CN105352862A - Method for detecting metal abrasive particles in oil in direct-current electric field on basis of microchannels - Google Patents

Abstract

The invention provides a method for detecting metal abrasive particles in oil in a direct-current electric field on the basis of microchannels. The method comprises steps as follows: sampled oil is dropped in two liquid storage tanks of focusing channels respectively, and after a main channel and detection channels are soaked with to-be-sampled oil, the same volume of to-be-detected sample oil containing an ionic surfactant and the metal abrasive particles is dropped into a first liquid storage tank; a signal amplification circuit is connected, and the voltage value of a direct-current power supply is adjusted; the metal abrasive particles in the to-be-detected oil pass by a detection area, the resistance of oil in the detection area changes, current in the main channel changes, and voltage pulse signals generated at two ends of the channel are detected, pass by the signal amplification circuit and are transmitted to a signal acquisition unit; a processor determines the number and the size of the metal particles contained in the to-be-detected sample according to signals acquired by the signal acquisition unit. The particles are detected on basis of change of system resistance when the particles pass the detection area, and the detection accuracy of the abrasive particles in the oil is improved.

Description

A kind of method detecting metal worn particle in fluid based on microchannel under DC electric field

Technical field

The embodiment of the present invention relates to micro-fluidic technologies field, particularly relates to a kind of method detecting metal worn particle in fluid based on microchannel under DC electric field.

Background technology

Hydraulic oil and lubricating oil play power transimission and lubrication in all kinds of plant equipment, each operative minor rubs in the course of the work and produces a large amount of particle, and wherein metallic particles is major pollutants and causes the excessive wear of equipment working surface and then component function is reduced even losing efficacy.Statistics show, the hydraulic system fault more than 75%, the diesel engine operation troubles of 35%, the gear failure of 38.5% and 40% rolling bearing lost efficacy all by lubricating oil lost efficacy cause.Therefore, periodic monitoring oil cleanliness detect metal particle concentration and particle size in fluid and seem particularly important.

Current engineering mainly contains analytic ferrographic method to the balancing method of contamination level of oil liquid, pollutes gravimetry, microscope relative method, granule counting method etc., in these methods, beyond particle-removing counting method, other several methods can only be estimated to a certain extent to contamination level of oil liquid grade, and the result obtained is affected by human factors to a great extent.And granule counting method is determined size and the concentration of particle in fluid really to realize the accurate detection of particle in fluid by the pulse signal amplitude measuring particle and produce through surveyed area and quantity.

Summary of the invention

The embodiment of the present invention provides a kind of method detecting metal worn particle in fluid based on microchannel under DC electric field, detects the not high enough problem of degree of accuracy to overcome in prior art for the metal worn particle in fluid.

The present invention is based on the method that metal worn particle in fluid is detected in microchannel under DC electric field, comprising:

Sampling fluid is instilled in two reservoirs of focus channel respectively, infiltrates after described main channel and described sense channel until described sampling fluid, the testing sample fluid containing ionic surfactant and metal worn particle of same volume is instilled the first reservoir;

Connection signal amplifying circuit also adjusts the magnitude of voltage of direct supply;

Described testing sample fluid is transported to surveyed area under DC electric field electroosmotic flow and electrophoretic action, when metal worn particle in fluid to be measured will change through described surveyed area fluid resistance, cause curent change in described main channel, thus described sense channel two ends produce voltage pulse signal, described pulse signal is through signal amplification circuit and transfer to signal gathering unit;

The signal number that processor gathers according to described signal gathering unit and amplitude determine the metallic particles number that contains in described testing sample and size.

Further, described ion-type surfactant concentration exceedes its critical micelle concentration in fluid.

Further, the signal number that described processor gathers according to described signal gathering unit and amplitude determine the metallic particles number that contains in described testing sample and size, comprising:

Described processor is determined the particle diameter of described metallic particles according to the amplitude of collection signal, is determined the number of described metallic particles according to the number of described collection signal.

Further, described connection signal amplifying circuit before adjusting the magnitude of voltage of direct supply, also comprising:

Instill in described focus channel not containing the sample fluid of ionic surfactant.

Compared with prior art, the present invention has following beneficial effect:

1) drastically increase the sensing range of metal worn particle size in fluid, according to surveyed area size, particle diameter 5 μm and above metal worn particle can be detected;

2) concentration is added in fluid to be measured more than the ionic surfactant of CMC, improves the conductivity of fluid to be measured, make metal worn particle transporting under DC electric field become possibility;

3) sample fluid transports under DC electric field effect electroosmotic flow and electrophoretic action, can the flowing of Precise Control of Oil liquid, and eliminates external discharge pump;

4) ionic surfactant is added on a small amount of moisture effectively can eliminated in fluid to be measured and contain in fluid, gets rid of the detection interference caused by water droplet.

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 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 the present invention is based on the method flow diagram that metal worn particle in fluid is detected in microchannel under DC electric field;

Fig. 2 detects metal worn particle apparatus structure schematic diagram in fluid for the present invention is based on microchannel under DC electric field;

Fig. 3 is the entity structure schematic diagram of apparatus of the present invention;

Fig. 4 is the equivalent schematic circuit figure of apparatus of the present invention;

Fig. 5 is the circuit theory diagrams of signal amplification circuit in apparatus of the present invention.

Embodiment

For making the object of the embodiment of the present invention, technical scheme and advantage clearly, below in conjunction with the accompanying drawing in the embodiment of the present invention, technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is 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.

Fig. 1 detects metal worn particle method flow diagram in fluid for the present invention is based on microchannel under DC electric field, and as shown in Figure 1, the method for the present embodiment, comprising:

Step 101, by sampling fluid instill in two reservoirs of focus channel respectively, infiltrate after described main channel and described sense channel until described sampling fluid, the testing sample fluid containing ionic surfactant and metal worn particle of same volume is instilled the first reservoir;

Step 102, connection signal amplifying circuit adjust the magnitude of voltage of direct supply;

Step 103, described testing sample fluid are transported to surveyed area under DC electric field electroosmotic flow and electrophoretic action, when metal worn particle in fluid to be measured will change through described surveyed area fluid resistance, cause curent change in described main channel, thus described sense channel two ends produce voltage pulse signal, described pulse signal is through signal amplification circuit and transfer to signal gathering unit;

The signal number that step 104, processor gather according to described signal gathering unit and amplitude determine the metallic particles number that contains in described testing sample and size.

Specifically, when described metal worn particle passes through the surveyed area of micro-fluid chip, the resistance of described surveyed area can change, and its resistance value reduced can represent with following formula:

$\mathrm{\Δ}R=\frac{4{\mathrm{\ρd}}^3}{{\mathrm{\πD}}^4}\[1+\frac{2d^3}{3D^{2}L}+{\left(\frac{2d^3}{3D^{2}L}\right)}^2+\mathrm{...}\]---\left(1\right)$

Wherein, ρ is the resistivity of fluid, and d is the particle diameter of metal worn particle, D and L is diameter of section and the length of surveyed area passage respectively.

When not having metal worn particle in described surveyed area through out-of-date, the electric current I of main channel is:

$I=\frac{V_{+}-V_{-}}{R_1+R_2+R_3}---\left(2\right)$

When described surveyed area have metal worn particle by time, main channel electric current I ' be:

$I^{\′}=\frac{V_{+}-V_{-}}{R_1+R_2+R_3-\mathrm{\Δ}R}---\left(3\right)$

Derive can obtain in conjunction with formula (1), (2), (3), when described sense channel have metal worn particle by time, the Δ V of described sense channel both end voltage change after amplifying circuit _outputfor:

${\mathrm{\ΔV}}_{output}=-\frac{\mathrm{\Δ}R(R_1+R_3)(V_{+}-V_{-})}{{(R_1+R_2+R_3)}^2-\mathrm{\Δ}R(R_1+R_2+R_3)}---\left(4\right)$

Because the equivalent resistance in described passage can be expressed as:

$R_1=\mathrm{\ρ}\frac{4L_1}{{{\mathrm{\πD}}_1}^2}---\left(5\right)$

$R_2=\mathrm{\ρ}\frac{4L_2}{{{\mathrm{\πD}}_2}^2}---\left(6\right)$

$R_3=\mathrm{\ρ}\frac{4L_3}{{{\mathrm{\πD}}_3}^2}---\left(7\right)$

In conjunction with formula (4), (5), (6), (7), described Δ V _outputcan be expressed as through deriving:

${\mathrm{\ΔV}}_{output}=\frac{(\frac{L_1}{{D_1}^2}+\frac{L_3}{D_3^2})\frac{d^3}{D_2^4}}{{(\frac{L_1}{{D_1}^2}+\frac{L_1}{D_2^2}+\frac{L_3}{D_3^2})}^2-(\frac{L_1}{{D_1}^2}+\frac{L_1}{D_2^2}+\frac{L_3}{D_3^2})\frac{d^3}{D_2^1}}(V_{-}-V_{+})---\left(8\right)$

Further, described ionic surfactant concentration exceedes its critical micelle concentration in fluid.Wherein, described ion-type activating agent comprises anionic surfactant and cationic surfactant.

Further, described connection signal amplifying circuit before adjusting the magnitude of voltage of direct supply, also comprising:

Instill in described focus channel not containing the sample fluid of ionic surfactant.

Specifically, instill not containing the sample fluid of ionic surfactant in described focus channel, its effect is the impact that elimination non-uniform electric field moves on metal worn particle, and metal worn particle is moved along channel center as far as possible.

Further, the signal number that described processor gathers according to described signal gathering unit and amplitude determine the metallic particles number that contains in described testing sample and size, comprising:

Described processor is determined the particle diameter of described metallic particles according to the amplitude of collection signal, is determined the number of described metallic particles according to the number of described collection signal.

Specifically, the judgement of described metal worn particle particle diameter: different size metal worn particle resistance variations in the region that surveyed area causes is different, cause sense channel two ends to detect voltage pulse signal amplitude different, therefore judge the metal worn particle particle diameter by surveyed area according to the size of potential pulse amplitude.

As being d with reference to calibration diameter ₁standard metal particle, when utilizing this standard metal particle to test, the voltage pulse signal amplitude that sense channel two ends detect is Δ V ₁, be d with containing detection metal worn particle particle diameter _xfluid when testing, the voltage pulse signal amplitude that sense channel two ends detect is Δ V _x, according to formula the metal worn particle particle diameter derived in sample fluid is

Fig. 2 detects metal worn particle apparatus structure schematic diagram in fluid for the present invention is based on microchannel under DC electric field, and device can comprise as shown in Figure 2:

Main channel 101, surveyed area 102, sense channel 103, first reservoir 104, second reservoir 105, the 3rd reservoir 106, the 4th reservoir 107, first platinum electrode 108, second platinum electrode 109, the 3rd platinum electrode 110, the 4th platinum electrode 111, metallic particles 112, described sense channel comprises upstream detection passage and detected downstream passage;

Described main channel is used for transporting fluid to be measured, the centre position of described main channel arranges described surveyed area 102, described upstream detection passage and detected downstream passage are drawn in the two ends of described surveyed area, two ends, described main channel are respectively arranged with the first reservoir 104 and the second reservoir 105, this first reservoir stores the described fluid to be measured containing metallic particles sample, this second reservoir is for storing the waste liquid after detection, described upstream detection expanding channels has the 3rd reservoir 106, described detected downstream expanding channels has the 4th reservoir 107, described first platinum electrode 108 inserts in described first reservoir 104, described second platinum electrode 109 inserts in the second reservoir 105, described 3rd platinum electrode 110 inserts in described 3rd reservoir 106, described 4th platinum electrode 111 inserts in described 4th reservoir 107, described first, second platinum electrode is connected with the both positive and negative polarity of direct supply respectively, described 3rd, 4th platinum electrode is connected with the input end of amplifier respectively, the output terminal of described amplifier is connected with signal gathering unit.Focus channel 113, for eliminating non-uniform electric field effect, described focus channel 113 is arranged between described surveyed area 102 and the first reservoir 104, both sides, described main channel 101.5th reservoir 114, the 6th reservoir 115, described 5th reservoir, the 6th reservoir are arranged at the two ends of described focus channel 113 respectively, for the sample introduction tank of described focus channel.

Specifically, before the sample introduction of main channel, the pure fluid of ionic surfactant AOT is not first contained in the instillation of focus channel sample introduction tank, it is made to flow along both sides, main channel inwall, then in main channel, sample introduction is carried out, the fluid that main channel includes metal worn particle to be detected along main channel center flow, will eliminate the adhesive attraction that inside microchannels non-uniform electric field causes.

As shown in Figure 3,1 is microscope slide, and 2 is dimethyl silicone polymer micro-fluid chip, and 3 is chip internal channel.Microchannel dimethyl silicone polymer micro-fluid chip application soft lithography intaglio passage on PDMS micro-fluid chip of the present embodiment, card punch is utilized to punch in channel end, and the side of being carved with passage is placed upward, put into plasma cleaner to clean together with microslide, then both are into a single integrated structure by the rear sealing-in of one side laminating of cleaning, namely described PDMS micro-fluid chip forms with microslide the microchannel formed for detecting containing metallic particles sample between the two.

Wherein, described signal amplification circuit is secondary differential amplifier circuit.

Wherein, described signal gathering unit is data collecting instrument, and described data collecting instrument adopts LABVIEW software.

Specifically, as shown in Figure 4, be the equivalent circuit diagram of the differential detection circuit of the present embodiment device, described main channel length and cross section live width are respectively L1, L3 and D1, D3, main channel 1 described in the present embodiment with 3 length and cross section live width size design identical; Thus equivalent resistance length is L1, L3, equivalent resistance diameter of section is D1, D3, and described surveyed area sense channel length and diameter of section are respectively L2 and D2, and corresponding equivalent resistance length is L2, and equivalent resistance diameter of section is D2.V+, V-are the electromotive force that two ends, main channel direct supply produces, V1, V2 are the potential change value that surveyed area detects, R1, R3 are respectively the equivalent resistance of upstream, main channel, downstream, R2 is the equivalent resistance of described surveyed area passage, and Δ R is the surveyed area resistance variations that described detection metallic particles causes through surveyed area.3rd platinum electrode, the 4th platinum electrode are connected with the input end of amplifier respectively, and form complete signal amplification circuit, the output terminal of described amplifier is connected with signal gathering unit.

Figure 5 shows that secondary differential amplifier principle schematic of the present invention, as shown in Figure 5, to be secondary differential amplifier be made up of firsts and seconds amplifier based on the signal secondary differential amplifier circuit of AD620 amplifier in the present embodiment, voltage signal from detecting electrode sends into the input end of the first order two differential signal amplifiers first respectively, signal is after first stage amplifier process, signal obtains A1 and doubly amplifies, and the noise of system is cut down, the signal exported from first stage amplifier is then sent into the amplifier of the second level, carry out continuation to signal to amplify, because the input end signal polarity of two first stage amplifier is contrary, the polarity of its output signal is also contrary.Therefore, signal is after the two-stage amplifier process that gain is A2, and the total enlargement factor of final system is A=2A1A2.The signal gathering unit of the present embodiment is that data collecting instrument carries out data acquisition with suitable frequency acquisition, and data collecting instrument coordinates described LABVIEW software application, and final data display and storage are on computers.The present embodiment difference processing has high immunity to external electromagnetic interference, and differential signal is conducive to identifying feeble signal, and differential signal does not need virtual earth, thus adds fidelity and the stability of ambipolar signal.

The present invention adopts described micro-fluid chip as detection carrier, can test on the chip of several square centimeters, its microchannel size is in micron level, use the magnitude of described detection sample fluid in microliter range, considerably reduce the consumption of sample fluid, be more conducive to the development of metal worn particle checkout equipment in portable fluid.The AD620 differential amplifier adopted is a single core instrument grade amplifier, its gain controllable, low-power consumption, low input offset voltage, low input imbalance drift, low input bias current, there is splendid common-mode rejection ratio and low input noise and peak noise, outstanding AC characteristic etc., can be this research and eliminate external noise interference, bias current etc. the treating method of signal amplification more is accurately provided.The present invention accurately can not only detect the number of metal worn particle in described fluid, and can infer this metal worn particle particle size according to signal amplitude size, is plant equipment, and especially the abrasive wear of hydraulic system provides a kind of effective discrimination method.

Last it is noted that above each embodiment is only in order to illustrate technical scheme of the present invention, be not intended to limit; Although with reference to foregoing embodiments to invention has been detailed description, those of ordinary skill in the art is to be understood that: it still can be modified to the technical scheme described in foregoing embodiments, or carries out equivalent replacement to wherein some or all of technical characteristic; And these amendments or replacement, do not make the essence of appropriate technical solution depart from the scope of various embodiments of the present invention technical scheme.

Claims (4)

1. under DC electric field, detect a method for metal worn particle in fluid based on microchannel, it is characterized in that, comprising:

Sampling fluid is instilled in two reservoirs of focus channel respectively, infiltrates after described main channel and described sense channel until described sampling fluid, the testing sample fluid containing ionic surfactant and metal worn particle of same volume is instilled the first reservoir;

Connection signal amplifying circuit also adjusts the magnitude of voltage of direct supply;

Described testing sample fluid is transported to surveyed area under DC electric field electroosmotic flow and electrophoretic action, when metal worn particle in fluid to be measured will change through described surveyed area fluid resistance, cause curent change in described main channel, thus described sense channel two ends produce voltage pulse signal, described pulse signal is through signal amplification circuit and transfer to signal gathering unit;

The signal number that processor gathers according to described signal gathering unit and amplitude determine the metallic particles number that contains in described testing sample and size.

2. method according to claim 1, is characterized in that, described ion-type surfactant concentration exceedes its critical micelle concentration in fluid.

3. method according to claim 1 and 2, is characterized in that, the signal number that described processor gathers according to described signal gathering unit and amplitude determine the metallic particles number that contains in described testing sample and size, comprising:

Described processor is determined the particle diameter of described metallic particles according to the amplitude of collection signal, is determined the number of described metallic particles according to the number of described collection signal.

4. method according to claim 1, is characterized in that, described connection signal amplifying circuit also before adjusting the magnitude of voltage of direct supply, also comprises:

Instill in described focus channel not containing the sample fluid of ionic surfactant.