CN108931459A - Long gap streamer pilot discharge converts instant gas density measurement system and method - Google Patents
Long gap streamer pilot discharge converts instant gas density measurement system and method Download PDFInfo
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Abstract
The present invention relates to a kind of long gap streamer pilot discharge conversion instant gas density measurement system and methods, including LED chip, extender lens, main lens, plus lens, the edge of a knife, telephoto lens and the ICCD camera set gradually along optical path direction；Region of discharge is generated between main lens and plus lens, the self-luminous focusing that electric discharge generates simultaneously is passed into photomultiplier tube by coupled lens, the photomultiplier tube, which converts electric discharge self-luminous light intensity time-domain signal to voltage waveform and input TTL pulse, forms circuit, the TTL pulse forms the input terminal of the output end connection digital delay generator of circuit, and the output end of the digital delay generator is separately connected pulsed drive current source and ICCD camera.Streamer-ns grades of pilot discharge conversion process instant gas density distributing law accurate inverting measurement can be achieved in the present invention, with the high advantage of system reliability and capture rate.
Description
Technical field
The present invention relates to a kind of long gap streamer pilot discharge conversion instant gas density measurement system and methods, specially
The measuring system and method for long air gap streamer instant gas density into the dark space time that pilot discharge converts belong to high electricity
Press experimental technique discharge plasma diagnostic field.
Background technique
Long air gap, which discharges, typically refers to the atmospherical discharges phenomenon of 1m to tens of m length.Long air gap electric discharge is electricity
The basis of Force system external insulating level and lightning protection research.Streamer and pilot discharge are two of leading long air gap breakdown
Discharge subprocess, and wherein ebb-flow discharge is made of many electric discharge branches, and equivalent conductivity is low, and the free electron of generation is guide
Formation provide energy.And pilot discharge is a kind of thermal ionization phenomenon, leader channel internal conductance rate increases, and gas density reduces,
It is the main cause for causing long air gap breakdown voltage to be saturated.Thus, gas density of the streamer to pilot discharge conversion process is measured,
It is very crucial for the formation of accurate simulation guide, the breakdown voltage of prediction gap, positive polarity large air gap discharge process such as Fig. 1 institute
Show.
Streamer, which is one to pilot discharge conversion, leads to heat by free-electron collision transmitting energy, heating neutral gas molecule
The process of ionization.Currently, having in field of gas discharge for gas density, temperature thermodynamic parameter quantitative Diagnosis method：
1, spectroscopic methodology, including：(1) emission spectrometry, principle is atoms outermost by ground state to excitation state, in excitation state electricity
Son is unstable, can be given off energy in the form of light radiation, and returns to ground state or lower energy level, so that line-spectra is obtained,
For quantitative analysis；(2) absorption spectrometry, principle are to irradiate discharge channel with the light of certain wavelength, and discharge channel can absorb one
Just there are the variation of luminous intensity in part light, irradiation front and back, record this spectrum for changing and obtaining, and such as molecule, atomic absorption spectrum, use
In quantitative analysis.
2, Mach once moral M-Z laser interferance method：As shown in Fig. 2, being sent out in the gas flowfield of variations in refractive index using light
The property of raw deviation, the collimated laser beam after expanding are divided into two-way by beam splitter, are known as reference light without region of discharge, on the contrary
Referred to as object light.It is pressurizeed using surge generator to high-field electrode and generates electric discharge, since discharge channel refractive index is different from air, object
Light will generate additional light path, interfere two-way light after beam splitter converges, and generate interference item through lens corresponding position
The displacement of line.Using the stripe pattern of high-speed camera record different moments, the displacement of striped is quantitatively calculated, is finally based on
Abel inverse transformation Inversion Calculation obtains gas density, and the triggering moment of high speed camera is provided by impulse voltage generator.
3, schlieren method, including common schlieren method and quantitative schlieren method.(1) common schlieren method does not include the edge of a knife, main former
Reason is that light is generated disturbance by high-field electrode region of discharge to become obtaining discharge channel thermal region as the distribution for shielding upper light intensity
Boundary.(2) quantitative schlieren method, by the first derivative of region of discharge variations in refractive index, is transformed to edge of a knife cutting by introducing the edge of a knife
The variation of displacement and the corresponding relationship of image grayscale are measured, provides trigger signal note by using high-speed camera and by surge voltage
The gray level image for recording different moments discharge channel is obtained the quantitative distribution of region of discharge density and temperature by inverse Abel transformation inverting
Curve, quantitative schlieren type testing arrangement are as shown in Figure 3.
Big (the 1m to number of long air gap discharge breakdown voltage high (about 500kV to 2000kV range), gap geometric scale
Ten m length).Streamer-guide's conversion process duration is as short as several μ s, gas density and variations in refractive index in conversion zone
It is unobvious, initial radium is small (only 0.1mm), while streamer to pilot discharge conversion process generate and duration exist
Biggish randomness is intended to accurately obtain the thermodynamic parameter in streamer guide conversion process, not only to the time of measurement method, sky
Between resolution capability require it is high, it is necessary to solve because discharge the low problem of randomness bring capture rate.
Existing discharge gas density diagnostic method is only able to satisfy logical in stable guide development or guide's relaxation process
Road gas density, is not suitable for manoscopy of the streamer to guide's conversion process, and concrete reason is：
1, spectral diagnostics.
(1) in streamer into guide's conversion process, streamer photo-ionisation weakens, and energy conversion process is mainly neutral molecule vibration
Dynamic conversion of the kinetic energy to translational kinetic energy, leader channel own transmission light is faint, and existing spectroscopy diagnostic method is difficult to be applicable in.
(2) since long air gap discharge voltage is high, there are strong electromagnetism to emission spectrum for diagnosing equipment for discharge process
Interference, spectroscopy diagnostic method is mainly used in cm grades of short air gap ns pulsed discharge plasma parameter diagnosis at present.
2, Mach once moral M-Z laser interferance method.
Deposit problem both ways：
(1) width of the sensitivity of M-Z interferometry and striped is positively correlated, and within the time of dark space, gas density variable quantity is very
Small, so as to cause the variable quantity very little of refractive index, the displacement of interference fringe to be increased needs to increase fringe spacing, reduces item
Line quantity, but this reduces the spatial resolution of interferometry again.Since there are sensitivity and spatial resolution for M-Z interferometry
Contradiction, so that it is unable to satisfy measurement of the streamer to guide's conversion process channel density.
(2) guide's conversion process duration is short due to streamer-, at the time of occur there are randomness, using being impacted in Fig. 2
Triggering benchmark of the voltage signal as high-speed camera, it is difficult to effectively capture record streamer-guide's conversion process interference image, nothing
Method realizes the accurate measurement of its density.
3, quantitative schlieren method.
The not set edge of a knife of traditional schlieren method can only obtain the qualitative distribution of leader channel density.Quantitative schlieren method
There are two aspects：
(1) there are contradictions with image quality for the promotion of quantitative schlieren method spatial and temporal resolution, and image intensity is made to be difficult to accurately remember
Record, density measure error increase.This is because schlieren system generallys use invariable power LED light source in order to avoid diffraction phenomena.When
When promoting its spatial resolution, need to will lead to the reduction of Fig. 3 high speed photographic apparatus light-inletting quantity using long focal length lens, be intended to simultaneously
Temporal resolution is promoted, high-speed camera light-inletting quantity will further decrease, and cause image contrast decline, picture noise to increase,
Seriously affect inversion of Density computational accuracy.
(2) it equally exists in quantitative schlieren system and is triggered using surge voltage signal as triggering benchmark, it is difficult to be captured
The problem of recording streamer-guide's conversion process schlieren image.
In conclusion existing long air gap discharge gas density measuring method deposits problem both ways：
1, the sensitivity of existing method and spatial and temporal resolution are not able to satisfy streamer guide's conversion process manoscopy
It is required that.There are contradictions with spatial resolution increase for M-Z interferometry sensitivity enhancement.There are temporal resolutions to mention for general measure schlieren
It is high and the problem of cause image quality to significantly reduce.
2, guide's conversion process duration is short due to streamer-, at the time of occur there are randomness, existing method is all made of
Surge voltage triggers benchmark as image, it is difficult to which the instantaneous picture of reliable record optical system can not achieve the standard of gas density
Really measurement.
Summary of the invention
Guide's conversion process duration is short for above-mentioned long air gap electric discharge streamer-, it is random to exist at the time of occur
Property, gas density changes the difficult problem of small, accurate measurement therebetween, and it is first that the purpose of the present invention is to provide a kind of long gap streamers
Lead electric discharge conversion instant gas density measurement system and method.The present invention is based on the optical paths of quantitative schlieren method, using high-power arteries and veins
It rushes drive current source driving LED chip and combines ultrahigh speed ICCD camera (enhancing charge-coupled device camera, also to pass through
The CCD camera that optical fiber is connected with the board-like image intensifier of electron tube or microchannel), realize the high comparison of instantaneous schlieren image
Degree, low noise acoustic imaging；Using ebb-flow discharge self-luminous transient signal, take a picture through the coupling of lens optical path and pulse shaping as ICCD
Machine triggers reference pulse, by accurately controlling trigger pulse time delay, realizes streamer-guide's conversion process any time schlieren image
Reliable record.It is accurate anti-that streamer-ns grades of pilot discharge conversion process instant gas density distributing law can be achieved in the present invention
Measurement is drilled, with the high advantage of system reliability and capture rate, space division when solving existing M-Z interference and schlieren imaging method
Resolution is low, be difficult to adapt to streamer-pilot discharge conversion random process manoscopy the problem of.
The purpose of the present invention is what is be achieved through the following technical solutions：
A kind of long gap streamer pilot discharge conversion instant gas density measurement system, including set gradually along optical path direction
LED chip, extender lens, main lens, plus lens, the edge of a knife, telephoto lens and ICCD camera；Wherein, the LED chip
It is driven by pulsed drive current source and generates light pulse；
The top in region is equipped with high-field electrode between the main lens and plus lens, and saturating in the main lens and convergence
Region of discharge is generated between mirror, the bottom in region is equipped with coupled lens between the main lens and plus lens；
The coupled lens are used to detect the spontaneous optical signal of high-field electrode end electric discharge, and the self-luminous that electric discharge is generated
Focusing passes into photomultiplier tube, and the photomultiplier tube converts voltage waveform simultaneously for electric discharge self-luminous light intensity time-domain signal
It inputs TTL pulse and forms circuit, the TTL pulse forms the input terminal of the output end connection digital delay generator of circuit, institute
The output end for stating digital delay generator is separately connected pulsed drive current source and ICCD camera.
Further, the focus of the focus with telephoto lens of the plus lens is overlapped in the knife-edge part.
Further, it is additionally provided with impulse voltage generator, the impulse voltage generator rushes standard thunder and lightning or operation
It hits voltage and is applied to the high-field electrode, to generate region of discharge.
Further, the TTL pulse forms circuit and turns first rising edge of the self-luminous light intensity time-domain signal that discharges
TTL voltage signal is turned to, and passes through digital delay generator, generates the independent TTL of two-way by setting different delay times
Trigger signal of the voltage signal as ICCD camera and pulsed drive current source.
Further, the TTL pulse forms circuit and turns first rising edge of the self-luminous light intensity time-domain signal that discharges
TTL voltage signal is turned to, and passes through digital delay generator, generates the independent TTL of two-way by setting different delay times
Trigger signal of the voltage signal as ICCD camera and pulsed drive current source.
Further,
The operating voltage in the pulsed drive current source is 10V~24V, and output square wave current peak value is 100A~200A,
Pulse current pulsewidth is 0.5 μ of μ s~5.0 s；
The LED chip is the green point light source of wavelength 532nm ± 10nm, and spot diameter is less than 4mm.
Further,
The main lens and plus lens focal length are within the scope of 1.5m~2.5m, and optic diameter is in 20cm~30cm model
In enclosing；
The edge of a knife minimum stroke is not more than 50 μm；
The telephoto lens focal length minimum value is not less than 500mm.
Further, the coupled lens focal length is 0.5m~1.0m；The photomultiplier tube response time is not more than
5ns。
A kind of long gap streamer pilot discharge conversion instant gas density measuring method, includes the following steps：
Step 1, when the voltage being applied on high-field electrode is more than ebb-flow discharge voltage t1When, there is branch in region of discharge
Streamer and adjoint self-luminous；
Step 2, discharge generation self-luminous by coupled lens focus enter photomultiplier tube；The photomultiplier tube will
The electric discharge self-luminous light intensity time-domain signal of input is converted into voltage waveform and is input to TTL pulse formation circuit；The pulse shaping
The corresponding time t of first rising edge for the electric discharge self-luminous light intensity time-domain signal that circuit will test2It is converted into TTL voltage letter
Trigger source signal number as whole system；
Step 3, TTL voltage signal obtained in step 2 is input to digital delay generator, the digital delay occurs
Device exports the independent TTL voltage signal of two-way by different delay times；Wherein TTL voltage signal passes through time delay Δ t all the way1
Output, it is T that trigger pulse drive current source, which works and generates pulsewidth,1Pulse current, driving LED chip work, generate transient state
High-intensitive green light；
Step 4, the high-intensitive green light successively passes through extender lens and main lens generates directional light, using region of discharge
Domain；Since ebb-flow discharge electric current heating air makes it be converted into guide, gas density is reduced in region of discharge, refractive index becomes
Change, directional light generates offset, and by plus lens and the edge of a knife, the line changed over time is generated at ICCD camera imaging plane
Shadow image；
Step 5, in addition TTL voltage signal passes through time delay Δ t all the way obtained in step 32Output is touched to ICCD camera
It sends out ICCD camera and opens the schlieren image of shutter record at this time；
Step 6, it lead to-is worn according to schlieren image combination gray scale checking curve, Abel Transform algorithm and the lattice Lars of acquisition
Your formula Inversion Calculation obtains the gas density regularity of distribution in region of discharge at this time.
Further, in step 5, cooperate the time for exposure of telephoto lens and ICCD camera that the imaging of schlieren image is adjusted
Range, the temporal resolution of each pixel corresponding spatial resolution and schlieren image.
The digital delay generator to the pulsed drive current source signal cable and the digital delay generator
The extremely signal cable equal length of the ICCD camera, and the signal cable length is less than 20m；Be delayed Δ t1Less than delay
Δt2。
Beneficial effects of the present invention are：
(1) using quantitative schlieren method optical path combination telephoto lens, it can be obviously improved the spatial resolution of schlieren imaging, overcome
The problem of M-Z interferometry causes spatial resolution to reduce because of sensitivity enhancement.
(2) replace high-speed camera as image recording structure using ultrahigh speed ICCD camera, by manoscopy
Temporal resolution be promoted to ns grades of time scales by s grades of μ of conventional method.
(3) it combines LED chip to constitute high intensity pulses light source using pulsed drive current source, solves traditional quantitative schlieren
Method uses invariable power LED light source, leads to image contrast decline, noise image because of light-inletting quantity deficiency in ns grades of time images
Noise increases, and the problem of seriously affect inversion of Density computational accuracy.
(4) trigger source signal to be worked using electric discharge self-luminous as system is realized by cooperation pulse digit delay
Streamer-pilot discharge conversion process reliable, efficient capture, solving conventional method can not as trigger source using surge voltage
The low problem of adaptive electric discharge randomness, capture rate.
(5) contactless detection is carried out to spontaneous optical signal using coupled lens, avoids measuring system to discharge process
Influence.
(6) by adjusting delay Δ t1With delay Δ t2, the two, which cooperates, can be achieved streamer guide conversion process any time ns
The measurement of grade instant gas density.Compared with traditional M-Z interferometry, system spatial and temporal resolution is high, the optical device used is few,
It is at low cost, control and adjust it is more flexible and convenient, can be realized large air gap discharge streamer to guide convert mm grade regions in, arbitrarily
The accurate measurement of streamer guide conversion gas ns grades of instantaneous density Two dimensional Distribution of dark space moment.
Detailed description of the invention
Fig. 1 is positive polarity large air gap discharge process schematic；
Fig. 2 is Mach once moral M-Z laser interferance method pilot system schematic diagram；Wherein, 21- laser source, 22- beam splitter, 23-
Reflecting mirror, 24- lens, 25- slit, 26- imaging screen, 27- high-speed camera instrument, 28- impulse voltage generator, 29- high-field electrode,
210- discharge channel, 211-TTL pulse shaping circuit；
Fig. 3 is quantitative schlieren trial system schematic；Wherein, 31- light source, 32- beam expanding lens, 33- lens, 34- convergence are saturating
Mirror, the 35- edge of a knife, 36- high-speed camera, 37- impulse voltage generator, 38- high-field electrode, 39- discharge channel, 310-TTL arteries and veins
Punching forms circuit；
Fig. 4 is that long gap streamer of the present invention-pilot discharge converts instant gas density measurement system structural schematic diagram；
Wherein, 1- pulsed drive current source, 2-LED chip, 3- extender lens, 41- main lens, 42- plus lens, the 5- edge of a knife, 6- long
Zoom lens, 7-ICCD camera, 8- high-field electrode, 9- region of discharge, 10- coupled lens, 11- photomultiplier tube, 12-TTL arteries and veins
Punching forms circuit, 13- digital delay generator, 14- impulse voltage generator.
Fig. 5 is the system trigger that long gap streamer of the present invention-pilot discharge converts instant gas density measuring method
Timing diagram.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right
The present invention is further elaborated.It should be appreciated that described herein, specific examples are only used to explain the present invention, not
For limiting the present invention.
A kind of long gap streamer pilot discharge conversion instant gas density measurement system, as shown in Figure 1, including along optical path side
To LED chip 2, extender lens 3, main lens 41, plus lens 42, the edge of a knife 5, telephoto lens 6 and the ICCD photograph set gradually
Machine 7；Wherein, the LED chip 2 is driven by pulsed drive current source 1 and generates light pulse.It is combined using pulsed drive current source
LED chip constitutes high intensity pulses light source, solves traditional quantitative schlieren method using invariable power LED light source, ns grades of times at
As when because light-inletting quantity deficiency due to cause image contrast decline, noise image noise increase, and seriously affect inversion of Density calculating
The problem of precision.Replace high-speed camera as image recording structure using ultrahigh speed ICCD camera, by manoscopy
Temporal resolution be promoted to ns grades of time scales by s grades of μ of conventional method.
The top in region is equipped with high-field electrode 8, the main lens 41 and remittance between the main lens 41 and plus lens 42
The bottom in region is equipped with coupled lens 10 between poly- lens 42.It is additionally provided with impulse voltage generator 14, the surge voltage occurs
Standard thunder and lightning or operating impulse voltage are applied to the high-field electrode 8 by device 14, in the main lens 41 and plus lens
Region of discharge 9 is generated between 42.
The coupled lens 10 be used for detect 8 end of high-field electrode electric discharge spontaneous optical signal, and by electric discharge generate from
Luminous focusing passes into photomultiplier tube 11.Contactless detection is carried out to spontaneous optical signal using coupled lens, is avoided
Influence of the measuring system to discharge process.Electric discharge self-luminous light intensity time-domain signal is converted voltage wave by the photomultiplier tube 11
Shape simultaneously inputs TTL pulse formation circuit 12.The TTL pulse forms the output end connection digital delay generator 13 of circuit 12
The output end of input terminal, the digital delay generator 13 is separately connected pulsed drive current source 1 and ICCD camera 7.Specifically
, the TTL pulse forms circuit 12 and converts TTL voltage letter for first rising edge of the self-luminous light intensity time-domain signal that discharges
Number, and pass through digital delay generator 13, the independent TTL voltage signal conduct of two-way is generated by setting different delay times
The trigger signal of ICCD camera 7 and pulsed drive current source 1.
Wherein, the focus with the focus of telephoto lens 6 of the plus lens 42 are overlapped at the edge of a knife 5.
A kind of long gap streamer pilot discharge conversion instant gas density measuring method, includes the following steps：
Step 1, when the voltage being applied on high-field electrode 8 is more than ebb-flow discharge voltage t1When, divide in region of discharge 9
Branch streamer and adjoint self-luminous.
Step 2, discharge generation self-luminous by coupled lens 10 focus enter photomultiplier tube 11；The photomultiplier transit
Pipe 11 converts voltage waveform for the electric discharge self-luminous light intensity time-domain signal of input and is input to TTL pulse formation circuit 12；It is described
The corresponding time t of first rising edge for the electric discharge self-luminous light intensity time-domain signal that pulse shaping circuit 12 will test2Conversion
Trigger source signal for TTL voltage signal as whole system.
Step 3, TTL voltage signal obtained in step 2 is input to digital delay generator 13, the digital delay hair
Raw device 13 exports the independent TTL voltage signal of two-way by different delay times；Wherein TTL voltage signal passes through time delay all the way
Δt1Output, it is T that trigger pulse drive current source 1, which works and generates pulsewidth,1Pulse current, driving LED chip work, generate
Transient state high intensity green light.
Step 4, the high-intensitive green light successively passes through extender lens 3 and main lens 41 generates directional light, using electric discharge
Region 9；It is set to be converted into guide since ebb-flow discharge electric current is heating air, gas density is reduced, reflected in region of discharge 9
Rate changes, and directional light generates offset, by plus lens 42 and the edge of a knife 5, generated at 7 imaging plane of ICCD camera with
The schlieren image of time change.
Step 5, in addition TTL voltage signal passes through time delay Δ t all the way obtained in step 32It exports to ICCD camera 7,
It triggers ICCD camera 7 and opens the schlieren image of shutter record at this time；When cooperating the exposure of telephoto lens 6 and ICCD camera 7
Between be adjusted schlieren image imaging range, the temporal resolution of each pixel corresponding spatial resolution and schlieren image.It adopts
With quantitative schlieren method optical path combination telephoto lens, it can be obviously improved the spatial resolution of schlieren imaging, overcome M-Z interferometry because of spirit
The problem of sensitivity is promoted and spatial resolution is caused to reduce.
Step 6, it lead to-is worn according to schlieren image combination gray scale checking curve, Abel Transform algorithm and the lattice Lars of acquisition
Your formula Inversion Calculation obtains the gas density regularity of distribution in region of discharge 9 at this time.Detailed description is not added in the step category universal method.
The shape and interstitial structure of high-field electrode 8 can be set according to research.It is applied to rushing on high-field electrode 8
It is as needed to hit voltage waveform, either standard lightning impulse voltage, can also be standard switching impulse voltage.It applies alive
Peak value UpIt must be over the starting voltage of ebb-flow discharge, value can consult high-voltage test techniques engineering manual.
1 operating voltage of pulsed drive current source is preferably set as 10V~24V range, and by MOSFET, (metal-oxide is partly led
Body field effect transistor) driving, it exports square wave current peak value and preferably controls in 100A~200A range, pulse current pulsewidth preferably controls
In the 0.5 μ s range of μ s~5.0.LED chip 2 preferably uses CBT-120Green LED, and wavelength is the green light of 532nm ± 10nm
Source.To guarantee measurement sensitivity, point light source should be, spot diameter should be less than 4mm.
In order to guarantee sensitivity and insulation distance, main lens 41 and 42 focal length of plus lens are preferably controlled in 1.5m~2.5m
Range, optic diameter are 20cm~30cm range, and eyeglass double-sided coating is anti-reflection.
In order to guarantee to obtain the accuracy of schlieren image grayscale, 5 minimum stroke of the edge of a knife should not exceed 50 μm.
In order to guarantee the spatial resolution of schlieren image, 6 focal length minimum value of telephoto lens is no less than 500mm, so that line
The corresponding maximum space distance of shadow imaging single pixel should be less than 100 μm.
10 focal length of coupled lens is preferably set as 0.5m~1.0m range.11 response time of photomultiplier tube is not more than 5ns, light
Spectral limit covers Uv and visible light.Pulse shaping circuit 12 can use comparator, when input optical intensity voltage signal first time
When more than threshold value, rising edge TTL is exported, converts time delay Δ ts50ns should be not more than.Digital delay generator 13 can be used
DG535 is, it can be achieved that the accuracy controlling that multichannel TTL pulse postpones, maximum delay control value are no less than 100 μ s.
The signal cable length in digital delay generator 13 to pulsed drive current source 1 and ICCD camera 7 answer it is equal, with
Guarantee trigger pulse propagation delay time Δ t3It is equal, and signal cable length should be less than 20m, taking propagation of electrical signals speed is 2/3 times
The light velocity, propagation delay time Δ t3Maximum value should be less than 100ns.
Be delayed Δ t1It should be less than delay Δ t2, that is, must assure that trigger pulse drive current source makes LED chip work first
Make, then triggers ICCD camera record schlieren image.In view of to receive start pulse signal fast to opening for ICCD camera
The time delay of door is Δ t4If generating the moment with surge voltage as 0 moment, schlieren image that physical record arrives, inverting are obtained
The corresponding absolute time t of gas densityiFor：ti=t1+Δts+Δt2+Δt3+Δt4, wherein t1The moment is generated for ebb-flow discharge,
As shown in Figure 5.Fig. 5 is the system touching that long gap streamer of the present invention-pilot discharge converts instant gas density measuring method
Timing diagram is sent out, reaches streamer starting voltage, ebb-flow discharge starting when applying voltage, and then photomultiplier tube detects optical signal,
And circuit is formed respectively to pulsed drive current source and ICCD Camiera input TTL triggering level from TTL pulse, when system correlation
Prolong as shown in the figure.Wherein, the time for exposure of ICCD camera can be set to 10ns~100ns range.
Obtaining tiOn the basis of moment schlieren image, the distribution for calculating optical fiber deviation angle value according to gray value of image is bent
Line, and then the index distribution based on Abel inverse transformation calculating gas finally lead to-Dell's formula calculating acquisition according to lattice Lars
tiThe instant gas density of 10ns~100ns region of discharge after moment.
The transient measurement side that dark space time gas density is converted to streamer guide in large air gap discharge that the application is proposed
One of method key point is using the spontaneous optical signal of ebb-flow discharge as trigger source.Since discharge current waveform and light intensity waveform are in line
Sexual intercourse, similarly can also be using discharge current waveform as trigger source.Therefore, using discharge current and based on various flow fields
Display technology (schlieren method, shadowing method, interferometry etc.), is able to achieve partial function of the invention, therefore be considered the application
Alternative solution.
The foregoing is only a preferred embodiment of the present invention, is not intended to restrict the invention, for the skill of this field
For art personnel, the invention may be variously modified and varied.All within the spirits and principles of the present invention, made any to repair
Change, equivalent replacement, improvement etc., should all be included in the protection scope of the present invention.
Claims (10)
1. a kind of long gap streamer pilot discharge converts instant gas density measurement system, which is characterized in that including along optical path side
To LED chip (2), extender lens (3), main lens (41), plus lens (42), the edge of a knife (5), telephoto lens set gradually
(6) and ICCD camera (7)；Wherein, the LED chip (2) is driven by pulsed drive current source (1) and generates light pulse；
The top in region is equipped with high-field electrode (8) between the main lens (41) and plus lens (42), and in the main lens
(41) region of discharge (9) are generated between plus lens (42), region between the main lens (41) and plus lens (42)
Bottom is equipped with coupled lens (10)；
The coupled lens (10) be used for detect high-field electrode (8) end electric discharge spontaneous optical signal, and by electric discharge generate from
Luminous focusing passes into photomultiplier tube (11), and the photomultiplier tube (11) will electric discharge self-luminous light intensity time-domain signal conversion
For voltage waveform and TTL pulse formation circuit (12) is inputted, the output end connection number that the TTL pulse forms circuit (12) is prolonged
The input terminal of slow generator (13), the output end of the digital delay generator (13) are separately connected pulsed drive current source (1)
With ICCD camera (7).
2. long gap streamer pilot discharge according to claim 1 converts instant gas density measurement system, feature exists
In the focus of the plus lens (42) is overlapped at the edge of a knife (5) with the focus of telephoto lens (6).
3. long gap streamer pilot discharge according to claim 1 converts instant gas density measurement system, feature exists
In being additionally provided with impulse voltage generator (14), the impulse voltage generator (14) is by standard thunder and lightning or operating impulse voltage
The high-field electrode (8) are applied to, to generate region of discharge (9).
4. long gap streamer pilot discharge according to claim 1 converts instant gas density measurement system, feature exists
In the TTL pulse forms circuit (12) and converts TTL voltage for first rising edge of the self-luminous light intensity time-domain signal that discharges
Signal, and pass through digital delay generator (13), the independent TTL voltage signal of two-way is generated by setting different delay times
Trigger signal as ICCD camera (7) and pulsed drive current source (1).
5. long gap streamer pilot discharge according to claim 1 converts instant gas density measurement system, feature exists
In,
The operating voltage of the pulsed drive current source (1) is 10V~24V, and output square wave current peak value is 100A~200A, arteries and veins
Rushing electric current pulsewidth is 0.5 μ of μ s~5.0 s；
The LED chip (2) is the green point light source of wavelength 532nm ± 10nm, and spot diameter is less than 4mm.
6. long gap streamer pilot discharge according to claim 1 converts instant gas density measurement system, feature exists
In, the main lens (41) and plus lens (42) focal length within the scope of 1.5m~2.5m, optic diameter 20cm~
Within the scope of 30cm；
The edge of a knife (5) minimum stroke is not more than 50 μm；
Telephoto lens (6) the focal length minimum value is not less than 500mm.
7. long gap streamer pilot discharge according to claim 1 converts instant gas density measurement system, feature exists
In coupled lens (10) focal length is 0.5m~1.0m；Photomultiplier tube (11) response time is not more than 5ns.
8. a kind of long gap streamer pilot discharge converts instant gas density measuring method, which is characterized in that include the following steps：
Step 1, when the voltage being applied on high-field electrode (8) is more than ebb-flow discharge voltage t1When, region of discharge (9) is middle to be divided
Branch streamer and adjoint self-luminous；
Step 2, discharge generation self-luminous by coupled lens (10) focus enter photomultiplier tube (11)；The photomultiplier transit
Pipe (11) converts voltage waveform for the electric discharge self-luminous light intensity time-domain signal of input and is input to TTL pulse formation circuit (12)；
The first rising edge corresponding time for the electric discharge self-luminous light intensity time-domain signal that the pulse shaping circuit (12) will test
t2It is converted into trigger source signal of the TTL voltage signal as whole system；
Step 3, TTL voltage signal obtained in step 2 is input to digital delay generator (13), the digital delay occurs
Device (13) exports the independent TTL voltage signal of two-way by different delay times；Wherein TTL voltage signal passes through time delay all the way
Δt1Output, it is T that trigger pulse drive current source (1), which works and generates pulsewidth,1Pulse current, driving LED chip work, produce
Raw transient state high intensity green light；
Step 4, the high-intensitive green light successively passes through extender lens (3) and main lens (41) generates directional light, using electric discharge
Region (9)；Since ebb-flow discharge electric current heating air makes it be converted into guide, the interior gas density of region of discharge (9) is reduced, is reflected
Rate changes, and directional light generates offset, by plus lens (42) and the edge of a knife (5), at ICCD camera (7) imaging plane
Generate the schlieren image changed over time；
Step 5, in addition TTL voltage signal passes through time delay Δ t all the way obtained in step 32Output is triggered to ICCD camera (7)
ICCD camera (7) opens the schlieren image of shutter record at this time；
Step 6 ,-Dell's public affairs are led to according to the schlieren image combination gray scale checking curve of acquisition, Abel Transform algorithm and lattice Lars
Formula Inversion Calculation obtains the gas density regularity of distribution in region of discharge (9) at this time.
9. long gap streamer pilot discharge according to claim 8 converts instant gas density measuring method, feature exists
In, in step 5, the range of the time for exposure of cooperation telephoto lens (6) and ICCD camera (7) adjustable schlieren image imaging,
The temporal resolution of each pixel corresponding spatial resolution and schlieren image.
10. long gap streamer pilot discharge according to claim 8 converts instant gas density measuring method, feature exists
In,
The digital delay generator (13) to the signal cable of the pulsed drive current source (1) and the digital delay occurs
The signal cable equal length of device (13) the extremely ICCD camera (7), and the signal cable length is less than 20m；
Be delayed Δ t1Less than delay Δ t2。
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| CN113203923A (en) * | 2021-04-23 | 2021-08-03 | 华中科技大学 | Equivalent observation method for positive long air gap discharge streamer characteristics |
| CN113329553A (en) * | 2021-06-11 | 2021-08-31 | 北京环境特性研究所 | Detection method and detection device for plasma density distribution |
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