CN102253234B - Method for measuring flame propagation speed of gas fuel laminar flow under Bunsen burner accurately - Google Patents

Method for measuring flame propagation speed of gas fuel laminar flow under Bunsen burner accurately Download PDF

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CN102253234B
CN102253234B CN 201110148721 CN201110148721A CN102253234B CN 102253234 B CN102253234 B CN 102253234B CN 201110148721 CN201110148721 CN 201110148721 CN 201110148721 A CN201110148721 A CN 201110148721A CN 102253234 B CN102253234 B CN 102253234B
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flame
bunsen
image
flame propagation
velocity
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CN102253234A (en
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孙锐
于欣
杨晓川
彭江波
刘辉
陈德应
孙军
伊亚超
王春红
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Harbin Institute of Technology
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Abstract

The invention relates to a method for measuring the flame propagation speed of a gas fuel laminar flow under a Bunsen burner accurately, and relates to a method for measuring the laminar flow flame propagation speed accurately. By the method, the calculation accuracy of a taper method calculation model of the conventional Bunsen burner method is improved. The method comprises the following steps of: acquiring a flow field image of a flame area above a pipe orifice by using a two-dimensional particle imaging speed meter, and processing an image to obtain an inner flow field speed diagram which is perpendicular to the axial cross section of the pipe orifice; acquiring the image of the flame of the Bunsen burner by using a charge coupled device (CCD) imaging instrument, performing luminance analysis on the image, extracting edges of the image, and performing curve fitting to obtain a flame frontal surface which is subjected fitting; performing position matching on the flow field speed diagram and a frontal surface curve, and calculating by an interpolation process to obtain the airflow speed Un of each point on a section with high linearity on the frontal surface curve; and calculating the flame propagation speed of each point according to a cosine law, and solving an average value to obtain the flame propagation speed of a local laminar flow of the Bunsen burner. The method is suitable for measuring the laminar flow flame propagation speed of the Bunsen burner accurately in the process of burning gas fuel.

Description

The accurate measurement method of flame propagation speed of gas fuel laminar flow under Bunsen burner
Technical field
The present invention relates to a kind of accurate measurement method of laminar flame velocity of propagation.
Background technology
Flame propagation velocity refers to the speed that move by contiguous unburned gas on vertical its surface direction on the flat flame corrugated.It is not only having very large Practical significance aspect the investigation flame holding, and broad theory is worth also having very aspect the research flame propagation theory.Bunsen flame method is a kind of flame propagation velocity measurements and calculations method commonly used, usually adopt the coning computation model, the average discharge with gaseous mixture under the Laminar Flow condition obtains average velocity as the laminar flame velocity of propagation divided by flame internal flame sharp side surface area.But because actual Bunsen burner mouth of pipe exit flow velocity distribution unevenness is different with outlet flame front different parts heat transfer characteristic, can cause the skewness of partial flame velocity of propagation, bigger than normal near tubular axis neutral flame point place, less than normal at the flame root area near the tube wall place, and at the flame zone line, then because velocity distribution is even, heat dissipation characteristics is identical, flame propagation velocity is substantially constant.At this moment, adopt coning based on average rate of discharge to calculate flame propagation velocity and can produce larger error.
Summary of the invention
The present invention is in order to improve existing Bunsen burner method coning computation model computational accuracy, thereby a kind of accurate measurement method of flame propagation speed of gas fuel laminar flow under Bunsen burner is provided.
The accurate measurement method of flame propagation speed of gas fuel laminar flow under Bunsen burner, it is realized by following steps:
Step 1, will trace particle introduce in the mixed gas tank and fully mix with gaseous fuel, form mixed airflow;
Step 2, the described mixed airflow of step 1 is passed into the Bunsen burner burner, light at burner outlet, form Bunsen flame;
Step 3, employing two-dimensional particles image taking speed instrument obtain the flow field figure picture of mouth of pipe top flame region;
Step 4, the flow field figure that step 3 is obtained look like to process, and obtain vertical mouth of pipe axial cross section flow field velocity diagram;
Step 5, employing CCD imager carry out image acquisition to Bunsen flame, obtain the Bunsen flame image;
Step 6, the Bunsen flame image that step 5 is obtained carry out carrying out curve fitting behind brightness analysis, the edge extracting, the curve after the acquisition match;
Curve after the match that step 7, flow field velocity figure and step 6 that step 4 is obtained obtain carries out location matches, and adopts interpolation calculation to go out each point gas velocity U on the good section of the curve Linear degree of step 6 acquisition n
N represents the sequence number put on the good section of curve Linear degree; Described n is positive integer;
The section that curve Linear degree is good is: flame front is carried out behind the linear fit with matched curve relative standard variance ± 1% with interior section;
Step 8, according to formula S n=U nCos θ nObtain the flame propagation velocity S of the described each point of step 7 n, get the flame propagation velocity S with each point nMean value be point within ± 0.5%～± 2% in relative standard's variance, and then ask for the flame propagation velocity S of each point nMean value, obtain Bunsen burner laminar flame velocity of propagation S 1
In the formula, θ nGas velocity U for n point on the flame front nAngle with this flame front normal.
Gaseous fuel described in the step 1 is the fuel blend of methane, oxygen and nitrogen, and the percent by volume of methane is 6.8%～14.3%, the percent by volume of oxygen is 17.8%～20.7%, the percent by volume of nitrogen is 67.6%～73.6%.
Adopt least square method that the image that CCD obtains is carried out curve fitting.
In step 6, adopt the brightness of image process software that the Bunsen flame image that step 5 obtains is carried out brightness analysis, edge extracting.
The spout diameter of Bunsen burner burner is 3mm～15mm.
Beneficial effect: the present invention uses two-dimensional particles image taking speed instrument (PIV) and CCD imager, adopts contactless mode that Bunsen burner laminar flame velocity of propagation is measured, and can not destroy the flame body construction.Because two-dimensional particles image taking speed instrument (PIV) can record the velocity amplitude of each point in the flow field, therefore flow field velocity figure and flame contours matched curve are carried out location matches, can obtain the flame propagation velocity value of each point on the flame front.The error that causes for the coning computation model has larger elimination, can realize Bunsen burner laminar flame velocity of propagation is accurately measured.
Description of drawings
Fig. 1 is schematic flow sheet of the present invention; Fig. 2 is the experimental provision structural representation in the specific embodiment of the invention six; Fig. 3 is the flame front synoptic diagram that gathers in the experiment of the specific embodiment of the invention six; Fig. 4 is the characteristic pattern on the experiment Flame sharp side of the specific embodiment of the invention six; Fig. 5 is the flame front matched curve figure in the experiment of the specific embodiment of the invention six; Fig. 6 is the principle schematic that the present invention measures flame propagation velocity.
Embodiment
Embodiment one, in conjunction with Fig. 1 this embodiment is described, the accurate measurement method of flame propagation speed of gas fuel laminar flow under Bunsen burner, it is realized by following steps:
Step 1, will trace particle introduce in the mixed gas tank and fully mix with gaseous fuel, form mixed airflow;
Step 2, the described mixed airflow of step 1 is passed into the Bunsen burner burner, light at burner outlet, form Bunsen flame;
Step 3, employing two-dimensional particles image taking speed instrument obtain the flow field figure picture of mouth of pipe top flame region;
Step 4, the flow field figure that step 3 is obtained look like to process, and obtain vertical mouth of pipe axial cross section flow field velocity diagram;
Step 5, employing CCD imager carry out image acquisition to Bunsen flame, obtain the Bunsen flame image;
Step 6, the Bunsen flame image that step 5 is obtained carry out carrying out curve fitting behind brightness analysis, the edge extracting, the curve after the acquisition match;
Curve after the match that step 7, flow field velocity figure and step 6 that step 4 is obtained obtain carries out location matches, and adopts interpolation calculation to go out each point gas velocity U on the good section of the curve Linear degree of step 6 acquisition n
N represents the sequence number put on the good section of curve Linear degree; Described n is positive integer;
The good section of described curve Linear degree is: flame front is carried out behind the linear fit with matched curve relative standard variance ± 1% with interior section;
Step 8, according to formula S n=U nCos θ nObtain the flame propagation velocity S of the described each point of step 7 n, get the flame propagation velocity S with each point nMean value, be point within ± 0.5%～± 2% in relative standard's variance, and then averaged, obtain Bunsen burner laminar flame velocity of propagation S 1
In the formula, θ nGas velocity U for n point on the flame front nAngle with this flame front normal.
The difference of the accurate measurement method of embodiment two, this embodiment and embodiment one described flame propagation speed of gas fuel laminar flow under Bunsen burner is that gaseous fuel described in the step 1 is the fuel blend of methane, oxygen and nitrogen.
The difference of the accurate measurement method of embodiment three, this embodiment and embodiment two described flame propagation speed of gas fuel laminar flow under Bunsen burners is, the percent by volume of methane is 6.8%～14.3%, the percent by volume of oxygen is 17.8%～20.7%, the percent by volume of nitrogen is 67.6%～73.6%.
The difference of the accurate measurement method of embodiment four, this embodiment and embodiment one, two or three described flame propagation speed of gas fuel laminar flow under Bunsen burners is, adopts least square method that the image that CCD obtains is carried out curve fitting.
The difference of the accurate measurement method of embodiment five, this embodiment and embodiment four described flame propagation speed of gas fuel laminar flow under Bunsen burners is, in step 6, adopt the brightness of image process software that the Bunsen flame image that step 5 obtains is carried out brightness analysis, edge extracting.
The difference of the accurate measurement method of embodiment six, this embodiment and embodiment one, two, three, four or five described flame propagation speed of gas fuel laminar flow under Bunsen burners is that the spout diameter of Bunsen burner burner is 3mm～15mm.
Below by concrete experimental verification effect of the present invention:
Experimental provision is as shown in Figure 2: described device comprises methane gas cylinder 1, oxygen gas cylinder 2, nitrogen gas cylinder 3, methane mass flow controller 4, oxygen quality flow controller 5, nitrogen mass flow controller 6, mass rate display instrument 7, mixed gas tank 8, trace particle introducing device 9, computing machine 10, CCD imager 11, focusing telescope 12, Bunsen burner burner 13, sheet laser light path system 14, laser instrument 15, PIV control, lock unit 16, synchronizer 17, optical filtering 18, CCD camera 19 and control software 20.Described methane mass flow controller 4 is used for measuring and controlling the flow of methane gas cylinder 1 eluting gas; Oxygen quality flow controller 5 is used for measuring and controlling the flow of oxygen gas cylinder 2 eluting gas; Nitrogen mass flow controller 6 is used for measuring and controlling the flow of nitrogen gas cylinder 3 eluting gas; The measuring-signal output terminal that the measuring-signal output terminal of methane mass flow controller 4, the measuring-signal output terminal of oxygen quality flow controller 5 are connected with the nitrogen mass flow controller is connected with three measuring-signal input ends of mass rate display instrument 7 respectively; The gas outlet of control methane gas cylinder 1, the gas outlet of oxygen gas cylinder 2, the gas outlet of nitrogen gas cylinder 3, the outlet of trace particle introducing device 9 are communicated with four air intake openings of mixed gas tank 8 respectively; The gas outlet of mixed gas tank 8 is communicated with the air intake opening of Bunsen burner burner 13; The light input end place of CCD imager 11 is provided with focusing telescope 12, and the flame light that described Bunsen burner burner 13 produces inputs to the light input end of focusing telescope 13; The signal output part of CCD imager 11 is connected with computing machine 10; PIV control, lock unit 16, synchronizer 17 form the control system of PIV, guarantee the accurate synchronization operation of system component; The flow field imaging is made of sheet laser light path system 14, take laser instrument 15 as light source; CCD camera 19 identification trace particles carry out image taking; Before CCD camera 19 camera lenses, optical filtering 18 has been installed, to reduce luminous flame to the impact of photographic images; Control software 20 is finished analysis and the demonstration to image.
In this experiment there be selected parameter: the flow velocity that methane mass flow controller 4, oxygen quality flow controller 5, nitrogen mass flow controller 6 are controlled respectively methane, oxygen, nitrogen is 0.1～5m/s; The flow velocity that the mixed gas of mixed gas tank 8 flows out is 0.2～10m/s, and the spout diameter of Bunsen burner burner 13 is 3mm～15mm, and interval value is every 1mm.
Adopt the CCD imager that Bunsen flame is carried out image acquisition in the experiment, obtain Bunsen flame sharp side picture as shown in Figure 3; The characteristic pattern that in the experiment Bunsen flame image is carried out flame front behind brightness analysis, the edge extracting as shown in Figure 4; Experiment Flame sharp side matched curve figure as shown in Figure 5.
When using the Bunsen burner method to carry out the measurement of flame propagation velocity, if supposing gas velocity is equally distributed along tube section, and do not consider that the high temperature of flame front is on the impact of fresh mixed gas, then flame front can be regarded as a positive taper, at this moment, actual flow with gaseous mixture can be used as flame propagation velocity divided by the average velocity that flame internal flame sharp side surface area obtains.But actual gas velocity is uneven distribution along tube section, can cause the uneven distribution of flame propagation velocity, and is less than normal at the flame root area near the tube wall place bigger than normal near the tubular axis center, then substantially constant at zone line.At this moment, adopt coning calculating can cause larger error.Thereby, need to get the constant zone of midrange speed and measure with Bunsen burner method Accurate Measurement flame propagation velocity if want.When flame front maintains static, the flame propagation velocity S on the each point of taper internal flame surface nThe normal direction component velocity v of (it is inner that direction is pointed to the taper internal flame) and this air-flow nIt is balance.Also namely there is following relational expression for the every bit on the taper flame front, is called again cosine law:
S n＝U n·cosθ n＝v n
In the formula: S nThe normal direction flame propagation velocity of any on the expression taper flame front; U nThe gas velocity that represents this point; v nThe normal direction component velocity that represents this air-flow; θ nThe gas velocity of each point and the angle between the flame front normal on the expression flame front.
Use two-dimensional particles image taking speed instrument (PIV) can obtain the flow field figure picture of mouth of pipe top flame region, process through image, can obtain the velocity profile in flow field.To process the resulting matched curve of ccd image and flow field velocity distribution plan and carry out location matches, then can obtain the corresponding gas velocity of each point on the curve, utilize above-mentioned computing formula, can obtain the flame propagation velocity value of each point.Choosing the good section of matched curve Linear degree calculates, can obtain the substantially constant flame propagation velocity value of each point, averaged, as recording laminar flame velocity of propagation empirical tests, the error that method of the present invention causes the coning computation model has larger elimination, and is higher to Bunsen burner laminar flame velocity of propagation degree of accuracy.

Claims (6)

1. the accurate measurement method of flame propagation speed of gas fuel laminar flow under Bunsen burner, it is characterized in that: it is realized by following steps:
Step 1, will trace particle introduce in the mixed gas tank and fully mix with gaseous fuel, form mixed airflow;
Step 2, the described mixed airflow of step 1 is passed into the Bunsen burner burner, light at burner outlet, form Bunsen flame;
Step 3, employing two-dimensional particles image taking speed instrument obtain the flow field figure picture of mouth of pipe top flame region;
Step 4, the flow field figure that step 3 is obtained look like to process, and obtain vertical mouth of pipe axial cross section flow field velocity diagram;
Step 5, employing CCD imager carry out image acquisition to Bunsen flame, obtain the Bunsen flame image;
Step 6, the Bunsen flame image that step 5 is obtained carry out carrying out curve fitting behind brightness analysis, the edge extracting, the curve after the acquisition match;
Curve after the match that step 7, flow field velocity figure and step 6 that step 4 is obtained obtain carries out location matches, and adopts interpolation calculation to go out each point gas velocity U on the good section of the curve Linear degree of step 6 acquisition n
N represents the sequence number put on the good section of curve Linear degree; Described n is positive integer;
The section that curve Linear degree is good is: flame front is carried out behind the linear fit with matched curve relative standard variance 1% with interior section;
Step 8, according to formula S n=U nCos θ nObtain the flame propagation velocity S of the described each point of step 7 n, get the flame propagation velocity S with each point nMean value be point within 0.5%～2% in relative standard's variance, and then ask for the flame propagation velocity S of each point nMean value, obtain Bunsen burner laminar flame velocity of propagation S 1
In the formula, θ nGas velocity U for n point on the flame front nAngle with this flame front normal.
2. the accurate measurement method of flame propagation speed of gas fuel laminar flow under Bunsen burner according to claim 1 is characterized in that gaseous fuel described in the step 1 is the fuel blend of methane, oxygen and nitrogen.
3. the accurate measurement method of flame propagation speed of gas fuel laminar flow under Bunsen burner according to claim 2, the percent by volume that it is characterized in that methane are 6.8%～14.3%, the percent by volume of oxygen is 17.8%～20.7%, the percent by volume of nitrogen is 67.6%～73.6%.
4. according to claim 1, the accurate measurement method of 2 or 3 described flame propagation speed of gas fuel laminar flow under Bunsen burners, it is characterized in that adopting least square method that the image that CCD obtains is carried out curve fitting.
5. the accurate measurement method of flame propagation speed of gas fuel laminar flow under Bunsen burner according to claim 4, it is characterized in that in step 6, adopt the brightness of image process software that the Bunsen flame image that step 5 obtains is carried out brightness analysis, edge extracting.
6. according to claim 1, the accurate measurement method of 2,3 or 5 described flame propagation speed of gas fuel laminar flow under Bunsen burners, the spout diameter that it is characterized in that the Bunsen burner burner is 3mm～15mm.
CN 201110148721 2011-06-03 2011-06-03 Method for measuring flame propagation speed of gas fuel laminar flow under Bunsen burner accurately Active CN102253234B (en)

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CN104062394B (en) * 2014-05-29 2016-03-02 南京航空航天大学 Liquid fuel gas phase Bunsen burner laminar flame propagation velocity measurement mechanism and measuring method thereof
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