CN103575695B - A kind of the GN 2 oxide content pick-up unit - Google Patents

Abstract

The invention discloses a kind of the GN 2 oxide content pick-up unit, for detecting the concentration of institute's nitrogen-containing oxide in gas, described pick-up unit comprises: processor, programmable current source, laser instrument, gas absorption cell, detector and signal conditioner.Application the present invention, do not need pyrolytic conversion process, because this reducing power consumption and energy consumption, and owing to being the content of oxides of nitrogen in direct measurement gas, the impact that the existence avoiding other materials detects gas content to be measured, makes check result more accurate.Further, owing to not needing to use ZrO ₂, therefore, also there is not P in sensor, the compound of S, Si, such as H ₂s, can cause ZrO ₂the problem of Sensor Poisoning.Meanwhile, due to ZrO ₂the technology that sensor technology is monopolized by offshore company, and the application does not need to use ZrO ₂sensor, has therefore broken prior art barrier.

Description

A kind of the GN 2 oxide content pick-up unit

Technical field

The present invention relates to gas content detection technique field, particularly a kind of the GN 2 oxide content pick-up unit.

Background technology

The high speed development of China's automobile industry, demand is by breakthrough 1,000 ten thousand.Go on a journey facilitating the people, pull GDP to increase etc. in achieve remarkable result while, result also in serious environmental issue.Automotive emission has become the important source of atmospheric pollution, has a strong impact on the sustainable development generation of body health of people and national society.Therefore, countries in the world constantly propose more and more higher requirement to motor-driven vehicle gas disposal.China has enforced state 3 (Europe 3) standard, estimates that on July 1st, 2012 will enforce state IV (Europe IV) standard, this means solar obligation oxides of nitrogen (NOx) pick-up unit with control discharge content.

At present, common way uses zirconia (ZrO ₂) lambda sensor made carries out oxides of nitrogen detection, its Cleaning Principle is specially:, then by catalytic reaction, nitrogen oxide NOx is converted into N in the first air chamber by oxygen pump to 1ppb once ₂and O ₂, N after transforming ₂and O ₂enter the second air chamber, in the second air chamber, pass through ZrO again ₂lambda sensor measures the oxygen content generated, thus the content of indirect inspection nitrogen oxide NOx.

Although said method can record the content of oxides of nitrogen, at least there is following problem:

1, by catalytic reaction, NO is being converted into O ₂process in need the temperature making conversion environment to reach the high temperature of 300 degrees Celsius, power consumption is high, and energy consumption is large;

2, because the temperature of conversion environment needs the high temperature reaching 300 degrees Celsius, inflammable gas is thus subject to as H ₂, CH ₄, the impact of CO equal size, make testing result be subject to the impact of inflammable gas content very large, the accuracy of testing result is low;

3, the compound of P, S, Si, such as H ₂s, can cause ZrO ₂sensor Poisoning, causes ZrO ₂sensor failure.

Summary of the invention

The embodiment of the present invention provides a kind of the GN 2 oxide content pick-up unit, both can make testing result by the impact of inflammable gas content, avoid sensor because of some compound poisoning, also reduce power consumption.

The invention discloses a kind of the GN 2 oxide content pick-up unit, for detecting the concentration of institute's nitrogen-containing oxide in gas, described pick-up unit comprises: processor (100), programmable current source (200), laser instrument (300), gas absorption cell (400), detector (500) and signal conditioner (600), wherein, described gas absorption cell (400) has broken line type air chamber, described broken line type air chamber have air admission hole (415) and venthole (416), gas to be measured enters described broken line type air chamber from described air admission hole (415), flow along broken line type air chamber, described broken line type air chamber is flowed out from venthole (416), described broken line type air chamber also have incident light hole and light perforation hole, incident laser enters described broken line type air chamber from described incident light hole, along the reflection of broken line type air chamber, penetrates from light perforation hole,

Described programmable current source (200), directly adjusts laser instrument under the control of a processor, laser instrument (300) is exported laser that a road light intensity and wavelength are sinusoidal fluctuation; A described road laser enters the broken line type air chamber in gas absorption cell 400 by described incident light hole, from the injection of light perforation hole, enter detector;

Described detector (500), is converted to electric signal by a described road light signal, sends the electric signal after conversion to signal conditioning circuit;

Signal conditioning circuit (600), sends processor to after described electric signal conditioning;

Processor (100), according to the instruction received, detects second harmonic and base wave intensity in shoot laser, obtains the concentration of the oxides of nitrogen in gas to be measured according to described two kinds of humorous wave intensity from the signal after the conditioning received.

Wherein, described signal conditioning circuit comprises:

Wave filter, carries out filtering process by the electric signal from detector;

AD converter, sends processor to after described filtered analog electrical signal is converted to digital signal.

Wherein, described processor comprises:

Memory storage, when the concentration being kept at oxides of nitrogen gas in the gas comprising oxides of nitrogen is more than the first preset value, measures the difference DELTA D of the corresponding respectively laser current levels in the nox adsorption peak that obtains and reference absorption peak center; Be kept in the gas of nitrogenfree oxide gas current value D corresponding to the reference absorption peak center measuring and obtain ₂₀, and preserve current value D ₂₀the amplitude A of the first harmonic of the reference absorption peak at place ₀, and under equal conditions, current value is (D ₂₀-Δ D) the second harmonic value I at place _2f0;

Humorous intensity of wave acquisition device, first measures the current value D corresponding to reference absorption peak center in gas to be measured ₂, and measure current value D ₂the first harmonic amplitude A at place; Measuring laser current levels is again D ₁=D ₂the second harmonic value I of-Δ D position _{2f surveys}; The amplitude A of the first harmonic measuring the reference absorption peak obtained under the condition without gas to be measured is obtained from described memory storage ₀, and electric current is (D ₂₀-Δ D) the second harmonic value I at place _2f0, calculate background f (A)=I _2f0× A/A ₀, make laser diode current be D ₁nox adsorption peak second harmonic intensity I _2f=I _{2f surveys}-f (A);

Concentration calculation element, the intensity I of the second harmonic at current value place corresponding to described nox adsorption peak _2fwith reference absorption peak corresponding to the intensity A of first-harmonic at current value place obtain the concentration of the oxides of nitrogen in gas to be measured.

Wherein, described signal conditioning circuit comprises:

Wave filter, carries out filtering process by the electric signal from detector;

Lock-in amplify circuit, detects the intensity I of the second harmonic of shoot laser in described filtered signal _{2f surveys}.

Wherein, described processor comprises:

Memory storage, when the concentration being kept at oxides of nitrogen gas in the gas comprising oxides of nitrogen is more than the first preset value, measures the difference DELTA D of the corresponding respectively laser current levels in the nox adsorption peak that obtains and reference absorption peak center; Be kept in the gas of nitrogenfree oxide gas current value D corresponding to the reference absorption peak center measuring and obtain ₂₀, and preserve current value D ₂₀the amplitude A of the first harmonic of the reference absorption peak at place ₀, and under equal conditions, current value is (D ₂₀-Δ D) the second harmonic value I at place _2f0;

Humorous intensity of wave acquisition device, first measures the current value D corresponding to reference absorption peak center in gas to be measured ₂, and measure current value D ₂the first harmonic amplitude A at place; The amplitude A of the first harmonic measuring the reference absorption peak obtained under the condition without gas to be measured is obtained from described memory storage ₀, and electric current is (D ₂₀-Δ D) the second harmonic value I at place _2f0, calculate background f (A)=I _2f0× A/A ₀, make laser diode current be D ₁nox adsorption peak second harmonic intensity I _2f=I _{2f surveys}-f (A);

Concentration calculation element, the intensity I of the second harmonic at current value place corresponding to described nox adsorption peak _2fwith reference absorption peak corresponding to the intensity A of first-harmonic at current value place obtain the concentration of the oxides of nitrogen in gas to be measured.

Wherein, described gas to be measured is vehicle exhaust; Described reference gas is aqueous vapor.

Wherein, described gas absorption cell (400) comprising: pond body (401), first plane mirror (402), second plane mirror (403) peaceful surface cover (404), described first plane mirror (402) and the second plane mirror (403) are close to body (401) pond body the first side wall, described pond (406) and pond body second sidewall (407) respectively, wherein, described pond body the first side wall (406) is vertical with pond body upper surface (405) with pond body second sidewall (407), and described pond body the first side wall (406) and pond body second sidewall (407) are parallel to each other, described pond body upper surface (405) is provided with broken line type raceway groove (410), the broken line type raceway groove that described plane cover plate (404) covers described pond body (401) forms broken line type air chamber, described broken line type air chamber is positioned between described first plane mirror (402) and described second plane mirror (403), above multiple smooth reflection hole (412) is had along the direction perpendicular to pond body the first side wall (406) and pond body second sidewall (407) in pond body the first side wall (406) and pond body second sidewall (407), light reflection hole (412) communicates with broken line type raceway groove (410),

Described pond body upper surface (405) offers air admission hole (415) and venthole (416), gas to be measured enters described broken line type air chamber from described air admission hole (415), along broken line type raceway groove (410) flowing, flow out described broken line type air chamber from venthole (416);

Described gas absorption cell (400) also has pond body the 3rd sidewall (408) and pond body the 4th sidewall (409), wherein, described pond body the 3rd sidewall (408) becomes to preset the angle of the number of degrees with pond body second sidewall (407) respectively with pond body the 4th sidewall (409); Direction on the upper edge of pond body the 3rd sidewall (408) perpendicular to pond body the 3rd sidewall has incident light hole (411), and described incident light hole (411) communicates with broken line type raceway groove (410); Direction on the upper edge of pond body the 4th sidewall (409) perpendicular to pond body the 4th sidewall (409) has light perforation hole (413), and described smooth perforation hole (413) communicates with broken line type raceway groove (410); Incident laser enters described broken line type air chamber from described incident light hole (411), along the reflection of broken line type air chamber, penetrates from light perforation hole (413).

Wherein, described pick-up unit also comprises: cooling line, be connected to gas purging to be measured outlet and described gas absorption cell broken line type air chamber air admission hole (415) between, so that cooled gas to be measured is sent in described gas absorption cell.

Wherein, described pick-up unit also comprises: filtrator and gas-liquid separator, between the air admission hole (415) being connected to the end of cooling line and the broken line type air chamber of described gas absorption cell, to filter impurity in gas to be measured and liquid.

The pick-up unit that the application embodiment of the present invention provides, use spectrum test method, do not need pyrolytic conversion process, because this reducing power consumption and energy consumption, and, owing to being the content of oxides of nitrogen in direct measurement gas, the impact that the existence avoiding other materials detects gas content to be measured, makes check result more accurate.Further, owing to not needing to use ZrO ₂, therefore, also there is not P in sensor, the compound of S, Si, such as H ₂s, can cause ZrO ₂the problem of Sensor Poisoning.Meanwhile, due to ZrO ₂the technology that sensor technology is monopolized by offshore company, and the application does not need to use ZrO ₂sensor, has therefore broken prior art barrier.

Have again, in the scheme of application, laser instrument is only needed to export a road detecting light beam, the concentration of the oxides of nitrogen in gas to be measured is carried out by the intensity of the second harmonic of final shoot laser, do not need standard air chamber, also do not need reference arm, the spectrum test method thus avoiding existing two-way balance can not be applied to the problem of industry spot, the industry spot application wanted of can in officely what is the need for.

Have again, gas absorption cell in application the embodiment of the present application, make the concentration of gas to be measured equiblibrium mass distribution in gas absorption cell, not only can extend effective light path in a less area of space, and the quick turnover of gas to be measured in gas absorption cell can be realized.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.

Fig. 1 is the structural drawing of the GN 2 oxide content pick-up unit according to an embodiment of the invention;

Fig. 2 is the structural representation of a kind of gas absorption cell according to the embodiment of the present invention, and wherein Fig. 2 A is front view, and Fig. 2 B is left view, and Fig. 2 C is vertical view;

Fig. 3 is pond body inner structure according to gas absorption cell embodiment illustrated in fig. 2 and light transmission path schematic diagram;

Fig. 4 is the embody rule example schematic according to the embodiment of the present invention.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

See Fig. 1, it is the structural drawing of the GN 2 oxide content pick-up unit according to an embodiment of the invention, in the present embodiment, this pick-up unit is used for detecting the concentration of institute's nitrogen-containing oxide in gas, it specifically comprises: processor 100, programmable current source 200, laser instrument 300, gas absorption cell 400, detector 500 and signal conditioner 600, wherein, gas absorption cell 400 has broken line type air chamber, described broken line type air chamber have air admission hole 415 and venthole 416, gas to be measured enters described broken line type air chamber from described air admission hole 415, flow along broken line type air chamber, described broken line type air chamber is flowed out from venthole 416, described broken line type air chamber also have incident light hole and light perforation hole, incident laser enters described broken line type air chamber from described incident light hole, along the reflection of broken line type air chamber, penetrates from light perforation hole,

Programmable current source 200, directly adjusts laser instrument under the control of processor 100, laser instrument is exported laser that a road light intensity and wavelength are sinusoidal fluctuation; A described road laser enters the broken line type air chamber in gas absorption cell 400 by described incident light hole, from the injection of light perforation hole, enter detector;

Detector 500, is converted to electric signal by a described road light signal, sends the electric signal after conversion to signal conditioning circuit;

Signal conditioning circuit 600, sends processor to after described electric signal conditioning;

Processor 100, according to the instruction received, detects second harmonic and base wave intensity in shoot laser, obtains the concentration of the oxides of nitrogen in gas to be measured according to described two kinds of humorous wave intensity from the signal after the conditioning received.

In a kind of possible embodiment, above-mentioned signal conditioning circuit 600 can comprise:

Wave filter (not shown), carries out filtering process by the electric signal from detector; And

Modulus (AD) converter (not shown), sends processor to after described filtered analog electrical signal is converted to digital signal.

Now, described processor 100, according to the instruction received, detects the second harmonic in shoot laser and base wave intensity, obtains the concentration of oxides of nitrogen in gas to be measured according to described second harmonic and base wave intensity.In this embodiment, second harmonic and the base wave intensity of shoot laser are detected by processor.

Concrete, described processor 100 can comprise:

Memory storage, the concentration being kept at oxides of nitrogen gas in the gas comprising oxides of nitrogen more than the first preset value as 10% time, measure the difference DELTA D of the corresponding respectively laser current levels in the nox adsorption peak that obtains and reference absorption peak center; Be kept in the gas of nitrogenfree oxide gas current value D corresponding to the reference absorption peak center measuring and obtain ₂₀, and preserve current value D ₂₀the amplitude A of the first harmonic of the reference absorption peak at place ₀, and under equal conditions, current value is (D ₂₀-Δ D) the second harmonic value I at place _2f0;

Humorous intensity of wave acquisition device, first measures the current value D corresponding to reference absorption peak center in gas to be measured ₂, and measure current value D ₂the first harmonic amplitude A at place; Measuring laser current levels is again D ₁=D ₂the second harmonic value I of-Δ D position _{2f surveys}; The amplitude A of the first harmonic measuring the reference absorption peak obtained under the condition without gas to be measured is obtained from described memory storage ₀, and electric current is (D ₂₀-Δ D) the second harmonic value I at place _2f0, calculate background f (A)=I _2f0× A/A ₀, make laser diode current be D ₁nox adsorption peak second harmonic intensity I _2f=I _{2f surveys}-f (A);

Concentration calculation element, the intensity I of the second harmonic at current value place corresponding to nox adsorption peak _2fwith reference absorption peak corresponding to the intensity A of first-harmonic at current value place obtain the concentration of the oxides of nitrogen in gas to be measured.

Here, a simple declaration is done to the above-mentioned concept related to.

Background, due to P-I curve non-linear of laser instrument, and the other system existed is non-linear, even if when not having gas to be measured, the second harmonic value measuring the gas to be measured obtained can not be also 0, and this non-zero value is called background;

Oxides of nitrogen gas, it has been generally acknowledged that it is weak absorbing gas, and namely the absorption peak of oxides of nitrogen gas is substantially suitable with background owing to absorbing the second harmonic intensity level caused.

Reference absorption peak: if the absorption peak of certain gas is owing to absorbing the second harmonic intensity level that causes much larger than background, then this absorption peak is called as strong absorption peak, this strong absorption peak is usually used as reference absorption peak, and this gas corresponding to reference absorption peak is called reference gas.Such as, the background values that the second harmonic intensity level that certain absorption peak causes due to absorption is greater than 10 times, then this absorption peak can as reference absorption peak; Here, if the product value of absorption intensity and concentration is comparatively large, but this gas dense under a kind of possible situation lower environment to be measured that is absorption intensity, but another kind of possible situation is that the lower absorption intensity of concentration is high.

Usually, nox adsorption peak and reference absorb peak-to-peak distance range, are the scopes that current-modulation can reach, generally in several nanometer at zero point, but again can not be too close, influence each other in order to avoid absorption cross section overlaps.

Wherein, the principle that concentration calculates is same as the prior art, only does simple declaration here.

First, when light is by after certain gas, it will be subject to the absorption of gas, and its output intensity is determined by Bill-Lambert (Beer-Lambert) formula

I(υ)＝I ₀(υ)exp[-α(υ)CL](4.1)

Wherein, I (υ) is emergent light light intensity, and υ is the frequency of this light; I ₀be by air chamber before initial beam intensity; C is the concentration of gas; L for passed through air chamber long; α is the absorption coefficient of gas, and the absorption frequency that gas with various is corresponding is also different; For same gas, also there is a plurality of absorption peak.

Utilize this character, select the wavelength of incident laser, make it the center of certain absorption peak being in gas to be measured.Then allow this laser by gas to be measured.By detecting the intensity of emergent light, its absorption intensity by gas can be obtained, thus indirectly obtain the concentration of gas to be measured.Concrete,

A low frequency (k hertz rank) small signal modulation is added to the drive current of light source, laser instrument is directly adjusted, thus a modulation is produced to laser output wavelength, simultaneously an additional intensity modulation

$\begin{array}{c}\mathrm{\υ}=\stackrel{\‾}{\mathrm{\υ}}+a\sin \mathrm{\ω}t\\ I_0\left(t\right)=I_0(1+\mathrm{\η}\sin \mathrm{\ω}t)\end{array}---\left(4.2\right)$

Wherein, υ is the wavelength of light, I ₀the t time dependent light intensity value of light intensity that () laser instrument exports, ω is the angular frequency of added modulation, for the centre frequency of laser, a is frequency modulation (PFM) amplitude, and η is the intensity modulation degree of depth because frequency modulation (PFM) causes, and t is time parameter.

Because now gas concentration is very low, so there is-α (υ) CL<<1

So (4.1) formula can be rewritten as:

I(υ)＝I ₀(υ)e ^-α(υ)CL≈I ₀(υ)[1-α(υ)CL](4.3)

The absorption peak of general gas flow is Lorentz line shape, namely

$\mathrm{\&alpha;}\left(\mathrm{\&upsi;}\right)=\frac{{\mathrm{\&alpha;}}_0}{1+{\left(\frac{\mathrm{\&upsi;}-{\mathrm{\&upsi;}}_0}{\mathrm{\&Delta;}\mathrm{\&upsi;}}\right)}^2}---\left(4.4\right)$

υ in formula ₀for the center of absorption peak, α ₀for υ ₀the absorption coefficient at place; Δ ν is the halfwidth of absorption peak.

By (4.2), (4.4) are brought into (4.3), then the output intensity (namely arriving the light intensity of detector) after absorbing is

$I\left(t\right)=I_0(1+\mathrm{\&eta;}sin\mathrm{\&omega;}t)\&lsqb;1-\frac{{\mathrm{\&alpha;}}_{0}CL}{1+{\left(\frac{\stackrel{\&OverBar;}{\mathrm{\&upsi;}}-{\mathrm{\&upsi;}}_{0}a\sin \mathrm{\&omega;}t}{\mathrm{\&Delta;}\mathrm{\&upsi;}}\right)}^2}\&rsqb;---\left(4.5\right)$

The drive current of adjustment laser instrument makes the center of output light wavelength overlap with the center at gas absorption peak, namely then have

$\begin{array}{c}I\left(t\right)=I_0(1+\mathrm{\&eta;}\sin \mathrm{\&omega;}t)(1-\frac{{\mathrm{\&alpha;}}_{0}CL}{1+m^2{\sin }^2\mathrm{\&omega;}t})\\ =I\left(t\right)=I_0+I_0\mathrm{\&eta;}\sin \mathrm{\&omega;}t-\frac{I_0{\mathrm{\&alpha;}}_{0}CL}{1+m^2{\sin }^2\mathrm{\&omega;}t}-\frac{{\mathrm{\&alpha;}}_0\mathrm{\&eta;}\sin \mathrm{\&omega;}tCL}{1+m^2{\sin }^2\mathrm{\&omega;}t}\end{array}---\left(4.6\right)$

In formula, $m=\frac{a}{\mathrm{\&Delta;}\mathrm{\&nu;}}.$

Owing to being small signal modulation, η <<1, therefore can ignore second order in a small amount obtain:

$I\left(t\right)=I_0+I_0\mathrm{\&eta;}sin\mathrm{\&omega;}t-\frac{I_0{\mathrm{\&alpha;}}_{0}CL}{1+m^2{\sin }^2\mathrm{\&omega;}t}---\left(4.7\right)$

According to ω, Fourier expansion is done to (4.7), the fundametal compoment I of wherein ω can be obtained _fwith second harmonic component I _2fintensity be respectively:

$\begin{array}{c}{I}_f=I_0\mathrm{\&eta;}\\ I_{2f}=-I_0\frac{2(2+m^2-2\sqrt{1+m^2})}{m^2\sqrt{1+m^2}}{\mathrm{\&alpha;}}_{0}CL\\ =-I_{0}k\left(m\right){\mathrm{\&alpha;}}_{0}CL\end{array}---\left(4.8\right)$

In formula, $k\left(m\right)=\frac{2(2+m^2-2\sqrt{1+m^2})}{m^2\sqrt{1+m^2}}.$

Visible, the intensity proportional of fundametal compoment is in the depth of modulation of light intensity and intensity modulated; And for second harmonic, k (m) only with relevant, can by changing warbled amplitude to regulate.Be definite value for m a system determined, k (m) is also just a definite value; Meanwhile, α ₀l is also definite value.Therefore the intensity proportional of second harmonic component is in light intensity and gas concentration, utilizes the intensity I of second harmonic _2fnamely gas concentration C can be obtained.

Utilize above-mentioned formula (4.8) although gas concentration C can be calculated theoretically, but, if only use the intensity of second harmonic to detect vapour concentration, to introduce unnecessary common-mode noise, this causes by reference to the decay caused due to reasons such as the dust scatterings in air during air chamber at laser.

In order to eliminate above-mentioned impact, can by second harmonic component I _2fwith fundametal compoment I _fcompare, obtain

$\frac{I_{2f}}{I_f}=-\frac{2(2+m^2-2\sqrt{1+m^2})}{{\mathrm{\&eta;m}}^2\sqrt{1+m^2}}{\mathrm{\&alpha;}}_{0}CL---\left(4.9\right)$

Second harmonic and first-harmonic are actually the different frequency component of same light beam, owing to only there is light beam, therefore in communication process, absorb the impact of the light intensity decreasing caused by dust scattering or other non-pneumatics identical.The ratio I of the two _2f/ I _fhave nothing to do with equivalent power.Thus eliminating the need common-mode noise, make the Concentration Testing of gas more accurate.

Therefore, measure I _fobject actual be eliminate the impact of equivalent power, eliminate common-mode noise, and the first harmonic amplitude A in abovementioned steps 203 be exactly reference absorption peak place first harmonic intensity I ' _f=I ₀η ', so first can calculate I _2fwith the ratio of A, wherein, I _2fthe second harmonic intensity at current value place corresponding to target absorption peak, the first harmonic width intensity at A current value place corresponding to reference absorption peak; Again according to described I _2fthe concentration of object gas in gas to be measured is obtained with the ratio of A.

Concrete, I _2fwith the ratio of A be

$\frac{I_{2f}}{A}=\frac{I_{2f}}{I_f^{\&prime;}}=-\frac{2(2+m^2-2\sqrt{1+m^2})}{{\mathrm{\&eta;}}^{\&prime;}{m}^2\sqrt{1+m^2}}{\mathrm{\&alpha;}}_{0}CL---\left(4.10\right)$

It is visible, be directly proportional to concentration equally.Wherein, I' _fthe first harmonic amplitude at the current value place corresponding to reference absorption peak, the intensity modulation degree of depth that the current value place of η ' corresponding to reference absorption peak causes due to frequency modulation (PFM).

Then, due to I _2f=I _{2f surveys}-f (A), so have

The concentration of gas to be measured can be calculated by above-mentioned formula (4.10) and formula (4.11).

In the embodiment that another kind is possible, described signal conditioning circuit 600 can comprise:

Wave filter, carries out filtering process by the electric signal from detector;

Lock-in amplify circuit, detects the intensity I of the second harmonic of shoot laser in described filtered signal _{2f surveys}.

Now, described processor, extracts intensity and the base wave intensity of described second harmonic, obtains the concentration of oxides of nitrogen in gas to be measured according to described second harmonic and base wave intensity from the signal after the modulation received.In this embodiment, second harmonic and the base wave intensity of shoot laser are gone out by lock-in amplify electric circuit inspection, and processor carries out concentration calculating.

In this case, processor comprises:

Memory storage, when the concentration being kept at oxides of nitrogen gas in the gas comprising oxides of nitrogen is more than the first preset value, measures the difference DELTA D of the corresponding respectively laser current levels in the nox adsorption peak that obtains and reference absorption peak center; Be kept in the gas of nitrogenfree oxide gas current value D corresponding to the reference absorption peak center measuring and obtain ₂₀, and preserve current value D ₂₀the amplitude A of the first harmonic of the reference absorption peak at place ₀, and under equal conditions, current value is (D ₂₀-Δ D) the second harmonic value I at place _2f0;

Humorous intensity of wave acquisition device, first measures the current value D corresponding to reference absorption peak center in gas to be measured ₂, and measure current value D ₂the first harmonic amplitude A at place; The amplitude A of the first harmonic measuring the reference absorption peak obtained under the condition without gas to be measured is obtained from described memory storage ₀, and electric current is (D ₂₀-Δ D) the second harmonic value I at place _2f0, calculate background f (A)=I _2f0× A/A ₀, make laser diode current be D ₁nox adsorption peak second harmonic intensity I _2f=I _{2f surveys}-f (A);

Concentration calculation element, the intensity I of the second harmonic at current value place corresponding to nox adsorption peak _2fwith reference absorption peak corresponding to the intensity A of first-harmonic at current value place obtain the concentration of the oxides of nitrogen in gas to be measured.

It should be noted that, aforementioned gas to be measured can be vehicle exhaust, also can be other gas of nitrogen-containing oxide, the waste gas etc. such as discharged from chimney; Aforementioned reference gas is aqueous vapor H ₂o also can be that other has the gas of strong receptivity, as carbon dioxide CO ₂deng.

The pick-up unit that the application embodiment of the present invention provides, use spectrum test method, do not need pyrolytic conversion process, because this reducing power consumption and energy consumption, and, owing to being the content of oxides of nitrogen in direct measurement gas, the impact that the existence avoiding other materials detects gas content to be measured, makes check result more accurate.Further, owing to not needing to use ZrO ₂, therefore, also there is not P in sensor, the compound of S, Si, such as H ₂s, can cause ZrO ₂the problem of Sensor Poisoning.Meanwhile, due to ZrO ₂the technology that sensor technology is monopolized by offshore company, and the application does not need to use ZrO ₂sensor, has therefore broken prior art barrier.

Further, be all use two-way balancing method, i.e. a road reference path in existing spectrum test method, a road detection light path, the equal position locking absorption peak of first harmonic two-way being recorded by adjustment direct current flow point.The program is feasible in laboratory, but in commercial Application, there is obvious problem.This is because reference arm is generally standard air chamber, the environment residing for it is different from branch road to be measured, and owing to cannot eliminate the dust scattering in air in the commercial Application of reality, the factors such as coupling imbalance, cannot provide satisfactory reference arm at all.Therefore, two-way balancing method can only be used for laboratory examination and can not be used in practical application.And in the scheme of the application, laser instrument is only needed to export a road detecting light beam, the concentration of the oxides of nitrogen in gas to be measured is carried out by the intensity of the second harmonic of final shoot laser, do not need standard air chamber, also reference arm is not needed, thus the spectrum test method avoiding existing two-way balance can not be applied to the problem of industry spot, the industry spot application wanted of can in officely what is the need for.

The gas concentration portion, ground caused due to gas turbulence and circulation in gas absorption cell in order to avoid gas to be measured is balanced, need the long period just can complete the problem that in air chamber, gaseous sample upgrades, the embodiment of the present application additionally provides a kind of gas absorption cell of special structure, make the concentration of gas to be measured equiblibrium mass distribution in gas absorption cell, not only can extend effective light path in a less area of space, and the quick turnover of gas to be measured in gas absorption cell can be realized.

Fig. 2 is the structural representation of a kind of gas absorption cell according to the embodiment of the present invention, and wherein Fig. 2 A is front view, and Fig. 2 B is left view, and Fig. 2 C is vertical view.Fig. 3 is pond body inner structure according to gas absorption cell embodiment illustrated in fig. 2 and light transmission path schematic diagram.

See Fig. 2 and Fig. 3, gas absorption cell shown in the present embodiment comprises: the peaceful surface cover 404 of pond body 401, first plane mirror 402, second plane mirror 403, described first plane mirror 402 and the second plane mirror 403 are close to body 401 pond, described pond body the first side wall 406 and pond body second sidewall 407 respectively, wherein, described pond body the first side wall 406 is vertical with pond body upper surface 405 with pond body second sidewall 407, and described pond body the first side wall 406 and pond body second sidewall 407 are parallel to each other; Described pond body upper surface 405 is provided with broken line type raceway groove 410, the broken line type raceway groove that described plane cover plate 404 covers described pond body 401 forms broken line type air chamber, described broken line type air chamber is between described first plane mirror 402 and described second plane mirror 403, pond body the first side wall 406 and pond body second sidewall 407 have multiple smooth reflection hole 412 along the direction perpendicular to pond body the first side wall 406 and pond body second sidewall 407, and light reflection hole 412 communicates with broken line type raceway groove 410;

Described pond body upper surface 405 offers air admission hole 415 and venthole 416, and gas to be measured enters described broken line type air chamber from described air admission hole 415, flows along broken line type raceway groove 410, flows out described broken line type air chamber from venthole 416;

Described gas absorption cell 400 also has pond body the 3rd sidewall 408 and pond body the 4th sidewall 409, wherein, described pond body the 3rd sidewall 408 and pond body the 4th sidewall 409 preset the angle of the number of degrees with pond body second sidewall 407 one-tenth respectively, such as, can be 3 ° ~ 10 °, can be preferably 4 °, 5 °, 6 ° or 7 °; Pond body the 3rd sidewall 408 has incident light hole 411 along the direction perpendicular to pond body the 3rd sidewall, and described incident light hole 411 communicates with broken line type raceway groove 410; Pond body the 4th sidewall 409 has light perforation hole 413 along the direction perpendicular to pond body the 4th sidewall 409, and described smooth perforation hole 413 communicates with broken line type raceway groove 410; Incident laser enters described broken line type air chamber from described incident light hole 411, along the reflection of broken line type air chamber, penetrates from light perforation hole 413.

It should be noted that, the angle α of broken line type raceway groove can adjust according to the length of the angle of incident laser and required light path, and the size of the application not considered critical angle α, it can decide according to practical application.

It should be noted that, the angle of pond body the 3rd sidewall 408 and the default number of degrees of pond body the 4th sidewall 409 respectively and between pond body second sidewall 407 is also determined according to practical application, such as installation site, the laser incident angle etc. of requirement, the application does not do strict restriction to this.

In a preferred embodiment, plane cover plate 404 is identical with size with pond body upper surface 405 shape, and by impressed pressure and flexible member, the cooperation lower seal as O type circle covers broken line type raceway groove 410, closes the broken line type air chamber forming gas absorption cell.Pond body the 3rd sidewall 408 and pond body the 4th sidewall 409 and pond body second sidewall 407 one-tenth 5 ° of angles, pond body the 3rd sidewall 408 is plane with pond body the 4th sidewall 409 and vertical with pond body upper surface 405.The broken line direction of broken line type raceway groove 410 is vertical with pond body the 4th sidewall 409 with pond body the 3rd sidewall 408 respectively.Pond body the 3rd sidewall 408 has incident light hole 411 along on the direction perpendicular to the 3rd sidewall 408, and incident light hole 411 communicates with broken line type raceway groove 410.Along having multiple smooth reflection hole 412 perpendicular to pond body the first side wall 406 and pond body second sidewall 407 direction on pond body the first side wall 406 and pond body second sidewall 407, the plurality of smooth reflection hole 412 communicates with broken line type raceway groove 410.Pond body the 4th sidewall 409 has a light perforation hole 413 along the direction perpendicular to pond body the 4th sidewall 409, and light perforation hole 413 communicates with broken line type raceway groove 410.Incident light hole 411 and light perforation hole 413 are closed by translucent element.

Gas absorption cell described in application drawing 2 and Fig. 3, is conducive to the detection real-time of continually varying gaseous sample, effectively improves the detection sensitivity to low concentration, consecutive variations gaseous sample; Further, above-mentioned air chamber structure simple, be easy to carry.

It should be noted that, can also comprise for pick-up unit described in Fig. 1: cooling line, this cooling line is connected between the air admission hole (415) of the broken line type air chamber of gas purging to be measured outlet and described gas absorption cell, to be sent in described gas absorption cell by cooled gas to be measured.High temperature gas to be measured can be avoided to enter gas absorption cell, with the serviceable life of extension detection device by cooling line.

It should be noted that, can also comprise for pick-up unit described in Fig. 1: filtrator and gas-liquid separator, between the air admission hole (415) being connected to the end of cooling line and the broken line type air chamber of described gas absorption cell, to filter impurity in gas to be measured and liquid.Impurity in gas to be measured and liquid are leached, namely can improve final accuracy of detection, the serviceable life of all right extension detection device.

It should be noted that, can also comprise for pick-up unit described in Fig. 1: display device, be connected with processor, for showing the concentration of the oxides of nitrogen in gas to be measured.The physical location of this display device can from processor very close to such as just on processor side, be convenient to field observation like this, can also distance processor comparatively far away such as at point of presence, be convenient to the operations such as subsequent statistical analysis like this.

See Fig. 4, it is the embody rule example schematic according to the embodiment of the present invention.In this example, tail gas to be measured is vehicle exhaust, and the vehicle exhaust of drawing from three-element catalytic tank 640 is introduced into cooling line 610, then enters sensor 630 by filtrator gas-liquid separator 620, thus detects the content of oxides of nitrogen in vehicle exhaust easily.Processor, programmable current source, laser instrument, gas absorption cell, detector and signal conditioner is included in sensor 630.

Pick-up unit shown in application drawing 4, does not need pyrolytic conversion process, because this reducing power consumption and energy consumption, and, owing to being the content of oxides of nitrogen in direct measurement gas, the impact that the existence avoiding other materials detects gas content to be measured, makes check result more accurate.Further, owing to not needing to use ZrO ₂, therefore, also there is not P in sensor, the compound of S, Si, such as H ₂s, can cause ZrO ₂the problem of Sensor Poisoning.Meanwhile, due to ZrO ₂the technology that sensor technology is monopolized by offshore company, and the present embodiment does not need to use ZrO ₂sensor, has therefore broken prior art barrier.

It should be noted that, in this article, term " comprises ", " comprising " or its any other variant are intended to contain comprising of nonexcludability, thus make to comprise the process of a series of key element, method, article or equipment and not only comprise those key elements, but also comprise other key elements clearly do not listed, or also comprise by the intrinsic key element of this process, method, article or equipment.When not more restrictions, the key element limited by statement " comprising ... ", and be not precluded within process, method, article or the equipment comprising described key element and also there is other identical element.

The foregoing is only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.All any amendments done within the spirit and principles in the present invention, equivalent replacement, improvement etc., be all included in protection scope of the present invention.

Claims (8)

1. the GN 2 oxide content pick-up unit, for detecting the concentration of institute's nitrogen-containing oxide in gas, it is characterized in that, described pick-up unit comprises: processor (100), programmable current source (200), laser instrument (300), gas absorption cell (400), detector (500) and signal conditioner (600), wherein, described gas absorption cell (400) has broken line type air chamber, described broken line type air chamber have air admission hole (415) and venthole (416), gas to be measured enters described broken line type air chamber from described air admission hole (415), flow along broken line type air chamber, described broken line type air chamber is flowed out from venthole (416), described broken line type air chamber also have incident light hole and light perforation hole, incident laser enters described broken line type air chamber from described incident light hole, along the reflection of broken line type air chamber, penetrates from light perforation hole,

Described programmable current source (200), directly adjusts laser instrument under the control of a processor, laser instrument (300) is exported laser that a road light intensity and wavelength are sinusoidal fluctuation; A described road laser enters the broken line type air chamber in gas absorption cell (400) by described incident light hole, from the injection of light perforation hole, enter detector;

Described detector (500), is converted to electric signal by a described road light signal, sends the electric signal after conversion to signal conditioning circuit;

Signal conditioning circuit (600), sends processor to after described electric signal conditioning;

Processor (100), according to the instruction received, detects second harmonic and base wave intensity in shoot laser, obtains the concentration of the oxides of nitrogen in gas to be measured according to described two kinds of humorous wave intensity from the signal after the conditioning received;

Described pick-up unit also comprises: cooling line, be connected to gas purging to be measured outlet and described gas absorption cell broken line type air chamber air admission hole (415) between, so that cooled gas to be measured is sent in described gas absorption cell.

2. pick-up unit according to claim 1, is characterized in that, described signal conditioning circuit comprises:

Wave filter, carries out filtering process by the electric signal from detector;

AD converter, sends processor to after described filtered analog electrical signal is converted to digital signal.

3. pick-up unit according to claim 2, is characterized in that, described processor comprises:

Memory storage, when the concentration being kept at oxides of nitrogen gas in the gas comprising oxides of nitrogen is more than the first preset value, measures the difference DELTA D of the corresponding respectively laser current levels in the nox adsorption peak that obtains and reference absorption peak center; Be kept in the gas of nitrogenfree oxide gas current value D corresponding to the reference absorption peak center measuring and obtain ₂₀, and preserve current value D ₂₀the amplitude A of the first harmonic of the reference absorption peak at place ₀, and under equal conditions, current value is (D ₂₀-Δ D) the second harmonic value I at place _2f0;

Humorous intensity of wave acquisition device, first measures the current value D corresponding to reference absorption peak center in gas to be measured ₂, and measure current value D ₂the first harmonic amplitude A at place; Measuring laser current levels is again D ₁=D ₂the second harmonic value I of-Δ D position _{2f surveys}; The amplitude A of the first harmonic measuring the reference absorption peak obtained under the condition without gas to be measured is obtained from described memory storage ₀, and electric current is (D ₂₀-Δ D) the second harmonic value I at place _2f0, calculate background f (A)=I _2f0× A/A ₀, make laser diode current be D ₁nox adsorption peak second harmonic intensity I _2f=I _{2f surveys}-f (A);

Concentration calculation element, the intensity I of the second harmonic at current value place corresponding to described nox adsorption peak _2fwith reference absorption peak corresponding to the intensity A of first-harmonic at current value place obtain the concentration of the oxides of nitrogen in gas to be measured.

4. pick-up unit according to claim 1, is characterized in that, described signal conditioning circuit comprises:

Wave filter, carries out filtering process by the electric signal from detector;

Lock-in amplify circuit, detects the intensity I of the second harmonic of shoot laser in described filtered signal _{2f surveys}.

5. pick-up unit according to claim 4, is characterized in that, described processor comprises:

Memory storage, when the concentration being kept at oxides of nitrogen gas in the gas comprising oxides of nitrogen is more than the first preset value, measures the difference DELTA D of the corresponding respectively laser current levels in the nox adsorption peak that obtains and reference absorption peak center; Be kept in the gas of nitrogenfree oxide gas current value D corresponding to the reference absorption peak center measuring and obtain ₂₀, and preserve current value D ₂₀the amplitude A of the first harmonic of the reference absorption peak at place ₀, and under equal conditions, current value is (D ₂₀-Δ D) the second harmonic value I at place _2f0;

Humorous intensity of wave acquisition device, first measures the current value D corresponding to reference absorption peak center in gas to be measured ₂, and measure current value D ₂the first harmonic amplitude A at place; The amplitude A of the first harmonic measuring the reference absorption peak obtained under the condition without gas to be measured is obtained from described memory storage ₀, and electric current is (D ₂₀-Δ D) the second harmonic value I at place _2f0, calculate background f (A)=I _2f0× A/A ₀, make laser diode current be D ₁nox adsorption peak second harmonic intensity I _2f=I _{2f surveys}-f (A);

Concentration calculation element, the intensity I of the second harmonic at current value place corresponding to described nox adsorption peak _2fwith reference absorption peak corresponding to the intensity A of first-harmonic at current value place obtain the concentration of the oxides of nitrogen in gas to be measured.

6. the pick-up unit according to claim 3 or 5, is characterized in that,

Described gas to be measured is vehicle exhaust;

Described reference gas is aqueous vapor.

7. pick-up unit according to claim 1, it is characterized in that, described gas absorption cell (400) comprising: pond body (401), first plane mirror (402), second plane mirror (403) peaceful surface cover (404), described first plane mirror (402) and the second plane mirror (403) are close to body (401) pond body the first side wall, described pond (406) and pond body second sidewall (407) respectively, wherein, described pond body the first side wall (406) is vertical with pond body upper surface (405) with pond body second sidewall (407), and described pond body the first side wall (406) and pond body second sidewall (407) are parallel to each other, described pond body upper surface (405) is provided with broken line type raceway groove (410), the broken line type raceway groove that described plane cover plate (404) covers described pond body (401) forms broken line type air chamber, described broken line type air chamber is positioned between described first plane mirror (402) and described second plane mirror (403), above multiple smooth reflection hole (412) is had along the direction perpendicular to pond body the first side wall (406) and pond body second sidewall (407) in pond body the first side wall (406) and pond body second sidewall (407), light reflection hole (412) communicates with broken line type raceway groove (410),

Described pond body upper surface (405) offers air admission hole (415) and venthole (416), gas to be measured enters described broken line type air chamber from described air admission hole (415), along broken line type raceway groove (410) flowing, flow out described broken line type air chamber from venthole (416);

Described gas absorption cell (400) also has pond body the 3rd sidewall (408) and pond body the 4th sidewall (409), wherein, described pond body the 3rd sidewall (408) becomes to preset the angle of the number of degrees with pond body second sidewall (407) respectively with pond body the 4th sidewall (409); Direction on the upper edge of pond body the 3rd sidewall (408) perpendicular to pond body the 3rd sidewall has incident light hole (411), and described incident light hole (411) communicates with broken line type raceway groove (410); Direction on the upper edge of pond body the 4th sidewall (409) perpendicular to pond body the 4th sidewall (409) has light perforation hole (413), and described smooth perforation hole (413) communicates with broken line type raceway groove (410); Incident laser enters described broken line type air chamber from described incident light hole (411), along the reflection of broken line type air chamber, penetrates from light perforation hole (413).

8. pick-up unit according to claim 1, it is characterized in that, described pick-up unit also comprises: filtrator and gas-liquid separator, between the air admission hole (415) being connected to the end of cooling line and the broken line type air chamber of described gas absorption cell, to filter impurity in gas to be measured and liquid.