RU2044306C1 - Fume meter of exhaust gases of diesel engine - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: fume meter has light source, forming optical system, optical commutator with drive, inclined mirror, two protective glasses, measurement chamber composed of two compartments with holes drilled in lower and upper walls of measurement compartment, interference filter, receiving optical system, photodetector with amplifier, temperature sensitive element located in measurement compartment of chamber, amplifier of element signal, multiplexer, analog-to-digital converter, demultiplexer, microprocessor, control unit, diffuser providing for mating of chamber to sampling pipe-line coupled to exhaust pipe of Diesel engine. Diffuser has two holes ensuring protection of protective glasses against soiling by means of suction of air from atmosphere which flows through holes in upper and lower walls of measurement compartment of chamber intended for passing of light radiation when exhausted gases of Diesel engine are exposed to radiation. EFFECT: enhanced authenticity of operation of fume meter. 1 dwg

Description

 The invention relates to measuring equipment and can be used in the fleet to determine the correct adjustment of the power system of cars with diesel engines according to the optical density of the exhaust gases.

 A known photoelectric smoke meter [1] in which in order to ensure continuous operation of the device under the conditions of intense exposure to polluting particles on the viewing windows, as well as the influence of other various destabilizing factors on the measurement accuracy, a two-channel device uses two light fluxes: measuring and control.

 The disadvantage of this device is the effect of contamination on the results of the analysis.

 Closest to the proposed device is a smoke meter [2] which contains a light source, a measuring and control photodetector, two cameras separated by a chimney and equipped with inspection windows and tubes for the passage of light to the control photodetector, an air supply pipe connecting the cameras to each other and located between the light source and a control photodetector, while the outputs of the photodetectors are connected to the corresponding inputs of the comparison unit, the output signals of which trigger the signaling devices, first the first of which informs about the excess of the established smoke density, and the second of the unacceptable contamination of the inspection windows.

 The need to use two photodetectors leads to the fact that due to the spread of their characteristics deteriorates the accuracy of the measurement of smoke, which is a disadvantage of this device.

 To eliminate this drawback, the proposed device uses one photodetector, and the radiation from the light source to the photodetector is sent using an optical switch either through an inclined mirror and the first compartment of the measuring chamber filled with the gas mixture under study, or through a second compartment free from this mixture, and for The signal processing of the photodetector uses the same electronic path, including an amplifier, a multiplexer, an analog-to-digital converter, a demultiplexer, and a microprocessor.

 The drawing shows a functional diagram of a device for measuring smoke exhaust gases of a diesel engine.

 The device for measuring smoke contains a light source 1, forming an optical system 2, an optical switch 3 with a drive 4, an inclined mirror 5, protective glasses 6 and 7, a camera 8, consisting of two compartments 9 and 10, the first of which is measuring, the second control, holes 13 and 14, an interference filter 15, a receiving optical system 16, a photodetector 17 with an amplifier 18, a temperature sensor 19 located in the measuring compartment 9 of the camera 8, an amplifier 20, a multiplexer 21, are made in the lower 11 and upper 12 walls of the measuring compartment digitally a howling converter 22, a demultiplexer 23, a microprocessor 24, a control unit 25, an indication unit 26, a diffuser 27 that interfaces the chamber 8 with a pipe 28 connected to the diesel exhaust pipe, while two openings 29 and 30 are made in the diffuser 27, which provide protection against pollution of the protective glasses 6 and 7 by sucking air from the atmosphere flowing through the openings 13 and 14, which serve to pass light radiation during transmission of the diesel exhaust gas in the measuring compartment 9 of the chamber 8.

 Let us explain the operation of the proposed device.

 Before measuring smoke, the pipe 28 is connected to the exhaust pipe of the diesel engine. The exhaust gases through the pipe 28 are directed through the diffuser 27 to the measuring compartment 9 of the chamber 8. The temperature of the gases in the measuring compartment 9 of the chamber 8 is controlled by the temperature sensor 19. An electrical signal proportional to the temperature of the gases in the chamber is amplified in the amplifier 20 and supplied to the first information input of the multiplexer 21. In this mode, the multiplexer 21 provides a signal generated by the temperature sensor 19 to the input of the analog-to-digital converter 22. The digital code generated by the converter 22 , using a demultiplexer 23 is fed to the first input of microprocessor 24. In microprocessor 24, this digital code passes through the corresponding memory register and enters block 26 to indicate eratury gases. As soon as the gas temperature lies in the range necessary for measuring smoke, the operator, using the control unit 25, gives a command to the microprocessor 24, by which a digital code proportional to the gas temperature is stored in the corresponding register, and three control signals are generated. The first of these signals provides switching of the multiplexer 21, the second switching of the demultiplexer 23, and the third switching of the optical switch 3.

 The optical switch 3 is a disk, one part of which transmits light radiation, and the other part reflects it. Under the influence of the control signal supplied to the input of the actuator 4 (for example, electromagnetic), the optical switch 3 reflects the radiation of the source 1, formed by the optical system 2, in the direction of the protective glass 6. Next, the light radiation through the protective glass 6 enters the control compartment 10 of the camera 8 providing optical coupling of the protective glass 6 with the protective glass 7.

 After passing through the protective glass 7 and the interference filter 15, the light radiation is focused using the receiving optical system 16 on the sensitive area of the photodetector 17. As can be seen from the above, in this case, the light radiation has no contact with the exhaust gases. Therefore, this radiation is control, and its flux received by the photodetector 17 is proportional to the transmission of the optical path.

i_λS_λфS_λфпdλ сила излучения в спектральном диапазоне [λ₁,λ₂] работы устройства; ε_o интегральная чувствительность фотоприемника; ω₁ угол охвата формирующей оптической системы 2 в стерадианах.If the spectral radiation power i _{λ of} source 1, the transmittance η of the optical path, and the relative spectral characteristics S _λf and S _{λfp of the} interference filter 15 and photodetector 17 are _known , then the amplitude U _{to the} signal at the output of the photodetector will be
U _K ε _o ηω ₁ I _o , (1) where I _o =

i _λ S _λф S _λфп dλ radiation power in the spectral range [λ ₁ , λ ₂ ] of the operation of the device; ε _{o the} integrated sensitivity of the photodetector; ω _{1 the} angle of coverage of the forming optical system 2 in steradians.

The output signal of the photodetector 17 is supplied to the amplifier 18, and then to the second information input of the multiplexer 21. This time, the multiplexer 21, under the influence of a control signal generated in the microprocessor 24, supplies the amplified signal of the photodetector 17 to the analog-to-digital converter 22 to convert its amplitude to digital the code. A digital code proportional to the amplitude U of _the signal is fed to the corresponding information input of the demultiplexer, which transmits this code to the microprocessor, where it is stored in the corresponding memory cells.

 Then the operator through the control unit 25 sets the command "Measurement" to the microprocessor 24. By this command, the corresponding signals are generated in the microprocessor 24, by which the optical switch 3 and the demultiplexer 23 are switched. In this mode, the light radiation of the source 1, which can be used as the lamp forming the optical system 2 is converted into a parallel beam, which, passing through the optical switch 3 and reflected from the inclined mirror 5, through the protective glass 6 and the hole 13 in the bottom wall 11 is guided into the measuring chamber 9 to the chamber 8 radiographic therein exhaust gases. Further, this radiation through the hole 14 in the upper wall 12 of the measuring compartment 9 of the camera 8 is directed to the protective glass 7, the interference filter 15 passes through it, and then with the aid of the receiving optical system 16 it focuses on the sensitive area of the photodetector 17. Since the smoke should be measured in visible spectral region, the spectral characteristic of the optical path using the interference filter 15 and the spectral characteristic of the photodetector 17 is performed by a similar curve of the sensitivity of the eye.

=

(3)
Справедливость формулы (3) вытекает из равенств (1) и (2).If K _{d the} exhaust smoke, then by analogy with the expression (1), the amplitude U _{of the} signal at the output of the photodetector 17 can be determined by the formula
U _of ε _o ηω ₁ I _o (1 K _d ) (2)
The output signal of the photodetector 17 after amplification in the amplifier 18 through the multiplexer 21 is fed to an analog-to-digital Converter 22, where it is converted into a digital code. The generated digital code, proportional to the amplitude U _{of the} signal, is supplied through the demultiplexer 23 to the corresponding input of the microprocessor 24. In the microprocessor 24 for a given temperature T _{about the} exhaust gases, the calculation of smoke is carried out in accordance with the expression
K

=

(3)
The validity of formula (3) follows from equalities (1) and (2).

 Since the exhaust smoke depends on the photometric base and temperature, the microprocessor 24 recalculates the obtained smoke readings.

If K _to opacity measured at a temperature T _o, the temperature T is equal to
K _d K _to ˙K _t , (4) where K _t (273 + T) / (273 + T _о ) is the correction temperature coefficient.

=К_д ^lтр^/l (6) С учетом (4) формула (6) приводится к виду
К_дтр=(К_д˙К_т)^lтр^/l (7)
В микропроцессоре 24 с помощью формулы (7) осуществляется приведение показаний прибора к заданной температуре Т и фотометрической базе l_тр. Полученный результат подается в блок 26 для индикации показаний дымности. Введение температурного поправочного коэффициента повышает точность прибора, а использование фотометрической базы l, меньшей l_тр, с последующим приведением показаний к требуемому значению фотометрической базы дает возможность уменьшить габаритные размеры измерительной камеры и ее массы, а следовательно, и всего прибора в целом.Smoke K _d associated with the photometric base l and the absorption coefficient α by the following equality:
K _d exp (- α˙l) (5)
If the required photometric base l _tr differs from the photometric base l used in the device, then when calculating the smoke, use the expression
TO

= K _d ^l tr ^{/ l} (6) Taking into account (4), formula (6) is reduced to
K _dtr = (K _d ˙K _t ) ^l tr ^{/ l} (7)
In microprocessor 24, using the formula (7), the readings of the device are brought to a predetermined temperature T and a photometric base l _tr . The result is fed to block 26 to indicate smoke readings. The introduction of a temperature correction coefficient increases the accuracy of the device, and the use of a photometric base l less _than l _tr , with subsequent reduction of the indications to the required value of the photometric base, makes it possible to reduce the overall dimensions of the measuring chamber and its mass, and therefore the entire device as a whole.

 To protect the glasses 6 and 7 from pollution, two air streams are formed in the device, passing through the holes 13 and 14, respectively, optically coupled to the protective glasses 6 and 7. The formation of these flows is as follows. The exhaust gases passing through the pipeline 28, due to the high speed and instant expansion in the diffuser 27, create a vacuum at the openings 29 and 30. Through these openings, atmospheric air is sucked in and two flows flow through the openings 13 and 14 of the first compartment 9 of the measuring chamber 8 .

(1-K

). (8)
Как видно из формулы (8), чем больше разброс параметров фотоприемников и интерференционных фильтров, тем значительней ошибка измерения дымности. При использовании же одного фотоприемника технологические, темпеpатурные и другие нестабильности в спектральных характеристиках фотоприемника и интерференционного фильтра не вносят ошибок в измерение дымности.If two photodetectors were used in the device to receive the control and measuring flows, respectively, then when the spectral characteristics of photodetectors and interference filters are scattered (technological deviations, scatter due to temperature changes, aging, etc.), an error ΔK _d in the measurement of smoke
ΔK _d =

(1-K

) (8)
As can be seen from formula (8), the greater the variation in the parameters of photodetectors and interference filters, the greater the error in measuring smoke. When using one photodetector, technological, temperature and other instabilities in the spectral characteristics of the photodetector and interference filter do not introduce errors into the measurement of smoke.

 From the above it follows that the use of the proposed device can reduce the size and weight of the device; increase measurement accuracy; exclude the influence of instability of the spectral characteristics of the photodetector on the results of measurements of smoke.

Claims (1)

 FUEL EXHAUST GAS DIMENSION METER, comprising a camera paired with a sampling pipe through a diffuser, a radiation source, two protective glasses, the photodetector connected to a photo-recording circuit, characterized in that an optical switch with a drive is inserted into it to form a measuring optical path and a control optical tract, a temperature sensor with an amplifier, and the camera is divided into two compartments, one of which is measuring, the other is control, while measuring is connected to the sampling pipe the chamber, the temperature sensor is installed in the measuring compartment of the camera, the measuring optical path includes optically paired an inclined mirror optically paired with an optical switch, the first protective glass installed in the camera body, the first and second diaphragms and the second protective glass installed in the housing cameras optically coupled to a photodetector, the control optical path includes optically paired a first protective glass mounted in the camera body, paired opt with an optical switch, a second protective glass mounted in the camera’s body, optically paired with a photodetector, the first and second diaphragms are made in the form of holes in the walls of the measuring compartment of the camera, respectively, in the first and second holes, holes for suction of atmospheric air are made in the walls of the diffuser, one of which is located between the protective glass and the first wall of the measuring compartment of the camera, the other between the second wall of the measuring compartment of the camera and the protective glass, and the registration circuit contains a series-connected multiplexer, an analog-to-digital converter, a demultiplexer and a microprocessor, the control input of which is connected to the output of the control unit, the first output to the input of the display unit, the second output to the drive of the optical switch, the third output to the control input of the demultiplexer, the fourth output to the control the multiplexer input, the first information input of which is connected to the amplifier output, and the second information input through the preamplifier with the photodetector output ka.

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