Exhaust gas sampling apparatus and exhaust gas analysis system

Abstract

In order to provide an exhaust gas sampling apparatus that makes it possible to simplify the entire system using a simple structure flow rate control mechanism having a small variable flow rate range as well as making the accuracy of an exhaust gas dilution ratio higher than before, the exhaust gas sampling apparatus is configured as an exhaust gas sampling apparatus that makes a multistage dilution. In addition, the exhaust gas sampling apparatus is configured to, given that a dilution ratio determined by an n-th diluter in a dilution flow path at an n-th stage as a final stage is R, make dilution ratios determined by diluters in dilution flow paths at the respective stages other than the n-th stage as the final stage substantially equal to (R+1).

Claims

1. An exhaust gas sampling apparatus comprising: a plurality of sequential dilution flow paths each provided with a sampling pipe adapted to receive exhaust gas or diluted exhaust gas resulting from dilution in an immediately preceding one of the dilution flow paths, a diluter adapted to dilute with dilution air the exhaust gas or the diluted exhaust gas from the sampling pipe, a dilution air flow rate control mechanism adapted to control a flow rate of the dilution air flowing into the diluter, and a diluted exhaust gas flow rate control mechanism adapted to control a flow rate of diluted exhaust gas flowing out of the diluter; and the exhaust gas sampling apparatus being configured such that, in the dilution, flow rates of the exhaust gas and the diluted exhaust gas are controlled in conjunction with the flow rate of the dilution air flowing into the diluter of a final one of the dilution flow path.

2. The exhaust gas sampling apparatus according to claim 1, wherein the exhaust gas sampling apparatus is further configured such that, in the dilution flow paths, the flow rates of the exhaust gas and the diluted exhaust gas are made substantially same.

3. The exhaust gas sampling apparatus according to claim 1, wherein the exhaust gas sampling apparatus is further configured such that, responsive to a dilution ratio determined by the diluter in the final one of the dilution flow paths being R, dilution ratios determined by the diluters in other of the dilution flow paths are made substantially equal to (R+1).

4. The exhaust gas sampling apparatus according to claim 1, where the exhaust gas sampling apparatus is further configured such that the flow rates of the dilution air flowing into the diluters in the dilution flow paths other than the final one of the dilution flow path, and the flow rates of the diluted exhaust gas flowing out of the diluters in all the dilution flow paths are made substantially same.

5. The exhaust gas sampling apparatus according to claim 1, wherein the dilution air flow rate control mechanisms in the dilution flow paths other than the final one of the dilution flow paths are configured such that the flow rates of the dilution air flowing into the diluters in the dilution flow paths other than the final one of the dilution flow paths are made substantially same.

6. The exhaust gas sampling apparatus according to claim 1, wherein the diluted exhaust gas flow rate control mechanisms in the dilution flow paths other than the final one of the dilution flow paths are configured such that the flow rates of the diluted exhaust gas flowing out of the diluters in the dilution flow paths other than the final one of the dilution flow paths are made substantially same.

7. The exhaust gas sampling apparatus according to claim 1, wherein the final one of the dilution flow path is further provided with a filter through which the diluted exhaust gas after the dilution by the diluter of the final one of the dilution flow paths passes.

8. The exhaust gas sampling apparatus according to claim 1, wherein the dilution air flow rate control mechanisms and the diluted exhaust gas flow rate control mechanisms in the dilution flow paths other than the final one of the dilution flow paths are configured to be critical flow orifices or critical flow venturis, respectively.

9. The exhaust gas sampling apparatus according to claim 1, wherein only the dilution air flow rate control mechanism in the final one of the dilution flow paths is configured to change the flow rate of the dilution air flowing into the diluter of the final one of the dilution flow paths, and the flow rates to be controlled by the dilution air flow rate control mechanisms in other than the final one of the dilution flow paths and by the diluted exhaust gas flow rate control mechanisms in all of the dilution flow paths are fixed to one flow rate.

10. An exhaust gas analysis system comprising: the exhaust gas sampling apparatus according to claim 1; and an analyzer adapted to introduce the diluted exhaust gas resulting from the dilution with the dilution air controlled by the dilution air flow rate control mechanism in the final one of the dilution flow paths and to analyze the diluted exhaust gas.

11. An exhaust gas dilution method using an exhaust gas sampling apparatus comprising a plurality of sequential dilution flow paths each provided with a sampling pipe adapted to receive exhaust gas or diluted exhaust gas resulting from dilution in an immediately preceding one of the dilution flow paths, a diluter adapted to dilute with dilution air the exhaust gas or the diluted exhaust gas from the sampling pipe, a dilution air flow rate control mechanism adapted to control a flow rate of the dilution air flowing into the diluter, and a diluted exhaust gas flow rate control mechanism adapted to control a flow rate of diluted exhaust gas flowing out of the diluter, the exhaust gas dilution method comprising: in the dilution flow paths, controlling flow rates of the exhaust gas and the diluted exhaust gas by changing the flow rate of the dilution air flowing into the diluter through the dilution air flow rate control mechanism of a final one of the dilution flow paths.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram illustrating an exhaust gas sampling apparatus and an exhaust gas analysis system according to one embodiment of the present invention;

(2) FIG. 2 is a schematic diagram illustrating the details of the exhaust gas sampling apparatus according to the same embodiment; and

(3) FIG. 3 is a functional block diagram illustrating the configuration of a control part of an exhaust gas sampling apparatus according to another embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

(4) An exhaust gas analysis system 200 and an exhaust gas sampling apparatus 100 according to one embodiment of the present invention will be described with reference to FIGS. 1 and 2.

(5) The exhaust gas sampling apparatus 100 according to the present embodiment is one that as illustrated in FIG. 1, constitutes part of the exhaust gas analysis system 200 adapted to measure the amount of particulate matter (hereinafter also referred to as PM) having a predetermined particle size contained in exhaust gas. More specifically, from the side surface of an attachment pipe attached to a tail pipe of a vehicle V making a test run on a chassis dynamometer 101, a sampling pipe S of the exhaust gas sampling apparatus 100 is inserted into the attachment pipe. In addition, part of the raw exhaust gas discharged from the vehicle V is collected through the sampling pipe S, and diluted to a predetermined concentration by the exhaust gas sampling apparatus 100. The diluted exhaust gas resulting from the dilution by the exhaust gas sampling apparatus 100 is introduced into an analyzer 102 to analyze the exhaust gas. The analyzer 102 in the present embodiment is one adapted to measure the amount of particulate matter, but may be configured to measure the amounts or concentrations of other components such as NO.sub.x, CO, CO.sub.2, and THC.

(6) As illustrated in FIG. 2, the exhaust gas sampling apparatus 100 is configured to dilute the exhaust gas in a multistage manner to a concentration appropriate for measuring the amount of the PM contained in the exhaust gas. That is, the exhaust gas sampling apparatus 100 has an n-stage dilution flow path DL (n is a natural number equal to or more than 2), and is configured to dilute the exhaust gas in stages by repeating dilution of the exhaust gas or diluted exhaust gas and flow separation of the diluted exhaust gas through the respective dilution flow paths DL.

(7) The respective dilution flow paths DL have substantially the same configuration. That is, a dilution flow path DL at a k-th stage (k is a natural number from 1 to n) is provided with: a k-th sampling pipe S adapted to get the exhaust gas or diluted exhaust gas; a k-th diluter T adapted to dilute with dilution air the exhaust gas or the diluted exhaust gas got through the k-th sampling pipe S; a k-th dilution air flow rate control mechanism D adapted to control the flow rate of the dilution air flowing into the k-th diluter T; and a k-th diluted exhaust gas flow rate control mechanism E adapted to control the flow rate of the diluted exhaust gas flowing out of the k-th diluter T. Note that in the case where components at the respective stages are easier to understand when described discriminatingly in the following description, the components at the k-th stage are represented by giving the number denoting the stage to the symbols, like DL(k), D(k), S(k), and T(k).

(8) The first sampling pipe S(1) in the dilution flow path DL at the first stage is intended to get the exhaust gas, and a k-th sampling pipe S(k) in a dilution flow path DL(k) at a k-th stage other than the first stage is configured to get diluted exhaust gas resulting from dilution in a dilution flow path DL(k1) at a (k1)-th stage.

(9) The diluter T is a tubular-shaped dilution tunnel, and from an upstream end thereof, the dilution air having passed through the dilution air flow rate control mechanism D flows in, whereas a downstream end thereof is connected to the diluted exhaust gas flow rate control mechanism E. On the upstream side inside the diluter T, a downstream end of the sampling pipe S is opened to allow the exhaust gas or the diluted exhaust gas got from the dilution flow path DL at the previous stage to flow in. In addition, in a dilution flow path DL at a stage other than the n-th stage as the final stage, on the downstream side inside a diluter T, the upstream end of a sampling pipe S constituting a dilution flow path DL at the next stage is opened to allow part of diluted exhaust gas to separately flow to the next dilution flow path DL. The rest of the diluted exhaust gas, which does not separately flow to the next dilution flow path DL, passes through a diluted exhaust gas flow rate control mechanism E and is discharged to the outside of the diluter T.

(10) The dilution air flow rate control mechanisms D of the dilution flow paths DL at the stages other than the n-th stage are critical flow orifices or critical flow venturis configured to flow the dilution air at substantially the same flow rate. On the other hand, the dilution air flow rate control mechanism D(n) of the dilution flow path DL(n) at the n-th stage is configured to be able to appropriately change the flow rate of the dilution air.

(11) Also, in the present embodiment, the diluted exhaust gas flow rate control mechanisms E of all the dilution flow paths DL are critical flow orifices or critical flow venturis configured to flow corresponding exhaust gases at substantially the same flow rate. In addition, each of the diluted exhaust gas flow rate control mechanisms E is connected downstream thereof to an unillustrated suction source such as a pump.

(12) Further, in the dilution flow path DL(n) at the n-th stage as the final stage, a filter F through which the diluted exhaust gas passes is provided between the downstream end of the diluter T(n) and the diluted exhaust gas flow rate control mechanism E(n). The filter F collects PM contained in the diluted exhaust gas, and the content of the PM is measured by measuring the blackness of the filter F.

(13) Next, the flow rate of gas flowing through each dilution flow path DL will be described in the following order: the flow rate of the gas flowing through the dilution flow path DL at the n-th stage as the final stage, and the flow rate of gas flowing through each of the dilution flow paths DL at the stages other than the n-th stage.

(14) Since in the dilution flow path DL(n) at the n-th stage, the diluted exhaust gas is entirely discharged outside from the n-th diluter T(n) through the n-th diluted exhaust gas flow rate control mechanism E(n) without flow separation, the difference in flow rate between an outflow diluted exhaust gas flow rate Q.sub.E(n) controlled by the n-th diluted exhaust gas flow rate control mechanism E(n) and an inflow dilution air flow rate Q.sub.D(n) controlled by the n-th dilution air flow rate control mechanism D(n) is equal to the flow rate Q.sub.S(n) of diluted exhaust gas got from the dilution flow path DL(n1) at the (n1)-th stage through the n-th sampling pipe S(n).

(15) That is, the relationship among them can be represented as
Q.sub.S(n)=Q.sub.E(n)Q.sub.D(n)(1)

(16) Also, a dilution ratio R in the dilution flow path DL at the n-th stage can be represented from the definition thereof as
R=(Q.sub.S(n)+Q.sub.D(n))/Q.sub.S(n)=Q.sub.E(n)/Q.sub.S(n).(2)

(17) The flow rate QE(n) of the diluted exhaust gas passing through the n-th diluted exhaust gas flow rate control mechanism E(n) is set so as to meet regulations such as emissions measurement regulations provided in US. In the present embodiment, the flow rate Q.sub.E is set to a flow rate determined as a flow rate at which the diluted exhaust gas should be passed through the filter F in order to measure the PM.

(18) Next, the flow rate of gas flowing through the dilution flow path DL(k) at the k-th stage other than the n-th stage will be described.

(19) Given that the flow rate of the dilution air controlled by the k-th dilution air flow rate control mechanism D is Q.sub.D(k), the flow rate of the exhaust gas or the diluted exhaust gas got from the dilution flow path DL(k1) at the (k1)-th stage through the k-th sampling pipe S(k) is Q.sub.S(k), the flow rate of the diluted exhaust gas separately flowed through the (k+1)-th sampling pipe S(k+1) is Q.sub.S(k+1), and the flow rate of the diluted exhaust gas discharged outside through the k-th diluted exhaust gas flow rate control mechanism E(k) is QE(k), since the flow rates of the diluted exhaust gases flowing into and flowing out of the k-th diluter T(k) are balanced, the relationship among the flow rates can be represented as follows.
Q.sub.D(k)+Q.sub.S(k)=Q.sub.S(k+1)+Q.sub.E(k)(3)

(20) Also, given that a dilution ratio in the dilution flow path DL(k) at the k-th stage is X(k), the dilution ratio X(k) can be represented from the definition of a dilution ratio as follows.
X(k)=(Q.sub.S(k)+Q.sub.D(k))/Q.sub.S(k)(4)

(21) Note that in the present embodiment, each of the inflow dilution air flow rate Q.sub.D(k) controlled by the k-th dilution air flow rate control mechanism D(k) at the k-th stage other than the n-th stage and the outflow diluted exhaust gas flow rate Q.sub.E(k) controlled by the k-th diluted exhaust gas flow rate control mechanism E(k) is set to be equal to the flow rate Q.sub.E(n) of the diluted exhaust gas flowing out of the n-th diluted exhaust gas flow rate control mechanism E(n).

(22) In short, in the dilution flow path DL(k) at the k-th stage other than the n-th stage, each of the dilution air flow rate Q.sub.D(k) and the flow rate Q.sub.E(k) at which the diluted exhaust gas passes through the k-th diluted exhaust gas flow rate control mechanism E(k) and flows outside is equal to Q.sub.E(n), and therefore Expression (3) can be modified as follows.
Q.sub.S(k)=Q.sub.S(k+1)(5)

(23) That is, the flow rates of the exhaust gas and the diluted exhaust gases got through all the sampling pipes S are the same, and equal to the flow rate Q.sub.S(n) of the diluted exhaust gas got in the dilution flow path DL(n) at the n-th stage. Note that the flow rate Q.sub.S(n) of the diluted exhaust gas got at the n-th stage can be adjusted by changing the inflow dilution air flow rate Q.sub.D(n) determined by the n-th dilution air flow rate control mechanism D(n). In addition, as can be seen from Expression (5), conjunctive control can be performed such that only by changing the flow rate Q.sub.D(n) of the dilution air flowing into the n-th diluter T(n), the flow rate Q.sub.S(k) of the exhaust gas or diluted exhaust gas got at each stage is also made equal to the flow rate Q.sub.S(n) of the diluted exhaust gas got at the n-th stage. In other words, the present embodiment is configured to set the dilution air flow rates Q.sub.D(k) at the respective stages except for the dilution air flow rate Q.sub.D(n) at the n-th stage and the outflow diluted exhaust gas flow rates Q.sub.E(k) at all the stage to the same flow rate, and thereby in the dilution flow paths DL(k) at the respective stages, control the flow rates Q.sub.S(k) of the exhaust gas and the diluted exhaust gases got through corresponding sampling pipes S(k) in conjunction with the flow rate Q.sub.D(n) of the dilution air flowing into the n-th diluter T(n) through the n-th dilution air flow rate control mechanism D(n).

(24) As described above, since the dilution air flow rate Q.sub.D(k) at the k-th stage is controlled to be equal to the diluted exhaust gas flow rate Q.sub.E(n) at the n-th stage, the dilution ratio X in the dilution flow path DL at the k-th stage other than the n-th stage given by the flow rate expression (4) can be rewritten as follows.
X(k)=(Q.sub.S(n)+Q.sub.E(n)/Q.sub.S(n)(6)

(25) Further, from Expressions (2) and (6), the following expression can be derived.
X(k)=R+1(7)

(26) As described, in the present embodiment, by making the flow rates controlled by all the flow rate control mechanisms except for the n-th dilution air flow rate control mechanism D(n) uniformly equal to Q.sub.E(n), the dilution ratios in the dilution flow paths DL at the stages other than the n-th stage are made uniformly equal to (R+1).

(27) Also, as can be seen from Expressions (1) and (2), when making the flow rate Q.sub.D(n) of the inflow dilution air from the n-th dilution air flow rate control mechanism D(n) slightly smaller than Q.sub.E(n), the dilution ratio in the dilution flow path DL(n) at the n-th stage has a sufficient large value, and therefore the dilution ratio R in the dilution flow path DL at the n-th stage, and the dilution ratios (R+1) in the dilution flow paths DL at the respective stages other than the n-th stage can be made uniformly equal to substantially the same value.

(28) As described, the exhaust gas sampling apparatus 100 according to the present embodiment is adapted to make the flow rates controlled by the flow rate control mechanisms other than the n-th dilution air flow rate control mechanism D(n) uniformly equal to the flow rate Q.sub.E(n) of the diluted exhaust gas to be passed through the filter F. As a result, the exhaust gas sampling apparatus 100 can make the dilution ratios in the respective dilution flow paths DL uniformly equal to substantially the same value, and dilute the exhaust gas in stages.

(29) In addition, since the exhaust gas or diluted exhaust gas is diluted in each dilution flow path DL at the small dilution ratio step by step, even in the case where an error occurs in the flow rate of the fluid flowing through the dilution flow path DL, the error is unlikely to affect the dilution ratio (R+1) or R in the dilution flow path DL.

(30) Accordingly, even in the case of desiring to increase a dilution ratio Y as the whole of the exhaust gas sampling apparatus 100 to a large value, the dilution can be accurately made.

(31) Also, in the case of desiring to change the dilution ratio Y as the whole of the exhaust gas sampling apparatus 100 to another value, only by changing the dilution air flow rate Q.sub.D(n) controlled by the n-th dilution air flow rate control mechanism D(n), the dilution ratios in the respective dilution flow paths DL(k) can be automatically made uniform. As a result, in the case of desiring to change a dilution ratio, in the past, a flow rate set in a flow rate control mechanism provided in each dilution flow path DL has been changed, whereas the exhaust gas sampling apparatus 100 according to the present embodiment can make the dilution ratios in the respective flow paths DL uniform, and accurately make the dilution at a high dilution ratio as a whole only by changing the flow rate set in the one flow rate control mechanism.

(32) Further, in the exhaust gas sampling apparatus 100 according to the present embodiment, only the n-th dilution air flow rate control mechanism D(n) is a flow rate control mechanism having a large variable flow rate range, and for the other flow rate control mechanisms, mechanisms of the same type having a fixed flow rate can be used. Accordingly, the many flow rate control mechanisms used in the exhaust gas sampling apparatus 100 can be configured as the mechanisms of the same type to simplify the system while keeping the accuracy of the dilution ratio.

(33) Other embodiments will be described.

(34) In the above-described embodiment, the exhaust gas sampling apparatus 100 including the n-stage dilution flow path DL is described; however, the present invention may be configured as an exhaust gas sampling apparatus 100 including a two- or more-stage dilution flow path DL. Also, the above-described embodiment is configured to measure the exhaust gas only at the n-th stage as the final stage; however, the present invention may be configured to provide an exhaust gas measuring device in a dilution flow path DL at a middle stage to measure the exhaust gas. Each of the flow rate control mechanisms is not limited to the critical flow orifice or the critical flow venturi, but may use a mechanism configured to combine a mass flow controller or a flow rate control valve, and a controller. Further, the present invention may be configured such that in a dilution flow path DL at a stage other than the n-th stage, a dilution air flow rate Q.sub.D(k) determined by a corresponding dilution air flow rate control mechanism D and a diluted exhaust gas flow rate Q.sub.E(k) determined by a corresponding diluted exhaust gas flow rate control mechanism E are set to different values, and the dilution ratios in the dilution flow paths at the stages other than the n-th stage are made uniformly equal to (R+1) where R is the dilution ratio in the dilution flow path DL(n) at the n-th stage.

(35) In the above-described embodiment, the case where the dilution ratios in the dilution flow paths DL at the respective stages other than the n-th stage are made uniformly equal to (R+1) is described; however, the dilution ratios in the respective dilution flow paths DL may be made uniformly equal to substantially the same value. For example, even in the case where the dilution ratios are made uniform within the range of plus/minus 20% with reference to the dilution ratio (R+1), or the dilution ratios are high dilution ratios, the exhaust gas can be accurately diluted. In addition, preferably, it is only necessary to make the dilution ratios uniform within the range of plus/minus 10% or 5% with reference to the dilution ratio (R+1).

(36) Further, the present invention may be configured to make the dilution air flow rates controlled by the respective dilution air flow rate control mechanisms D at the stages other than the n-th stage uniform within the range of plus/minus 20% with reference to a reference flow rate Q.sub.DR. Preferably, it is only necessary to make the flow rates controlled by the respective dilution air flow rate control mechanisms D at the stages other than the n-th stage uniform within the range of plus/minus 10% or 5% with reference to the reference flow rate Q.sub.DR.

(37) Still further, the dilution air flow rates Q.sub.D(k) at the stages other than the n-th stage and the flow rates Q.sub.E(k) of the diluted exhaust gas discharged through corresponding diluted exhaust gas flow rate control mechanisms E are not required to have precisely the same value.

(38) The diluted exhaust gas flow rates controlled by the respective diluted exhaust gas flow rate control mechanisms E may also be made uniform within a predetermined range with reference to a reference flow rate Q.sub.ER. For example, is it only necessary to make the diluted exhaust gas flow rates uniform within the range of plus/minus 20% with reference to the reference flow rate Q.sub.ER, or preferably, the present invention may be configured to make the diluted exhaust gas flow rates uniform within the range of plus/minus 10% or 5% with reference to the reference flow rate Q.sub.ER.

(39) In addition, as illustrated in FIG. 3, the exhaust gas sampling apparatus 100 may further include a control part C adapted to receive the dilution ratio Y to be achieved as a whole, and change a flow rate set in the n-th dilution air flow rate control mechanism D(n) in order to achieve the dilution ratio Y.

(40) The control part C is constituted by a computer including a CPU, memory, A/D and D/A converters, input/output means, and the like, and functions as at least a total dilution ratio reception part C1, a setting flow rate calculation part C2, and a flow rate setting part C3.

(41) The total dilution ratio reception part C1 is one that receives the dilution ratio Y to be achieved as the whole of the exhaust gas sampling apparatus 100 through some means such as user's input, and outputs a value of the dilution ratio Y to the setting flow rate calculation part C2.

(42) The setting flow rate calculation part C2 is one that on the basis of the received total dilution ratio Y, calculates the setting flow rate to be set in the n-th dilution air flow rate control mechanism D(n). As described in the above embodiment, given that the dilution ratio in the dilution flow path DL at the n-th stage is R, the dilution ratios in the dilution flow paths DL at the stages other than the n-th stage are (R+1), and therefore the exhaust gas dilution ratio Y as the whole of the exhaust gas sampling apparatus 100 is Y=R(R+1).sup.n1, or if R is sufficiently large, can be YR.sup.n as an approximate value. The setting flow rate calculation part C2 calculates the dilution ratio R at the n-th stage on the basis of any of these expressions. Further, since the flow rate Q.sub.E(n) of the diluted exhaust gas to be flowed to the filter F is predetermined in accordance with test regulations, the setting flow rate calculation part C2 calculates the required dilution air flow rate Q.sub.D(n) at the n-th stage from the calculated dilution ratio R and the flow rate Q.sub.E(n), and determines a value of the calculated dilution air flow rate Q.sub.D(n) as the setting flow rate.

(43) The flow rate setting part C3 sets Q.sub.D(n), which has been calculated in the setting flow rate calculation part C2, in the n-th dilution air flow rate control mechanism D as a target value. Note that the flow rate setting part C3 is configured to change the setting flow rate to be set only in the n-th dilution air flow rate control mechanism among the many flow rate control mechanisms.

(44) Such a configuration as described above makes it possible to activate the exhaust gas sampling apparatus 100 so as to automatically and most accuracy make the dilution on the basis of the total dilution ratio Y inputted by a user.

(45) Note that the present invention is not limited to any of the above-described embodiments, but may include various modifications and combinations of the embodiments.

REFERENCE SIGNS LIST

(46) 200: Exhaust gas analysis system 100: Exhaust gas sampling apparatus D(k): Dilution air flow rate control mechanism S(k): Sampling pipe T(k): Diluter (dilution tunnel) E(k): Diluted exhaust gas flow rate control mechanism C: Control part C1: Total dilution ratio reception part C2: Setting flow rate calculation part C3: Flow rate setting part