JPH0260254B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to dry suit (carbon particles to which soluble organic matter (SOF) is not attached) and soluble organic fraction (SOF) contained in the exhaust gas of diesel engines. This invention relates to a real-time particulate concentration measuring device.

Conventional technology Conventionally, the concentration of dry suit and SOF was measured using a sampling pump from a dilution tunnel to collect particulate on a filter, and after controlling the temperature and humidity of the filter, it was weighed on a chemical balance. By doing so, the patteikurate concentration was determined. Plus dry suits and SOF
The concentration of SOF was measured by soaking and extracting only the SOF from the filter that collected the particulate and weighing the amount of dry suit left behind. However, it took a long time to measure and it was difficult to measure in real time. It had problems such as being impossible.

Purpose of the invention The purpose of the present invention is to install a dry suit on two filters arranged in one sampling pipe.
The SOF is separated and collected by suction, and for dry suits, the increase in pressure loss before and after the filter is approximately proportional to the weight of the deposit, and for SOF, the increase in pressure loss before and after the filter is proportional to the increase in pressure loss before and after the filter. Based on the idea that the amount of pressure loss after subtracting the influence of pressure loss is approximately proportional to the weight of the deposit, we can measure the concentration of particulates in internal combustion engine exhaust gas in real time and in a relatively short period of time. It's about doing things correctly.

Structure of the Invention The present invention includes a dilution tunnel that dilutes and mixes exhaust gas from an internal combustion engine with a large amount of clean air and guides the diluted and mixed gas to a detection means, and a sampling system for taking out a portion of the diluted mixed gas from the dilution tunnel. a first filter installed in the middle of the sampling pipe to collect the dry suit;
a heating means provided upstream of the sampling pipe than the first filter; a first differential pressure converter for detecting a pressure difference before and after the first filter; a dry suit amount calculation circuit that calculates the amount of dry suit in exhaust gas; a second filter that is provided downstream of the first filter and upstream of the sampling pump and that collects soluble organic matter; a second differential pressure transducer that detects the pressure difference before and after the filter;
and the time differential value of the pressure difference signal to the first
Using the signal value of the pressure difference from the differential pressure converter, correct it to a value when the pressure difference before and after the first filter is zero, and calculate the amount of soluble organic matter in the exhaust gas based on the corrected pressure difference signal. There is provided an apparatus for measuring the concentration of particulates in exhaust gas of an internal combustion engine, which is characterized by comprising a soluble organic matter amount calculation circuit.

Embodiment FIG. 1 shows an apparatus for measuring the concentration of particulates in internal combustion engine exhaust gas as an embodiment of the present invention.

As a premise for explaining the embodiments of the present invention, the influence of the pressure loss of the dry suit collection filter on the SOF collection filter will be explained.

When the sampling pump 16 is suctioning at an equal mass flow rate Q, the pressure immediately before passing through the dry suit collection filter 13 is P _d , the flow rate is V _d ,
When the pressure immediately before passing through the SOF collection filter 15 is P _s and the flow velocity is V _s , the following equation (1) holds true.

Q=k ₁・P _d・V _d =k ₁・P _s・V _s (k ₁ is a constant) ...(1) If the pressure loss of the dry suit collection filter 13 is ΔP _d , then P _s = P _d −△P _d , so V _s
will increase by P _d /(P _d −△P _d ).
On the other hand, the pressure loss ΔP in the filter is expressed by the following equation (2) using the flow velocity V of the passing fluid and the viscosity coefficient μ.

ΔP=k ₂ ·V · μ (k ₂ is a constant) (2) Therefore, as V _s increases, the pressure loss in the SOF collection filter 15 increases. In other words, the pressure loss △ at the SOF collection filter 15
When the pressure immediately after passing through the dry suit collection filter 13, that is, the pressure immediately before the SOF collection filter 15 _, decreases from _Ps1 to _Ps2 , Ps increases as shown in the following equation (3).

△p _s1 = P ₀₁ +k ₃・W …(3) △P _s2 =k ₄ (P _s1 /P _s2 ) (P ₀₁ +k ₃・W) …(4) Here, P ₀₁ is SOF deposited on the filter This is the pressure loss when not in use, W is the amount of SOF deposited, k ₃ ,
k ₄ is a constant. Therefore, if P _s1 is the standard pressure, the SOF deposition amount W when the pressure loss in the dry suit collection filter 13 increases by △P _d is calculated by using P _s2 in equation (4).
It can be obtained as shown in the following equation (5) by replacing P _s1 −△P _d .

W={△P _s2 (P _s1 −△P _d ) / (k ₄ · P _s1 ) − P ₀₁ } / k ₃ ...(5) In the device shown in Figure 1, E is a diesel engine, and 3 is an exhaust gas in a dilution tunnel. Gas is sucked at a constant velocity in the direction of arrow 31 by a roots blower (not shown) or the like. 43 is a division valve that can appropriately divide the exhaust gas into the dilution tunnel 3 and the exhaust port 44. 25
is the sampling pipe, 26 and 27 are the valves,
28 is a coil heater, and 29 is a temperature regulator that adjusts the temperature of the exhaust gas after passing through the coil heater. 1
3 is a dry suit collection filter made of glass fiber coated with Teflon. 15 is
The SOF collection filter is made of Teflon. 1
2 and 14 are temperature detectors, which are set just before the filters 13 and 15.

54 and 55 are differential pressure converters, which detect the differential pressure before and after the dry suit collection filter 13 and the differential pressure before and after the SOF collection filter 15. Reference numeral 16 denotes a sampling pump for suctioning a constant flow rate, and has equipment such as a pump, a buffer tank, a flow meter, and a computing unit inside. Reference numeral 6 denotes a calculation device for calculating the dry suit and SOF concentration, which receives output signals from the temperature detectors 12 and 14, output signals from the differential pressure converters 54 and 55, and a sampling flow rate signal from the sampling pump 16, and performs calculations. Note that a relatively long cooling pipe 18 is provided between the dry suit collection filter 13 and the SOF collection filter 15.

It will be explained below that by heating the exhaust gas, particulates in the exhaust gas can be separated into dry suit and SOF. FIG. 2 shows an experimental device for determining the relationship between the collected matter on the filter and the temperature in front of the filter, with a filter 152 on the downstream side of a sampling pipe 151 and a temperature detector 153 immediately upstream of this filter 152. , this temperature sensor 1
Coil heaters 154 are provided on the upstream side of 53, and the coil heaters 154 are connected to variable DC power supply 155.
Power is supplied by The exhaust gas is sucked through the sampling pipe 151 in the direction of arrow 156,
It is discharged through filter 152. Here, the temperature in front of the filter 152 is changed by adjusting the variable DC power supply 155.

Figure 3 shows the temperature TEMP1 in front of the filter 152.
52 and the weight U of the collected material accumulated on the filter 152. In Figure 3, the shaded area U ₇
represents the deposited weight after Soxhlet extraction of the filter 152 with dichloromethane without heating, that is, when only dry suit is collected on the filter 152. Items U ₁ to _{U 6} that are not shaded indicate the weights of deposits without Soxhlet extraction. U ₁ without heating, U ₂ at 50℃, U ₃
is 100℃, U ₄ is 150℃, U ₅ is 200℃, and U ₆ is 250℃.

From Figure 3, the deposited weight is the highest when not heated by the coil heater 154, and as the temperature increases, the deposited weight decreases, and becomes approximately constant at 200°C or higher, which is the same as in the case of Soxhlet extraction. I understand that. That is, the filter 152
If the temperature in front of the
Only the dry suit is collected on the filter 152, and the SOF is passed through the filter 152. Particulates in the exhaust gas are separated into the dry suit and SOF.

This SOF can be cooled and condensed in a suitably extended sampling pipe and collected by a filter installed in the middle of this pipe. For this purpose, in the apparatus shown in FIG. provided.

dry suit collected on the filter and
The relationship between the stacked weight of SOF and the differential pressure across the filter will be explained below. Although it can be easily estimated that the ventilation resistance of the filter will generally increase as the amount of particles deposited on the filter increases, the present invention will not work unless there is a quantitative relationship between the two. Also, when fine particles of the same weight are deposited,
It is thought that the ventilation resistance will differ if the properties of the particles differ, and the properties of the dry suits and SOF discharged from diesel engines may also change depending on the operating conditions.

FIGS. 4 and 5 are graphs showing the relationship between the experimentally determined dry suit and SOF collection amount U (SOF) (mg) and the pressure loss ΔP (mmAq) in the filter. In the diagram, A and A', B and B', and C.
C' has engine operating conditions of 1000 rpm, low load,
The relationship between the amount of collected particulates discharged under a medium load of 2000 rotations and a high load of 3000 rotations and pressure loss ΔP is shown. Furthermore, the portions indicated by D and D' indicate the ventilation resistance of the filter itself. As is clear from Figures 4 and 5, the pressure loss △P of the collection filter has a very good proportional relationship with the amount of dry suit and SOF collected, and it is not affected much by the engine operating conditions. Recognize.

In addition, the temperature before the filter in Figure 4 is 225℃,
The temperature before the filter in FIG. 5 is 45°C.
The sampling gas flow rate is 20°C at 25°C.
/minute.

Dry suit discharged per unit time or
If the weight of SOF particles is W′, then W′ is calculated by the following formula
It is expressed as (6).

W′=m(Q+q) …(6) Here, W′ is particulate emission per unit time (mg/sec, etc.), m is particulate weight in unit volume of sampling gas (mg/ ^m3 , etc.), and Q is The diluted mixed gas blower flow rate (m ³ /sec, etc.), and q is the sampling gas flow rate (m ³ /sec, etc.).

Among the quantities included in the above equation (6), the particle weight m in the unit volume of the sampling gas during sampling could not be determined by conventional methods, but considering the pressure loss characteristics of the filters 13 and 15 mentioned above, It can be obtained as follows. filter 13,
Since the pressure loss in No. 15 is proportional to the amount of collected particles and proportional to the flow rate, the increase in pressure loss d(ΔP) of the filter during the minute time dt is expressed by equation (7).

d(△P)=K・m・q・dt・q …(7) Here, △P is pressure loss (Kg/ ^m3, etc.), K is a constant determined by the filter diameter and other factors, and m・q・dt is The weight (g, etc.) of fine particles collected by the filter during dt is expressed as: From equation (7), m can be found using equation (8).

m=1/Kq ²・d(△P)/dt...(8) Here, K is a constant determined by the filter diameter, etc., and d(△P)/dt is the time differential value of the filter pressure loss.

By determining the weight m of particulates in a unit volume of sampling gas using equation (8), the momentary amount of particulate emissions during mode driving can be determined using equation (6) described above. Note that the blower flow rate Q of the diluted mixed gas and the sampling gas flow rate q included in equation (6) take approximately constant values during the test, so they can be treated as constants.

In this way, by determining the time differential value of the pressure loss of the filters 13 and 15, which have the characteristics of being proportional to the amount of trapped particles and proportional to the sampling gas flow rate, the weight of the dry suit and SOF in a unit volume of the sampling gas can be determined. can know,
In the end, you can know the amount of dry suit and SOF emissions while driving in mode.

The experimental results shown in FIG. 5 were obtained using the experimental apparatus shown in FIG. In FIG. 6, exhaust gas is sucked in the direction of arrow 160 and coil heater 161 is used.
Configuration of an experimental device that heats to 200°C or higher, collects only the dry suit with a large auxiliary filter 162, collects SOF with a SOF collection filter 163, and detects the differential pressure across the filter with a differential pressure converter 164. The temperature in front of the filter is detected by the temperature detector 165, and SOF is efficiently collected when the temperature is about 50°C. In addition, even if about 10 mg of dry suit accumulates on the auxiliary filter, the front part 167 of the filter and the rear part 16 of the filter
This is a filter in which the differential pressure with respect to 8 hardly increases. During experimentation, the differential pressure transducer 166 makes it known that the pre-filter section 167 and the post-filter section 168 are at approximately the same pressure.

In the device shown in Figure 1, a filter with pressure loss characteristics as shown in Figure 4 is used as the dry suit collection filter, so as the dry suit accumulates, a considerably large pressure loss is caused at the rear part of the filter. It turns out. In other words, when performing equal flow rate suction, the dry suit collection filter 13
The pressure loss at will increase the exhaust gas velocity passing through the SOF collection filter 15,
Since the pressure loss characteristics of the SOF collection filter 15 will be different from those shown in FIG. 5, the value of the pressure loss must be corrected using the value of the pressure loss of the dry suit collection filter 13.

This correction method will be explained below. In FIG. 1, when the sampling pump 16 is suctioning at an equal mass flow rate Q, the dry suit collection filter 13
The pressure just before passing through is P _d , the flow velocity is V _d ,
The pressure just before passing through the SOF collection filter 15
When P _s is the flow velocity and V _s is the flow velocity, the following relationship holds true.

Q = k ₁ p _d V _d = k ₁ p _s V _s (however, k ₁ is a constant) ...(9) Therefore, if the pressure loss of the dry suit collection filter 13 is △p _d , p _s = p _d −△p _d , so
Equation (10) is obtained.

V _s = V _d p _d / (p _d −△p _d ) …(10) On the other hand, in general, the pressure loss △p when fluid passes through a filter is expressed by equation (11) using the fluid flow velocity V and viscosity coefficient μ. It is expressed as follows.

Δp=k ₂ Vμ (11) Here, k ₂ is a constant determined by the filter.

Therefore, when the pressure just before passing through the dry suit collection filter 13 is p _d and the pressure loss is △p _d ,
The pressure loss in the SOF collection filter 15 is △p′ _s
Then, the pressure loss △p _s that removes the influence of pressure loss in the dry suit collection filter 13 is expressed as
It becomes like (12).

△p _s = △p′ _s (p _d −△p _d )/p _d …(12) In other words, this corrected pressure loss △p _s has a proportional relationship with the amount of SOF collected as shown in Figure 5. I will have it.

The operation of the FIG. 1 apparatus will now be described. First, at the start of mode driving, the valve 26 opens, and the diluted mixed gas is sucked into the sampling pipe 25.
It is heated to 200° C. or higher by the coil heater 28.
The heated gas passes through the dry suit collection filter 13
The dry suit passes through filter 13 first.
is collected by. At this time, the SOF passes through the filter 15, but after passing through the cooling pipe 18, it is collected by the SOF collection filter 15. The differential pressure across the dry suit collection filter 13 and the SOF collection filter 15 is determined by differential pressure converters 54 and 55, and the signals thereof are input to the calculation device 6, respectively.

The calculation device 6 further includes temperature detectors 12 and 14.
and a signal indicating the sampling flow rate from the sampling pump 16 are input. The reason for inputting the temperatures in front of the filters 13 and 15 to the calculation device 6 is that as the gas temperature increases, the volume and viscosity of the gas increases, and the differential pressure before and after the filters increases. This is to correct the increase in differential pressure.

The relationship between this temperature and the differential pressure increase based on temperature is △p=aT+b under the condition of constant mass flow rate, and this △p is subtracted from the differential pressure determined by the differential pressure converters 54 and 55. Perform temperature correction. However, T and the absolute temperatures a and b are constants determined by the sampling flow rate and the type of filter.

The arithmetic unit 6 receives the above signals,
By determining the weight of the dry suit and SOF in a unit volume of sampling gas based on the above-mentioned calculation formula and reading this, it is possible to know in real time the amount of dry suit and SOF discharged while the vehicle is running.

The arithmetic processing in the arithmetic device 6 will be explained below. FIG. 7 is a block diagram showing the configuration of the arithmetic unit 6. First, the calculation process of dry suit discharge amount will be explained. In order to correct the differential pressure signal p _d of the dry suit collection filter to the differential pressure at 200° C., the temperature sensor signal T _d in front of the filter is used, and the comparator 71
A multiplier 602 performs temperature correction on the differential pressure signal _pd .

Next, the differential pressure signal is sent to two sets of gate circuits 603,
At 605, the differential pressure signal is passed through at a certain sampling time, held by hold circuits 604 and 606, and the output of the hold circuit 606 is subtracted from the output of the hold circuit 604 by a subtracter 607, thereby obtaining the time differential dp _d of the differential pressure signal. /dt.
This signal is then divided by a signal Q ² _d corresponding to the square of the flow rate from the sampling pump (612).
By dividing through, the formula becomes 1/Q ² / _d・dp _d /dt.
The same calculation as (4) can be performed and the amount of dry suit discharged can be determined. AD this signal at each sampling time.
It is converted and displayed.

Next, the calculation process for SOF emissions is almost the same as for dry suits, but the temperature correction of the SOF collection filter differential pressure signal p _s is performed using the temperature detector signal.
Using T _s , comparator 615 and multiplier 616,
The differential pressure is constantly corrected to 50℃. In addition, since the differential pressure of the SOF collection filter increases more than it appears due to the increase in the differential pressure of the dry suit collection filter, in order to correct this, the dry suit differential pressure signal after temperature correction (output of multiplier 602) using comparator 6
17, is performed by a multiplier 618. Further, the dry suit discharge amount signal s (612) and the SOF discharge amount signal s (624) are added by an adder 627 to obtain the particulate discharge amount, which is also displayed in the same manner.

In carrying out the present invention, various modifications can be made in addition to the above-described embodiments. For example, in the above description, the sampling gas is heated using a coil heater, but instead of this, a ribbon heater may be wrapped around the outer periphery of the sampling pipe, or heating may be performed using a burner or the like. Furthermore, when heating the sampling gas with a coil heater, a heat insulating material or the like can be provided outside the pipe.

Effects of the Invention According to the present invention, a dry suit on two filters arranged in one sampling pipe and a
SOF is separated and collected by suction, and for dry suits, the increase in pressure loss before and after the filter is almost proportional to the weight of the deposited weight, and for SOF, the increase in pressure loss before and after the filter is proportional to the increase in pressure loss before and after the filter. By subtracting the influence of pressure loss and using the fact that the amount of pressure loss is almost proportional to the accumulated weight, it is possible to accurately measure the concentration of particulates in internal combustion engine exhaust gas in real time and in a relatively short time. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a device for measuring the concentration of particulates in internal combustion engine exhaust gas as an embodiment of the present invention, and FIG.
The figure shows an experimental setup for determining the relationship between the collected material on the filter and the temperature in front of the filter. Figure 3 shows the relationship between the temperature in front of the filter and the accumulated weight of the collected material on the filter. Characteristic diagram. Figure 4 is a characteristic diagram showing the relationship between drysuit collection amount and filter pressure loss, Figure 5 is a characteristic diagram showing the relationship between SOF collection amount and filter pressure loss, and Figure 6 is a characteristic diagram showing the relationship between SOF collection amount and filter pressure loss. FIG. 7 is a diagram showing an experimental apparatus for determining the relationship between losses, and FIG. 7 is a diagram showing the configuration of a calculation circuit in the apparatus shown in FIG. Explanation of symbols, 12...Temperature detector, 13...Dry suit collection filter, 14...Temperature detector,
15... SOF collection filter, 16... Sampling pump, 18... Cooling pipe, 25... Sampling pipe, 26, 27... Valp, 28
...Coil heater, 29...Temperature regulator, 3...
Dilution tunnel, 43... Division valve, 44... Exhaust port, 54, 55... Differential pressure converter, 6... Arithmetic unit, E... Diesel engine.

Claims (1)

[Claims] 1. A dilution tunnel that dilutes and mixes the exhaust gas of the internal combustion engine with a large amount of clean air and guides the diluted and mixed gas to the gas detection means, a sampling pipe for taking out a portion of the diluted mixed gas from the dilution tunnel, and a portion in the middle of the sampling pipe. a first filter provided in the sampling pipe to collect the dry suit, a heating means provided upstream of the sampling pipe from the first filter, and a first differential pressure converter to detect a pressure difference before and after the first filter. a dry suit amount calculation circuit that calculates the amount of dry suit in the exhaust gas based on the time differential value of the pressure difference signal; a second filter that collects soluble organic matter, a second differential pressure converter that detects a pressure difference before and after the second filter, and a time differential value of the signal of the pressure difference from the first differential pressure converter. The amount of soluble organic matter is corrected to a value when the pressure difference before and after the first filter is zero using the signal value of the pressure difference, and the amount of soluble organic matter in the exhaust gas is calculated based on the corrected pressure difference signal. A device for measuring the concentration of particulates in exhaust gas of an internal combustion engine, comprising: an arithmetic circuit.