% ,至少有400个基因编码离子通道。相应的 由于离子通道功能改变所引起的中枢及外周疾 病也越来越受到重视。 离子通道的实验研究最初主要来源于生理学实 验。1949～1952年, Hodgkin等发展的“电压钳 技术” 为离子通透性的研究提供技术条件。60 年代中期,一些特异性通道抑制剂的发现为离 子通道的研究提供有力武器。1976年Neher和 Sakmann发展的膜片钳技术直接记录离子单通 道电流,为从分子水平上研究离子通道提供直 接手段。80年代中期,生化技术的进步,分子生物学以及基因重组技术的发展,使人们能够分离纯化许多不同的通道蛋白,直接研究离子通道的结构与功能关系。 通道结构和功能的研究日益成为电生理学、分子生物学、生物化学、物理学等多学科交叉的热点问题.对离子通道进行研究,传统的实验方法是电压钳技术、膜片钳技术等电生理学研究方法[; 传统的理论方法主要包括PNP模型和布朗动力学模型, 伴随计算机技术的迅猛发展和X 射线晶体衍射图谱技术在离子通道研究中的应用, 以及Mackinnon 等用X 射线晶体衍射技术成功解析出多个高分辨率离子通道三维空间结构,使得人们得以使用分子动力学模拟和量子化学计算等模拟在分子水平认识离子通道结构和功能的关系;随着分子生物学快速发展,又出现了定点突变技术、人工膜离子通道重建技术等实验技术手段本文中,笔者将 一、电离平衡理论和水解平衡理论 1.电离理论：⑴弱电解质的电离是微弱的，电离消耗的电解质及产生的微粒都是少量的，同时注意考虑水的电离的存在；例如NH3·H2O溶液中微粒浓度大小关系。 【分析】由于在NH3·H2O溶液中存在下列电离平衡：NH3·H2O NH4++OH-，H2O H++OH-，所以溶液中微粒浓度关系为：c(NH3·H2O)＞ c(OH-)＞c(NH4+)＞c(H+)。 ⑵多元弱酸的电离是分步的，主要以第一步电离为主；例如H2S溶液中微粒浓度大小关系。 【分析】由于H2S溶液中存在下列平衡：H2S HS-+H+，HS- S2-+H+，H2O H++OH-，所以溶液中微粒浓度关系为：c(H2S)＞c(H+)＞c(HS-)＞c(OH-)。 2.水解理论： ⑴弱酸的阴离子和弱碱的阳离子因水解而损耗；如NaHCO3溶液中有：c(Na+)＞c(HCO3-)。 ⑵弱酸的阴离子和弱碱的阳离子的水解是微量的（双水解除外），因此水解生成的弱电解质及产生H+的（或OH-）也是微量，但由于水的电离平衡和盐类水解平衡的存在，所以水解后的酸性溶液中c(H+)（或碱性溶液中的c(OH-)）总是大于水解产生的弱电解质的浓度；例如（NH4）2SO4溶液中微粒浓度关系。 【分析】因溶液中存在下列关系：（NH4）2SO4=2NH4++SO42-， 2H2O2OH-+2H+， 2NH3·H2O，由于水电离产生的c(H+)水=c(OH-)水，而水电离产生的一部分OH-与NH4+结合产生NH3·H2O，另一部分OH-仍存在于溶液中，所以溶液中微粒浓度关系为：c(NH4+)＞c(SO42-)＞c(H+)＞c(NH3·H2O)＞c(OH-)。 ⑶一般来说“谁弱谁水解，谁强显谁性”，如水解呈酸性的溶液中c(H+)＞c(OH-)，水解呈碱性的溶液中 c(OH-)＞c(H+)； ⑷多元弱酸的酸根离子的水解是分步进行的，主要以第一步水解为主。例如Na2CO3溶液中微粒浓度关系。【分析】因碳酸钠溶液水解平衡为：CO32-+H2O HCO3-+OH-，H2O+HCO3-H2CO3+OH-，所以溶液中部分微粒浓度的关系为：c(CO32-)＞c(HCO3-)。 二、电荷守恒和物料守恒 1．电荷守恒：电解质溶液中所有阳离子所带有的正电荷数与所有的阴离子所带的负电荷数相等。如NaHCO3溶液中：n(Na+)＋n(H+)＝n(HCO3-)＋2n(CO32-)＋n(OH-)推出：c(Na+)＋c(H+)＝c(HCO3-)＋2c(CO32-) 流动电流检测器（SC5200型流动电流检测仪） 一.功能原理 流动电流检测器简称SCD，可以用于检测水样中胶体离子的荷电特性，主要由检测水样的传感器和检测信号的放大处理器两部分构成。而SC5200型的检测器是目前在控制混凝剂投加上的优先选择之一。它的结构及工作原理如下： SC5200流动电流检测仪集取样探头，信号处理及PID控制器于一体、探头内壁与柱塞间隙0.014英寸。 SCD是动电荷的在线分析装置，为混凝过程提供检测、记录和控制功能，是唯一一种直接测量混凝剂投加剂效果的最佳在线仪表。它可测控经化学处理后的废水样中，使水中的带电离子或颗粒在SCD 取样室内的两个电极之间产生电流。电极埋置于塑料壳体中，电机驱动活塞在壳体中做往复运动产生剪切作用，推动离子并带动水中离子趋向电极，从而形成流动电流信号，它的大小决定混凝后仍留在水中的正（负）离子的净余量。 来自探头电极的流动电流信号，由主电路板处理，主电路板还接收电机轴开槽圆盘的计时信号，其结果是输出一个4~20mA信号，并显示流动电流单位，此信号与水样的带电状态成比例，故可用以检测或控制混凝过程。 二.SC5200型流动电流检测仪的特点 它可以连续检测混凝过程，因此在变化的处理状态下可提供一致的水质，还可以帮助保持：1.同水中悬浮固体含量成比例，均匀投加药 剂；2.不管悬浮固体量和原水流量的波动，均匀投加药剂；3.不管混凝剂浓度变化，均匀投加药剂。 检测仪的稳定运行需要优质的水样，因此SCD装置的水样应满足以下主要四点：1.水样能代表所检测和控制过程；2.水样应不含损坏探头或阻碍水样流动的异物；3.在SCD运行过程中，水样应是连续的；4.选取取样点时应提供合适的系统延迟时间。 三.SC5200型流动电流检测仪在净水处理中的应用 投药是水净化处理中的一个重要环节，其投量是根据原水流量和连续流而定的。采用SC5200自动投药系统的话，由于SC5200具有完整的流动信号检测处理和过程控制器双重功能，可控制任何可接收4~20mA过程信号的混凝剂投加泵或控制阀，因此系统中无需其他控制仪表。 在净水处理的应用中，SC5200具有以下的效用： 1.即使水质、水流或环境等外部条件变动，也可保证出水水质恒定； 2.混凝剂的消耗量可降至最低，从而降低成本； 3.由于是最佳的混凝剂投加，可以减少污泥量； 4.由于污泥形成减少，延长了过滤周期； 5.由于是最佳混凝剂投加，PH控制更为严格； 6.加药过程可以实现自动化。 SCD的应用，使出水水质在受到外界干扰的情况下仍保持稳定。 四.结束语 在水处理的应用中，SCD起着很重要的作用。通过SCD检测的原水SC电流响应值，来确定混凝剂的最佳投加量，从而在保证、提高 离子通道病 定义:离子通道结构的缺陷所引起的疾病.又称离子通道缺陷性疾病。 与信号传导相关的离子通道获得性或遗传性的结构和功能改变,均可能导致响应的信号传导异常,引起某种疾病或参与疾病的发病过程。如；肌肉型nAch受体自身免疫性损害-----重症肌无力；CI-通道CIC1基因缺陷-----先天性肌强直：Ryarodine受体缺陷------恶性高热易感性。 细胞膜上电压调控性钠、钙、钾和氯离子通道功能改变与先天性和后天性疾病发生之间的关系，对于离子通道基因缺陷、功能改变与某些疾病关系的研究，将可更新在离子通道生理学、病理学和分子遗传学等方面的知识，有助于开辟离子通道病治疗新途径。 90年代以来发现的主要离子通道病: 第一节钠通道病 钠通道基因突变所引起的心律失常，其原因可分为：基于通道活动的失活异常（不完全失活）；基于通道激活异常（Ina降低）；基于细胞膜上通道的数量减少（合成、运输及表达障碍)。钠通道分子结构上的有关部门位点发生突变时，就会严重影响钠通道的正常活动，而出现致命性心律失常。 所有钠通道基因突变所引起的疾病主要与α-亚单位的基因改变有关。在心肌细胞，位于染色体3p21-24上的SCN5A基因与钠通道（hH1）的组成有关。该基因突变是造成人类第3型长Q-T综合症（LQT3）的根本原因。先天性长Q-T综合症是一种罕见且致死的心脏电复极化过程异常延长性心律失常，心电图上QT间期延长，出现室性心律失常、晕厥和瘁死的一种综合症。与正常结构相比，在由突变SCN5A形成的钠通道α亚单位上，位于Ⅲ和Ⅳ结构域之间的4和5号片段有脯氨酸、赖氨酸和谷氨酰胺缺失现象。破坏了通到连接攀与通道的相互作用，使部分通道变为非失活的形式，通道失活的延迟导致持续的Na+内流，延长心肌复极时间，导致QT间期延长。 LQT与一些基因的突变或缺失有关，这些基因分别命名为LQT1---LQT4。 LQT1，LQT2是主要的心脏钾通道病。 离子电流检测电路与优化设计研究 摘要： 关键字： 0引言 内燃机燃烧时会产生大量的自由电子、正负离子和自由基等带电粒子，使混合气具有一定的导电性。对于火花点火式发动机，如果在火花塞两极之间加上适当的直流偏置电压就会形成离子电流[1]；对于压缩自燃式发动机例如柴油机，也可以通过自加电极的方式形成离子电流[2]。离子电流包含大量发动机燃烧和运转信息，通过信号检测和处理可以对缸内燃烧过程进行表征和反馈控制。同时离子电流检测无需对发动机进行大规模的改动也不受发动机结构布局和燃料类型限制，能够应用于几乎所有燃料的内燃机。目前关于离子电流的应用，国内外相关机构已做了大量的研究。Nick Collings[3]基于一台PFI 汽油机研究了空燃比、燃烧时刻和燃油成分对离子电流的影响，提出和证明了离子电流法在火花塞积碳检测中的应用及其可行性。Stefan Byttner等[4]利用离子电流信号评估了缸内循环变动（COV）。研究结果表明，在小负荷工况下，火花塞离子电流信号循环变动与平均有效压力循环变动之间存在正相关性。吴筱敏等[5-7]对离子电流在失火检测、爆震控制以及空燃比检测等方面做了大量研究。李理光等[8-11]基于离子电流制定了GDI-HCCI发动机循环间燃烧相位的反馈控制策略，结果显示，控制后缸压及平均指示压力等参数的循环波动明显减少，HC排放得到改善。又对一台两阶段喷射GDI发动机起动过程的离子电流特性进行了细致研究，并在此基础上基于燃烧循环的控制思想进行了失火检测和补火控制，有效减少了冷起动过程中的HC排放。 要想实现离子电流在发动机上的相关应用，稳定可靠的检测电路是基础。对检测电路的要求主要有以下三点：1、检测到的信号真实准确，2、信号数值范围适当，3、具备一定抗干扰能力。针对上述要求，本文先是比较了目前所采用的离子电流检测电路的优缺点，并对其中一种电路进行了优化设计。在一台两阶段喷射直喷汽油机上进行了试验验证，结果表明改进后的检测电路能够更好满足要求。 1离子电流检测电路对比分析 目前所采用的离子电流检测电路按电源的形式可以分为外接电源式和电容式两种。两种电路各有其优缺点，下面将分别对这两种电路进行分析。 外接电源式离子电流检测电路 外接电源式离子电流检测电路的基本结构如所示[9]。从图中可以看出，该电路主要由高压隔离模块、分压电路和偏置电源等三部分组成。高压隔离模块是为了防止点火高压对检测回路造成干扰和冲击，由高压硅堆和电阻R3并联而成；偏置电源是整个检测回路的电源部分，一般可通过DC/DC升压模块将车用蓄电池的12V电压转换为所需要的适合电压值；分压电路部分是整个检测电路的信号输出部分，由于回路中离子电流值较小，直接测量电流值相对困难且难以保证测量精度，通过串联分压电阻的作用，使得回路中的电流即待测离子电 第四章钠通道激动剂、阻滞剂 第一节概述 钠通道的一个重要特性就是具有特异的激动剂和阻滞剂。这些激动剂和阻滞剂主要是神经毒素和作用于中枢及心脏钠通道的药物。钠通道是许多特异性天然动植物神经毒素作用的靶器。这些毒素可调节钠通道的各种功能活性，包括通道的电导、激活和失活等，进而影响电信号产生与传导过程，使动物麻痹，甚至死亡。电压门控型钠通道上至少存在7个不同的神经毒素结合靶位点（见图2-6-1）。河豚毒素（tetrodotoxin，TTX）、蛤蚌毒素（saxitoxin，STX）和芋螺毒素（conotoxin，CTX）作用于位点1，阻断通道外口，但不改变通道动力学和门控性质；蟾毒素（batrachotoxin，BTX）、木藜芦毒素（grayanotoxin ，GTX）和乌头碱（aconitine）等作用于位点2，可持续激活钠通道；北非蝎α-毒素(North African scorpion α-toxin)，海洋海葵毒素(Sea-anemone toxins, ATX)它们分别从北非蝎和海葵中分离和提炼出来的碱性水溶性多肽毒素，作用于位点3，其受体部位在通道外侧，使钠通道缓慢失活，并增强其持续激活。表2-4-1列出了电压门控性钠通道（VGSC）的毒素结合位点及生理效应。 钠通道蛋白的提纯，就是利用它与毒素选择性的结合而进行的。首先用非离子的清洁剂(detergent) 使可兴奋膜上的钠通道蛋白溶解，然后再通过选择性毒素与该蛋白结合。最后再用常规生化方法进行纯化。许多毒素对钠通道有选择性结合作用，主要工作是在神经细胞上发现的。虽然在骨骼肌细胞与心肌细胞膜上均有钠通道，而且其分子结构与神经细胞上的钠通道相似，但它们对毒素的亲和力并不相同。例如，心肌细胞钠通道对TTX的亲和力比脑及骨骼肌细胞弱100-1000 倍。 表2-4-1 电压门控性钠通道（VGSC）的毒素结合位点 结合位点神经毒素生理效应 1 河豚毒素(Tetrodotoxin ,TTX) 离子通道阻滞→抑制离子转运 蛤蚌毒素(Saxitoxin,STX) μ-芋螺毒素（μ-Conotoxins，μ-CTX） 2 藜芦定(Veratridine) 持续激活 蟾毒素(Batrachotoxin ,BTX) 乌头碱(Aconitine) 木藜芦毒素(Grayanotoxin,GTX) 3 北非蝎α-毒素(North African scorpion α-toxin) 缓慢失活; 增强持续激活 海洋海葵毒素(Sea-anemone toxins, ATX) δ-Atracotoxins 4 北非蝎β-毒素(American scorpion β-toxin) 短暂反复激活；电压依赖性激活移向更负的 盐溶液中离子浓度大小的比较一、基本知识在盐溶液中存在平衡：水的电离平衡、盐的水解、弱电解质的电离平衡。 （H＋）与c（OH－）的关系： 中性溶液：c（H＋）＝c（OH－）（如NaCl溶液） 酸性溶液：c（H＋）＞c（OH－）（如NH4Cl溶液） 碱性溶液：c（H＋）＜c（OH－）（如Na2CO3溶液） 恒温时：c（H+）·c（OH－）＝定值（常温时为10－14） 2.电荷守恒：盐溶液中阴、阳离子所带的电荷总数相等。 如NH4Cl溶液中：c（NH4+）＋c（H+）＝c（Cl－）＋c（OH－） 如Na2CO3溶液中：c（Na+）＋c（H+）＝2c（CO32-）＋c（HCO3-）＋c（OH－） 3.物料守恒：某元素各种不同存在形态的微粒，物质的量总和不变。 如 mol/L NH4Cl溶液中：c（NH4+）＋c（NH3·H2O）＝ mol/L 如 mol/L Na2CO3溶液中：c（CO32-）＋c（HCO3-）＋c（H2CO3）＝ mol/L 4.质子守恒：溶液中水电离出的H＋与OH－相等 如Na2CO3溶液中：c（OH－）＝c（HCO3-）＋2c（H2CO3）＋c（H+） 二、解题方法和步骤 1.判断水解、电离哪个为主。 （1）盐离子不水解不电离：强酸强碱盐，如NaCl、Na2SO4等。 （2）盐离子只水解不电离：强酸弱碱或弱酸强碱形成的正盐，如NH4Cl、Na2CO3等。 （3）盐离子既水解又电离：多元弱酸形成的酸式盐， 以水解为主的有NaHCO3、NaHS、Na2HPO4等； 以电离为主的有NaHSO3和NaH2PO4等。 （4）根据题意判断： 如某温度下NaHB强电解质溶液中： 当c（H+）＞c（OH－）时：以HB－的电离为主； 当c（H+）＜c（OH－）时，以HB－的水解为主。 对于弱酸HX与强碱盐（NaX式）的混合溶液中： 均质压燃发动机离子电流检测技术的研究概述 摘要：均质压缩燃烧(HCCI)具有高效、低污染等优点，已逐渐成为内燃机一种新型的燃烧方式。但HCCI燃烧过程对混合气组分、温度等因素很敏感，因此对HCCI的控制和检测技术提出严格的要求。本文介绍了HCCI发动机离子电流检测技术的原理，分析了HCCI例子电流形成的机理、离子电流信号特征提取及参数估计以及精确控制HCCI燃烧的燃烧相位的方法；最后从HCCI燃烧离子电流形成机理、模型研究方面不足，离子电流信号质量较差，信噪比较低等问题；等方面阐述了HCCI发动机离子电流检测技术的发展趋势。 关键词：均质压燃离子电流离子信号检测技术 均质压缩燃烧(HCCI)具有高效、低污染等优点，已逐渐成为内燃机一种新型的燃烧方式。HCCI燃烧的过程受到化学反应动力学控制，且对混合气组分和浓度以及混合气的温度等因素非常敏感。因此，HCCI的控制和检测技术提出严格的要求。 目前，基于MAP的开环控制的常规控制手段已不能满足HCCI燃烧的控制要求，而基于缸内燃烧信息反馈的控制手段又难以达成。因此，必须采用闭环反馈的方法对HCCI的燃烧进行控制。国内外专家、学者从SI汽油机燃烧参数控制和状态检测中吸取经验，并用这种技术对HCCI燃烧特征监测和反馈控制进行研究，展现出了HCCI燃烧精确控制和HCCI发动机离子电流检测技术的前景。 1、HCCI燃烧离子电流检测技术原理 HCCI燃烧离子电流检测技术的原理：利用火花塞作为传感器，将一定的直流偏置电压施加在火花塞两极。混合气在气缸内燃烧时将产生自由离子，在偏置电压作用下定向移动，从而形成离子电流。在发动机外部联接一个检测电阻，分析检测电阻的电压信号波形即可得到缸内的燃烧信息。 SI燃烧方式下，火焰前锋期的化学电离阶段以及火焰后期热电离阶段的自由离子定向迁移形成离子电流，这是比较一致认可的结论。在有点火、火焰前锋区的化学电离和火焰后区的高温热电离三个阶段离子电流形成三个峰值。HCCI 燃烧时，气缸内的可燃混合气同时着火，并且燃烧温度较低，因此可以忽略火焰传播和混合气运动的影响。自由离子主要形成于燃烧时的化学电离阶段，在该燃烧方式下不存在点火对离子电流的干扰。 HCCI燃烧方式下，离子电流信号为单峰信号，因此相对于SI燃烧，HCCI 燃烧离子电流信号与燃烧特征参数之间的关系更为明显，更加容易提取此燃烧方式下的特征参数。所以，离子电流检测技术有望成为基于缸内燃烧信息实现HCCI 燃烧相位闭环控制的高效、低成本的一种技术，有助于推动HCCI燃烧技术的产 专题讲座：离子浓度大小关系判断 一、熟悉两论，构建思维基点 1．电离理论 (1)弱电解质的电离是微弱的，电离产生的微粒都非常少，同时还要考虑水的电离，如氨水溶液中：NH3·H2O、NH＋4、OH－浓度的大小关系是c(NH3·H2O)>c(OH－)>c(NH＋4)。 (2)多元弱酸的电离是分步进行的，其主要是第一级电离(第一步电离程度远大于第二步电离)。如在H2S溶液中：H2S、HS－、S2－、H＋的浓度大小关系是c(H2S)>c(H＋)>c(HS－)>c(S2－)。 2．水解理论 (1)弱电解质离子的水解损失是微量的(双水解除外)，但由于水的电离，故水解后酸性溶液中c(H＋)或碱性溶液中c(OH－)总是大于水解产生的弱电解质的浓度。如NH4Cl溶液中：NH＋4、Cl －、NH ＋的浓度大小关系是c(Cl－)>c(NH＋4)>c(H＋)>c(NH3·H2O)。 3·H2O、H (2)多元弱酸酸根离子的水解是分步进行的，其主要是第一步水解，如在Na2CO3溶液中：CO2－3、HCO－3、H2CO3的浓度大小关系应是c(CO2－3)>c(HCO－3)>c(H2CO3)。 二、把握三种守恒，明确等量关系 1．电荷守恒规律 电解质溶液中，无论存在多少种离子，溶液都是呈电中性，即阴离子所带负电荷总数一定等于阳离子所带正电荷总数。如NaHCO3溶液中存在着Na＋、H＋、HCO－3、CO2－3、OH－，存在如下关系：c(Na＋)＋c(H＋)＝c(HCO－3)＋c(OH－)＋2c(CO2－3)。 2．物料守恒规律 电解质溶液中，由于某些离子能够水解，离子种类增多，但元素总是守恒的。如K2S溶液中S2－、HS－都能水解，故S元素以S2－、HS－、H2S三种形式存在，它们之间有如下守恒关系：c(K ＋)＝2c(S2－)＋2c(HS－)＋2c(H2S)。 3．质子守恒规律 如Na2S水溶液中的质子转移情况图示如下： 由图可得Na2S水溶液中质子守恒式可表示：c(H3O＋)＋2c(H2S)＋c(HS－)＝c(OH－)或c(H＋)＋ 应用文献 IonFlux system 应用之一： hERG K +通道电流和药理学特性 简介 HERG (human ether-a go-go-related gene) K + 通道在心脏中高表达，是心肌动作电位三期快速复极化电流(IK r )的主要组成部分(Curran ‘95; Sanguinetti ‘95)。hERG 突变引起的功能缺失常伴随一些遗传性长QT 综合症(LQTS) 并且会增加发生严重的室性心律失常, 扭转性实行心动过速 (Tanaka ‘97; Moss ‘02)的风险。HERG 钾离子通道被作用于心脏或非作用于心脏的药物抑制，都被证实有非常大的可能性出现获得性药物诱导的长QT 综合症(LQTS)，甚至导致猝死(V andenberg, Walker & Campbell ‘01)。实际上，hERG 钾离子通道被抑制引起的副作用是近年来药物撤市的主要原因，因而药物作用于外源性表达于哺乳动物细胞的hERG 通道的体外效应评价已被 国际药品注册协调会议（International Conference on Harmonization ）推荐作为临床前安全性评价工作的一部分(ICHS7B Expert Working Group, ‘02)。 hERG 钾离子通道药物效应评价的金标准方法是手动膜片钳记录。然而，这种低通量、高成本的方法在大量的安全性筛选实验中非常受限制。近年来，全自动膜片钳技术发展越来越成熟，可以获得高通量的、可与手动膜片钳记录结果相媲美的数据。IonFlux? 系统结合了读板机的便捷和传统膜片钳技术的优秀性能。本文主要利用IonFlux 系统记录了在哺乳细胞中表达的hERG 电流以及一些阳性抑制剂对hERG 阻断效应的药理学特性分析。 材料和方法 细胞 实验中使用G418筛选的稳定表达hERG 通道的CHO 细胞（Millipore PrecisION? hERG-CHO Recombinant Cell Line, Cat# CYL3038）。细胞培养在含10%胎牛血清的Glutamax DMEM/F12 培养基 (Gibco, Cat# 11320) ，加有1% 青霉素-链霉素以及500 μg/mL G418。实验前至少提前24小时将细胞转移至30℃培养箱中，或传代后一直放置在30℃培养箱中。细胞密度不能超过90%。收集细胞时，使用Detachin (Genlantis, San Diego, CA, Cat# T100100)消化细胞，冲洗并轻柔吹打，最后细胞悬浮在细胞外液中，浓度为每毫升2-5百万个细胞。 溶液和化合物 细胞外液成分（ECS ）含有（mM ）：NaCl 145, KCl 4, MgCl 2 1, CaCl 2 2, HEPES 10, 葡萄糖 10，用NaOH 调pH 至7.4 。细胞内液成分（ICS ）含有（mM ）：KCl 120, HEPES 10, Na 2ATP 4, EGTA 10, CaCl 2 5.374, MgCl 2 1.75，用KOH 调pH 至7.2。 hERG 抑制剂购自Sigma 。化合物第一步全部溶于DMSO 中，制成高浓度的母液（10-50 mM ），然后按照浓度梯度和最终外液中的终浓度的倍数关系进行下一步的稀释，因而最终相应的DMSO 浓度为（0.1- 0.3%）。DMSO 溶液（0.1- 0.3%）作为阴性对照的记录始终开始于抑制剂作用之前， 且规定不能对电流幅度的影响超过10%。 Figure 1. IonFlux 高通量全自动膜片钳系统，采用“读板机”式模式，简化了工作流程、增加了实验通量。系统配有16通道和64通道两种型号，每天可以记录获取10,000 个数据点。 高二化学溶液中离子浓度大小比较专题（用） 一、相关知识点梳理: 1、电解质的电离 强电解质在水溶液中是完全电离的，在溶液中不存在电解质分子。弱电解质在水溶液中 是少部分发生电离的。多元弱酸如H 2CO 3 还要考虑分步电离： H 2CO 3 H+＋HCO 3 -；HCO 3 -H+＋CO 3 2-。 ２、水的电离 水是一种极弱的电解质，它能微弱地电离， H 2 O H+＋OH-。水电离出的[H+]＝[OH-] 在一定温度下，纯水中[H+]与[OH-]的乘积是一个常数：水的离子积Kw＝[H+]·[OH-]，在２５℃时，Kw＝1×10-14。 在纯水中加入酸或碱，抑制了水的电离，使水的电离度变小，在纯水中加入弱酸强碱盐、弱碱强酸盐，促进了水的电离，使水的电离度变大。 ３、盐类水解 在溶液中盐的离子跟水所电离出的H+或OH-生成弱电解质的反应，叫做盐类的水解。关于盐的水解有这么一个顺口溜“谁弱谁水解，谁强显谁性” 多元弱酸盐还要考虑分步水解，如CO 32-＋H 2 O HCO 3 -＋OH-、HCO 3 -＋H 2 O H 2 CO 3 ＋OH-。 ４、电解质溶液中的守恒关系 电荷守恒：电解质溶液中所有阳离子所带有的正电荷数与所有的阴离子所带的负电荷数相等。 如Na 2CO 3 溶液中：[Na+]＋[H+]＝[HCO 3 -]＋2[CO 3 2-]＋[OH-] 物料守恒：电解质溶液中由于电离或水解因素，离子会发生变化变成其它离子或分子等，但离子或分子中某种特定元素的原子的总数是不会改变的。 如Na 2CO 3 溶液中n(Na+)：n(c)＝2：1，推出： c(Na+)＝2c(HCO 3 -)＋2c(CO 3 2-)＋2c(H 2 CO 3 ) 水的电离守恒（也称质子守恒）：是指在强碱弱酸盐或强酸弱碱盐溶液中，由水所电离的H＋与OH－量相等。 如在0.1mol·L－1的Na 2S溶液中：c(OH－)＝c(H＋)＋c(HS－)＋2c(H 2 S)。 质子守恒：电解质溶液中分子或离子得到或失去质子（H+）的物质的量应相等。例如在NH 4 HCO溶液中H O+、H CO为得到质子后的产物；NH、OH-、CO2-为失去质子后的产物，故有以下关系： c(H 3O+)+c(H 2 CO 3 )=c(NH 3 )+c(OH-)+c(CO 3 2-)。 列守恒关系式要注意以下三点： ①要善于通过离子发生的变化，找出溶液中所有离子和分子，不能遗漏。 ②电荷守恒要注意离子浓度前面的系数；物料守恒要弄清发生变化的元素各离子的浓 度与未发生变化的元素之间的关系；质子守恒要找出所有能得失质子的微粒，不能遗漏。 ③某些关系式既不是电荷守恒也不是物料守恒通常是两种守恒关系式通过某种变式 而得。 解题指导 电解质溶液中离子浓度大小比较问题，是高考的“热点”之一。多年以来全国高考化 溶液中离子浓度的关系比较（Ⅰ） 王在强 引入: 溶液中离子浓度的关系比较是近几年高考的热点和难点之一，学生在解答此类型问题时，常感到思维混乱，无从下手。原因是没有抓住问题的题眼和没有形成正确的解题思维过程，从而形成解决此类问题的一般模式。本类型问题的解题思路遵循两个原则： 一、解题思路 （一）两弱原则 ①电离程度“小” 该原则主要是指弱酸、弱碱溶液的电离程度很小，产生的离子浓度也很小。适用弱电解质的溶液中离子浓度大小比较的题型，遵循的方法是：首先写出溶液中存在的所有的平衡关系，确定溶液中存在的离子种类。由于电离或水解很弱，决定了溶液中原有溶质离子或分子的浓度一定大于水解或电离得到的微粒的浓度。 1、一元弱酸或弱碱的电离 例1、0.1mol·L-1的CH3COOH溶液中的离子分子大小关系如何？ 首先写出溶液中存在的平衡关系， [投影] CH 3COOH CH3COO- + H+ H 2O H+ + OH- 由于电离或水解很弱，决定了溶液中原有溶质离子的浓度一定大于水解或电离得到的微粒的浓度，在此溶液中溶质为CH3COOH。由CH3COOH电离的c(H+)、C(CH3COO-)相等，但水会继续电离出H+，因此c(H+)＞c(CH3COO-)。由于溶液呈酸性，一般来讲c(OH-)最小，即c(CH3COOH)＞c(H+)＞C(CH3COO-)＞c(OH-) 2、多元弱酸溶液的电离 例2、0.1mol·L-1H3PO4溶液中离子分子浓度大小关系如何？ 首先写出溶液中存在的平衡关系， [投影] H 3PO4H+ +H2PO4- H 2PO4-H+ + HPO42- HPO 42-H+ +PO43- O H+ + OH- H H3PO4分三步电离，首先H3PO4少量电离出H+和H2PO4-接着H2PO4-少量电离出H+和HPO42-，由于本来电离出的H2PO4-就很少，加上它少了个H，电离的倾向就更小，所以它电离出的HPO42-会少到可以忽略，最后HPO42-少量电离出H+和PO43-就更少了 所以计量H3PO4电离能力和它的酸性只考虑第一步电离，溶液中离子分子浓度大小关系为: c(H3PO4) ＞c(H+)＞c(H2PO4-)＞c(HPO42-)＞c(PO43-)＞c(OH-) 【练习】在0.1mol/L的H2S溶液离子分子浓度大小关系如何？ 答案: c(H2S) ＞c(H+)＞c HS-)＞c(S2-)＞c( OH-) O H+ + OH- 解析：溶液存在平衡：H S HS- + H+HS-S2- + H+ H 溶液中原溶质为H2S，多元弱酸以第一步电离为主。如果溶液呈酸性，一般c( OH-)放在最后。 ②水解程度“小” 1、一元弱酸的正盐溶液 例1、CH3COONa溶液中存在的离子分子浓度大小关系： 同样先写出溶液中存在的平衡关系： 电解质溶液中离子浓度关系 一、电离平衡理论和水解平衡理论 1.电离理论： ⑴弱电解质的电离是微弱的，电离消耗的电解质及产生的微粒都是少量的，同时注意考虑水的电离的存在；例如NH3·H2O溶液中微粒浓度大小关系。 【分析】由于在NH3·H2O溶液中存在下列电离平衡：NH3·H2O NH4++OH-，H2O H++OH-，所以溶液中微粒浓度关系为： c(NH3·H2O)＞c(OH-)＞c(NH4+)＞c(H+)。 ⑵多元弱酸的电离是分步的，主要以第一步电离为主；例如H2S溶液中微粒浓度大小关系。 【分析】由于H2S溶液中存在下列平衡：H2S HS-+H+，HS- S2-+H+，H2O H++OH-，所以溶液中微粒浓度关系为：c(H2S)＞c(H+)＞c(HS-)＞c(OH-)。 2.水解理论： ⑴弱酸的阴离子和弱碱的阳离子因水解而损耗；如NaHCO3溶液中有：c(Na+)＞c(HCO3-)。 ⑵弱酸的阴离子和弱碱的阳离子的水解是微量的（双水解除外），因此水解生成的弱电解质及产生H+的（或OH-）也是微量，但由于水的电离平衡和盐类水解平衡的存在，所以水解后的酸性溶液中c(H+)（或碱性溶液中的c(OH-)）总是大于水解产生的弱电解质的浓度；例如（NH4）2SO4溶液中微粒浓度关系。 【分析】因溶液中存在下列关系：（NH4）2SO4=2NH4++SO42-， + 2H2O 2OH-+2H+， 2NH3·H2O，由于水电离产生的c(H+)水=c(OH-)水，而水电离产生的一部分OH-与NH4+结合产生NH3·H2O，另一部分OH-仍存在于溶液中，所以溶液中微粒浓度关系为：c(NH4+)＞c(SO42-)＞c(H+)＞c(NH3·H2O)＞c(OH-)。 电解质溶液中离子浓度的主要关系 1．知识与技能目标：能熟练判断电解质溶液中离子浓度的主要关系并会简单应用，2．过程与方法目标：学会正确解答问题的思路和方法,培养良好的思维品质,提高分析和解决问题的能力， ,养成良好的学习习惯， 电解质溶液中离子浓度的主要关系及应用 2．电解质溶液中离子浓度的关系主要考查类型有哪几种？ 1．在氯化铵溶液中,下列关系式正确的是（） A．c (Cl-)＞c (NH4+)＞c (H+)＞c(OH-) B．c(NH4+)＞c(Cl-)＞c(H+)＞c(OH-) C．c (Cl-)＝c (NH4+)＞c (H+)＝c (OH-) D．c (NH4+)＝c (Cl-)＞c (H+)＞c (OH-) 2．CH3COOH与CH3COONa等物质的量混合配制成的稀溶液,pH为4.7，下列说法错误的是（） A．CH3COOH的电离作用大于CH3COONa的水解作用， B．CH3COONa的水解作用大于CH3COOH的电离作用， C．CH3COOH的存在抑制了CH3COONa的水解， D．CH3COONa的存在抑制了CH3COOH的电离， 3．25℃时,将等体积的盐酸和氨水混合后,若溶液中c（NH4+）= c（Cl-）,则溶液的pH为（） A．大于7 B. 小于7 C．等于7 D．无法确定 4．在25℃时,在浓度为1mol/L的(NH4)2SO4、(NH4)2CO3、(NH4)2Fe(SO4)2的溶液中,测得其c(NH4＋)分别为a、b、c（单位mol/L），下列判断正确的是（） A．a＝b＝c B．a>b>c C．a>c>b D．c>a>b 5．在Na2S溶液中,各微粒间浓度关系如下: (1) c(Na+)+ c(H+) = c(OH-)+ + (2) c(Na+) =2c(S2-) + + 已知某溶液中只存在OH—、H+、NH4+、Cl—四种离子,某同学推测其离子浓度大小顺序有如下四种关系： ①c(Cl－)＞c(NH4+)＞c(H+)＞c(OH－) ②c(Cl－)＞c(NH4+)＞c(OH－)＞c(H+) ③c(NH4+)＞c(Cl－)＞c(OH－)＞c(H+) ④c(Cl－)＞c(H+)＞c(NH4+)＞c(OH－) 填写下列空白： （1）若溶液中只溶解了一种溶质,则该溶质是,上述四种离子浓度的大小顺序为（填序号）， （2）若上述关系中③是正确的,则溶液中的溶质为；若上述关系中④是正确的,则溶液中的溶质为， （3）若该溶液是由体积相等的稀盐酸和氨水混合而成,且恰好呈中性,则混合前 c(HCl) c(NH3·H2O)（填“大于”、“小于”或“等于”,下同）,混合前酸中c(H+)和碱中c(OH－)的关系c(H+) c(OH－)， 有关溶液中离子浓度的大小比较题型归纳及解题策略 电解质溶液中离子浓度大小比较问题，是高考的“热点”之一。多年以来全国高考化学试卷几乎年年涉及。这种题型考查的知识点多，灵活性、综合性较强，有较好的区分度，它能有效地测试出学生对强弱电解质、电离平衡、水的电离、pH 、离子反应、盐类水解等基本概念的掌握程度及对这些知识的综合运用能力。现结合07年各省市高考试题和模拟题谈谈解答此类问题的方法与策略。 一、要建立正确一种的解题模式 1．首先必须有正确的思路： 2．要养成认真、细致、严谨的解题习惯，要在平时的练习中学会灵活运用常规的解题方法，例如：淘汰法、定量问题定性化、整体思维法等。 二、要注意掌握两个微弱观念 1．弱电解质的电离平衡 弱电解质电离的过程是可逆的、微弱的，在一定条件下达到电离平衡状态，对于多元弱酸-+-HS +H ，H 的电离，可认为是分步电离，且以第一步电离为主。如在S 的水溶液中：H S HS 222-+S+H ， ++-2-－－。c(OH ＞c(S)H)+OH ，则离子浓度由大到小的顺序为c(H)＞c(HS ＞) O H 22．盐的水解平衡 在盐的水溶液中，弱酸根的阴离子或弱碱的阳离子都会发生水解反应，在一定条件下达到水解平衡。在平衡时，一般来说发生水解反应是微弱的。多元弱酸根的阴离子的水解，可认为2－＋COHO 是分步进行的，且依次减弱，以第一步为主。 如在NaCO 溶液中存在的水解平衡是：2332++－－2－－－－－ ）。＞c ＞c(OH （)＞c(HCOHCO ＋OH ＋，HCO ＋HO HCOOHH ，则c(Na)＞c(CO))3322333 三、要全面理解三种守恒 关系电解质溶液中所有阳离子所带有的正电荷数与所有的阴离子所带的负电荷数．电荷守恒：1 相等。++2－－++－cc )(Na(H)＋2n(CO))＋n(OH ＋)推出：n(Na 例如： NaHCO 溶液中：n(H)＋n(HCO)＝333－2－－ccc ) (HCO))＋2(CO ＋＝(OH 33离子会发生变化变成其它离子或分子等，电解质溶液中由 于电离或水解因素，2．物料守恒： 但离子或分子中某种特定元素的原子的总数是不会改变的。－－+2+cccc ) CO ＋＝11n(C)n(Na 溶液中例如：NaHCO)：＝：，推出：(Na)(HCO)(CO)＋(H 32333． +）的物质的量应相等。 3．质子守恒：电解质溶液中分子或离子得到或失去质 子（H +－2－为失去质子后的、COCO 为得到质子后的产物；NH 、例如：在NHHCO 溶液 中HOOH 、H 3332433产物， +－2－ccccc )(OH 。)+)+(HCO)= (NH)+ 故有以下关系：(CO(HO 32333以上三种守恒是解 题的关键，对于这一类题的如何切入、如何展开、如何防止漏洞的出现等只有通过平时的练习认真总结，形成技能，才能很好地解这一类型的题。 四、要熟悉常见题型与对策 1．单一溶质溶液中离子浓度大小关系 ① 强酸、强碱、强酸强碱盐溶液 +2－－c cc )。(OH(H))＝2＋(SO 对策：只考虑电解质的电离与水的电离。如HSO 溶 液中，442② 弱酸或弱碱溶液 +－2－ccc ))(H ＞)＞(HPO(HPO 对策：只考虑电离。如在HPO 溶液中，要考虑它是多 【专题精讲】溶液中离子浓度大小比较归类解析 09.11 一、电离平衡理论和水解平衡理论 1.电离理论： ⑴弱电解质的电离是微弱的，电离消耗的电解质及产生的微粒都是少量的，同时注意考虑水的电离的存在；例如NH3·H2O溶液中微粒浓度大小关系。 【分析】由于在NH3·H2O溶液中存在下列电离平衡：NH3·H2O NH4++OH-，H2O H++OH-，所以溶液中微粒浓度关系为：c(NH3·H2O)＞c(OH-)＞c(NH4+)＞c(H+)。 ⑵多元弱酸的电离是分步的，主要以第一步电离为主；例如H2S溶液中微粒浓度大小关系。【分析】由于H2S溶液中存在下列平衡：H2S HS-+H+，HS-S2-+H+，H2O H++OH-，所以溶液中微粒浓度关系为：c(H2S)＞c(H+)＞c(HS-)＞c(OH-)。 2.水解理论： ⑴弱酸的阴离子和弱碱的阳离子因水解而损耗；如NaHCO3溶液中有：c(Na+)＞c(HCO3-)。 ⑵弱酸的阴离子和弱碱的阳离子的水解是微量的（双水解除外），因此水解生成的弱电解质及产生H+的（或OH-）也是微量，但由于水的电离平衡和盐类水解平衡的存在，所以水解后的酸性溶液中c(H+)（或碱性溶液中的c(OH-)）总是大于水解产生的弱电解质的浓度；例如（NH4）2SO4溶液中微粒浓度关系： c(NH4+)＞c(SO42-)＞c(H+)＞c(NH3·H2O)＞c(OH-)。 (3)多元弱酸的酸根离子的水解是分步进行的，主要以第一步水解为主。 例如: Na2CO3溶液中水解平衡为：CO32-+H2O HCO3-+OH-，H2O+HCO3-H2CO3+OH-，所以溶液中部分微粒浓度的关系为：c(CO32-)＞c(HCO3-)。 二、电荷守恒和物料守恒 1．电荷守恒：电解质溶液中所有阳离子所带有的正电荷数与所有的阴离子所带的负电荷数相等。如NaHCO3溶液中：n(Na+)＋n(H+)＝n(HCO3-)＋2n(CO32-)＋n(OH-)推出：c(Na+)＋c(H+)＝c(HCO3-)＋2c(CO32-)＋c(OH-) 2．物料守恒：电解质溶液中由于电离或水解因素，离子会发生变化变成其它离子或分子等，但离子或分子中某种特定元素的原子的总数是不会改变的。如NaHCO3溶液中n(Na+)：n(c)＝1：1，推出：c(Na+)＝c(HCO3-)＋c(CO32-)＋c(H2CO3) 离子浓度关系专题复习 崔黄口中学 杨春山 复习目标要求： 1. 掌握比较溶液中离子浓度大小的方法 2. 理解并掌握溶液中离子浓度关系，并准确快速判断关系是否正确 （1）电荷守恒 （2）物料守恒 （3）质子守恒 3. 培养分析、归纳、思维能力 （1）电离平衡理论和水解平衡理论——紧抓两个“微弱” （2）电离平衡理论: 弱电解质(弱酸、弱碱)的电离是微弱的，电离消耗的电解质及产生的微粒都是少量的。同时注意考虑水的电离的存在。 一. 适用弱电解质的溶液中离子浓度大小比较的题型。 1. 0.1 mol ·L-1 的CH3COOH 溶液中的离子、分子大小关系如何? 2．在0.1 mol/L 的NH3·H2O 溶液中，NH3·H2O 、 NH4+、 OH-、 H+的浓度由大到小的顺序是 C(NH3·H2O)＞C(OH-)＞C(NH4+)＞C(H+) 2）水解平衡理论: 弱离子(弱酸根离子、弱碱的阳离子)的水解一般是微弱的。 如：CH3COONa 溶液中存在如下关系： C(Na+)＞C(CH3COO-)＞C(OH-)＞C(CH3COOH)＞C(H+) 2.电荷守恒、物料守恒和质子守恒——牢记“三个守恒” （1）电荷守恒： 电解质溶液总是呈电中性的，即：电解质溶液中所有阳离子所带有的正电荷总数与所有的阴离子所带的负电荷总数相等。 如：NH4Cl 溶液： C(NH4+) + C(H+) ＝ C(Cl-) + C(OH-) （2） 物料守恒 : 电解质溶液中由于电离或水解因素，离子会发生变化变成其它离子或分子等，但离子或分子中某种特定元素的原子的总数是不会改变的。 如：NH4Cl 溶液： Ｃ(Cl-) ＝ Ｃ(NH4+) + Ｃ(NH3·H2O) (3）质子守恒（水的电离守恒）： 电解质溶液中，分子(或离子)得失质子(H+)的物质的量是相等。 如：NH4Cl 溶液： c(H+) ＝ c(OH -) + c(NH3·H2O) 〖训练1〗写出CH3COONa 溶液中三个守恒关系式 电荷守恒： 物料守恒： 质子守恒： 〖训练2〗写出NaHCO3溶液中三个守恒关系式 电荷守恒： 物料守恒： )()()()(33--+>>>OH C COO CH C H C COOH CH C离子通道研究进展
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