WO2008061872A1

WO2008061872A1 - Test bench for exhaust gas analysis and method for using the same

Info

Publication number: WO2008061872A1
Application number: PCT/EP2007/061909
Authority: WO
Inventors: Manuel Denayrolles; Corinne Wartelle
Original assignee: Renault S.A.S
Priority date: 2006-11-21
Filing date: 2007-11-06
Publication date: 2008-05-29
Also published as: FR2908886A1

Abstract

The invention relates to a test bench for analysing the exhaust gases of an engine (2), the engine including a filter assembly (5), a first duct (4) for connecting said engine (2) to said filter assembly (5), a second duct (6) for connecting said filter assembly (5) to open air, wherein the test bench comprises at least one analysis line (7) including a sampling cannula (8), a hot line (9) and an analysis bay (10), wherein said test bench further includes a two-position distribution means (11) and a bleeder cannula (12) connected to open air, the distribution means (11) being provided so as to connect the hot line (9) to the sampling cannula (8) in a first position (13), and so as to connect the hot line (9) to the bleeder cannula (12) in the second position (14). The invention also relates to a method for using said test bench, comprising an analysis step in which the distribution means (11) is controlled in its first position (13), exhaust gases are sampled and conveyed to the analysis bay (10), and a bleeding step in which a bleeder gas is injected while the distribution means (11) is controlled in its second position (14).

Description

Exhaust gas test bench and method of use.

The present invention relates to an exhaust gas test bench for an internal combustion engine.

In the field of exhaust gas analysis, it is known to use a bench of the type illustrated in FIG.

Such a test bench 1 is intended to test an engine comprising a filter assembly 5, a first exhaust pipe 4 connecting the exhaust of said engine 2 to an inlet of the filter assembly 5, a second exhaust pipe 6 connecting an outlet of the filter assembly 5 to the open air. The bench comprises at least one analysis line 7 of the exhaust gas. The filter assembly 5 can comprise a particulate filter (FAP) still designated in English "diesel particles filter" (DPF) and / or a catalytic oxidation filter (FOC) still referred to as "diesel oxidation catalyst" (DOC). The first exhaust pipe 4 may comprise a turbine 3. In this case the gas sampling is preferably carried out downstream of said turbine 3. The engine 2, of the internal combustion type, produces in operation exhaust gases that we want to analyze. For this, one or more analysis lines 7 are arranged in such a manner as to take off said gas. An analysis line 7 typically comprises an exhaust gas sampling cannula 8, a hot line 9 and an analysis rack 10. The sampling cannula 8 is connected by a stitching to the zone where it is desired to carry out the sampling, for example at the level of the first pipe 4 upstream of the filter assembly 5, in the embodiment illustrated in FIG. 1. The other end of the sampling cannula 8 is connected to a hot line 9 which transports the gas to the analysis bay 10 where the gas can be analyzed. A hot line 9 is an advantageously flexible tube, coated with a sheath in which electrical resistances are embedded in order to regulate the internal walls of the tube at high temperature. This high temperature, of the order of 18O ⁰ C, avoids during the sampling a cooling of the gas incompatible with the measurement and limits the formation of condensates. The analysis array 10 may be a smoke meter or a gas analyzer.

The use of such a test bench typically comprises two steps. In a first analysis step, exhaust gas is taken by the sampling cannula 8 and transmitted via the hot line 9 to the analysis rack 10. Depending on the type of rack 10, the analysis includes a test analysis. the chemical composition and / or the particle ratio with a gas analyzer or a measurement of the smoke index with a smoke meter.

In a second purge step, a purge gas is injected from the analysis chamber 10, in order to discharge into the exhaust pipe 4 the residues and condensates accumulated in the analysis line 7 during the analysis step. .

The fact of performing the purge by the same line as that used for the sampling during the analysis step entails the following disadvantages: the expansion of the purge gas, injected under pressure, when it reaches the piping of Exhaust 4 causes significant cooling of the active elements: filter assembly 5 and turbine 3. This cooling requires an additional waiting time required for stabilized temperature rise of said active elements before a new analysis step;

the purge thus produced discharges residues and condensates formed in the analysis line 7 by driving them back into the sampling / measurement zone. This causes pollution of the measurement zone without control of its composition;

the purge thus produced discharges said residues and said condensates upstream of the filter assembly 5. This induces a pollution of the filter assembly 5 and particularly of the particle filter.

In order to remedy these various disadvantages, the invention modifies the test bench to redirect the purge flow elsewhere than in the measurement zone.

The test bench according to the invention further comprises a distribution means 11, 16, 17 with two positions and a purge cannula 12. Said purge cannula 12 is connected to the open air at one of its ends. The dispensing means 11, 16, 17 is disposed between the sampling cannula 8, the purge cannula 12 at its other end and the hot line 9 so as to connect:

in a first position 13 the hot line 9 with the sampling cannula 8 and

in a second position 14 the hot line 9 with the purge cannula 12.

According to a first embodiment of the invention, the dispensing means is a three-way distributor 11 and two positions 13, 14. This is illustrated in Figures 2 and 3. The two positions are obtained by moving the dispenser drawer 11 .

According to a second embodiment of the invention, the distribution means comprises two two-way valves 16, 17 jointly controlled.

Thus it is possible to use the test bench according to the following procedure: during the analysis step, the means of 11, 16, 17 being controlled in its first position 13, the exhaust gas is taken from the first pipe 4 by the sampling cannula 8 and transmitted via the distribution means 11, 16, 17 and the hot line 9 to the analysis bay 10, and during the purge step, the dispensing means 11, 16, 17 being controlled in its second position 14, a purge gas is injected at the analysis bay 10 and passes through said analysis chamber 10, the hot line 9, the distribution means 11, 16, 17 and the purge cannula 12.

The purge gas thus ejected in the open air advantageously no longer causes the aforementioned drawbacks.

According to another characteristic of the invention, the purge cannula 12 is able to be connected to the free air via a stitching 15 in the second exhaust pipe 6. Such an arrangement advantageously makes it possible, on the one hand, to reuse the exhaust gas treatment equipment disposed at the exit of the exhaust line. On the other hand, it alternatively enables the purge cannula 12 to be used for taking a sample of gas downstream of the filter assembly 5.

Other characteristics, details and advantages of the invention will emerge more clearly from the detailed description given below as an indication in relation to drawings in which:

FIG. 1 illustrates an exhaust gas analysis test bench according to the prior art,

FIG. 2 illustrates an improved test bench according to the invention, the three-way distributor in a first position,

- Figure 3 illustrates an improved test bench according to the invention, the three-way distributor in a second position

FIG. 4 illustrates an improved test bench according to the invention, according to the embodiment with two valves.

From one figure to another, the same numerical references designate the same elements. With respect to the test bench of the prior art already described with reference to FIG. 1, a test bench according to the invention as illustrated in FIGS. 2, 3 and 4, further comprises a distribution means 11 , 16, 17 with two positions and a purge cannula 12. This purge cannula 12 is connected to the open air. According to the first embodiment, the dispensing means is a three-way distributor 11 disposed between the sampling cannula 8, the purge cannula 12 and the hot line 9 in such a way as to connect:

in a first position 13, illustrated in FIG. 2, the hot line 9 with the sampling cannula 8 and

in a second position 14, illustrated in FIG. 3, the hot line 9 with the purge cannula 12.

According to a second embodiment, illustrated in FIG. 4, the distribution means is made by association of two valves 16, 17 connected by a tee

18. Each of the valves 16, 17 has a passing lane and a closed lane. A first valve 16 is connected to the sampling cannula 8. A second valve 17 is connected to the purge cannula 12. A tee 18 connects the two valves 16, 17 and the hot line 9 connecting to the analysis chamber 10. The two valves are jointly controlled to provide two positions 13, 14. The sampling position 13 is obtained with the first valve 16 passing and the second valve 17 closed. The purge position 14 is obtained with the first valve 16 closed and the second valve 17 passing. FIG. 4 illustrates this embodiment in sampling position 13.

In this second embodiment, in order to limit the fouling of the line 9 and the tee 18 during the phases of operation of the engine different from the sampling phase, the first valve 16 is advantageously normally closed while the second valve 17 is advantageously normally open.

Thus, it is possible to perform an analysis step similar to that of the prior art, when the distribution means 11, 16, 17 is controlled in its first position 13. Exhaust gas can be taken from the first pipe 4 through the sampling cannula 8 and be transmitted via the distributor 11 and the hot line 9 to the analysis bay 10.

A purge step can be performed when the dispensing means 11, 16, 17 is controlled in its second position 14. A purge gas can be injected at the analysis array 10. It passes through said analysis bay 10, the hot line 9, the dispensing means 11, 16, 17 and the bleed cannula 12. In contrast with the bleeding step of the prior art, the purge air flow does not pass back into the cannula 8 to lead in the first pipe 4, but is redirected by the dispensing means 11, 16, 17 to the purge pipe 12 to reach the open air.

Note that the upstream portion of the dispensing means 11, 16, 17, namely the sampling cannula 8, is not purged during the purge step. Also, according to an advantageous embodiment, the length of the sampling cannula 8 is as short as possible. A length thus limited reduces the exhaust gas cooling. This cooling is detrimental to a good analysis in that it modifies the measurement conditions. In addition, this cooling favors the condensation that is to be avoided.

The evacuation of the exhaust gas when it leaves the air requires extraction equipment in order not to pollute the workshop where the test bench is located. These extraction equipment, present at the exit of the test bench

(free end of the second exhaust pipe 6), are reused for the purge flow, according to an advantageous embodiment where the purge cannula 12 is connected to the open air via a stitching 15 in the second pipe of Exhaust 6. This embodiment is illustrated in Figures 2 and 3.

In this embodiment, it is still possible with the test bench according to the invention to carry out another analysis step in which the exhaust gas sampling takes place in the second pipe 6, downstream of the pipe. filter assembly 5. For this the distribution means 11, 16, 17 is controlled in its second position 14, to allow an exhaust gas sampling in the second pipe 6 by means of the purge cannula 12. This gas is then transmitted via the distribution means 11, 16, 17 and the hot line 9 to the analysis rack 10. In this same second position of the distribution means 11, 16, 17, it is possible to purge the line of an analysis comprising the cannula 12, the hot line 9 and the analysis array 10, by sending a purge gas to the analysis bay 10. Advantageously, in order not to send the flow of purge gas to the filter assembly 5, at risk to cool and / or pollute, the stitching 15 is such that the purge cannula 12 is oriented on the opposite side to the filter assembly 5. Thus the purge flow flows to the free end of the second pipe 6.

When the purge cannula 12 is used to perform a gas sampling downstream of the filter assembly 5, it is advantageous for its length to be as short as possible. A length thus limited reduces the cooling of the exhaust gas, detrimental to good analysis and favorable to condensate, as seen above. Similarly, in order to take the filter assembly 5 as close as possible downstream from it, the stitching 15 is advantageously arranged as close as possible to the filter assembly 5.

In order to reduce the drawbacks of the cooling of the exhaust gas in the purge cannula 12, for example when its length can not be sufficiently reduced, the purge cannula 12 advantageously comprises a hot line.

According to a particularly interesting embodiment, in order to fight against the detrimental effects both for analysis and for pollution, of a cooling of the exhaust gas, the distribution means 11, 16, 17 is advantageously heated.

According to an advantageous embodiment, the purge streams use a purge gas consisting of synthetic air ("clean" air obtained by mixing oxygen and nitrogen in proportion of 20 and 80% respectively) or 'nitrogen. In order to improve the efficiency and the productivity of the cleaning of the elements traversed during the purge steps, the purge gas is injected under pressure in a pulsed flow.

Claims

1. Exhaust gas test bench for an internal combustion engine, the engine (2) to be tested producing exhaust gas and comprising

- a filter assembly (5), a first exhaust pipe (4) connecting said motor (2) to said filter assembly (5), - a second exhaust pipe (6) connecting said filter assembly (5) to the free air, and the test bench comprising at least one analysis line (7) comprising:

An exhaust gas sampling pipe (8) adapted to be stitched into said first exhaust pipe (4), extended by

A hot line (9) allowing the transfer of exhaust gas to an analysis chamber (10) of said exhaust gas, characterized in that the test bench further comprises a distribution means (11, 16 , 17) at two positions (13, 14) and a bleed cannula (12) connected to the free air, the dispensing means (11, 16, 17) being arranged between the sampling cannula (8), the cannula purge (12) and the hot line (9) so as to connect:

- In a first position (13) the hot line (9) with the sampling cannula (8) and - in a second position (14) the hot line (9) with the purge cannula (12).

2. Test stand according to claim 1, wherein the dispensing means is a distributor (11) three-way and two positions (13, 14).

3. Test bench according to claim 1, wherein the distribution means comprises two valves (16, 17) to two lanes jointly ordered.

4. Test bench according to any one of claims 1 to 3, wherein the length of the sampling cannula (8) adapted to connect the first exhaust pipe (4) to the distribution means (11, 16, 17 ) is as short as possible.

5. Test bench according to any one of claims 1 to 4, wherein the purge cannula (12) is adapted to be connected to the open air via a stitching (15) in the second exhaust pipe (6). ).

6. Test stand according to claim 5, wherein said stitching (15) is such that the purge cannula (12) is oriented on the opposite side to the filter assembly (5).

7. Test bench according to claim 5 or 6, wherein the length of the purge cannula (12) connecting the second exhaust pipe (6) to the distribution means (11, 16, 17) is the shortest possible and wherein the stitching (15) is disposed closest to the filter assembly (5).

8. Test stand according to any one of claims 5 to 7, wherein the purge cannula (12) comprises a hot line.

9. Test bench according to any one of claims 1 to 8, wherein the dispensing means (11, 16, 17) is heating.

10. A method of using a test bench according to any one of claims 1 to 9, characterized in that it comprises the following steps:

an analysis step where, the dispensing means (11, 16, 17) being controlled in its first position (13), exhaust gas is taken from the first pipe (4) by the sampling cannula (8); ) and transmitted via the distribution means (11, 16, 17) and the hot line (9) to the analysis bay (10), and

a purge step where the dispensing means (11, 16, 17) being controlled in its second position

(14), a purge gas is injected at the bay for analysis (10) and passes through said analysis chamber (10), the hot line (9), the dispensing means (11, 16, 17) and the bleed cannula (12).

11. The method of claim 10 for using a test bench according to any one of claims 5 to 9 further comprising the following step:

an analysis step where, the distribution means

(11, 16, 17) being controlled in its second position

(14), exhaust gas is taken from the second pipe (6) through the bleed cannula (12) and transmitted via the distribution means (11, 16, 17) and the hot line (9) to the bay analysis (10).

12. The method of claim 10 or 11, wherein the purge gas is synthetic air or nitrogen, injected under pressure in a pulsed flow.