CN103630479B - A kind of measuring method of engine combustion exhaust particulate number - Google Patents

Abstract

The present invention relates to field of measuring technique, propose the measuring method of the method engine combustion exhaust particulate of the present invention number of a kind of measurement point combustion engine or compression ignition engine exhaust particulate number, mainly comprise gather candidate particles sample, candidate particles sample dispersion treatment, obtain discrete particles sem image, judge agglomerated particle degree of scatter, determine flex point number and the too much particle of arc length number, eliminating flex point number and arc length number, judge M _ithe steps such as middle individual particle number, finally obtain engine combustion exhaust particulate number N _sum.Contrast oneself and have technology, it is simple and easy that the present invention has measurement mechanism, do not need to obtain amounts of particles by the conversion of electric current, can obtain the feature of granule number intuitively.

Description

A kind of measuring method of engine combustion exhaust particulate number

Technical field

The present invention relates to field of measuring technique, propose a kind of method of measurement point combustion engine or compression ignition engine exhaust particulate number.

Background technology

The particle (particulatematter, PM) that motor car engine is discharged has become one of main source of air environmental pollution thing.2013, automobile " capital V " emission standard was implemented in Beijing, and automobile " state IV " emission standard will be implemented in nationwide.In stricter Abgasgesetz, except to except the quantitative limitation of motor vehicle emission particulate matter, also add the restriction requirement to particle number (particulatenumber, PN).Engine particle can be divided into thick state (1 ~ 10 μm), aggregative state (100 ~ 300nm) and core state (particle diameter is less than 50nm) according to particle size.Chinese scholars research shows, granular mass particle emission peak concentrates on aggregative state and thick state, and amounts of particles particle emission peak concentrates on core state.Measure engine combustion grain diameter rapidly and accurately, for the quantitative test of different-grain diameter granular mass and quantity discharge, and reduce granular mass and quantity discharge has great importance.

Grain diameter is different by measuring method, can be divided into aerodynamic diameter and electron transfer diameter.Aerodynamic diameter utilizes gravitational method, and electron transfer diameter utilizes number of particles Size Distribution method.For engine combustion particle, at present, the device measuring grain diameters such as scanning/transmission electron microscope (SEM/TEM), electrostatic low pressure ram (ELPI), scan-type electromigration grain graininess instrument (SMPS), amounts of particles and particle size analyzer (EEPS) are mainly adopted both at home and abroad.In measuring principle, SEM/TEM is by shooting particle sem image, and directly measure grain diameter, transformed error is little, can realize the high-acruracy survey of grain diameter in theory.Engine particle exists with the form of particle swarm usually, particle swarm contains tens to a hundreds of individual particle, overlaps, be difficult to distinguish the profile of individual particle by means of only particle image between individual particle, and sem image obtains is local granule image, statistically poor.ELPI, SMPS and EEPS method mainly utilizes particle charge or electrostatic interaction, wherein, ELPI is made up of multi-stage impinger, utilizes the inertia of charged particle, measure and be deposited on the electric current that on ram, charged particle produces, indirectly obtain the number concentration of different-grain diameter (0.03 ~ 10 μm) particle.These three kinds of measuring methods are all indirectly obtain grain diameter and quantity by the conversion of electric signal, the particle diameter of the particle size results obtained mainly particle swarm, can not reflect the individual particle particle diameter situation that burning is formed, and measuring equipment are complicated, expensive.

For the deficiency of said method, a kind of method measuring engine combustion granule number is rapidly and accurately proposed, the method of invention is conducive to the measuring method simplifying grain diameter, and reduce expense needed for testing equipment, for meeting, state five requirement of Abgasgesetz to grain count is significant.

Summary of the invention

The object of the invention is, in order to measure engine combustion exhaust particulate number, to propose a kind of measuring method of engine combustion granule number.

For achieving the above object, the technical solution used in the present invention is:

A measuring method for engine combustion exhaust particulate number, comprises the steps:

Step 1: gather candidate particles sample;

Engine combustion particle in employing filter membrane collection engine main exhaust passageway is as candidate particles sample;

Step 2: the dispersion treatment of candidate particles sample;

Adopt ethanol/dichloromethane solution to extract particulate samples to be measured, ultrasonic disperse carried out to the suspending liquid after extraction, the solution after dispersion after filtration, dry after, obtain grain diameter and analyze sample;

Step 3: the sem image obtaining discrete particles;

Gather the image that grain diameter analyzes sample, obtain pending agglomerated particle sem image;

Step 4: the degree of scatter judging agglomerated particle;

Remember that total number of agglomerated particle in pending agglomerated particle sem image is M, adopt M _irepresent i-th agglomerated particle, i=1,2 ... M; According to the base plate lattice dimensions of pending agglomerated particle sem image, lattice method is adopted to measure M _iprojected area note be less than 1 μm ²agglomerated particle number be M ^*if, M ^*< 90%M, returns step 2; If M ^*>=90%M, thinks that particle tentatively disperses, note M _ithe number of middle individual particle is N _i, continue to enter step 5;

Step 5: determine flex point number and arc length number;

Torispherical hypothesis is carried out to individual particle, adopts curve fitting method to M _iprofile carry out matching, obtain matched curve, then carry out knee point differentiation, obtain the flex point number G of closed curve _iwith arc length number H _i.

Step 6: get rid of flex point number and the too much particle of arc length number;

If G _i> 8 or H _i> 8, gets rid of this agglomerated particle;

If G _i=0,1,2,3 ... 8, retain this agglomerated particle, then H _i=1,2 ... 8;

Step 7: judge M _imiddle individual particle number;

Step 7.1,

If G _i=0, think when only to have an individual particle in agglomerated particle, N _i=1;

If G _i≠ 0, i.e. N _i>=2, enter step 7.2;

Step 7.2, determine N _iscope:

Work as N _iwhen>=2, according to flex point number G _i, arc length number H _iand following formula determination particle number N _iscope:

$(\frac{G_i}{2}+1)\&le;N_i\&le;(G_i+1)---\left(1\right)$

$(\frac{H_i}{2}+1)\&le;N_i\&le;H_i---\left(2\right)$

N _ispan be: be greater than 1 and meet the positive integer of formula (1) and formula (2) simultaneously;

Step 7.3, eliminating N _ithe unreasonable situation of value:

N in step 7.2 will be met _ithe N of span _ivalue judges as follows:

If meet N _i=G _i+ 1, and H _i≠ 2G _i, then this N is got rid of _ivalue; Otherwise, then this N is retained _ivalue;

Get rid of N _iafter the unreasonable situation of value, note N _ican the number of value be Z _i, continue to enter step 7.4;

Step 7.4,

If Z _i=1, then N _ibe M _imiddle individual particle number;

If Z _i>=2, enter step 7.5;

Step 7.5, by solving M _ithe diameter of middle individual particle, obtains the number of individual particle:

Step 7.5.1, the arc length of matched curve remembered between adjacent two flex points are , y is the ordinal number of arc length, and note with air line distance between two corresponding flex points is through type (3) calculates for corresponding particle diameter;

$D_y^i\&times;\sin (180\&times;\frac{C_y^i}{\mathrm{\&pi;}{D}_y^i})=A_y^i---\left(3\right)$

Step 7.5.2, according to each calculate one by one obtain the set of particle diameter corresponding to arc length, for

The particle of step 7.5.3, eliminating same diameter:

To gather in each different numerical value only extract one, form new set; The number obtaining numerical value in this new set is this M _ithe number N of middle individual particle _i;

Step 8: screening M _iin all be less than 1 μm ²agglomerated particle, adopt the method for step 7 to judge M one by one _imiddle individual particle number, the set of acquired results is designated as the individual particle number in particulate samples;

Step 9: to the individual particle number summation in all particulate samples obtained in step 8, namely obtain engine combustion exhaust particulate number N _sum.

The invention has the beneficial effects as follows: contrasting oneself has technology, and it is simple and easy that the present invention has measurement mechanism, do not need to obtain amounts of particles by the conversion of electric current, the feature of granule number can be obtained intuitively.

Accompanying drawing explanation

Accompanying drawing is used to provide a further understanding of the present invention, and forms a part for instructions, together with embodiments of the present invention for explaining the present invention, is not construed as limiting the invention.In the accompanying drawings:

Fig. 1: the original sem image of particle of the embodiment of the present invention.

Fig. 2: the effect schematic diagram of topography after the process of the embodiment of the present invention.

Fig. 3: the process flow diagram that granule number is measured.

Specific embodiments

Below in conjunction with specific embodiment, the present invention is described:

Step 1: gather candidate particles sample;

Engine combustion particle in employing filter membrane collection engine main exhaust passageway is as candidate particles sample; What adopt in the present embodiment is glass fiber filter, and sampling flow controls as 5L/min, and the sampling time is 10min.

Not before dispersion treatment, as shown in Figure 1, particle is chain to engine combustion particle sem image, bulk, floccule mass are got together, and the measurement of granule number is comparatively difficult.

Step 2: the dispersion treatment of candidate particles sample;

Adopt ethanol or dichloromethane solution to extract particulate samples to be measured, the addition of solvent is 5 times of particulate samples quality, and extraction leaves standstill 5min.Ultrasonic disperse is carried out to the suspending liquid after extraction, adopts the solution after being less than 300 object carbon nets/copper mesh filtration ultrasonic disperse, by baker, the carbon net/copper mesh containing particle is evaporated, obtain grain diameter and analyze sample.

Step 3: the sem image obtaining discrete particles;

Adopt scanning/transmission electron microscope to gather the image of grain diameter analysis sample, measurement range and precision can meet the measurement of grain diameter.After gradation of image, Edge contrast, obtain pending agglomerated particle sem image, Fig. 2 is the effect schematic diagram of topography after process.

Step 4: the degree of scatter judging agglomerated particle;

Remember that total number of agglomerated particle in pending agglomerated particle sem image is M=15, adopt M _irepresent i-th agglomerated particle, i=1,2 ... 15; According to the base plate lattice dimensions of pending agglomerated particle sem image, lattice method is adopted to measure M _iprojected area be respectively: 0.43,0.21,0.15,0.32,0.31,1.12,0.38,0.21,0.35,0.46,0.37,0.19,0.22,0.33,0.27 μm ².Note be less than 1 μm ²agglomerated particle number be M ^*=1, M ^*meet M ^*>=90%M, thinks that particle tentatively disperses, note M _ithe number of middle individual particle is N _i.

A certain agglomerated particle M ₁for example, calculate the number of individual particle in agglomerated particle, continue to enter step 5.

Step 5: determine flex point number and arc length number;

Torispherical hypothesis is carried out to individual particle, adopts curve fitting method to M ₁profile carry out matching, obtain matched curve, then carry out knee point differentiation, obtain the flex point number G of closed curve ₁=5 and arc length number H ₁=5.

Step 6: get rid of flex point number and the too much particle of arc length number;

Because M ₁flex point number G ₁meet " G _i=0,1,2,3 ... 8 ", so retain M ₁, then H _i=1,2 ... 8.

Step 7: judge M ₁middle individual particle number;

Step 7.1,

Because G ₁≠ 0, i.e. N ₁>=2, so enter step 7.2;

Step 7.2, determine N ₁scope:

Because N ₁when>=2, according to flex point number G ₁, arc length number H ₁and following formula determination particle number N ₁scope:

$(\frac{G_1}{2}+1)\&le;N_1\&le;(G_1+1)---\left(1\right)$

$(\frac{H_1}{2}+1)\&le;N_1\&le;H_1---\left(2\right)$

N ₁span be: meet 4≤N ₁the positive integer of≤5;

Step 7.3, eliminating N ₁the unreasonable situation of value:

N in step 7.2 will be met ₁the N of span ₁value (N ₁=4 and N ₁=5) judge:

Because N ₁=4 and N ₁=5 all do not meet " N _i=G _i+ 1, and H _i≠ 2G _i", so retain this N ₁value;

Note N ₁can the number of value be Z ₁, Z ₁=2, continue to enter step 7.4;

Step 7.4,

Because Z ₁=2 meet " Z _i>=2 ", so enter step 7.5;

Step 7.5, by solving M ₁the diameter of middle individual particle, obtains the number of individual particle:

Step 7.5.1, the arc length of matched curve remembered between adjacent two flex points are , y is the ordinal number of arc length, be respectively: 0.5,0.33,0.41,1.14,0.78 μm.And note with air line distance between two corresponding flex points is be respectively: 0.12,0.074,0.327,0.309,0.298 μm, through type (3) calculates corresponding particle diameter;

$D_y^1\&times;\sin (180\&times;\frac{C_y^1}{\mathrm{\&pi;}{D}_y^1})=A_y^1---\left(3\right)$

Step 7.5.2, according to each calculate one by one obtain the set of particle diameter corresponding to arc length, for be respectively: 0.2,0.13,0.36,0.47,0.36 μm.

The particle of step 7.5.3, eliminating same diameter:

To gather in each different numerical value only extract one, form new set; The number obtaining numerical value in this new set is this M ₁the number N of middle individual particle ₁=4;

Step 8: screening M _iin all be less than 1 μm ²agglomerated particle, adopt the method for step 7 to judge M one by one _imiddle individual particle number, the set of acquired results is designated as the individual particle number in particulate samples; Obtain N ₁~ N ₅be respectively: 4,3,1,3,5, be greater than 1 μm ², so get rid of M ₆, N ₇~ N ₁₅be respectively: 5,3,3,4,5,4,4,4,2.

Step 9: to the individual particle number summation in all particulate samples obtained in step 8, namely obtain engine combustion exhaust particulate number N _sumbe 50.

Below by reference to the accompanying drawings specific embodiment of the invention scheme is described; but these explanations can not be understood to limit scope of the present invention; protection scope of the present invention is limited by the claims of enclosing, and any change on the claims in the present invention basis is all protection scope of the present invention.

Claims (1)

1. a measuring method for engine combustion exhaust particulate number, is characterized in that comprising the steps:

Step 1: gather candidate particles sample;

Engine combustion particle in employing filter membrane collection engine main exhaust passageway is as candidate particles sample;

Step 2: the dispersion treatment of candidate particles sample;

Adopt ethanol/dichloromethane solution to extract particulate samples to be measured, ultrasonic disperse carried out to the suspending liquid after extraction, the solution after dispersion after filtration, dry after, obtain grain diameter and analyze sample;

Step 3: the sem image obtaining discrete particles;

Gather the image that grain diameter analyzes sample, obtain pending agglomerated particle sem image;

Step 4: the degree of scatter judging agglomerated particle;

Remember that total number of agglomerated particle in pending agglomerated particle sem image is M, adopt M _irepresent i-th agglomerated particle, i=1,2 ... M; According to the base plate lattice dimensions of pending agglomerated particle sem image, lattice method is adopted to measure M _iprojected area note be less than 1 μm ²agglomerated particle number be M ^*if, M ^*< 90%M, returns step 2; If M ^*>=90%M, thinks that particle tentatively disperses, note M _ithe number of middle individual particle is N _i, continue to enter step 5;

Step 5: determine flex point number and arc length number;

Torispherical hypothesis is carried out to individual particle, adopts curve fitting method to M _iprofile carry out matching, obtain matched curve, then carry out knee point differentiation, obtain the flex point number G of closed curve _iwith arc length number H _i;

Step 6: get rid of flex point number and the too much particle of arc length number;

If G _i> 8 or H _i> 8, gets rid of this agglomerated particle;

If G _i=0,1,2,3 ... 8, retain this agglomerated particle, then H _i=1,2 ... 8;

Step 7: judge M _imiddle individual particle number;

Step 7.1,

If G _i=0, think only there is an individual particle, N in agglomerated particle _i=1;

If G _i≠ 0, i.e. N _i>=2, enter step 7.2;

Step 7.2, determine N _iscope:

Work as N _iwhen>=2, according to flex point number G _i, arc length number H _iand following formula determination particle number N _iscope:

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N _ispan be: be greater than 1 and meet the positive integer of formula (1) and formula (2) simultaneously;

Step 7.3, eliminating N _ithe unreasonable situation of value:

N in step 7.2 will be met _ithe N of span _ivalue judges as follows:

If meet N _i=G _i+ 1, and H _i≠ 2G _i, then this N is got rid of _ivalue; Otherwise, then this N is retained _ivalue;

Get rid of N _iafter the unreasonable situation of value, note N _ican the number of value be Z _i, continue to enter step 7.4;

Step 7.4,

If Z _i=1, then N _ibe M _imiddle individual particle number;

If Z _i>=2, enter step 7.5;

Step 7.5, by solving M _ithe diameter of middle individual particle, obtains the number of individual particle:

Step 7.5.1, the arc length of matched curve remembered between adjacent two flex points are y is the ordinal number of arc length, and note with air line distance between two corresponding flex points is through type (3) calculates for corresponding particle diameter;

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Step 7.5.2, according to each calculate one by one obtain the set of particle diameter corresponding to arc length, for

The particle of step 7.5.3, eliminating same diameter:

To gather in each different numerical value only extract one, form new set; The number obtaining numerical value in this new set is this M _ithe number N of middle individual particle _i;

Step 8: screening M _iin all be less than 1 μm ²agglomerated particle, adopt the method for step 7 to judge M one by one _imiddle individual particle number, the set of acquired results is designated as the individual particle number in particulate samples;

Step 9: to the individual particle number summation in all particulate samples obtained in step 8, namely obtain engine combustion exhaust particulate number N _sum.