JPH0415897B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a device for measuring in real time the amount of dry suit such as carbon particles and soluble organic matter (hereinafter referred to as SOF) contained in the exhaust gas of a diesel engine. be.

Prior Art Conventionally, the concentration of dry suits and SOF in exhaust gas has been measured as follows. First, particulates in the exhaust gas are collected on a filter, the temperature and humidity of this filter are adjusted, and then the particulate concentration is measured by weighing with a chemical balance. Next, SOF is extracted from the particles on the filter using a Soxhlet device, and the concentration of the dry suit and SOF is determined from the weighed results. However, due to this type of processing, it takes time to measure the concentration of dry suits and SOF, and it is impossible to grasp concentrations that change from moment to moment, making it difficult to comply with strict exhaust gas regulations for diesel engines. Have difficulty.

In view of this point, the applicant has already filed a patent application in 1983-
In No. 203641, we proposed a device that measures the concentration of dry suit and SOF contained in exhaust gas in real time.

Problems to be Solved by the Invention The above proposed device heats the exhaust gas to a constant temperature and collects the dry suit or SOF on the filter, but if there is a large error in the fluctuation of the heating temperature, the dry suit or The error in the measured value of the amount of SOF becomes large. SUMMARY OF THE INVENTION The present invention has been made with the object of providing a particulate emission measurement device that can perform more accurate measurement by minimizing the range of variation in heating temperature.

Means for Solving the Problems The device of the present invention dilutes and mixes the exhaust gas of a natural engine with a large amount of clean air in a dilution tunnel, and then guides this diluted mixed gas to first and second detection means, and This is a particulate emission measurement device for a vehicle in which the detection means detects the amount of dry suit in the exhaust gas, and the second detection means detects soluble organic matter in the exhaust gas. The first detection means includes a first sampling pipe for taking out a part of the diluted mixed gas from the diluted tunnel, a first sampling pump for flowing the diluted mixed gas into the first sampling pipe, and the first sampling pipe. a first filter installed in the middle of the pipe to collect the dry suit;
A first heating means is provided upstream of the first sampling pipe than the first filter and has a constant calorific value, and a first heating means is provided downstream of the first heating means to heat the diluted mixed gas to the final heating temperature. A second heating means for heating, a first differential pressure converter for detecting the pressure difference before and after the first filter, and calculating the amount of dry suit in the exhaust gas based on the time differential value of the signal of this pressure difference. and a first arithmetic unit. The second detection means includes a second sampling pipe for taking out a portion of the diluted mixed gas from the dilution tunnel, a second sampling pump for flowing the diluted mixed gas into the second sampling pipe, and the second sampling pipe. a relatively large auxiliary filter that is provided in the middle of the second sampling pipe to collect the dry suit; a third heating means that is provided above the second sampling pipe than the auxiliary filter and has a certain amount of heat; a fourth heating means provided downstream of the third heating means and heating the diluted mixed gas to the final heating temperature; a second filter provided downstream of the auxiliary filter collecting soluble organic matter; It includes a second differential pressure converter that detects the pressure difference before and after the filter, and a second calculation device that calculates the amount of soluble organic matter in the exhaust gas based on the time differential value of the signal of this pressure difference.

Example The present invention will be explained below based on illustrated embodiments.

FIG. 1 shows a first embodiment of the present invention. In this figure, an exhaust pipe 2 extending from a diesel engine 1 branches into two at a split valve 3, one of which is connected to an exhaust port 4 and the other communicated with a dilution tunnel 5. Therefore, the exhaust gas discharged from the engine 1 is divided at the division valve 3 and discharged from the exhaust port 4, while a portion is supplied into the dilution tunnel 5.

The dilution tunnel 5 mixes the air taken in from the intake port 2 and the exhaust gas taken in from the branch pipe 7 of the intake pipe 2. The diluted mixed gas formed by mixing the exhaust gas and air is passed through a roots blower (not shown). etc., and flows at a constant speed in the direction of arrow A. A thermometer 8 is installed in the middle of the dilution tunnel 5 to detect the temperature inside the tunnel, and first and second sampling pipes 10, 30
The tip of is facing you. These sampling pipes 1
0 and 30 are for taking in the diluted mixed gas and detecting the amount of dry suit and SOF in the exhaust gas, respectively.

A first sampling pump 11 is installed on the downstream side of the first sampling pipe 10 to suck the diluted mixed gas at a constant flow rate, and inside this pump 11 are a buffer tank for absorbing pulsation, a flow meter, and a computing unit. Equipment such as these will be installed. The first sampling pipe 10 is provided with a valve 12 in a portion close to the dilution tunnel 5, coil heaters 13 and 22 immediately downstream of this valve 12, and a first filter 14 downstream thereof.
A temperature sensor 15 is installed immediately upstream of the temperature sensor 15 . A pressure detector 1 is installed before and after the first filter 14.
6 and 17 are provided. These pressure detectors 1
A signal indicating the pressure detected by the filters 6 and 17 is input to the first differential pressure converter 18, converted into a signal indicating the differential pressure before and after the filter 14, and then sent to the first computing unit 19.
is input. A temperature detector 15 and a first sampling pump 11 are also connected to this calculator 19 . The first filter 14 collects the dry suit, and the amount of the collected dry suit is determined by the filter 1 as described below.
It is determined based on the pressure difference around 4. Note that the electric power supplied to the coil heater 13 is
0 provides a constant output. On the other hand, the electric power supplied to the coil heater 2 is regulated by a PID temperature controller 21 that performs temperature control by feeding back the temperature detected by the temperature detector 15.

A mechanism similar to that of the first sampling pipe 10 is provided on the downstream side of the second sampling pipe 30 as well. That is, a second sampling pump 31 similar to the first sampling pump 11 is provided at the most downstream side, and a valve 32 is installed at a portion near the dilution tunnel 5. Also valve 3
Coil heaters 33 and 42 immediately downstream of 2, a second filter 34 downstream of that, and this second filter 3
Temperature detectors 35 are provided immediately upstream of the temperature sensors 4 and 4, respectively. Pressure detectors 36 and 37 are installed before and after the second filter 34, and these pressure detectors 3
The output signals of 6 and 37 are input to a second differential pressure converter 38. This second differential pressure converter 38, second sampling pump 31, and temperature detector 35
It is connected to a computing unit 39. Also, the coil heater 33
The power supplied to the coil heater 42 is supplied at a constant output from the slider 40, and the power supplied to the coil heater 42 is a PID temperature controller that feeds back the temperature detected by the temperature detector 43 through proportional + integral + differential control operations. 41.

The functions of these mechanisms are basically the same as those provided downstream of the first sampling pipe 10, but the second filter 34 is the same as the one provided downstream of the first sampling pipe 10.
Unlike 4, it collects SOF. Second filter 34
In order to collect only SOF, an auxiliary filter 44 for collecting dry suit is installed upstream of the second filter 34 and immediately downstream of the coil heater 42. This auxiliary filter 44 has the same material and composition as the first filter 14, but its diameter is several times larger than that of the first filter 14. Note that the auxiliary filter 44 and the second filter 3
4, a relatively long cooling pipe 45 is provided.

Next, we will explain that by heating the exhaust gas, particles in the exhaust gas can be separated into dry suits 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 52 on the downstream side of the sampling pipe 51 and a temperature detector 53 immediately upstream of this filter 52. Coil heaters 54 are provided upstream of the temperature detectors 53, and the coil heaters 54 are supplied with electric power from a variable DC power source 55. Exhaust gas is sucked into the sampling pipe 51 in the direction of arrow B, and is discharged through the filter 52. Here, the temperature in front of the filter 52 is changed by adjusting the variable DC power supply 55.

Figure 3 shows the temperature in front of the filter 52 and the temperature in front of the filter 5.
2 shows the relationship with the estimated weight of the collected material above. In the figure,
The shaded area shows the filter 52 without heating after Soxhlet extraction with dichloromethane.
In other words, the estimated weight is shown when only the dry suit is collected on the filter 52. Other items not shaded indicate estimated weights without Soxhlet extraction. From this figure, the estimated weight is the highest when not heated by the coil heater 54, and as the temperature increases, the estimated weight decreases, and becomes almost constant at 200°C or higher, which is the same as when Soxhlet extraction is performed. In other words, when the temperature in front of the filter 52 reaches 200°C or more, only the dry suit is collected on the filter 52, and the SOF passes through the filter 52, and the fine particles in the exhaust gas are collected. is separated into 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. A cooling pipe 45 is provided.

Next, the dry suit and
The relationship between the estimated weight of SOF and the differential pressure before and after the filter will be explained. Generally, it can be easily estimated that the ventilation resistance of the filter will increase as the amount of particles deposited on the filter increases, but the present invention will not work unless there is a quantitative relationship between the two. Also, when fine particles of the same weight are estimated,
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. Figures 4 and 5 show the experimentally determined dry suit and
Collection amount of SOF and pressure loss ΔP in the filter
It is a graph showing the relationship between. In the diagram, A, A', and B
B', C, and C' show the relationship between the amount of collected particulates and the pressure drop ΔP under engine operating conditions of 1000 rpm low load, 2000 rpm medium load, and 3000 rpm high load, respectively.
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 ΔP of the collection filter has a very good proportional relationship with the amount of collection of the dry suit and SOF, and it is understood that it is not affected much by the engine operating conditions. .

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.

Using the pressure loss characteristics of the filter described above, the dry suit and the
To know the SOF emission status, that is, the ever-changing dry suit and SOF emission amount per unit time, you can do the following. Calculate the weight of dry suit or SOF particles emitted per unit time.
If W′, W′ is expressed by the following equation (2).

W' = m x (Q + q) ... (2) where W': Amount of particulate emissions per unit time (mg/sec, etc.) m: Weight of particulates in a unit volume of sampling gas (mg/m ² seconds, etc.) Q ; Diluted mixed gas blower flow rate (m ³ /sec, etc.) q; Sampling gas flow rate (m ³ /sec, etc.) Among the amounts included in the above formula (2), the particle weight m in the unit volume of sampling gas during sampling could not be determined by conventional methods, but can be determined as follows by considering the pressure loss characteristics of the filters 14 and 34 described above. filter 14,
Since the pressure loss of 34 is proportional to the amount of particles collected and proportional to the flow rate, the increase in pressure loss d(ΔP) of the filter during the minute time dt is as follows: d(ΔP) = K・m・q・dt・q...(3) ΔP: Pressure loss (Kg/ ^m2, etc.) K: Constant determined by filter diameter and other factors m・q・dt: Weight of fine particles collected by the filter during dt (mg, etc.) It will be done. From equation (3), m can be found using equation (4) below.

m = 1/K・q ²・d(ΔP)/dt...(4) K: Constant determined by filter diameter, etc. d(ΔP)/dt: Differential value of filter pressure loss Unit volume of sampling gas using equation (4) By determining the weight m of the particles in the vehicle, the amount of particles emitted moment by moment during mode driving can be determined using equation (2) described above. Note that the blower flow rate Q of the diluted mixed gas and the sampling gas flow rate q included in equation (2) take approximately constant values during the test, so they can be treated as constants.

To summarize the above, by determining the time differential value of the pressure loss of the filters 14 and 34, which has the characteristics of being proportional to the amount of collected particles and proportional to the sampling gas flow rate, the dry suit in the unit volume of the sampling gas is You can know the weight of the dry suit and SOF, and ultimately the amount of emissions of the dry suit and SOF while driving in the mode.

Next, the operation of the above embodiment will be explained.

First, at the start of mode driving, valves 12 and 3
2 is opened, the diluted mixed gas is drawn into the first and second sampling pipes 10, 30, and heated to a constant temperature of 200° C. or higher by the coil heaters 13, 22, 33, 42. The heated gas is
It passes through a filter 14 and an auxiliary filter 44, which collect the dry suit. On the other hand, SOF is filter 1
4, 44, but the SOF that has passed through the first filter 14 is collected by a filter (not shown) in the first sampling pump 11, and then passed through the auxiliary filter 4.
The SOF that has passed through the cooling pipe 45 is collected by the second filter 34.

The differential pressure across the first and second filters 14, 34 is determined by the first and second differential pressure converters 18,
38, and the signals thereof are input to first and second arithmetic units 19 and 39, respectively. These computing units 19, 39 further include temperature detectors 15,
35 and a signal indicating the sampling flow rate from the sampling pumps 11 and 31 are input. The reason why the temperatures in front of the filters 14 and 34 are input into the calculators 19 and 39, respectively, is because 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 due to The relationship between this temperature and the differential pressure increase based on temperature is ΔP = aT + b under the condition of constant mass flow rate, and this ΔP is subtracted from the differential pressure determined by the differential pressure converters 18 and 38 to correct the temperature. Do this. However, T is the absolute temperature, and a and b are constants determined by the sampling flow rate and the type of filter.

The first and second computing units 19 and 39 receive the above-mentioned signals and calculate the dry suit and
By determining and reading the weight of the SOF, it is possible to know in real time the amount of dry suit and SOF emissions while the vehicle is running.

Now, the coil heaters 13 and 33 heat the sampling gas to 60 to 80% of the final heating temperature, respectively, and the sampling gas is heated to the coil heaters 22 and 42.
are respectively heated to the final heating temperature. As mentioned above, the coil heaters 13 and 33 are always supplied with constant power and generate a certain amount of heat, but the coil heaters 22 and 42 are connected to the temperature detected by the temperature detectors 15 and 35 by the PID temperature controllers 21 and 42. Based on this, the amount of heat generated is adjusted by controlling the feedback. By the way, the coil heaters 22, 42, the temperature detector 15,
43. It is also possible to heat the sampling gas to a constant temperature using the PID temperature controllers 21, 41.
However, when running in mode, sampling pipe 1
The temperature within 0 and 30 fluctuates by about ±5 degrees Celsius, and the fluctuations occur rapidly, so the PID temperature controllers 21 and 41 cannot adequately control the temperature, and even if they could control it, the differential of the temperature change would be difficult to control. In this embodiment, the coil heaters 13 and 33, which generate heat with constant power, are replaced with the PID temperature controller 2 because the value is very large, which increases the error in measuring the estimated amount of particles.
Coil heaters 22, 4 controlled by 1, 41
It is installed on the upstream side of 2.

The reason why the sampling gas flows out through the coil heaters 13 and 33 that generate heat with constant power to reduce temperature fluctuations is as follows.

If the heating temperature of the coil heater is θw, the coil heater inlet temperature of the inflowing gas is θgi, the coil heater outlet temperature of the inflowing gas is θgo, the heat transfer coefficient from the coil heater to the gas is α, and the heat capacity of the gas is C, θgo is as follows. It can be written like an expression.

θgo = θgi (1-α/C) + α/C・θw ...(5) From equation (5), calculate the change Δθgo in the coil heater outlet temperature when the coil heater inlet temperature of the inflow gas changes by Δθgi. Then, Δθgo = Δθgi・(1−α/C) ...(6) On the other hand, the condition that the coil heater outlet temperature θgo of the inflow gas does not exceed the coil heater temperature,
In other words, from the condition θgo<θw, O<1−α/C<1, so |Δθgo|<|
Δθgi|, and this equation shows that temperature fluctuations are reduced when the temperature passes through a coil heater heated with constant power. For example, θw=250℃, θgi=50℃, θgo
= 150°C, 1-α/C = 0.5, which means that the temperature fluctuation is halved. It can be seen that the value of (1-α/C) decreases as the coil heater outlet temperature of the inflowing gas increases, that is, temperature fluctuations can be suppressed by increasing the outlet temperature. Since the inlet temperature of the incoming gas to the coil heaters 13, 33 fluctuates significantly, input is made to the coil heaters 13, 33 so that the gas is heated to about 60 to 80% of the final heating temperature in the coil heaters 13, 33. All you have to do is adjust the power.

The first filter 14 is placed at the auxiliary filter 44.
If pressure detectors 16 and 17 are installed, a single sampling pipe can be used to
It is possible to measure SOF. However, at the auxiliary filter 44, there is a small first filter 1 with high differential pressure sensitivity depending on the estimated volume of the dry suit.
4, the pressure in the cooling pipe 45 is greatly reduced, so the flow velocity increases and the second filter 34
This will increase the differential pressure before and after. This tendency for the differential pressure to increase varies by about 20 to 30% from filter to filter, and cannot be sufficiently corrected by the calculators 19 and 20. Therefore, as in the above embodiment, two sampling pipes were provided to measure the dry suit and SOF separately. Note that when the filter diameter is increased by x times, the differential pressure sensitivity per estimated amount decreases to 1/x ⁴ .

In the above embodiment, the sampling gas was heated using the coil heaters 13 and 33, but instead of this,
Heating may be performed by wrapping a ribbon heater around the outer periphery of the sampling pipe, or heating may be performed using a burner or the like.

Further, when heating the sampling gas with a coil heater, a heat insulating material or the like may be provided outside the pipe.

Furthermore, as shown in FIG. 6, the pipe on the upstream side of the auxiliary filter 44 may be formed to have substantially the same outer diameter as the filter 44, and the coil heater 42 having a large diameter may be provided in this pipe.

Effects of the Invention As described above, according to the present invention, it is possible to measure the dry suit and SOF in exhaust gas in real time, and the measurement can always be performed accurately.

[Brief explanation of drawings]

Fig. 1 shows an embodiment of the present invention, and Fig. 2 is a partial cross-sectional system diagram, and Fig. 2 is a sectional view showing an experimental apparatus for determining the relationship between the collected matter on the filter and the temperature in front of the filter. , Figure 3 is a graph showing the relationship between the collected matter on the filter and the temperature in front of the filter, Figure 4 is a graph showing the relationship between the amount of dry suit collection and filter pressure loss, and Figure 5 is the graph showing the amount of SOF collected. FIG. 6 is a sectional view showing another embodiment of the pipe and coil heater on the upstream side of the auxiliary filter. 5... Dilution tunnel, 10... First sampling pipe, 11... First sampling pump, 1
3... Coil heater (first heating means), 14...
First filter, 18... First differential pressure converter, 22...
...Coil heater (second heating means), 30...Second
sampling pipe, 31... second sampling pump, 33... coil heater (third heating means),
34... Second filter, 38... Second differential pressure converter, 42... Coil heater (fourth heating means), 4
4...Auxiliary filter.

Claims (1)

[Claims] 1 After diluting and mixing the exhaust gas of the internal engine with a large amount of clean air in a dilution tunnel, the diluted mixed gas is guided to first and second detection means, and the first detection means detects the amount of dry suit in the exhaust gas. The second detection means detects soluble organic matter in exhaust gas, and the first detection means includes a first detection means for extracting a part of the diluted mixed gas from the dilution tunnel. a sampling pipe, a first sampling pump for flowing diluted mixed gas into the first sampling pipe, a first filter provided in the middle of the first sampling pipe to collect dry suit, and a first filter for collecting dry suit from the first filter. A first heating means is provided upstream of the first sampling pipe and has a constant calorific value, and a second heating means is provided downstream of the first heating means and heats the diluted mixed gas to a final heating temperature. means, a first differential pressure converter for detecting the pressure difference before and after the first filter, and a first calculation device for calculating the amount of dry suit in the exhaust gas based on the time differential value of the signal of the pressure difference. The second detection means includes a second sampling pipe for taking out a part of the diluted mixed gas from the diluted tunnel, a second sampling pump for flowing the diluted mixed gas into the second sampling pipe, and a relatively large auxiliary filter provided in the middle of the second sampling pipe to collect the dry suit; and a third heating means provided upstream of the second sampling pipe from the auxiliary filter and having a constant calorific value. and a fourth heating means provided downstream of the third heating means to heat the diluted mixed gas to a final heating temperature; and a second filter provided downstream of the auxiliary filter to collect soluble organic matter. , a second differential pressure converter that detects the pressure difference before and after the second filter, and a second calculation device that calculates the amount of soluble organic matter in the exhaust gas based on the time differential value of the signal of the pressure difference. A vehicle particulate emission measurement device characterized by the following.